@article{
 title = {A generalized shear-lag theory for elastic stress transfer between matrix and fibres having a variable radius},
 type = {article},
 year = {2022},
 pages = {111464},
 volume = {239-240},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0020768322000348},
 month = {3},
 id = {4dcc0590-9688-313a-8264-d4c8edaf440a},
 created = {2022-01-30T04:40:50.073Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-03-23T10:38:35.345Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Topcu2022},
 private_publication = {false},
 abstract = {A generalized shear-lag theory for fibres with variable radius is developed to analyse elastic fibre/matrix stress transfer. The theory accounts for the reinforcement of biological composites, such as soft tissue and bone tissue, as well as for the reinforcement of technical composite materials, such as fibre-reinforced polymers (FRP). The original shear-lag theory proposed by Cox in 1952 is generalized for fibres with variable radius and with symmetric and asymmetric ends. Analytical solutions are derived for the distribution of axial and interfacial shear stress in cylindrical and elliptical fibres, as well as conical and paraboloidal fibres with asymmetric ends. Additionally, the distribution of axial and interfacial shear stress for conical and paraboloidal fibres with symmetric ends are numerically predicted. The results are compared with solutions from axisymmetric finite element models. A parameter study is performed, to investigate the suitability of alternative fibre geometries for use in FRP.},
 bibtype = {article},
 author = {Topçu, Murat and Madabhushi, Gopal S.P. and Staat, Manfred},
 doi = {10.1016/j.ijsolstr.2022.111464},
 journal = {International Journal of Solids and Structures}
}

A generalized shear-lag theory for fibres with variable radius is developed to analyse elastic fibre/matrix stress transfer. The theory accounts for the reinforcement of biological composites, such as soft tissue and bone tissue, as well as for the reinforcement of technical composite materials, such as fibre-reinforced polymers (FRP). The original shear-lag theory proposed by Cox in 1952 is generalized for fibres with variable radius and with symmetric and asymmetric ends. Analytical solutions are derived for the distribution of axial and interfacial shear stress in cylindrical and elliptical fibres, as well as conical and paraboloidal fibres with asymmetric ends. Additionally, the distribution of axial and interfacial shear stress for conical and paraboloidal fibres with symmetric ends are numerically predicted. The results are compared with solutions from axisymmetric finite element models. A parameter study is performed, to investigate the suitability of alternative fibre geometries for use in FRP.

@article{
 title = {Dental strain on maxillary incisors during tracheal intubation with double-lumen tubes and different laryngoscopy techniques - a blinded manikin study},
 type = {article},
 year = {2022},
 websites = {https://www.sciencedirect.com/science/article/abs/pii/S1053-0770(22)00126-4,https://linkinghub.elsevier.com/retrieve/pii/S1053077022001264},
 month = {2},
 id = {ea2198db-c5da-35ea-8b3b-9e70b17a5405},
 created = {2022-02-14T14:51:49.305Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-02-17T20:32:45.498Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Defosse2022},
 private_publication = {false},
 abstract = {Objectives : To quantify dental forces during double-lumen tube intubations with different laryngoscopy techniques. Design : Experimental biomechanical manikin study. Setting : Two German university hospitals. Participants : 104 anaesthetists with varying levels of experience. Interventions : Participants performed a sequence of intubations on a manikin equipped with hidden forces sensors in the maxillary incisors. Different laryngoscopy techniques were evaluated under normal and difficult airway conditions. Direct laryngoscopy was compared to different videolaryngoscopy techniques: the C-MAC with a Macintosh blade, the GlideScope and the KingVision with hyperangulated blades. Measurements and Main Results : A total of 624 intubations were evaluated. In normal airway conditions, the median (IQR [range]) peak forces were significantly lower when the GlideScope (15.7 (11.3-22.0[2.1-110.5]) N) was used compared to direct laryngoscopy (21.0 (14.1-28.5[4.7-168.6]) N) (p=0.007). In difficult airways, resulting forces were reduced using hyperangulated videolaryngoscopes (GlideScope -13.7 N (p<0.001); KingVision -11.9 N (p<0.001)) compared to direct laryngoscopy, respectively. The time to intubation was prolonged with the use of the KingVision (25.5 (17.1-41.9[9.2-275.0])) s (p<0.001)) in comparison to direct laryngoscopy (20.8 (15.9-27.4[8.7-198.6]) s). The C-MAC demonstrated the shortest time to intubation. Conclusions : While hyperangulated videolaryngoscopes improve dental strain, clinicians should also consider the time to intubation, which is shortest with non-hyperangulated videoblades, when choosing a laryngoscopy technique on an individual patient basis.},
 bibtype = {article},
 author = {Defosse, Jerome and Kleinschmidt, Joris and Schmutz, Axel and Torsten, Loop and Staat, Manfred and Gatzweiler, Karl-Heinz and Wappler, Frank and Schieren, Mark},
 doi = {10.1053/j.jvca.2022.02.017},
 journal = {Journal of Cardiothoracic and Vascular Anesthesia}
}

Objectives : To quantify dental forces during double-lumen tube intubations with different laryngoscopy techniques. Design : Experimental biomechanical manikin study. Setting : Two German university hospitals. Participants : 104 anaesthetists with varying levels of experience. Interventions : Participants performed a sequence of intubations on a manikin equipped with hidden forces sensors in the maxillary incisors. Different laryngoscopy techniques were evaluated under normal and difficult airway conditions. Direct laryngoscopy was compared to different videolaryngoscopy techniques: the C-MAC with a Macintosh blade, the GlideScope and the KingVision with hyperangulated blades. Measurements and Main Results : A total of 624 intubations were evaluated. In normal airway conditions, the median (IQR [range]) peak forces were significantly lower when the GlideScope (15.7 (11.3-22.0[2.1-110.5]) N) was used compared to direct laryngoscopy (21.0 (14.1-28.5[4.7-168.6]) N) (p=0.007). In difficult airways, resulting forces were reduced using hyperangulated videolaryngoscopes (GlideScope -13.7 N (p<0.001); KingVision -11.9 N (p<0.001)) compared to direct laryngoscopy, respectively. The time to intubation was prolonged with the use of the KingVision (25.5 (17.1-41.9[9.2-275.0])) s (p<0.001)) in comparison to direct laryngoscopy (20.8 (15.9-27.4[8.7-198.6]) s). The C-MAC demonstrated the shortest time to intubation. Conclusions : While hyperangulated videolaryngoscopes improve dental strain, clinicians should also consider the time to intubation, which is shortest with non-hyperangulated videoblades, when choosing a laryngoscopy technique on an individual patient basis.

@article{
 title = {Virgin passive colon biomechanics and a literature review of active contraction constitutive models},
 type = {article},
 year = {2022},
 pages = {138-157},
 volume = {2},
 websites = {https://www.mdpi.com/2673-7078/2/2/13},
 month = {3},
 day = {22},
 id = {5653e48e-4df1-3af6-8f29-bf3ce6eddb4f},
 created = {2022-03-17T13:17:36.677Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-03-22T19:45:02.999Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2022},
 private_publication = {false},
 abstract = {The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel–Gasser–Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill’s three-element model, Murphy’s four-state cross-bridge chemical kinetic model and Huxley’s sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine.},
 bibtype = {article},
 author = {Bhattarai, Aroj and Horbach, Andreas Johannes and Staat, Manfred and Kowalczyk, Wojciech and Tran, Thanh Ngoc},
 doi = {10.3390/biomechanics2020013},
 journal = {Biomechanics},
 number = {2}
}

The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel–Gasser–Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill’s three-element model, Murphy’s four-state cross-bridge chemical kinetic model and Huxley’s sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine.

@article{
 title = {Direct plastic structural design under random strength and random load by chance constrained programming},
 type = {article},
 year = {2021},
 keywords = {chance constrained programming,limit analysis,lower bound,reliability,shakedown analysis,stochastic programming,upper bound},
 pages = {104106},
 volume = {85},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0997753820304940},
 month = {1},
 id = {a381c51d-3ffc-3b63-9365-f9d1b04d83e7},
 created = {2020-08-21T15:51:20.560Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-12-07T10:30:30.254Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {TrinhTran2020},
 private_publication = {false},
 abstract = {A new formulation to calculate shakedown limit load of structures under stochastic conditions of strength and loading is developed. Direct structural reliability design is based on the required failure probabilities by chance constrained programming, which is an effective approach of stochastic programming if it can be formulated as an equivalent deterministic optimization problem.},
 bibtype = {article},
 author = {Trần, Ngọc Trình and Staat, Manfred},
 doi = {10.1016/j.euromechsol.2020.104106},
 journal = {European Journal of Mechanics - A/Solids},
 number = {1}
}

A new formulation to calculate shakedown limit load of structures under stochastic conditions of strength and loading is developed. Direct structural reliability design is based on the required failure probabilities by chance constrained programming, which is an effective approach of stochastic programming if it can be formulated as an equivalent deterministic optimization problem.

@article{
 title = {Intratendinous strain variations of the supraspinatus tendon depending on repair technique: A biomechanical analysis regarding the cause of medial cuff failure.},
 type = {article},
 year = {2021},
 keywords = {biomechanics,double row,intratendinous strain variations,medial cuff failure,medial row failure,rotator cuff repair,rotator cuff tear,single row,supraspinatus,suture bridge},
 pages = {1847-1853},
 volume = {49},
 websites = {http://journals.sagepub.com/doi/10.1177/03635465211006138,http://www.ncbi.nlm.nih.gov/pubmed/33872064},
 month = {4},
 day = {19},
 id = {4e85b36d-ba41-3674-af24-e29128584c0d},
 created = {2021-04-19T16:52:52.917Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-08-17T10:39:45.292Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2021},
 private_publication = {false},
 abstract = {BACKGROUND Double-row (DR) and transosseous-equivalent (TOE) techniques for rotator cuff repair offer more stability and promote better tendon healing compared with single-row (SR) repairs and are preferred by many surgeons. However, they can lead to more disastrous retear patterns with failure at the medial anchor row or the musculotendinous junction. The biomechanics of medial cuff failure have not been thoroughly investigated thus far. PURPOSE To investigate the intratendinous strain distribution within the supraspinatus tendon depending on repair technique. STUDY DESIGN Controlled laboratory study. METHODS Twelve fresh-frozen cadaveric shoulders were used. The intratendinous strain within the supraspinatus tendon was analyzed in 2 regions-(1) at the footprint at the greater tuberosity and (2) medial to the footprint up to the musculotendinous junction-using a high-resolution 3-dimensional camera system. Testing was performed at submaximal loads of 40 N, 60 N, and 80 N for intact tendons, after SR repair, after DR repair, and after TOE repair. RESULTS The tendon strain of the SR group differed significantly in both regions from that of the intact tendons and the TOE group at 40 N (P≤ .043) and from the intact tendons, the DR group, and the TOE group at 60 N and 80 N (P≤ .048). SR repairs showed more tendon elongation at the footprint and less elongation medial to the footprint. DR and TOE repairs did not provide significant differences in tendon strain when compared with the intact tendons. However, the increase in tendon strain medial to the footprint from 40 N to 80 N was significantly more pronounced in the DR and TOE group (P≤ .029). CONCLUSION While DR and TOE repair techniques more closely reproduced the strains of the supraspinatus tendon than did SR repair in a cadaveric model, they showed a significantly increased tendon strain at the musculotendinous junction with higher loads in comparison with the intact tendon. CLINICAL RELEVANCE DR and TOE rotator cuff reconstructions lead to a more anatomic tendon repair. However, their use has to be carefully evaluated whenever tendon quality is diminished, as they lead to a more drastic increase in tendon strain medial to the footprint, putting these repairs at risk of medial cuff failure.},
 bibtype = {article},
 author = {Hackl, Michael and Nacov, Julia and Kammerlohr, Sandra and Staat, Manfred and Buess, Eduard and Leschinger, Tim and Müller, Lars P. and Wegmann, Kilian},
 doi = {10.1177/03635465211006138},
 journal = {The American journal of sports medicine},
 number = {7}
}

BACKGROUND Double-row (DR) and transosseous-equivalent (TOE) techniques for rotator cuff repair offer more stability and promote better tendon healing compared with single-row (SR) repairs and are preferred by many surgeons. However, they can lead to more disastrous retear patterns with failure at the medial anchor row or the musculotendinous junction. The biomechanics of medial cuff failure have not been thoroughly investigated thus far. PURPOSE To investigate the intratendinous strain distribution within the supraspinatus tendon depending on repair technique. STUDY DESIGN Controlled laboratory study. METHODS Twelve fresh-frozen cadaveric shoulders were used. The intratendinous strain within the supraspinatus tendon was analyzed in 2 regions-(1) at the footprint at the greater tuberosity and (2) medial to the footprint up to the musculotendinous junction-using a high-resolution 3-dimensional camera system. Testing was performed at submaximal loads of 40 N, 60 N, and 80 N for intact tendons, after SR repair, after DR repair, and after TOE repair. RESULTS The tendon strain of the SR group differed significantly in both regions from that of the intact tendons and the TOE group at 40 N (P≤ .043) and from the intact tendons, the DR group, and the TOE group at 60 N and 80 N (P≤ .048). SR repairs showed more tendon elongation at the footprint and less elongation medial to the footprint. DR and TOE repairs did not provide significant differences in tendon strain when compared with the intact tendons. However, the increase in tendon strain medial to the footprint from 40 N to 80 N was significantly more pronounced in the DR and TOE group (P≤ .029). CONCLUSION While DR and TOE repair techniques more closely reproduced the strains of the supraspinatus tendon than did SR repair in a cadaveric model, they showed a significantly increased tendon strain at the musculotendinous junction with higher loads in comparison with the intact tendon. CLINICAL RELEVANCE DR and TOE rotator cuff reconstructions lead to a more anatomic tendon repair. However, their use has to be carefully evaluated whenever tendon quality is diminished, as they lead to a more drastic increase in tendon strain medial to the footprint, putting these repairs at risk of medial cuff failure.

@inproceedings{
 title = {FEM shakedown analysis of Kirchhoff-Love plates under uncertainty of strength},
 type = {inproceedings},
 year = {2021},
 keywords = {Chance Constrained Programming,Kirchhoff Plate,Limit Analysis,Primal Dual Programming,Shakedown Analysis,Stochastic Programming},
 pages = {323-338},
 websites = {https://generalconferencefiles.s3.eu-west-1.amazonaws.com/uncecomp_2021_proceedings.pdf,https://www.eccomasproceedia.org/conferences/thematic-conferences/uncecomp-2021/8041},
 publisher = {Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece},
 city = {Athens},
 id = {1e723ae3-a0e2-3390-bf9f-6d7dc5989adc},
 created = {2021-06-03T22:48:18.066Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-02-02T19:18:54.734Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Tran2021},
 private_publication = {false},
 abstract = {A new formulation to calculate the shakedown limit load of Kirchhoff plates under stochastic conditions of strength is developed. Direct structural reliability design by chance con-strained programming is based on the prescribed failure probabilities, which is an effective approach of stochastic programming if it can be formulated as an equivalent deterministic optimization problem. We restrict uncertainty to strength, the loading is still deterministic. A new formulation is derived in case of random strength with lognormal distribution. Upper bound and lower bound shakedown load factors are calculated simultaneously by a dual algorithm.},
 bibtype = {inproceedings},
 author = {Trần, Ngọc Trình and Staat, Manfred},
 editor = {Papadrakakis, Manolis and Papadopoulos, Vissarion and Stefanou, George},
 doi = {10.7712/120221.8041.19047},
 booktitle = {UNCECOMP 2021, 4th International Conference on Uncertainty Quantification in Computational Sciences and Engineering, Streamed from Athens, Greece, 28–30 June 2021}
}

A new formulation to calculate the shakedown limit load of Kirchhoff plates under stochastic conditions of strength is developed. Direct structural reliability design by chance con-strained programming is based on the prescribed failure probabilities, which is an effective approach of stochastic programming if it can be formulated as an equivalent deterministic optimization problem. We restrict uncertainty to strength, the loading is still deterministic. A new formulation is derived in case of random strength with lognormal distribution. Upper bound and lower bound shakedown load factors are calculated simultaneously by a dual algorithm.

@techreport{
 title = {Plattformtechnologie für kardiale Sicherheitspharmakologie basierend auf teilsynthetischem Herzmuskelgewebe (FLEXcyte)},
 type = {techreport},
 year = {2021},
 pages = {85, IV},
 websites = {https://www.tib.eu/de/suchen/id/TIBKAT:1771590602},
 city = {München},
 institution = {Nanion Technologies GmbH},
 id = {0c7cff6a-9e40-3c5d-afef-0242dcf29d15},
 created = {2021-06-28T13:03:45.670Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-09-27T08:47:17.459Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Stolzle-Feix2021},
 private_publication = {false},
 abstract = {Das Ziel der Verwendung von humanen, induzierten, pluripotenten Stammzellen beim präklinischen Wirkstoff-Screening und bei der Modellierung von Krankheiten sollte weltweite Unterstützung finden. Es ist nicht nur aus ethischen Gründen und zur Vermeidung von Tiermodellen für die Forschung relevant, sondern es besteht auch die Tatsache, dass induzierte Kardiomyozyten aus humanen, pluripotenten Stammzellen (hiPSC-CMs) vergleichbare Ergebnisse wie menschliche, adulte Kardiomyozyten liefern. Sie stellen eine billige und gültige Alternative zu typischerweise verwendeten, embryonalen Stammzellen dar, die im Fötusstadium aus Blastozysten extrahiert werden. HiPSC-CMs fehlt jedoch immer noch ein ähnlicher Reifegrad, der sich gut mit tatsächlichen Kardiomyozyten des menschlichen Herzgewebes vergleichen lässt. Der Ansatz des hier beschriebenen Vorhabens bestand darin, das FLEXcyte 96 System zu entwickeln, welches durch Anwendung mechanischer Stimulation einen reifen Phänotyp in hiPSC-CMs fördern kann. Dabei werden die Zellen auf einem flexiblen Substrat kultiviert. Die Ergebnisse zeigen, dass eine Kultivierung auf flexiblem Substrat und eine zyklische, mechanische Stimulation die Zellreifung förderte. Im Vergleich zu nicht stimulierten Zellen entwickelten sie signifikant höhere Amplituden, verringerte Schlagraten, schnellere Relaxation und Aufwärtsgeschwindigkeiten, welches Anzeichen maturierter Zellen sind. Das Ziel des Projektes war es, eine Hochdurchsatz Assay-Technologie für Sicherheitspharmakologie an kardialen Stammzellen zu entwickeln. Simulationsrechnungen anhand in-silico Computermodellen dienten der Validierung des Gesamtsystems und ermöglichen einen Vergleich mit bestehenden, etablierten Systemen. Solche Hochdurchsatz-Assays werden verwendet, um die Kardiotoxizität von pharmazeutischen Wirkstoffen zu prüfen. Der Erfolg des Projektes konnte dadurch gewährleistet werden, dass Expertisen aus den Bereichen stammzell-abgeleitete Kardiomyozyten, automatisierte Screening Plattformen und Sicherheitspharmakologie kombiniert wurden. Das Ergebnis dieser Arbeit zeigt, wie wichtig es ist, die Reifung von hiPSC-CMs für ein zuverlässigeres, präklinisches Wirkstoff-Screening zu fördern. Die in diesem Projekt entwickelte Assay-Plattform hat das Potenzial, die Lücke zwischen Skalierbarkeit und der nötigen Aussagekraft des Assays bei der Medikamenten-Entwicklung zu schließen.},
 bibtype = {techreport},
 author = {Stölzle-Feix, Sonja and Thomas, Ulrich and Engelstädter, Max and Goßmann, Matthias and Linder, Peter and Staat, Manfred and Raman, Aravind Hariharan and Jung, Alexander and Fertig, Niels}
}

Das Ziel der Verwendung von humanen, induzierten, pluripotenten Stammzellen beim präklinischen Wirkstoff-Screening und bei der Modellierung von Krankheiten sollte weltweite Unterstützung finden. Es ist nicht nur aus ethischen Gründen und zur Vermeidung von Tiermodellen für die Forschung relevant, sondern es besteht auch die Tatsache, dass induzierte Kardiomyozyten aus humanen, pluripotenten Stammzellen (hiPSC-CMs) vergleichbare Ergebnisse wie menschliche, adulte Kardiomyozyten liefern. Sie stellen eine billige und gültige Alternative zu typischerweise verwendeten, embryonalen Stammzellen dar, die im Fötusstadium aus Blastozysten extrahiert werden. HiPSC-CMs fehlt jedoch immer noch ein ähnlicher Reifegrad, der sich gut mit tatsächlichen Kardiomyozyten des menschlichen Herzgewebes vergleichen lässt. Der Ansatz des hier beschriebenen Vorhabens bestand darin, das FLEXcyte 96 System zu entwickeln, welches durch Anwendung mechanischer Stimulation einen reifen Phänotyp in hiPSC-CMs fördern kann. Dabei werden die Zellen auf einem flexiblen Substrat kultiviert. Die Ergebnisse zeigen, dass eine Kultivierung auf flexiblem Substrat und eine zyklische, mechanische Stimulation die Zellreifung förderte. Im Vergleich zu nicht stimulierten Zellen entwickelten sie signifikant höhere Amplituden, verringerte Schlagraten, schnellere Relaxation und Aufwärtsgeschwindigkeiten, welches Anzeichen maturierter Zellen sind. Das Ziel des Projektes war es, eine Hochdurchsatz Assay-Technologie für Sicherheitspharmakologie an kardialen Stammzellen zu entwickeln. Simulationsrechnungen anhand in-silico Computermodellen dienten der Validierung des Gesamtsystems und ermöglichen einen Vergleich mit bestehenden, etablierten Systemen. Solche Hochdurchsatz-Assays werden verwendet, um die Kardiotoxizität von pharmazeutischen Wirkstoffen zu prüfen. Der Erfolg des Projektes konnte dadurch gewährleistet werden, dass Expertisen aus den Bereichen stammzell-abgeleitete Kardiomyozyten, automatisierte Screening Plattformen und Sicherheitspharmakologie kombiniert wurden. Das Ergebnis dieser Arbeit zeigt, wie wichtig es ist, die Reifung von hiPSC-CMs für ein zuverlässigeres, präklinisches Wirkstoff-Screening zu fördern. Die in diesem Projekt entwickelte Assay-Plattform hat das Potenzial, die Lücke zwischen Skalierbarkeit und der nötigen Aussagekraft des Assays bei der Medikamenten-Entwicklung zu schließen.

@article{
 title = {A "Comma sign"-directed subscapularis repair in anterosuperior rotator cuff tears yields biomechanical advantages in a cadaveric model.},
 type = {article},
 year = {2021},
 keywords = {arthroscopy,biomechanics,comma sign,rotator cuff repair,shoulder,subscapularis},
 pages = {3212-3217},
 volume = {49},
 websites = {http://journals.sagepub.com/doi/10.1177/03635465211031506,http://www.ncbi.nlm.nih.gov/pubmed/34398639},
 month = {10},
 day = {16},
 id = {82195e9c-12db-3a00-8432-e08f912f7eeb},
 created = {2021-08-17T08:20:45.569Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-01-03T08:29:43.512Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2021},
 private_publication = {false},
 abstract = {BACKGROUND Additional stabilization of the "comma sign" in anterosuperior rotator cuff repair has been proposed to provide biomechanical benefits regarding stability of the repair. PURPOSE This in vitro investigation aimed to investigate the influence of a comma sign-directed reconstruction technique for anterosuperior rotator cuff tears on the primary stability of the subscapularis tendon repair. STUDY DESIGN Controlled laboratory study. METHODS A total of 18 fresh-frozen cadaveric shoulders were used in this study. Anterosuperior rotator cuff tears (complete full-thickness tear of the supraspinatus and subscapularis tendons) were created, and supraspinatus repair was performed with a standard suture bridge technique. The subscapularis was repaired with either a (1) single-row or (2) comma sign technique. A high-resolution 3D camera system was used to analyze 3-mm and 5-mm gap formation at the subscapularis tendon-bone interface upon incremental cyclic loading. Moreover, the ultimate failure load of the repair was recorded. A Mann-Whitney test was used to assess significant differences between the 2 groups. RESULTS The comma sign repair withstood significantly more loading cycles than the single-row repair until 3-mm and 5-mm gap formation occurred (P≤ .047). The ultimate failure load did not reveal any significant differences when the 2 techniques were compared (P = .596). CONCLUSION The results of this study show that additional stabilization of the comma sign enhanced the primary stability of subscapularis tendon repair in anterosuperior rotator cuff tears. Although this stabilization did not seem to influence the ultimate failure load, it effectively decreased the micromotion at the tendon-bone interface during cyclic loading. CLINICAL RELEVANCE The proposed technique for stabilization of the comma sign has shown superior biomechanical properties in comparison with a single-row repair and might thus improve tendon healing. Further clinical research will be necessary to determine its influence on the functional outcome.},
 bibtype = {article},
 author = {Hackl, Michael and Buess, Eduard and Kammerlohr, Sandra and Nacov, Julia and Staat, Manfred and Leschinger, Tim and Müller, Lars Peter and Wegmann, Kilian},
 doi = {10.1177/03635465211031506},
 journal = {The American journal of sports medicine},
 number = {12}
}

BACKGROUND Additional stabilization of the "comma sign" in anterosuperior rotator cuff repair has been proposed to provide biomechanical benefits regarding stability of the repair. PURPOSE This in vitro investigation aimed to investigate the influence of a comma sign-directed reconstruction technique for anterosuperior rotator cuff tears on the primary stability of the subscapularis tendon repair. STUDY DESIGN Controlled laboratory study. METHODS A total of 18 fresh-frozen cadaveric shoulders were used in this study. Anterosuperior rotator cuff tears (complete full-thickness tear of the supraspinatus and subscapularis tendons) were created, and supraspinatus repair was performed with a standard suture bridge technique. The subscapularis was repaired with either a (1) single-row or (2) comma sign technique. A high-resolution 3D camera system was used to analyze 3-mm and 5-mm gap formation at the subscapularis tendon-bone interface upon incremental cyclic loading. Moreover, the ultimate failure load of the repair was recorded. A Mann-Whitney test was used to assess significant differences between the 2 groups. RESULTS The comma sign repair withstood significantly more loading cycles than the single-row repair until 3-mm and 5-mm gap formation occurred (P≤ .047). The ultimate failure load did not reveal any significant differences when the 2 techniques were compared (P = .596). CONCLUSION The results of this study show that additional stabilization of the comma sign enhanced the primary stability of subscapularis tendon repair in anterosuperior rotator cuff tears. Although this stabilization did not seem to influence the ultimate failure load, it effectively decreased the micromotion at the tendon-bone interface during cyclic loading. CLINICAL RELEVANCE The proposed technique for stabilization of the comma sign has shown superior biomechanical properties in comparison with a single-row repair and might thus improve tendon healing. Further clinical research will be necessary to determine its influence on the functional outcome.

@article{
 title = {An Extension Strain Type Mohr–Coulomb Criterion},
 type = {article},
 year = {2021},
 pages = {6207-6233},
 volume = {54},
 websites = {https://link.springer.com/10.1007/s00603-021-02608-7},
 month = {12},
 day = {20},
 id = {1b5ad81e-6c15-3c09-8cc4-81adbd261339},
 created = {2021-08-20T20:00:43.830Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-11-26T21:49:31.437Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2021},
 private_publication = {false},
 abstract = {Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr–Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1007/s00603-021-02608-7},
 journal = {Rock Mechanics and Rock Engineering},
 number = {12}
}

Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr–Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.

@article{
 title = {Corrigendum to "Wind and fairness in ski jumping: A computer modelling analysis" [J. Biomech. 75 (2018) 147-153].},
 type = {article},
 year = {2021},
 pages = {110690},
 volume = {128},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0021929021004590,http://www.ncbi.nlm.nih.gov/pubmed/34536903},
 month = {9},
 day = {15},
 id = {ce26fb38-95e1-30bf-b630-2c039de976da},
 created = {2021-09-21T01:27:55.571Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-03-23T10:38:35.333Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2021},
 private_publication = {false},
 bibtype = {article},
 author = {Jung, Alexander and Müller, Wolfram and Staat, Manfred},
 doi = {10.1016/j.jbiomech.2021.110690},
 journal = {Journal of Biomechanics}
}

@article{
 title = {Direct plastic structural design under lognormally distributed strength by chance constrained programming},
 type = {article},
 year = {2020},
 keywords = {chance constrained programming,limit analysis,primal dual programming,shakedown analysis,stochastic programming,structural reliability},
 pages = {131-157},
 volume = {21},
 websites = {http://link.springer.com/10.1007/s11081-019-09437-2,https://rdcu.be/bxiaz},
 id = {6f0ba919-3796-3b2a-afcf-ff1d77357145},
 created = {2019-04-04T06:55:43.054Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-01-23T18:12:53.224Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Tran2020},
 private_publication = {false},
 abstract = {We propose the so-called chance constrained programming model of stochastic programming to analyze limit and shakedown loads of structures under random strength with a lognormal distribution. A dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit. The edge-based smoothed finite element method (ES-FEM) is used with three-node linear triangular elements.},
 bibtype = {article},
 author = {Trần, Ngọc Trình and Staat, Manfred},
 doi = {10.1007/s11081-019-09437-2},
 journal = {Optimization and Engineering},
 number = {1}
}

We propose the so-called chance constrained programming model of stochastic programming to analyze limit and shakedown loads of structures under random strength with a lognormal distribution. A dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit. The edge-based smoothed finite element method (ES-FEM) is used with three-node linear triangular elements.

@article{
 title = {A computational study of organ relocation after laparoscopic pectopexy to repair posthysterectomy vaginal vault prolapse},
 type = {article},
 year = {2020},
 pages = {277-286},
 volume = {8},
 websites = {https://www.tandfonline.com/doi/full/10.1080/21681163.2019.1670095},
 month = {4},
 day = {29},
 id = {fda44c3c-86a0-3bcb-aa99-ad7ca4008809},
 created = {2019-09-26T11:30:39.105Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-04-29T13:04:15.869Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2019},
 private_publication = {false},
 abstract = {Minimally invasive surgery such as laparoscopic sacrocolpopexy, pectopexy and cervicosacropexy are widely performed for the treatment of the vaginal vault/cuff prolapse using prosthetic mesh implants to strengthen lax apical ligaments. Depending on the patient’s anatomy and the surgeon’s preference, implants of different shapes, pore architectures and polymers can be selected. In this article, a 3D model of the pelvis was built and the pectopexy technique was reproduced. The finite element model of the textile implant was sutured to the cervical stump with a bilateral fixation to the iliopectineal ligament on either side of the pelvic walls. Pelvic soft tissues and prosthetic implants were modelled as hyperelastic and linearly elastic orthotropic materials, respectively. Numerical simulations were performed after surgery at rest and during Valsalva manoeuvre. The positions and the orientation of the vagina, during increased abdominal pressure were calculated in relation to the pubococcygeal line (PCL). We found from our simulation-model that the structure of the DynaMesh®-PRP Soft (17.18 mm above PCL line) provides better support to the vaginal cuff compared to GYNEMESH (11.95 mm) and ARTISYN (6.72 mm). And the treatment with, the stiffer DynaMesh seems to provide better urethral axis (24°) than the flexible Ethicon meshes (28.5° and 29°).},
 bibtype = {article},
 author = {Bhattarai, Aroj and Staat, Manfred},
 doi = {10.1080/21681163.2019.1670095},
 journal = {Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization},
 number = {3}
}

Minimally invasive surgery such as laparoscopic sacrocolpopexy, pectopexy and cervicosacropexy are widely performed for the treatment of the vaginal vault/cuff prolapse using prosthetic mesh implants to strengthen lax apical ligaments. Depending on the patient’s anatomy and the surgeon’s preference, implants of different shapes, pore architectures and polymers can be selected. In this article, a 3D model of the pelvis was built and the pectopexy technique was reproduced. The finite element model of the textile implant was sutured to the cervical stump with a bilateral fixation to the iliopectineal ligament on either side of the pelvic walls. Pelvic soft tissues and prosthetic implants were modelled as hyperelastic and linearly elastic orthotropic materials, respectively. Numerical simulations were performed after surgery at rest and during Valsalva manoeuvre. The positions and the orientation of the vagina, during increased abdominal pressure were calculated in relation to the pubococcygeal line (PCL). We found from our simulation-model that the structure of the DynaMesh®-PRP Soft (17.18 mm above PCL line) provides better support to the vaginal cuff compared to GYNEMESH (11.95 mm) and ARTISYN (6.72 mm). And the treatment with, the stiffer DynaMesh seems to provide better urethral axis (24°) than the flexible Ethicon meshes (28.5° and 29°).

@article{
 title = {An open-source tool for the validation of finite element models using three-dimensional full-field measurements},
 type = {article},
 year = {2020},
 keywords = {3D point-set registration,Biomechanics,Digital image correlation (DIC),Global optimization,Synthetic bone},
 pages = {125-129},
 volume = {77},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S1350453319302437,http://www.ncbi.nlm.nih.gov/pubmed/31952915},
 month = {1},
 day = {15},
 id = {8d4156a5-e9d6-31bc-8bf1-3a868b72452f},
 created = {2020-01-28T07:52:43.679Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-10-01T09:19:53.360Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Abel2020},
 private_publication = {false},
 abstract = {Three-dimensional (3D) full-field measurements provide a comprehensive and accurate validation of finite element (FE) models. For the validation, the result of the model and measurements are compared based on two respective point-sets and this requires the point-sets to be registered in one coordinate system. Point-set registration is a non-convex optimization problem that has widely been solved by the ordinary iterative closest point algorithm. However, this approach necessitates a good initialization without which it easily returns a local optimum, i.e. an erroneous registration. The globally optimal iterative closest point (Go-ICP) algorithm has overcome this drawback and forms the basis for the presented open-source tool that can be used for the validation of FE models using 3D full-field measurements. The capability of the tool is demonstrated using an application example from the field of biomechanics. Methodological problems that arise in real-world data and the respective implemented solution approaches are discussed.},
 bibtype = {article},
 author = {Abel, Alexander and Kahmann, Stephanie L. and Mellon, Stephen and Staat, Manfred and Jung, Alexander},
 doi = {10.1016/j.medengphy.2019.10.015},
 journal = {Medical Engineering & Physics}
}

Three-dimensional (3D) full-field measurements provide a comprehensive and accurate validation of finite element (FE) models. For the validation, the result of the model and measurements are compared based on two respective point-sets and this requires the point-sets to be registered in one coordinate system. Point-set registration is a non-convex optimization problem that has widely been solved by the ordinary iterative closest point algorithm. However, this approach necessitates a good initialization without which it easily returns a local optimum, i.e. an erroneous registration. The globally optimal iterative closest point (Go-ICP) algorithm has overcome this drawback and forms the basis for the presented open-source tool that can be used for the validation of FE models using 3D full-field measurements. The capability of the tool is demonstrated using an application example from the field of biomechanics. Methodological problems that arise in real-world data and the respective implemented solution approaches are discussed.

@article{
 title = {Combining physiological relevance and throughput for in vitro cardiac contractility measurement},
 type = {article},
 year = {2020},
 pages = {570a},
 volume = {118},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0006349519340378},
 month = {2},
 id = {c4ae9912-5c01-3fd9-9cf1-feb826aa09db},
 created = {2020-02-13T19:43:16.639Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:44:00.041Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Knox2020},
 private_publication = {false},
 bibtype = {article},
 author = {Knox, Ronald and Bruggemann, Andrea and Gossmann, Matthias and Thomas, Ulrich and Horváth, András and Dragicevic, Elena and Stoelzle-Feix, Sonja and Fertig, Niels and Jung, Alexander and Raman, Aravind Hariharan and Staat, Manfred and Linder, Peter},
 doi = {10.1016/j.bpj.2019.11.3104},
 journal = {Biophysical Journal},
 number = {3, Suppl. 1}
}

@article{
 title = {Pressure distribution to the distal biceps tendon at the radial tuberosity: a biomechanical study},
 type = {article},
 year = {2020},
 keywords = {Biomechanics elbow,distal biceps tendon,elbow anatomy,radial tuberosity,tendon repair},
 pages = {776.e1-776.e9},
 volume = {45},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0363502320300319,http://www.ncbi.nlm.nih.gov/pubmed/32151407,https://www.jhandsurg.org/article/S0363-5023(20)30031-9},
 month = {8},
 day = {1},
 id = {ee6b6564-1948-3b38-96f3-794104cf0682},
 created = {2020-03-09T14:59:57.636Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-10-01T13:15:43.712Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Rausch2020},
 private_publication = {false},
 abstract = {PURPOSE Mechanical impingement at the narrow radioulnar space of the tuberosity is believed to be an etiological factor in the injury of the distal biceps tendon. The aim of the study was to compare the pressure distribution at the proximal radioulnar space between 2 fixation techniques and the intact state. METHODS Six right arms and 6 left arms from 5 female and 6 male frozen specimens were used for this study. A pressure transducer was introduced at the height of the radial tuberosity with the intact distal biceps tendon and after 2 fixation methods: the suture-anchor and the cortical button technique. The force (N), maximum pressure (kPa) applied to the radial tuberosity, and the contact area (mm²) of the radial tuberosity with the ulna were measured and differences from the intact tendon were detected from 60° supination to 60° pronation in 15° increments with the elbow in full extension and in 45° and 90° flexion of the elbow. RESULTS With the distal biceps tendon intact, the pressures during pronation were similar regardless of extension and flexion and were the highest at 60° pronation with 90° elbow flexion (23.3 ± 53.5 kPa). After repair of the tendon, the mean peak pressure, contact area, and total force showed an increase regardless of the fixation technique. Highest peak pressures were found using the cortical button technique at 45° flexion of the elbow and 60° pronation. These differences were significantly different from the intact tendon. The contact area was significantly larger in full extension and 15°, 30°, and 60° pronation using the cortical button technique. CONCLUSIONS Pressures on the distal biceps tendon at the radial tuberosity increase during pronation, especially after repair of the tendon. CLINICAL RELEVANCE Mechanical impingement could play a role in both the etiology of primary distal biceps tendon ruptures and the complications occurring after fixation of the tendon using certain techniques.},
 bibtype = {article},
 author = {Rausch, Valentin and Kahmann, Stephanie L. and Baltschun, Christoph and Staat, Manfred and Müller, Lars P. and Wegmann, Kilian},
 doi = {10.1016/j.jhsa.2020.01.006},
 journal = {The Journal of Hand Surgery},
 number = {8}
}

PURPOSE Mechanical impingement at the narrow radioulnar space of the tuberosity is believed to be an etiological factor in the injury of the distal biceps tendon. The aim of the study was to compare the pressure distribution at the proximal radioulnar space between 2 fixation techniques and the intact state. METHODS Six right arms and 6 left arms from 5 female and 6 male frozen specimens were used for this study. A pressure transducer was introduced at the height of the radial tuberosity with the intact distal biceps tendon and after 2 fixation methods: the suture-anchor and the cortical button technique. The force (N), maximum pressure (kPa) applied to the radial tuberosity, and the contact area (mm²) of the radial tuberosity with the ulna were measured and differences from the intact tendon were detected from 60° supination to 60° pronation in 15° increments with the elbow in full extension and in 45° and 90° flexion of the elbow. RESULTS With the distal biceps tendon intact, the pressures during pronation were similar regardless of extension and flexion and were the highest at 60° pronation with 90° elbow flexion (23.3 ± 53.5 kPa). After repair of the tendon, the mean peak pressure, contact area, and total force showed an increase regardless of the fixation technique. Highest peak pressures were found using the cortical button technique at 45° flexion of the elbow and 60° pronation. These differences were significantly different from the intact tendon. The contact area was significantly larger in full extension and 15°, 30°, and 60° pronation using the cortical button technique. CONCLUSIONS Pressures on the distal biceps tendon at the radial tuberosity increase during pronation, especially after repair of the tendon. CLINICAL RELEVANCE Mechanical impingement could play a role in both the etiology of primary distal biceps tendon ruptures and the complications occurring after fixation of the tendon using certain techniques.

@article{
 title = {Osteosynthesis of phalangeal fractures: biomechanical comparison of Kirschner wires, plates, and compression screws},
 type = {article},
 year = {2020},
 keywords = {3-dimensional digital image correlation measuremen,Proximal phalanx,biomechanics,cadaver study,cannulated headless compression screw},
 pages = {987.e1-987.e8},
 volume = {45},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0363502320302124,https://www.jhandsurg.org/article/S0363-5023(20)30212-4/pdf,http://www.ncbi.nlm.nih.gov/pubmed/32499069},
 day = {1},
 id = {164a6bd3-b975-3fb2-ac8e-8618de1d84a3},
 created = {2020-06-02T19:11:07.825Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-10-01T09:38:22.320Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Rausch2020},
 private_publication = {false},
 abstract = {PURPOSE The aim of this study was to compare several osteosynthesis techniques (intramedullary headless compression screws, T-plates, and Kirschner wires) for distal epiphyseal fractures of proximal phalanges in a human cadaveric model. METHODS A total of 90 proximal phalanges from 30 specimens (index, ring, and middle fingers) were used for this study. After stripping off all soft tissue, a transverse distal epiphyseal fracture was simulated at the proximal phalanx. The 30 specimens were randomly assigned to 1 fixation technique (30 per technique), either a 3.0-mm intramedullary headless compression screw, locking plate fixation with a 2.0-mm T-plate, or 2 oblique 1.0-mm Kirschner wires. Displacement analysis (bending, distraction, and torsion) was performed using optical tracking of an applied random speckle pattern after osteosynthesis. Biomechanical testing was performed with increasing cyclic loading and with cyclic load to failure using a biaxial torsion-tension testing machine. RESULTS Cannulated intramedullary compression screws showed significantly less displacement at the fracture site in torsional testing. Furthermore, screws were significantly more stable in bending testing. Kirschner wires were significantly less stable than plating or screw fixation in any cyclic load to failure test setup. CONCLUSIONS Intramedullary compression screws are a highly stable alternative in the treatment of transverse distal epiphyseal phalangeal fractures. Kirschner wires seem to be inferior regarding displacement properties and primary stability. CLINICAL RELEVANCE Fracture fixation of phalangeal fractures using plate osteosynthesis may have the advantage of a very rigid reduction, but disadvantages such as stiffness owing to the more invasive surgical approach and soft tissue irritation should be taken into account. Headless compression screws represent a minimally invasive choice for fixation with good biomechanical properties.},
 bibtype = {article},
 author = {Rausch, Valentin and Harbrecht, Andreas and Kahmann, Stephanie L. and Fenten, Thomas and Jovanovic, Nebojsa and Hackl, Michael and Müller, Lars P. and Staat, Manfred and Wegmann, Kilian},
 doi = {10.1016/j.jhsa.2020.04.010},
 journal = {The Journal of hand surgery},
 number = {10}
}

PURPOSE The aim of this study was to compare several osteosynthesis techniques (intramedullary headless compression screws, T-plates, and Kirschner wires) for distal epiphyseal fractures of proximal phalanges in a human cadaveric model. METHODS A total of 90 proximal phalanges from 30 specimens (index, ring, and middle fingers) were used for this study. After stripping off all soft tissue, a transverse distal epiphyseal fracture was simulated at the proximal phalanx. The 30 specimens were randomly assigned to 1 fixation technique (30 per technique), either a 3.0-mm intramedullary headless compression screw, locking plate fixation with a 2.0-mm T-plate, or 2 oblique 1.0-mm Kirschner wires. Displacement analysis (bending, distraction, and torsion) was performed using optical tracking of an applied random speckle pattern after osteosynthesis. Biomechanical testing was performed with increasing cyclic loading and with cyclic load to failure using a biaxial torsion-tension testing machine. RESULTS Cannulated intramedullary compression screws showed significantly less displacement at the fracture site in torsional testing. Furthermore, screws were significantly more stable in bending testing. Kirschner wires were significantly less stable than plating or screw fixation in any cyclic load to failure test setup. CONCLUSIONS Intramedullary compression screws are a highly stable alternative in the treatment of transverse distal epiphyseal phalangeal fractures. Kirschner wires seem to be inferior regarding displacement properties and primary stability. CLINICAL RELEVANCE Fracture fixation of phalangeal fractures using plate osteosynthesis may have the advantage of a very rigid reduction, but disadvantages such as stiffness owing to the more invasive surgical approach and soft tissue irritation should be taken into account. Headless compression screws represent a minimally invasive choice for fixation with good biomechanical properties.

@article{
 title = {Erratum to: Modeling and simulation of human induced pluripotent stem cell‐derived cardiac tissue (GAMM-Mitteilungen, (2019), 42, 4, 10.1002/gamm.201900002)},
 type = {article},
 year = {2020},
 pages = {e202000011},
 websites = {https://onlinelibrary.wiley.com/doi/abs/10.1002/gamm.202000011},
 month = {5},
 day = {28},
 id = {015e405f-cbfb-30bc-b1a2-3d5aafd7a6ae},
 created = {2020-06-05T18:41:43.496Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-06-06T04:45:20.274Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2020},
 private_publication = {false},
 bibtype = {article},
 author = {Jung, Alexander and Staat, Manfred},
 doi = {10.1002/gamm.202000011},
 journal = {GAMM-Mitteilungen}
}

@article{
 title = {Biomechanical in vitro examination of a standardized low-volume tubular femoroplasty},
 type = {article},
 year = {2020},
 keywords = {Biomechanical test,Femoroplasty,Osteoporosis,Prevention,Proximal femur fracture},
 pages = {105104},
 volume = {80},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0268003320302229,http://www.ncbi.nlm.nih.gov/pubmed/32712527},
 day = {1},
 id = {98715311-ac08-3d7e-b42c-d13e44af1ad6},
 created = {2020-06-12T14:20:03.055Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-10-01T09:32:55.511Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Horbach2020},
 folder_uuids = {adee5ffe-7473-40f0-bc96-24e6feec7c9b},
 private_publication = {false},
 abstract = {BACKGROUND Osteoporosis is associated with the risk of fractures near the hip. Age and comorbidities increase the perioperative risk. Due to the ageing population, fracture of the proximal femur also proves to be a socio-economic problem. Preventive surgical measures have hardly been used so far. METHODS 10 pairs of human femora from fresh cadavers were divided into control and low-volume femoroplasty groups and subjected to a Hayes fall-loading fracture test. The results of the respective localization and classification of the fracture site, the Singh index determined by computed tomography (CT) examination and the parameters in terms of fracture force, work to fracture and stiffness were evaluated statistically and with the finite element method. In addition, a finite element parametric study with different position angles and variants of the tubular geometry of the femoroplasty was performed. FINDINGS Compared to the control group, the work to fracture could be increased by 33.2%. The fracture force increased by 19.9%. The used technique and instrumentation proved to be standardized and reproducible with an average poly(methyl methacrylate) volume of 10.5 ml. The parametric study showed the best results for the selected angle and geometry. INTERPRETATION The cadaver studies demonstrated the biomechanical efficacy of the low-volume tubular femoroplasty. The numerical calculations confirmed the optimal choice of positioning as well as the inner and outer diameter of the tube in this setting. The standardized minimally invasive technique with the instruments developed for it could be used in further comparative studies to confirm the measured biomechanical results.},
 bibtype = {article},
 author = {Horbach, Andreas J. and Staat, Manfred and Pérez-Viana, Daniel and Simmen, Hans-Peter and Neuhaus, Valentin and Pape, Hans-Christoph and Prescher, Andreas and Ciritsis, Bernhard},
 doi = {10.1016/j.clinbiomech.2020.105104},
 journal = {Clinical Biomechanics}
}

BACKGROUND Osteoporosis is associated with the risk of fractures near the hip. Age and comorbidities increase the perioperative risk. Due to the ageing population, fracture of the proximal femur also proves to be a socio-economic problem. Preventive surgical measures have hardly been used so far. METHODS 10 pairs of human femora from fresh cadavers were divided into control and low-volume femoroplasty groups and subjected to a Hayes fall-loading fracture test. The results of the respective localization and classification of the fracture site, the Singh index determined by computed tomography (CT) examination and the parameters in terms of fracture force, work to fracture and stiffness were evaluated statistically and with the finite element method. In addition, a finite element parametric study with different position angles and variants of the tubular geometry of the femoroplasty was performed. FINDINGS Compared to the control group, the work to fracture could be increased by 33.2%. The fracture force increased by 19.9%. The used technique and instrumentation proved to be standardized and reproducible with an average poly(methyl methacrylate) volume of 10.5 ml. The parametric study showed the best results for the selected angle and geometry. INTERPRETATION The cadaver studies demonstrated the biomechanical efficacy of the low-volume tubular femoroplasty. The numerical calculations confirmed the optimal choice of positioning as well as the inner and outer diameter of the tube in this setting. The standardized minimally invasive technique with the instruments developed for it could be used in further comparative studies to confirm the measured biomechanical results.

@article{
 title = {A higher-throughput approach to investigate cardiac contractility in vitro under physiological mechanical conditions},
 type = {article},
 year = {2020},
 pages = {106843},
 volume = {105},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S1056871920301726},
 month = {9},
 id = {005a7632-d83f-32c9-afca-b9a82386d0d9},
 created = {2020-12-02T22:25:12.012Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-12-02T22:25:12.012Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Gossmann2020},
 private_publication = {false},
 bibtype = {article},
 author = {Gossmann, Matthias and Thomas, Ulrich and Horvath, Andras and Dragicevic, Elena and Stoelzle-Feix, Sonja and Fertig, Niels and Jung, Alexander and Raman, Aravind H. and Staat, Manfred and Linder, Peter},
 doi = {10.1016/j.vascn.2020.106843},
 journal = {Journal of Pharmacological and Toxicological Methods}
}

@article{
 title = {Postural and metabolic benefits of using a forearm support walker in older adults with impairments},
 type = {article},
 year = {2019},
 keywords = {Assistive technology,Elbow support,Elderly,Gait,Grip strength,Low back pain,Rehabilitation,Repeated strain injuries,Rollator walker,Trunk posture},
 pages = {638-647},
 volume = {100},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0003999318313844,http://www.ncbi.nlm.nih.gov/pubmed/30367875},
 month = {4},
 day = {24},
 id = {1999390d-9275-3abd-9579-aa4bc7c774c9},
 created = {2018-12-11T22:16:12.137Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:43:59.888Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jayaraman2018},
 private_publication = {false},
 abstract = {OBJECTIVE To investigate the postural and metabolic benefits a walker with adjustable elbow support (LifeWalker [LW]) can provide for ambulation in population with impairment. The clinical outcomes from the elbow support walker will be compared with standard rollator (SR) and participants predicate device (PD). DESIGN Case-crossover study design. SETTING Clinical laboratory. PARTICIPANTS Individuals aged between 18 and 85 years using a rollator walker as primary mode of assistance and certified as medically stable by their primary physician. Participants (N=30; 80% women [n=24]) recruited from a convenient sample provided voluntary consent and completed the study. INTERVENTION Not applicable. MAIN OUTCOME MEASURES The trunk anterior-posterior (AP) sway (during the 10-meter walk test), oxygen consumption (during the 6-minute walk test), the mean forearm load offloaded to the elbow support as percentage of body weight, and mean peak hand grip load (during the 25-meter walk test) were measured. RESULTS Ambulating with a LW led to (1) reduced trunk sway in the AP direction [(ZLW vs PD= -2.34, P=.018); (ZLW vs SR= -3.461, P=.001)]; (2) reduced erector spinae muscle activation at the left lumbar L3 level [(ZLW vs PD= -2.71, P=.007); (ZLW vs SR= -1.71, P=.09)]; and (3) improved gait efficiency [(ZLW vs PD= -2.66, P=.008) Oxygen cost; (ZLW Vs. SR= -2.66, P=.008) Oxygen cost]. Participants offloaded between 39% and 46% of their body weight through the elbow support armrest while ambulating with the LW. Irrespective of the walker used, participants exerted ∼5%-6% of their body weight in gripping the walker handles during walking. CONCLUSIONS Using the forearm support-based LW led to upright body posture, offloaded portions of body weight from the lower extremity, and improved gait efficiency during ambulation in comparison to the SR and the participants' own PD. Further studies focusing on population-specific benefits are recommended.},
 bibtype = {article},
 author = {Jayaraman, Chandrasekaran and Mummidisetty, Chaithanya Krishna and Loesch, Alexandra and Kaur, Sandi and Hoppe-Ludwig, Shenan and Staat, Manfred and Jayaraman, Arun},
 doi = {10.1016/j.apmr.2018.10.001},
 journal = {Archives of Physical Medicine and Rehabilitation},
 number = {4}
}

OBJECTIVE To investigate the postural and metabolic benefits a walker with adjustable elbow support (LifeWalker [LW]) can provide for ambulation in population with impairment. The clinical outcomes from the elbow support walker will be compared with standard rollator (SR) and participants predicate device (PD). DESIGN Case-crossover study design. SETTING Clinical laboratory. PARTICIPANTS Individuals aged between 18 and 85 years using a rollator walker as primary mode of assistance and certified as medically stable by their primary physician. Participants (N=30; 80% women [n=24]) recruited from a convenient sample provided voluntary consent and completed the study. INTERVENTION Not applicable. MAIN OUTCOME MEASURES The trunk anterior-posterior (AP) sway (during the 10-meter walk test), oxygen consumption (during the 6-minute walk test), the mean forearm load offloaded to the elbow support as percentage of body weight, and mean peak hand grip load (during the 25-meter walk test) were measured. RESULTS Ambulating with a LW led to (1) reduced trunk sway in the AP direction [(ZLW vs PD= -2.34, P=.018); (ZLW vs SR= -3.461, P=.001)]; (2) reduced erector spinae muscle activation at the left lumbar L3 level [(ZLW vs PD= -2.71, P=.007); (ZLW vs SR= -1.71, P=.09)]; and (3) improved gait efficiency [(ZLW vs PD= -2.66, P=.008) Oxygen cost; (ZLW Vs. SR= -2.66, P=.008) Oxygen cost]. Participants offloaded between 39% and 46% of their body weight through the elbow support armrest while ambulating with the LW. Irrespective of the walker used, participants exerted ∼5%-6% of their body weight in gripping the walker handles during walking. CONCLUSIONS Using the forearm support-based LW led to upright body posture, offloaded portions of body weight from the lower extremity, and improved gait efficiency during ambulation in comparison to the SR and the participants' own PD. Further studies focusing on population-specific benefits are recommended.

@article{
 title = {Modeling and simulation of human induced pluripotent stem cell-derived cardiac tissue},
 type = {article},
 year = {2019},
 keywords = {electromechanical coupling,fibroblasts,hiPSC-derived cardiomyocytes,multi-scale computer model,pharmacology},
 pages = {e201900002},
 volume = {42},
 websites = {https://onlinelibrary.wiley.com/doi/full/10.1002/gamm.201900002,http://doi.wiley.com/10.1002/gamm.201900002},
 month = {11},
 day = {4},
 id = {74ebf553-590d-31d2-b77f-f6bbbfb1e79b},
 created = {2019-01-18T20:14:00.793Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:44:00.077Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2019},
 private_publication = {false},
 abstract = {Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have become a promising in vitro model for human native cardiomyocytes. Cultivated tissue samples beat autonomously and can be used for basic and pharmacological research. For mechanical measurements of these tissue samples, the CellDrum technology has been developed. Measurements are extended by simulations with a multi-scale electromechanically coupled FEM based model. This model can be parameterized and validated experimentally. The paper describes the model, its workflow, and preliminary simulations to study the effect of fibroblasts and a selected cardiac drug on the electromechanics of hiPSC-CMs.},
 bibtype = {article},
 author = {Jung, Alexander and Staat, Manfred},
 doi = {10.1002/gamm.201900002},
 journal = {GAMM-Mitteilungen},
 number = {4}
}

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have become a promising in vitro model for human native cardiomyocytes. Cultivated tissue samples beat autonomously and can be used for basic and pharmacological research. For mechanical measurements of these tissue samples, the CellDrum technology has been developed. Measurements are extended by simulations with a multi-scale electromechanically coupled FEM based model. This model can be parameterized and validated experimentally. The paper describes the model, its workflow, and preliminary simulations to study the effect of fibroblasts and a selected cardiac drug on the electromechanics of hiPSC-CMs.

@article{
 title = {A musculoskeletal shoulder simulation of moment arms and joint reaction forces after medialization of the supraspinatus footprint in rotator cuff repair.},
 type = {article},
 year = {2019},
 keywords = {Rotator cuff repair,attachment,medialization,moment arm,reinsertion,stability,supraspinatus},
 pages = {595-604},
 volume = {22},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/30835541,https://www.tandfonline.com/doi/full/10.1080/10255842.2019.1572749},
 month = {3},
 day = {5},
 id = {5a7d8577-2c71-3255-b9b4-f50df5bdb54c},
 created = {2019-02-04T20:09:28.249Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T14:28:22.880Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Leschinger2019},
 private_publication = {false},
 abstract = {A non-anatomical reinsertion of the supraspinatus medially to the original footprint to avoid over-tensioning of the tendon in large and retracted tears is one surgical option in rotator cuff (RC) repair. The purpose of the study was to determine the biomechanical effects on the glenohumeral joint with regard to this surgical technique. A modified musculoskeletal computational shoulder model was used to evaluate the change in moment arms and muscle forces of the RC and the co-contracting muscles and the alteration of the joint reaction forces (compressive and shear forces) after reinsertion of the supraspinatus 5 mm, 10 mm, 15 mm and 20 mm medially to the original footprint. A medialization of the supraspinatus reduces its moment arm in glenohumeral abduction. In case of a medialization of the attachment of 15 mm and 20 mm, the supraspinatus restricts glenohumeral abduction at 54° and 68°. In glenohumeral forward flexion and in lower degrees of internal rotation the moment arm of the supraspinatus increases for a medialized tendon attachment and decreases in external rotation in relation to the anatomical condition. A medialization of the supraspinatus insertion point yields in an increase in muscle force for abduction, internal and external rotation. In the present model a medially non-anatomic reinsertion reduces significantly the compressive glenohumeral joint reaction and the glenohumeral stability. Moreover, the results show that a medialization of the supraspinatus leads to a reduction of the supraspinatus moment arm especially in abduction. This leads to an increase of a compensatory supraspinatus load for stabilization the humerus in space, which may potentially cause a postoperative overload of the tendon-bone-complex.},
 bibtype = {article},
 author = {Leschinger, Tim and Birgel, Stefan and Hackl, Michael and Staat, Manfred and Müller, Lars Peter and Wegmann, Kilian},
 doi = {10.1080/10255842.2019.1572749},
 journal = {Computer Methods in Biomechanics and Biomedical Engineering},
 number = {6}
}

A non-anatomical reinsertion of the supraspinatus medially to the original footprint to avoid over-tensioning of the tendon in large and retracted tears is one surgical option in rotator cuff (RC) repair. The purpose of the study was to determine the biomechanical effects on the glenohumeral joint with regard to this surgical technique. A modified musculoskeletal computational shoulder model was used to evaluate the change in moment arms and muscle forces of the RC and the co-contracting muscles and the alteration of the joint reaction forces (compressive and shear forces) after reinsertion of the supraspinatus 5 mm, 10 mm, 15 mm and 20 mm medially to the original footprint. A medialization of the supraspinatus reduces its moment arm in glenohumeral abduction. In case of a medialization of the attachment of 15 mm and 20 mm, the supraspinatus restricts glenohumeral abduction at 54° and 68°. In glenohumeral forward flexion and in lower degrees of internal rotation the moment arm of the supraspinatus increases for a medialized tendon attachment and decreases in external rotation in relation to the anatomical condition. A medialization of the supraspinatus insertion point yields in an increase in muscle force for abduction, internal and external rotation. In the present model a medially non-anatomic reinsertion reduces significantly the compressive glenohumeral joint reaction and the glenohumeral stability. Moreover, the results show that a medialization of the supraspinatus leads to a reduction of the supraspinatus moment arm especially in abduction. This leads to an increase of a compensatory supraspinatus load for stabilization the humerus in space, which may potentially cause a postoperative overload of the tendon-bone-complex.

@article{
 title = {Optimization of the flight technique in ski jumping: The influence of wind},
 type = {article},
 year = {2019},
 keywords = {Computer simulation,Optimal control,Ski flying,Sport aerodynamics,Winter sports},
 pages = {190-193},
 volume = {88},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0021929019302015,http://www.ncbi.nlm.nih.gov/pubmed/30940358},
 month = {5},
 day = {22},
 id = {79f38305-dca6-338f-af0c-59fb90b8d437},
 created = {2019-02-13T19:29:48.917Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:44:00.059Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2019},
 private_publication = {false},
 abstract = {Ski jumping performance is strongly affected by wind. Flight technique optimization for maximizing jump length is a highly complex motor-control task that also depends on the wind. Pontryagin's minimum principle was used in this study to gain a better understanding on how wind influences flight technique optimization. Optimum time courses of the angle of attack α of the skis and of the body-to-ski angle β were computed for seven realistic wind scenarios on the large hill and on the flying hill. The optimum values of α were smaller at headwind, and larger at tailwind when compared to the optimum time course at calm wind. The optimum values of β were the smallest possible ones at the given flight technique constraints, except for the last part of the flight. Optimum adjustments of α increased the jump lengths between 0 and 1.8 m on the large hill, and between 0 and 6.4 m on the flying hill. Maximum jump length increases were achieved at the highest headwind speed. Even larger jump length effects can be achieved by using smaller β-angles, which might be possible in headwind conditions, but this is associated with increased problems to keep the flight stable.},
 bibtype = {article},
 author = {Jung, Alexander and Müller, Wolfram and Staat, Manfred},
 doi = {10.1016/j.jbiomech.2019.03.023},
 journal = {Journal of Biomechanics}
}

Ski jumping performance is strongly affected by wind. Flight technique optimization for maximizing jump length is a highly complex motor-control task that also depends on the wind. Pontryagin's minimum principle was used in this study to gain a better understanding on how wind influences flight technique optimization. Optimum time courses of the angle of attack α of the skis and of the body-to-ski angle β were computed for seven realistic wind scenarios on the large hill and on the flying hill. The optimum values of α were smaller at headwind, and larger at tailwind when compared to the optimum time course at calm wind. The optimum values of β were the smallest possible ones at the given flight technique constraints, except for the last part of the flight. Optimum adjustments of α increased the jump lengths between 0 and 1.8 m on the large hill, and between 0 and 6.4 m on the flying hill. Maximum jump length increases were achieved at the highest headwind speed. Even larger jump length effects can be achieved by using smaller β-angles, which might be possible in headwind conditions, but this is associated with increased problems to keep the flight stable.

@misc{
 title = {Biaxiales Materialprüfsystem und Verfahren zu dessen Anwendung [Biaxial material testing system and use thereof]},
 type = {misc},
 year = {2019},
 pages = {15},
 websites = {https://register.dpma.de/DPMAregister/pat/PatSchrifteneinsicht?docId=DE102017116067A1,https://worldwide.espacenet.com/publicationDetails/biblio?FT=D&date=20190117&DB=&locale=&CC=DE&NR=102017116067A1#,http://www.freepatentsonline.com/DE102017116067.html},
 publisher = {Deutsches Patent- und Markenamt},
 institution = {Fachhochschule Aachen},
 revision = {DE 10 2017 116 067},
 id = {fd8db9ef-48c7-3e36-b6a2-de3ddd1d8da9},
 created = {2019-04-19T13:09:23.046Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-10-01T13:33:53.510Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2019},
 country = {Germany},
 patent_owner = {Bonnekamp & Sparing},
 private_publication = {false},
 abstract = {System und Verfahren zur Durchführung von Messungen biaxialer und kreuzförmiger Zugversuche, wobei ein Weg oder eine Kraft auf eine Materialprobe über mindestens zwei Nadelarme mit Nadeln geleitet wird, die in einem Gehäuse gelagert sind, wobei die Arme und/oder Nadelarme für eine ungehinderte Querkontraktion bei gleichmäßiger Lasteinleitung um eine Achse drehbar gelagert und seitlich auslenkbar sind. [System and method for carrying out measurements of biaxial and cross-shaped tensile tests, wherein a path or a force is directed onto a material sample via at least two needle arms with needles which are mounted in a housing, wherein the arms and/or needle arms are mounted rotatably about an axis for unconstrained transverse contraction with uniform load application and can be deflected laterally. ]},
 bibtype = {misc},
 author = {Staat, Manfred and Horbach, Andreas J. and Gatzweiler, Karl-Heinz}
}

System und Verfahren zur Durchführung von Messungen biaxialer und kreuzförmiger Zugversuche, wobei ein Weg oder eine Kraft auf eine Materialprobe über mindestens zwei Nadelarme mit Nadeln geleitet wird, die in einem Gehäuse gelagert sind, wobei die Arme und/oder Nadelarme für eine ungehinderte Querkontraktion bei gleichmäßiger Lasteinleitung um eine Achse drehbar gelagert und seitlich auslenkbar sind. [System and method for carrying out measurements of biaxial and cross-shaped tensile tests, wherein a path or a force is directed onto a material sample via at least two needle arms with needles which are mounted in a housing, wherein the arms and/or needle arms are mounted rotatably about an axis for unconstrained transverse contraction with uniform load application and can be deflected laterally. ]

@article{
 title = {Kyphoplasty of osteoporotic fractured vertebrae: A finite element analysis about two types of cement.},
 type = {article},
 year = {2019},
 pages = {9232813},
 volume = {2019},
 websites = {https://www.hindawi.com/journals/bmri/2019/9232813/,http://www.ncbi.nlm.nih.gov/pubmed/31143778,http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC6501275},
 month = {4},
 day = {22},
 id = {e38566f1-c2ad-3352-84fe-f4ccdb530be1},
 created = {2019-04-21T20:21:55.084Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T14:28:22.879Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Meyer2019},
 private_publication = {false},
 abstract = {If conservative treatment of osteoporotic vertebral compression fractures fails, vertebro- or kyphoplasty is indicated. Usually, polymethylmethacrylate cement (PMMA) is applied coming along with many disadvantageous features. Aluminum-free glass-polyalkenoate cement (GPC) appears to be a benefit alternative material. This study aimed at comparing the mean stress values in human vertebrae after kyphoplasty with PMMA and GPC (IlluminOss™) at hand of a finite element analysis. Three models were created performing kyphoplasty using PMMA or IlluminOss™, respectively, at two native, human lumbar vertebrae (L4) while one remains intact. Finite element analysis was performed using CT-scans of every vertebra. Moreover the PMMA-treated vertebra was used as a model as analyses were executed using material data of PMMA and of GPC. The unimpaired, spongious bone showed potentials of 0.25 MPa maximally. After augmentation stress levels showed fivefold increase, rising from externally to internally, revealing stress peaks at the ventral border of the spinal canal. At central areas of cement 1 MPa is measured in both types of cement. Around these central areas the von Mises stress decreased about 25-50% (0.5-0.75 MPa). If workload of 500 N was applied, the stress appeared to be more centralized at the IlluminOss™-model, similar to the unimpaired. Considering the endplates the GPC model also closely resembles the unimpaired. Comparing the PMMA-treated vertebral body and the GPC-simulation, there is an obvious difference. While the PMMA-treated model showed a central stress peak of 5 MPa, the GPC-simulation of the same vertebral body presents lower stress of 1.2-2.5 MPa. Finite element analysis showed that IlluminOss™ (GPC), used in kyphoplasty of vertebral bodies, creates lower level stress and strain compared to standardly used PMMA, leading to lower stress concentrations on the cranial and caudal vertebral surface especially. GPC appears to own advantageous biological and clinical relevant features.},
 bibtype = {article},
 author = {Meyer, Carolin and van Gaalen, Kerstin and Leschinger, Tim and Scheyerer, Max J. and Neiss, Wolfram F. and Staat, Manfred and Müller, Lars Peter and Wegmann, Kilian},
 doi = {10.1155/2019/9232813},
 journal = {BioMed Research Iternational}
}

If conservative treatment of osteoporotic vertebral compression fractures fails, vertebro- or kyphoplasty is indicated. Usually, polymethylmethacrylate cement (PMMA) is applied coming along with many disadvantageous features. Aluminum-free glass-polyalkenoate cement (GPC) appears to be a benefit alternative material. This study aimed at comparing the mean stress values in human vertebrae after kyphoplasty with PMMA and GPC (IlluminOss™) at hand of a finite element analysis. Three models were created performing kyphoplasty using PMMA or IlluminOss™, respectively, at two native, human lumbar vertebrae (L4) while one remains intact. Finite element analysis was performed using CT-scans of every vertebra. Moreover the PMMA-treated vertebra was used as a model as analyses were executed using material data of PMMA and of GPC. The unimpaired, spongious bone showed potentials of 0.25 MPa maximally. After augmentation stress levels showed fivefold increase, rising from externally to internally, revealing stress peaks at the ventral border of the spinal canal. At central areas of cement 1 MPa is measured in both types of cement. Around these central areas the von Mises stress decreased about 25-50% (0.5-0.75 MPa). If workload of 500 N was applied, the stress appeared to be more centralized at the IlluminOss™-model, similar to the unimpaired. Considering the endplates the GPC model also closely resembles the unimpaired. Comparing the PMMA-treated vertebral body and the GPC-simulation, there is an obvious difference. While the PMMA-treated model showed a central stress peak of 5 MPa, the GPC-simulation of the same vertebral body presents lower stress of 1.2-2.5 MPa. Finite element analysis showed that IlluminOss™ (GPC), used in kyphoplasty of vertebral bodies, creates lower level stress and strain compared to standardly used PMMA, leading to lower stress concentrations on the cranial and caudal vertebral surface especially. GPC appears to own advantageous biological and clinical relevant features.

@book{
 title = {Proceedings of 3rd YRA MedTech Symposium, Young Researchers Academy - MedTech in NRW},
 type = {book},
 year = {2019},
 pages = {52},
 websites = {http://yra-medtech.de/daten_medtech/dokumente2019/YRA_2019_PROC_low.pdf},
 publisher = {University Duisburg-Essen},
 city = {Jülich, Germany},
 id = {dc27bcb9-dc79-3b16-a374-2e5d9320db07},
 created = {2019-05-15T20:22:26.641Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.289Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2019},
 private_publication = {false},
 bibtype = {book},
 author = {},
 editor = {Staat, Manfred and Erni, Daniel},
 doi = {10.17185/duepublico/48750}
}

@inproceedings{
 title = {Development of a tool to analyse the conduction speed in multi electrode array measurements of cardiac tissue},
 type = {inproceedings},
 year = {2019},
 pages = {7-8},
 websites = {http://yra-medtech.de/daten_medtech/dokumente2019/YRA_2019_PROC.pdf},
 publisher = {University Duisburg-Essen},
 city = {Jülich, Germany},
 id = {8436ef14-dc27-3e59-9ef9-d105034a1ed1},
 created = {2019-05-18T20:43:50.028Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.088Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hunker2019},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Hunker, Jan and Jung, Alexander and Goßmann, Matthias and Linder, Peter and Staat, Manfred},
 editor = {Staat, Manfred and Erni, Daniel},
 doi = {10.17185/duepublico/48750},
 booktitle = {3rd YRA MedTech Symposium, Young Researchers Academy - MedTech in NRW}
}

@inproceedings{
 title = {Modification of a computer model of human stem cell-derived cardiomyocyte electrophysiology based on patch-clamp measurements},
 type = {inproceedings},
 year = {2019},
 pages = {10-11},
 websites = {http://yra-medtech.de/daten_medtech/dokumente2019/YRA_2019_PROC.pdf},
 publisher = {University Duisburg-Essen},
 city = {Jülich, Germany},
 id = {8b577258-0b1a-3e44-8525-c6cabe549fa2},
 created = {2019-05-18T20:43:50.122Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.505Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Raman2019},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Raman, Aravind Hariharan and Jung, Alexander and Horváth, András and Becker, Nadine and Staat, Manfred},
 editor = {Staat, Manfred and Erni, Daniel},
 doi = {10.17185/duepublico/48750},
 booktitle = {3rd YRA MedTech Symposium, Young Researchers Academy - MedTech in NRW}
}

@article{
 title = {Irreparable rotator cuff tears: a biomechanical comparison of superior capsuloligamentous complex reconstruction techniques and an interpositional graft technique},
 type = {article},
 year = {2019},
 keywords = {biomechanics,capsule reconstruction,interposition,irreparable rotator cuff tears,superior glenohumeral stability},
 pages = {2325967119864590},
 volume = {7},
 websites = {http://journals.sagepub.com/doi/10.1177/2325967119864590,http://www.ncbi.nlm.nih.gov/pubmed/31489328,http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC6709439},
 month = {8},
 day = {22},
 id = {f7201c5a-87b9-3bcc-957c-ff139dcfd1ee},
 created = {2019-08-22T22:10:47.480Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T14:28:22.939Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Leschinger2019},
 private_publication = {false},
 abstract = {Background Irreparable rotator cuff tears lead to superior translation of the humeral head. Numerous surgical management options are available to treat the condition. Purpose To compare superior capsule stability among different types of patch grafting in irreparable rotator cuff tears. Methods Six cadaveric shoulders were tested in a custom-designed shoulder testing system. Superior translation of the humerus and subacromial contact pressure were quantified in an intact condition (condition 1), after cutting the supraspinatus tendon (condition 2), and after additionally cutting the superior capsuloligamentous complex (condition 3). The results were compared among 3 types of patch grafting, in which capsule reconstruction was achieved by glenoidal 3-point (condition 4) or 2-point (condition 5) fixation or by affixing a graft below the acromion (condition 6). Results No significant difference in subacromial pressure was measured by reconstruction with 2 or 3 anchors compared with conditions 1 and 2 (P > .05). However, with 3-point fixation, lower levels of pressure were measured than with 2-point fixation. Moreover, superior translation values were lower with 3-point fixation; the same applied for values of the preserved capsule as compared with the torn capsule. In condition 6, a significant increase in pressure in the neutral position was documented (P < .05). Conclusion The superior capsuloligamentous complex plays an important role in stabilizing the glenohumeral joint. The results suggest that with additional medial anchoring at the coracoid base, the depressing and centering effect of the superior complex can probably be regained in a more physiological way compared with a reconstructed capsule with 2 glenoid attachments or with an interpositional graft below the acromion.},
 bibtype = {article},
 author = {Leschinger, Tim and Besch, Katharina and Aydin, Cansu and Staat, Manfred and Scaal, Martin and Müller, Lars Peter and Wegmann, Kilian},
 doi = {10.1177/2325967119864590},
 journal = {Orthopaedic Journal of Sports Medicine},
 number = {8}
}

Background Irreparable rotator cuff tears lead to superior translation of the humeral head. Numerous surgical management options are available to treat the condition. Purpose To compare superior capsule stability among different types of patch grafting in irreparable rotator cuff tears. Methods Six cadaveric shoulders were tested in a custom-designed shoulder testing system. Superior translation of the humerus and subacromial contact pressure were quantified in an intact condition (condition 1), after cutting the supraspinatus tendon (condition 2), and after additionally cutting the superior capsuloligamentous complex (condition 3). The results were compared among 3 types of patch grafting, in which capsule reconstruction was achieved by glenoidal 3-point (condition 4) or 2-point (condition 5) fixation or by affixing a graft below the acromion (condition 6). Results No significant difference in subacromial pressure was measured by reconstruction with 2 or 3 anchors compared with conditions 1 and 2 (P > .05). However, with 3-point fixation, lower levels of pressure were measured than with 2-point fixation. Moreover, superior translation values were lower with 3-point fixation; the same applied for values of the preserved capsule as compared with the torn capsule. In condition 6, a significant increase in pressure in the neutral position was documented (P < .05). Conclusion The superior capsuloligamentous complex plays an important role in stabilizing the glenohumeral joint. The results suggest that with additional medial anchoring at the coracoid base, the depressing and centering effect of the superior complex can probably be regained in a more physiological way compared with a reconstructed capsule with 2 glenoid attachments or with an interpositional graft below the acromion.

@article{
 title = {Comparison of forces acting on maxillary incisors during tracheal intubation with different laryngoscopy techniques: a blinded manikin study.},
 type = {article},
 year = {2019},
 keywords = {anaesthetic complications,dental trauma,force,injuries,intubation,videolaryngoscopy},
 pages = {1563-1571},
 volume = {74},
 websites = {https://onlinelibrary.wiley.com/doi/abs/10.1111/anae.14815,http://www.ncbi.nlm.nih.gov/pubmed/31448404},
 day = {1},
 id = {395100c3-226e-3efc-bccc-d34afb5b8f4a},
 created = {2019-08-26T08:04:35.470Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-02-14T14:52:46.924Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Schieren2019},
 private_publication = {false},
 abstract = {Dental trauma is a common complication of tracheal intubation. As existing evidence is insufficient to validly assess the impact of different laryngoscopy techniques on the incidence of dental trauma, the force exerted onto dental structures during tracheal intubation was investigated. An intubation manikin was equipped with hidden force sensors in all maxillary incisors. Dental force was measured while 104 anaesthetists performed a series of tracheal intubations using direct laryngoscopy with a Macintosh blade, and videolaryngoscopy with a C-MAC® , or the hyperangulated GlideScope® or KingVision® laryngoscopes in both normal and difficult airway conditions. A total of 624 tracheal intubations were analysed. The median (IQR [range]) peak force of direct laryngoscopy in normal airways was 21.1 (14.0-32.8 [2.3-127.6]) N and 29.3 (17.7-44.8 [3.3-97.2]) N in difficult airways. In normal airways, these were lower with the GlideScope and KingVision hyperangulated laryngoscopes, with a reduction of 4.6 N (p = 0.006) and 10.9 N (p < 0.001) compared with direct laryngoscopy, respectively. In difficult airways, these were lower with the GlideScope and KingVision hyperangulated laryngoscopes, with a reduction of 9.8 N (p < 0.001) and 17.6 N (p < 0.001) compared with direct laryngoscopy, respectively. The use of the C-MAC did not have an impact on the median peak force. Although sex of anaesthetists did not affect peak force, more experienced anaesthetists generated a higher peak force than less experienced providers. We conclude that hyperangulated videolaryngoscopy was associated with a significantly decreased force exerted on maxillary incisors and might reduce the risk for dental injury in clinical settings.},
 bibtype = {article},
 author = {Schieren, Mark and Kleinschmidt, Joris and Schmutz, Axel and Loop, Torsten and Staat, Manfred and Gatzweiler, K-H and Wappler, Frank and Defosse, Jérôme},
 doi = {10.1111/anae.14815},
 journal = {Anaesthesia},
 number = {12}
}

Dental trauma is a common complication of tracheal intubation. As existing evidence is insufficient to validly assess the impact of different laryngoscopy techniques on the incidence of dental trauma, the force exerted onto dental structures during tracheal intubation was investigated. An intubation manikin was equipped with hidden force sensors in all maxillary incisors. Dental force was measured while 104 anaesthetists performed a series of tracheal intubations using direct laryngoscopy with a Macintosh blade, and videolaryngoscopy with a C-MAC® , or the hyperangulated GlideScope® or KingVision® laryngoscopes in both normal and difficult airway conditions. A total of 624 tracheal intubations were analysed. The median (IQR [range]) peak force of direct laryngoscopy in normal airways was 21.1 (14.0-32.8 [2.3-127.6]) N and 29.3 (17.7-44.8 [3.3-97.2]) N in difficult airways. In normal airways, these were lower with the GlideScope and KingVision hyperangulated laryngoscopes, with a reduction of 4.6 N (p = 0.006) and 10.9 N (p < 0.001) compared with direct laryngoscopy, respectively. In difficult airways, these were lower with the GlideScope and KingVision hyperangulated laryngoscopes, with a reduction of 9.8 N (p < 0.001) and 17.6 N (p < 0.001) compared with direct laryngoscopy, respectively. The use of the C-MAC did not have an impact on the median peak force. Although sex of anaesthetists did not affect peak force, more experienced anaesthetists generated a higher peak force than less experienced providers. We conclude that hyperangulated videolaryngoscopy was associated with a significantly decreased force exerted on maxillary incisors and might reduce the risk for dental injury in clinical settings.

@article{
 title = {A new in vitro tool to investigate cardiac contractility under physiological mechanical conditions},
 type = {article},
 year = {2019},
 pages = {106595},
 volume = {99},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S1056871919302758,http://www.ncbi.nlm.nih.gov/pubmed/31962939},
 month = {9},
 id = {b27a5cce-7be7-32d5-ac13-5859cd1bd895},
 created = {2019-10-21T08:36:03.379Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:44:00.031Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Linder2018},
 private_publication = {false},
 bibtype = {article},
 author = {Linder, Peter and Beckler, Matthias and Doerr, Leo and Stoelzle-Feix, Sonja and Fertig, Niels and Jung, Alexander and Staat, Manfred and Gossmann, Matthias},
 doi = {10.1016/j.vascn.2019.05.162},
 journal = {Journal of Pharmacological and Toxicological Methods}
}

@article{
 title = {Porosity and tissue integration of elastic mesh implants evaluated in vitro and in vivo},
 type = {article},
 year = {2018},
 keywords = {Digital image correlation (DIC),Elastic mesh implant,Porosity,Tensile tests,Thermoplastic polyurethane (TPU),Tissue integration},
 pages = {827-833},
 volume = {106},
 websites = {http://doi.wiley.com/10.1002/jbm.b.33877},
 month = {2},
 id = {bbdb07ec-e550-3a8a-8f4b-0c82f1eaa89d},
 created = {2017-11-28T03:43:56.970Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:46:59.790Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Ciritsis2018},
 private_publication = {false},
 abstract = {© 2017 Wiley Periodicals, Inc. Purpose: In vivo, a loss of mesh porosity triggers scar tissue formation and restricts functionality. The purpose of this study was to evaluate the properties and configuration changes as mesh deformation and mesh shrinkage of a soft mesh implant compared with a conventional stiff mesh implant in vitro and in a porcine model. Material and Methods: Tensile tests and digital image correlation were used to determine the textile porosity for both mesh types in vitro. A group of three pigs each were treated with magnetic resonance imaging (MRI) visible conventional stiff polyvinylidene fluoride meshes (PVDF) or with soft thermoplastic polyurethane meshes (TPU) (FEG Textiltechnik mbH, Aachen, Germany), respectively. MRI was performed with a pneumoperitoneum at a pressure of 0 and 15 mmHg, which resulted in bulging of the abdomen. The mesh-induced signal voids were semiautomatically segmented and the mesh areas were determined. With the deformations assessed in both mesh types at both pressure conditions, the porosity change of the meshes after 8 weeks of ingrowth was calculated as an indicator of preserved elastic properties. The explanted specimens were examined histologically for the maturity of the scar (collagen I/III ratio). Results: In TPU, the in vitro porosity increased constantly, in PVDF, a loss of porosity was observed under mild stresses. In vivo, the mean mesh areas of TPU were 206.8 cm 2 (± 5.7 cm 2 ) at 0 mmHg pneumoperitoneum and 274.6 cm 2 (± 5.2 cm 2 ) at 15 mmHg; for PVDF the mean areas were 205.5 cm 2 (± 8.8 cm 2 ) and 221.5 cm 2 (± 11.8 cm 2 ), respectively. The pneumoperitoneum-induced pressure increase resulted in a calculated porosity increase of 8.4% for TPU and of 1.2% for PVDF. The mean collagen I/III ratio was 8.7 (± 0.5) for TPU and 4.7 (± 0.7) for PVDF. Conclusion: The elastic properties of TPU mesh implants result in improved tissue integration compared to conventional PVDF meshes, and they adapt more efficiently to the abdominal wall.},
 bibtype = {article},
 author = {Ciritsis, Alexander and Horbach, Andreas and Staat, Manfred and Kuhl, Christiane K. and Kraemer, Nils Andreas},
 doi = {10.1002/jbm.b.33877},
 journal = {Journal of Biomedical Materials Research Part B: Applied Biomaterials},
 number = {2}
}

© 2017 Wiley Periodicals, Inc. Purpose: In vivo, a loss of mesh porosity triggers scar tissue formation and restricts functionality. The purpose of this study was to evaluate the properties and configuration changes as mesh deformation and mesh shrinkage of a soft mesh implant compared with a conventional stiff mesh implant in vitro and in a porcine model. Material and Methods: Tensile tests and digital image correlation were used to determine the textile porosity for both mesh types in vitro. A group of three pigs each were treated with magnetic resonance imaging (MRI) visible conventional stiff polyvinylidene fluoride meshes (PVDF) or with soft thermoplastic polyurethane meshes (TPU) (FEG Textiltechnik mbH, Aachen, Germany), respectively. MRI was performed with a pneumoperitoneum at a pressure of 0 and 15 mmHg, which resulted in bulging of the abdomen. The mesh-induced signal voids were semiautomatically segmented and the mesh areas were determined. With the deformations assessed in both mesh types at both pressure conditions, the porosity change of the meshes after 8 weeks of ingrowth was calculated as an indicator of preserved elastic properties. The explanted specimens were examined histologically for the maturity of the scar (collagen I/III ratio). Results: In TPU, the in vitro porosity increased constantly, in PVDF, a loss of porosity was observed under mild stresses. In vivo, the mean mesh areas of TPU were 206.8 cm 2 (± 5.7 cm 2 ) at 0 mmHg pneumoperitoneum and 274.6 cm 2 (± 5.2 cm 2 ) at 15 mmHg; for PVDF the mean areas were 205.5 cm 2 (± 8.8 cm 2 ) and 221.5 cm 2 (± 11.8 cm 2 ), respectively. The pneumoperitoneum-induced pressure increase resulted in a calculated porosity increase of 8.4% for TPU and of 1.2% for PVDF. The mean collagen I/III ratio was 8.7 (± 0.5) for TPU and 4.7 (± 0.7) for PVDF. Conclusion: The elastic properties of TPU mesh implants result in improved tissue integration compared to conventional PVDF meshes, and they adapt more efficiently to the abdominal wall.

@article{
 title = {Modelling of soft connective tissues to investigate female pelvic floor dysfunctions.},
 type = {article},
 year = {2018},
 pages = {9518076},
 volume = {2018},
 websites = {https://www.hindawi.com/journals/cmmm/2018/9518076/,http://www.ncbi.nlm.nih.gov/pubmed/29568322,http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC5820624},
 id = {1a2eeead-e427-3ac5-ad55-f9287b1744d2},
 created = {2018-01-16T21:23:52.661Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-06-30T14:13:13.150Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2018c},
 private_publication = {false},
 abstract = {After menopause, decreased levels of estrogen and progesterone remodel the collagen of the soft tissues thereby reducing their stiffness. Stress urinary incontinence is associated with involuntary urine leakage due to pathological movement of the pelvic organs resulting from lax suspension system, fasciae, and ligaments. This study compares the changes in the orientation and position of the female pelvic organs due to weakened fasciae, ligaments, and their combined laxity. A mixture theory weighted by respective volume fraction of elastin-collagen fibre compound (5%), adipose tissue (85%), and smooth muscle (5%) is adopted to characterize the mechanical behaviour of the fascia. The load carrying response (other than the functional response to the pelvic organs) of each fascia component, pelvic organs, muscles, and ligaments are assumed to be isotropic, hyperelastic, and incompressible. Finite element simulations are conducted during Valsalva manoeuvre with weakened tissues modelled by reduced tissue stiffness. A significant dislocation of the urethrovesical junction is observed due to weakness of the fascia (13.89 mm) compared to the ligaments (5.47 mm). The dynamics of the pelvic floor observed in this study during Valsalva manoeuvre is associated with urethral-bladder hypermobility, greater levator plate angulation, and positive Q-tip test which are observed in incontinent females.},
 bibtype = {article},
 author = {Bhattarai, Aroj and Staat, Manfred},
 doi = {10.1155/2018/9518076},
 journal = {Computational and Mathematical Methods in Medicine}
}

After menopause, decreased levels of estrogen and progesterone remodel the collagen of the soft tissues thereby reducing their stiffness. Stress urinary incontinence is associated with involuntary urine leakage due to pathological movement of the pelvic organs resulting from lax suspension system, fasciae, and ligaments. This study compares the changes in the orientation and position of the female pelvic organs due to weakened fasciae, ligaments, and their combined laxity. A mixture theory weighted by respective volume fraction of elastin-collagen fibre compound (5%), adipose tissue (85%), and smooth muscle (5%) is adopted to characterize the mechanical behaviour of the fascia. The load carrying response (other than the functional response to the pelvic organs) of each fascia component, pelvic organs, muscles, and ligaments are assumed to be isotropic, hyperelastic, and incompressible. Finite element simulations are conducted during Valsalva manoeuvre with weakened tissues modelled by reduced tissue stiffness. A significant dislocation of the urethrovesical junction is observed due to weakness of the fascia (13.89 mm) compared to the ligaments (5.47 mm). The dynamics of the pelvic floor observed in this study during Valsalva manoeuvre is associated with urethral-bladder hypermobility, greater levator plate angulation, and positive Q-tip test which are observed in incontinent females.

@article{
 title = {Pathogenese, funktionelle und anatomische Aspekte der weiblichen Belastungsinkontinenz [Female stress incontinence: aspects of pathogenesis and functional anatomy].},
 type = {article},
 year = {2018},
 pages = {47-51},
 volume = {49},
 websites = {http://www.thieme-connect.de/DOI/DOI?10.1055/s-0043-120616,http://www.ncbi.nlm.nih.gov/pubmed/29390217},
 month = {2},
 day = {1},
 id = {cb148826-5b3d-3f90-966c-5ce443520f1d},
 created = {2018-02-02T21:29:41.631Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-06-08T10:52:21.884Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Kohler2018},
 private_publication = {false},
 abstract = {This article focuses on female stress incontinence in the form of pelvic floor dysfunction and urethral sphincter deficiency, although isolated stress incontinence accounts for less than half of all incontinence cases. Especially in women of old age and those with neurological comorbidities, the causes of incontinence are mostly multifactorial. Also it has to be considered that the female bladder, urethra, uterus and rectum as well as the muscular and ligamentous structures of the female pelvis minor are affected by phases of fertility, possible pregnancies, births and menopause in addition to the normal ageing process. Der vorliegende Artikel fokussiert sich auf die weibliche Belastungsinkontinenz als Insuffizienz der Speicherfunktion der Blase, auch wenn im klinischen Alltag die Harninkontinenz der Frau häufig verschiedene Ursachen hat und insbesondere eine Belastungsinkontinenz im Alter und bei neurologischer Komorbidität nur selten isoliert vorkommt.Das kleine Becken der Frau ist sowohl als Funktions- als auch als strukturelle Einheit zu betrachten. Dabei unterliegen bei der Frau Blase, Harnröhre, Gebärmutter und Enddarm sowie die muskulären und ligamentösen Strukturen des kleinen Beckens durch Fertilitätsphase, mögliche Schwangerschaften, Geburten und Menopausen-Phase, über das „normale Altern“ hinaus, gravierenden Veränderungen.},
 bibtype = {article},
 author = {Kohler, Annette and Kirschner-Hermanns, Ruth and Staat, Manfred and Brehmer, Bernhard},
 doi = {10.1055/s-0043-120616},
 journal = {Aktuelle Urologie},
 number = {1}
}

This article focuses on female stress incontinence in the form of pelvic floor dysfunction and urethral sphincter deficiency, although isolated stress incontinence accounts for less than half of all incontinence cases. Especially in women of old age and those with neurological comorbidities, the causes of incontinence are mostly multifactorial. Also it has to be considered that the female bladder, urethra, uterus and rectum as well as the muscular and ligamentous structures of the female pelvis minor are affected by phases of fertility, possible pregnancies, births and menopause in addition to the normal ageing process. Der vorliegende Artikel fokussiert sich auf die weibliche Belastungsinkontinenz als Insuffizienz der Speicherfunktion der Blase, auch wenn im klinischen Alltag die Harninkontinenz der Frau häufig verschiedene Ursachen hat und insbesondere eine Belastungsinkontinenz im Alter und bei neurologischer Komorbidität nur selten isoliert vorkommt.Das kleine Becken der Frau ist sowohl als Funktions- als auch als strukturelle Einheit zu betrachten. Dabei unterliegen bei der Frau Blase, Harnröhre, Gebärmutter und Enddarm sowie die muskulären und ligamentösen Strukturen des kleinen Beckens durch Fertilitätsphase, mögliche Schwangerschaften, Geburten und Menopausen-Phase, über das „normale Altern“ hinaus, gravierenden Veränderungen.

@inbook{
 type = {inbook},
 year = {2018},
 keywords = {Muscle fibers,Passive stretching,Pelvic floor dysfunction,Pelvic muscle},
 pages = {217-230},
 volume = {29},
 websites = {http://link.springer.com/10.1007/978-3-319-71574-2_17},
 publisher = {Springer International Publishing},
 chapter = {Computational analysis of pelvic floor dysfunction},
 id = {dde3a0dc-8fb8-3951-99d9-3e21d8d7f3ff},
 created = {2018-02-06T23:04:02.277Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:46:59.942Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2018b},
 private_publication = {false},
 abstract = {© 2018, Springer International Publishing AG. Pelvic floor dysfunction (PFD) is characterized by the failure of the levator ani (LA) muscle to maintain the pelvic hiatus, resulting in the descent of the pelvic organs below the pubococcygeal line. This chapter adopts the modified Humphrey material model to consider the effect of the muscle fiber on passive stretching of the LA muscle. The deformation of the LA muscle subjected to intra-abdominal pressure during Valsalva maneuver is compared with the magnetic resonance imaging (MRI) examination of a nulliparous female. Numerical result shows that the fiber-based Humphrey model simulates the muscle behavior better than isotropic constitutive models. Greater posterior movement of the LA muscle widens the levator hiatus due to lack of support from the anococcygeal ligament and the perineal structure as a consequence of birth-related injury and aging. Old and multiparous females with uncontrolled urogenital and rectal hiatus tend to develop PFDs such as prolapse and incontinence.},
 bibtype = {inbook},
 author = {Bhattarai, Aroj and Frotscher, Ralf and Staat, Manfred},
 editor = {Brandão, Sofia and Roza, Thuane Da and Ramos, Isabel and Mascarenhas, Teresa},
 doi = {10.1007/978-3-319-71574-2_17},
 title = {Women’s Health and Biomechanics: Where Medicine and Engineering Meet. Lecture Notes in Computational Vision and Biomechanics}
}

© 2018, Springer International Publishing AG. Pelvic floor dysfunction (PFD) is characterized by the failure of the levator ani (LA) muscle to maintain the pelvic hiatus, resulting in the descent of the pelvic organs below the pubococcygeal line. This chapter adopts the modified Humphrey material model to consider the effect of the muscle fiber on passive stretching of the LA muscle. The deformation of the LA muscle subjected to intra-abdominal pressure during Valsalva maneuver is compared with the magnetic resonance imaging (MRI) examination of a nulliparous female. Numerical result shows that the fiber-based Humphrey model simulates the muscle behavior better than isotropic constitutive models. Greater posterior movement of the LA muscle widens the levator hiatus due to lack of support from the anococcygeal ligament and the perineal structure as a consequence of birth-related injury and aging. Old and multiparous females with uncontrolled urogenital and rectal hiatus tend to develop PFDs such as prolapse and incontinence.

@article{
 title = {Calculation of muscle forces and joint reaction loads in the shoulder area via an OpenSim based computer model},
 type = {article},
 year = {2018},
 pages = {321-330},
 volume = {85},
 websites = {http://www.degruyter.com/view/j/teme.ahead-of-print/teme-2017-0114/teme-2017-0114.xml,http://www.degruyter.com/view/j/teme.2018.85.issue-5/teme-2017-0114/teme-2017-0114.xml},
 month = {4},
 day = {25},
 id = {88fc0296-e697-3dea-9938-a3de730388cd},
 created = {2018-02-16T20:33:49.939Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-06-08T10:52:21.806Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Birgel2018},
 private_publication = {false},
 abstract = {Using the OpenSim software and verified anatomical data, a computer model for the calculation of biomechanical parameters is developed and used to determine the effect of a reattachment of the Supraspinatus muscle with a medial displacement of the muscle attachment point, which may be necessary for a rupture of the supraspinatus tendon. The results include the influence of the operation on basic biomechanical parameters such as the lever arm, as well as the calculated the muscle activations for the supraspinatus and deltoid. In addition, the influence on joint stability is examined by an analysis of the joint reaction force. The study provides a detailed description of the used model, as well as medical findings to a reattachment of the supraspinatus.},
 bibtype = {article},
 author = {Birgel, Stefan and Leschinger, Tim and Wegmann, Kilian and Staat, Manfred},
 doi = {10.1515/teme-2017-0114},
 journal = {tm - Technisches Messen},
 number = {5}
}

Using the OpenSim software and verified anatomical data, a computer model for the calculation of biomechanical parameters is developed and used to determine the effect of a reattachment of the Supraspinatus muscle with a medial displacement of the muscle attachment point, which may be necessary for a rupture of the supraspinatus tendon. The results include the influence of the operation on basic biomechanical parameters such as the lever arm, as well as the calculated the muscle activations for the supraspinatus and deltoid. In addition, the influence on joint stability is examined by an analysis of the joint reaction force. The study provides a detailed description of the used model, as well as medical findings to a reattachment of the supraspinatus.

@article{
 title = {Corrigendum to "Flight style optimization in ski jumping on normal, large, and ski flying hills" [J. Biomech 47 (2014) 716-722].},
 type = {article},
 year = {2018},
 pages = {313},
 volume = {71},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0021929018300617,http://www.ncbi.nlm.nih.gov/pubmed/29456170},
 month = {4},
 day = {11},
 id = {176151ae-0ee9-3c5c-9830-7d597ac97a1a},
 created = {2018-02-28T19:34:26.103Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T14:53:06.662Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2018b},
 private_publication = {false},
 bibtype = {article},
 author = {Jung, Alexander and Staat, Manfred and Müller, Wolfram},
 doi = {10.1016/j.jbiomech.2018.02.001},
 journal = {Journal of Biomechanics}
}

@article{
 title = {Surgical treatment of vaginal vault prolapse using different prosthetic mesh implants: a finite element analysis},
 type = {article},
 year = {2018},
 keywords = {Apical prolapse,biomechanical modeling,finite element simulation,prosthetic mesh implants,sacrocolpopexy,vaginal cuff},
 pages = {331-342},
 volume = {85},
 websites = {http://www.degruyter.com/view/j/teme.ahead-of-print/teme-2017-0115/teme-2017-0115.xml,http://www.degruyter.com/view/j/teme.2018.85.issue-5/teme-2017-0115/teme-2017-0115.xml},
 month = {4},
 day = {25},
 id = {e1953a25-0f0d-35b4-a58d-822fff836e97},
 created = {2018-04-01T19:28:33.558Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-06-08T10:52:22.274Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2018a},
 private_publication = {false},
 abstract = {Particularly multiparous elderly women may suffer from vaginal vault prolapse after hysterectomy due to weak support from lax apical ligaments. A decreased amount of estrogen and progesterone in older age is assumed to remodel the collagen thereby reducing tissue stiffness. Sacrocolpopexy is either performed as open or laparoscopic surgery using prosthetic mesh implants to substitute lax ligaments. Y-shaped mesh models (DynaMesh, Gynemesh, and Ultrapro) are implanted in a 3D female pelvic floor finite element model in the extraperitoneal space from the vaginal cuff to the first sacral (S1) bone below promontory. Numerical simulations are conducted during Valsalva maneuver with weakened tissues modeled by reduced tissue stiffness. Tissues are modeled as incompressible, isotropic hyperelastic materials whereas the meshes are modeled either as orthotropic linear elastic or as isotropic hyperlastic materials. The positions of the vaginal cuff and the bladder base are calculated from the pubococcygeal line for female pelvic floor at rest, for prolapse and after repair using the three meshes. Due to mesh mechanics and mesh pore deformation along the loaded direction, the DynaMesh with regular rectangular mesh pores is found to provide better mechanical support to the organs than the Gynemesh and the Ultrapro with irregular hexagonal mesh pores.},
 bibtype = {article},
 author = {Bhattarai, Aroj and Jabbari, Medisa and Anding, Ralf and Staat, Manfred},
 doi = {10.1515/teme-2017-0115},
 journal = {tm - Technisches Messen},
 number = {5}
}

Particularly multiparous elderly women may suffer from vaginal vault prolapse after hysterectomy due to weak support from lax apical ligaments. A decreased amount of estrogen and progesterone in older age is assumed to remodel the collagen thereby reducing tissue stiffness. Sacrocolpopexy is either performed as open or laparoscopic surgery using prosthetic mesh implants to substitute lax ligaments. Y-shaped mesh models (DynaMesh, Gynemesh, and Ultrapro) are implanted in a 3D female pelvic floor finite element model in the extraperitoneal space from the vaginal cuff to the first sacral (S1) bone below promontory. Numerical simulations are conducted during Valsalva maneuver with weakened tissues modeled by reduced tissue stiffness. Tissues are modeled as incompressible, isotropic hyperelastic materials whereas the meshes are modeled either as orthotropic linear elastic or as isotropic hyperlastic materials. The positions of the vaginal cuff and the bladder base are calculated from the pubococcygeal line for female pelvic floor at rest, for prolapse and after repair using the three meshes. Due to mesh mechanics and mesh pore deformation along the loaded direction, the DynaMesh with regular rectangular mesh pores is found to provide better mechanical support to the organs than the Gynemesh and the Ultrapro with irregular hexagonal mesh pores.

@article{
 title = {Wind and fairness in ski jumping: A computer modelling analysis.},
 type = {article},
 year = {2018},
 keywords = {Computer simulation,Optimal control,Ski flying,Sport aerodynamics,Wind compensation},
 pages = {147-153},
 volume = {75},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S002192901830349X,http://www.ncbi.nlm.nih.gov/pubmed/29803308},
 month = {6},
 day = {25},
 id = {1f03ae28-77c7-3f37-80f1-d0b7a080e4c6},
 created = {2018-05-24T19:51:02.809Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-06-30T14:13:13.149Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2018a},
 private_publication = {false},
 abstract = {Wind is closely associated with the discussion of fairness in ski jumping. To counter-act its influence on the jump length, the International Ski Federation (FIS) has introduced a wind compensation approach. We applied three differently accurate computer models of the flight phase with wind (M1, M2, and M3) to study the jump length effects of various wind scenarios. The previously used model M1 is accurate for wind blowing in direction of the flight path, but inaccuracies are to be expected for wind directions deviating from the tangent to the flight path. M2 considers the change of airflow direction, but it does not consider the associated change in the angle of attack of the skis which additionally modifies drag and lift area time functions. M3 predicts the length effect for all wind directions within the plane of the flight trajectory without any mathematical simplification. Prediction errors of M3 are determined only by the quality of the input data: wind velocity, drag and lift area functions, take-off velocity, and weight. For comparing the three models, drag and lift area functions of an optimized reference jump were used. Results obtained with M2, which is much easier to handle than M3, did not deviate noticeably when compared to predictions of the reference model M3. Therefore, we suggest to use M2 in future applications. A comparison of M2 predictions with the FIS wind compensation system showed substantial discrepancies, for instance: in the first flight phase, tailwind can increase jump length, and headwind can decrease it; this is opposite of what had been anticipated before and is not considered in the current wind compensation system in ski jumping.},
 bibtype = {article},
 author = {Jung, Alexander and Müller, Wolfram and Staat, Manfred},
 doi = {10.1016/j.jbiomech.2018.05.001},
 journal = {Journal of Biomechanics}
}

Wind is closely associated with the discussion of fairness in ski jumping. To counter-act its influence on the jump length, the International Ski Federation (FIS) has introduced a wind compensation approach. We applied three differently accurate computer models of the flight phase with wind (M1, M2, and M3) to study the jump length effects of various wind scenarios. The previously used model M1 is accurate for wind blowing in direction of the flight path, but inaccuracies are to be expected for wind directions deviating from the tangent to the flight path. M2 considers the change of airflow direction, but it does not consider the associated change in the angle of attack of the skis which additionally modifies drag and lift area time functions. M3 predicts the length effect for all wind directions within the plane of the flight trajectory without any mathematical simplification. Prediction errors of M3 are determined only by the quality of the input data: wind velocity, drag and lift area functions, take-off velocity, and weight. For comparing the three models, drag and lift area functions of an optimized reference jump were used. Results obtained with M2, which is much easier to handle than M3, did not deviate noticeably when compared to predictions of the reference model M3. Therefore, we suggest to use M2 in future applications. A comparison of M2 predictions with the FIS wind compensation system showed substantial discrepancies, for instance: in the first flight phase, tailwind can increase jump length, and headwind can decrease it; this is opposite of what had been anticipated before and is not considered in the current wind compensation system in ski jumping.

@inproceedings{
 title = {Electromechanical model of hiPSC-derived ventricular cardiomyocytes co-cultured with fibroblasts},
 type = {inproceedings},
 year = {2018},
 pages = {859-869},
 websites = {http://www.eccm-ecfd2018.org/admin/files/filePaper/p435.pdf},
 publisher = {International Center for Numerical Methods in Engineering (CIMNE) Barcelona, Spain},
 city = {Glasgow},
 id = {df727a03-c4b7-3ecd-8956-96e934bb521d},
 created = {2018-05-30T05:17:58.133Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-06-21T14:05:52.967Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2018},
 private_publication = {false},
 abstract = {The CellDrum provides an experimental setup to study the mechanical effects of fibroblasts co-cultured with hiPSC-derived ventricular cardiomyocytes. Multi-scale computational models based on the Finite Element Method are developed. Coupled electrical cardiomyocyte-fibroblast models (cell level) are embedded into reaction-diffusion equations (tissue level) which compute the propagation of the action potential in the cardiac tissue. Electromechanical coupling is realised by an excitation-contraction model (cell level) and the active stress arising during contraction is added to the passive stress in the force balance, which determines the tissue displacement (tissue level). Tissue parameters in the model can be identified experimentally to the specific sample.},
 bibtype = {inproceedings},
 author = {Jung, Alexander and Frotscher, Ralf and Staat, Manfred},
 editor = {Owen, Roger and de Borst, René and Reese, Jason and Pearce, Chris},
 booktitle = {6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7)}
}

The CellDrum provides an experimental setup to study the mechanical effects of fibroblasts co-cultured with hiPSC-derived ventricular cardiomyocytes. Multi-scale computational models based on the Finite Element Method are developed. Coupled electrical cardiomyocyte-fibroblast models (cell level) are embedded into reaction-diffusion equations (tissue level) which compute the propagation of the action potential in the cardiac tissue. Electromechanical coupling is realised by an excitation-contraction model (cell level) and the active stress arising during contraction is added to the passive stress in the force balance, which determines the tissue displacement (tissue level). Tissue parameters in the model can be identified experimentally to the specific sample.

@inproceedings{
 title = {Direct plastic structural design by chance constrained programming},
 type = {inproceedings},
 year = {2018},
 pages = {3992-4003},
 websites = {http://www.eccm-ecfd2018.org/admin/files/filePaper/p1777.pdf},
 publisher = {International Center for Numerical Methods in Engineering (CIMNE) Barcelona, Spain},
 city = {Glasgow},
 id = {19623750-64f2-33a2-b535-1f0539dc81da},
 created = {2018-05-30T05:24:08.515Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-06-21T14:05:53.056Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Tran2018},
 private_publication = {false},
 abstract = {We propose a stochastic programming method to analyse limit and shakedown of structures under random strength with lognormal distribution. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit or the shakedown limit. The edge-based smoothed finite element method (ES-FEM) using three-node linear triangular elements is used.},
 bibtype = {inproceedings},
 author = {Trần, Ngọc Trình and Matthies, Hermann G. and Stavroulakis, Georgios Eleftherios and Staat, Manfred},
 editor = {Owen, Roger and de Borst, René and Reese, Jason and Pearce, Chris},
 booktitle = {6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7)}
}

We propose a stochastic programming method to analyse limit and shakedown of structures under random strength with lognormal distribution. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit or the shakedown limit. The edge-based smoothed finite element method (ES-FEM) using three-node linear triangular elements is used.

@inproceedings{
 title = {Biomechanical multibody model with refined kinematics of the elbow},
 type = {inproceedings},
 year = {2018},
 pages = {2700-2710},
 websites = {http://www.eccm-ecfd2018.org/admin/files/filePaper/p2085.pdf},
 publisher = {International Center for Numerical Methods in Engineerin (CIMNE) Barcelona, Spain},
 city = {Glasgow},
 id = {4c951f38-43c0-378b-a822-820d5958029e},
 created = {2018-05-30T05:29:10.437Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-06-21T14:05:52.933Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Kahmann2018},
 private_publication = {false},
 abstract = {The overall objective of this study is to develop a new external fixator, which closely maps the native kinematics of the elbow to decrease the joint force resulting in reduced rehabilitation time and pain. An experimental setup was designed to determine the native kinematics of the elbow during flexion of cadaveric arms. As a preliminary study, data from literature was used to modify a published biomechanical model for the calculation of the joint and muscle forces. They were compared to the original model and the effect of the kinematic refinement was evaluated. Furthermore, the obtained muscle forces were determined in order to apply them in the experimental setup. The joint forces in the modified model differed slightly from the forces in the original model. The muscle force curves changed particularly for small flexion angles but their magnitude for larger angles was consistent.},
 bibtype = {inproceedings},
 author = {Kahmann, Stephanie and Uschok, Stephan and Wegmann, Kilian and Mueller, Lars and Staat, Manfred},
 editor = {Owen, Roger and de Borst, René and Reese, Jason and Pearce, Chris},
 booktitle = {6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7)}
}

The overall objective of this study is to develop a new external fixator, which closely maps the native kinematics of the elbow to decrease the joint force resulting in reduced rehabilitation time and pain. An experimental setup was designed to determine the native kinematics of the elbow during flexion of cadaveric arms. As a preliminary study, data from literature was used to modify a published biomechanical model for the calculation of the joint and muscle forces. They were compared to the original model and the effect of the kinematic refinement was evaluated. Furthermore, the obtained muscle forces were determined in order to apply them in the experimental setup. The joint forces in the modified model differed slightly from the forces in the original model. The muscle force curves changed particularly for small flexion angles but their magnitude for larger angles was consistent.

@inproceedings{
 title = {Modelling analysis of the effect of fibroblast on ventricular contraction},
 type = {inproceedings},
 year = {2018},
 websites = {https://app.oxfordabstracts.com/stages/123/programme-builder/submission/19174},
 city = {Dublin},
 id = {5072cdec-4010-3f36-b875-d765a71f805e},
 created = {2018-07-16T12:07:26.708Z},
 file_attached = {true},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T14:48:23.396Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2018c},
 private_publication = {false},
 abstract = {Introduction},
 bibtype = {inproceedings},
 author = {Jung, Alexander and Frotscher, Ralf and Goßmann, Matthias and Staat, Manfred},
 booktitle = {BMT2018, 8th World Congress of Biomechanics}
}

Introduction

@article{
 title = {Optical strain measurement for the modeling of surgical meshes and their porosity},
 type = {article},
 year = {2018},
 keywords = {Digital image correlation,Orthotropy,Porosity,Surgical mesh},
 pages = {181-184},
 volume = {4},
 websites = {http://www.degruyter.com/view/j/cdbme.2018.4.issue-1/cdbme-2018-0045/cdbme-2018-0045.xml},
 month = {9},
 day = {1},
 id = {f1978ece-91ff-3279-ad51-6b151f6ecc13},
 created = {2018-09-22T14:15:23.834Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:44:00.110Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Horbach2018},
 private_publication = {false},
 abstract = {The porosity of surgical meshes makes them flexible for large elastic deformation and establishes the healing conditions of good tissue ingrowth. The biomechanic modeling of orthotropic and compressible materials requires new materials models and simulstaneoaus fit of deformation in the load direction as well as trannsversely to to load. This nonlinear modeling can be achieved by an optical deformation measurement. At the same time the full field deformation measurement allows the dermination of the change of porosity with deformation. Also the socalled effective porosity, which has been defined to asses the tisssue interatcion with the mesh implants, can be determined from the global deformation of the surgical meshes.},
 bibtype = {article},
 author = {Horbach, Andreas J. and Staat, Manfred},
 doi = {10.1515/cdbme-2018-0045},
 journal = {Current Directions in Biomedical Engineering},
 number = {1}
}

The porosity of surgical meshes makes them flexible for large elastic deformation and establishes the healing conditions of good tissue ingrowth. The biomechanic modeling of orthotropic and compressible materials requires new materials models and simulstaneoaus fit of deformation in the load direction as well as trannsversely to to load. This nonlinear modeling can be achieved by an optical deformation measurement. At the same time the full field deformation measurement allows the dermination of the change of porosity with deformation. Also the socalled effective porosity, which has been defined to asses the tisssue interatcion with the mesh implants, can be determined from the global deformation of the surgical meshes.

@article{
 title = {Computational comparison of different textile implants to correct apical prolapse in females},
 type = {article},
 year = {2018},
 pages = {661-664},
 volume = {4},
 websites = {http://www.degruyter.com/view/j/cdbme.2018.4.issue-1/cdbme-2018-0159/cdbme-2018-0159.xml},
 month = {9},
 day = {1},
 id = {15f6a0d3-fb56-3c7c-acbb-2cb9cbe319f6},
 created = {2018-09-22T14:15:53.817Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-11T22:02:04.233Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2018d},
 private_publication = {false},
 abstract = {Prosthetic textile implants of different shapes, sizes and polymers are used to correct the apical prolapse after hysterectomy (removal of the uterus). The selection of the implant before or during minimally invasive surgery depends on the patient’s anatomical defect, intended function after reconstruction and most importantly the surgeon’s preference. Weakness or damage of the supporting tissues during childbirth, menopause or previous pelvic surgeries may put females in higher risk of prolapse. Numerical simulations of reconstructed pelvic floor with weakened tissues and organ supported by textile product models: DynaMesh® PRS soft, DynaMesh® PRP soft and DynaMesh® CESA from FEG Textiltechnik mbH, Germany are compared.},
 bibtype = {article},
 author = {Bhattarai, Aroj and Staat, Manfred},
 doi = {10.1515/cdbme-2018-0159},
 journal = {Current Directions in Biomedical Engineering},
 number = {1}
}

Prosthetic textile implants of different shapes, sizes and polymers are used to correct the apical prolapse after hysterectomy (removal of the uterus). The selection of the implant before or during minimally invasive surgery depends on the patient’s anatomical defect, intended function after reconstruction and most importantly the surgeon’s preference. Weakness or damage of the supporting tissues during childbirth, menopause or previous pelvic surgeries may put females in higher risk of prolapse. Numerical simulations of reconstructed pelvic floor with weakened tissues and organ supported by textile product models: DynaMesh® PRS soft, DynaMesh® PRP soft and DynaMesh® CESA from FEG Textiltechnik mbH, Germany are compared.

@article{
 title = {Untersuchung der thermischen Auswirkung von therapeutischem Ultraschall},
 type = {article},
 year = {2018},
 keywords = {Diathermie,Infrarotthermografie,Mechanotherapie,Ultraschall,therapeutischer Ultraschall},
 pages = {518-522},
 volume = {7},
 id = {631075c0-aae7-34ee-a4ee-5db7137d0018},
 created = {2018-10-08T19:28:18.510Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-02-07T20:02:54.435Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Keutmann2018},
 private_publication = {false},
 abstract = {In der Orthopädie zählt der therapeutische Ultraschall als Mittel zur Prävention und Therapiebegleitung. Er hat mechanische, thermische und physiko-chemische Auswirkungen auf den menschlichen Körper. Um mehr Erkenntnisse über die thermischen Auswirkungen zu erlangen, wurden Versuche an einem Hydrogel- Phantom und an Probanden durchgeführt. Dabei entstand eine signifikante Erwärmung des Gewebes, welche beim Probandenversuch an der Oberfläche und beim Hydrogelversuch in der Tiefe gemessen wurde.},
 bibtype = {article},
 author = {Keutmann, Sabine and Staat, Manfred and van Laack, Walter},
 doi = {10.3238/oup.2018.0518–0522},
 journal = {OUP ∙ Zeitschrift für die orthopädische und unfallchirurgische Praxis},
 number = {10}
}

In der Orthopädie zählt der therapeutische Ultraschall als Mittel zur Prävention und Therapiebegleitung. Er hat mechanische, thermische und physiko-chemische Auswirkungen auf den menschlichen Körper. Um mehr Erkenntnisse über die thermischen Auswirkungen zu erlangen, wurden Versuche an einem Hydrogel- Phantom und an Probanden durchgeführt. Dabei entstand eine signifikante Erwärmung des Gewebes, welche beim Probandenversuch an der Oberfläche und beim Hydrogelversuch in der Tiefe gemessen wurde.

@inbook{
 type = {inbook},
 year = {2018},
 pages = {209-232},
 websites = {http://link.springer.com/10.1007/978-981-10-7904-7_9},
 publisher = {Springer Singapore},
 city = {Singapore},
 chapter = {Growth modelling promoting mechanical stimulation of smooth muscle cells of porcine tubular organs in a fibrin-PVDF scaffold},
 id = {75db36c7-b64a-3da3-8f33-1b039b7fc3c0},
 created = {2018-12-17T20:11:50.173Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-05-22T18:53:10.846Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Duong2018a},
 private_publication = {false},
 abstract = {Reconstructive surgery and tissue replacements like ureters or bladders reconstruction have been recently studied, taking into account growth and remodelling of cells since living cells are capable of growing, adapting, remodelling or degrading and restoring in order to deform and respond to stimuli. Hence, shapes of ureters or bladders and their microstructure change during growth and these changes strongly depend on external stimuli such as training. We present the mechanical stimulation of smooth muscle cells in a tubular fibrin-PVDFA scaffold and the modelling of the growth of tissue by stimuli. To this end, mechanotransduction was performed with a kyphoplasty balloon catheter that was guided through the lumen of the tubular structure. The bursting pressure was examined to compare the stability of the incubated tissue constructs. The results showed the significant changes on tissues with training by increasing the burst pressure as a characteristic mechanical property and the smooth muscle cells were more oriented with uniformly higher density. Besides, the computational growth models also exhibited the accurate tendencies of growth of the cells under different external stimuli. Such models may lead to design standards for the better layered tissue structure in reconstructing of tubular organs characterized as composite materials such as intestines, ureters and arteries.},
 bibtype = {inbook},
 author = {Dương, Minh Tuấn and Seifarth, Volker and Artmann, Ayşegül and Artmann, Gerhard M. and Staat, Manfred},
 editor = {Artmann, Gerhard M. and Artmann, Aysegül and Zhubanova, Azhar A. and Digel, Ilya},
 doi = {10.1007/978-981-10-7904-7_9},
 title = {Biological, Physical and Technical Basics of Cell Engineering}
}

Reconstructive surgery and tissue replacements like ureters or bladders reconstruction have been recently studied, taking into account growth and remodelling of cells since living cells are capable of growing, adapting, remodelling or degrading and restoring in order to deform and respond to stimuli. Hence, shapes of ureters or bladders and their microstructure change during growth and these changes strongly depend on external stimuli such as training. We present the mechanical stimulation of smooth muscle cells in a tubular fibrin-PVDFA scaffold and the modelling of the growth of tissue by stimuli. To this end, mechanotransduction was performed with a kyphoplasty balloon catheter that was guided through the lumen of the tubular structure. The bursting pressure was examined to compare the stability of the incubated tissue constructs. The results showed the significant changes on tissues with training by increasing the burst pressure as a characteristic mechanical property and the smooth muscle cells were more oriented with uniformly higher density. Besides, the computational growth models also exhibited the accurate tendencies of growth of the cells under different external stimuli. Such models may lead to design standards for the better layered tissue structure in reconstructing of tubular organs characterized as composite materials such as intestines, ureters and arteries.

@inbook{
 type = {inbook},
 year = {2018},
 pages = {251-275},
 websites = {http://link.springer.com/10.1007/978-981-10-7904-7_11},
 publisher = {Springer Singapore},
 city = {Singapore},
 chapter = {Mechanics of soft tissue reactions to textile mesh implants},
 id = {61aa4b32-716d-3fc2-bf8c-71dd262dff55},
 created = {2018-12-17T20:11:50.222Z},
 file_attached = {false},
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 citation_key = {Bhattarai2018f},
 private_publication = {false},
 abstract = {For pelvic floor disorders that cannot be treated with non-surgical procedures, minimally invasive surgery has become a more frequent and safer repair procedure. More than 20 million prosthetic meshes are implanted each year worldwide. The simple selection of a single synthetic mesh construction for any level and type of pelvic floor dysfunctions without adopting the design to specific requirements increase the risks for mesh related complications. Adverse events are closely related to chronic foreign body reaction, with enhanced formation of scar tissue around the surgical meshes, manifested as pain, mesh erosion in adjacent structures (with organ tissue cut), mesh shrinkage, mesh rejection and eventually recurrence. Such events, especially scar formation depend on effective porosity of the mesh, which decreases discontinuously at a critical stretch when pore areas decrease making the surgical reconstruction ineffective that further augments the re-operation costs. The extent of fibrotic reaction is increased with higher amount of foreign body material, larger surface, small pore size or with inadequate textile elasticity. Standardized studies of different meshes are essential to evaluate influencing factors for the failure and success of the reconstruction. Measurements of elasticity and tensile strength have to consider the mesh anisotropy as result of the textile structure. An appropriate mesh then should show some integration with limited scar reaction and preserved pores that are filled with local fat tissue. This chapter reviews various tissue reactions to different monofilament mesh implants that are used for incontinence and hernia repairs and study their mechanical behavior. This helps to predict the functional and biological outcomes after tissue reinforcement with meshes and permits further optimization of the meshes for the specific indications to improve the success of the surgical treatment.},
 bibtype = {inbook},
 author = {Bhattarai, Aroj and Staat, Manfred},
 editor = {Gerhard M. Artmann, undefined and Artmann, Aysegül and Zhubanova, Azhar A. and Digel, Ilya},
 doi = {10.1007/978-981-10-7904-7_11},
 title = {Biological, Physical and Technical Basics of Cell Engineering}
}

For pelvic floor disorders that cannot be treated with non-surgical procedures, minimally invasive surgery has become a more frequent and safer repair procedure. More than 20 million prosthetic meshes are implanted each year worldwide. The simple selection of a single synthetic mesh construction for any level and type of pelvic floor dysfunctions without adopting the design to specific requirements increase the risks for mesh related complications. Adverse events are closely related to chronic foreign body reaction, with enhanced formation of scar tissue around the surgical meshes, manifested as pain, mesh erosion in adjacent structures (with organ tissue cut), mesh shrinkage, mesh rejection and eventually recurrence. Such events, especially scar formation depend on effective porosity of the mesh, which decreases discontinuously at a critical stretch when pore areas decrease making the surgical reconstruction ineffective that further augments the re-operation costs. The extent of fibrotic reaction is increased with higher amount of foreign body material, larger surface, small pore size or with inadequate textile elasticity. Standardized studies of different meshes are essential to evaluate influencing factors for the failure and success of the reconstruction. Measurements of elasticity and tensile strength have to consider the mesh anisotropy as result of the textile structure. An appropriate mesh then should show some integration with limited scar reaction and preserved pores that are filled with local fat tissue. This chapter reviews various tissue reactions to different monofilament mesh implants that are used for incontinence and hernia repairs and study their mechanical behavior. This helps to predict the functional and biological outcomes after tissue reinforcement with meshes and permits further optimization of the meshes for the specific indications to improve the success of the surgical treatment.

@inbook{
 type = {inbook},
 year = {2018},
 pages = {233-250},
 websites = {http://link.springer.com/10.1007/978-981-10-7904-7_10},
 publisher = {Springer Singapore},
 city = {Singapore},
 chapter = {Towards patient-specific computational modeling of hiPS-derived cardiomyocyte function and drug action},
 id = {3ba21d27-9314-382e-a476-30f9dea2a32d},
 created = {2018-12-17T20:11:50.270Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-05-22T18:53:10.837Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2018},
 private_publication = {false},
 abstract = {Human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) today are widely used for the investigation of normal electromechanical cardiac function, of cardiac medication and of mutations. Computational models are thus established that simulate the behavior of this kind of cells. This section first motivates the modeling of hiPS-CM and then presents and discusses several modeling approaches of microscopic and macroscopic constituents of human-induced pluripotent stem cell-derived and mature human cardiac tissue. The focus is led on the mapping of the computational results one can achieve with these models onto mature human cardiomyocyte models, the latter being the real matter of interest. Model adaptivity is the key feature that is discussed because it opens the way for modeling various biological effects like biological variability, medication, mutation and phenotypical expression. We compare the computational with experimental results with respect to normal cardiac function and with respect to inotropic and chronotropic drug effects. The section closes with a discussion on the status quo of the specificity of computational models and on what challenges have to be solved to reach patient-specificity.},
 bibtype = {inbook},
 author = {Frotscher, Ralf and Staat, Manfred},
 editor = {Gerhard M. Artmann, undefined and Artmann, Aysegül and Zhubanova, Azhar A. and Digel, Ilya},
 doi = {10.1007/978-981-10-7904-7_10},
 title = {Biological, Physical and Technical Basics of Cell Engineering}
}

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) today are widely used for the investigation of normal electromechanical cardiac function, of cardiac medication and of mutations. Computational models are thus established that simulate the behavior of this kind of cells. This section first motivates the modeling of hiPS-CM and then presents and discusses several modeling approaches of microscopic and macroscopic constituents of human-induced pluripotent stem cell-derived and mature human cardiac tissue. The focus is led on the mapping of the computational results one can achieve with these models onto mature human cardiomyocyte models, the latter being the real matter of interest. Model adaptivity is the key feature that is discussed because it opens the way for modeling various biological effects like biological variability, medication, mutation and phenotypical expression. We compare the computational with experimental results with respect to normal cardiac function and with respect to inotropic and chronotropic drug effects. The section closes with a discussion on the status quo of the specificity of computational models and on what challenges have to be solved to reach patient-specificity.

@inbook{
 type = {inbook},
 year = {2018},
 pages = {85-103},
 websites = {http://link.springer.com/10.1007/978-3-319-59810-9_6},
 publisher = {Springer International Publishing},
 city = {Cham},
 chapter = {Shakedown analysis under stochastic uncertainty by chance constrained programming},
 id = {e2638f49-b257-3e2e-b53f-2e22c259f205},
 created = {2019-10-12T21:11:57.603Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-10-12T21:12:37.386Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Tran2018},
 private_publication = {false},
 abstract = {In this paper we propose a stochastic programming method to analyse limit and shakedown of structures under uncertainty condition of strength. Based on the duality theory, the shakedown load multiplier formulated by the kinematic theorem is proved actually to be the dual form of the shakedown load multiplier formulated by static theorem. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit. The edge-based smoothed finite element method (ES-FEM) with three-node linear triangular elements is used for structural analysis.},
 bibtype = {inbook},
 author = {Tran, N. T. and Tran, Thanh Ngoc and Matthies, Hermann G. and Stavroulakis, Georgios Eleftherios and Staat, Manfred},
 editor = {Barrera, Olga and Cocks, Alan and Ponter, Alan},
 doi = {10.1007/978-3-319-59810-9_6},
 title = {Advances in Direct Methods for Materials and Structures}
}

In this paper we propose a stochastic programming method to analyse limit and shakedown of structures under uncertainty condition of strength. Based on the duality theory, the shakedown load multiplier formulated by the kinematic theorem is proved actually to be the dual form of the shakedown load multiplier formulated by static theorem. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit. The edge-based smoothed finite element method (ES-FEM) with three-node linear triangular elements is used for structural analysis.

@article{
 title = {Poster Session},
 type = {article},
 year = {2018},
 pages = {276-401},
 volume = {63},
 websites = {https://www.degruyter.com/document/doi/10.1515/bmt-2018-6051/html},
 month = {9},
 day = {1},
 id = {20a33964-3aed-31b0-8063-56c33e0ee21f},
 created = {2021-10-25T16:36:29.893Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-03-23T10:38:35.426Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2018},
 private_publication = {false},
 bibtype = {article},
 author = {Bhattarai, Aroj and Staat, Manfred},
 doi = {10.1515/bmt-2018-6051},
 journal = {Biomedical Engineering / Biomedizinische Technik},
 number = {s1}
}

@article{
 title = {Plate Osteosynthesis of Proximal Ulna Fractures-A Biomechanical Micromotion Analysis.},
 type = {article},
 year = {2017},
 keywords = {Proximal ulna,double plating,fracture,olecranon,posterior plating},
 pages = {834.e1-834.e7},
 volume = {42},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0363502317308316,http://www.ncbi.nlm.nih.gov/pubmed/28606433},
 month = {10},
 id = {b4ecf518-2441-395b-b568-fd32d77eaa4e},
 created = {2017-07-03T20:16:11.481Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-06-30T14:19:45.284Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2017b},
 private_publication = {false},
 abstract = {PURPOSE Double plating has been promoted, in recent years, as an alternative treatment method for proximal ulna fractures. This study aimed to compare the biomechanical properties of double-plate osteosynthesis with posterior plate fixation using a novel investigational design utilizing a 3-dimensional camera system to analyze fracture micromotion. METHODS Fourteen fresh-frozen specimens were available for this study. Mayo type IIA fractures of the olecranon were created and internal fixation was performed with either an angular stable posterior plate or angular stable double plates. Fracture micromotion was evaluated by means of digital image correlation with a 3-dimensional camera system before and after dynamic cyclic loading from 15° to 90° of elbow flexion with a pulling force of 25 N to 80 N. RESULTS Micromotion of fragments was less pronounced in double-plate osteosynthesis when compared with single plates before and after cyclic loading. However, overall results were similar. Two of the single plates failed during cyclic loading but there were no failures in the double plates. CONCLUSIONS This biomechanical analysis shows that single and double plating results in comparable stability of fixation. Although the double-plating technique tends to provide more stable fixation, relevant differences were not observed. CLINICAL RELEVANCE Double plating potentially represents an efficient option for fixation of proximal ulna fractures. It could decrease the risk of soft tissue complications owing to their low profile and the superior soft tissue coverage.},
 bibtype = {article},
 author = {Hackl, Michael and Mayer, Katharina and Weber, Mareike and Staat, Manfred and van Riet, Roger and Burkhart, Klaus Josef and Müller, Lars Peter and Wegmann, Kilian},
 doi = {10.1016/j.jhsa.2017.05.014},
 journal = {The Journal of Hand Surgery, American Volume},
 number = {10}
}

PURPOSE Double plating has been promoted, in recent years, as an alternative treatment method for proximal ulna fractures. This study aimed to compare the biomechanical properties of double-plate osteosynthesis with posterior plate fixation using a novel investigational design utilizing a 3-dimensional camera system to analyze fracture micromotion. METHODS Fourteen fresh-frozen specimens were available for this study. Mayo type IIA fractures of the olecranon were created and internal fixation was performed with either an angular stable posterior plate or angular stable double plates. Fracture micromotion was evaluated by means of digital image correlation with a 3-dimensional camera system before and after dynamic cyclic loading from 15° to 90° of elbow flexion with a pulling force of 25 N to 80 N. RESULTS Micromotion of fragments was less pronounced in double-plate osteosynthesis when compared with single plates before and after cyclic loading. However, overall results were similar. Two of the single plates failed during cyclic loading but there were no failures in the double plates. CONCLUSIONS This biomechanical analysis shows that single and double plating results in comparable stability of fixation. Although the double-plating technique tends to provide more stable fixation, relevant differences were not observed. CLINICAL RELEVANCE Double plating potentially represents an efficient option for fixation of proximal ulna fractures. It could decrease the risk of soft tissue complications owing to their low profile and the superior soft tissue coverage.

@article{
 title = {Modelling of compressible and orthotropic surgical mesh implants based on optical deformation measurement.},
 type = {article},
 year = {2017},
 keywords = {Digital image correlation,Effective porosity,Mesh implants,Optical strain measurement,Polyconvex strain energy function,Pore size},
 pages = {400-410},
 volume = {74},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S1751616117302503,http://www.ncbi.nlm.nih.gov/pubmed/28697434},
 month = {10},
 id = {17b53a32-7680-355a-99da-82333fe1598b},
 created = {2017-07-14T15:52:15.832Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-06-30T14:05:17.895Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Horbach2017},
 private_publication = {false},
 abstract = {There is a potential mismatch between surgical mesh implants for hernia repair of pelvic floor surgery and the host tissue because soft tissue is incompressible and meshes are compressible. Therefore, mesh and tissue may develop different stiffness over the range of deformation. In addition compressibility is related to a change of porosity of the mesh which may decrease during the deformation. Scar formation and the ingrowth of the mesh can be related to effective porosity which decreases discontinuously in uniaxial loading at a critical stretch when pore areas collapse and therefore the mesh becomes ineffective. Compressibility requires several non standard approaches which can be performed with high accuracy and local resolution by deformation measurement with digital image correlation (DIC). A compressible hyperelastic model is chosen and identified with biaxial deformation measurements. Also effective porosity of deformed meshes can be calculated on the basis of biaxial deformation. The proposed constitutive equation and the developed model of effective porosity are represented in form of principle stretch. Stretch can be measured with magnetic resonance imaging (MRI) visible meshes so that stress and effective porosity can be derived in vivo.},
 bibtype = {article},
 author = {Horbach, Andreas J. and Duong, Minh Tuan and Staat, Manfred},
 doi = {10.1016/j.jmbbm.2017.06.012},
 journal = {Journal of the Mechanical Behavior of Biomedical Materials}
}

There is a potential mismatch between surgical mesh implants for hernia repair of pelvic floor surgery and the host tissue because soft tissue is incompressible and meshes are compressible. Therefore, mesh and tissue may develop different stiffness over the range of deformation. In addition compressibility is related to a change of porosity of the mesh which may decrease during the deformation. Scar formation and the ingrowth of the mesh can be related to effective porosity which decreases discontinuously in uniaxial loading at a critical stretch when pore areas collapse and therefore the mesh becomes ineffective. Compressibility requires several non standard approaches which can be performed with high accuracy and local resolution by deformation measurement with digital image correlation (DIC). A compressible hyperelastic model is chosen and identified with biaxial deformation measurements. Also effective porosity of deformed meshes can be calculated on the basis of biaxial deformation. The proposed constitutive equation and the developed model of effective porosity are represented in form of principle stretch. Stretch can be measured with magnetic resonance imaging (MRI) visible meshes so that stress and effective porosity can be derived in vivo.

@article{
 title = {Radial shortening osteotomy reduces radiocapitellar contact pressures while preserving valgus stability of the elbow.},
 type = {article},
 year = {2017},
 keywords = {Biomechanics,Post-traumatic osteoarthritis,Proximal radius,Radial head fracture,Salvage procedure,Shortening osteotomy},
 pages = {2280-2288},
 volume = {25},
 websites = {http://link.springer.com/10.1007/s00167-017-4468-z,http://www.ncbi.nlm.nih.gov/pubmed/28238092},
 month = {7},
 day = {25},
 id = {d5f91a1b-1cc6-3063-8466-ee17aff785ef},
 created = {2017-07-14T15:52:43.933Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-06-30T14:13:13.053Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2017a},
 private_publication = {false},
 abstract = {PURPOSE Shortening osteotomy of the proximal radius might represent a potential salvage procedure in symptomatic radiocapitellar osteoarthritis, which could decrease radiocapitellar load while preserving the native radial head. In an in-vitro biomechanical investigation, we sought to determine whether shortening osteotomy of the proximal radius (1) decreases the radiocapitellar joint pressure upon axial loading and (2) retains valgus stability of the elbow. In addition, the anatomic configuration of the lesser sigmoid notch was evaluated to assess possible contraindications. METHODS Axial loading (0-400 N) and valgus torque (7.5 N m) over the full range of motion were applied to 14 fresh-frozen specimens before and after shortening osteotomy of the proximal radius by 2.5 mm. Radiocapitellar and ulnohumeral load distribution during axial compression was evaluated using a digital pressure mapping sensor. Valgus displacement was analyzed with a 3D camera system. The inclination angle (α) of the lesser sigmoid notch was assessed via 50 CT scans. RESULTS Up to axial loading of 250 N, shortening osteotomy caused a significant decrease in radiocapitellar contact pressures (p < 0.041). Valgus stability of specimens did not differ before and after shortening osteotomy (n.s.). The mean inclination angle (α) of the lesser sigmoid notch was 11.3° ± 6.3°. 46% had an inclination angle of ≤ 10° (type I). 46% had an inclination angle of 11°-20° (type II). In 8%, the inclination angle was >20° (type III). CONCLUSION Shortening osteotomy of the proximal radius can decrease radiocapitellar contact pressures during axial loading of up to 250 N. Primary valgus stability is not relevantly influenced by this procedure. In few patients, shortening osteotomy may cause radioulnar impingement of the radial head at the distal edge of the lesser sigmoid notch due to an inclination angle of >20°. Shortening osteotomy might be a promising treatment option to decrease pain levels in case of isolated radiocapitellar osteoarthritis.},
 bibtype = {article},
 author = {Hackl, Michael and Wegmann, Kilian and Kahmann, Stephanie L. and Heinze, Nicolai and Staat, Manfred and Neiss, Wolfram F. and Scaal, Martin and Müller, Lars P.},
 doi = {10.1007/s00167-017-4468-z},
 journal = {Knee Surgery, Sports Traumatology, Arthroscopy : official journal of the ESSKA},
 number = {7}
}

PURPOSE Shortening osteotomy of the proximal radius might represent a potential salvage procedure in symptomatic radiocapitellar osteoarthritis, which could decrease radiocapitellar load while preserving the native radial head. In an in-vitro biomechanical investigation, we sought to determine whether shortening osteotomy of the proximal radius (1) decreases the radiocapitellar joint pressure upon axial loading and (2) retains valgus stability of the elbow. In addition, the anatomic configuration of the lesser sigmoid notch was evaluated to assess possible contraindications. METHODS Axial loading (0-400 N) and valgus torque (7.5 N m) over the full range of motion were applied to 14 fresh-frozen specimens before and after shortening osteotomy of the proximal radius by 2.5 mm. Radiocapitellar and ulnohumeral load distribution during axial compression was evaluated using a digital pressure mapping sensor. Valgus displacement was analyzed with a 3D camera system. The inclination angle (α) of the lesser sigmoid notch was assessed via 50 CT scans. RESULTS Up to axial loading of 250 N, shortening osteotomy caused a significant decrease in radiocapitellar contact pressures (p < 0.041). Valgus stability of specimens did not differ before and after shortening osteotomy (n.s.). The mean inclination angle (α) of the lesser sigmoid notch was 11.3° ± 6.3°. 46% had an inclination angle of ≤ 10° (type I). 46% had an inclination angle of 11°-20° (type II). In 8%, the inclination angle was >20° (type III). CONCLUSION Shortening osteotomy of the proximal radius can decrease radiocapitellar contact pressures during axial loading of up to 250 N. Primary valgus stability is not relevantly influenced by this procedure. In few patients, shortening osteotomy may cause radioulnar impingement of the radial head at the distal edge of the lesser sigmoid notch due to an inclination angle of >20°. Shortening osteotomy might be a promising treatment option to decrease pain levels in case of isolated radiocapitellar osteoarthritis.

@article{
 title = {Reply to the letter to the editor: shortening osteotomy of the proximal radius.},
 type = {article},
 year = {2017},
 pages = {3328-3329},
 volume = {25},
 websites = {http://link.springer.com/10.1007/s00167-017-4666-8,http://www.ncbi.nlm.nih.gov/pubmed/28840264},
 day = {24},
 id = {396538fd-4918-3b77-b74a-af3008f0bede},
 created = {2017-09-04T18:37:14.862Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-06-30T14:13:13.146Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2017},
 private_publication = {false},
 bibtype = {article},
 author = {Hackl, Michael and Wegmann, Kilian and Kahmann, Stephanie L. and Heinze, Nicolai and Staat, Manfred and Neiss, Wolfram F. and Scaal, Martin and Müller, Lars P.},
 doi = {10.1007/s00167-017-4666-8},
 journal = {Knee Surgery, Sports Traumatology, Arthroscopy : official journal of the ESSKA},
 number = {10}
}

@article{
 title = {Suture button reconstruction of the central band of the interosseous membrane in Essex-Lopresti lesions: a comparative biomechanical investigation.},
 type = {article},
 year = {2017},
 keywords = {Essex-Lopresti injury,TightRope,biomechanics,interosseous membrane,longitudinal forearm instability,reconstruction},
 pages = {370-376},
 volume = {42},
 websites = {http://journals.sagepub.com/doi/10.1177/1753193416665943,http://www.ncbi.nlm.nih.gov/pubmed/27573130},
 month = {5},
 day = {29},
 id = {a99468e2-b6ff-3738-b8f2-c46b8ca61424},
 created = {2018-12-29T21:54:45.786Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-06-30T14:13:13.135Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2017},
 private_publication = {false},
 abstract = {Surgical reconstruction of the interosseous membrane may restore longitudinal forearm stability in Essex-Lopresti lesions. This study aimed to compare the longitudinal stability of the intact forearm with a single-bundle and a double-bundle reconstruction of the central band of the interosseous membrane using digital image correlation with a three-dimensional camera system. Single and cyclic axial loading of eight fresh-frozen forearm specimens was carried out in the intact state, after creation of an Essex-Lopresti lesion, after a single-bundle and after a double-bundle reconstruction of the central band using a TightRope® (Arthrex GmbH, Munich, Germany) construct. Instability significantly increased after creation of an Essex-Lopresti lesion. The stability of intact specimens was similar to both reconstruction techniques. The results of this study suggest that TightRope® reconstruction of the central band restores longitudinal forearm stability. However, the single-bundle technique may be less reliable than double-bundle reconstruction. LEVEL OF EVIDENCE Basic Science Study.},
 bibtype = {article},
 author = {Hackl, Michael and Andermahr, J. and Staat, Manfred and Bremer, I. and Borggrefe, J. and Prescher, Andreas and Müller, L. P. and Wegmann, Kilian},
 doi = {10.1177/1753193416665943},
 journal = {The Journal of Hand Surgery, European volume},
 number = {4}
}

Surgical reconstruction of the interosseous membrane may restore longitudinal forearm stability in Essex-Lopresti lesions. This study aimed to compare the longitudinal stability of the intact forearm with a single-bundle and a double-bundle reconstruction of the central band of the interosseous membrane using digital image correlation with a three-dimensional camera system. Single and cyclic axial loading of eight fresh-frozen forearm specimens was carried out in the intact state, after creation of an Essex-Lopresti lesion, after a single-bundle and after a double-bundle reconstruction of the central band using a TightRope® (Arthrex GmbH, Munich, Germany) construct. Instability significantly increased after creation of an Essex-Lopresti lesion. The stability of intact specimens was similar to both reconstruction techniques. The results of this study suggest that TightRope® reconstruction of the central band restores longitudinal forearm stability. However, the single-bundle technique may be less reliable than double-bundle reconstruction. LEVEL OF EVIDENCE Basic Science Study.

@inbook{
 type = {inbook},
 year = {2017},
 keywords = {Constitutive model,Ill-conditioned,Numerical stability,Physical behaviour,Soft tissues},
 pages = {1-18},
 volume = {2},
 issue = {3},
 websites = {http://www.scirp.org/book/DetailedInforOfABook.aspx?bookID=2445,http://www.apjcen.com/content/2/1/3},
 month = {12},
 publisher = {Scientific Research Publishing},
 day = {8},
 city = {Wuhan},
 chapter = {Physical response of hyperelastic models for composite materials and soft tissues},
 id = {a6d03856-c131-3aa2-bb6a-8e8488a1657a},
 created = {2019-04-21T20:21:54.969Z},
 accessed = {2015-12-08},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-04-21T20:21:54.969Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Duong2017},
 language = {en},
 private_publication = {false},
 abstract = {A hyperelastic model must not only characterize the mechanical response of a composite material such as soft tissue, but also ensure numerical stability by a feasible set of material parameters. Apart from the well-known ill-conditioning problem caused by the incompressibility constraint, the paper indicates another ill-conditioning occurring in any general fibre-reinforced material model for tubular organs when unbalance between the fibre strain energy and the matrix strain energy becomes too large. Specifically, although the Holzapfel model is polyconvex, this problem can be observed as an unphysical behaviour in a physiological deformation range of a tissue such as arterial wall and intestine by thickening in the thickness direction associated with a volume growth of a specimen in a tension test. Particularly, the same problem for a polyconvex modified Fung-type model with the matrix characterized by the neo-Hookean model has been discussed for the first time. By investigating the influence of the shear modulus in these two models, we not only prove the cause of the ill-conditioning but also propose a solution to control the unbalance in the strain energy. The numerical results show significant enhancement of the model stability in overcoming the unphysical deformation.},
 bibtype = {inbook},
 author = {Duong, Minh Tuan and Nguyen, Nhu Huynh and Staat, Manfred and Nguyễn, Như Huynh and Staat, Manfred},
 doi = {10.1186/s40540-015-0015-x},
 title = {Advances in Composite Material}
}

A hyperelastic model must not only characterize the mechanical response of a composite material such as soft tissue, but also ensure numerical stability by a feasible set of material parameters. Apart from the well-known ill-conditioning problem caused by the incompressibility constraint, the paper indicates another ill-conditioning occurring in any general fibre-reinforced material model for tubular organs when unbalance between the fibre strain energy and the matrix strain energy becomes too large. Specifically, although the Holzapfel model is polyconvex, this problem can be observed as an unphysical behaviour in a physiological deformation range of a tissue such as arterial wall and intestine by thickening in the thickness direction associated with a volume growth of a specimen in a tension test. Particularly, the same problem for a polyconvex modified Fung-type model with the matrix characterized by the neo-Hookean model has been discussed for the first time. By investigating the influence of the shear modulus in these two models, we not only prove the cause of the ill-conditioning but also propose a solution to control the unbalance in the strain energy. The numerical results show significant enhancement of the model stability in overcoming the unphysical deformation.

@inproceedings{
 title = {Biomechanical simulation of different prosthetic meshes for repairing uterine/vaginal vault prolapse},
 type = {inproceedings},
 year = {2017},
 pages = {118-119},
 websites = {http://yra-medtech.de/daten_medtech/dokumente2017/YRA_Booklet_2017_LO.pdf,http://yra-medtech.de/daten_medtech/dokumente2017/IEEE_Workshop_2017_Abstracts.pdf},
 publisher = {University Duisburg-Essen},
 city = {Mühlheim a. d. Ruhr, Germany},
 id = {3ff664e6-e92c-3c42-a9b9-1c4b9eba8aa2},
 created = {2019-05-18T20:43:49.937Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.172Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jabbari2017},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Jabbari, Medisa and Bhattarai, Aroj and Anding, Ralf and Staat, Manfred},
 editor = {Erni, Daniel and Fischerauer, Alice and Himmel, Jörg and Seeger, Thomas and Thelen, Klaus},
 doi = {10.17185/duepublico/43984},
 booktitle = {2nd YRA MedTech Symposium, Young Researchers Academy – MedTech in NRW jointly held with the 7th IEEE Workshop & SENSORICA 2017}
}

@inproceedings{
 title = {Calculation of muscle forces and joint reaction loads in shoulder area via an OpenSim based computer calculation},
 type = {inproceedings},
 year = {2017},
 pages = {116-117},
 websites = {http://yra-medtech.de/daten_medtech/dokumente2017/YRA_Booklet_2017_LO.pdf,http://yra-medtech.de/daten_medtech/dokumente2017/IEEE_Workshop_2017_Abstracts.pdf},
 publisher = {University Duisburg-Essen},
 city = {Mühlheim a. d. Ruhr, Germany},
 id = {a5222794-f0ec-34eb-9dd1-a93fc5e6a4d7},
 created = {2019-05-19T06:57:44.592Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.172Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Birgel2017},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Birgel, Stefan and Leschinger, Tim and Wegmann, Kilian and Staat, Manfred},
 editor = {Erni, Daniel and Fischerauer, Alice and Himmel, Jörg and Seeger, Thomas and Thelen, Klaus},
 doi = {10.17185/duepublico/43984},
 booktitle = {2nd YRA MedTech Symposium, Young Researchers Academy – MedTech in NRW jointly held with the 7th IEEE Workshop & SENSORICA 2017}
}

@inproceedings{
 title = {Prevention of femur neck fractures through femoroplasty},
 type = {inproceedings},
 year = {2017},
 pages = {114-115},
 websites = {http://yra-medtech.de/daten_medtech/dokumente2017/YRA_Booklet_2017_LO.pdf,http://yra-medtech.de/daten_medtech/dokumente2017/IEEE_Workshop_2017_Abstracts.pdf},
 publisher = {University Duisburg-ssen},
 city = {Mühlheim a. d. Ruhr, Germany},
 id = {c09f16d1-27f8-3010-8f27-47b95b0f0ca9},
 created = {2019-05-19T06:57:44.598Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-08-05T12:12:01.329Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Abel2017},
 folder_uuids = {adee5ffe-7473-40f0-bc96-24e6feec7c9b},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Abel, Alexander and Pérez-Viana, Daniel and Ciritsis, Bernhard and Staat, Manfred},
 editor = {Erni, Daniel and Fischerauer, Alice and Himmel, Jörg and Seeger, Thomas and Thelen, Klaus},
 doi = {10.17185/duepublico/43984},
 booktitle = {2nd YRA MedTech Symposium, Young Researchers Academy – MedTech in NRW jointly held with the 7th IEEE Workshop & SENSORICA 2017}
}

@article{
 title = {Biomechanical modeling of macular hole formation and development},
 type = {article},
 year = {2017},
 pages = {3701},
 volume = {58},
 websites = {https://iovs.arvojournals.org/article.aspx?articleid=2638089},
 id = {13436bc1-ce18-3695-8bc3-c75197626898},
 created = {2020-02-15T22:12:47.437Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-02-15T22:45:46.936Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frank2017},
 private_publication = {false},
 abstract = {Purpose : A macular hole (MH) is a pathological full thickness retinal defect in the macular region (MR). Interestingly, a MH always possesses a circular shape in the retinal plane. Present assumptions on MH etiology refer to tangential or anterior-posterior tensile forces at the foveal region. Using biomechanical models, we investigated the impact of biomechanical factors in macular region on the MH formation and its circular shape. Methods : 2D- and 3D-finite-element models of MR were developed based on optical coherence tomography (OCT) volume scans of a healthy eye. The models consist of two elastic layers: the internal limiting membrane (ILM: E=0.147MPa) and the retina (E=0.431MPa). Both materials were modeled as linearly elastic and incompressible. In the ILM in MR a small ellipsoidal slit was constructed as a precursor to a macular hole. In the 3D model, the axial ratio (minor d /major axis b, see Figure) of the initial constructed slit was determined assuming physiological intraocular pressure (IOP) range. In the 2D model, tangential and anterior-posterior tensile forces were applied to the intact ILM at specific angular vitreal attachments (shearing angle ranged 0°-90°). Maximal principal strains were computed, which are likely candidates of causing failure in the tissue and thus MH formation. Results : Under physiological IOP-conditions, the 2D model of MR without an initial slit shows high strains exactly in the area, where the MH formation is observed clinically. Using the 3D model further simulations under the same conditions show that an initial slit turns into an oval shape with a tendency to become round. When additional forces were considered in the attachment region of the vitreous it was observed that maximal principal strains in MR become larger with smaller shearing angle under predominant tangential forces. Tangential forces become greater than tensile forces hence being potentially riskier for MH progression. Conclusions : The IOP as single factor is not alone responsible for the circular formation of a MH from an initial slit. However, forces, especially tangential ones, transferred by the detaching vitreous result in high principal strains in MR. This aspect in combination with weakened tissue might lead to MH formation. Biomechanical modelling can be a useful tool for the investigation of MH etiology as well for the early MH diagnostics and the prediction of its progression. This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.},
 bibtype = {article},
 author = {Frank, Anissa and Jung, Alexander and Staat, Manfred and Engelbert, Michael and Dashevsky, Alexey and Haritoglou, Christos and Maier, Mathias M and Kotliar, Konstantin E},
 journal = {Investigative Ophthalmology & Visual Science},
 number = {8}
}

Purpose : A macular hole (MH) is a pathological full thickness retinal defect in the macular region (MR). Interestingly, a MH always possesses a circular shape in the retinal plane. Present assumptions on MH etiology refer to tangential or anterior-posterior tensile forces at the foveal region. Using biomechanical models, we investigated the impact of biomechanical factors in macular region on the MH formation and its circular shape. Methods : 2D- and 3D-finite-element models of MR were developed based on optical coherence tomography (OCT) volume scans of a healthy eye. The models consist of two elastic layers: the internal limiting membrane (ILM: E=0.147MPa) and the retina (E=0.431MPa). Both materials were modeled as linearly elastic and incompressible. In the ILM in MR a small ellipsoidal slit was constructed as a precursor to a macular hole. In the 3D model, the axial ratio (minor d /major axis b, see Figure) of the initial constructed slit was determined assuming physiological intraocular pressure (IOP) range. In the 2D model, tangential and anterior-posterior tensile forces were applied to the intact ILM at specific angular vitreal attachments (shearing angle ranged 0°-90°). Maximal principal strains were computed, which are likely candidates of causing failure in the tissue and thus MH formation. Results : Under physiological IOP-conditions, the 2D model of MR without an initial slit shows high strains exactly in the area, where the MH formation is observed clinically. Using the 3D model further simulations under the same conditions show that an initial slit turns into an oval shape with a tendency to become round. When additional forces were considered in the attachment region of the vitreous it was observed that maximal principal strains in MR become larger with smaller shearing angle under predominant tangential forces. Tangential forces become greater than tensile forces hence being potentially riskier for MH progression. Conclusions : The IOP as single factor is not alone responsible for the circular formation of a MH from an initial slit. However, forces, especially tangential ones, transferred by the detaching vitreous result in high principal strains in MR. This aspect in combination with weakened tissue might lead to MH formation. Biomechanical modelling can be a useful tool for the investigation of MH etiology as well for the early MH diagnostics and the prediction of its progression. This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

@article{
 title = {Sample-specific adaption of an improved electro-mechanical model of in vitro cardiac tissue},
 type = {article},
 year = {2016},
 keywords = {Cardiac tissue,Computational biomechanics,Drug simulation,Electromechanical modeling,Frequency adaption,Hodgkin–Huxley models,Homogenization,hiPS cardiomyocytes},
 pages = {2428-2435},
 volume = {49},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0021929016301154,http://www.ncbi.nlm.nih.gov/pubmed/26972766},
 month = {8},
 day = {11},
 id = {27c2f85e-f2f6-3fdf-947f-0c15c99cb289},
 created = {2016-02-14T10:53:08.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:46:59.949Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2016},
 private_publication = {false},
 abstract = {We present an electromechanically coupled computational model for the investigation of a thin cardiac tissue construct consisting of human-induced pluripotent stem cell-derived atrial, ventricular and sinoatrial cardiomyocytes. The mechanical and electrophysiological parts of the finite element model, as well as their coupling are explained in detail. The model is implemented in the open source finite element code Code_Aster and is employed for the simulation of a thin circular membrane deflected by a monolayer of autonomously beating, circular, thin cardiac tissue. Two cardio-active drugs, S-Bay K8644 and veratridine, are applied in experiments and simulations and are investigated with respect to their chronotropic effects on the tissue. These results demonstrate the potential of coupled micro- and macroscopic electromechanical models of cardiac tissue to be adapted to experimental results at the cellular level. Further model improvements are discussed taking into account experimentally measurable quantities that can easily be extracted from the obtained experimental results. The goal is to estimate the potential to adapt the presented model to sample specific cell cultures.},
 bibtype = {article},
 author = {Frotscher, Ralf and Muanghong, Danita and Dursun, Gözde and Goßmann, Matthias and Temiz-Artmann, Ayşegül and Staat, Manfred},
 doi = {10.1016/j.jbiomech.2016.01.039},
 journal = {Journal of Biomechanics},
 number = {12}
}

We present an electromechanically coupled computational model for the investigation of a thin cardiac tissue construct consisting of human-induced pluripotent stem cell-derived atrial, ventricular and sinoatrial cardiomyocytes. The mechanical and electrophysiological parts of the finite element model, as well as their coupling are explained in detail. The model is implemented in the open source finite element code Code_Aster and is employed for the simulation of a thin circular membrane deflected by a monolayer of autonomously beating, circular, thin cardiac tissue. Two cardio-active drugs, S-Bay K8644 and veratridine, are applied in experiments and simulations and are investigated with respect to their chronotropic effects on the tissue. These results demonstrate the potential of coupled micro- and macroscopic electromechanical models of cardiac tissue to be adapted to experimental results at the cellular level. Further model improvements are discussed taking into account experimentally measurable quantities that can easily be extracted from the obtained experimental results. The goal is to estimate the potential to adapt the presented model to sample specific cell cultures.

@article{
 title = {Mechano-pharmacological characterization of cardiomyocytes derived from human induced pluripotent stem cells},
 type = {article},
 year = {2016},
 keywords = {Cardiac myocytes,CellDrum,Heart tissue culture,Induced pluripotent stem cells,Inotropic compounds,Ion channels,Pharmacology},
 pages = {1182-1198},
 volume = {38},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/26983082,http://www.karger.com/?doi=10.1159/000443124},
 month = {3},
 day = {17},
 id = {bc36fb82-76ca-3f42-a60f-151214e179f7},
 created = {2016-03-01T14:02:50.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:46:59.930Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Goßmann2016},
 private_publication = {false},
 abstract = {BACKGROUND/AIMS Common systems for the quantification of cellular contraction rely on animal-based models, complex experimental setups or indirect approaches. The herein presented CellDrum technology for testing mechanical tension of cellular monolayers and thin tissue constructs has the potential to scale-up mechanical testing towards medium-throughput analyses. Using hiPS-Cardiac Myocytes (hiPS-CMs) it represents a new perspective of drug testing and brings us closer to personalized drug medication. METHODS In the present study, monolayers of self-beating hiPS-CMs were grown on ultra-thin circular silicone membranes and deflect under the weight of the culture medium. Rhythmic contractions of the hiPS-CMs induced variations of the membrane deflection. The recorded contraction-relaxation-cycles were analyzed with respect to their amplitudes, durations, time integrals and frequencies. Besides unstimulated force and tensile stress, we investigated the effects of agonists and antagonists acting on Ca2+ channels (S-Bay K8644/verapamil) and Na+ channels (veratridine/lidocaine). RESULTS The measured data and simulations for pharmacologically unstimulated contraction resembled findings in native human heart tissue, while the pharmacological dose-response curves were highly accurate and consistent with reference data. CONCLUSION We conclude that the combination of the CellDrum with hiPS-CMs offers a fast, facile and precise system for pharmacological, toxicological studies and offers new preclinical basic research potential.},
 bibtype = {article},
 author = {Goßmann, Matthias and Frotscher, Ralf and Linder, Peter and Neumann, Stephan and Bayer, Robin and Epple, Matthias and Staat, Manfred and Artmann, Aysegül and Artmann, Gerhard M.},
 doi = {10.1159/000443124},
 journal = {Cellular Physiology and Biochemistry},
 number = {3}
}

BACKGROUND/AIMS Common systems for the quantification of cellular contraction rely on animal-based models, complex experimental setups or indirect approaches. The herein presented CellDrum technology for testing mechanical tension of cellular monolayers and thin tissue constructs has the potential to scale-up mechanical testing towards medium-throughput analyses. Using hiPS-Cardiac Myocytes (hiPS-CMs) it represents a new perspective of drug testing and brings us closer to personalized drug medication. METHODS In the present study, monolayers of self-beating hiPS-CMs were grown on ultra-thin circular silicone membranes and deflect under the weight of the culture medium. Rhythmic contractions of the hiPS-CMs induced variations of the membrane deflection. The recorded contraction-relaxation-cycles were analyzed with respect to their amplitudes, durations, time integrals and frequencies. Besides unstimulated force and tensile stress, we investigated the effects of agonists and antagonists acting on Ca2+ channels (S-Bay K8644/verapamil) and Na+ channels (veratridine/lidocaine). RESULTS The measured data and simulations for pharmacologically unstimulated contraction resembled findings in native human heart tissue, while the pharmacological dose-response curves were highly accurate and consistent with reference data. CONCLUSION We conclude that the combination of the CellDrum with hiPS-CMs offers a fast, facile and precise system for pharmacological, toxicological studies and offers new preclinical basic research potential.

@article{
 title = {Reconstruction of the interosseous membrane in the Essex Lopresti lesion - a biomechanical evaluation},
 type = {article},
 year = {2016},
 pages = {S130-S131},
 volume = {24},
 websites = {http://link.springer.com/10.1007/s00167-016-4080-7},
 month = {5},
 day = {18},
 id = {0f364c6a-044e-3fcc-a2d1-47682e05e04d},
 created = {2016-05-11T10:54:25.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-29T21:54:46.048Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2016a},
 private_publication = {false},
 bibtype = {article},
 author = {Hackl, Michael and Leschinger, Tim and Staat, Manfred and Müller, Lars Peter and Wegmann, Kilian},
 doi = {10.1007/s00167-016-4080-7},
 journal = {Knee Surgery, Sports Traumatology, Arthroscopy},
 number = {S1}
}

@article{
 title = {Proximal phalangeal neck fractures of the hand - a biomechanical comparison of three fixation techniques},
 type = {article},
 year = {2016},
 pages = {S148-S149},
 volume = {24},
 websites = {http://link.springer.com/10.1007/s00167-016-4080-7},
 month = {5},
 day = {18},
 id = {4fa12338-f72a-37f0-a5ca-597678c035ee},
 created = {2016-05-11T10:54:25.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2016b},
 private_publication = {false},
 bibtype = {article},
 author = {Hackl, Michael and Müller, Lars Peter and Staat, Manfred and Kahmann, Stepahine Lucina and Wegmann, Kilian},
 doi = {10.1007/s00167-016-4080-7},
 journal = {Knee Surgery, Sports Traumatology, Arthroscopy},
 number = {S1}
}

@article{
 title = {Shortening osteotomy of the proximal radius - a treatment option for isolated osteoarthritis of the lateral column of the elbow joint},
 type = {article},
 year = {2016},
 pages = {S128-S129},
 volume = {24},
 websites = {http://link.springer.com/10.1007/s00167-016-4080-7},
 month = {5},
 day = {18},
 id = {1bb1eb93-2e02-310d-a2a3-497396dd25b8},
 created = {2016-05-11T11:06:57.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Hackl2016},
 private_publication = {false},
 bibtype = {article},
 author = {Hackl, Michael and Kahmann, Stepahine Lucina and Wegmann, Kilian and Ries, Christian and Staat, Manfred and Müller, Lars Peter},
 doi = {10.1007/s00167-016-4080-7},
 journal = {Knee Surgery, Sports Traumatology, Arthroscopy},
 number = {S1}
}

@article{
 title = {Double plate osteosynthesis of proximal ulna fractures: biomechanical and clinical results},
 type = {article},
 year = {2016},
 pages = {S58-S59},
 volume = {24},
 websites = {http://link.springer.com/10.1007/s00167-016-4079-0},
 month = {5},
 day = {13},
 id = {c6f37748-411b-3383-b8c0-734e484181b9},
 created = {2016-05-11T11:06:57.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Wegmann2016},
 private_publication = {false},
 bibtype = {article},
 author = {Wegmann, Kilian and Hackl, Michael and Staat, Manfred and Mayer, Katharina and Müller, Lars Peter},
 doi = {10.1007/s00167-016-4079-0},
 journal = {Knee Surgery, Sports Traumatology, Arthroscopy},
 number = {S1}
}

@inproceedings{
 title = {A 3D electromechanical FEM-based model for cardiac tissue},
 type = {inproceedings},
 year = {2016},
 keywords = {Cardiac Tissue,Cell Models,Drug Modeling,Electromechanical Coupling},
 pages = {63-73},
 websites = {https://www.eccomas2016.org/proceedings/pdf/11367.pdf,http://www.eccomasproceedia.org/conferences/eccomas-congresses/eccomas-congress-2016/1791},
 publisher = {Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece},
 city = {Athens},
 id = {5a9f097c-2986-3b36-9b05-c2e8cbdd6cff},
 created = {2016-09-06T20:32:58.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-06-03T22:57:04.796Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Duong2016},
 private_publication = {false},
 abstract = {The CellDrum provides an experimental setup to investigate the electromechanics of a cardiac tissue construct and particularly the effect of drugs. Experimental data were used to develop a respective computational electromechanical model. Until now, the experiments have been performed with a thin tissue construct. Mechanically, it was modeled as a materially and geometrically nonlinear shell. Future experiments with thicker tissue are planned. Thus, the mechanical model needs to be modified. This study aims to predict the outcome of such experiments using a nonlinear 3D continuum formulation. Here, the action of one drug, verapamil, was taken into account.},
 bibtype = {inproceedings},
 author = {Duong, Minh Tuan and Jung, Alexander and Frotscher, Ralf and Staat, Manfred},
 editor = {Papadrakakis, Manolis and Papadopoulos, Vissarion and Stefanou, George and Plevris, Vagelis},
 doi = {10.7712/100016.1791.11367},
 booktitle = {Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)}
}

The CellDrum provides an experimental setup to investigate the electromechanics of a cardiac tissue construct and particularly the effect of drugs. Experimental data were used to develop a respective computational electromechanical model. Until now, the experiments have been performed with a thin tissue construct. Mechanically, it was modeled as a materially and geometrically nonlinear shell. Future experiments with thicker tissue are planned. Thus, the mechanical model needs to be modified. This study aims to predict the outcome of such experiments using a nonlinear 3D continuum formulation. Here, the action of one drug, verapamil, was taken into account.

@inproceedings{
 title = {Shakedown analysis of plate bending under stochastic uncertainty by chance constrained programming},
 type = {inproceedings},
 year = {2016},
 keywords = {Limit analysis,Shakedown analysis,chance constrained programming,non-linear programming,stochastic programming},
 pages = {3007-3019},
 websites = {https://www.eccomas2016.org/proceedings/pdf/11106.pdf,http://www.eccomasproceedia.org/conferences/eccomas-congresses/eccomas-congress-2016/2012},
 publisher = {Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece},
 city = {Athens},
 id = {8bfff788-7316-3b1c-b398-27edff1cf02f},
 created = {2016-09-06T20:41:35.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-22T14:16:34.846Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Tran2016a},
 private_publication = {false},
 abstract = {In this paper we propose a stochastic programming to analyze limit and shakedown of plate bending under uncertainty conditions of strength. The Kirchhoff plate theory is used to formulate chance constrained problems. Based on the duality theory, the shakedown load multiplier formulated by the kinematic theorem is proved actually to be the dual form of the shakedown load multiplier for-mulated by static theorem. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit.},
 bibtype = {inproceedings},
 author = {Tran, Ngoc Trinh and Tran, Thanh Ngoc and Matthies, H.G. and Stavroulakis, G.E. and Staat, Manfred},
 editor = {Papadopoulos, V. and Stefanou, G. and Plevris, V.},
 doi = {10.7712/100016.2012.11106},
 booktitle = {Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)}
}

In this paper we propose a stochastic programming to analyze limit and shakedown of plate bending under uncertainty conditions of strength. The Kirchhoff plate theory is used to formulate chance constrained problems. Based on the duality theory, the shakedown load multiplier formulated by the kinematic theorem is proved actually to be the dual form of the shakedown load multiplier for-mulated by static theorem. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit.

@inbook{
 type = {inbook},
 year = {2016},
 keywords = {Muscle fibres,passive relaxation,pelvic dysfunction},
 pages = {185-188},
 websites = {http://www.crcnetbase.com/doi/pdfplus/10.1201/9781315644622-47},
 publisher = {CRC Press/Balkema},
 city = {London},
 id = {443d4b46-a4bc-3298-a2be-4c63097d07f1},
 created = {2016-09-07T19:56:44.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-28T11:55:30.334Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2016},
 private_publication = {false},
 abstract = {A perfect tone of the pelvic muscle fibres elevates the pelvic organs and maintains the urinary and fecal continence. Prosthetic mesh implants are widely used to reconstruct the pelvic floor dysfunctions due to damaged muscle fibres. This paper focuses on the muscle fibre orientation to simulate the passive stretching of the pelvic muscles under increased intra-abdominal pressure (IAP) during Valsalva maneuver. The Humphrey model is adopted for the passive deformation of the pelvic muscle. With a pressure of 0.2 kPa applied on the internal faces of the muscle, the levator ani (LA) muscle displaces 27.917 mm inferiorly. High stress is observed at the fixation of the muscle to the pubic bones. Without any supports from the anal plate and the perineal body, the posterior movement of the LA muscle is 11.640 mm which is almost 2.5 times larger than that observed from the MRI examination of a nulliparous female.},
 bibtype = {inbook},
 author = {Bhattarai, Aroj and Frotscher, Ralf and Staat, Manfred},
 editor = {Jorge, Renato Natal and Mascarenhas, Teresa and Duarte, José Alberto and Ramos, Isabel and Costa, Maria Emília and Figueiral, Maria Helena and Pinho, Olívia and Brandão, Sofia and Roza, Thuane Da and Tavares, João Manuel R.S.},
 chapter = {Significance of fibre geometry on passive-active response of pelvic muscles to evaluate pelvic dysfunction},
 title = {BioMedWomen: Proceedings of the International Conference on Clinical and BioEngineering for Women's Health (Porto, Portugal, 20-23 June, 2015)}
}

A perfect tone of the pelvic muscle fibres elevates the pelvic organs and maintains the urinary and fecal continence. Prosthetic mesh implants are widely used to reconstruct the pelvic floor dysfunctions due to damaged muscle fibres. This paper focuses on the muscle fibre orientation to simulate the passive stretching of the pelvic muscles under increased intra-abdominal pressure (IAP) during Valsalva maneuver. The Humphrey model is adopted for the passive deformation of the pelvic muscle. With a pressure of 0.2 kPa applied on the internal faces of the muscle, the levator ani (LA) muscle displaces 27.917 mm inferiorly. High stress is observed at the fixation of the muscle to the pubic bones. Without any supports from the anal plate and the perineal body, the posterior movement of the LA muscle is 11.640 mm which is almost 2.5 times larger than that observed from the MRI examination of a nulliparous female.

@article{
 title = {FEM Shakedown of uncertain structures by chance constrained programming},
 type = {article},
 year = {2016},
 pages = {715-716},
 volume = {16},
 websites = {http://doi.wiley.com/10.1002/pamm.201610346},
 month = {10},
 id = {3bbfdc1d-5346-3c7b-b4e5-dfe2c6390ff6},
 created = {2016-10-28T14:53:24.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:46:59.823Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Tran2016},
 private_publication = {false},
 abstract = {We present a new primal-dual numerical algorithm of the shakedown problem under uncertainty in which the material strength is considered as a normally distributed random variable. Using chance constrained programming, we obtain deterministic equivalent formulations based on upper bound and lower bound theorems which are dual to each other. The proposed algorithm is tested in numerical examples which are applied to civil engineering structures. The obtained solutions show good performance.},
 bibtype = {article},
 author = {Tran, Ngoc Trinh and Tran, Thanh Ngoc and Matthies, Hermann G. and Stavroulakis, Georgios Eleftherios and Staat, Manfred},
 doi = {10.1002/pamm.201610346},
 journal = {PAMM · Proceedings in Applied Mathematics and Mechanics},
 number = {1}
}

We present a new primal-dual numerical algorithm of the shakedown problem under uncertainty in which the material strength is considered as a normally distributed random variable. Using chance constrained programming, we obtain deterministic equivalent formulations based on upper bound and lower bound theorems which are dual to each other. The proposed algorithm is tested in numerical examples which are applied to civil engineering structures. The obtained solutions show good performance.

@inproceedings{
 title = {Smoothed finite element methods for nonlinear solid mechanics problems: 2D and 3D case studies},
 type = {inproceedings},
 year = {2016},
 pages = {440-445},
 publisher = {Hanoi University of Science and Technology},
 city = {Hanoi, Vietnam},
 id = {3c218c6d-3708-378f-a389-dba43c7b2eea},
 created = {2016-10-28T15:04:21.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-06-08T10:52:22.225Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2016},
 private_publication = {false},
 abstract = {The Smoothed Finite Element Method (SFEM) is presented as an edge-based and a facebased techniques for 2D and 3D boundary value problems, respectively. SFEMs avoid shortcomings of the standard Finite Element Method (FEM) with lower order elements such as overly stiff behavior, poor stress solution, and locking effects. Based on the idea of averaging spatially the standard strain field of the FEM over so-called smoothing domains SFEM calculates the stiffness matrix for the same number of degrees of freedom (DOFs) as those of the FEM. However, the SFEMs significantly improve accuracy and convergence even for distorted meshes and/or nearly incompressible materials. Numerical results of the SFEMs for a cardiac tissue membrane (thin plate inflation) and an artery (tension of 3D tube) show clearly their advantageous properties in improving accuracy particularly for the distorted meshes and avoiding shear locking effects.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Dương, Minh Tuấn},
 doi = {10.21269/7859},
 booktitle = {Proceedings of the National Science and Technology Conference on Mechanical - Transportation Engineering (NSCMET 2016)}
}

The Smoothed Finite Element Method (SFEM) is presented as an edge-based and a facebased techniques for 2D and 3D boundary value problems, respectively. SFEMs avoid shortcomings of the standard Finite Element Method (FEM) with lower order elements such as overly stiff behavior, poor stress solution, and locking effects. Based on the idea of averaging spatially the standard strain field of the FEM over so-called smoothing domains SFEM calculates the stiffness matrix for the same number of degrees of freedom (DOFs) as those of the FEM. However, the SFEMs significantly improve accuracy and convergence even for distorted meshes and/or nearly incompressible materials. Numerical results of the SFEMs for a cardiac tissue membrane (thin plate inflation) and an artery (tension of 3D tube) show clearly their advantageous properties in improving accuracy particularly for the distorted meshes and avoiding shear locking effects.

@inproceedings{
 title = {Impact of a proximal radial shortening osteotomy on the distribution of forces and the stability of the elbow},
 type = {inproceedings},
 year = {2016},
 pages = {7-8},
 websites = {http://yra-medtech.de/daten_medtech/22_YRA_S_2016_FH_Aachen_Kahmann.pdf},
 publisher = {University Duisburg-Essen},
 city = {Duisburg, Germany},
 id = {c48f7e52-a81b-326f-a373-7e98567e2ee1},
 created = {2018-04-01T19:17:45.933Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.192Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Kahmann2016},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Kahmann, Stefanie and Hackl, Michael and Wegmann, Kilian and Müller, L.-P. and Staat, Manfred},
 editor = {Erni, Daniel},
 doi = {10.17185/duepublico/40821},
 booktitle = {1st YRA MedTech Symposium, Young Researchers Academy – MedTech in NRW}
}

@inproceedings{
 title = {Female pelvic floor dysfunction: progressive weakening of the support system},
 type = {inproceedings},
 year = {2016},
 pages = {11-12},
 websites = {http://yra-medtech.de/daten_medtech/7_YRA_S_2016_FH_Aachen_Bhattarai.pdf},
 publisher = {University Duisburg-Essen},
 city = {Duisburg, Germany},
 id = {7aa4ae04-3290-3efa-8800-58dfba41c63e},
 created = {2018-04-01T19:17:45.941Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.163Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2016},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Bhattarai, Aroj and Staat, Manfred},
 editor = {Erni, Daniel},
 doi = {10.17185/duepublico/40821},
 booktitle = {1st YRA MedTech Symposium, Young Researchers Academy – MedTech in NRW}
}

@inproceedings{
 title = {Computing Olympic gold: Ski jumping as an example},
 type = {inproceedings},
 year = {2016},
 pages = {54-55},
 websites = {http://yra-medtech.de/daten_medtech/1_YRA_S_2016_FH_Aachen_Jung.pdf},
 publisher = {University Duisburg-Essen},
 city = {Duisburg, Germany},
 id = {84d023d6-f8e5-314f-ad2a-4cbeda344cf9},
 created = {2018-04-01T19:17:45.946Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-11-01T20:13:48.250Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2016},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Jung, Alexander and Staat, Manfred and Müller, Wolfram},
 editor = {Erni, Daniel},
 doi = {10.17185/duepublico/40821},
 booktitle = {1st YRA MedTech Symposium, Young Researchers Academy – MedTech in NRW}
}

@techreport{
 title = {Schlussbericht zu BINGO: Optimierung des Systems Netzimplantat-Beckenboden zur therapeutischen Gewebeverstärkung nach der Integraltheorie [Final report on BINGO: Optimization of the system surgical mesh-implant and pelvic floor for therapeutic tissue rein},
 type = {techreport},
 year = {2016},
 keywords = {Beckenbodenfunktionsstörung,Finite-Elemente-Methode,Implantat,Netz,Rekonstruktion},
 pages = {35},
 websites = {https://edocs.tib.eu/files/e01fb17/881343862.pdf},
 institution = {FH Aachen, Technische Informationsbibliothek (TIB)},
 id = {19192cc8-97a8-3f23-bb34-3f0f4b3cb358},
 created = {2019-03-18T19:45:23.282Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-09-13T15:02:54.855Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2016},
 private_publication = {false},
 bibtype = {techreport},
 author = {Bhattarai, Aroj and Frotscher, Ralf and Dương, Minh Tuấn and Staat, Manfred},
 doi = {10.2314/GBV:881343862}
}

@inbook{
 type = {inbook},
 year = {2015},
 keywords = {Limit Analysis,Multimode Failure,Non-linear Optimization,Reliability Analysis,Shakedown Analysis},
 pages = {279-298},
 volume = {4},
 websites = {http://link.springer.com/10.1007/978-3-319-12928-0,http://link.springer.com/10.1007/978-3-319-12928-0_14},
 publisher = {Springer International Publishing},
 city = {Cham},
 chapter = {Uncertainty multimode failure and shakedown analysis of shells},
 id = {0878f54e-5e18-3150-aa9e-a41d9376b826},
 created = {2014-07-05T06:22:30.000Z},
 accessed = {2015-01-12},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {directmeth2015},
 source_type = {incollection},
 private_publication = {false},
 abstract = {This paper presents a numerical procedure for reliability analysis of thin plates and shells with respect to plastic collapse or to inadaptation. The procedure involves a deterministic shakedown analysis for each probabilistic iteration, which is based on the upper bound approach and the use of the exact Ilyushin yield surface. Probabilistic shakedown analysis deals with uncertain-ties originated from the loads, material strength and thickness of the shell. Based on a direct definition of the limit state function, the calculation of the failure probability may be solved efficiently solved by using the First and Second Order Reliability Methods (FORM and SORM). The problem of reliability of structural systems (series systems) will be handled by the application of a special technique, which permits to find all the design points correspond-ing to all the failure modes. Studies show, in this case, that it improves con-siderably the FORM and SORM results.},
 bibtype = {inbook},
 author = {Trần, Thanh Ngọc and Staat, Manfred},
 editor = {Fuschi, Paolo and Pisano, Aurora Angela and Weichert, Dieter},
 doi = {10.1007/978-3-319-12928-0_14},
 title = {Direct Methods for Limit and Shakedown Analysis of Structures}
}

This paper presents a numerical procedure for reliability analysis of thin plates and shells with respect to plastic collapse or to inadaptation. The procedure involves a deterministic shakedown analysis for each probabilistic iteration, which is based on the upper bound approach and the use of the exact Ilyushin yield surface. Probabilistic shakedown analysis deals with uncertain-ties originated from the loads, material strength and thickness of the shell. Based on a direct definition of the limit state function, the calculation of the failure probability may be solved efficiently solved by using the First and Second Order Reliability Methods (FORM and SORM). The problem of reliability of structural systems (series systems) will be handled by the application of a special technique, which permits to find all the design points correspond-ing to all the failure modes. Studies show, in this case, that it improves con-siderably the FORM and SORM results.

@article{
 title = {Computational investigation of drug action on human-induced stem cell-derived cardiomyocytes},
 type = {article},
 year = {2015},
 pages = {071002},
 volume = {137},
 websites = {http://biomechanical.asmedigitalcollection.asme.org/article.aspx?doi=10.1115/1.4030173,http://www.ncbi.nlm.nih.gov/pubmed/25807216},
 month = {7},
 day = {1},
 id = {9026301c-e1ee-3b2c-8404-c279efe424e4},
 created = {2015-06-08T14:34:55.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2015a},
 private_publication = {false},
 abstract = {We compare experimental and computational results for the actions of the cardioactive drugs Lidocaine, Verapamil, Veratridine and Bay K 8644 on a tissue monolayer consisting of mainly fibroblasts and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSc-CM). The choice of the computational models is justified and literature data is collected to model drug action as accurately as possible. The focus of this work is to evaluate the validity and capability of existing models for native human cells with respect to the simulation of pharmaceutical treatment of monolayers and hiPSc-CM. From the comparison of experimental and computational results we derive suggestions for model improvements which are intended to computationally support the interpretation of experimental results obtained for hiPSc-CM.},
 bibtype = {article},
 author = {Frotscher, Ralf and Koch, Jan-Peter and Staat, Manfred},
 doi = {10.1115/1.4030173},
 journal = {Journal of Biomechanical Engineering},
 number = {7}
}

We compare experimental and computational results for the actions of the cardioactive drugs Lidocaine, Verapamil, Veratridine and Bay K 8644 on a tissue monolayer consisting of mainly fibroblasts and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSc-CM). The choice of the computational models is justified and literature data is collected to model drug action as accurately as possible. The focus of this work is to evaluate the validity and capability of existing models for native human cells with respect to the simulation of pharmaceutical treatment of monolayers and hiPSc-CM. From the comparison of experimental and computational results we derive suggestions for model improvements which are intended to computationally support the interpretation of experimental results obtained for hiPSc-CM.

@inproceedings{
 title = {Modeling and simulation of a growing mass by the Smoothed Finite Element Method (SFEM)},
 type = {inproceedings},
 year = {2015},
 keywords = {Constitutive Modeling,Face-based SFEM,Growing mass,Growth Modeling,SFEM},
 city = {Aachen, Germany},
 id = {15d6267c-2cf1-3ae7-9a3b-08601cbd762b},
 created = {2015-07-25T15:26:18.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Duong2015b},
 private_publication = {false},
 abstract = {Modeling of a growing mass like soft tissue becomes more essential in biomechanical applications such as mesh implants, tissue replacements or stents in arteries. It could be hypothesised that growth and remodelling may cause problems such as aneurisms and herniae. The paper presents growth modeling using a multiplicative decomposition of the deformation gradient into the growth part and the elastic term. Stretch ratios in growth tensors are introduced as internal variables at the integration point level in the finite element setting. Isotropic and transversely isotropic growth models are implemented into the open source program Code Aster. The growth problems are solved by adopting a Face-based Smoothed Finite Element Method (FS-FEM). To this end, internal variables of the growth models are modified properly, the growth tensors are smoothed, and the implicit Euler scheme for the stretch ratios is utilized. The FS-FEM can improve some existing problems which the standard Finite Element Method (FEM) such as the well-known overly stiff behavior and poor stress solution.},
 bibtype = {inproceedings},
 author = {Duong, Minh Tuan and Nguyễn, Như Huynh and Staat, Manfred},
 booktitle = {YIC GACM 2015, 3rd ECCOMAS Young Investigators Conference, 6th GACM Colloquium, Aachen, Germany, July 20-23, 2015}
}

Modeling of a growing mass like soft tissue becomes more essential in biomechanical applications such as mesh implants, tissue replacements or stents in arteries. It could be hypothesised that growth and remodelling may cause problems such as aneurisms and herniae. The paper presents growth modeling using a multiplicative decomposition of the deformation gradient into the growth part and the elastic term. Stretch ratios in growth tensors are introduced as internal variables at the integration point level in the finite element setting. Isotropic and transversely isotropic growth models are implemented into the open source program Code Aster. The growth problems are solved by adopting a Face-based Smoothed Finite Element Method (FS-FEM). To this end, internal variables of the growth models are modified properly, the growth tensors are smoothed, and the implicit Euler scheme for the stretch ratios is utilized. The FS-FEM can improve some existing problems which the standard Finite Element Method (FEM) such as the well-known overly stiff behavior and poor stress solution.

@inproceedings{
 title = {Biomechanical study of the female pelvic floor dysfunction using the finite element method},
 type = {inproceedings},
 year = {2015},
 keywords = {Finite Element Method,Integral Theory,Pelvic Floor Dysfunction,Urinary Incontinence},
 city = {Aachen, Germany},
 id = {2b1e846e-1af6-32cb-81df-73e7e7e41bb2},
 created = {2015-07-25T15:26:18.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2015a},
 private_publication = {false},
 abstract = {Pelvic floor dysfunction is considered to be a long run sequel of injuries of the weak pelvic supporting structures during vaginal delivery and their laxity in old age. Besides immediate effects, it becomes a socially embarrassing health issue in the form of incontinence and prolapse. To validate such clinical outcomes and to highlight the importance of supporting ligaments and fascias in the maintenance of continence as suggested Petros’ integral theory, computational studies are carried out on a 3D finite element pelvic floor model.},
 bibtype = {inproceedings},
 author = {Bhattarai, Aroj and Frotscher, Ralf and Staat, Manfred},
 booktitle = {YIC GACM 2015, 3rd ECCOMAS Young Investigators Conference, 6th GACM Colloquium, Aachen, Germany, July 20-23, 2015}
}

Pelvic floor dysfunction is considered to be a long run sequel of injuries of the weak pelvic supporting structures during vaginal delivery and their laxity in old age. Besides immediate effects, it becomes a socially embarrassing health issue in the form of incontinence and prolapse. To validate such clinical outcomes and to highlight the importance of supporting ligaments and fascias in the maintenance of continence as suggested Petros’ integral theory, computational studies are carried out on a 3D finite element pelvic floor model.

@inproceedings{
 title = {A simplification for shakedown analysis of hardening structures},
 type = {inproceedings},
 year = {2015},
 keywords = {Dual algorithm,Kinematic hardening,Shakedown,Upper bound},
 city = {Aachen, Germany},
 id = {c2c77c68-a5b5-3127-b10e-c45e948137e5},
 created = {2015-07-25T15:26:18.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Pham2015},
 private_publication = {false},
 abstract = {This paper introduces a simplified way to determine the shakedown load multiplier of bounded linearly kinematic hardening structures. The simplification is based on the shakedown solution for elastic-perfectly plastic structures. The numerical results show that the simplified way gives good results, compared to results from upper bound shakedown algorithm for bounded linearly kinematic hardening structures.},
 bibtype = {inproceedings},
 author = {Phạm, Phú Tình and Staat, Manfred},
 booktitle = {YIC GACM 2015, 3rd ECCOMAS Young Investigators Conference, 6th GACM Colloquium, Aachen, Germany, July 20-23, 2015}
}

This paper introduces a simplified way to determine the shakedown load multiplier of bounded linearly kinematic hardening structures. The simplification is based on the shakedown solution for elastic-perfectly plastic structures. The numerical results show that the simplified way gives good results, compared to results from upper bound shakedown algorithm for bounded linearly kinematic hardening structures.

@inproceedings{
 title = {An electromechanical model for cardiac tissue constructs},
 type = {inproceedings},
 year = {2015},
 keywords = {cardiac tissue,electro-mechanical coupling,finite element method},
 websites = {http://nbn-resolving.de/urn:nbn:de:hbz:82-rwth-2015-039806},
 publisher = {RWTH Aachen},
 city = {Aachen, Germany},
 id = {183fd0ac-5bbd-35f7-8832-d5f86adaa113},
 created = {2015-07-25T15:26:18.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2015},
 private_publication = {false},
 abstract = {The presented work computationally investigates cardiac tissue constructs, so-called engineered heart tissues, that consist of a collagen-based extracellular matrix and human-induced pluripotent stem-cell derived cardiomyocytes. A finite element model is built in order to support the interpretation of experimental results and to predict for instance the effect of drug application to the tissue. The electro-mechanically coupled model proves to be useful by means of elucidating macroscopic experimental results at the microscopic level.},
 bibtype = {inproceedings},
 author = {Frotscher, Ralf and Staat, Manfred},
 editor = {Elgeti, S. and Simon, J.-W.},
 booktitle = {YIC GACM 2015, 3rd ECCOMAS Young Investigators Conference, 6th GACM Colloquium, Aachen, Germany, July 20-23, 2015}
}

The presented work computationally investigates cardiac tissue constructs, so-called engineered heart tissues, that consist of a collagen-based extracellular matrix and human-induced pluripotent stem-cell derived cardiomyocytes. A finite element model is built in order to support the interpretation of experimental results and to predict for instance the effect of drug application to the tissue. The electro-mechanically coupled model proves to be useful by means of elucidating macroscopic experimental results at the microscopic level.

@inbook{
 type = {inbook},
 year = {2015},
 keywords = {cardiac tissue modeling,electromechanical coupling,homogenization},
 websites = {http://opus.bibliothek.fh-aachen.de/opus4/files/7263/CMBE2015_Staat_Frotscher.pdf},
 publisher = {CMBE Zeta Computational Resources Ltd., Swansea, UK},
 id = {af1389a1-0e01-3c9c-9110-46313912aa7c},
 created = {2015-07-25T22:17:17.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-27T10:54:39.636Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2015c},
 private_publication = {false},
 abstract = {We extend the modeling of a cardiac tissue composite by proper homogenization of all the different mechanical contributions to the constitutive tensor as well as the contributions to the diffusion tensor and the electrical source current in the parabolic system. The model is applied to support the interpretation of experimental findings in drug testing being able to explain the results at the cellular level. Moreover the model can be used for the prediction of drug effects on cardiac tissue and for computational studies of cardiomyocyte and cardiac tissue electromechanics.},
 bibtype = {inbook},
 author = {Frotscher, Ralf and Staat, Manfred},
 editor = {Nithiarasu, Perumal and Budyn, Elisa},
 chapter = {Homogenization of a cardiac tissue construct},
 title = {4th International Conference on Computational and Mathematical Biomedical Engineering - CMBE2015, 29 June - 1 July 2015, Cachan (Paris), France}
}

We extend the modeling of a cardiac tissue composite by proper homogenization of all the different mechanical contributions to the constitutive tensor as well as the contributions to the diffusion tensor and the electrical source current in the parabolic system. The model is applied to support the interpretation of experimental findings in drug testing being able to explain the results at the cellular level. Moreover the model can be used for the prediction of drug effects on cardiac tissue and for computational studies of cardiomyocyte and cardiac tissue electromechanics.

@inproceedings{
 title = {Effect of wind on flight style optimisation in ski jumping},
 type = {inproceedings},
 year = {2015},
 id = {a3c55746-1ca0-35ec-af02-6c6d83b5821e},
 created = {2015-07-25T22:17:17.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2015},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Jung, Alexander and Staat, Manfred and Müller, Wolfram},
 booktitle = {XV International Symposium on Computer Simulation in Biomechanics, July 9th-11th 2015, Edinburgh, UK}
}

@inproceedings{
 title = {Adjustment of computational models of cardiomyocytes with respect to the beating frequency},
 type = {inproceedings},
 year = {2015},
 pages = {40-41},
 publisher = {Deutsche Gesellschaft für Biomechanik},
 id = {48b034e9-33b7-33f8-9190-29b8fd9544ad},
 created = {2015-07-25T22:17:17.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2015b},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Frotscher, Ralf and Muanghong, Danita and Goßmann, Matthias and Temiz-Artmann, Ayşegül and Staat, Manfred},
 booktitle = {9. Jahrestagung der Deutschen Gesellschaft für Biomechanik, 06.-08. Mai 2015, Bonn}
}

@inproceedings{
 title = {Numerical simulation of urinary incontinence: urethral relocation using surgical mesh implants},
 type = {inproceedings},
 year = {2015},
 pages = {88},
 publisher = {Deutschen Gesellschaft für Biomechanik},
 city = {Bonn, Germany},
 id = {da175e52-d029-39b4-aa20-c72e8af5de23},
 created = {2015-07-25T22:17:17.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Bhattarai2015},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Bhattarai, Aroj and Frotscher, Ralf and Duong, Minh Tuan and Staat, Manfred},
 booktitle = {9. Jahrestagung der Deutschen Gesellschaft für Biomechanik, 06.-08. Mai 2015, Bonn}
}

@inproceedings{
 title = {Femoroplasty: fracture test, optical strain measurement and FE analysis},
 type = {inproceedings},
 year = {2015},
 pages = {8-9},
 publisher = {Deutschen Gesellschaft für Biomechanik},
 city = {Bonn, Germany},
 id = {791df087-aa24-3adc-954e-5e6d6e5d59b4},
 created = {2015-07-25T22:17:17.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-08-05T12:12:01.166Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Ciritsis2015},
 folder_uuids = {adee5ffe-7473-40f0-bc96-24e6feec7c9b},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Ciritsis, Bernhard and Simmen, H-P and Pérez-Viana, Daniel and Ciritsis, Alexander and Prescher, Andreas and Staat, Manfred},
 booktitle = {9. Jahrestagung der Deutschen Gesellschaft für Biomechanik, 06.-08. Mai 2015, Bonn}
}

@article{
 title = {Influence of refrigerated storage on tensile mechanical properties of porcine liver and spleen},
 type = {article},
 year = {2015},
 keywords = {autolysis,freeze-thaw,liver,refrigerated storage,spleen},
 pages = {79-88},
 volume = {2},
 websites = {http://www.tandfonline.com/doi/full/10.1080/23335432.2015.1049295},
 month = {1},
 id = {265e8bb8-b1ed-317b-b21a-72f180319bc0},
 created = {2015-08-07T15:42:37.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Duong2015},
 private_publication = {false},
 abstract = {Preservation conditions may affect internal organs thus influencing the results of protracted biomechanical tests. The influence of the freeze-thaw cycle on the mechanical behaviour of porcine abdominal organs was reported in our previous work. Here we further investigate the effects of refrigerated storage on the mechanical properties of porcine spleen and liver. Twenty-seven swine were chosen for tensile testing. To simulate the conservation conditions before biomechanical experimentation, the total sample was divided into three groups of nine individuals each and tested in a fresh state, after a freeze-thaw cycle, and after refrigerated storage (+4 °C). Fitted stress-stretch curves for each tissue type were obtained by employing a modified Fung model for isotropic behaviour. The results suggest statistically significant effects of refrigerated storage on the spleen but negligible influence on the liver. Similarly to the impact of the freeze-thaw cycle, refrigerated storage caused a decrease in the mechanical properties of the spleen. This again supports the hypothesized cause of the altered behaviour of spleen due to the autolysis of elastin by elastolytic enzymes during and after the cooling period. Spleen and liver are good examples of tissue with and without elastin. These findings have wide biomechanical and decomposition implications for the study of soft tissues.},
 bibtype = {article},
 author = {Dương, M. Tuấn and Nguyễn, N. Huynh and Trần, T. Ngọc and Tolba, René Hany and Staat, Manfred},
 doi = {10.1080/23335432.2015.1049295},
 journal = {International Biomechanics},
 number = {1}
}

Preservation conditions may affect internal organs thus influencing the results of protracted biomechanical tests. The influence of the freeze-thaw cycle on the mechanical behaviour of porcine abdominal organs was reported in our previous work. Here we further investigate the effects of refrigerated storage on the mechanical properties of porcine spleen and liver. Twenty-seven swine were chosen for tensile testing. To simulate the conservation conditions before biomechanical experimentation, the total sample was divided into three groups of nine individuals each and tested in a fresh state, after a freeze-thaw cycle, and after refrigerated storage (+4 °C). Fitted stress-stretch curves for each tissue type were obtained by employing a modified Fung model for isotropic behaviour. The results suggest statistically significant effects of refrigerated storage on the spleen but negligible influence on the liver. Similarly to the impact of the freeze-thaw cycle, refrigerated storage caused a decrease in the mechanical properties of the spleen. This again supports the hypothesized cause of the altered behaviour of spleen due to the autolysis of elastin by elastolytic enzymes during and after the cooling period. Spleen and liver are good examples of tissue with and without elastin. These findings have wide biomechanical and decomposition implications for the study of soft tissues.

@inbook{
 type = {inbook},
 year = {2015},
 pages = {187-212},
 volume = {45},
 websites = {http://link.springer.com/chapter/10.1007/978-3-319-02535-3_11,http://link.springer.com/10.1007/978-3-319-02535-3_11},
 publisher = {Springer},
 city = {Cham, Heidelberg},
 institution = {Минск: Изд. центр БГУ},
 series = {Advanced Structured Materials},
 chapter = {Simulation of cardiac cell-seeded membranes using the edge-based smoothed FEM},
 id = {a57cbab3-91aa-350b-957c-ec180ab18bc1},
 created = {2018-04-01T19:17:46.043Z},
 accessed = {2014-10-20},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-02-28T16:00:05.563Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {frotscher2013simulation},
 source_type = {incollection},
 private_publication = {false},
 abstract = {We present an electromechanically coupled Finite Element model for cardiac tissue. It bases on the mechanical model for cardiac tissue of Hunter et al. that we couple to the McAllister-Noble-Tsien electrophysiological model of purkinje fibre cells. The corresponding system of ordinary differential equations is implemented on the level of the constitutive equations in a geometrically and physically nonlinear version of the so-called edge-based smoothed FEMfor plates. Mechanical material parameters are determined from our own pressure-deflection experimental setup. The main purpose of the model is to further examine the experimental results not only on mechanical but also on electrophysiological level down to ion channel gates. Moreover, we present first drug treatment simulations and validate the model with respect to the experiments.},
 bibtype = {inbook},
 author = {Frotscher, Ralf and Goßmann, Matthias and Raatschen, Hans-Jürgen and Temiz-Artmann, Ayşegül and Staat, Manfred},
 editor = {Altenbach, Holm and Mikhasev, Gennadi I.},
 doi = {10.1007/978-3-319-02535-3_11},
 title = {Shell and Membrane Theories in Mechanics and Biology: From Macro- to Nanoscale Structures}
}

We present an electromechanically coupled Finite Element model for cardiac tissue. It bases on the mechanical model for cardiac tissue of Hunter et al. that we couple to the McAllister-Noble-Tsien electrophysiological model of purkinje fibre cells. The corresponding system of ordinary differential equations is implemented on the level of the constitutive equations in a geometrically and physically nonlinear version of the so-called edge-based smoothed FEMfor plates. Mechanical material parameters are determined from our own pressure-deflection experimental setup. The main purpose of the model is to further examine the experimental results not only on mechanical but also on electrophysiological level down to ion channel gates. Moreover, we present first drug treatment simulations and validate the model with respect to the experiments.

@inproceedings{
 title = {Simulating beating cardiomyocytes with electromechanical coupling},
 type = {inproceedings},
 year = {2015},
 keywords = {cardiomyocytes,cell interaction,cell physiology},
 websites = {https://nbn-resolving.org/urn:nbn:de:101:1-2018111407534824068862,http://opus.bibliothek.fh-aachen.de/opus4/frontdoor/index/index/docId/7442},
 city = {Hannover},
 id = {0d632402-eab9-314f-b438-610a15dcd3a5},
 created = {2020-01-28T22:25:50.075Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-01-28T22:50:17.957Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2015},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Frotscher, Ralf and Duong, Minh Tuan and Staat, Manfred},
 editor = {Lenarz, Thomas and Wriggers, Peter},
 doi = {10.21269/7442},
 booktitle = {II. International Conference on Biomedical Technology : 28-30 October 2015 Hannover, Germany}
}

@article{
 title = {Physical response of hyperelastic models for composite materials and soft tissues},
 type = {article},
 year = {2015},
 keywords = {Constitutive model,Ill-conditioned,Numerical stability,Physical behaviour,Soft tissues},
 pages = {3},
 volume = {2},
 websites = {http://apjcen.springeropen.com/articles/10.1186/s40540-015-0015-x},
 month = {12},
 day = {8},
 id = {a6b54b16-6111-3815-9f00-9bc277b803a3},
 created = {2020-08-30T17:51:56.668Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-08-30T18:18:23.732Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Duong2015},
 private_publication = {false},
 abstract = {A hyperelastic model must not only characterize the mechanical response of a composite material such as soft tissue, but also ensure numerical stability by a feasible set of material parameters. Apart from the well-known ill-conditioning problem caused by the incompressibility constraint, the paper indicates another ill-conditioning occurring in any general fibre-reinforced material model for tubular organs when unbalance between the fibre strain energy and the matrix strain energy becomes too large. Specifically, although the Holzapfel model is polyconvex, this problem can be observed as an unphysical behaviour in a physiological deformation range of a tissue such as arterial wall and intestine by thickening in the thickness direction associated with a volume growth of a specimen in a tension test. Particularly, the same problem for a polyconvex modified Fung-type model with the matrix characterized by the neo-Hookean model has been discussed for the first time. By investigating the influence of the shear modulus in these two models, we not only prove the cause of the ill-conditioning but also propose a solution to control the unbalance in the strain energy. The numerical results show significant enhancement of the model stability in overcoming the unphysical deformation.},
 bibtype = {article},
 author = {Duong, Minh Tuan and Nguyen, Nhu Huynh and Staat, Manfred},
 doi = {10.1186/s40540-015-0015-x},
 journal = {Asia Pacific Journal on Computational Engineering},
 number = {1}
}

A hyperelastic model must not only characterize the mechanical response of a composite material such as soft tissue, but also ensure numerical stability by a feasible set of material parameters. Apart from the well-known ill-conditioning problem caused by the incompressibility constraint, the paper indicates another ill-conditioning occurring in any general fibre-reinforced material model for tubular organs when unbalance between the fibre strain energy and the matrix strain energy becomes too large. Specifically, although the Holzapfel model is polyconvex, this problem can be observed as an unphysical behaviour in a physiological deformation range of a tissue such as arterial wall and intestine by thickening in the thickness direction associated with a volume growth of a specimen in a tension test. Particularly, the same problem for a polyconvex modified Fung-type model with the matrix characterized by the neo-Hookean model has been discussed for the first time. By investigating the influence of the shear modulus in these two models, we not only prove the cause of the ill-conditioning but also propose a solution to control the unbalance in the strain energy. The numerical results show significant enhancement of the model stability in overcoming the unphysical deformation.

@inproceedings{
 title = {Uncertain multimode failure and limit analysis of shells},
 type = {inproceedings},
 year = {2014},
 keywords = {Limit Analysis,Multimode Failure,Non-linear Optimization,Reliability Analysis,Shakedown Analysis},
 pages = {1896-1907},
 websites = {opus.bibliothek.fh-aachen.de/opus4/files/6508/Barcelona_2014-p819.pdf},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {f9d2798f-b336-39c4-afce-76151e44c994},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2014uncertainlimit},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {This paper presents a numerical procedure for reliability analysis of thin plates and shells with respect to plastic collapse. The procedure involves a deterministic limit analysis for each probabilistic iteration, which is based on the upper bound approach and the use of the exact Ilyushin yield surface. Probabilistic limit analysis deals with uncertainties of the loads, material strength and thickness of the shell. Based on a direct definition of the limit state function, the calculation of the failure probability may be efficiently solved by using the First and Second Order Reliability Methods (FORM and SORM). The problem of reliability of structural systems (series systems) will be handled by the application of a special technique which permits to find all the design points corresponding to all the failure modes. Studies show, in this case, that it improves considerably the FORM and SORM results.},
 bibtype = {inproceedings},
 author = {Trần, Thanh Ngọc and Staat, Manfred},
 editor = {Oñate, E and J. Oliver, J and Huerta, A},
 booktitle = {11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) July 20-25, 2014, Barcelona, Spain}
}

This paper presents a numerical procedure for reliability analysis of thin plates and shells with respect to plastic collapse. The procedure involves a deterministic limit analysis for each probabilistic iteration, which is based on the upper bound approach and the use of the exact Ilyushin yield surface. Probabilistic limit analysis deals with uncertainties of the loads, material strength and thickness of the shell. Based on a direct definition of the limit state function, the calculation of the failure probability may be efficiently solved by using the First and Second Order Reliability Methods (FORM and SORM). The problem of reliability of structural systems (series systems) will be handled by the application of a special technique which permits to find all the design points corresponding to all the failure modes. Studies show, in this case, that it improves considerably the FORM and SORM results.

@inproceedings{
 title = {A multicriteria method for truss optimization},
 type = {inproceedings},
 year = {2014},
 keywords = {Limit and Shakedown Analysis,Sizing Optimization},
 pages = {1821-1832},
 websites = {http://opus.bibliothek.fh-aachen.de/opus4/files/6510/Barcelona_2014-p3625.pdf},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {03a91654-d972-39aa-ab4b-8a4e64de17fd},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2014multicriteria},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {We propose a multicriteria approach to the optimization of trusses. Stress and cross sectional areas of bars are considered as independent variables. This is a distinguishing point of this method. Using two independent variables makes the equilibrium equations become nonlinear. The problem is solved by the Optimization Toolbox of Matlab. In this paper, we consider the nine-bar truss of as an example.},
 bibtype = {inproceedings},
 author = {Trần, Ngọc Trinh and Staat, Manfred and Stavroulakis, Georgios E.},
 editor = {Oñate, E and J. Oliver, J and Huerta, A},
 booktitle = {11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) July 20-25, 2014, Barcelona, Spain}
}

We propose a multicriteria approach to the optimization of trusses. Stress and cross sectional areas of bars are considered as independent variables. This is a distinguishing point of this method. Using two independent variables makes the equilibrium equations become nonlinear. The problem is solved by the Optimization Toolbox of Matlab. In this paper, we consider the nine-bar truss of as an example.

@inproceedings{
 title = {Evaluation of a computational model for drug action on cardiac tissue},
 type = {inproceedings},
 year = {2014},
 keywords = {Cardiac Tissue,Cell Models,Drug Modeling,Finite Element Method},
 pages = {1425-1436},
 websites = {opus.bibliothek.fh-aachen.de/opus4/files/6505/Barcelona_2014-p633.pdf},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {e3991aea-0a4a-3d22-9496-4f89d238ea33},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {frotscher2014evaluation},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {In this paper an electromechanical finite element model of cardiac tissue is evaluated with respect to its ability to simulate drug action. We compare experimental mechanical data of our partners with corresponding simulation results.},
 bibtype = {inproceedings},
 author = {Frotscher, Ralf and Koch, Jan-Peter and Raatschen, Hans-Jürgen and Staat, Manfred},
 editor = {Oñate, E and J. Oliver, J and Huerta, A},
 booktitle = {11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) July 20-25, 2014, Barcelona, Spain}
}

In this paper an electromechanical finite element model of cardiac tissue is evaluated with respect to its ability to simulate drug action. We compare experimental mechanical data of our partners with corresponding simulation results.

@inproceedings{
 title = {A face-based smoothed finite element method for hyperelastic models and tissue growth},
 type = {inproceedings},
 year = {2014},
 keywords = {FEM,FS-FEM,Hyperelastic Models,Nonlinear Problems,SFEM},
 pages = {2657-2668},
 websites = {opus.bibliothek.fh-aachen.de/opus4/files/6509/Barcelona_2014-p3040.pdf},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {9cd137f3-e685-36be-bd12-20dfbfbeecab},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {duong2014facebased},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {This paper presents a Face-based Smoothed Finite Element Method (FS-FEM) using the 4-node tetrahedral elements (T4) (FS-FEM-T4) applied to nonlinear problems. The FS-FEM can overcome and improve some existing problems which the standard Finite Element Method using the T4 (FEM-T4) often faces, such as the well-known overly stiff behavior, poor stress solution, and volumetric effects. The principal idea of the FS-FEM is to formulate a strain field as a spatial average of the standard strain measure. In the field of biomechanics, the FS-FEM is still relative new. We have implemented the FS-FEM into the open source software Code_Aster for large scale biomedical applications. Numerical results of the FS-FEM for linear and nonlinear problems show clearly its advantages in improving accuracy particularly for the distorted meshes. A combination of the FS-FEM with the growth models performed exhibits clearly good performances.},
 bibtype = {inproceedings},
 author = {Dương, Minh Tuấn and Staat, Manfred},
 editor = {Oñate, E and J. Oliver, J and Huerta, A},
 booktitle = {11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) July 20-25, 2014, Barcelona, Spain}
}

This paper presents a Face-based Smoothed Finite Element Method (FS-FEM) using the 4-node tetrahedral elements (T4) (FS-FEM-T4) applied to nonlinear problems. The FS-FEM can overcome and improve some existing problems which the standard Finite Element Method using the T4 (FEM-T4) often faces, such as the well-known overly stiff behavior, poor stress solution, and volumetric effects. The principal idea of the FS-FEM is to formulate a strain field as a spatial average of the standard strain measure. In the field of biomechanics, the FS-FEM is still relative new. We have implemented the FS-FEM into the open source software Code_Aster for large scale biomedical applications. Numerical results of the FS-FEM for linear and nonlinear problems show clearly its advantages in improving accuracy particularly for the distorted meshes. A combination of the FS-FEM with the growth models performed exhibits clearly good performances.

@article{
 title = {FEM-based shakedown analysis of hardening structures},
 type = {article},
 year = {2014},
 keywords = {Kinematic hardening,Ratchetting,Two-surface plas},
 pages = {4},
 volume = {1},
 websites = {http://www.apjcen.com/content/1/1/4,https://apjcen.springeropen.com/articles/10.1186/2196-1166-1-4,https://nbn-resolving.org/urn:nbn:de:101:1-2019080321291662161022},
 month = {12},
 day = {29},
 id = {01d91703-483a-33e6-90d8-df04033c95a3},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-05-05T20:38:03.155Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {pham2014},
 source_type = {article},
 private_publication = {false},
 abstract = {This paper develops a new finite element method (FEM)-based upper bound algorithm for limit and shakedown analysis of hardening structures by a direct plasticity method. The hardening model is a simple two-surface model of plasticity with a fixed bounding surface. The initial yield surface can translate inside the bounding surface, and it is bounded by one of the two equivalent conditions: (1) it always stays inside the bounding surface or (2) its centre cannot move outside the back-stress surface. The algorithm gives an effective tool to analyze the problems with a very high number of degree of freedom. Our numerical results are very close to the analytical solutions and numerical solutions in literature.},
 bibtype = {article},
 author = {Phạm, Phú Tình and Staat, Manfred},
 doi = {10.1186/2196-1166-1-4},
 journal = {Asia Pacific Journal on Computational Engineering},
 number = {1}
}

This paper develops a new finite element method (FEM)-based upper bound algorithm for limit and shakedown analysis of hardening structures by a direct plasticity method. The hardening model is a simple two-surface model of plasticity with a fixed bounding surface. The initial yield surface can translate inside the bounding surface, and it is bounded by one of the two equivalent conditions: (1) it always stays inside the bounding surface or (2) its centre cannot move outside the back-stress surface. The algorithm gives an effective tool to analyze the problems with a very high number of degree of freedom. Our numerical results are very close to the analytical solutions and numerical solutions in literature.

@inbook{
 type = {inbook},
 year = {2014},
 pages = {101-117},
 volume = {3},
 websites = {http://link.springer.com/10.1007/978-94-007-6827-7_5},
 publisher = {Springer Netherlands},
 city = {Dordrecht},
 chapter = {Shakedown analysis of Reissner-Mindlin plates using the edge-based smoothed finite element method},
 id = {1721bb33-4ecc-31eb-a81f-ad93accf4a43},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-09-16},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2014shakedown},
 source_type = {incollection},
 private_publication = {false},
 abstract = {This paper concerns the development of a primal-dual algorithm for limit and shakedown analysis of Reissner-Mindlin plates made of von Mises material. At each optimization iteration, the lower bound of the shakedown load multiplier is calculated simultaneously with the upper bound using the duality theory. An edge-based smoothed finite element method (ES-FEM) combined with the discrete shear gap (DSG) technique is used to improve the accuracy of the solutions and to avoid the transverse shear locking behaviour. The method not only possesses all inherent features of convergence and accuracy from ES-FEM, but also ensures that the total number of variables in the optimization problem is kept to a minimum compared with the standard finite element formulation. Numerical examples are presented to demonstrate the effectiveness of the present method.},
 bibtype = {inbook},
 author = {Trần, Thanh Ngọc and Staat, Manfred},
 editor = {Spiliopoulos, Konstantinos and Weichert, Dieter},
 doi = {10.1007/978-94-007-6827-7_5},
 title = {Direct Methods for Limit States in Structures and Materials}
}

This paper concerns the development of a primal-dual algorithm for limit and shakedown analysis of Reissner-Mindlin plates made of von Mises material. At each optimization iteration, the lower bound of the shakedown load multiplier is calculated simultaneously with the upper bound using the duality theory. An edge-based smoothed finite element method (ES-FEM) combined with the discrete shear gap (DSG) technique is used to improve the accuracy of the solutions and to avoid the transverse shear locking behaviour. The method not only possesses all inherent features of convergence and accuracy from ES-FEM, but also ensures that the total number of variables in the optimization problem is kept to a minimum compared with the standard finite element formulation. Numerical examples are presented to demonstrate the effectiveness of the present method.

@inproceedings{
 title = {Optimization of the flight style in ski jumping},
 type = {inproceedings},
 year = {2014},
 keywords = {Aerodynamics,Computer simulation,Optimal control,Ski jumping,Sports engineering},
 pages = {799-810},
 websites = {opus.bibliothek.fh-aachen.de/opus4/files/6506/Barcelona_2014-p584.pdf},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {fe89dab5-4a65-3838-bc58-86efef7a6af2},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {jung2014optimization},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {During the flight phase the athlete has to optimize the aerodynamic forces in order to maximize the jump length while keeping the flight stable, both with respect to his features and abilities. A system of first order nonlinear differential equations describes the motion of a ski jumper and provides the basis for solving this constrained optimization problem by means of an optimization algorithm and comprehensive wind tunnel measurements. An optimization algorithm was developed on the basis of Pontryagin´s minimum principle combined with a penalty function derived from flight position constraints. By varying the constraints, it has been recently shown that there are various possibilities to reach comparable jump lengths and individual athletes have to develop their individual optimum which is to be tuned with their personal features and abilities. In this study, the effect of the take-off velocity perpendicular to the ramp (v_p0) on the flight style is examined in order to deepen the understanding of the individual flight style optimization. It is shown that a reference value of v_p0=2.5 ms^-1 can be used for optimization studies in elite ski jumping. Optimization studies can be used advantageously for guiding the individual training. Since the optimization algorithm was developed for the flight phase starting at t=0.7 s, future work should be based on the extension concerning the initial flight and the landing preparation. Furthermore, the take-off phase can be added since it can be also described by a first order nonlinear differential equation. For this purpose new comprehensive wind tunnel measurements with athletes using the latest equipment and field studies are necessary. The presented optimization approach can be applied to any sports which can be described by ordinary differential equations. That provides a new basis for improving the performance.},
 bibtype = {inproceedings},
 author = {Jung, Alexander and Staat, Manfred and Müller, Wolfram},
 editor = {Oñate, E and J. Oliver, J and Huerta, A},
 booktitle = {11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) July 20-25, 2014, Barcelona, Spain}
}

During the flight phase the athlete has to optimize the aerodynamic forces in order to maximize the jump length while keeping the flight stable, both with respect to his features and abilities. A system of first order nonlinear differential equations describes the motion of a ski jumper and provides the basis for solving this constrained optimization problem by means of an optimization algorithm and comprehensive wind tunnel measurements. An optimization algorithm was developed on the basis of Pontryagin´s minimum principle combined with a penalty function derived from flight position constraints. By varying the constraints, it has been recently shown that there are various possibilities to reach comparable jump lengths and individual athletes have to develop their individual optimum which is to be tuned with their personal features and abilities. In this study, the effect of the take-off velocity perpendicular to the ramp (v_p0) on the flight style is examined in order to deepen the understanding of the individual flight style optimization. It is shown that a reference value of v_p0=2.5 ms^-1 can be used for optimization studies in elite ski jumping. Optimization studies can be used advantageously for guiding the individual training. Since the optimization algorithm was developed for the flight phase starting at t=0.7 s, future work should be based on the extension concerning the initial flight and the landing preparation. Furthermore, the take-off phase can be added since it can be also described by a first order nonlinear differential equation. For this purpose new comprehensive wind tunnel measurements with athletes using the latest equipment and field studies are necessary. The presented optimization approach can be applied to any sports which can be described by ordinary differential equations. That provides a new basis for improving the performance.

@article{
 title = {Limit and shakedown analysis under uncertainty},
 type = {article},
 year = {2014},
 keywords = {FEM,Shakedown,direct plasticity,mathematical pr},
 pages = {1343008},
 volume = {11},
 websites = {http://www.worldscientific.com/doi/abs/10.1142/S0219876213430081},
 month = {6},
 publisher = {World Scientific Publishing Company},
 id = {f955c48b-f185-3d1f-b42c-6dd74a7252f6},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat2014limit},
 source_type = {article},
 private_publication = {false},
 abstract = {Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. Upper and lower bound theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behavior under time variant loading. The limit state function and its gradient are obtained from a mathematical optimization problem. The method is implemented into a general purpose finite element model (FEM) code. Combined with first-order methods/second-order methods (FORM/SORM) robust and precise analyses can be performed for structures with high reliability. This approach is particularly effective because the sensitivities which are needed by FORM/SORM are derived from the solution of the deterministic problem.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1142/S0219876213430081},
 journal = {International Journal of Computational Methods},
 number = {03}
}

Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. Upper and lower bound theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behavior under time variant loading. The limit state function and its gradient are obtained from a mathematical optimization problem. The method is implemented into a general purpose finite element model (FEM) code. Combined with first-order methods/second-order methods (FORM/SORM) robust and precise analyses can be performed for structures with high reliability. This approach is particularly effective because the sensitivities which are needed by FORM/SORM are derived from the solution of the deterministic problem.

@inproceedings{
 title = {A 3D finite element model of the female pelvic floor for the reconstruction of urinary incontinence},
 type = {inproceedings},
 year = {2014},
 keywords = {Active Closure,Integral Theory,Pelvic Floor Anatomy,Urethral Opening,Urinary Incontinence},
 pages = {923-934},
 websites = {opus.bibliothek.fh-aachen.de/opus4/files/6507/Barcelona_2014-p1073.pdf},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {a0f348ee-eb29-31cf-9f7f-f208fd6df610},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {bhattarai2014pelvicfloor},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Urinary incontinence is a well known pelvic floor (PF) dysfunction in the aging female. Causes can be mainly assumed to be vaginal delivery and reduced stiffness of supporting structures. These can be addressed effectively through a minimally invasive surgery with an insertion of a Polyvinyl anchoring mesh `to restore the structure to improve its function': the fundamental principle of the `Integral Theory System'. Although significant research has been done, an exact cause of incontinence remains elusive, either because of limited knowledge of pelvic floor anatomy or of a lack of anatomically realistic finite element simulations. In order to cope up with such shortcomings and to facilitate an effective treatment method, the detailed study of pelvic anatomy, realistic modeling of pelvic floor functions and 3D finite element simulations of the pelvic floor dynamics during urethral closure and opening are the core interests of this research work.},
 bibtype = {inproceedings},
 author = {Bhattarai, Aroj and Frotscher, Ralf and Sora, M-C and Staat, Manfred},
 editor = {Oñate, E and J. Oliver, J and Huerta, A},
 booktitle = {11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI) July 20-25, 2014, Barcelona, Spain}
}

Urinary incontinence is a well known pelvic floor (PF) dysfunction in the aging female. Causes can be mainly assumed to be vaginal delivery and reduced stiffness of supporting structures. These can be addressed effectively through a minimally invasive surgery with an insertion of a Polyvinyl anchoring mesh `to restore the structure to improve its function': the fundamental principle of the `Integral Theory System'. Although significant research has been done, an exact cause of incontinence remains elusive, either because of limited knowledge of pelvic floor anatomy or of a lack of anatomically realistic finite element simulations. In order to cope up with such shortcomings and to facilitate an effective treatment method, the detailed study of pelvic anatomy, realistic modeling of pelvic floor functions and 3D finite element simulations of the pelvic floor dynamics during urethral closure and opening are the core interests of this research work.

@article{
 title = {Flight style optimization in ski jumping on normal, large, and ski flying hills},
 type = {article},
 year = {2014},
 keywords = {Aerodynamics,Computer simulation,Optimal control,Ski jumping},
 pages = {716-22},
 volume = {47},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/24388531,http://linkinghub.elsevier.com/retrieve/pii/S0021929013005733},
 month = {2},
 publisher = {Elsevier},
 day = {7},
 id = {6902ec96-7d9e-3611-b130-44a73b53d44b},
 created = {2014-06-02T18:44:50.000Z},
 accessed = {2014-06-02},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-05-22T20:17:18.729Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Jung2014},
 private_publication = {false},
 abstract = {In V-style ski jumping, aerodynamic forces are predominant performance factors and athletes have to solve difficult optimization problems in parts of a second in order to obtain their jump length maximum and to keep the flight stable. Here, a comprehensive set of wind tunnel data was used for optimization studies based on Pontryagin's minimum principle with both the angle of attack α and the body-ski angle β as controls. Various combinations of the constraints αmax and βmin(t) were analyzed in order to compare different optimization strategies. For the computer simulation studies, the Olympic hill profiles in Esto-Sadok, Russia (HS 106m, HS 140m), and in Harrachov, Czech Republic, host of the Ski Flying World Championships 2014 (HS 205m) were used. It is of high importance for ski jumping practice that various aerodynamic strategies, i.e. combinations of α- and β-time courses, can lead to similar jump lengths which enables athletes to win competitions using individual aerodynamic strategies. Optimization results also show that aerodynamic behavior has to be different at different hill sizes (HS). Optimized time courses of α and β using reduced drag and lift areas in order to mimic recent equipment regulations differed only in a negligible way. This indicates that optimization results presented here are not very sensitive to minor changes of the aerodynamic equipment features when similar jump length are obtained by using adequately higher in-run velocities. However, wind tunnel measurements with athletes including take-off and transition to stabilized flight, flight, and landing behavior would enable a more detailed understanding of individual flight style optimization.},
 bibtype = {article},
 author = {Jung, Alexander and Staat, Manfred and Müller, Wolfram},
 doi = {10.1016/j.jbiomech.2013.11.021},
 journal = {Journal of biomechanics},
 number = {3}
}

In V-style ski jumping, aerodynamic forces are predominant performance factors and athletes have to solve difficult optimization problems in parts of a second in order to obtain their jump length maximum and to keep the flight stable. Here, a comprehensive set of wind tunnel data was used for optimization studies based on Pontryagin's minimum principle with both the angle of attack α and the body-ski angle β as controls. Various combinations of the constraints αmax and βmin(t) were analyzed in order to compare different optimization strategies. For the computer simulation studies, the Olympic hill profiles in Esto-Sadok, Russia (HS 106m, HS 140m), and in Harrachov, Czech Republic, host of the Ski Flying World Championships 2014 (HS 205m) were used. It is of high importance for ski jumping practice that various aerodynamic strategies, i.e. combinations of α- and β-time courses, can lead to similar jump lengths which enables athletes to win competitions using individual aerodynamic strategies. Optimization results also show that aerodynamic behavior has to be different at different hill sizes (HS). Optimized time courses of α and β using reduced drag and lift areas in order to mimic recent equipment regulations differed only in a negligible way. This indicates that optimization results presented here are not very sensitive to minor changes of the aerodynamic equipment features when similar jump length are obtained by using adequately higher in-run velocities. However, wind tunnel measurements with athletes including take-off and transition to stabilized flight, flight, and landing behavior would enable a more detailed understanding of individual flight style optimization.

@article{
 title = {Stresses produced by different textile mesh implants in a tissue equivalent},
 type = {article},
 year = {2014},
 pages = {25-30},
 volume = {15},
 websites = {http://www.degruyter.com/view/j/biomat.2014.15.issue-1-2/bnm-2014-0003/bnm-2014-0003.xml},
 month = {1},
 day = {1},
 id = {6f32dec3-6d48-3cf1-ac06-afb78499db72},
 created = {2014-07-05T06:22:30.000Z},
 accessed = {2014-10-23},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {mesh2015},
 source_type = {article},
 notes = {Special Issue Medical Textiles},
 private_publication = {false},
 abstract = {In pelvic floor surgery mesh implants are commonly used to recover incontinence and prolapse. There is a huge number of different mesh implants that have largely different mechanical properties, like their dimension, their material, the way of weaving, the number of threads used for the weaving, thickness of the threads, pore size and orientation of the pores. Due to the numerous differences the mesh implants already have been mechanically investigated with respect to all those properties and uniaxial tension tests, tearing tests, bending burst tests and other loading experiments have been conducted to determine maximum forces, strain, stress, pull-out strength, the degree of anisotropy, material parameters and hysteresis. In this paper we compare two different meshes, the Gynecare (GC) of Ethicon, USA and SIS direct (SD) of FEG Textiltechnik, Germany. We choose those meshes because they have a considerably different structure which we identifoed to be very important by means of their pull-out behavior and stress distribution in the surrounding tissue. We present an experimental method for measuring the pull-out strength and visualizing the shear stresses in a muscle tissue equivalent using photoelasticity. The meshes are embedded into a transparent gelatin block. Gelatin serves as a tissue that behaves similar to muscle tissue. The end of the mesh and another textile tissue embedded at the other end of the gelatin block have been clamped into a tension machine. Applying tension to the mesh and looking at the gelatine block through a filter leads to colorful isochromatic lines that represent lines of equal shear stresses.},
 bibtype = {article},
 author = {Frotscher, Ralf and Staat, Manfred},
 doi = {10.1515/bnm-2014-0003},
 journal = {BioNanoMaterials},
 number = {1-2}
}

In pelvic floor surgery mesh implants are commonly used to recover incontinence and prolapse. There is a huge number of different mesh implants that have largely different mechanical properties, like their dimension, their material, the way of weaving, the number of threads used for the weaving, thickness of the threads, pore size and orientation of the pores. Due to the numerous differences the mesh implants already have been mechanically investigated with respect to all those properties and uniaxial tension tests, tearing tests, bending burst tests and other loading experiments have been conducted to determine maximum forces, strain, stress, pull-out strength, the degree of anisotropy, material parameters and hysteresis. In this paper we compare two different meshes, the Gynecare (GC) of Ethicon, USA and SIS direct (SD) of FEG Textiltechnik, Germany. We choose those meshes because they have a considerably different structure which we identifoed to be very important by means of their pull-out behavior and stress distribution in the surrounding tissue. We present an experimental method for measuring the pull-out strength and visualizing the shear stresses in a muscle tissue equivalent using photoelasticity. The meshes are embedded into a transparent gelatin block. Gelatin serves as a tissue that behaves similar to muscle tissue. The end of the mesh and another textile tissue embedded at the other end of the gelatin block have been clamped into a tension machine. Applying tension to the mesh and looking at the gelatine block through a filter leads to colorful isochromatic lines that represent lines of equal shear stresses.

@inbook{
 type = {inbook},
 year = {2014},
 keywords = {bilateral sagittal split osteotomy,bone sawing,training simulator,virtual reality},
 pages = {1-10},
 volume = {8789},
 websites = {http://link.springer.com/10.1007/978-3-319-12057-7_1},
 publisher = {Springer International Publishing},
 city = {Cham, Heidelberg},
 series = {Lecture Notes in Computer Science},
 chapter = {Preliminary bone sawing model for a virtual reality-based training simulator of bilateral sagittal split osteotomy},
 id = {d06eee26-8c98-3be8-b871-a10ba241f191},
 created = {2014-10-20T08:28:26.000Z},
 accessed = {2014-10-14},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:55:29.561Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {knott2014},
 source_type = {incollection},
 private_publication = {false},
 abstract = {Successful bone sawing requires a high level of skill and experience, which could be gained by the use of Virtual Reality-based simulators. A key aspect of these medical simulators is realistic force feedback. The aim of this paper is to model the bone sawing process in order to develop a valid training simulator for the bilateral sagittal split osteotomy, the most often applied corrective surgery in case of a malposition of the mandible. Bone samples from a human cadaveric mandible were tested using a designed experimental system. Image processing and statistical analysis were used for the selection of four models for the bone sawing process. The results revealed a polynomial dependency between the material removal rate and the applied force. Differences between the three segments of the osteotomy line and between the cortical and cancellous bone were highlighted.},
 bibtype = {inbook},
 author = {Knott, Thomas C and Sofronia, Raluca E and Gerressen, Marcus and Law, Yuen and Davidescu, Arjana and Savii, George G and Gatzweiler, Karl-Heinz and Staat, Manfred and Kuhlen, Torsten W},
 editor = {Bello, Fernando and Cotin, Stéphane},
 doi = {10.1007/978-3-319-12057-7_1},
 title = {Biomedical Simulation, Lecture Notes in Computer Science}
}

Successful bone sawing requires a high level of skill and experience, which could be gained by the use of Virtual Reality-based simulators. A key aspect of these medical simulators is realistic force feedback. The aim of this paper is to model the bone sawing process in order to develop a valid training simulator for the bilateral sagittal split osteotomy, the most often applied corrective surgery in case of a malposition of the mandible. Bone samples from a human cadaveric mandible were tested using a designed experimental system. Image processing and statistical analysis were used for the selection of four models for the bone sawing process. The results revealed a polynomial dependency between the material removal rate and the applied force. Differences between the three segments of the osteotomy line and between the cortical and cancellous bone were highlighted.

@inbook{
 type = {inbook},
 year = {2013},
 pages = {89-102},
 volume = {2},
 websites = {http://link.springer.com/10.1007/978-94-007-5425-6,http://link.springer.com/10.1007/978-94-007-5425-6_5},
 publisher = {Springer Netherlands},
 city = {Dordrecht},
 chapter = {An edge-based smoothed finite element method for primal-dual shakedown analysis of structures under uncertainties},
 id = {f792b2f8-b88b-3709-bfa0-b9cc5f8c9df0},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-09-16},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-07-15T17:23:55.696Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2013edge},
 source_type = {incollection},
 private_publication = {false},
 abstract = {This paper deals with the application of a new algorithm of probabilistic limit and shakedown analysis for 2D structures, in which the loading and strength of the material are to be considered as random variables. The procedure involves a deterministic shakedown analysis for each probabilistic iteration, which is based on the primal-dual approach and the edge-based smoothed finite element method (ES-FEM). The limit state function separating the safe and failure regions is defined directly as the difference between the obtained shakedown load factor and the current load factor. A Sequential Quadratic Programming (SQP) is implemented for finding the design point. Sensitivity analyses are performed numerically from a mathematical model and the probability of failure is calculated by the First Order Reliability Method. Because of use of constant smoothing functions in the ES-FEM, only one Gaussian point is required for each smoothing domain ensuring that the total number of variables in the resulting optimization problem is kept to a minimum compared with standard finite element formulation. Numerical examples are presented to show the validity and effectiveness of the present method.},
 bibtype = {inbook},
 author = {Trân, Thanh Ngọc and Staat, Manfred},
 editor = {de Saxcé, Géry and Oueslati, Abdelbacet and Charkaluk, Eric and Tritsch, Jean-Bernard},
 doi = {10.1007/978-94-007-5425-6_5},
 title = {Limit State of Materials and Structures}
}

This paper deals with the application of a new algorithm of probabilistic limit and shakedown analysis for 2D structures, in which the loading and strength of the material are to be considered as random variables. The procedure involves a deterministic shakedown analysis for each probabilistic iteration, which is based on the primal-dual approach and the edge-based smoothed finite element method (ES-FEM). The limit state function separating the safe and failure regions is defined directly as the difference between the obtained shakedown load factor and the current load factor. A Sequential Quadratic Programming (SQP) is implemented for finding the design point. Sensitivity analyses are performed numerically from a mathematical model and the probability of failure is calculated by the First Order Reliability Method. Because of use of constant smoothing functions in the ES-FEM, only one Gaussian point is required for each smoothing domain ensuring that the total number of variables in the resulting optimization problem is kept to a minimum compared with standard finite element formulation. Numerical examples are presented to show the validity and effectiveness of the present method.

@article{
 title = {Gonarthrosetherapie auf Kernspinresonanzbasis mit MBST-Vierjahresbeobachtungen},
 type = {article},
 year = {2013},
 pages = {13},
 volume = {2013},
 publisher = {Biermann Verlag GmbH},
 id = {35b527f8-1dca-3ea4-bf59-7feb27111db1},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {levers2013therapie},
 source_type = {article},
 private_publication = {false},
 bibtype = {article},
 author = {Levers, A and Staat, Manfred and van Laack, Walter},
 journal = {Orthopädische Nachrichten},
 number = {7/8}
}

@inbook{
 type = {inbook},
 year = {2013},
 pages = {71-87},
 volume = {2},
 websites = {http://link.springer.com/10.1007/978-94-007-5425-6,http://link.springer.com/10.1007/978-94-007-5425-6_4},
 publisher = {Springer Netherlands},
 city = {Dordrecht},
 chapter = {An upper bound algorithm for limit and shakedown analysis of bounded linearly kinematic hardening structures},
 id = {e29e7e5f-0147-3568-a0a2-fa73bcd0ad44},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-09-16},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {phạm2013upper},
 source_type = {incollection},
 private_publication = {false},
 abstract = {The paper develops a new FEM based algorithm for shakedown analysis of structures made of elastic plastic bounded linearly kinematic hardening material. The hardening effect is simulated by using a two-surface plastic model to bound the Melan-Prager model. The initial yield surface can translate inside the bounding surface, without changing its shape and size. The translated yield surface may touch the bounding surface and ratcheting may occur with clear benefit of hardening. Or it may not touch the bounding surface, alternating plasticity may occur and there is no effect of hardening. The direct calculation of plastic limit and shakedown bounds is considered as a nonlinear programming problem. The upper bound of the shakedown load is obtained as the minimum of the plastic dissipation function, which is based on the von Mises yield criterion.},
 bibtype = {inbook},
 author = {Phạm, Phu Tinh and Staat, Manfred},
 editor = {de Saxcé, Géry and Oueslati, Abdelbacet and Charkaluk, Eric and Tritsch, Jean-Bernard},
 doi = {10.1007/978-94-007-5425-6_4},
 title = {Limit State of Materials and Structures}
}

The paper develops a new FEM based algorithm for shakedown analysis of structures made of elastic plastic bounded linearly kinematic hardening material. The hardening effect is simulated by using a two-surface plastic model to bound the Melan-Prager model. The initial yield surface can translate inside the bounding surface, without changing its shape and size. The translated yield surface may touch the bounding surface and ratcheting may occur with clear benefit of hardening. Or it may not touch the bounding surface, alternating plasticity may occur and there is no effect of hardening. The direct calculation of plastic limit and shakedown bounds is considered as a nonlinear programming problem. The upper bound of the shakedown load is obtained as the minimum of the plastic dissipation function, which is based on the von Mises yield criterion.

@article{
 title = {Limit analysis of flaws in pressurized pipes and cylindrical vessels. Part II: Circumferential defects},
 type = {article},
 year = {2013},
 keywords = {Circumferential crack,Global collapse,Limit load,Plasticity,Pressure loaded crack-face},
 pages = {314-333},
 volume = {97},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0013794412002573},
 month = {1},
 publisher = {Pergamon},
 id = {d7fba2a3-1beb-30b6-89f2-f2710e76f099},
 created = {2014-06-02T18:44:51.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.027Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat2012limit},
 source_type = {article},
 private_publication = {false},
 abstract = {Upper and lower bound theorems of limit analyses have been presented in part I of the paper. Part II starts with the finite element discretization of these theorems and demonstrates how both can be combined in a primal–dual optimization problem. This recently proposed numerical method is used to guide the development of a new class of closed-form limit loads for circumferential defects, which show that only large defects contribute to plastic collapse with a rapid loss of strength with increasing crack sizes. The formulae are compared with primal–dual FEM limit analyses and with burst tests. Even closer predictions are obtained with iterative limit load solutions for the von Mises yield function and for the Tresca yield function. Pressure loading of the faces of interior cracks in thick pipes reduces the collapse load of circumferential defects more than for axial flaws. Axial defects have been treated in part I of the paper. ► This paper presents plastic limit loads for cracked thick-walled pipes for von Mises yield function and for Tresca yield function. ► Limit loads are given for the whole parameter range: from shallow to penetrating cracks, from short to fully-circumferential defects. ► Limit loads are derived for exterior cracks and for interior surface flaws with and without pressure on crack faces. ► All limit loads are compared with direct primal–dual FEM limit analyses and with burst tests.},
 bibtype = {article},
 author = {Staat, Manfred and Vu, Duc Khôi},
 doi = {10.1016/j.engfracmech.2012.05.017},
 journal = {Engineering Fracture Mechanics},
 number = {1}
}

Upper and lower bound theorems of limit analyses have been presented in part I of the paper. Part II starts with the finite element discretization of these theorems and demonstrates how both can be combined in a primal–dual optimization problem. This recently proposed numerical method is used to guide the development of a new class of closed-form limit loads for circumferential defects, which show that only large defects contribute to plastic collapse with a rapid loss of strength with increasing crack sizes. The formulae are compared with primal–dual FEM limit analyses and with burst tests. Even closer predictions are obtained with iterative limit load solutions for the von Mises yield function and for the Tresca yield function. Pressure loading of the faces of interior cracks in thick pipes reduces the collapse load of circumferential defects more than for axial flaws. Axial defects have been treated in part I of the paper. ► This paper presents plastic limit loads for cracked thick-walled pipes for von Mises yield function and for Tresca yield function. ► Limit loads are given for the whole parameter range: from shallow to penetrating cracks, from short to fully-circumferential defects. ► Limit loads are derived for exterior cracks and for interior surface flaws with and without pressure on crack faces. ► All limit loads are compared with direct primal–dual FEM limit analyses and with burst tests.

@article{
 title = {Einschränkung von Taluskippung und -vorschub durch verschiedene Sprunggelenkorthesen nach fibularer Bandruptur [Constraint of talar tilt and anterior drawer by differerent ankle braces after the rupture of fibular ligament]},
 type = {article},
 year = {2013},
 keywords = {Soccer,damping,efficiency,impact test,protection,soccer shin guards},
 pages = {306-309},
 volume = {2},
 websites = {http://opus4.bibliothek.fh-aachen.de/opus4/files/5227/van_Laack,Beleg.pdf,http://opus.bibliothek.fh-aachen.de/opus4/frontdoor/index/index/docId/5227},
 id = {c02bb645-b7ff-395a-8f19-c510ad400396},
 created = {2018-04-01T19:17:46.131Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-08-12T14:10:39.344Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {linden2013untersuchung},
 source_type = {article},
 private_publication = {false},
 abstract = {Die fibulare Bandruptur zählt zu einer der am häufigsten auftretenden Verletzungen des Bewegungsapparats. In den meisten Fällen wird heute die konservativ frühfunktionelle Therapie mit Sprunggelenkorthesen allgemein bevorzugt. Im Rahmen der vorliegenden Studie wurden 14 verschiedene Sprunggelenkorthesen im Hinblick auf ihre Einschränkung von Taluskippung und Talusvorschub untersucht. Zur Simulation einer fibularen Bandruptur wurde ein Unterschenkelmodell aus Holz mit Fußteil, mit angelegten Orthesen in einen Scheuba-Halteapparat eingespannt und mit 150 N seitlich sowie anterior-posterior belastet. Anhand der erstellten „gehaltenen“ Röntgenaufnahmen konnten Taluskippung und Talusvorschub jeder einzelnen Orthese eindeutig bestimmt werden. Die meisten Orthesen erreichten zufriedenstellende Ergebnisse. Es stellte sich heraus, dass vor allem eine eng anliegende, im Gelenkbereich anatomisch angepasste Form vorteilhaft zu sein scheint. [The ankle sprain is actually one of the most common injuries. Nowadays the conservative pre-functional therapy with ankle braces is generally preferred. In the present study 14 different ankle braces were tested with regard to their ability to constrict the talar tilt and anterior drawer displacement. As part of the tests a wooden model of a foot was used in order to simulate an ankle sprain. This model was clamped in a Scheuba-device with different ankle braces and a force of 150 N was applied to it. The stress radiographs showed different talar tilts and anterior drawers of each brace. Most ankle braces achieved a satisfying result. It has become obvious that a tight fitting and an anatomically designed shape seem to be favourable..]},
 bibtype = {article},
 author = {Linden, A and Fischöder, M and Staat, Manfred and Laack, Walter van},
 doi = {10.3238/oup.2013.0306-0309},
 journal = {OUP Zeitschrift für die orthopädische und unfallchirurgische Praxis},
 number = {6}
}

Die fibulare Bandruptur zählt zu einer der am häufigsten auftretenden Verletzungen des Bewegungsapparats. In den meisten Fällen wird heute die konservativ frühfunktionelle Therapie mit Sprunggelenkorthesen allgemein bevorzugt. Im Rahmen der vorliegenden Studie wurden 14 verschiedene Sprunggelenkorthesen im Hinblick auf ihre Einschränkung von Taluskippung und Talusvorschub untersucht. Zur Simulation einer fibularen Bandruptur wurde ein Unterschenkelmodell aus Holz mit Fußteil, mit angelegten Orthesen in einen Scheuba-Halteapparat eingespannt und mit 150 N seitlich sowie anterior-posterior belastet. Anhand der erstellten „gehaltenen“ Röntgenaufnahmen konnten Taluskippung und Talusvorschub jeder einzelnen Orthese eindeutig bestimmt werden. Die meisten Orthesen erreichten zufriedenstellende Ergebnisse. Es stellte sich heraus, dass vor allem eine eng anliegende, im Gelenkbereich anatomisch angepasste Form vorteilhaft zu sein scheint. [The ankle sprain is actually one of the most common injuries. Nowadays the conservative pre-functional therapy with ankle braces is generally preferred. In the present study 14 different ankle braces were tested with regard to their ability to constrict the talar tilt and anterior drawer displacement. As part of the tests a wooden model of a foot was used in order to simulate an ankle sprain. This model was clamped in a Scheuba-device with different ankle braces and a force of 150 N was applied to it. The stress radiographs showed different talar tilts and anterior drawers of each brace. Most ankle braces achieved a satisfying result. It has become obvious that a tight fitting and an anatomically designed shape seem to be favourable..]

@inbook{
 type = {inbook},
 year = {2013},
 pages = {165-167},
 websites = {http://elib.bsu.by/handle/123456789/56608},
 publisher = {Center of BSU},
 city = {Minsk, Belarus},
 id = {770238d2-c6c4-3f09-9617-43f3ad21ce94},
 created = {2018-12-27T11:31:22.550Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-10-31T08:45:06.461Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Frotscher2013},
 private_publication = {false},
 bibtype = {inbook},
 author = {Frotscher, Ralf and Gossmann, Matthias and Temiz-Artmann, Ayşegül and Staat, Manfred},
 editor = {Mikhasev, G.I. and Altenbach, Holm},
 chapter = {Simulation of cardiac cell-seeded membranes using the edge-based smoothed FEM},
 title = {Proceeding of the International Conference "Shell and Membrane Theories in Mechanics and Biology: From Macro- to Nanoscale Structures" (SMT in MB 2013)}
}

@article{
 title = {Introducing a method of in vitro testing of different anchoring systems used for female incontinence and prolapse surgery.},
 type = {article},
 year = {2013},
 pages = {401417},
 volume = {2013},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/24455692,http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC3881509},
 id = {dd1ed89a-085f-3ba3-bb94-e08cd0fde2ed},
 created = {2022-01-30T05:14:04.136Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2022-01-30T05:19:01.388Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Anding2013},
 private_publication = {false},
 abstract = {AIMS To develop a method for in vitro testing to compare different intracorporeal anchoring systems (AS) used, for example, in single-incision slings or vaginal meshes. Intracorporeal fixation needs reliable anchorage systems, which keep the implant in the operative and early postoperative phase in place. Up to now, the impact of the design of current anchor systems and their capability to provide sufficient retention forces is not known. METHODS Four AS ("PelFix", "Surelift", "TFS", and "MiniArc") were evaluated in an animal model and a ballistic gelatine model with pull-out tests. We performed ANOVA with post hoc Bonferroni. Results were presented as mean values whereby a significance level of <0.05 was considered significant. RESULTS The four systems showed significantly different pull-out forces. Depending on mesh structure, size, and form of the AS, mechanical strain resulted in deformation with local peak stresses. Under the condition of form stability, relative differences of pull-out forces did not change in different tissues. CONCLUSIONS Reliable testing of different AS in their ability to keep mesh implants in place can be done in animal models and in especially designed ballistic gelatine. These methods of testing will help to modify AS in novel pelvic floor implants.},
 bibtype = {article},
 author = {Anding, Ralf and Tabaza, Ruth and Staat, Manfred and Trenz, Eva and Lohmann, Philipp and Klinge, Uwe and Kirschner-Hermanns, Ruth},
 doi = {10.1155/2013/401417},
 journal = {BioMed research international}
}

AIMS To develop a method for in vitro testing to compare different intracorporeal anchoring systems (AS) used, for example, in single-incision slings or vaginal meshes. Intracorporeal fixation needs reliable anchorage systems, which keep the implant in the operative and early postoperative phase in place. Up to now, the impact of the design of current anchor systems and their capability to provide sufficient retention forces is not known. METHODS Four AS ("PelFix", "Surelift", "TFS", and "MiniArc") were evaluated in an animal model and a ballistic gelatine model with pull-out tests. We performed ANOVA with post hoc Bonferroni. Results were presented as mean values whereby a significance level of <0.05 was considered significant. RESULTS The four systems showed significantly different pull-out forces. Depending on mesh structure, size, and form of the AS, mechanical strain resulted in deformation with local peak stresses. Under the condition of form stability, relative differences of pull-out forces did not change in different tissues. CONCLUSIONS Reliable testing of different AS in their ability to keep mesh implants in place can be done in animal models and in especially designed ballistic gelatine. These methods of testing will help to modify AS in novel pelvic floor implants.

@article{
 title = {New measurements to compare soft tissue anchoring systems in pelvic floor surgery},
 type = {article},
 year = {2012},
 keywords = {PVDF,anchor,mesh,photoelasticity,pull-out strength,soft-tissue surrogate},
 pages = {924-933},
 volume = {100B},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/22287385,http://doi.wiley.com/10.1002/jbm.b.32654},
 month = {5},
 id = {7519734e-1a37-3c7b-a5ef-a5b5a0fc6a54},
 created = {2014-06-02T18:47:18.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.142Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2012},
 private_publication = {false},
 abstract = {Suburethral slings as well as different meshes are widely used treating stress urinary incontinence and prolaps in women. With the development of MiniSlings and special meshes using less alloplastic material anchorage systems become more important to keep devices in place and to put some tension especially on the MiniSlings. To date, there are many different systems of MiniSlings of different companies on the market which differ in the structure of the used meshes and anchors. A new objective measurement method to compare different properties of MiniSling systems (mesh and anchor) is presented in this article. Ballistic gelatine acts as soft tissue surrogate. Significant differences in parameters like pull-out strength of anchors or shrinkage of meshes under loading conditions have been determined. The form and size of the anchors as well as the structural stability of the meshes are decisive for a proper integration. The tested anchorings sytems showed markedly different mechanical function at their respective load bearing capacity. As the stable fixation of the device in tissue is a prerequisite for a permanet reinforcement, the proposed test system permits further optimisation of anchor and mesh devices to improve the success of the surgical treatment.},
 bibtype = {article},
 author = {Staat, Manfred and Trenz, Eva and Lohmann, Philipp and Frotscher, Ralf and Klinge, Uwe and Tabaza, Ruth and Kirschner-Hermanns, Ruth},
 doi = {10.1002/jbm.b.32654},
 journal = {Journal of Biomedical Materials Research Part B: Applied Biomaterials},
 number = {4}
}

Suburethral slings as well as different meshes are widely used treating stress urinary incontinence and prolaps in women. With the development of MiniSlings and special meshes using less alloplastic material anchorage systems become more important to keep devices in place and to put some tension especially on the MiniSlings. To date, there are many different systems of MiniSlings of different companies on the market which differ in the structure of the used meshes and anchors. A new objective measurement method to compare different properties of MiniSling systems (mesh and anchor) is presented in this article. Ballistic gelatine acts as soft tissue surrogate. Significant differences in parameters like pull-out strength of anchors or shrinkage of meshes under loading conditions have been determined. The form and size of the anchors as well as the structural stability of the meshes are decisive for a proper integration. The tested anchorings sytems showed markedly different mechanical function at their respective load bearing capacity. As the stable fixation of the device in tissue is a prerequisite for a permanet reinforcement, the proposed test system permits further optimisation of anchor and mesh devices to improve the success of the surgical treatment.

@inproceedings{
 title = {Characterizing the material properties of intestinal tissues},
 type = {inproceedings},
 year = {2012},
 keywords = {plates,smoothed finite element method SFEM,strain smoothing},
 publisher = {Verlag der TU Graz},
 id = {da38759c-872f-3e4d-bcd4-342878d96e33},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2012graz},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {The knowledge of biomechanical properties of intestinal tissue is critical for the development of realistic computer-based surgical simulators as well as for the optimal design of surgical staplers. Surgical staplers are used widely to re-establish continuity of the gastrointestinal tract. In order to predict the performance of stapled anastomosis by simulations, material parameters of the intestinal tissue must be determined for the dominant loading in compression by the staples.},
 bibtype = {inproceedings},
 author = {Tran, T N and Nováček, Vit and Turquier, Frédéric and Klinge, Uwe and Tolba, René Hany and Bronson, D and Miesse, A and Whiffen, Jennifer and Staat, Manfred},
 editor = {Holzapfel, Gehard A and Ogden, Ray W},
 booktitle = {ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012}
}

The knowledge of biomechanical properties of intestinal tissue is critical for the development of realistic computer-based surgical simulators as well as for the optimal design of surgical staplers. Surgical staplers are used widely to re-establish continuity of the gastrointestinal tract. In order to predict the performance of stapled anastomosis by simulations, material parameters of the intestinal tissue must be determined for the dominant loading in compression by the staples.

@inproceedings{
 title = {Effectiveness of the edge-based smoothed finite element method applied to soft biological tissues},
 type = {inproceedings},
 year = {2012},
 keywords = {plates,smoothed finite element method SFEM,strain smoothing},
 publisher = {Verlag der TU Graz},
 id = {8e9faa6c-5f71-3e6b-a73b-12f6543638d2},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {frotscher2012graz},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Finite Element Analyses of organs and muscles in the female pelvic floor as well as cardiac tissue are highly non-linear due to the material behaviour, the large deformations and displacements, and the contacts with other organs or implants. We reduce the resulting high computational costs using the Smoothed Finite Element Method (S-FEM) developed by G.R. Liu and T. Nguyen-Thoi. The very good convergence of these methods is achieved by smoothing the strain field.},
 bibtype = {inproceedings},
 author = {Frotscher, Ralf and Raatschen, Hans-Jürgen and Staat, Manfred},
 editor = {Holzapfel, Gerhard A and Ogden, Ray W},
 booktitle = {ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012}
}

Finite Element Analyses of organs and muscles in the female pelvic floor as well as cardiac tissue are highly non-linear due to the material behaviour, the large deformations and displacements, and the contacts with other organs or implants. We reduce the resulting high computational costs using the Smoothed Finite Element Method (S-FEM) developed by G.R. Liu and T. Nguyen-Thoi. The very good convergence of these methods is achieved by smoothing the strain field.

@inproceedings{
 title = {A primal-dual shakedown analysis of 3D structures using the face-based smoothed finite element method},
 type = {inproceedings},
 year = {2012},
 keywords = {limit analysis,moothed finite element method SFEM,nonlinear programming,shakedown analysis},
 pages = {4787-4793},
 websites = {https://www.scopus.com/record/display.uri?eid=2-s2.0-84871631378&origin=inward&txGid=ee071f6931a02101e5496793c8d29401},
 month = {9},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {8186f0ab-d456-3992-9a2f-1a81892116d6},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-30T16:48:36.557Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2012sfem},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {.},
 bibtype = {inproceedings},
 author = {Tran, Thanh Ngoc and Staat, Manfred},
 editor = {Eberhardsteiner, Josef and Böhm, Helmut J. and Rammerstorfer, Franz G.},
 booktitle = {Proceedings European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) Vienna, Austria, September 10-14, 2012}
}

.

@article{
 title = {Experimentelle Kraftmessungen als Beitrag zur Wirksamkeitsbeurteilung von Schienbeinschonern im Fußballsport [Experimental measurement of forces as a contribution to evaluate the effectiveness of shin guards in soccer]},
 type = {article},
 year = {2012},
 keywords = {Soccer,damping,efficiency,impact test,protection,soccer shin guards},
 pages = {10-15},
 volume = {1},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2012/355/pdf/Staat_OUP_01_2012_S00012_00017.pdf},
 id = {c1a35dee-f779-36be-8ace-c6d5f7227774},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {gorissen2012experimentelle},
 source_type = {article},
 private_publication = {false},
 abstract = {Diese Studie beschäftigte sich mit der Dämpfungswirkung von Schienbeinschonern, wie sie beim Fußball zum Einsatz kommen. Sie wurde mit Hilfe eines Pendelhammers durchgeführt, der verschiedene Aufschlagkräfte auf die Schoner ermöglichte. Dabei wurde deutlich, dass Schienbeinschoner die beste Wirkung bei Maximalkräften unterhalb von 5kN erreichen können, dass bei größerer Belastung allerdings Verbesserungsbedarf besteht. Hierfür konnte, u.a. durch den Einsatz neuer Materialien, ein guter Ansatzpunkt im „adäquaten Zusammenspiel von Schale und Polsterung“ der Schoner gefunden werden. Die Untersuchung hat weiterhin gezeigt, dass zumindest teilweise eine deutliche Verbesserung der Dämpfungswirkung der Schienbeinschoner in den letzten Jahren erreicht werden konnte. [This study was conducted to test the damping effects of commercially available soccer shin guards on their damping effects. Therefore a pendulum impact apparatus with varying impact forces was used. It became clear that shin guards show the best effect at maximum forces of less than 5kN. There is however a need for improvement at greater impact forces. A good starting point was found in an „appropriate interaction of shell and padding” of the shin guard. It was further clarified that a significant improvement on the damping effect could be achieved at least partially over the last years.]},
 bibtype = {article},
 author = {Gorißen, P and Staat, Manfred and Laack, Walter van},
 doi = {10.3238/oup.2012.0010-0015},
 journal = {OUP Zeitschrift für die orthopädische und unfallchirurgische Praxis},
 number = {1}
}

Diese Studie beschäftigte sich mit der Dämpfungswirkung von Schienbeinschonern, wie sie beim Fußball zum Einsatz kommen. Sie wurde mit Hilfe eines Pendelhammers durchgeführt, der verschiedene Aufschlagkräfte auf die Schoner ermöglichte. Dabei wurde deutlich, dass Schienbeinschoner die beste Wirkung bei Maximalkräften unterhalb von 5kN erreichen können, dass bei größerer Belastung allerdings Verbesserungsbedarf besteht. Hierfür konnte, u.a. durch den Einsatz neuer Materialien, ein guter Ansatzpunkt im „adäquaten Zusammenspiel von Schale und Polsterung“ der Schoner gefunden werden. Die Untersuchung hat weiterhin gezeigt, dass zumindest teilweise eine deutliche Verbesserung der Dämpfungswirkung der Schienbeinschoner in den letzten Jahren erreicht werden konnte. [This study was conducted to test the damping effects of commercially available soccer shin guards on their damping effects. Therefore a pendulum impact apparatus with varying impact forces was used. It became clear that shin guards show the best effect at maximum forces of less than 5kN. There is however a need for improvement at greater impact forces. A good starting point was found in an „appropriate interaction of shell and padding” of the shin guard. It was further clarified that a significant improvement on the damping effect could be achieved at least partially over the last years.]

@inproceedings{
 title = {Application of an edge-based smoothed finite element method on geometrically non-linear plates of non-linear material},
 type = {inproceedings},
 year = {2012},
 keywords = {plates,smoothed finite element method SFEM,strain smoothing},
 pages = {2928-2936},
 month = {9},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {365848d6-45cd-3fc6-a8d2-28e917ce1cd3},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-30T16:48:36.638Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {frotscher2012raatschen},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {In this paper we describe our implementation of the edge-based smoothed finite element method (ES-FEM) for physically and geometrically nonlinear problems in the finite element software Code Aster. The implementation works for linear triangular elements. We apply our implementation to linear and geometrically and materially nonlinear problems. We compare the simulation results obtained by this method with those obtained with standard FEM using linear triangular and quadrilateral elements. The results show that the accuracy of the solutions achieved with ES-FEM using linear triangular elements are comparable with those of standard FEM using quadrilateral elements. ES-FEM is especially very useful regarding large deformation problems because it has the ability to work with largely distorted meshes and naturally avoids shear locking. These facts lead to a high computational efficiency and low computational costs.},
 bibtype = {inproceedings},
 author = {Frotscher, Ralf and Raatschen, Hans-Jürgen and Staat, Manfred},
 editor = {Eberhardsteiner, Josef and Böhm, Helmut J. and Rammerstorfer, Franz G.},
 booktitle = {Proceedings European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) Vienna, Austria, September 10-14, 2012}
}

In this paper we describe our implementation of the edge-based smoothed finite element method (ES-FEM) for physically and geometrically nonlinear problems in the finite element software Code Aster. The implementation works for linear triangular elements. We apply our implementation to linear and geometrically and materially nonlinear problems. We compare the simulation results obtained by this method with those obtained with standard FEM using linear triangular and quadrilateral elements. The results show that the accuracy of the solutions achieved with ES-FEM using linear triangular elements are comparable with those of standard FEM using quadrilateral elements. ES-FEM is especially very useful regarding large deformation problems because it has the ability to work with largely distorted meshes and naturally avoids shear locking. These facts lead to a high computational efficiency and low computational costs.

@article{
 title = {Determination of the frictional coefficient of the implant-antler interface: experimental approach},
 type = {article},
 year = {2012},
 keywords = {Antler bone,Dental implant,Frictional coefficient,Frictional force,Immediate loading,Sliding velocity},
 pages = {359-363},
 volume = {57},
 websites = {http://www.degruyter.com/view/j/bmte.2012.57.issue-5/bmt-2012-0010/bmt-2012-0010.xml},
 month = {1},
 publisher = {de Gruyter},
 day = {1},
 id = {0c77009c-9cb4-34b7-b60d-80fef85600ba},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {hasan2012determination},
 source_type = {article},
 private_publication = {false},
 abstract = {The similar bone structure of reindeer antler to human bone permits studying the osseointegration of dental implants in the jawbone. As the friction is one of the major factors that have a significant influence on the initial stability of immediately loaded dental implants, it is essential to define the frictional coefficient of the implant-antler interface. In this study, the kinetic frictional forces at the implant-antler interface were measured experimentally using an optomechanical setup and a stepping motor controller under different axial loads and sliding velocities. The corresponding mean values of the static and kinetic frictional coefficients were within the range of 0.5–0.7 and 0.3–0.5, respectively. An increase in the frictional forces with increasing applied axial loads was registered. The measurements showed an evidence of a decrease in the magnitude of the frictional coefficient with increasing sliding velocity. The results of this study provide a considerable assessment to clarify the suitable frictional coefficient to be used in the finite element contact analysis of antler specimens.},
 bibtype = {article},
 author = {Hasan, Istabrak and Keilig, Ludger and Staat, Manfred and Wahl, Gerhard and Bourauel, Christoph},
 doi = {10.1515/bmt-2012-0010},
 journal = {Biomedizinische Technik/Biomedical Engineering},
 number = {5}
}

The similar bone structure of reindeer antler to human bone permits studying the osseointegration of dental implants in the jawbone. As the friction is one of the major factors that have a significant influence on the initial stability of immediately loaded dental implants, it is essential to define the frictional coefficient of the implant-antler interface. In this study, the kinetic frictional forces at the implant-antler interface were measured experimentally using an optomechanical setup and a stepping motor controller under different axial loads and sliding velocities. The corresponding mean values of the static and kinetic frictional coefficients were within the range of 0.5–0.7 and 0.3–0.5, respectively. An increase in the frictional forces with increasing applied axial loads was registered. The measurements showed an evidence of a decrease in the magnitude of the frictional coefficient with increasing sliding velocity. The results of this study provide a considerable assessment to clarify the suitable frictional coefficient to be used in the finite element contact analysis of antler specimens.

@inproceedings{
 title = {Implementation of the edge-based smoothed extended finite element method},
 type = {inproceedings},
 year = {2012},
 keywords = {exte,smoothed extended finite element method SXFEM},
 pages = {8117-8123},
 websites = {https://www.scopus.com/record/display.uri?eid=2-s2.0-84871626747&origin=inward&txGid=3242fda8b10367fbcb86133a8618d38f},
 month = {9},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {29101ee6-4932-393f-b1a6-3f28df361d5f},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:25:34.989Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {nix2012sxfem},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Cutting is an essential manipulation task in surgery. For these and other discontinuities T. Belytschko et al. introduced the Extended Finite Element Method (XFEM), that allows the simulation of cuts, cracks or interfaces in virtual environments. To reduce the high computational costs in FE simulations and to improve the accuracy, G.R. Liu et al. developed the Smoothed Finite Element Method (SFEM). Combining these two methods results in the Smoothed Extended Finite Element Method (SXFEM) which was first introduced by St.P.A. Bordas et al.. They used the cell-based strain smoothing with triangular and quadrangular elements to show the ability for FE simulations. In this paper we describe our implementation of the edge-based SXFEM in the large FE software Code Aster of Electricit´e de France SA. These elements can be implemented easily because they only require the modification of the discretized gradient operator B. The implementation works for linear problems, e.g. problems with material interfaces, discretized with linear triangular elements. We compare the simulation results obtained by this method with those obtained with the standard XFEM using triangular elements. The principle of strain smoothing extended to the partition of unity enrichment simplifies the numerical integration of discontinuous approximations in the XFEM.},
 bibtype = {inproceedings},
 author = {Nix, Yvonne and Frotscher, Ralf and Staat, Manfred},
 editor = {Eberhardsteiner, Josef and Böhm, Helmut J. and Rammerstorfer, Franz G.},
 booktitle = {Proceedings European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) Vienna, Austria, September 10-14, 2012}
}

Cutting is an essential manipulation task in surgery. For these and other discontinuities T. Belytschko et al. introduced the Extended Finite Element Method (XFEM), that allows the simulation of cuts, cracks or interfaces in virtual environments. To reduce the high computational costs in FE simulations and to improve the accuracy, G.R. Liu et al. developed the Smoothed Finite Element Method (SFEM). Combining these two methods results in the Smoothed Extended Finite Element Method (SXFEM) which was first introduced by St.P.A. Bordas et al.. They used the cell-based strain smoothing with triangular and quadrangular elements to show the ability for FE simulations. In this paper we describe our implementation of the edge-based SXFEM in the large FE software Code Aster of Electricit´e de France SA. These elements can be implemented easily because they only require the modification of the discretized gradient operator B. The implementation works for linear problems, e.g. problems with material interfaces, discretized with linear triangular elements. We compare the simulation results obtained by this method with those obtained with the standard XFEM using triangular elements. The principle of strain smoothing extended to the partition of unity enrichment simplifies the numerical integration of discontinuous approximations in the XFEM.

@inproceedings{
 title = {Finite element implementation of a 3D Fung-type model},
 type = {inproceedings},
 year = {2012},
 keywords = {plates,smoothed finite element method SFEM,strain smoothing},
 pages = {1-2},
 publisher = {Verlag der TU Graz},
 id = {87081e39-7721-38ca-9482-da4027505607},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {doung2012graz},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {A modified Fung-type model (MFM) for three-dimensional (3D) boundary-value problems has been implemente into a finite element program, in which the Fung model represents fibers and the neo-Hookean model describes matrix of soft tissue. Simple constraints on the material parameters are adopted to render the MFM applicable to not only any material behavior, such as orthotropic, transversely isotropic and isotropic material, but also in the analysis stapled anastomoses for which the material is subjected to both tension load and compression},
 bibtype = {inproceedings},
 author = {Duong, M T and Nguyen, N H and Staat, Manfred},
 editor = {Holzapfel, Gerhard A and Ogden, Ray W},
 booktitle = {ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012}
}

A modified Fung-type model (MFM) for three-dimensional (3D) boundary-value problems has been implemente into a finite element program, in which the Fung model represents fibers and the neo-Hookean model describes matrix of soft tissue. Simple constraints on the material parameters are adopted to render the MFM applicable to not only any material behavior, such as orthotropic, transversely isotropic and isotropic material, but also in the analysis stapled anastomoses for which the material is subjected to both tension load and compression

@inproceedings{
 title = {FEM based shakedown analysis of hardening structures},
 type = {inproceedings},
 year = {2012},
 keywords = {FEM,kinematic hardening,ratchetting,shakedown,two-surface plasticity},
 pages = {870-882},
 month = {8},
 publisher = {Tri Thức, Hanoi},
 city = {Ho Chi Minh City},
 id = {86a708d3-9951-35eb-a477-655890e1ae85},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-01-11T13:47:59.422Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {pham2012acome},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {This paper develops a new FEM based upper bound algorithm for limit and shakedown analysis of hardening structures by a direct plastic method. The hardening model is a simple two-surface model of plasticity with a fixed bounding surface. The initial yield surface can translate inside the bounding surface, and it is bounded by one of the two equivalent conditions: (1) it always stays inside the bounding surface, or (2) its centre cannot move outside the back-stress surface. The algorithm gives an effective tool to analyze the problems with a very high number of degrees of freedom. Our numerical results are very close to the analytical solutions and numerical solutions in literature.},
 bibtype = {inproceedings},
 author = {Phạm, Phú Tình and Nguyễn, Thị Ngọc Loan and Staat, Manfred},
 editor = {Nguyen, Tong Thien and Ngyen, Xuan Hung and Nguyen, Thoi Trung and Chau, Dinh Thanh},
 booktitle = {Proceedings International Conference on Advances in Computational Mechanics (ACOME), August 14-16, 2012, Ho Chi Minh City, Vietnam}
}

This paper develops a new FEM based upper bound algorithm for limit and shakedown analysis of hardening structures by a direct plastic method. The hardening model is a simple two-surface model of plasticity with a fixed bounding surface. The initial yield surface can translate inside the bounding surface, and it is bounded by one of the two equivalent conditions: (1) it always stays inside the bounding surface, or (2) its centre cannot move outside the back-stress surface. The algorithm gives an effective tool to analyze the problems with a very high number of degrees of freedom. Our numerical results are very close to the analytical solutions and numerical solutions in literature.

@inproceedings{
 title = {Numerical stability enhancement of modeling hyperelastic materials},
 type = {inproceedings},
 year = {2012},
 keywords = {Holzapfel model,hyperelastic model,numerical instability,strongly directional behavior},
 pages = {4794-4808},
 websites = {https://www.scopus.com/record/display.uri?eid=2-s2.0-84871639018&origin=inward&txGid=3242fda8b10367fbcb86133a8618d38f},
 month = {9},
 institution = {European Community on Computational Methods in Applied Sciences (ECCOMAS)},
 id = {2d9333aa-f15a-3091-a62c-9399e53eb6ea},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-01-01T11:19:17.216Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {duong2012stability},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Besides the capability of representing the material behavior of biological soft tissue accurately, constitutive equations must also ensure numerical stability in simulations. Biomechanical models of composite materials, such as arteries, ureter, intestine, etc., which combine an isotropic term and an anisotropic term, may generally show Strongly Directional Behavior (SDB). This can lead to unphysical response in numerical simulation known as “fibre rotation”. However, based on mathematical reasoning and numerical analysis, a plausible argument proves that this unrealistic behavior is due to a large difference between the isotropic strain energy and the anisotropic strain energy, resulting in an ill-conditioned constitutive matrix. Furthermore, this paper shows that the SDB dominating over the isotropic behavior can, in general, cause unphysical responses along non-fibrous directions, which was proven for a Transversely Isotropic Model (TIM). Different from the solution developed in literature, this paper proposes a model implemented in a finite element program which can solve or alleviate the instability problem at large strains regardless of determining the histological structure of tissue. The proposed material model comprising a new strain energy component can mitigate some restrictions of mechanical response of the model in the literature. Though it was mathematically formulated for dealing with the numerical problem, however, good performance is still achieved. Pure shear, biaxial tests, and additional tension tests were carried out to validate the proposed formulation and analyze comprehensively the numerical problems. The numerical results show reasonable stability and convergence of the proposed model and its significant effect on the mechanical behavior at larger strains as well as its capability of modeling soft tissue.},
 bibtype = {inproceedings},
 author = {Duong, M T and Nguyen, N H and Staat, Manfred},
 editor = {Eberhardsteiner, Josef and Böhm, Helmut J. and Rammerstorfer, Franz G.},
 booktitle = {Proceedings European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) Vienna, Austria, September 10-14, 2012}
}

Besides the capability of representing the material behavior of biological soft tissue accurately, constitutive equations must also ensure numerical stability in simulations. Biomechanical models of composite materials, such as arteries, ureter, intestine, etc., which combine an isotropic term and an anisotropic term, may generally show Strongly Directional Behavior (SDB). This can lead to unphysical response in numerical simulation known as “fibre rotation”. However, based on mathematical reasoning and numerical analysis, a plausible argument proves that this unrealistic behavior is due to a large difference between the isotropic strain energy and the anisotropic strain energy, resulting in an ill-conditioned constitutive matrix. Furthermore, this paper shows that the SDB dominating over the isotropic behavior can, in general, cause unphysical responses along non-fibrous directions, which was proven for a Transversely Isotropic Model (TIM). Different from the solution developed in literature, this paper proposes a model implemented in a finite element program which can solve or alleviate the instability problem at large strains regardless of determining the histological structure of tissue. The proposed material model comprising a new strain energy component can mitigate some restrictions of mechanical response of the model in the literature. Though it was mathematically formulated for dealing with the numerical problem, however, good performance is still achieved. Pure shear, biaxial tests, and additional tension tests were carried out to validate the proposed formulation and analyze comprehensively the numerical problems. The numerical results show reasonable stability and convergence of the proposed model and its significant effect on the mechanical behavior at larger strains as well as its capability of modeling soft tissue.

@article{
 title = {Finite element modelling of stapled colorectal end-to-end anastomosis: Advantages of variable height stapler design},
 type = {article},
 year = {2012},
 keywords = {Anastomotic leakage,End-to-end colorectal anastomosis,Finite element modelling,Surgical staplers,Variable height stapler design},
 pages = {2693-2697},
 volume = {45},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/22871347,http://linkinghub.elsevier.com/retrieve/pii/S0021929012004186},
 month = {10},
 publisher = {Elsevier},
 day = {11},
 id = {2772c5a8-d3dd-333e-b477-69e27a53f90d},
 created = {2014-06-02T18:44:49.000Z},
 accessed = {2014-06-02},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.213Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {novavcek2012finite},
 source_type = {article},
 private_publication = {false},
 abstract = {The impact of surgical staplers on tissues has been studied mostly in an empirical manner. In this paper, finite element method was used to clarify the mechanics of tissue stapling and associated phenomena. Various stapling modalities and several designs of circular staplers were investigated to evaluate the impact of the device on tissues and mechanical performance of the end-to-end colorectal anastomosis. Numerical simulations demonstrated that a single row of staples is not adequate to resist leakage due to non-linear buckling and opening of the tissue layers between two adjacent staples. Compared to the single staple row configuration, significant increase in stress experienced by the tissue at the inner staple rows was observed in two and three rows designs. On the other hand, adding second and/or third staple row had no effect on strain in the tissue inside the staples. Variable height design with higher staples in outer rows significantly reduced the stresses and strains in outer rows when compared to the same configuration with flat cartridge. © 2012 Elsevier Ltd.},
 bibtype = {article},
 author = {Nováček, Vit and Trần, T.N. and Klinge, Uwe and Tolba, René Hany and Staat, Manfred and Bronson, D.G. and Miesse, A.M. and Whiffen, Jennifer and Turquier, Frédéric},
 doi = {10.1016/j.jbiomech.2012.07.021},
 journal = {Journal of Biomechanics},
 number = {15}
}

The impact of surgical staplers on tissues has been studied mostly in an empirical manner. In this paper, finite element method was used to clarify the mechanics of tissue stapling and associated phenomena. Various stapling modalities and several designs of circular staplers were investigated to evaluate the impact of the device on tissues and mechanical performance of the end-to-end colorectal anastomosis. Numerical simulations demonstrated that a single row of staples is not adequate to resist leakage due to non-linear buckling and opening of the tissue layers between two adjacent staples. Compared to the single staple row configuration, significant increase in stress experienced by the tissue at the inner staple rows was observed in two and three rows designs. On the other hand, adding second and/or third staple row had no effect on strain in the tissue inside the staples. Variable height design with higher staples in outer rows significantly reduced the stresses and strains in outer rows when compared to the same configuration with flat cartridge. © 2012 Elsevier Ltd.

@article{
 title = {Influence of a freeze–thaw cycle on the stress–stretch curves of tissues of porcine abdominal organs},
 type = {article},
 year = {2012},
 keywords = {Autolysis,Decomposition,Freeze-thaw process,Liver,Spleen},
 pages = {2382-2386},
 volume = {45},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/22867765,http://linkinghub.elsevier.com/retrieve/pii/S0021929012003983},
 month = {9},
 publisher = {Elsevier},
 day = {21},
 id = {d8dbe76b-f404-3c77-9530-8ecc055ef75f},
 created = {2014-06-02T18:44:49.000Z},
 accessed = {2014-05-26},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.091Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {nguyen2012influence},
 source_type = {article},
 private_publication = {false},
 abstract = {The paper investigates both fresh porcine spleen and liver and the possible decomposition of these organs under a freeze-thaw cycle. The effect of tissue preservation condition is an important factor which should be taken into account for protracted biomechanical tests. In this work, tension tests were conducted for a large number of tissue specimens from twenty pigs divided into two groups of 10. Concretely, the first group was tested in fresh state; the other one was tested after a freeze-thaw cycle which simulates the conservation conditions before biomechanical experiments. A modified Fung model for isotropic behavior was adopted for the curve fitting of each kind of tissues. Experimental results show strong effects of the realistic freeze-thaw cycle on the capsule of elastin-rich spleen but negligible effects on the liver which virtually contains no elastin. This different behavior could be explained by the autolysis of elastin by elastolytic enzymes during the warmer period after thawing. Realistic biomechanical properties of elastin-rich organs can only be expected if really fresh tissue is tested. The observations are supported by tests of intestines. © 2012 Elsevier Ltd.},
 bibtype = {article},
 author = {Nguyễn, N. Huynh and Dương, M. Tuấn and Trần, T. Ngọc and Phạm, P. Tình and Grottke, Oliver and Tolba, R. and Staat, Manfred},
 doi = {10.1016/j.jbiomech.2012.07.008},
 journal = {Journal of Biomechanics},
 number = {14}
}

The paper investigates both fresh porcine spleen and liver and the possible decomposition of these organs under a freeze-thaw cycle. The effect of tissue preservation condition is an important factor which should be taken into account for protracted biomechanical tests. In this work, tension tests were conducted for a large number of tissue specimens from twenty pigs divided into two groups of 10. Concretely, the first group was tested in fresh state; the other one was tested after a freeze-thaw cycle which simulates the conservation conditions before biomechanical experiments. A modified Fung model for isotropic behavior was adopted for the curve fitting of each kind of tissues. Experimental results show strong effects of the realistic freeze-thaw cycle on the capsule of elastin-rich spleen but negligible effects on the liver which virtually contains no elastin. This different behavior could be explained by the autolysis of elastin by elastolytic enzymes during the warmer period after thawing. Realistic biomechanical properties of elastin-rich organs can only be expected if really fresh tissue is tested. The observations are supported by tests of intestines. © 2012 Elsevier Ltd.

@article{
 title = {Limit and shakedown analysis under uncertainty},
 type = {article},
 year = {2012},
 keywords = {Direct plasticity,FEM,FORM,Mathematical programming,SORM,Shakedown,Structural Reliability},
 pages = {45-57},
 volume = {19},
 websites = {http://old.tdt.edu.vn/images/stories/tapchikhoahocungdung/tckhud19/5.pdf},
 month = {8},
 id = {3b201fd8-3151-3057-9521-563d9cc7c9ce},
 created = {2018-04-01T19:17:45.828Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-04-01T20:37:18.601Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat2012acome},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. Upper and lower bound theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behavior under time variant loading. The limit state function and its gradient are obtained from a mathematical optimization problem. The method is implemented into a general purpose FEM code. Combined with FORM/SORM robust and precise analyses can be performed for structures with high reliability. This approach is particularly effective because the sensitivities which are needed by FORM/SORM are derived from the solution of the deterministic problem.},
 bibtype = {article},
 author = {Staat, Manfred},
 journal = {Tạp chí Khoa học & ứng dụng - Đại học Tôn Đức Thắng [Journal of Applied Sciences - Ton Duc Thang University]}
}

Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. Upper and lower bound theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behavior under time variant loading. The limit state function and its gradient are obtained from a mathematical optimization problem. The method is implemented into a general purpose FEM code. Combined with FORM/SORM robust and precise analyses can be performed for structures with high reliability. This approach is particularly effective because the sensitivities which are needed by FORM/SORM are derived from the solution of the deterministic problem.

@inproceedings{
 title = {Limit and shakedown analysis under uncertainty},
 type = {inproceedings},
 year = {2012},
 keywords = {Direct plasticity,FEM,FORM/SORM,Mathematical programming,Shakedown,Structural reliability},
 pages = {837-861},
 publisher = {Tri Thức, Hanoi},
 city = {Ho Chi Minh City, Vietnam},
 id = {7fdac10a-827a-3d02-aa3f-0bf03d526689},
 created = {2019-01-11T14:28:39.322Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-01-11T15:31:46.164Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2012},
 private_publication = {false},
 abstract = {Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. The paper discusses some difficulties of different reliability methods for FEM­ discretized nonlinear structures. It is proposed that theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behaviour under time variant loading. The limit state function and its gradient is obtained from a mathematical optimization problem. For application to large FEM models a basis reduction method is used. The method is implemented into a general purpose FEM code. Combined with FORM highly effective, robust and precise analyses could be performed for high-reliabilty problems.},
 bibtype = {inproceedings},
 author = {Staat, Manfred},
 editor = {Nguyen, Tong Thien and Ngyen, Xuan Hung and Nguyen, Thoi Trung and Chau, Dinh Thanh},
 booktitle = {Proceedings International Conference on Advances in Computational Mechanics (ACOME), August 14-16, 2012, Ho Chi Minh City, Vietnam}
}

Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. The paper discusses some difficulties of different reliability methods for FEM­ discretized nonlinear structures. It is proposed that theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behaviour under time variant loading. The limit state function and its gradient is obtained from a mathematical optimization problem. For application to large FEM models a basis reduction method is used. The method is implemented into a general purpose FEM code. Combined with FORM highly effective, robust and precise analyses could be performed for high-reliabilty problems.

@article{
 title = {Hypothermic machine perfusion of kidney grafts: Which pressure is preferred?},
 type = {article},
 year = {2011},
 keywords = {Perfusion pressure,Pig,Preservation,Transplantation},
 pages = {1051-1059},
 volume = {39},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/21161683,http://link.springer.com/10.1007/s10439-010-0228-7},
 month = {3},
 id = {edc3ea3b-125e-32ed-8362-8f9ac0f3c69f},
 created = {2014-06-02T18:47:19.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Doorschodt2011},
 private_publication = {false},
 abstract = {To assess the effect of the perfusion pressure (PP) during machine perfusion (MP) on the preservation quality of kidney grafts, we compared mean PPs of 25 and 30 mmHg using a porcine autotransplantation model. After assessment of the microcirculation, animals underwent left nephrectomy. Thereafter, kidneys were washed out followed by 20 h of MP at 25 mmHg (MP25, n = 7) or 30 mmHg (MP30, n = 7) using a novel MP system for hypothermic pulsatile perfusion. After MP preservation, the contralateral kidneys were removed and the preserved kidneys heterotopically autotransplanted. Ten minutes after reperfusion, the microcirculation was reassessed. Seven days posttransplant, animals were euthanized and the kidney grafts removed for histological analysis. MP using a mean PP of 25 mmHg resulted in higher capillary blood flow after reperfusion. In the MP30 group, 6 out of 7 animals survived, whereas in the MP25 group all animals survived. Overall, improvement in recovery of renal function and a better preservation of structural integrity were seen in the MP25 group compared to the MP30 group. Using a novel system for hypothermic MP, a mean PP of 25 mmHg is preferred over a mean PP of 30 mmHg.},
 bibtype = {article},
 author = {Doorschodt, B. M. and Schreinemachers, M. C J M and Behbahani, Mehdi and Florquin, S. and Weis, J. and Staat, Manfred and Tolba, René Hany},
 doi = {10.1007/s10439-010-0228-7},
 journal = {Annals of Biomedical Engineering},
 number = {3}
}

To assess the effect of the perfusion pressure (PP) during machine perfusion (MP) on the preservation quality of kidney grafts, we compared mean PPs of 25 and 30 mmHg using a porcine autotransplantation model. After assessment of the microcirculation, animals underwent left nephrectomy. Thereafter, kidneys were washed out followed by 20 h of MP at 25 mmHg (MP25, n = 7) or 30 mmHg (MP30, n = 7) using a novel MP system for hypothermic pulsatile perfusion. After MP preservation, the contralateral kidneys were removed and the preserved kidneys heterotopically autotransplanted. Ten minutes after reperfusion, the microcirculation was reassessed. Seven days posttransplant, animals were euthanized and the kidney grafts removed for histological analysis. MP using a mean PP of 25 mmHg resulted in higher capillary blood flow after reperfusion. In the MP30 group, 6 out of 7 animals survived, whereas in the MP25 group all animals survived. Overall, improvement in recovery of renal function and a better preservation of structural integrity were seen in the MP25 group compared to the MP30 group. Using a novel system for hypothermic MP, a mean PP of 25 mmHg is preferred over a mean PP of 30 mmHg.

@inproceedings{
 title = {Modified stapler configuration for optimisation of colonic anastomosis},
 type = {inproceedings},
 year = {2011},
 keywords = {anastomoses,finite element ana,surgical staplers},
 pages = {21-25},
 publisher = {MEDIMOND, Pianoro, Italy},
 id = {3d9c8ca0-2d9e-30a0-a942-7f4497d8a6f6},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-01-01T11:19:17.217Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {klinge2011essr},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {.},
 bibtype = {inproceedings},
 author = {Klinge, Uwe and Trần, T N and Nováček, Vit and Staat, Manfred and Alizai, Patrick and Miesse, A M and Tolba, Rene},
 editor = {Tolba, René Hany},
 booktitle = {Proccedings of ESSR 2011, 46th Annual Congress of the European Society of Surgical Research, Aachen, Germany, May 25-28, 2011}
}

.

@inproceedings{
 title = {Experimental and computational approach to study colorectal anastomosis},
 type = {inproceedings},
 year = {2011},
 keywords = {anastomoses,finite element ana,surgical staplers},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2011/348/},
 id = {7867321f-6f01-3292-b0b4-2c84945593b8},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2011isb},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {This paper presents a methodology to study and understand the mechanics of stapled anastomotic behaviors by combining empirical experimentation and finite element analysis. Performance of stapled anastomosis is studied in terms of leakage and numerical results which are compared to in vitro experiments performed on fresh porcine tissue. Results suggest that leaks occur between the tissue and staple legs penetrating through the tissue.},
 bibtype = {inproceedings},
 author = {Trần, T N and Nováček, Vit and Tolba, R and Klinge, Uwe and Turquier, Frédéric and Staat, Manfred},
 booktitle = {ISB 2011, Proceedings of the XXIII Congress of the International Society of Biomechanics, Brussels, Belgium, July 3-7, 2011}
}

This paper presents a methodology to study and understand the mechanics of stapled anastomotic behaviors by combining empirical experimentation and finite element analysis. Performance of stapled anastomosis is studied in terms of leakage and numerical results which are compared to in vitro experiments performed on fresh porcine tissue. Results suggest that leaks occur between the tissue and staple legs penetrating through the tissue.

@article{
 title = {Analyse der Langzeitwirkung der MBST® KernspinResonanzTherapie bei Gonarthrose},
 type = {article},
 year = {2011},
 keywords = {Arthrosetherapie [ gonarthrosis,Gonarthrose,MBST,arthrosis therapy ]},
 pages = {536-543},
 volume = {47},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2011/350/},
 id = {80b1b23d-0040-3e1a-aef2-cb62de29621e},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {levers2011analyse},
 source_type = {article},
 private_publication = {false},
 abstract = {Auf der Basis von Patientenabfragen mittels Fragebogen zum Schmerzempfinden und zur Einschränkung bei Aktivitäten des alltäglichen Lebens wird die Langzeitwirkung der MBST® KernspinResonanzTherapie bei Gonarthrose untersucht. An der Studie nahmen 39 Patienten teil, bei denen die Therapie bis zu vier Jahre zurückliegt. Neben einer Gesamtbetrachtung wird der Erfolg auch in Abhängigkeit von Alter, Geschlecht und sportlicher Aktivität analysiert. Insgesamt weist die Studie auf eine anhaltende Verbesserung des Gesundheitszustands mit zum Teil deutlicher Schmerzlinderung auch noch nach vier Jahren hin, jedoch mit einer leichten Schmerzzunahme gegen Ende des Untersuchungszeitraums von vier Jahren. Eine tendenziell positivere Wirkung bei Frauen, älteren Menschen oder auch sportlich nicht-aktiven Patienten lässt auf eine mögliche Beeinflussung des Erfolgs der Therapie durch (Über-)Belastungen im Alltag schließen. Ein zusätzlich positiver Effekt der Therapie auf die Knochendichte ist ebenfalls denkbar, dies bleibt jedoch offen. Based upon a questionnaire for patient-queries regarding pain-sensation and activityrestrictions during everyday tasks, the long-term effect of MBST® nuclear magnetic resonance therapy is studied in osteoarthritis of the knee. 39 patients, whose therapy dates back up to four years, participated in the study. In addition to an overall view, the success of this therapy is also analyzed regarding age, gender and physical activities. Overall, the study pointed out a sustained improvement in the patients’ local health-status with a significant pain-relief even after four years, but also with a slight increase in pain towards the end of that four-year period. There tends to be a more positive effect on women, on elderly or also on even non-sports-active patients which suggests a possible influence by daily (over)-stressing on the success of the therapy. An additional positive effect of the therapy on bone density is also conceivable, however, this remains open.},
 bibtype = {article},
 author = {Levers, Andrea and Staat, Manfred and van Laack, Walter},
 journal = {Orthopädische Praxis},
 number = {11}
}

Auf der Basis von Patientenabfragen mittels Fragebogen zum Schmerzempfinden und zur Einschränkung bei Aktivitäten des alltäglichen Lebens wird die Langzeitwirkung der MBST® KernspinResonanzTherapie bei Gonarthrose untersucht. An der Studie nahmen 39 Patienten teil, bei denen die Therapie bis zu vier Jahre zurückliegt. Neben einer Gesamtbetrachtung wird der Erfolg auch in Abhängigkeit von Alter, Geschlecht und sportlicher Aktivität analysiert. Insgesamt weist die Studie auf eine anhaltende Verbesserung des Gesundheitszustands mit zum Teil deutlicher Schmerzlinderung auch noch nach vier Jahren hin, jedoch mit einer leichten Schmerzzunahme gegen Ende des Untersuchungszeitraums von vier Jahren. Eine tendenziell positivere Wirkung bei Frauen, älteren Menschen oder auch sportlich nicht-aktiven Patienten lässt auf eine mögliche Beeinflussung des Erfolgs der Therapie durch (Über-)Belastungen im Alltag schließen. Ein zusätzlich positiver Effekt der Therapie auf die Knochendichte ist ebenfalls denkbar, dies bleibt jedoch offen. Based upon a questionnaire for patient-queries regarding pain-sensation and activityrestrictions during everyday tasks, the long-term effect of MBST® nuclear magnetic resonance therapy is studied in osteoarthritis of the knee. 39 patients, whose therapy dates back up to four years, participated in the study. In addition to an overall view, the success of this therapy is also analyzed regarding age, gender and physical activities. Overall, the study pointed out a sustained improvement in the patients’ local health-status with a significant pain-relief even after four years, but also with a slight increase in pain towards the end of that four-year period. There tends to be a more positive effect on women, on elderly or also on even non-sports-active patients which suggests a possible influence by daily (over)-stressing on the success of the therapy. An additional positive effect of the therapy on bone density is also conceivable, however, this remains open.

@article{
 title = {Influence of stapler configuration on mechanics of connecting tissues},
 type = {article},
 year = {2011},
 keywords = {anastomoses,finite element ana,surgical staplers},
 pages = {261},
 volume = {25},
 websites = {http://www.sages2011.org/influence-of-stapler-configuration-on-mechanics-of-connecting-tissues/,http://link.springer.com/10.1007/s00464-011-1598-0},
 month = {3},
 id = {ca2ea9a9-5e91-38ce-97ca-0093aab44c86},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-30T16:48:36.674Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tolba2011sages},
 source_type = {inproceedings},
 notes = {Surg Endosc 25 (2011) S261},
 private_publication = {false},
 abstract = {Surgical staplers are used to perform several intestinal procedures including reconstructions and anastomoses with highly standardised techniques. However, postoperative bleeding, anastomotic dehiscence, or stenosis cannot be completely prevented. Considering the significant variations of tissue we analysed whether an optimised design of staples and staple lines can be defined, in particular looking for the impact of staple size, closure mechanism and the number of staple lines on the local compression of the surrounding tissue.},
 bibtype = {article},
 author = {Tolba, Rene and Ngọc, Trần T and Klinge, Uwe and Segan, R and Nováček, Vit and Turquier, Frédéric and Staat, Manfred},
 doi = {10.1007/s00464-011-1598-0},
 journal = {Surgical Endoscopy},
 number = {S1}
}

Surgical staplers are used to perform several intestinal procedures including reconstructions and anastomoses with highly standardised techniques. However, postoperative bleeding, anastomotic dehiscence, or stenosis cannot be completely prevented. Considering the significant variations of tissue we analysed whether an optimised design of staples and staple lines can be defined, in particular looking for the impact of staple size, closure mechanism and the number of staple lines on the local compression of the surrounding tissue.

@inproceedings{
 title = {Finite element modeling of gastrointestinal tissue stapling},
 type = {inproceedings},
 year = {2011},
 websites = {http://profiles.wizfolio.com/Termis2011/publications/19010/135984/},
 id = {6e0c0de1-dc51-3eea-a97f-94d0712c79c2},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {novavcek2011finite},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Background Following surgical intervention, establishing GI tract continuity remains challenging due to limited knowledge regarding device effects on tissue. Significant effort has been directed toward creating reliable tissue apposition via mechanical devices, i.e., staplers. These instruments have a lengthy history of clinical use even though their impact on tissue response and healing remain unclear. This study investigates tissue response to several stapling modalities which may influence tissue regeneration and healing. Methods We developed finite element models (FEM) utilizing circular staplers often employed in GI tissue to investigate the influence of the number of staple rows (one, two, three) wire size, closed height and tissue thickness on stress within the tissues. Results For equivalent closed staple height and initial tissue thickness, each additional outer row increased the compressive stress within the tissues in the inner row(s). Smaller staple wire resulted in lower tissue stress compared to larger wire. Conclusion FEM demonstrated differences between stapling modalities tested; staple row number and wire gauge were significant factors contributing to tissue stress; in turn these factors may affect healing in a clinical setting. Additional studies will investigate possible correlates between FEM and clinically relevant in vivo studies to further validate the models.},
 bibtype = {inproceedings},
 author = {Nováček, Vit and Trần, T N and Bronson, D and Diederich, J and Godek, M and Klinge, Uwe and Miesse, A and Staat, Manfred and Tolba, R},
 booktitle = {TERMIS-AP 2011, Proceedings of the annual meeting of the Asia Pacific Chapter of the Tissue Engineering and Regenerative Medicine International Society, Singapore, August 3-5, 2011}
}

Background Following surgical intervention, establishing GI tract continuity remains challenging due to limited knowledge regarding device effects on tissue. Significant effort has been directed toward creating reliable tissue apposition via mechanical devices, i.e., staplers. These instruments have a lengthy history of clinical use even though their impact on tissue response and healing remain unclear. This study investigates tissue response to several stapling modalities which may influence tissue regeneration and healing. Methods We developed finite element models (FEM) utilizing circular staplers often employed in GI tissue to investigate the influence of the number of staple rows (one, two, three) wire size, closed height and tissue thickness on stress within the tissues. Results For equivalent closed staple height and initial tissue thickness, each additional outer row increased the compressive stress within the tissues in the inner row(s). Smaller staple wire resulted in lower tissue stress compared to larger wire. Conclusion FEM demonstrated differences between stapling modalities tested; staple row number and wire gauge were significant factors contributing to tissue stress; in turn these factors may affect healing in a clinical setting. Additional studies will investigate possible correlates between FEM and clinically relevant in vivo studies to further validate the models.

@article{
 title = {Analysis of the long-term effect of the MBST® nuclear magnetic resonance therapy on gonarthrosis},
 type = {article},
 year = {2011},
 pages = {521-528},
 volume = {47},
 websites = {http://www.thebodyworksclinic.com/wp-content/uploads/2015/03/study-knee-long-term-2011.pdf},
 id = {93892463-d1ab-375e-a5b8-fcbb95e415f5},
 created = {2016-11-11T16:12:25.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-06-08T10:52:22.021Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Levers2011},
 private_publication = {false},
 abstract = {Based on a questionnaire for patient-queries regarding pain-sensation and activity restrictions during everyday tasks, the long-term effect of MBST® nuclear magnetic resonance therapy is studied in osteoarthritis of the knee. 39 patients, whose therapy dates back up to four years, participated in the study. In addition to an overall view, the success of this therapy is also analyzed regarding age, gender and physical activities. Overall, the study pointed out a sustained improvement in the patients’ local health-status with a significant pain-relief even after four years, but also with a slight increase in pain towards the end of that four-year period. There tends to be a more positive effect on women, on elderly or also on even non-sports-active patients which suggests a possible influence by daily (over)-stressing on the success of the therapy on bone density is also conceivable, however this remains open.},
 bibtype = {article},
 author = {Levers, Andrea and Staat, Manfred and van Laack, Walter},
 journal = {Orthopedic Practice},
 number = {11}
}

Based on a questionnaire for patient-queries regarding pain-sensation and activity restrictions during everyday tasks, the long-term effect of MBST® nuclear magnetic resonance therapy is studied in osteoarthritis of the knee. 39 patients, whose therapy dates back up to four years, participated in the study. In addition to an overall view, the success of this therapy is also analyzed regarding age, gender and physical activities. Overall, the study pointed out a sustained improvement in the patients’ local health-status with a significant pain-relief even after four years, but also with a slight increase in pain towards the end of that four-year period. There tends to be a more positive effect on women, on elderly or also on even non-sports-active patients which suggests a possible influence by daily (over)-stressing on the success of the therapy on bone density is also conceivable, however this remains open.

@article{
 title = {Modified stapler configuration for optimisation of colonic anastomosis},
 type = {article},
 year = {2011},
 pages = {S31},
 volume = {98 Suppl 5},
 websites = {https://academic.oup.com/bjs/article/98/Supplement_5/S1/6150540,http://www.ncbi.nlm.nih.gov/pubmed/21618754},
 month = {6},
 day = {25},
 id = {51bb0e44-78b6-3b52-86d2-cefc36904172},
 created = {2021-04-19T16:46:36.601Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-04-19T16:46:36.601Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Klinge2011},
 private_publication = {false},
 abstract = {ESSR Abstracts 2011. Abstracts of the 46th Congress of the European Society for Surgical Research. Aachen, Germany. May 25-28, 2011.},
 bibtype = {article},
 author = {Klinge, Uwe and Trần, T. Ngọc and Nováček, Vit and Staat, Manfred and Alizai, Patrick and Miesse, A.M. and Tolba, Rene},
 doi = {10.1002/bjs.7577},
 journal = {The British Journal of Surgery},
 number = {Supplement_5}
}

ESSR Abstracts 2011. Abstracts of the 46th Congress of the European Society for Surgical Research. Aachen, Germany. May 25-28, 2011.

@inproceedings{
 title = {Virtual needle simulation with haptics for regional anaesthesia},
 type = {inproceedings},
 year = {2010},
 keywords = {Artificial,Life and Medical Sciences,Multimedia Information Systems,and virtual realities,augmented},
 pages = {1-3},
 websites = {http://www.hpv.cs.bangor.ac.uk/vr10-med/Papers/Ullrich-VirtualNeedleSimulation.pdf,http://www.fg-medvis.de/dokuwiki/lib/exe/fetch.php?media=medvisaward:2010:ullrich_submission_b.pdf},
 id = {8e32ace9-6d0a-321d-afe5-5e386b9615f9},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-01-01T21:52:36.684Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {ullrich2010virtual},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {This paper reports about an ongoing research project, called RASim. The goal of this project is to develop a virtual realitybased training tool for regional anaesthesia. A production pipeline to create patient-specific datasets has been established. A prototype of the simulator has been implemented on a virtual reality-platform and was evaluated in a first study. The current research and development is focused on soft-tissue simulation and haptics to improve the interaction. Furthermore, a bi-manual interaction scheme to combine palpation and virtual needle guidance is introduced as conceptual work and will be evaluated soon},
 bibtype = {inproceedings},
 author = {Ullrich, Sebastian and Grottke, Oliver and Rossaint, Rolf and Staat, Manfred and Deserno, Thomas M and Kuhlen, Torsten},
 booktitle = {Proc. of the IEEE Virtual Reality 2010, Workshop on Medical Virtual Environments, Waltham, MA, USA, March 21, 2010}
}

This paper reports about an ongoing research project, called RASim. The goal of this project is to develop a virtual realitybased training tool for regional anaesthesia. A production pipeline to create patient-specific datasets has been established. A prototype of the simulator has been implemented on a virtual reality-platform and was evaluated in a first study. The current research and development is focused on soft-tissue simulation and haptics to improve the interaction. Furthermore, a bi-manual interaction scheme to combine palpation and virtual needle guidance is introduced as conceptual work and will be evaluated soon

@inproceedings{
 title = {An upper bound algorithm for shakedown analysis of elastic-plastic bounded linearly kinematic hardening bodies},
 type = {inproceedings},
 year = {2010},
 websites = {https://www.eccm-2010.org/complet/fullpaper_901.pdf},
 institution = {European Conference on Computational Mechanics},
 id = {0fe54a41-8554-3470-8c44-b57f15477a39},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {pham2010eccm},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {By means of FEM, we derive here an upper bound algorithm for bounded linear kinematic hardening bodies. The existing yield surface can translate within stress space, but it is bounded such that its centre can not move outside the back stress surface.},
 bibtype = {inproceedings},
 author = {Phạm, Phú Tình and Vũ, Đức Khôi and Trần, Thanh Ngọc and Staat, Manfred},
 booktitle = {Proceedings ECCM 2010, IV European Conference on Computational Mechanics, Paris, France, May 16-21, 2010}
}

By means of FEM, we derive here an upper bound algorithm for bounded linear kinematic hardening bodies. The existing yield surface can translate within stress space, but it is bounded such that its centre can not move outside the back stress surface.

@inproceedings{
 title = {Shakedown analysis of two dimensional structures by an edge-based smoothed finite element method},
 type = {inproceedings},
 year = {2010},
 websites = {https://www.eccm-2010.org/complet/fullpaper_1042.pdf},
 institution = {European Conference on Computational Mechanics},
 id = {0d205ad8-1274-3ba0-9818-76326290040d},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2010eccm},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {.An edge-based smoothed finite element method (ES-FEM) is extended for limit and shakedown analysis of structures. A primal-dual algorithm which is based upon the von Mises yield criterion and a nonlinear optimization procedure is used to calculate both the upper and lower bounds of the plastic collapse limit and the shakedown limit. Using a constant smoothing function which leads to local constant smoothing domains constructed on edges of elements, only one Gaussian point is required for each domain ensuring that the total number of variables in the resulting optimization problem is kept to a minimum compared with standard finite element formulation. Numerical examples are presented to show that stable and accurate solutions are obtained by the present method.},
 bibtype = {inproceedings},
 author = {Trần, Thanh Ngọc and Staat, Manfred},
 booktitle = {Proceedings ECCM 2010, IV European Conference on Computational Mechanics, Paris, France, May 16-21, 2010}
}

.An edge-based smoothed finite element method (ES-FEM) is extended for limit and shakedown analysis of structures. A primal-dual algorithm which is based upon the von Mises yield criterion and a nonlinear optimization procedure is used to calculate both the upper and lower bounds of the plastic collapse limit and the shakedown limit. Using a constant smoothing function which leads to local constant smoothing domains constructed on edges of elements, only one Gaussian point is required for each domain ensuring that the total number of variables in the resulting optimization problem is kept to a minimum compared with standard finite element formulation. Numerical examples are presented to show that stable and accurate solutions are obtained by the present method.

@inproceedings{
 title = {A hyperelastic model of biological tissue materials in tubular organs},
 type = {inproceedings},
 year = {2010},
 websites = {https://www.eccm-2010.org/complet/fullpaper_1079.pdf},
 institution = {European Conference on Computational Mechanics},
 id = {73883cd8-6744-3831-b26e-50493fa80eb8},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {nguyen2010eccm},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {The distribution of collagen fibers in various biological tissues has been well defined in the literature. In order to simulate the behavior of biological tissues, the material symmetry and heterogeneity, such as fiber directions and layered structure, respectively must be taken into account. The paper presents a new orthotropic material model for tubular organs. This is a fiber-reinforced material with two fiber families. In each layer, there are five material parameters for both isotropic and anisotropic parts. Hence, the behavior of the material is easily defined by experiments in the principal basis. On the other side, the model satisfies the fundamental conditions for a strain energy function, i.e., the energy and the stresses vanish in the reference configuration. As a result, the model is suitable to simulate soft tissue materials with collagen fibers such as ureter, urethra, intestine, arteries, etc.},
 bibtype = {inproceedings},
 author = {Nguyễn, N H and Raatschen, Hans-Jürgen and Staat, Manfred},
 booktitle = {Proceedings ECCM 2010, IV European Conference on Computational Mechanics, Paris, France, May 16-21, 2010}
}

The distribution of collagen fibers in various biological tissues has been well defined in the literature. In order to simulate the behavior of biological tissues, the material symmetry and heterogeneity, such as fiber directions and layered structure, respectively must be taken into account. The paper presents a new orthotropic material model for tubular organs. This is a fiber-reinforced material with two fiber families. In each layer, there are five material parameters for both isotropic and anisotropic parts. Hence, the behavior of the material is easily defined by experiments in the principal basis. On the other side, the model satisfies the fundamental conditions for a strain energy function, i.e., the energy and the stresses vanish in the reference configuration. As a result, the model is suitable to simulate soft tissue materials with collagen fibers such as ureter, urethra, intestine, arteries, etc.

@article{
 title = {A new model for blunt liver injuries in the swine},
 type = {article},
 year = {2010},
 keywords = {Coagulopathy,Haemorrhage,Haemostatic agents,Liver,Pig,Trauma},
 pages = {65-73},
 volume = {44},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/19996600,http://www.karger.com/doi/10.1159/000265053},
 month = {1},
 publisher = {Karger Publishers},
 id = {d576503b-7e97-3d26-94f7-86ba8cba839b},
 created = {2014-06-02T18:47:20.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-30T15:59:38.195Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {grottke2009new},
 source_type = {article},
 private_publication = {false},
 abstract = {BACKGROUND: To elaborate the impact of new haemostatic agents we developed an instrument for the pressure-controlled induction of blunt liver injuries in a porcine animal model. MATERIALS AND METHODS: A dilutional coagulopathy of 80% of animal blood volume was induced in 9 anaesthetized pigs. Animals were randomly assigned to be injured with a force of 112 Newton (N) (n = 1), 224 +/- 19 N (n = 4) or 355 +/- 35 N (n = 4). The impact of injury was measured by blood loss, survival time and coagulation parameters. Liver histology was obtained to evaluate the degree of liver injury. RESULTS: The profound haemodilution resulted in a significant alteration of all coagulation parameters. After inflicting the injury with 355 +/- 35 N, both the survival time (30 +/- 9 min; p = 0.006) and blood loss (68 +/- 16 ml min(-1), p = 0.002) were significantly different as compared to injuries with 224 +/- 19 N (survival time: 76 +/- 20 min, blood loss: 23 +/- 4 ml min(-1)). In contrast, an injury with 112 N led to an insignificant blood loss of only 239 ml. CONCLUSION: We developed a pressure-controlled clamp that allows for the induction of blunt liver traumas with highly reproducible injuries with a positive correlation with blood loss and survival.},
 bibtype = {article},
 author = {Grottke, Oliver and Braunschweig, T. and Philippen, B. and Gatzweiler, K.H. and Gronloh, N. and Staat, Manfred and Rossaint, Rolf and Tolba, Rene},
 doi = {10.1159/000265053},
 journal = {European Surgical Research},
 number = {2}
}

BACKGROUND: To elaborate the impact of new haemostatic agents we developed an instrument for the pressure-controlled induction of blunt liver injuries in a porcine animal model. MATERIALS AND METHODS: A dilutional coagulopathy of 80% of animal blood volume was induced in 9 anaesthetized pigs. Animals were randomly assigned to be injured with a force of 112 Newton (N) (n = 1), 224 +/- 19 N (n = 4) or 355 +/- 35 N (n = 4). The impact of injury was measured by blood loss, survival time and coagulation parameters. Liver histology was obtained to evaluate the degree of liver injury. RESULTS: The profound haemodilution resulted in a significant alteration of all coagulation parameters. After inflicting the injury with 355 +/- 35 N, both the survival time (30 +/- 9 min; p = 0.006) and blood loss (68 +/- 16 ml min(-1), p = 0.002) were significantly different as compared to injuries with 224 +/- 19 N (survival time: 76 +/- 20 min, blood loss: 23 +/- 4 ml min(-1)). In contrast, an injury with 112 N led to an insignificant blood loss of only 239 ml. CONCLUSION: We developed a pressure-controlled clamp that allows for the induction of blunt liver traumas with highly reproducible injuries with a positive correlation with blood loss and survival.

@inbook{
 type = {inbook},
 year = {2009},
 pages = {135-156},
 volume = {1},
 websites = {http://www.springerlink.com/index/10.1007/978-1-4020-9634-1_7,http://link.springer.com/10.1007/978-1-4020-9634-1_7},
 publisher = {Springer Netherlands},
 city = {Dordrecht},
 id = {56a52714-9b4b-3cfd-b86f-0e87d2242419},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-09-16},
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 last_modified = {2019-05-22T20:32:27.961Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2009reliability},
 source_type = {incollection},
 private_publication = {false},
 abstract = {This paper concerns the development of a primal-dual algorithm for limit and shakedown analysis of Reissner-Mindlin plates made of von Mises material. At each optimization iteration, the lower bound of the shakedown load multiplier is calculated simultaneously with the upper bound using the duality theory. An edge-based smoothed finite element method (ES-FEM) combined with the discrete shear gap (DSG) technique is used to improve the accuracy of the solutions and to avoid the transverse shear locking behaviour. The method not only possesses all inherent features of convergence and accuracy from ES-FEM, but also ensures that the total number of variables in the optimization problem is kept to a minimum compared with the standard finite element formulation. Numerical examples are presented to demonstrate the effectiveness of the present method.},
 bibtype = {inbook},
 author = {Trần, T.N. and Phạm, P.T. and Vũ, ÐK and Staat, Manfred},
 editor = {Dieter, Weichert and Alan, Ponter},
 doi = {10.1007/978-1-4020-9634-1_7},
 chapter = {Reliability analysis of inelastic shell structures under variable loads},
 title = {Limit States of Materials and Structures}
}

This paper concerns the development of a primal-dual algorithm for limit and shakedown analysis of Reissner-Mindlin plates made of von Mises material. At each optimization iteration, the lower bound of the shakedown load multiplier is calculated simultaneously with the upper bound using the duality theory. An edge-based smoothed finite element method (ES-FEM) combined with the discrete shear gap (DSG) technique is used to improve the accuracy of the solutions and to avoid the transverse shear locking behaviour. The method not only possesses all inherent features of convergence and accuracy from ES-FEM, but also ensures that the total number of variables in the optimization problem is kept to a minimum compared with the standard finite element formulation. Numerical examples are presented to demonstrate the effectiveness of the present method.

@article{
 title = {Probabilistic limit and shakedown analysis of thin plates and shells},
 type = {article},
 year = {2009},
 keywords = {Design point,First-order reliability method,Limit analysis,Second-order reliability method,Sequential quadratic programming,Shakedown analysis},
 pages = {1-18},
 volume = {31},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0167473007000689},
 month = {1},
 publisher = {Elsevier},
 id = {6ee29261-3950-3ac5-a8f3-f0edb5017ada},
 created = {2014-06-02T18:44:50.000Z},
 accessed = {2014-06-02},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2021-08-05T21:51:57.954Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2009probabilistic},
 source_type = {article},
 notes = {No. 14 of the TOP25 list of most read articles in Structural Safety in October-December 2008},
 private_publication = {false},
 abstract = {The reliability analysis of plates and shells with respect to plastic collapse or to inadaptation is formulated on the basis of limit and shakedown theorems. Based on a direct definition of the limit state function, the non-linear problems may be efficiently solved by using the first and second-order reliability methods (FORM/SORM). In order to get the design point, a non-linear optimisation was implemented. Sensitivity analyses are obtained numerically from a mathematical problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, computing costs and the numerical error. Numerical examples are presented to show the validity and effectiveness of the present method. © 2007 Elsevier Ltd. All rights reserved.},
 bibtype = {article},
 author = {Trần, Thanh Ngoc and Kreißig, R. and Staat, M.},
 doi = {10.1016/j.strusafe.2007.10.003},
 journal = {Structural Safety},
 number = {1}
}

The reliability analysis of plates and shells with respect to plastic collapse or to inadaptation is formulated on the basis of limit and shakedown theorems. Based on a direct definition of the limit state function, the non-linear problems may be efficiently solved by using the first and second-order reliability methods (FORM/SORM). In order to get the design point, a non-linear optimisation was implemented. Sensitivity analyses are obtained numerically from a mathematical problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, computing costs and the numerical error. Numerical examples are presented to show the validity and effectiveness of the present method. © 2007 Elsevier Ltd. All rights reserved.

@inbook{
 type = {inbook},
 year = {2009},
 keywords = {Soft tissues,bulge test,modified Kilian model,rubber},
 pages = {465-470},
 websites = {http://www.crcnetbase.com/doi/abs/10.1201/NOE0415563277.ch76,https://www.taylorfrancis.com/books/9780203862223/chapters/10.1201/NOE0415563277-90,https://www.taylorfrancis.com/books/9781135182168,https://www.taylorfrancis.com/books/9780203862223},
 month = {9},
 publisher = {CRC Press},
 day = {1},
 city = {Lodon, Boca Raton},
 id = {427ca273-ab9c-3c79-811d-59d4b5c11baf},
 created = {2018-12-27T15:47:45.326Z},
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 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Sponagel2009},
 folder_uuids = {4220b649-bc14-4170-b767-031fdc0b6161},
 private_publication = {false},
 abstract = {The bulge test is an efficient but simple biaxial setup using only a mittimum of biological material. This experiment is well suited to measure stretches in thin-walled materials such as rubber membranes, chorioamnion, bladder or intestinal lissue, etc. up to the ultimate stretch. The principal stretches are easily calculated from the experirnental data, especially when the tested material shows isotropic behavior. The growth of biological tissue generates residual stresses which can be also measured with the bulge test. Tests with small specimens also permit local measurements of inhomogeneous tissues. In the paper, the small size bulge test is first developed with elastomers. For fitting of the data a modified version of the Kilian network is proposed for hyperelastic modeling of rubberlike materials. This strain·energy function represents both entropic elasticity and in addition energetic elasticity. Fitting the results shows that the proposed model, with only two material constants, can describe the behavior of rubberlike materials up to large elastic strains as accurate as the Ogden model with four or even six material constants. In a second phase the bulge test is used to test planar soft biopolymers or tissues.},
 bibtype = {inbook},
 author = {Sponagel, Stefan and Nguyên, Huynh Như and Staat, Manfred},
 editor = {Heinrich, Gert and Kaliske, Michael and Lion, Alexander and Reese, Stefanie},
 doi = {10.1201/NOE0415563277},
 chapter = {Experiment and material model for soft tissue materials},
 title = {Constitutive Models for Rubber VI}
}

The bulge test is an efficient but simple biaxial setup using only a mittimum of biological material. This experiment is well suited to measure stretches in thin-walled materials such as rubber membranes, chorioamnion, bladder or intestinal lissue, etc. up to the ultimate stretch. The principal stretches are easily calculated from the experirnental data, especially when the tested material shows isotropic behavior. The growth of biological tissue generates residual stresses which can be also measured with the bulge test. Tests with small specimens also permit local measurements of inhomogeneous tissues. In the paper, the small size bulge test is first developed with elastomers. For fitting of the data a modified version of the Kilian network is proposed for hyperelastic modeling of rubberlike materials. This strain·energy function represents both entropic elasticity and in addition energetic elasticity. Fitting the results shows that the proposed model, with only two material constants, can describe the behavior of rubberlike materials up to large elastic strains as accurate as the Ogden model with four or even six material constants. In a second phase the bulge test is used to test planar soft biopolymers or tissues.

@article{
 title = {Upper bound limit and shakedown analysis of thin plates and shells},
 type = {article},
 year = {2008},
 keywords = {Exact Ilyushin yield surface,Limit analysis,Nonlinear programming,Shakedown analysis,Shells},
 pages = {1683-1695},
 volume = {86},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0045794908000461},
 month = {9},
 id = {2d6ec472-1b6b-3c05-9e63-6779f8333d4c},
 created = {2014-06-02T18:47:19.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.337Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Tran2008},
 private_publication = {false},
 abstract = {This paper concerns the development of a kinematic formulation for the finite element limit and shakedown analysis of shells. The technique is based upon an upper bound approach using the re-parameterized exact Ilyushin yield surface and a nonlinear optimization procedure. The solution of the problem is obtained by discretizing the shell into finite elements. Numerical examples are presented to show the validity of the present method.},
 bibtype = {article},
 author = {Tran, Thanh Ngọc and Kreißig, Reiner and Vu, Duc Khôi and Staat, Manfred},
 doi = {10.1016/j.compstruc.2008.02.005},
 journal = {Computers & Structures},
 number = {17-18}
}

This paper concerns the development of a kinematic formulation for the finite element limit and shakedown analysis of shells. The technique is based upon an upper bound approach using the re-parameterized exact Ilyushin yield surface and a nonlinear optimization procedure. The solution of the problem is obtained by discretizing the shell into finite elements. Numerical examples are presented to show the validity of the present method.

@article{
 title = {Load bearing capacity of thin shell structures made of elastoplastic material by direct methods},
 type = {article},
 year = {2008},
 pages = {299-309},
 volume = {28},
 websites = {http://www.uni-magdeburg.de/ifme/zeitschrift_tm/2008_Heft3_4/13_Staat_Kreissig_Tran.pdf},
 publisher = {Universität Magdeburg},
 id = {03a8cb28-d923-35a9-b2ef-69c9f1c5b3c0},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2008load},
 source_type = {article},
 private_publication = {false},
 abstract = {A method is introduced to determine the limit load of thin shells using the finite element method. The method is based on an upper bound limit and shake down analysis with the elastic-perfectly plastic material model. A nonlinear constrained optimization problem is solved by using Newton’s method in conjunction with a penalty method and the Lagrange dual method. The numerical investigation of a pipe bend subjected to bending moments proves the effectiveness of the algorithm.},
 bibtype = {article},
 author = {Trần, Ngọc Thanh and Kreißig, Reiner and Staat, Manfred},
 journal = {Technische Mechanik},
 number = {3-4}
}

A method is introduced to determine the limit load of thin shells using the finite element method. The method is based on an upper bound limit and shake down analysis with the elastic-perfectly plastic material model. A nonlinear constrained optimization problem is solved by using Newton’s method in conjunction with a penalty method and the Lagrange dual method. The numerical investigation of a pipe bend subjected to bending moments proves the effectiveness of the algorithm.

@inbook{
 type = {inbook},
 year = {2008},
 pages = {253-315},
 websites = {http://www.springerlink.com/index/10.1007/978-3-540-75409-1,http://link.springer.com/10.1007/978-3-540-75409-1},
 publisher = {Springer Berlin Heidelberg},
 city = {Berlin, Heidelberg},
 chapter = {Soft materials in technology and biology: characteristics, properties and parameter identification},
 id = {8b117ea5-6e4d-34d6-ab6c-3c410ca1f561},
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 source_type = {incollection},
 folder_uuids = {4220b649-bc14-4170-b767-031fdc0b6161},
 private_publication = {false},
 abstract = {The growing interest in flexible structures has also brought biomechanics into the focus of engineers. Elastomers and soft tissues consist of similar networks of macromolecules. After a brief introduction to the concepts of continuum mechanics, typical isotropic models of soft materials in technology and biology are presented. Similarities and differences of the thermo-mechanical behavior are discussed. For rubber-like materials a modification of the Kilian network is suggested which greatly simplifies the identification of material parameters. Finally the dynamical loading of biopolymers and volume changes with phase transitions are considered.},
 bibtype = {inbook},
 author = {Staat, Manfred and Baroud, Gamal and Topcu, Murat and Sponagel, Stepahn},
 editor = {Artmann, Gerhard M and Chien, Shu},
 doi = {10.1007/978-3-540-75409-1_12},
 title = {Bioengineering in Cell and Tissue Research}
}

The growing interest in flexible structures has also brought biomechanics into the focus of engineers. Elastomers and soft tissues consist of similar networks of macromolecules. After a brief introduction to the concepts of continuum mechanics, typical isotropic models of soft materials in technology and biology are presented. Similarities and differences of the thermo-mechanical behavior are discussed. For rubber-like materials a modification of the Kilian network is suggested which greatly simplifies the identification of material parameters. Finally the dynamical loading of biopolymers and volume changes with phase transitions are considered.

@inproceedings{
 title = {Reliability analysis of shells based on direct plasticity methods},
 type = {inproceedings},
 year = {2008},
 keywords = {First-order reliability method FORM,Limit analysis,Second-order reliability method SORM,Sensitivity,Shakedown analysis},
 pages = {1-2},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/257/},
 id = {fdaf7777-238d-3229-8ec3-e8237f9b479f},
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 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2008reliability},
 source_type = {inproceedings},
 notes = {paper a1486},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Trần, Thanh Ngọc and Phạm, Phú Tình and Staat, Manfred},
 editor = {Schrefler, Bernhard A. and Perego, Umberto},
 booktitle = {CD-ROM Proceedings of 8th World Congress on Computational Mechanics (WCCM8) 5th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008) June 30 – July 4, 2008, Venice, Italy}
}

@inproceedings{
 title = {Material parameters of the reindeer antler for use in dental implant biomechanics},
 type = {inproceedings},
 year = {2008},
 keywords = {antler bone,dental implant,frictional coefficien},
 websites = {http://wodan.meb.uni-bonn.de/forsch/poster/cmbbe_2008_porto/cmbbe2008-hasan.pdf},
 id = {381e1c76-7e0c-378f-a927-4e055d445b3e},
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 file_attached = {false},
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 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {hasan2008arup},
 source_type = {inproceedings},
 notes = {poster 146, ARUP prize for best poster presentation by Istabrak Hasan},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Hasan, Istabrak and Reimann, S and Rahimi, A and Keilig, Ludger and Staat, Manfred and Bourauel, Christoph},
 booktitle = {CD-ROM proceedings of the 8th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering. Porto, Portugal, 27th February-1st March 2008}
}

@article{
 title = {The use of open source software in biomechanical finite element analysis},
 type = {article},
 year = {2008},
 pages = {213-220},
 volume = {7/8},
 id = {b92d9f1e-a8ee-34c2-bb70-68367303e2d2},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
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 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {ciobanu2008},
 source_type = {article},
 private_publication = {false},
 bibtype = {article},
 author = {Ciobanu, Octavian and Staat, Manfred and Rahimi, A},
 journal = {Buletinul Institutului Politehnic Din Iaşi},
 number = {4}
}

@inproceedings{
 title = {Limit and shakedown reliability analysis by nonlinear programming},
 type = {inproceedings},
 year = {2008},
 keywords = {First an,Limit and shakedown reliability analysis},
 pages = {354-358},
 volume = {1},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/258/},
 institution = {Минск: Изд. центр БГУ},
 id = {004d3118-34e3-3bfb-a32c-8470cfdaeac3},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat2008relmas},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Analysis of advanced structures working under extreme heavy loading such as nuclear power plants and piping system should take into account the randomness of loading, geometrical and material parameters. The existing reliability are restricted mostly to the elastic working regime, e.g. allowable local stresses. Development of the limit and shakedown reliability-based analysis and design methods, exploiting potential of the shakedown working regime, is highly needed. In this paper the application of a new algorithm of probabilistic limit and shakedown analysis for shell structures is presented, in which the loading and strength of the material as well as the thickness of the shell are considered as random variables. The reliability analysis problems may be efficiently solved by using a system combining the available FE codes, a deterministic limit and shakedown analysis, and the First and Second Order Reliability Methods (FORM/SORM). Non-linear sensitivity analyses are obtained directly from the solution of the deterministic problem without extra computational costs.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Trần, Thanh Ngọc and Phạm, Phú Tình},
 booktitle = {Assessment of Reliability of Materials and Structures: Problems and Solutions. Proceedings of RELMAS 2008, June 17-20, 2008, Saint Petersburg State Polytechnical University, Russia}
}

Analysis of advanced structures working under extreme heavy loading such as nuclear power plants and piping system should take into account the randomness of loading, geometrical and material parameters. The existing reliability are restricted mostly to the elastic working regime, e.g. allowable local stresses. Development of the limit and shakedown reliability-based analysis and design methods, exploiting potential of the shakedown working regime, is highly needed. In this paper the application of a new algorithm of probabilistic limit and shakedown analysis for shell structures is presented, in which the loading and strength of the material as well as the thickness of the shell are considered as random variables. The reliability analysis problems may be efficiently solved by using a system combining the available FE codes, a deterministic limit and shakedown analysis, and the First and Second Order Reliability Methods (FORM/SORM). Non-linear sensitivity analyses are obtained directly from the solution of the deterministic problem without extra computational costs.

@inbook{
 type = {inbook},
 year = {2008},
 pages = {253-315},
 websites = {http://link.springer.com/10.1007/978-3-540-75409-1_12},
 publisher = {Springer},
 city = {Berlin, Heidelberg},
 chapter = {Soft materials in technology and biology – characteristics, properties, and parameter identification},
 id = {b1a2fe01-68b8-3633-8d31-88f2503f964b},
 created = {2018-12-22T14:08:35.384Z},
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 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2008},
 private_publication = {false},
 abstract = {The growing interest in flexible structures has also brought biomechanics into the focus of engineers. Elastomers and soft tissues consist of similar networks of macromolecules. After a brief introduction to the concepts of continuum mechanics, typical isotropic models of soft materials in technology and biology are presented. Similarities and differences of the thermo-mechanical behavior are discussed. For rubber-like materials a modification of the Kilian network is suggested which greatly simplifies the identification of material parameters. Finally the dynamical loading of biopolymers and volume changes with phase transitions are considered.},
 bibtype = {inbook},
 author = {Staat, Manfred and Baroud, Gamal and Topcu, Murat and Sponagel, Stefan},
 editor = {Artmann, Gerhard M and Chien, Shu},
 doi = {10.1007/978-3-540-75409-1_12},
 title = {Bioengineering in Cell and Tissue Research}
}

The growing interest in flexible structures has also brought biomechanics into the focus of engineers. Elastomers and soft tissues consist of similar networks of macromolecules. After a brief introduction to the concepts of continuum mechanics, typical isotropic models of soft materials in technology and biology are presented. Similarities and differences of the thermo-mechanical behavior are discussed. For rubber-like materials a modification of the Kilian network is suggested which greatly simplifies the identification of material parameters. Finally the dynamical loading of biopolymers and volume changes with phase transitions are considered.

@inbook{
 type = {inbook},
 year = {2008},
 pages = {527-539},
 websites = {http://link.springer.com/10.1007/978-3-540-75409-1_22},
 publisher = {Springer Berlin Heidelberg},
 city = {Berlin, Heidelberg},
 chapter = {Percutaneous vertebroplasty: a review of two intraoperative complications},
 id = {f54d3d12-063a-327e-9e73-2d619480b76f},
 created = {2018-12-22T14:08:35.388Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2019-05-22T20:32:27.841Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Vant2008},
 private_publication = {false},
 abstract = {Vertebroplasty is an interventional radiology procedure used to treat vertebral compression fractures. It shows promising results but has two major drawbacks: the excessive injection pressure and the risk for extraosseus cement leakage. To examine each of these problems, vertebroplasty is divided into intra- and extravertebral components. The excessive injection pressure is an extravertebral problem because 95% of the injection pressure is extravertebral. Extant solutions are cement delivery devices and lowering the cement viscosity. Additionally, the cannula can be redesigned to lower the friction and injection pressure. The extraosseus cement leakage is an intravertebral problem. Literature recommends delaying the injection to increase the control over the infiltration of cement; this hypothesis is tested using a synthetic model. The bone cement has complex rheological properties, which are modified by altering the cement preparation and composition; these may also play a role in controlling cement leakage. Combining the findings, conflicting demands on the cement viscosity are clearly demonstrated; the extravertebral component demands low-viscosity cement while the intravertebral component demands high-viscosity cement. The challenge is therefore to develop biomaterials, techniques and/or devices that can control the conflicting demands on cement viscosity.},
 bibtype = {inbook},
 author = {Vant, Christianne and Staat, Manfred and Baroud, Gamal},
 editor = {Artmann, Gerhard M. and Chien, Shu},
 doi = {10.1007/978-3-540-75409-1_22},
 title = {Bioengineering in Cell and Tissue Research}
}

Vertebroplasty is an interventional radiology procedure used to treat vertebral compression fractures. It shows promising results but has two major drawbacks: the excessive injection pressure and the risk for extraosseus cement leakage. To examine each of these problems, vertebroplasty is divided into intra- and extravertebral components. The excessive injection pressure is an extravertebral problem because 95% of the injection pressure is extravertebral. Extant solutions are cement delivery devices and lowering the cement viscosity. Additionally, the cannula can be redesigned to lower the friction and injection pressure. The extraosseus cement leakage is an intravertebral problem. Literature recommends delaying the injection to increase the control over the infiltration of cement; this hypothesis is tested using a synthetic model. The bone cement has complex rheological properties, which are modified by altering the cement preparation and composition; these may also play a role in controlling cement leakage. Combining the findings, conflicting demands on the cement viscosity are clearly demonstrated; the extravertebral component demands low-viscosity cement while the intravertebral component demands high-viscosity cement. The challenge is therefore to develop biomaterials, techniques and/or devices that can control the conflicting demands on cement viscosity.

@inproceedings{
 title = {Finite element shakedown and limit reliability analysis of thin shells},
 type = {inproceedings},
 year = {2007},
 keywords = {First Order Reliabib,exact Ilyushin yield surface},
 pages = {186-189},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2007/233/},
 institution = {CIMNE, Barcelona},
 id = {0b88a293-beec-387b-997c-833e42107c92},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-30T15:59:38.088Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {tran2007finite},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {A procedure for the evaluation of the failure probability of elastic-plastic thin shell structures is presented. The procedure involves a deterministic limit and shakedown analysis for each probabilistic iteration which is based on the kinematical approach and the use the exact Ilyushin yield surface. Based on a direct definition of the limit state function, the non-linear problems may be efficiently solved by using the First and Second Order Reliabiblity Methods (Form/SORM). This direct approach reduces considerably the necessary knowledge of uncertain technological input data, computing costs and the numerical error.},
 bibtype = {inproceedings},
 author = {Trần, Thanh Ngọc and Staat, Manfred and Kreißig, Reiner},
 editor = {Oñate, Eugenio and Owen, D R J and Suárez, B},
 booktitle = {Computational Plasticity. Fundamentals and Applications. COMPLAS IX. Part 1. International Center for Numerical Methods in Engineering (CIMNE), September 5-7, 2007, Barcelona, Spain}
}

A procedure for the evaluation of the failure probability of elastic-plastic thin shell structures is presented. The procedure involves a deterministic limit and shakedown analysis for each probabilistic iteration which is based on the kinematical approach and the use the exact Ilyushin yield surface. Based on a direct definition of the limit state function, the non-linear problems may be efficiently solved by using the First and Second Order Reliabiblity Methods (Form/SORM). This direct approach reduces considerably the necessary knowledge of uncertain technological input data, computing costs and the numerical error.

@article{
 title = {Mechanical modeling and testing of biological membranes},
 type = {article},
 year = {2007},
 pages = {572-573},
 volume = {2},
 month = {9},
 publisher = {Future Medicine Ltd},
 id = {0b17e40e-ef58-32f9-a918-93f6bdedcb41},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-10-17T17:34:53.192Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat2007topcu},
 source_type = {article},
 private_publication = {false},
 bibtype = {article},
 author = {Staat, Manfred and Topcu, Murat and Sponagel, Stefan},
 journal = {Regenerative Medicine},
 number = {5}
}

@inproceedings{
 title = {Calculation of load carrying capacity of shell structures with elasto-plastic material by direct methods},
 type = {inproceedings},
 year = {2007},
 keywords = {Ilyushin yield surface,limit analysis,shakedown analysis,shells},
 pages = {1-8},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2007/227/},
 id = {ba8e2a23-7ac0-315e-87d4-5ac103d03295},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {trancalculation},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {In this paper, a method is introduced to determine the limit load of general shells using the finite element method. The method is based on an upper bound limit and shakedown analysis with elastic-perfectly plastic material model. A non-linear constrained optimisation problem is solved by using Newton’s method in conjunction with a penalty method and the Lagrangean dual method. Numerical investigation of a pipe bend subjected to bending moments proves the effectiveness of the algorithm.},
 bibtype = {inproceedings},
 author = {Tran, Thanh Ngoc and Staat, Manfred and Kreißig, Reiner},
 booktitle = {CD-ROM Proceedings of the International Conference on Material Theory and Nonlinear Dynamics. MatDyn 2007. Hanoi, Vietnam, Sept. 24-26, 2007}
}

In this paper, a method is introduced to determine the limit load of general shells using the finite element method. The method is based on an upper bound limit and shakedown analysis with elastic-perfectly plastic material model. A non-linear constrained optimisation problem is solved by using Newton’s method in conjunction with a penalty method and the Lagrangean dual method. Numerical investigation of a pipe bend subjected to bending moments proves the effectiveness of the algorithm.

@article{
 title = {Elektromyographische Untersuchungen zur Kräftigung der Oberschenkelmuskulatur mit einem myoelektrischen Stimulator nach arthroskopischen Eingriffen am Kniegelenk},
 type = {article},
 year = {2007},
 pages = {539-542},
 volume = {43},
 id = {1a069488-631f-3e37-a3fa-dd46a891b6fe},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {eschweiler2007elektromyo},
 source_type = {article},
 private_publication = {false},
 bibtype = {article},
 author = {Eschweiler, J and Staat, Manfred and van Laack, Walter},
 journal = {Orthopädische Praxis},
 number = {10}
}

@article{
 title = {Limit analysis of flaws in pressurized pipes and cylindrical vessels. Part I: Axial defects},
 type = {article},
 year = {2007},
 keywords = {Axial crack,Global and local collapse,Limit load},
 pages = {431-450},
 volume = {74},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0013794406002062},
 month = {2},
 publisher = {Pergamon},
 id = {ac30286d-7b34-3048-b8ba-905d16b72867},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.260Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat2007limit},
 source_type = {article},
 notes = {No. 14 of the TOP25 list of most read articles in Engineering Fracture Mechanics in October-November 2006},
 private_publication = {false},
 abstract = {Within the theory of plasticity recently developed primal-dual limit analyses with the finite element method (FEM) give upper and lower bounds of the limit load. The method can be iterated until both bounds have converged to the same value which is then considered the exact plastic collapse load. This new numerical method is used in part I of the paper to derive improved lower bound limit load formulae for axial defects in pressurized cylinders for any defect geometry and loading. Based on the observation that even long slits in thick pipes have a residual strength a simple formula for the stress magnification factor is justified also for thick pipes. Global collapse loads are compared with primal-dual FEM limit analyses and with a large number of burst tests. For axial defects it is possible to find corresponding local collapse loads. Part II of the paper will discuss the FEM discretization of the limit load theorems and will consider circumferential defects.},
 bibtype = {article},
 author = {Staat, Manfred and Vu, Duc Khoi},
 doi = {10.1016/j.engfracmech.2006.04.031},
 journal = {Engineering Fracture Mechanics},
 number = {3}
}

Within the theory of plasticity recently developed primal-dual limit analyses with the finite element method (FEM) give upper and lower bounds of the limit load. The method can be iterated until both bounds have converged to the same value which is then considered the exact plastic collapse load. This new numerical method is used in part I of the paper to derive improved lower bound limit load formulae for axial defects in pressurized cylinders for any defect geometry and loading. Based on the observation that even long slits in thick pipes have a residual strength a simple formula for the stress magnification factor is justified also for thick pipes. Global collapse loads are compared with primal-dual FEM limit analyses and with a large number of burst tests. For axial defects it is possible to find corresponding local collapse loads. Part II of the paper will discuss the FEM discretization of the limit load theorems and will consider circumferential defects.

@article{
 title = {Shakedown analysis of structures made of materials with temperature-dependent yield stress},
 type = {article},
 year = {2007},
 keywords = {Convex nonlinear optimization,Shakedown analysis,Temperature-dependent yield stress},
 pages = {4524-4540},
 volume = {44},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0020768306005099},
 month = {6},
 id = {954f838a-2f0c-3f37-9ce9-fbfb0c080ed7},
 created = {2014-06-02T18:44:49.000Z},
 accessed = {2014-06-02},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.352Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Vu2007},
 private_publication = {false},
 abstract = {In this work, the shakedown of structures made of materials with temperature-dependent yield stress is considered. Under some restrictions on the thermal loading condition the yield stress is linearized and shakedown theorems are established. Based on these linearized shakedown theorems, the shakedown limit is formulated as a problem of convex optimization. An algorithm is built to compute shakedown limits. Numerical tests show good agreement with analytic solutions and experimental data. ?? 2006 Elsevier Ltd. All rights reserved.},
 bibtype = {article},
 author = {Vu, Duc Khôi and Staat, Manfred},
 doi = {10.1016/j.ijsolstr.2006.11.038},
 journal = {International Journal of Solids and Structures},
 number = {13}
}

In this work, the shakedown of structures made of materials with temperature-dependent yield stress is considered. Under some restrictions on the thermal loading condition the yield stress is linearized and shakedown theorems are established. Based on these linearized shakedown theorems, the shakedown limit is formulated as a problem of convex optimization. An algorithm is built to compute shakedown limits. Numerical tests show good agreement with analytic solutions and experimental data. ?? 2006 Elsevier Ltd. All rights reserved.

@article{
 title = {Analysis of pressure equipment by application of the primal-dual theory of shakedown},
 type = {article},
 year = {2007},
 keywords = {design by analysis,dua,limit analysis,shakedown},
 pages = {213-225},
 volume = {23},
 websites = {http://doi.wiley.com/10.1002/cnm.891},
 month = {8},
 publisher = {Wiley Online Library},
 day = {14},
 id = {66a7f82a-4aa0-31b8-9cd7-105b525e1d29},
 created = {2018-04-01T19:17:45.942Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T21:44:00.175Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {vu2007analysis},
 source_type = {article},
 private_publication = {false},
 abstract = {The paper describes the application of the primal-dual theory of limit and shakedown analysis in safety assessment and design of pressure components according to the new European approach to design by analysis. Two methods, the static and kinematic one, and their combination, the primal-dual method, are discussed. A numerical example is presented to show the robustness of the primal-dual method compared with two other methods recently used in two European projects on safety assessment and design.},
 bibtype = {article},
 author = {Vu, Duc Khoi and Staat, Manfred and Tran, Ich Thinh},
 doi = {10.1002/cnm.891},
 journal = {Communications in numerical methods in engineering},
 number = {3}
}

The paper describes the application of the primal-dual theory of limit and shakedown analysis in safety assessment and design of pressure components according to the new European approach to design by analysis. Two methods, the static and kinematic one, and their combination, the primal-dual method, are discussed. A numerical example is presented to show the robustness of the primal-dual method compared with two other methods recently used in two European projects on safety assessment and design.

@article{
 title = {Limit loads of circumferentially flawed pipes and cylindrical vessels under internal pressure},
 type = {article},
 year = {2006},
 keywords = {Circumferentially cracked pipe,Global collapse,Limit analysis,Limit load},
 pages = {188-196},
 volume = {83},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0308016106000184},
 month = {3},
 id = {95834fa3-d7e3-3002-9dea-22358c32a77e},
 created = {2014-06-02T18:47:19.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.116Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2006},
 private_publication = {false},
 abstract = {Published limit load formulae for circumferential defects overestimate the burst pressure for penetrating defects in pipes by the factor two in the short crack limit, because they only consider axial stress. Therefore, a class of limit load solution is discussed which takes the triaxial state of stress into account. The solutions for pressure loaded crack faces are improved analytically. Primal–dual limit analysis with the finite element method is used to adjust all solutions to numerical results. Limit loads are obtained for circumferential cracks of all sizes in thick-walled cylinders.},
 bibtype = {article},
 author = {Staat, Manfred and Vu, Duc Khoi},
 doi = {10.1016/j.ijpvp.2006.01.002},
 journal = {International Journal of Pressure Vessels and Piping},
 number = {3}
}

Published limit load formulae for circumferential defects overestimate the burst pressure for penetrating defects in pipes by the factor two in the short crack limit, because they only consider axial stress. Therefore, a class of limit load solution is discussed which takes the triaxial state of stress into account. The solutions for pressure loaded crack faces are improved analytically. Primal–dual limit analysis with the finite element method is used to adjust all solutions to numerical results. Limit loads are obtained for circumferential cracks of all sizes in thick-walled cylinders.

@inproceedings{
 title = {Biomechanical models to evaluate comfort},
 type = {inproceedings},
 year = {2006},
 keywords = {Anybody,multi-body simulation},
 id = {3b8b358b-d55b-31f0-a3bd-471df719b68b},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {rausch2006siebertz},
 source_type = {inproceedings},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Rausch, Jessica and Siebertz, K and Staat, Manfred},
 booktitle = {EUROFORUM-Konferenz “Automobilinnenraum”, München, 15.-16.02. 2006}
}

@article{
 title = {Local and global collapse pressure of longitudinally flawed pipes and cylindrical vessels},
 type = {article},
 year = {2005},
 keywords = {Axially cracked pipe,Global and local collapse,Limit analysis,Pressure loaded crack-face},
 pages = {217-225},
 volume = {82},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0308016104002042},
 month = {3},
 id = {3842d40a-dffb-3d2c-bea8-2f1e48c2c979},
 created = {2014-06-02T18:47:19.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.226Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2005},
 private_publication = {false},
 abstract = {Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. FEM suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to FEM limit analyses for all crack dimensions.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1016/j.ijpvp.2004.07.022},
 journal = {International Journal of Pressure Vessels and Piping},
 number = {3}
}

Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. FEM suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to FEM limit analyses for all crack dimensions.

@article{
 title = {Direct finite element route for design-by-analysis of pressure components},
 type = {article},
 year = {2005},
 keywords = {Alternating plasticity,Design-by-analysis,Progressive plastic deformation,Shakedown analysis,Shakedown criterion},
 pages = {61-67},
 volume = {82},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0308016104001073},
 month = {1},
 id = {f92a6c44-baff-3571-a67f-b6e2f1adf40c},
 created = {2014-06-02T18:47:19.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.271Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2005a},
 private_publication = {false},
 abstract = {In the new European standard for unfired pressure vessels, EN 13445-3, there are two approaches for carrying out a Design-by-Analysis that cover both the stress categorization method (Annex C) and the direct route method (Annex B) for a check against global plastic deformation and against progressive plastic deformation. This paper presents the direct route in the language of limit and shakedown analysis. This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for mechanical and thermal actions. One observation from the examples is that the so-called 3f (3Sm) criterion fails to be a reliable check against progressive plastic deformation. Precise conditions are given, which greatly restrict the applicability of the 3f criterion.},
 bibtype = {article},
 author = {Staat, Manfred and Heitzer, Michael and Lang, H. and Wirtz, Klaus},
 doi = {10.1016/j.ijpvp.2004.04.006},
 journal = {International Journal of Pressure Vessels and Piping},
 number = {1}
}

In the new European standard for unfired pressure vessels, EN 13445-3, there are two approaches for carrying out a Design-by-Analysis that cover both the stress categorization method (Annex C) and the direct route method (Annex B) for a check against global plastic deformation and against progressive plastic deformation. This paper presents the direct route in the language of limit and shakedown analysis. This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for mechanical and thermal actions. One observation from the examples is that the so-called 3f (3Sm) criterion fails to be a reliable check against progressive plastic deformation. Precise conditions are given, which greatly restrict the applicability of the 3f criterion.

@article{
 title = {Plastic collapse analysis of longitudinally flawed pipes and vessels},
 type = {article},
 year = {2004},
 pages = {25-43},
 volume = {234},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0029549304002316},
 month = {12},
 id = {2492bea5-7170-35e5-b5cc-5c5eba7cd9af},
 created = {2014-06-02T18:47:18.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:29:59.959Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Staat2004},
 private_publication = {false},
 abstract = {Improved collapse loads of thick-walled, crack containing pipes and vessels are suggested. Very deep cracks have a residual strength which is better modelled by a global limit load. In all burst tests, the ductility of pressure vessel steels was sufficiently high whereby the burst pressure could be predicted by limit analysis with no need to apply fracture mechanics. The relative prognosis error increases however, for long and deep defects due to uncertainties of geometry and strength data.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1016/j.nucengdes.2004.08.002},
 journal = {Nuclear Engineering and Design},
 number = {1-3}
}

Improved collapse loads of thick-walled, crack containing pipes and vessels are suggested. Very deep cracks have a residual strength which is better modelled by a global limit load. In all burst tests, the ductility of pressure vessel steels was sufficiently high whereby the burst pressure could be predicted by limit analysis with no need to apply fracture mechanics. The relative prognosis error increases however, for long and deep defects due to uncertainties of geometry and strength data.

@article{
 title = {An algorithm for shakedown analysis of structures with temperature dependent yield stress},
 type = {article},
 year = {2004},
 pages = {231-233},
 volume = {4},
 websites = {http://doi.wiley.com/10.1002/pamm.200410097},
 month = {12},
 publisher = {Wiley Online Library},
 id = {7f223e0c-4852-3c1a-a0c4-76d9a8109c88},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2018-12-23T20:41:44.936Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {vu2004algorithm},
 source_type = {article},
 private_publication = {false},
 abstract = {This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature-dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithm for shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools.},
 bibtype = {article},
 author = {Vu, Duc Khoi and Staat, Manfred},
 doi = {10.1002/pamm.200410097},
 journal = {PAMM · Proceedings in Applied Mathematics and Mechanics},
 number = {1}
}

This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature-dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithm for shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools.

@article{
 title = {An interpretation of Wolff’s law},
 type = {article},
 year = {2004},
 pages = {1020-1021},
 volume = {49},
 publisher = {de Gruyter},
 id = {657c35c8-4e3d-35af-8fad-673887eecc73},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-02-19T15:42:27.941Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {kuhn2004},
 source_type = {article},
 private_publication = {false},
 bibtype = {article},
 author = {Kühn, Raoul-Roman and Hauger, Werner and Staat, Manfred and Sponagel, Stepahn},
 journal = {Biomedical Engineering / Biomedizinische Technik},
 number = {Ergänzungsband 2, Teil 2}
}

@article{
 title = {A two phase mixture model based on bone observation},
 type = {article},
 year = {2004},
 pages = {618-619},
 volume = {4},
 websites = {http://doi.wiley.com/10.1002/pamm.200410290},
 month = {12},
 publisher = {Wiley Online Library},
 id = {a0f65d48-9d4c-39d9-996e-0b9641813407},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.122Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {kuhn2004two},
 source_type = {article},
 private_publication = {false},
 abstract = {An optimization method is developed to describe the mechanical behaviour of the human cancellous bone. The method is based on a mixture theory. A careful observation of the behaviour of the bone material leads to the hypothesis that the bone density is controlled by the principal stress trajectories (Wolff's law). The basic idea of the developed method is the coupling of a scalar value via an eigenvalue problem to the principal stress trajectories. On the one hand this theory will permit a prediction of the reaction of the biological bone structure after the},
 bibtype = {article},
 author = {Kühn, Raoul-Roman and Hauger, Werner and Staat, Manfred and Sponagel, Stefan},
 doi = {10.1002/pamm.200410290},
 journal = {PAMM · Proceedings in Applied Mathematics and Mechanics},
 number = {1}
}

An optimization method is developed to describe the mechanical behaviour of the human cancellous bone. The method is based on a mixture theory. A careful observation of the behaviour of the bone material leads to the hypothesis that the bone density is controlled by the principal stress trajectories (Wolff's law). The basic idea of the developed method is the coupling of a scalar value via an eigenvalue problem to the principal stress trajectories. On the one hand this theory will permit a prediction of the reaction of the biological bone structure after the

@article{
 title = {Shakedown and ratchetting under tension–torsion loadings: analysis and experiments},
 type = {article},
 year = {2003},
 pages = {11-26},
 volume = {225},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0029549303001341},
 month = {10},
 id = {0f7865d0-e265-3799-b726-7a5b693cdde2},
 created = {2014-06-02T18:47:19.000Z},
 accessed = {2014-07-28},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:30:00.303Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Heitzer2003},
 private_publication = {false},
 abstract = {Structural design analyses are conducted with the aim of verifying the exclusion of ratchetting. To this end it is important to make a clear distinction between the shakedown range and the ratchetting range. The performed experiment comprised a hollow tension specimen which was subjected to alternating axial forces, superimposed with constant moments. First, a series of uniaxial tests has been carried out in order to calibrate a bounded kinematic hardening rule. The load parameters have been selected on the basis of previous shakedown analyses with the PERMAS code using a kinematic hardening material model. It is shown that this shakedown analysis gives reasonable agreement between the experimental and the numerical results. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis.},
 bibtype = {article},
 author = {Heitzer, Michael and Staat, Manfred and Reiners, H. and Schubert, Florian},
 doi = {10.1016/S0029-5493(03)00134-1},
 journal = {Nuclear Engineering and Design},
 number = {1}
}

Structural design analyses are conducted with the aim of verifying the exclusion of ratchetting. To this end it is important to make a clear distinction between the shakedown range and the ratchetting range. The performed experiment comprised a hollow tension specimen which was subjected to alternating axial forces, superimposed with constant moments. First, a series of uniaxial tests has been carried out in order to calibrate a bounded kinematic hardening rule. The load parameters have been selected on the basis of previous shakedown analyses with the PERMAS code using a kinematic hardening material model. It is shown that this shakedown analysis gives reasonable agreement between the experimental and the numerical results. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis.

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@inproceedings{
 title = {Design by analysis of pressure components by non-linear optimization},
 type = {inproceedings},
 year = {2003},
 keywords = {Design-by_Analysis; limit analysis; shakedown anal},
 pages = {59-65},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2005/93/},
 institution = {ÖGS, Österreichische Gesellschaft für Schweißtechnik, Wien},
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 abstract = {This paper presents the direct route to Design by Analysis (DBA) of the new European pressure vessel standard in the language of limit and shakedown analysis (LISA). This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for some examples from the DBA-Manual. One observation from the examples is, that the optimisation approach gives reliable and close lower bound solutions leading to simple and optimised design decision.},
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 author = {Staat, Manfred and Schwartz, Marcus and Lang, Hermann and Wirtz, Klaus and Heitzer, Michael},
 editor = {Zeman, J L},
 booktitle = {Pressure Vessel Technology 2003. Proceedings ICPVT-10, July 7 10, 2003 Vienna, Austria}
}

This paper presents the direct route to Design by Analysis (DBA) of the new European pressure vessel standard in the language of limit and shakedown analysis (LISA). This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for some examples from the DBA-Manual. One observation from the examples is, that the optimisation approach gives reliable and close lower bound solutions leading to simple and optimised design decision.

@book{
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 abstract = {Foreword: The Commission of the European Communities has supported the LISA project on Limit and Shakedown Analysis for industrial use, which connects direct methods of plasticity with stochastic methods of structural reliability in a general purpose Finite Element package. There was no commercial Finite Element Code that could perform either of this kind of analysis at the time when Professor P.D. Panagiotopoulos and I began the first planning of the LISA project ten years ago. Therefore, we had to answer ourselves three questions: Who may benefit?, Why now?, and Is the idea challenging, can it be realized and will it be successful? The first question was easily answered from observing recent trends in engineering design codes and standards. Instead of the traditional reinterpretation of Finite Element Analyses by stress assessment, modern design codes address structural failure modes directly with the objective to use inelastic deformations of ductile materials for the extension the load carrying capacity. More economic steel structures, pressure vessels and piping can be designed with checks against plastic collapse (gross plastic deformation) and ratchetting (progressive plastic deformation) by Limit and Shakedown Analysis. Optionally, Low Cycle Fatigue (alternating plasticity) may be excluded. Parallel to the LISA project, the new European pressure vessel standard EN 13445-3 has been established with a direct route for design by limit and shakedown analysis. It is a second trend in modern design codes to base partial safety factors on the stochastic concepts of structural reliability analysis. Limit analysis also forms the basis of a number of simplified two-criteria assessment methods in ductile fracture mechanics. Limit and shakedown analysis found applications in a wide range, spanning from soil mechanics to wear in rolling and sliding contact. This answers the second question ’a posteriori’. Although being based on exact theorems of classical plasticity, limit and shakedown analysis are considered as simplified methods. Simplification is achieved without any additional approximation, by restricting analysis to only the failure states of the structure. From an engineering design standpoint, the merit of more elaborate analyses has to be judged in the light of the uncertainty of material data and the difficulties in obtaining suitable constitutive equations. One of the most important results of the simplification is that limit and shakedown analysis makes robust assessments of structural safety. Robustness of a method is its ability to provide acceptable results on the basis of a less than ideal input data. Limit and shakedown analysis states the design problem as a nonlinear optimization problem for the maximum of a safe load or for its dual, the minimum of a failure load. This is a challenging concept, because the number of constraints defining a safe load and a failure load in lower and upper bound analysis, respectively, is huge with Finite Element discretization. Realistic industrial problems are modelled with several 100 thousands of unknowns and constraints today. Different methods for large-scale optimization have been developed by the research groups contributing to the LISA project. The present report includes: basis reduction by plastic analyses and search for the maximum in a sequence of low dimensional subspace by Sequential Quadratic Programming (SQP); dual upper and lower bound analysis of the full size problem by large-scale nonlinear programming methods based on a sequence of linear elastic analyses; reformulation of the problem in the form of a Second Order Cone Programming problem (SOCP). Zarka’s method has been contributed as an additional direct plasticity method, which estimates the plastic deformation prior to failure. Methods which try to go around the difficulties of optimisation are not considered in the LISA project: deviatoric map and methods based on elastic moduli modification such as the Generalized Local Stress Strain (GLOSS) analysis, the elastic compensation method or the linear matching method. The LISA project extends the perfect plasticity models that are used in design code applications. More realistic structural behaviour is modelled by a two-surface plasticity model for bounded kinematic hardening, by the inclusion of moderately large deformations and displacements, and by continuum damage models. Two contributions treat the structural reliability problem for uncertain material data and loading by First and Second Order Reliability Methods (FORM/SORM). These methods become particularly effective with limit and shakedown analysis yielding linear limit state functions. Moreover, the solution of the optimization problem in limit and shakedown analysis generates already the sensitivities needed for the reliability analysis. The extension to chance constraint stochastic programming is indicated. The contributions from the different research groups to this report have been written selfcontained such that they can be read independently. Some effort has been made to use similar notations for the convenience of the reader. Few test problems have been chosen to demonstrate that limit and shakedown analysis combine conceptual insight with the economy of computational effort for a wide range of component geometry and loading conditions.},
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 editor = {Staat, Manfred and Heitzer, Michael}
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Foreword: The Commission of the European Communities has supported the LISA project on Limit and Shakedown Analysis for industrial use, which connects direct methods of plasticity with stochastic methods of structural reliability in a general purpose Finite Element package. There was no commercial Finite Element Code that could perform either of this kind of analysis at the time when Professor P.D. Panagiotopoulos and I began the first planning of the LISA project ten years ago. Therefore, we had to answer ourselves three questions: Who may benefit?, Why now?, and Is the idea challenging, can it be realized and will it be successful? The first question was easily answered from observing recent trends in engineering design codes and standards. Instead of the traditional reinterpretation of Finite Element Analyses by stress assessment, modern design codes address structural failure modes directly with the objective to use inelastic deformations of ductile materials for the extension the load carrying capacity. More economic steel structures, pressure vessels and piping can be designed with checks against plastic collapse (gross plastic deformation) and ratchetting (progressive plastic deformation) by Limit and Shakedown Analysis. Optionally, Low Cycle Fatigue (alternating plasticity) may be excluded. Parallel to the LISA project, the new European pressure vessel standard EN 13445-3 has been established with a direct route for design by limit and shakedown analysis. It is a second trend in modern design codes to base partial safety factors on the stochastic concepts of structural reliability analysis. Limit analysis also forms the basis of a number of simplified two-criteria assessment methods in ductile fracture mechanics. Limit and shakedown analysis found applications in a wide range, spanning from soil mechanics to wear in rolling and sliding contact. This answers the second question ’a posteriori’. Although being based on exact theorems of classical plasticity, limit and shakedown analysis are considered as simplified methods. Simplification is achieved without any additional approximation, by restricting analysis to only the failure states of the structure. From an engineering design standpoint, the merit of more elaborate analyses has to be judged in the light of the uncertainty of material data and the difficulties in obtaining suitable constitutive equations. One of the most important results of the simplification is that limit and shakedown analysis makes robust assessments of structural safety. Robustness of a method is its ability to provide acceptable results on the basis of a less than ideal input data. Limit and shakedown analysis states the design problem as a nonlinear optimization problem for the maximum of a safe load or for its dual, the minimum of a failure load. This is a challenging concept, because the number of constraints defining a safe load and a failure load in lower and upper bound analysis, respectively, is huge with Finite Element discretization. Realistic industrial problems are modelled with several 100 thousands of unknowns and constraints today. Different methods for large-scale optimization have been developed by the research groups contributing to the LISA project. The present report includes: basis reduction by plastic analyses and search for the maximum in a sequence of low dimensional subspace by Sequential Quadratic Programming (SQP); dual upper and lower bound analysis of the full size problem by large-scale nonlinear programming methods based on a sequence of linear elastic analyses; reformulation of the problem in the form of a Second Order Cone Programming problem (SOCP). Zarka’s method has been contributed as an additional direct plasticity method, which estimates the plastic deformation prior to failure. Methods which try to go around the difficulties of optimisation are not considered in the LISA project: deviatoric map and methods based on elastic moduli modification such as the Generalized Local Stress Strain (GLOSS) analysis, the elastic compensation method or the linear matching method. The LISA project extends the perfect plasticity models that are used in design code applications. More realistic structural behaviour is modelled by a two-surface plasticity model for bounded kinematic hardening, by the inclusion of moderately large deformations and displacements, and by continuum damage models. Two contributions treat the structural reliability problem for uncertain material data and loading by First and Second Order Reliability Methods (FORM/SORM). These methods become particularly effective with limit and shakedown analysis yielding linear limit state functions. Moreover, the solution of the optimization problem in limit and shakedown analysis generates already the sensitivities needed for the reliability analysis. The extension to chance constraint stochastic programming is indicated. The contributions from the different research groups to this report have been written selfcontained such that they can be read independently. Some effort has been made to use similar notations for the convenience of the reader. Few test problems have been chosen to demonstrate that limit and shakedown analysis combine conceptual insight with the economy of computational effort for a wide range of component geometry and loading conditions.

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@inproceedings{
 title = {Some achievements of the European project LISA for FEM based limit and shakedown analysis},
 type = {inproceedings},
 year = {2002},
 keywords = {Design,Finite element analysis,Finite element methods,Finite element model,Hardening,Load bearing capacity,Optimization,Plasticity,Pressure,Theorems (Mathematics)},
 pages = {177-185},
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 websites = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1585683},
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 abstract = {The load-carrying capacity or the safety against plastic limit states are central questions in the design of pressure equipment. The new European standard prEN 13445-3 reflects the fact that plastic limit states can be calculated simply by perfectly plastic limit and shakedown analyses. These methods can be derived from static and kinematic theorems for lower and upper bound analysis, respectively. Both may be formulated as optimization problems for finite element discretizations of structures. The problems of large-scale analysis have been solved in an European research project. The methods could be made more realistic by extension to other material models such as a two-surface plasticity model of kinematic hardening. Limit and shakedown analyses are briefly demonstrated with illustrative examples, which are chosen to show some limitations of the 3Sm criterion and the effect of kinematic hardening.},
 bibtype = {inproceedings},
 author = {Staat, Manfred},
 editor = {Badie, undefined},
 doi = {10.1115/PVP2002-1300},
 booktitle = {Computational Mechanics: Developments and Applications}
}

The load-carrying capacity or the safety against plastic limit states are central questions in the design of pressure equipment. The new European standard prEN 13445-3 reflects the fact that plastic limit states can be calculated simply by perfectly plastic limit and shakedown analyses. These methods can be derived from static and kinematic theorems for lower and upper bound analysis, respectively. Both may be formulated as optimization problems for finite element discretizations of structures. The problems of large-scale analysis have been solved in an European research project. The methods could be made more realistic by extension to other material models such as a two-surface plasticity model of kinematic hardening. Limit and shakedown analyses are briefly demonstrated with illustrative examples, which are chosen to show some limitations of the 3Sm criterion and the effect of kinematic hardening.

@inbook{
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 editor = {Marti, Kurt},
 chapter = {Limit and shakedown analysis with uncertain data},
 title = {Stochastic Optimization Techniques, Numerical Methods and Technical Applications}
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The structural reliability with respect to plastic collapse or to inadaptation is formulated on the basis of the lower bound limit and shakedown theorems. A direct definition of the limit state function is achieved. The suggested approach which combines the FE method with first order reliability methods (FORM) leads to a better understanding of the influences on the structural behaviour. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. The limit state function and its gradient are obtained from a mathematical optimization problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error, leading to highly effective and precise reliability analyses.

@inproceedings{
 title = {The restricted influence of kinematic hardening on shakedown loads},
 type = {inproceedings},
 year = {2002},
 keywords = {linear kinematic hardening,material shakedown,nonlinear kinematic hardening,ratcheting,shakedown},
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 abstract = {Structural design analyses are conducted with the aim of verifying the exclusion of ratcheting. To this end it is important to make a clear distinction between the shakedown range and the ratcheting range. In cyclic plasticity more sophisticated hardening models have been suggested in order to model the strain evolution observed in ratcheting experiments. The hardening models used in shakedown analysis are comparatively simple. It is shown that shakedown analysis can make quite stable predictions of admissible load ranges despite the simplicity of the underlying hardening models. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis. Both give identical or similar shakedown ranges. Structural shakedown analyses show that the loading may have a more pronounced effect than the hardening model.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Heitzer, Michael},
 editor = {Mang, H.A. and Rammerstorfer, F.G. and Eberhardsteiner, J},
 doi = {10.21269/62},
 booktitle = {Proceedings of WCCM V, Fifth World Congress on Computational Mechanics, July 7-12, 2002, Vienna, Austria}
}

Structural design analyses are conducted with the aim of verifying the exclusion of ratcheting. To this end it is important to make a clear distinction between the shakedown range and the ratcheting range. In cyclic plasticity more sophisticated hardening models have been suggested in order to model the strain evolution observed in ratcheting experiments. The hardening models used in shakedown analysis are comparatively simple. It is shown that shakedown analysis can make quite stable predictions of admissible load ranges despite the simplicity of the underlying hardening models. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis. Both give identical or similar shakedown ranges. Structural shakedown analyses show that the loading may have a more pronounced effect than the hardening model.

@article{
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@article{
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The load-carrying capacity or the safety against plastic limit states are the central questions in the design of structures and passive components in the apparatus engineering. A precise answer is most simply given by limit and shakedown analysis. These methods can be based on static and kinematic theorems for lower and upper bound analysis. Both may be formulated as optimization problems for finite element discretizations of structures. The problems of large-scale analysis and the extension towards realistic material modelling will be solved in a European research project. Limit and shakedown analyses are briefly demonstrated with illustrative examples.

@article{
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 abstract = {Fatigue analyses are conducted with the aim of verifying that thermal ratcheting is limited. To this end it is important to make a clear distintion between the shakedown range and the ratcheting range (continuing deformation). As part of an EU-supported research project, experiments were carried out using a 4-bar model. The experiment comprised a water-cooled internal tube, and three insulated heatable outer test bars. The system was subjected to alternating axial forces, superimposed with alternating temperatures at the outer bars. The test parameters were partly selected on the basis of previous shakedown analyses. During the test, temperatures and strains were measured as a function of time. The loads and the resulting stresses were confirmed on an ongoing basis during performance of the test, and after it. Different material models were applied for this incremental elasto-plastic analysis using the ANSYS program. The results of the simulation are used to verify the FEM-based shakedown analysis.},
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Fatigue analyses are conducted with the aim of verifying that thermal ratcheting is limited. To this end it is important to make a clear distintion between the shakedown range and the ratcheting range (continuing deformation). As part of an EU-supported research project, experiments were carried out using a 4-bar model. The experiment comprised a water-cooled internal tube, and three insulated heatable outer test bars. The system was subjected to alternating axial forces, superimposed with alternating temperatures at the outer bars. The test parameters were partly selected on the basis of previous shakedown analyses. During the test, temperatures and strains were measured as a function of time. The loads and the resulting stresses were confirmed on an ongoing basis during performance of the test, and after it. Different material models were applied for this incremental elasto-plastic analysis using the ANSYS program. The results of the simulation are used to verify the FEM-based shakedown analysis.

@inproceedings{
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 pages = {24.1. 24.16},
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 abstract = {Traglast- und Einspielanalysen sind vereinfachte doch exakte Verfahren der klassischen Plastizitätstheorie, die neben ausreichender Verformbarkeit keine einschränkenden Voraussetzungen beinhalten. Die Vereinfachungen betreffen die Beschaffung der Daten und Modelle für Details der Lastgeschichte und des Stoffverhaltens. Eine FEM-basierte Traglast- und Einspielanalyse für ideal plastisches Material wurde auf ein kinematisch verfestigendes Materialgesetz erweitert und in das Finite Element Programm PERMAS implementiert. In einem einfachen Zug-Torsionsexperiment wurde eine Hohlprobe mit konstanter Torsion und zyklischer Zugbelastung beansprucht, um die neue Implementierung zu verifizieren. Es konnte gezeigt werden, dass die Einspielanalyse gut mit den experimentellen Ergebnissen übereinstimmt. Bei Verfestigung lassen sich wesentlich größere Sicherheiten nachweisen. Dieses Potential bedarf weiterer experimenteller Absicherung. Parallel dazu ist die Eisnpieltheorie auf fortschrittliche Verfestigungsansätze zu erweitern.},
 bibtype = {inproceedings},
 author = {Heitzer, Michael and Reiners, H and Schubert, Florian and Staat, Manfred},
 editor = {Roos, Eberhard},
 booktitle = {27. MPA-Seminar: Sicherheit und Verfügbarkeit in der Anlagentechnik, Stuttgart, 4.-5. Oktober 2001}
}

Traglast- und Einspielanalysen sind vereinfachte doch exakte Verfahren der klassischen Plastizitätstheorie, die neben ausreichender Verformbarkeit keine einschränkenden Voraussetzungen beinhalten. Die Vereinfachungen betreffen die Beschaffung der Daten und Modelle für Details der Lastgeschichte und des Stoffverhaltens. Eine FEM-basierte Traglast- und Einspielanalyse für ideal plastisches Material wurde auf ein kinematisch verfestigendes Materialgesetz erweitert und in das Finite Element Programm PERMAS implementiert. In einem einfachen Zug-Torsionsexperiment wurde eine Hohlprobe mit konstanter Torsion und zyklischer Zugbelastung beansprucht, um die neue Implementierung zu verifizieren. Es konnte gezeigt werden, dass die Einspielanalyse gut mit den experimentellen Ergebnissen übereinstimmt. Bei Verfestigung lassen sich wesentlich größere Sicherheiten nachweisen. Dieses Potential bedarf weiterer experimenteller Absicherung. Parallel dazu ist die Eisnpieltheorie auf fortschrittliche Verfestigungsansätze zu erweitern.

@inproceedings{
 title = {Kollapsanalyse von längsfehlerbehafteten Rohren und Behältern [Collapse analysis of longitudinally flawed pipes and vessels]},
 type = {inproceedings},
 year = {2001},
 keywords = {axial crack,burst test,limit analysis,plastic c},
 pages = {4.1-4.20},
 volume = {1},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/242/},
 institution = {Staatliche Materialprüfungsanstalt Stuttgart},
 id = {912fa33d-29c7-36b9-90ae-9b9fbec37cbf},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staatkollapsanalyse},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Berstdrücke von 134 Rohren und Behältern mit axialen Oberflächenfehlern mit vier Ingenieurmethoden wurden bei Rißtiefen ab 85% der Wanddicke besonders große Streuungen beobachtet. Die benutzten Formeln stellten im Kern Traglastnäherungen für dünnwandige Rohre dar. Vorversuche mit verschiedenen Temperaturen, Kerbformen und Rissen hatten gezeigt, dass bei allen Oberfllächenrissen Versagen durch vollplastischen Kollaps angenommen werden konnte. Deshalb wurden die Versuche in der Regel vereinfacht mit eingefrästen Kerben durchgeführt. Bruchmechanische Kennwerte lagen i.a. nicht vor. Daher ist eine Bewertung nach der Traglastmethode angemessen und durchführbar. Die genannten Abweichungen konnten nicht alleine auf die statistischen Unsicherheiten in Geometrie und Werkstoffkennwerten zurückgeführt werden. Vielmehr wurde vermutet, dass die benutzten Traglastnäherungen für tiefe Risse ungeeignet sind. Daher wurde der Datensatz um die tiefen Risse reduziert. Bei den verbliebenen 90 Datensätzen konnte mit der besten Traglastnäherung in 40% (60%) der Fälle eine Genauigkeit von ±10% (±20%) erreicht werden. Dieser Beitrag geht davon aus, dass die Werkstoffe in allen Fällen ausreichend duktil waren, so dass plastischer Kollaps vorlag, und stellt daher neue Näherungen für Traglasten vor, die alle Rissabmessungen gleich gut beschreiben: lang, kurz, flach (bis rissfrei) und tief (einschließlich Durchriss). Außerdem werden alle Näherungen für dickwandige Rohre formuliert. Dieser Zielrichtung entsprechend wurde die Datenbasis auf 281 Berstversuche erweitert und schließt jetzt ungerissene und geschlitzte Rohre mit ein.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Szelinski, Ernst and Heitzer, Michael},
 editor = {Roos, Eberhard},
 booktitle = {27. MPA-Seminar: Sicherheit und Verfügbarkeit in der Anlagentechnik, Stuttgart, 4.-5. Oktober 2001}
}

Berstdrücke von 134 Rohren und Behältern mit axialen Oberflächenfehlern mit vier Ingenieurmethoden wurden bei Rißtiefen ab 85% der Wanddicke besonders große Streuungen beobachtet. Die benutzten Formeln stellten im Kern Traglastnäherungen für dünnwandige Rohre dar. Vorversuche mit verschiedenen Temperaturen, Kerbformen und Rissen hatten gezeigt, dass bei allen Oberfllächenrissen Versagen durch vollplastischen Kollaps angenommen werden konnte. Deshalb wurden die Versuche in der Regel vereinfacht mit eingefrästen Kerben durchgeführt. Bruchmechanische Kennwerte lagen i.a. nicht vor. Daher ist eine Bewertung nach der Traglastmethode angemessen und durchführbar. Die genannten Abweichungen konnten nicht alleine auf die statistischen Unsicherheiten in Geometrie und Werkstoffkennwerten zurückgeführt werden. Vielmehr wurde vermutet, dass die benutzten Traglastnäherungen für tiefe Risse ungeeignet sind. Daher wurde der Datensatz um die tiefen Risse reduziert. Bei den verbliebenen 90 Datensätzen konnte mit der besten Traglastnäherung in 40% (60%) der Fälle eine Genauigkeit von ±10% (±20%) erreicht werden. Dieser Beitrag geht davon aus, dass die Werkstoffe in allen Fällen ausreichend duktil waren, so dass plastischer Kollaps vorlag, und stellt daher neue Näherungen für Traglasten vor, die alle Rissabmessungen gleich gut beschreiben: lang, kurz, flach (bis rissfrei) und tief (einschließlich Durchriss). Außerdem werden alle Näherungen für dickwandige Rohre formuliert. Dieser Zielrichtung entsprechend wurde die Datenbasis auf 281 Berstversuche erweitert und schließt jetzt ungerissene und geschlitzte Rohre mit ein.

@inproceedings{
 title = {Traglastanalyse - ein strukturmechanisches Verfahren zur Beurteilung von gerissenen Bauteilen und Verbindungen},
 type = {inproceedings},
 year = {2000},
 keywords = {CT-specimen,frature mechanics,limit analysis,plastic collaps},
 pages = {183-192},
 volume = {232},
 publisher = {Deutscher Verband für Materialforschung und -prüfung},
 city = {Berlin},
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 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {heitzer2000traglastanalyse},
 source_type = {incollection},
 private_publication = {false},
 abstract = {Limit analysis is a structural mechanics method, which determines the load carrying capacity of structures with or without defects. Starting from the exact limit Ioad theory in plasticity a combined tool of Finite Element Method (FEM) and mathematical programming is developped. The comparison of numerical and known experimental results shows, that limit analyses can predict the load carrying capacity of ductile structures with defects nearly exactly.},
 bibtype = {inproceedings},
 author = {Heitzer, Michael and Staat, Manfred},
 editor = {Richard, H. A.},
 booktitle = {32. Tagung des DVM-Arbeitskreises Bruchvorgänge, 22. und 23. Februar 2000 in Berlin: Themenschwerpunkt: Festigkeits- und Bruchverhalten von Fügeverbindungen / Obmann des Arbeitskreises: H. A. Richard / Deutscher Verband für Materialforschung und -prüfung}
}

Limit analysis is a structural mechanics method, which determines the load carrying capacity of structures with or without defects. Starting from the exact limit Ioad theory in plasticity a combined tool of Finite Element Method (FEM) and mathematical programming is developped. The comparison of numerical and known experimental results shows, that limit analyses can predict the load carrying capacity of ductile structures with defects nearly exactly.

@inproceedings{
 title = {Direct FEM limit and shakedown analysis with uncertain data},
 type = {inproceedings},
 year = {2000},
 keywords = {FORM,limit analysis,reliabili,skaedown analysis},
 pages = {1-13},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2006/112/},
 id = {d4fb9e0d-cec3-3eb4-9e21-ad25341f614d},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
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 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {heitzer2000direct},
 source_type = {inproceedings},
 notes = {paper 483},
 private_publication = {false},
 abstract = {The structural reliability with respect to plastic collapse or to inadaptation is formulated on the basis of the lower bound limit and shakedown theorems. A direct definition of the limit state function is achieved which permits the use of the highly effective first order reliability methods (FORM) is achieved. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. The limit state function and its gradient are obtained from a mathematical optimization problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error, leading to highly effective and precise reliability analyses.},
 bibtype = {inproceedings},
 author = {Heitzer, Michael and Staat, Manfred},
 editor = {Oñate, E and Bugeda, G and Suarez, B},
 booktitle = {CD-ROM Proceedings of the European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS 2000, Barcelona, Spain, 11-14 September 2000}
}

The structural reliability with respect to plastic collapse or to inadaptation is formulated on the basis of the lower bound limit and shakedown theorems. A direct definition of the limit state function is achieved which permits the use of the highly effective first order reliability methods (FORM) is achieved. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. The limit state function and its gradient are obtained from a mathematical optimization problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error, leading to highly effective and precise reliability analyses.

@inproceedings{
 title = {Direct FEM approach to design-by-analysis of pressurized components},
 type = {inproceedings},
 year = {2000},
 pages = {79-81},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/239/},
 publisher = {Achema. Ausstellungstagung für chemisches Apparatewesen},
 city = {Frankfurt/Main},
 institution = {Achema},
 id = {20c13de2-5423-3cfd-a761-61d95d40c283},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-02-22T07:54:39.290Z},
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 starred = {false},
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 confirmed = {true},
 hidden = {false},
 citation_key = {heitzerdirect},
 source_type = {inproceedings},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Heitzer, Michael and Staat, Manfred},
 doi = {10.21269/200},
 booktitle = {ACHEMA 2000, Lecture groups Safety Technology, Equipment and Plant Engineering, Multiproduct Plants, Packaging/Tank Cleaning}
}

@inbook{
 type = {inbook},
 year = {2000},
 pages = {269-288},
 volume = {83},
 websites = {http://www.springerlink.com/index/10.1007/978-94-010-9421-4_17},
 publisher = {Springer Netherlands},
 city = {Dordrecht},
 series = {Solid Mechanics and Its Applications},
 id = {f060d277-92ba-3e7d-a63d-d26e14d43222},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-09-16},
 file_attached = {false},
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 last_modified = {2019-05-22T20:30:03.930Z},
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 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {heitzer2001reliability},
 source_type = {incollection},
 private_publication = {false},
 abstract = {Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. The paper discusses some difficulties of different reliability methods for FEM-discretized nonlinear structures. It is proposed that theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behaviour under time variant loading. The limit state function and its gradient is obtained from a mathematical optimization problem. For application to large FEM models a basis reduction method is used. The method is implemented into a general purpose FEM code. Combined with FORM highly effective, robust and precise analyses could be performed for high-reliabilty problems.},
 bibtype = {inbook},
 author = {Heitzer, Michael and Staat, Manfred},
 editor = {Weichert, Dieter and Maier, Giulio},
 doi = {10.1007/978-94-010-9421-4_17},
 chapter = {Reliability analysis of elasto-plastic structures under variable loads},
 title = {Inelastic Analysis of Structures under Variable Loads: Theory and Engineering Applications}
}

Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. The paper discusses some difficulties of different reliability methods for FEM-discretized nonlinear structures. It is proposed that theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behaviour under time variant loading. The limit state function and its gradient is obtained from a mathematical optimization problem. For application to large FEM models a basis reduction method is used. The method is implemented into a general purpose FEM code. Combined with FORM highly effective, robust and precise analyses could be performed for high-reliabilty problems.

@book{
 title = {Limit analysis of defects},
 type = {book},
 year = {2000},
 pages = {XII, 1-84},
 volume = {Jül-3746},
 websites = {http://hdl.handle.net/2128/20601,http://juser.fz-juelich.de/record/54193},
 publisher = {Research Centre Jülich},
 city = {Jülich, Germany},
 series = {Bericht des Forschungszentrums Jülich},
 id = {e4d1fb1a-e643-39ee-a6fb-62060b0d0186},
 created = {2014-06-02T20:07:49.000Z},
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 last_modified = {2020-03-12T22:09:35.483Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat2000defect},
 source_type = {book},
 private_publication = {false},
 abstract = {The present report introduces the use of numerical limit analysis in ductile fracture mechanics. Limit analysis is a structural mechanics method, which finds increasing application in engineering fracture mechanics. Emphasis is put on possible improvements in the integrity assessment of crack containing components which may be achieved by combining the approach with the Finite Element Method (FEM). Several applications and examples for numerical and experimental validations are presented. This report describes the LISA developments in connection with current practice of defect assessment and material testing. The Brite-EuRam III project LISA: FEM-Based Limit and Shakedown Analysis for Design and Integrity Assessment in European Industry is planned to extend and generalize the numerical methods of the so-called direct approach for the assessment of maximum load carrying capacity due to monotonic and cyclic loading (limit and shakedown load). Die Traglastanalyse ist eine strukturmechanische Methode, welche zunehmend in bruchmechanischen Bewertungskonzepten angewandt wird. Dieser Bericht gibt eine Einführung in die numerische Traglastanalyse in der Bruchmechanik duktiler Werkstoffe. Durch die Verbindung dieser Theorie mit Finite-Element Methoden (FEM) können Verbesserungen in der Bewertung rißbehafteter Bauteile erreicht werden. Zahlreiche Anwendungen und Beispiele zur numerischen und experimentellen Validierung werden vorgestellt. Dieser Bericht beschreibt die neuen Konzepte, die im LISA-Projekt im Rahmen der bruchmechanischen Bewertung erzielt wurden. Das Brite-EuRam III Projekt LISA: FEM-Based Limit and Shakedown Analysis for Design and Integrity Assessment in European Industry zielt auf die Erweiterung und Verallgemeinerung sogenannter direkter numerischer Methoden zur Berechnung von maximal tragbaren monotonen und zyklischen Belastungen (Trag- und Einspiellasten).},
 bibtype = {book},
 author = {Staat, Manfred and Heitzer, Michael and Ai-Min, Yan and Khoi, Vu Duc and Hung, Nguyen Dang and Voldoire, François and Lahousse, A}
}

The present report introduces the use of numerical limit analysis in ductile fracture mechanics. Limit analysis is a structural mechanics method, which finds increasing application in engineering fracture mechanics. Emphasis is put on possible improvements in the integrity assessment of crack containing components which may be achieved by combining the approach with the Finite Element Method (FEM). Several applications and examples for numerical and experimental validations are presented. This report describes the LISA developments in connection with current practice of defect assessment and material testing. The Brite-EuRam III project LISA: FEM-Based Limit and Shakedown Analysis for Design and Integrity Assessment in European Industry is planned to extend and generalize the numerical methods of the so-called direct approach for the assessment of maximum load carrying capacity due to monotonic and cyclic loading (limit and shakedown load). Die Traglastanalyse ist eine strukturmechanische Methode, welche zunehmend in bruchmechanischen Bewertungskonzepten angewandt wird. Dieser Bericht gibt eine Einführung in die numerische Traglastanalyse in der Bruchmechanik duktiler Werkstoffe. Durch die Verbindung dieser Theorie mit Finite-Element Methoden (FEM) können Verbesserungen in der Bewertung rißbehafteter Bauteile erreicht werden. Zahlreiche Anwendungen und Beispiele zur numerischen und experimentellen Validierung werden vorgestellt. Dieser Bericht beschreibt die neuen Konzepte, die im LISA-Projekt im Rahmen der bruchmechanischen Bewertung erzielt wurden. Das Brite-EuRam III Projekt LISA: FEM-Based Limit and Shakedown Analysis for Design and Integrity Assessment in European Industry zielt auf die Erweiterung und Verallgemeinerung sogenannter direkter numerischer Methoden zur Berechnung von maximal tragbaren monotonen und zyklischen Belastungen (Trag- und Einspiellasten).

@article{
 title = {Basis reduction for the shakedown problem for bounded kinematic hardening material},
 type = {article},
 year = {2000},
 keywords = {Basis reduction,Convex optimization,FEM,Shakedown analysis,basis reduction,convex optimization,fem,shakedown analysis},
 pages = {185-200},
 volume = {17},
 websites = {http://link.springer.com/article/10.1023/A:1008321026063,http://link.springer.com/10.1023/A:1008321026063},
 id = {6c3b75be-af53-3d7e-af05-8aa3a737bda5},
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 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Heitzer2000},
 private_publication = {false},
 abstract = {Limit and shakedown analysis are effective methods for assessing the load carrying ca- pacity of a given structure. The elasto–plastic behavior of the structure subjected to loads varying in a given load domain is characterized by the shakedown load factor, defined as the maximum factor which satisfies the sufficient conditions stated in the corresponding static shakedown theorem. The finite element dicretization of the problem may lead to very large convex optimization. For the effective solution a basis reduction method has been developed thatmakes use of the special problem structure for perfectly plastic material. The paper proposes a modified basis reduction method for direct application to the two-surface plasticity model of bounded kinematic hardening material. The considered numerical examples show an enlargement of the load carrying capacity due to bounded hardening.},
 bibtype = {article},
 author = {Heitzer, Michael and Pop, Gabriela and Staat, Manfred},
 doi = {10.1023/A:1008321026063},
 journal = {Journal of Global Optimization},
 number = {1/4}
}

Limit and shakedown analysis are effective methods for assessing the load carrying ca- pacity of a given structure. The elasto–plastic behavior of the structure subjected to loads varying in a given load domain is characterized by the shakedown load factor, defined as the maximum factor which satisfies the sufficient conditions stated in the corresponding static shakedown theorem. The finite element dicretization of the problem may lead to very large convex optimization. For the effective solution a basis reduction method has been developed thatmakes use of the special problem structure for perfectly plastic material. The paper proposes a modified basis reduction method for direct application to the two-surface plasticity model of bounded kinematic hardening material. The considered numerical examples show an enlargement of the load carrying capacity due to bounded hardening.

@article{
 title = {FEM-computation of load carrying capacity of highly loaded passive components by direct methods},
 type = {article},
 year = {1999},
 pages = {349-358},
 volume = {193},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/S0029549399001909},
 month = {10},
 publisher = {Elsevier Sequoia SA},
 id = {547dce97-34a2-3884-baa8-30b04302c933},
 created = {2014-06-02T18:47:20.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:29:59.870Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Heitzer1999},
 private_publication = {false},
 abstract = {Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of safety factors or of the load carrying capacity under constant and varying loads. Simple versions of limit and shakedown analysis are the basis of all design codes for pressure vessels and pipings. Using finite element methods (FEM), more realistic modeling can be used for a more rational design. The methods can be extended towards optimum plastic design. In this paper, we present a first implementation of limit and shakedown analyses for perfectly plastic material into a general purpose FEM program. Limit and shakedown loads are obtained for a square plate with a hole and for a thin tube. Interaction diagrams are calculated and the results are compared with known analytic solutions.},
 bibtype = {article},
 author = {Heitzer, Michael and Staat, Manfred},
 doi = {10.1016/S0029-5493(99)00190-9},
 journal = {Nuclear Engineering and Design},
 number = {3}
}

Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of safety factors or of the load carrying capacity under constant and varying loads. Simple versions of limit and shakedown analysis are the basis of all design codes for pressure vessels and pipings. Using finite element methods (FEM), more realistic modeling can be used for a more rational design. The methods can be extended towards optimum plastic design. In this paper, we present a first implementation of limit and shakedown analyses for perfectly plastic material into a general purpose FEM program. Limit and shakedown loads are obtained for a square plate with a hole and for a thin tube. Interaction diagrams are calculated and the results are compared with known analytic solutions.

@inproceedings{
 title = {Zyklische Einspielversuche zur Verifikation von Shakedown-Analysen mittels FEM [Cyclic plastic deformation test to verify FEM-based shakedown analysis]},
 type = {inproceedings},
 year = {1999},
 keywords = {ratcheting,thermal cyclic loading},
 pages = {44.1-44.18},
 volume = {2},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/245/},
 institution = {Staatliche Materialprüfungsanstalt Universität Stuttgart},
 id = {34640459-0bf3-30ec-b7cb-f6d2335553c0},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2017-03-14T23:34:32.861Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {langzyklische},
 source_type = {inproceedings},
 private_publication = {false},
 abstract = {Im Rahmen von Ermüdungsanalysen ist nachzuweisen, daß die thermisch bedingten fortschreitenden Deformationen begrenzt bleiben. Hierzu ist die Abgrenzung des Shakedown-Bereiches (Einspielen) vom Ratchetting-Bereich (fortschreitende Deformation) von Interesse. Im Rahmen eines EU-geförderten Forschungsvorhabens wurden Experimente mit einem 4-Stab-Modell durchgeführt. Das Experiment bestand aus einem wassergekühlten inneren Rohr und drei isolierten und beheizbaren äußeren Probestäben. Das System wurde durch alternierende Axialkräfte, denen alternierende Temperaturen an den äußeren Stäben überlagert wurden, belastet. Die Versuchsparameter wurden teilweise nach vorausgegangenen Einspielanalysen gewählt. Während der Versuchsdurchführung wurden Temperaturen und Dehnungen zeitabhängig gemessen. Begleitend und nachfolgend zur Versuchsdurchführung wurden die Belastungen und die daraus resultierenden Beanspruchungen nachvollzogen. Bei dieser inkrementellen elasto-plastischen Analyse mit dem Programm ANSYS wurden unterschiedliche Werkstoffmodelle angesetzt. Die Ergebnisse dieser Simulationsberechnung dienen dazu, die Shakedown-Analysen mittels FE-Methode zu verifizieren.},
 bibtype = {inproceedings},
 author = {Lang, H and Wirtz, Klaus and Heitzer, Michael and Staat, Manfred},
 editor = {K, Kussmaul},
 booktitle = {25. MPA-Seminar: Sicherheit und Verfügbarkeit in der Anlagentechnik mit dem Schwerpunkt Sicherheit und Zuverlässigkeit - Integritätsnachweise, Komponentenqualifikation, Schadensverhütung, Stuttgart, 6.-7. Oktober 1999}
}

Im Rahmen von Ermüdungsanalysen ist nachzuweisen, daß die thermisch bedingten fortschreitenden Deformationen begrenzt bleiben. Hierzu ist die Abgrenzung des Shakedown-Bereiches (Einspielen) vom Ratchetting-Bereich (fortschreitende Deformation) von Interesse. Im Rahmen eines EU-geförderten Forschungsvorhabens wurden Experimente mit einem 4-Stab-Modell durchgeführt. Das Experiment bestand aus einem wassergekühlten inneren Rohr und drei isolierten und beheizbaren äußeren Probestäben. Das System wurde durch alternierende Axialkräfte, denen alternierende Temperaturen an den äußeren Stäben überlagert wurden, belastet. Die Versuchsparameter wurden teilweise nach vorausgegangenen Einspielanalysen gewählt. Während der Versuchsdurchführung wurden Temperaturen und Dehnungen zeitabhängig gemessen. Begleitend und nachfolgend zur Versuchsdurchführung wurden die Belastungen und die daraus resultierenden Beanspruchungen nachvollzogen. Bei dieser inkrementellen elasto-plastischen Analyse mit dem Programm ANSYS wurden unterschiedliche Werkstoffmodelle angesetzt. Die Ergebnisse dieser Simulationsberechnung dienen dazu, die Shakedown-Analysen mittels FE-Methode zu verifizieren.

@inproceedings{
 title = {Structural reliability analysis of elasto-plastic structures},
 type = {inproceedings},
 year = {1999},
 keywords = {F,limit analysis,reliability,shakedown analysis},
 pages = {513-518},
 publisher = {AA Balkema, Rotterdam, Brookfield},
 id = {5150821c-fbae-39d1-ab5f-f66636edf16f},
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 abstract = {Limit and shakedown therorems are exact theories of classical plasticity for the direct computation of the load carrying capacity of structures under constant and varying loads. The theorems may be used for a direct definiton of the limit state function for failure by plastic collapse or by indaptation. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. Then the limit state function is obtained from a mathematical optimization problem. This direct approach reduces cosnsiderably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error. Moreover, the direct way leads to highly effective and precise reliability analyses.},
 bibtype = {inproceedings},
 author = {Heitzer, Michael and Staat, Manfred},
 editor = {Schuëller, G I and Kafka, P},
 booktitle = {Safety and Reliability}
}

Limit and shakedown therorems are exact theories of classical plasticity for the direct computation of the load carrying capacity of structures under constant and varying loads. The theorems may be used for a direct definiton of the limit state function for failure by plastic collapse or by indaptation. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. Then the limit state function is obtained from a mathematical optimization problem. This direct approach reduces cosnsiderably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error. Moreover, the direct way leads to highly effective and precise reliability analyses.

@inproceedings{
 title = {Reliability assessment of passive safety systems},
 type = {inproceedings},
 year = {1998},
 pages = {1-14},
 websites = {http://hdl.handle.net/10840/3114},
 publisher = {ASME, New York, N.Y.},
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 abstract = {Innovative reactor concepts make use of passive safety features to a large extent in combination with active safety or operational systems. Following the IAEA definitions a passive component does not need external input (especially energy) to operate. This is why it is expected that passive systems combine among others the advantages of simplicity, reduction of the need for human interaction, reduction or avoidance of external electrical power or signals. Besides the open feedback on economic competitiveness special aspects like lack of data on some phenomena, missing operating experience over the wide range of conditions and the smaller driving forces as - in most cases - compared to active safety systems must be taken into account. Both for active and passive systems, the effective reliability versus the achievement of safety functions is considered as an essential criteria for judging the real potential of the systems. Generally speaking, the reliability assessment of passive safety functions defined as the probability to fail the requested mission to achieve a generic safety function, depends, more than for active systems, on environment, physical, nuclear or chemical phenomena. This remark is entirely applicable to the passive B systems (i.e. implementing moving working fluids, cf. IAEA). Their mission is defined through a nominal requested time dependent evolution, for a set of selected and representative parameters and an allowable range is allocated around the nominal evolution. It is stated that the mission fails when the plant parameters are outside the allowable range. As a first approach, it is considered that the reliability assessment of passive safety functions can be estimated evaluating the probability for having the mission failure. This assessment is achieved comparing the distribution of the expected parameters values to the allowable range. This implies the identification and quantification of the uncertainties in the prediction of physical phenomena performances or interdependencies. In parallel, an adequate effort must be devoted to the improvement of thermalhydraulic computer codes that model the passive safety system behaviour to integrate those uncertainties. Finally, the transfer of the structural methodology assessment methodology (i.e. for passive A systems) must be checked to verify its applicability for the thermalhydraulic passive systems, too. The paper is focused particularly on passive B safety functions and related systems and illustrates a possible methodology for their reliability assessment. The example explained in the report can be used as a preliminary basis to motivate and to organise the content of a work that could be conducted within the framework of the European Commission sponsored activities on Reliability Methods for Passive Safety Functions.},
 bibtype = {inproceedings},
 author = {Burgazzi, L and Fiorini, G L and De Magistris, F and Von Lensa, Werner and Staat, Manfred and Altes, Jürgen},
 booktitle = {Proc. of the 6th Internat. Conf. on Nuclear Engineering, San Diego, Calif., May 10-15, 1998, ICONE 6-6340}
}

Innovative reactor concepts make use of passive safety features to a large extent in combination with active safety or operational systems. Following the IAEA definitions a passive component does not need external input (especially energy) to operate. This is why it is expected that passive systems combine among others the advantages of simplicity, reduction of the need for human interaction, reduction or avoidance of external electrical power or signals. Besides the open feedback on economic competitiveness special aspects like lack of data on some phenomena, missing operating experience over the wide range of conditions and the smaller driving forces as - in most cases - compared to active safety systems must be taken into account. Both for active and passive systems, the effective reliability versus the achievement of safety functions is considered as an essential criteria for judging the real potential of the systems. Generally speaking, the reliability assessment of passive safety functions defined as the probability to fail the requested mission to achieve a generic safety function, depends, more than for active systems, on environment, physical, nuclear or chemical phenomena. This remark is entirely applicable to the passive B systems (i.e. implementing moving working fluids, cf. IAEA). Their mission is defined through a nominal requested time dependent evolution, for a set of selected and representative parameters and an allowable range is allocated around the nominal evolution. It is stated that the mission fails when the plant parameters are outside the allowable range. As a first approach, it is considered that the reliability assessment of passive safety functions can be estimated evaluating the probability for having the mission failure. This assessment is achieved comparing the distribution of the expected parameters values to the allowable range. This implies the identification and quantification of the uncertainties in the prediction of physical phenomena performances or interdependencies. In parallel, an adequate effort must be devoted to the improvement of thermalhydraulic computer codes that model the passive safety system behaviour to integrate those uncertainties. Finally, the transfer of the structural methodology assessment methodology (i.e. for passive A systems) must be checked to verify its applicability for the thermalhydraulic passive systems, too. The paper is focused particularly on passive B safety functions and related systems and illustrates a possible methodology for their reliability assessment. The example explained in the report can be used as a preliminary basis to motivate and to organise the content of a work that could be conducted within the framework of the European Commission sponsored activities on Reliability Methods for Passive Safety Functions.

@inproceedings{
 title = {LISA, ein europäisches Projekt zur direkten Berechnung der Tragfähigkeit duktiler Strukturen},
 type = {inproceedings},
 year = {1998},
 keywords = {limit analysi,shakedown analysis},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/240/},
 publisher = {INTES GmbH, Stuttgrt},
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 abstract = {Auslegung und Bemessung von Komponenten und Bauwerken erfolgen im Maschinenwesen und Konstruktiven Ingenieurbau überwiegend mit dem Ziel eines Spannungsnachweises unterhalb der Streckgrenze. Im Apparatebau wird die plastische Auslegung nach Regelwerk weitgehend aus der elastischen Spannungsanalyse durch Extrapolation experimenteller und analytischer Ergebnisse im Sinne der Traglast- und Einspieltheorie gewonnen. Deshalb bilden linear elastische Rechnungen heute noch den überwiegenden Teil der Finite Elemente Anwendungen. Begünstigt durch die schnelle Rechnerentwicklung gewinnen aber zunehmend inelastische Analysen des plastischen (zeitunabhängigen) oder viskosen (zeitabhängigen) Verhaltens an Bedeutung. Das Ziel ist die kostengünstige Entwicklung betriebs- und sicherheitsoptimierter Strukturen. Inkrementelle elasto-plastische Analysen des Strukturverhaltens lösen die mit der Spannungsbewertung verbundenen Probleme nur teilweise. Daneben sind sie mit einem nicht immer zu rechtfertigenden hohen Aufwand an Rechnerzeit, Personaleinsatz und Daten-Beschaffungskosten verbunden. Mit der Traglast- und Einspielanalyse bietet sich eine Methode an, die eine Spannungsbewertung umgeht und deren Aufwand eher einer elastischen Rechnungen entspricht. Im Regelwerk ist das Traglastkonzept für Balkenbiegung seit 1947 in Großbritannien und seit 1959 in den U.S.A. akzeptiert. Es ist in den neuen Eurocodes enthalten und findet Anwendung in der Zähbruchmechanik. Trag- und Einspiellast bilden in der einen oder anderen Weise die Grundlage der Auslegungskonzepte aller Regelwerke für Druckbehälter und Rohrleitungen.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Heitzer, Michael and Hicken, Enno F},
 booktitle = {PERMAS–Benutzertagung, 8.-9.10.1998, Stuttgart}
}

Auslegung und Bemessung von Komponenten und Bauwerken erfolgen im Maschinenwesen und Konstruktiven Ingenieurbau überwiegend mit dem Ziel eines Spannungsnachweises unterhalb der Streckgrenze. Im Apparatebau wird die plastische Auslegung nach Regelwerk weitgehend aus der elastischen Spannungsanalyse durch Extrapolation experimenteller und analytischer Ergebnisse im Sinne der Traglast- und Einspieltheorie gewonnen. Deshalb bilden linear elastische Rechnungen heute noch den überwiegenden Teil der Finite Elemente Anwendungen. Begünstigt durch die schnelle Rechnerentwicklung gewinnen aber zunehmend inelastische Analysen des plastischen (zeitunabhängigen) oder viskosen (zeitabhängigen) Verhaltens an Bedeutung. Das Ziel ist die kostengünstige Entwicklung betriebs- und sicherheitsoptimierter Strukturen. Inkrementelle elasto-plastische Analysen des Strukturverhaltens lösen die mit der Spannungsbewertung verbundenen Probleme nur teilweise. Daneben sind sie mit einem nicht immer zu rechtfertigenden hohen Aufwand an Rechnerzeit, Personaleinsatz und Daten-Beschaffungskosten verbunden. Mit der Traglast- und Einspielanalyse bietet sich eine Methode an, die eine Spannungsbewertung umgeht und deren Aufwand eher einer elastischen Rechnungen entspricht. Im Regelwerk ist das Traglastkonzept für Balkenbiegung seit 1947 in Großbritannien und seit 1959 in den U.S.A. akzeptiert. Es ist in den neuen Eurocodes enthalten und findet Anwendung in der Zähbruchmechanik. Trag- und Einspiellast bilden in der einen oder anderen Weise die Grundlage der Auslegungskonzepte aller Regelwerke für Druckbehälter und Rohrleitungen.

@inproceedings{
 title = {Reliability methods for passive safety function},
 type = {inproceedings},
 year = {1997},
 keywords = {reliabilty},
 websites = {http://hdl.handle.net/10840/3114},
 institution = {International & American Associations for Structural Mechanics in Reactor Technology},
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 author = {Fiorini, G L and Staat, Manfred and von Lensa, Werner and Burgazzi, L},
 booktitle = {Proceedings of Post SMiRT 14, Seminar 18 Passive Safety Features in Nuclear Installations, Pisa, August 25-27, 1997}
}

@inproceedings{
 title = {Limit and shakedown analysis for plastic safety of complex structures},
 type = {inproceedings},
 year = {1997},
 pages = {33-40},
 volume = {B},
 websites = {https://repository.lib.ncsu.edu/handle/1840.20/31910},
 institution = {International & American Associations for Structural Mechanics in Reactor Technology},
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 abstract = {Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of the load carrying capacity under constant and varying loads. They are implemented in a general purpose FEM program in a way capable of large-scale analysis. The method deviates from the current approach in several aspects: No load history is used, stresses and strains are not calculated, and the safety factor is obtained from a mathematical optimization problem. This reduces considerably the necessary technological input data, the computing time, and the numerical error.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Heitzer, Michael},
 editor = {Livolant, M},
 booktitle = {Transactions of the 14th International Conference on Structural Dynamics in Reactor Technology (SMiRT-14), Lyon, France, August 17-22, 1997}
}

Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of the load carrying capacity under constant and varying loads. They are implemented in a general purpose FEM program in a way capable of large-scale analysis. The method deviates from the current approach in several aspects: No load history is used, stresses and strains are not calculated, and the safety factor is obtained from a mathematical optimization problem. This reduces considerably the necessary technological input data, the computing time, and the numerical error.

@inproceedings{
 title = {Limit and shakedown analysis using a general purpose finite element code},
 type = {inproceedings},
 year = {1997},
 pages = {522-533},
 volume = {97},
 month = {4},
 publisher = {Bell&Bain Ltd Glasgow},
 institution = {NAFEMS National Agency for Finite Element Methods and Standards},
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}

@inproceedings{
 title = {Limit and shakedown analysis for plastic design},
 type = {inproceedings},
 year = {1997},
 keywords = {limit analysis,shakedown analysis},
 pages = {4.3.1-4.3.19},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/244/},
 month = {9},
 publisher = {Staatliche Materialprüfungsanstalt, Stuttgart},
 city = {Stuttgart},
 institution = {Staatliche Materialpüfungsanstalt Universität Stuttgart},
 id = {d06b2338-e9e9-3d2b-a873-81ae1fa32018},
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 abstract = {Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of safety factors or of the load carrying capacity under constant and varying loads. Simple versions of limit and shakedown analysis are the basis of all design codes for pressure vessels and pipings. Using Finite Element Methods more realistic modeling can be used for a more rational design. The methods can be extended to yield optimum plastic design. In this paper we present a first implementation in FE of limit and shakedown analyses for perfectly plastic material. Limit and shakedown analyses are done of a pipe–junction and a interaction diagram is calculated. The results are in good correspondence with the analytic solution we give in the appendix.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Heitzer, Michael},
 editor = {Kussmaul, Karl},
 booktitle = {Proceedings of 7th German-Japanese Joint Seminar on Research in Structural Strength and NDE-Problems in Nuclear Engineering}
}

Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of safety factors or of the load carrying capacity under constant and varying loads. Simple versions of limit and shakedown analysis are the basis of all design codes for pressure vessels and pipings. Using Finite Element Methods more realistic modeling can be used for a more rational design. The methods can be extended to yield optimum plastic design. In this paper we present a first implementation in FE of limit and shakedown analyses for perfectly plastic material. Limit and shakedown analyses are done of a pipe–junction and a interaction diagram is calculated. The results are in good correspondence with the analytic solution we give in the appendix.

@inproceedings{
 title = {Direkte FEM-Berechnung der Tragfähigkeit hochbeanspruchter passiver Komponenten [Direct FEM-computation of load carrying capacity of highly loaded passive components]},
 type = {inproceedings},
 year = {1997},
 keywords = {FEM-computation,limit analysis,load carrying capacity,shakedown analysis},
 pages = {29.1-29.19},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2008/243/},
 publisher = {Materialprüfungsanstalt Universität Stuttgart},
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 private_publication = {false},
 abstract = {Genaue Kenntnis der Spannungen und Verformungen in passiven Komponenten gewinnt man mit detailierten inelastischen FEM Analysen. Die lokale Beanspruchung läßt sich aber nicht direkt mit einer Beanspruchbarkeit im strukturmechanischen Sinne vergleichen. Konzentriert man sich auf die Frage nach der Tragfähigkeit, dann vereinfacht sich die Analyse. Im Rahmen der Plastizitätstheorie berechnen Traglast- und Einspielanalyse die tragbaren Lasten direkt und exakt. In diesem Beitrag wird eine Implementierung der Traglast- und Einspielsätze in ein allgemeines FEM Programm vorgestellt, mit der die Tragfähigkeit passiver Komponenten direkt berechnet wird. Die benutzten Konzepte werden in Bezug auf die übliche Strukturanalyse erläutert. Beispiele mit lokal hoher Beanspruchung verdeutlichen die Anwendung der FEM basierten Traglast- und Einspielanalysen. Die berechneten Interaktionsdiagramme geben einen guten Überblick über die möglichen Betriebsbereiche passiver Komponenten. Die Traglastanalyse bietet auch einen strukturmechanischen Zugang zur Kollapslast rißbehafteter Komponenten aus hochzähem Material.},
 bibtype = {inproceedings},
 author = {Staat, Manfred and Heitzer, Michael},
 editor = {Kussmaul, Karl},
 doi = {10.21269/202},
 booktitle = {23. MPA-Seminar: Sicherheit und Verfügbarkeit in der Anlagentechnik mit dem Schwerpunkt Verhalten von druckführenden Komponenten und Systemen bei erhöhten Belastungen, Stuttgart, 1 und. 2. Oktober 1997}
}

Genaue Kenntnis der Spannungen und Verformungen in passiven Komponenten gewinnt man mit detailierten inelastischen FEM Analysen. Die lokale Beanspruchung läßt sich aber nicht direkt mit einer Beanspruchbarkeit im strukturmechanischen Sinne vergleichen. Konzentriert man sich auf die Frage nach der Tragfähigkeit, dann vereinfacht sich die Analyse. Im Rahmen der Plastizitätstheorie berechnen Traglast- und Einspielanalyse die tragbaren Lasten direkt und exakt. In diesem Beitrag wird eine Implementierung der Traglast- und Einspielsätze in ein allgemeines FEM Programm vorgestellt, mit der die Tragfähigkeit passiver Komponenten direkt berechnet wird. Die benutzten Konzepte werden in Bezug auf die übliche Strukturanalyse erläutert. Beispiele mit lokal hoher Beanspruchung verdeutlichen die Anwendung der FEM basierten Traglast- und Einspielanalysen. Die berechneten Interaktionsdiagramme geben einen guten Überblick über die möglichen Betriebsbereiche passiver Komponenten. Die Traglastanalyse bietet auch einen strukturmechanischen Zugang zur Kollapslast rißbehafteter Komponenten aus hochzähem Material.

@article{
 title = {Probabilistic assessment of the fracture mechanics behaviour of an HTR-module primary circuit pressure boundary},
 type = {article},
 year = {1996},
 pages = {221-236},
 volume = {160},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/0029549395011056},
 month = {2},
 id = {8b433f6b-b6d2-31be-8bbb-e4382cf4178f},
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 abstract = {In this paper the fracture mechanical behaviour of the primary circuit pressure boundary of a planned HTR-module reactor for electricity and steam generation under normal operation is assessed probabilistically. First and second order reliability methods (FORM-SORM) are used to calculate failure probabilities. They also allow a simplified analysis of the leak-before-break (LBB) behaviour. No LBB was probabilistically identified for the reactor pressure vessel. However, failure of the pressure vessel unit in normal operation probably originates from the connecting pressure vessel or the steam generator pressure vessel. They show LBB in probabilistic terms.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1016/0029-5493(95)01105-6},
 journal = {Nuclear Engineering and Design},
 number = {1-2}
}

In this paper the fracture mechanical behaviour of the primary circuit pressure boundary of a planned HTR-module reactor for electricity and steam generation under normal operation is assessed probabilistically. First and second order reliability methods (FORM-SORM) are used to calculate failure probabilities. They also allow a simplified analysis of the leak-before-break (LBB) behaviour. No LBB was probabilistically identified for the reactor pressure vessel. However, failure of the pressure vessel unit in normal operation probably originates from the connecting pressure vessel or the steam generator pressure vessel. They show LBB in probabilistic terms.

@inproceedings{
 title = {Problems and chances for probabilistic fracture mechanics in the analysis of steel pressure boundary reliability},
 type = {inproceedings},
 year = {1996},
 keywords = {leak-before-brea,probabilistic fracture mechanics},
 pages = {43-55},
 volume = {IAEA-TECDO},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2006/189/,https://www-pub.iaea.org/MTCD/Publications/PDF/te_920_web.pdf,http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/28/021/28021623.pdf},
 publisher = {International Atomic Energy Agency, Vienna},
 city = {Vienna},
 institution = {IAEA, Vienna},
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 citation_key = {staat1996problems},
 source_type = {inproceedings},
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 abstract = {It is shown that the difficulty for probabilistic fracture mechanics (PFM) is the general problem of the high reliability of a small population. There is no way around the problem as yet. Therefore what PFM can contribute to the reliability of steel pressure boundaries is demon­strated with the example of a typical reactor pressure vessel and critically discussed. Although no method is distinguishable that could give exact failure probabilities, PFM has several addi­tional chances. Upper limits for failure probability may be obtained together with trends for design and operating conditions. Further, PFM can identify the most sensitive parameters, improved control of which would increase reliability. Thus PFM should play a vital role in the analysis of steel pressure boundaries despite all shortcomings.},
 bibtype = {inproceedings},
 author = {Staat, Manfred},
 booktitle = {Technical feasibility and reliability of passive safety systems for nuclear power plants. Proceedings of an Advisory Group Meeting held in Jülich, 21-24 November 1994}
}

It is shown that the difficulty for probabilistic fracture mechanics (PFM) is the general problem of the high reliability of a small population. There is no way around the problem as yet. Therefore what PFM can contribute to the reliability of steel pressure boundaries is demon­strated with the example of a typical reactor pressure vessel and critically discussed. Although no method is distinguishable that could give exact failure probabilities, PFM has several addi­tional chances. Upper limits for failure probability may be obtained together with trends for design and operating conditions. Further, PFM can identify the most sensitive parameters, improved control of which would increase reliability. Thus PFM should play a vital role in the analysis of steel pressure boundaries despite all shortcomings.

@article{
 title = {Reliability of an HTR-module primary circuit pressure boundary Influences, sensitivity, and comparison with a PWR},
 type = {article},
 year = {1995},
 pages = {333-340},
 volume = {158},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/002954939501040O},
 month = {9},
 publisher = {North-Holland},
 id = {0907b825-94fd-30e4-b222-5db2b221fb5d},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-08-18},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
 last_modified = {2020-03-12T22:25:34.953Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat1995reliability},
 source_type = {article},
 private_publication = {false},
 abstract = {The reliability of the HTR-module for electricity and steam generation was analysed for normal operation, as well as accident conditions. The probabilistic fracture mechanics assessment was performed with a modification of the zerberus code on the basis of widely used data. The calculated failure probabilities may thus be compared with similar investigations. The HTR-module primary circuit pressure boundary as a unit showed leak-before-break behaviour in a probabilistic sense, although a break was more probable than a leak for some of its parts. However, the findings may depend greatly on the stochastic data. Therefore a stochastic reference problem is defined and the results are compared with the Japanese round robin on a PWR section. Possible changes of failure probabilities and of the leak-before-break behaviour are discussed for different criteria for the events leading to a leak, and for modifications of the stochastic reference problem such as the inclusion of NDE. The results may be used to identify those stochastic variables which have the greatest influence on the computed failure probabilities, and to perhaps justify further work which would provide more detailed information on these probabilities. Furthermore, there is an obvious need for reduction of the non-statistical reasons for great variations of failure probabilities.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1016/0029-5493(95)01040-O},
 journal = {Nuclear Engineering and Design},
 number = {2-3}
}

The reliability of the HTR-module for electricity and steam generation was analysed for normal operation, as well as accident conditions. The probabilistic fracture mechanics assessment was performed with a modification of the zerberus code on the basis of widely used data. The calculated failure probabilities may thus be compared with similar investigations. The HTR-module primary circuit pressure boundary as a unit showed leak-before-break behaviour in a probabilistic sense, although a break was more probable than a leak for some of its parts. However, the findings may depend greatly on the stochastic data. Therefore a stochastic reference problem is defined and the results are compared with the Japanese round robin on a PWR section. Possible changes of failure probabilities and of the leak-before-break behaviour are discussed for different criteria for the events leading to a leak, and for modifications of the stochastic reference problem such as the inclusion of NDE. The results may be used to identify those stochastic variables which have the greatest influence on the computed failure probabilities, and to perhaps justify further work which would provide more detailed information on these probabilities. Furthermore, there is an obvious need for reduction of the non-statistical reasons for great variations of failure probabilities.

@inproceedings{
 title = {Reliability of the primary circuit pressure boundary of an HTR-module under accident conditions},
 type = {inproceedings},
 year = {1993},
 pages = {331-342},
 publisher = {Balkema, Elsevier, Amsterdam},
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 author = {Staat, Manfred},
 editor = {Kafka, Peter and Wolf, Josefa},
 booktitle = {Safety and Reliability Assessment. An Integral Approach, ESREL '93,, München, 10 - 12 May 1993}
}

@article{
 title = {Failure probabilities of the primary circuit pressure boundary of an HTR-Module for process heat generation under accident conditions for different failure modes},
 type = {article},
 year = {1993},
 pages = {53-67},
 volume = {144},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/002954939390008W},
 month = {10},
 publisher = {North-Holland},
 id = {30fc457a-8d41-3d77-b96a-c295d4c902e9},
 created = {2014-06-02T20:07:49.000Z},
 file_attached = {false},
 profile_id = {93ec0d5b-403c-3f87-b702-40b6362f05e6},
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 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {staat1993failure},
 source_type = {article},
 private_publication = {false},
 abstract = {In this paper different failure modes of the primary circuit pressure boundary of a planned HTR-Module reactor for process heat generation under accident conditions with loss of all heat sinks are assessed probabilistically. It is shown why failure probabilities cannot be expected to represent absolute values but nevertheles, as relative values they permit an effective comparison of components and failure modes. Failure probabilities are calculated under the condition that the postulated accident has actually occurred. They are compared for various cross sections and different failure modes. The failure of the crack-free base material of the forgings as well as the Leak-Before-Break behaviour of the welds is considered. The conditional failure probabilities are to be multiplied with the cumulative frequency, still to be determined, of all event sequences leading to the accident in question to give its contribution to the total failure frequency. This contribution is low.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1016/0029-5493(93)90008-W},
 journal = {Nuclear Engineering and Design},
 number = {1}
}

In this paper different failure modes of the primary circuit pressure boundary of a planned HTR-Module reactor for process heat generation under accident conditions with loss of all heat sinks are assessed probabilistically. It is shown why failure probabilities cannot be expected to represent absolute values but nevertheles, as relative values they permit an effective comparison of components and failure modes. Failure probabilities are calculated under the condition that the postulated accident has actually occurred. They are compared for various cross sections and different failure modes. The failure of the crack-free base material of the forgings as well as the Leak-Before-Break behaviour of the welds is considered. The conditional failure probabilities are to be multiplied with the cumulative frequency, still to be determined, of all event sequences leading to the accident in question to give its contribution to the total failure frequency. This contribution is low.

@inproceedings{
 title = {Sensitivity of and influences on the reliability of an HTR-module primary circuit pressure boundary},
 type = {inproceedings},
 year = {1993},
 keywords = {leak-before-break,probabilistic fracture mechanics},
 pages = {147-152},
 volume = {M},
 issue = {1},
 websites = {http://www.iasmirt.org/transactions/12/MG10-2,http://www.lib.ncsu.edu/resolver/1840.20/24499},
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 notes = {<b>From Duplicate 3 ( <i>Sensitivity of and influences on the reliability of an HTR-module primary circuit pressure boundary</i> - Staat, M )<br/></b><br/>paper MG10/2},
 private_publication = {false},
 abstract = {In this paper different failure modes of the primary circuit pressure boundary of a planned HTR-Module reactor for process heat generation under accident conditions with loss of all heat sinks are assessed probabilistically. It is shown why failure probabilities cannot be expected to represent absolute values but nevertheles, as relative values they permit an effective comparison of components and failure modes. Failure probabilities are calculated under the condition that the postulated accident has actually occurred. They are compared for various cross sections and different failure modes. The failure of the crack-free base material of the forgings as well as the Leak-Before-Break behaviour of the welds is considered. The conditional failure probabilities are to be multiplied with the cumulative frequency, still to be determined, of all event sequences leading to the accident in question to give its contribution to the total failure frequency. This contribution is low.},
 bibtype = {inproceedings},
 author = {Staat, Manfred},
 editor = {Kussmaul, Karl},
 booktitle = {Transactions of the 12th International Conference on Structural Dynamics in Reactor Technology (SMiRT-12), Stuttgart, Germany, August 15-20, 1993}
}

In this paper different failure modes of the primary circuit pressure boundary of a planned HTR-Module reactor for process heat generation under accident conditions with loss of all heat sinks are assessed probabilistically. It is shown why failure probabilities cannot be expected to represent absolute values but nevertheles, as relative values they permit an effective comparison of components and failure modes. Failure probabilities are calculated under the condition that the postulated accident has actually occurred. They are compared for various cross sections and different failure modes. The failure of the crack-free base material of the forgings as well as the Leak-Before-Break behaviour of the welds is considered. The conditional failure probabilities are to be multiplied with the cumulative frequency, still to be determined, of all event sequences leading to the accident in question to give its contribution to the total failure frequency. This contribution is low.

@inproceedings{
 title = {Probabilistische Bewertung des bruchmechanischen Verhaltens der Primärkreisdruckumschließung eines HTR-Moduls [Probabilistic Assessment of the Fracture Mechanical Behaviour of an HTR-Module Primary Circuit Pressure Boundary]},
 type = {inproceedings},
 year = {1992},
 keywords = {ratcheting,thermal cyclic loading},
 pages = {27.1-27.18},
 volume = {1},
 institution = {Staatliche Materialprüfungsanstalt Universität Stuttgart},
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 citation_key = {staat18mpa},
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 abstract = {Im Rahmen von Ermüdungsanalysen ist nachzuweisen, daß die thermisch bedingten fortschreitenden Deformationen begrenzt bleiben. Hierzu ist die Abgrenzung des Shakedown-Bereiches (Einspielen) vom Ratchetting-Bereich (fortschreitende Deformation) von Interesse. Im Rahmen eines EU-geförderten Forschungsvorhabens wurden Experimente mit einem 4-Stab-Modell durchgeführt. Das Experiment bestand aus einem wassergekühlten inneren Rohr und drei isolierten und beheizbaren äußeren Probestäben. Das System wurde durch alternierende Axialkräfte, denen alternierende Temperaturen an den äußeren Stäben überlagert wurden, belastet. Die Versuchsparameter wurden teilweise nach vorausgegangenen Einspielanalysen gewählt. Während der Versuchsdurchführung wurden Temperaturen und Dehnungen zeitabhängig gemessen. Begleitend und nachfolgend zur Versuchsdurchführung wurden die Belastungen und die daraus resultierenden Beanspruchungen nachvollzogen. Bei dieser inkrementellen elasto-plastischen Analyse mit dem Programm ANSYS wurden unterschiedliche Werkstoffmodelle angesetzt. Die Ergebnisse dieser Simulationsberechnung dienen dazu, die Shakedown-Analysen mittels FE-Methode zu verifizieren.},
 bibtype = {inproceedings},
 author = {Staat, Manfred},
 editor = {Kussmaul, K},
 booktitle = {18. MPA-Seminar: Sicherheit und Verfügbarkeit in der Anlagentechnik mit dem Schwerpunkt Sicherheit und Zuverlässigkeit - Integritätsnachweise, Komponentenqualifikation, Schadensverhütung, Stuttgart, 8.-9. Oktober 1992}
}

Im Rahmen von Ermüdungsanalysen ist nachzuweisen, daß die thermisch bedingten fortschreitenden Deformationen begrenzt bleiben. Hierzu ist die Abgrenzung des Shakedown-Bereiches (Einspielen) vom Ratchetting-Bereich (fortschreitende Deformation) von Interesse. Im Rahmen eines EU-geförderten Forschungsvorhabens wurden Experimente mit einem 4-Stab-Modell durchgeführt. Das Experiment bestand aus einem wassergekühlten inneren Rohr und drei isolierten und beheizbaren äußeren Probestäben. Das System wurde durch alternierende Axialkräfte, denen alternierende Temperaturen an den äußeren Stäben überlagert wurden, belastet. Die Versuchsparameter wurden teilweise nach vorausgegangenen Einspielanalysen gewählt. Während der Versuchsdurchführung wurden Temperaturen und Dehnungen zeitabhängig gemessen. Begleitend und nachfolgend zur Versuchsdurchführung wurden die Belastungen und die daraus resultierenden Beanspruchungen nachvollzogen. Bei dieser inkrementellen elasto-plastischen Analyse mit dem Programm ANSYS wurden unterschiedliche Werkstoffmodelle angesetzt. Die Ergebnisse dieser Simulationsberechnung dienen dazu, die Shakedown-Analysen mittels FE-Methode zu verifizieren.

@inproceedings{
 title = {Versagenswahrscheinlichkeit der Primärkreisdruckumschließung eines HTR-Moduls zur Prozeßwärmegewinnung unter Störfallbedingungen},
 type = {inproceedings},
 year = {1991},
 keywords = {ratcheting,thermal cyclic loading},
 pages = {123-126},
 publisher = {INFORUM, Bonn},
 city = {Bonn, Germany},
 id = {691c532e-39b8-3a4c-a10e-3bc7581bead0},
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 booktitle = {Jahrestagung Kerntechnik ’91. INFORUM, Mai 14-16, 1991, Bonn, Germany}
}

@inproceedings{
 title = {Versagenswahrscheinlichkeit der Primärkreisdruckumschließung eines HTR-Moduls zur Prozeßwärmegewinnung unter Störfallbedingungen bei verschiedenen Versagensmoden [Failure probabilities of the pressure boundary of the primary circuit of a HTR-module for pr},
 type = {inproceedings},
 year = {1991},
 keywords = {ratcheting,thermal cyclic loading},
 pages = {22.1-22.20},
 volume = {1},
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 abstract = {Im Rahmen von Ermüdungsanalysen ist nachzuweisen, daß die thermisch bedingten fortschreitenden Deformationen begrenzt bleiben. Hierzu ist die Abgrenzung des Shakedown-Bereiches (Einspielen) vom Ratchetting-Bereich (fortschreitende Deformation) von Interesse. Im Rahmen eines EU-geförderten Forschungsvorhabens wurden Experimente mit einem 4-Stab-Modell durchgeführt. Das Experiment bestand aus einem wassergekühlten inneren Rohr und drei isolierten und beheizbaren äußeren Probestäben. Das System wurde durch alternierende Axialkräfte, denen alternierende Temperaturen an den äußeren Stäben überlagert wurden, belastet. Die Versuchsparameter wurden teilweise nach vorausgegangenen Einspielanalysen gewählt. Während der Versuchsdurchführung wurden Temperaturen und Dehnungen zeitabhängig gemessen. Begleitend und nachfolgend zur Versuchsdurchführung wurden die Belastungen und die daraus resultierenden Beanspruchungen nachvollzogen. Bei dieser inkrementellen elasto-plastischen Analyse mit dem Programm ANSYS wurden unterschiedliche Werkstoffmodelle angesetzt. Die Ergebnisse dieser Simulationsberechnung dienen dazu, die Shakedown-Analysen mittels FE-Methode zu verifizieren.},
 bibtype = {inproceedings},
 author = {Staat, Manfred},
 editor = {Kussmaul, K},
 booktitle = {17. MPA-Seminar: Sicherheit und Verfügbarkeit in der Anlagentechnik mit dem Schwerpunkt Sicherheit und Zuverlässigkeit - Integritätsnachweise, Komponentenqualifikation, Schadensverhütung, Stuttgart, 10.-11. Oktober 1991}
}

Im Rahmen von Ermüdungsanalysen ist nachzuweisen, daß die thermisch bedingten fortschreitenden Deformationen begrenzt bleiben. Hierzu ist die Abgrenzung des Shakedown-Bereiches (Einspielen) vom Ratchetting-Bereich (fortschreitende Deformation) von Interesse. Im Rahmen eines EU-geförderten Forschungsvorhabens wurden Experimente mit einem 4-Stab-Modell durchgeführt. Das Experiment bestand aus einem wassergekühlten inneren Rohr und drei isolierten und beheizbaren äußeren Probestäben. Das System wurde durch alternierende Axialkräfte, denen alternierende Temperaturen an den äußeren Stäben überlagert wurden, belastet. Die Versuchsparameter wurden teilweise nach vorausgegangenen Einspielanalysen gewählt. Während der Versuchsdurchführung wurden Temperaturen und Dehnungen zeitabhängig gemessen. Begleitend und nachfolgend zur Versuchsdurchführung wurden die Belastungen und die daraus resultierenden Beanspruchungen nachvollzogen. Bei dieser inkrementellen elasto-plastischen Analyse mit dem Programm ANSYS wurden unterschiedliche Werkstoffmodelle angesetzt. Die Ergebnisse dieser Simulationsberechnung dienen dazu, die Shakedown-Analysen mittels FE-Methode zu verifizieren.

@inproceedings{
 title = {Überarbeitete probabilistisch orientierte Sicherheitsanalyse für den HTR-Modul},
 type = {inproceedings},
 year = {1990},
 pages = {143-146},
 volume = {1},
 publisher = {INFORUM, Bonn},
 city = {Nürnberg},
 id = {7b88b6ff-7160-3c91-b25e-677ed34d3f0d},
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 author = {Wolters, J and Bongarts, R and Hennings, W and Jahn, Wilfried and Marx, J and Staat, Manfred and Verfondern, Karl},
 booktitle = {Jahrestagung Kerntechnik ’90. INFORUM, Mai 15-17, 1990, Nürnberg, Germany}
}

@article{
 title = {Zur Problematik tensorieller Verallgemeinerungen einachsiger nichtlinearer Materialgesetze},
 type = {article},
 year = {1989},
 pages = {73-81},
 volume = {69},
 websites = {http://doi.wiley.com/10.1002/zamm.19890690209},
 publisher = {WILEY-VCH Verlag (Akademie Verlag GmbH)},
 id = {bcb37a3a-0f62-3092-a0f7-da87ade578d4},
 created = {2014-06-02T20:07:49.000Z},
 accessed = {2014-06-02},
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 source_type = {article},
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 abstract = {Durch Angabe von Gegenbeispielen wird gezeigt, daß es alleine aus der Kenntnis eines einachsigen Versuches nicht allgemein möglich ist, eindimensionale Stoffgesetze mehrdimensional zu verallgemeinern; insbesondere stößt man bei der nichtlinearen Erweiterung klassischer Moduln auf Widersprüche. Die in der Argumentation ergänzend benutzten dualen Materialgesetze ermöglichen wesentliche Vereinfachungen. Die zur vollständigen Identifikation der Stoffwerte benötigten Experimente werden besprochen. It is shown by counterexamples that it is generally impossible to derive tensor constitutive equations from empirical scalar approximations of a single uniaxial experiment. Especially, the use of generalized classical moduli leads to inconsistencies. Some examples are given, which show that the use of a dual constitutive equation allows considerable simplifications. The experiments necessary for a complete identification of material parameters are discussed. При помощи противоречащих примеров доназывается невозможность выведения тензорных уравнений консистенции из эмпирических скалярных приближений одиночного эксперимента. Особенно применение обобщенных нлассических модулей водит к несовместимостям. Даются некоторые примеры показывающие, что применение двойственного уравнения консистенций позволяет значительные упрощения. Обсуждаются эксперыменты нужны для полной идентификации параметров материала.},
 bibtype = {article},
 author = {Staat, Manfred and Ballmann, Josef},
 doi = {10.1002/zamm.19890690209},
 journal = {ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik},
 number = {2}
}

Durch Angabe von Gegenbeispielen wird gezeigt, daß es alleine aus der Kenntnis eines einachsigen Versuches nicht allgemein möglich ist, eindimensionale Stoffgesetze mehrdimensional zu verallgemeinern; insbesondere stößt man bei der nichtlinearen Erweiterung klassischer Moduln auf Widersprüche. Die in der Argumentation ergänzend benutzten dualen Materialgesetze ermöglichen wesentliche Vereinfachungen. Die zur vollständigen Identifikation der Stoffwerte benötigten Experimente werden besprochen. It is shown by counterexamples that it is generally impossible to derive tensor constitutive equations from empirical scalar approximations of a single uniaxial experiment. Especially, the use of generalized classical moduli leads to inconsistencies. Some examples are given, which show that the use of a dual constitutive equation allows considerable simplifications. The experiments necessary for a complete identification of material parameters are discussed. При помощи противоречащих примеров доназывается невозможность выведения тензорных уравнений консистенции из эмпирических скалярных приближений одиночного эксперимента. Особенно применение обобщенных нлассических модулей водит к несовместимостям. Даются некоторые примеры показывающие, что применение двойственного уравнения консистенций позволяет значительные упрощения. Обсуждаются эксперыменты нужны для полной идентификации параметров материала.

@inbook{
 type = {inbook},
 year = {1989},
 keywords = {Hamiltonian,Hayes-Thomas formula,Monge cones,acceleration waves,method of characteristics},
 pages = {574-588},
 volume = {24},
 websites = {http://opus.bibliothek.fh-aachen.de/opus/volltexte/2007/206/,http://www.springerlink.com/index/10.1007/978-3-322-87869-4,http://link.springer.com/10.1007/978-3-322-87869-4_56},
 publisher = {Vieweg+Teubner Verlag},
 city = {Wiesbaden},
 series = {Notes on Numerical Fluid Mechanics},
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 authored = {true},
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 citation_key = {staat1989fundamental},
 source_type = {incollection},
 private_publication = {false},
 abstract = {The nonlinear scalar constitutive equations of gases lead to a change in sound speed from point to point as would be found in linear inhomogeneous (and time dependent) media. The nonlinear tensor constitutive equations of solids introduce the additional local effect of solution dependent anisotropy. The speed of a wave passing through a point changes with propagation direction and its rays are inclined to the front. It is an open question whether the widely used operator splitting techniques achieve a dimensional splitting with physically reasonable results for these multi-dimensional problems. Maybe this is the main reason why the theoretical and numerical investigations of multi-dimensional wave propagation in nonlinear solids are so far behind gas dynamics. We hope to promote the subject a little by a discussion of some fundamental aspects of the solution of the equations of nonlinear elastodynamics. We use methods of characteristics because they only integrate mathematically exact equations which have a direct physical interpretation.},
 bibtype = {inbook},
 author = {Staat, Manfred and Ballmann, Josef},
 editor = {Ballmann, Josef and Jeltsch, Rolf},
 doi = {10.1007/978-3-322-87869-4_56},
 chapter = {Fundamental aspects of numerical methods for the propagation of multi-dimensional nonlinear waves in solids},
 title = {Nonlinear Hyperbolic Equations — Theory, Computation Methods, and Applications}
}

The nonlinear scalar constitutive equations of gases lead to a change in sound speed from point to point as would be found in linear inhomogeneous (and time dependent) media. The nonlinear tensor constitutive equations of solids introduce the additional local effect of solution dependent anisotropy. The speed of a wave passing through a point changes with propagation direction and its rays are inclined to the front. It is an open question whether the widely used operator splitting techniques achieve a dimensional splitting with physically reasonable results for these multi-dimensional problems. Maybe this is the main reason why the theoretical and numerical investigations of multi-dimensional wave propagation in nonlinear solids are so far behind gas dynamics. We hope to promote the subject a little by a discussion of some fundamental aspects of the solution of the equations of nonlinear elastodynamics. We use methods of characteristics because they only integrate mathematically exact equations which have a direct physical interpretation.

@inbook{
 type = {inbook},
 year = {1989},
 pages = {73-81},
 websites = {https://www.degruyter.com/document/doi/10.1515/9783112553169-006/html},
 month = {12},
 publisher = {De Gruyter},
 day = {31},
 city = {Berlin, Boston},
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 citation_key = {Staat1989},
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 abstract = {Durch Angabe von Gegenbeispielen wird gezeigt, daß es alleine aus der Kenntnis eines einachsigen Versuches nicht allgemein möglich ist, eindimensionale Stoffgesetze mehrdimensional zu verallgemeinern; insbesondere stößt man bei der nichtlinearen Erweiterung klassischer Moduln auf Widersprüche. Die in der Argumentation ergänzend benutzten dualen Materialgesetze ermöglichen wesentliche Vereinfachungen. Die zur vollständigen Identifikation der Stoffwerte benötigten Experimente werden besprochen. It is shown by counterexamples that it is generally impossible to derive tensor constitutive equations from empirical scalar approximations of a single uniaxial experiment. Especially, the use of generalized classical moduli leads to inconsistencies. Some examples are given, which show that the use of a dual constitutive equation allows considerable simplifications. The experiments necessary for a complete identification of material parameters are discussed. При помощи противоречащих примеров доназывается невозможность выведения тензорных уравнений консистенции из эмпирических скалярных приближений одиночного эксперимента. Особенно применение обобщенных нлассических модулей водит к несовместимостям. Даются некоторые примеры показывающие, что рименение двойственного уравнения консистенций позволяет значительные упрощения. Обсуждаются эксперыменты нужны для полной идентификации параметров материала.},
 bibtype = {inbook},
 author = {Staat, Manfred and Ballmann, Josef},
 editor = {Heinrich, H. and Schmid, G.},
 doi = {10.1515/9783112553169-006},
 chapter = {Zur Problematik tensorieller Verallgemeinerungen einachsiger nichtlinearer Materialgesetze},
 title = {Zeitschrift für Angewandte Mathematik und Mechanik Volume 69, Heft 2}
}

Durch Angabe von Gegenbeispielen wird gezeigt, daß es alleine aus der Kenntnis eines einachsigen Versuches nicht allgemein möglich ist, eindimensionale Stoffgesetze mehrdimensional zu verallgemeinern; insbesondere stößt man bei der nichtlinearen Erweiterung klassischer Moduln auf Widersprüche. Die in der Argumentation ergänzend benutzten dualen Materialgesetze ermöglichen wesentliche Vereinfachungen. Die zur vollständigen Identifikation der Stoffwerte benötigten Experimente werden besprochen. It is shown by counterexamples that it is generally impossible to derive tensor constitutive equations from empirical scalar approximations of a single uniaxial experiment. Especially, the use of generalized classical moduli leads to inconsistencies. Some examples are given, which show that the use of a dual constitutive equation allows considerable simplifications. The experiments necessary for a complete identification of material parameters are discussed. При помощи противоречащих примеров доназывается невозможность выведения тензорных уравнений консистенции из эмпирических скалярных приближений одиночного эксперимента. Особенно применение обобщенных нлассических модулей водит к несовместимостям. Даются некоторые примеры показывающие, что рименение двойственного уравнения консистенций позволяет значительные упрощения. Обсуждаются эксперыменты нужны для полной идентификации параметров материала.

@inbook{
 type = {inbook},
 year = {1988},
 keywords = {Methods of Characteristics,P waves,Rayleigh waves,accerlaration waves,von Schmidt waves},
 pages = {1719-1722},
 volume = {2},
 websites = {http://link.springer.com/10.1007/978-3-642-61381-4_452},
 publisher = {Springer Berlin Heidelberg},
 city = {Berlin, Heidelberg},
 chapter = {Computation of impacts on elastic solids by methods of bicharacteristics},
 id = {9abd571f-9db4-3445-acf1-b7ed69b4f8f7},
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 abstract = {Shock waves, explosions, impacts or cavitation bubble collapses may generate stress waves in solids causing cracks or unexpected damage due to focussing, physical nonlinearity or interaction with existing cracks. There is a growing interest in wave propagation, which poses many novel problems to experimentalists and theorists. Wave propagation is mostly governed by hyperbolic PDEs. Numerical methods applicable to strong waves in solids, which are as powerful as the FEM e.g. applied to static or quasi-static problems, have not yet been evolved for multi­ dimensional problems. All state of the art methods for hyperbolic problems are based on the solution of the local wave propagation. They differ in the construction of the fundamental solution and thus in the treatment of singularities connected with any sharp wave front such as acceleration waves and shocks. For application to solids, the methods of bicharacteristics seem to be especially well suited, since fundamental solutions can be constructed in a straight forward way for various constitutive equations.},
 bibtype = {inbook},
 author = {Ballmann, Josef and Staat, Manfred},
 editor = {Atluri, S N and Yagawa, G},
 doi = {10.1007/978-3-642-61381-4_452},
 title = {Computational Mechanics ’88}
}

Shock waves, explosions, impacts or cavitation bubble collapses may generate stress waves in solids causing cracks or unexpected damage due to focussing, physical nonlinearity or interaction with existing cracks. There is a growing interest in wave propagation, which poses many novel problems to experimentalists and theorists. Wave propagation is mostly governed by hyperbolic PDEs. Numerical methods applicable to strong waves in solids, which are as powerful as the FEM e.g. applied to static or quasi-static problems, have not yet been evolved for multi­ dimensional problems. All state of the art methods for hyperbolic problems are based on the solution of the local wave propagation. They differ in the construction of the fundamental solution and thus in the treatment of singularities connected with any sharp wave front such as acceleration waves and shocks. For application to solids, the methods of bicharacteristics seem to be especially well suited, since fundamental solutions can be constructed in a straight forward way for various constitutive equations.

@inproceedings{
 title = {Wave propagation and focussing in plates},
 type = {inproceedings},
 year = {1988},
 keywords = {Rayleigh waves,acceleration waves,von Schmidt waves},
 pages = {949-956},
 volume = {2},
 publisher = {Deutsche Gesellschaft für Metallkunde Informationsgesellschaft, Oberursel},
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 abstract = {A method of bicharacteristics for the computation of stress waves in linear elastic plates with straight boundaries was first devised by CLIFTON on the basis of a proposal for gas dynamics. Also starting from gas dynamics we applied this method to plates with curved boundaries and plate structures including shear and bending. Of major interest was the computation of stress concentrations as a result of the focussing of waves that were reflected from concave boundaries, as well as from internal boundaries. We compared our numerical results with experiments that were carried out in the Shock Waves Laboratory of Aachen Technical University. Good correlations were observed which we wish to further improve upon by means of a higher order plate theory. Currently we have developed methods of characteristics for non-elastic and nonlinear materials. In regard to non-elastic materials, we have previously considered linear elastic-viscoplastic laws such as the PERZYNA model, as well as the BODNER-PARTOM model. They lead to semi-linear hyperbolic laws, i.e. the highest derivatives appear only linearly. In the case of nonlinear materials with large deformations and physical nonlinearity, we have considered isotropic elastic media. If homogeneously prestressed they show anisotropic wave propagation, resembling the observations made in linear transversely isotropic elastic media. Also in plasticity very similar effects of anisotropic wave propagation are expected, if e.g. PRANDTL-REUSS-like laws are used. Generally the strain induced anisotropy changes from point to point according to the local deformation. Attempts have been made to use this anisotropic effect in the non destructive evaluation of residual stresses with ultrasonics. A numerical method of bicharacteristics for the computation of strong stress waves in nonlinear elastic plates has been proposed by the authors for points in the interior of the domain of calculation. It was demonstrated that the numerical scheme based on this method maintains very well the form of the wave front in cases with strong anisotropy. Nonlinear behaviour of plastic materials could currently only be taken into account using deformation theory. As with many materials, especially for some rubber-like plastics and brittle materials like concrete and metal castings the nonlinear part is often dominant. With this in mind, valid statements can be made with the available program in many cases.},
 bibtype = {inproceedings},
 author = {Ballmann, Josef and Staat, Manfred},
 editor = {Chiem, C Y and Kunze, H D and Meyer, L W},
 booktitle = {Impact Loading and Dynamic Behaviour of Materials, IMPACT ’87 - International Conference on Impact Loading and Dynamic Behaviour of Materials. May 18-22, 1987, Bremen, Germany}
}

A method of bicharacteristics for the computation of stress waves in linear elastic plates with straight boundaries was first devised by CLIFTON on the basis of a proposal for gas dynamics. Also starting from gas dynamics we applied this method to plates with curved boundaries and plate structures including shear and bending. Of major interest was the computation of stress concentrations as a result of the focussing of waves that were reflected from concave boundaries, as well as from internal boundaries. We compared our numerical results with experiments that were carried out in the Shock Waves Laboratory of Aachen Technical University. Good correlations were observed which we wish to further improve upon by means of a higher order plate theory. Currently we have developed methods of characteristics for non-elastic and nonlinear materials. In regard to non-elastic materials, we have previously considered linear elastic-viscoplastic laws such as the PERZYNA model, as well as the BODNER-PARTOM model. They lead to semi-linear hyperbolic laws, i.e. the highest derivatives appear only linearly. In the case of nonlinear materials with large deformations and physical nonlinearity, we have considered isotropic elastic media. If homogeneously prestressed they show anisotropic wave propagation, resembling the observations made in linear transversely isotropic elastic media. Also in plasticity very similar effects of anisotropic wave propagation are expected, if e.g. PRANDTL-REUSS-like laws are used. Generally the strain induced anisotropy changes from point to point according to the local deformation. Attempts have been made to use this anisotropic effect in the non destructive evaluation of residual stresses with ultrasonics. A numerical method of bicharacteristics for the computation of strong stress waves in nonlinear elastic plates has been proposed by the authors for points in the interior of the domain of calculation. It was demonstrated that the numerical scheme based on this method maintains very well the form of the wave front in cases with strong anisotropy. Nonlinear behaviour of plastic materials could currently only be taken into account using deformation theory. As with many materials, especially for some rubber-like plastics and brittle materials like concrete and metal castings the nonlinear part is often dominant. With this in mind, valid statements can be made with the available program in many cases.

@phdthesis{
 title = {Nichtlineare Wellen in elastischen Scheiben. [Nonlinear waves in elastic discs.]},
 type = {phdthesis},
 year = {1987},
 pages = {VIII, 1-197},
 websites = {http://d-nb.info/890929769},
 institution = {RWTH-Aachen University},
 department = {Faculty of Mathematics, Computer Science and Natural Sciences},
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 notes = {summa cum laude},
 private_publication = {false},
 abstract = {Beschleunigungswellen breiten sich mit Unstetigkeiten der Beschleunigungegn und gewisser anderer zweiter Ableitungen des Verschiebungsfeldes aus. Nichtlineare Ausbreitungsprobleme lassen sich mit der Charakteristikentheorie weitgehend exakt behandeln. Auch die Theorie singulärer Flächen wird im Rahmen dieser Arbeit in die Charakteristikenheorie eingeordent. Bei der numerischen Intergration in Welleffächen macht man von der Stetigkeit der in den Verträglichkeitsbedingungen auftretenden inneren Ableitungen wesentlichen Gebrauch. Damit nimmt man jedoch als Verfahrensnachteil in Kauf, daß die Wellenflächen als Träger der Unstetigkeiten in jedem Rechenpunkt konstruiert werden müssen. Dadurch sind die Cahrakteristikenverfahren weniger flexibel und ihre Entwicklung vergleichsweise aufwendig, wenn - anders als in dieser Arbeit - Stoßwellen explizit zu berücksichtigen sind. [Acceleration waves propagate with discontinuities of acceleration and certain other second derivatives of the displacement field. Nonlinear propagation problems can be treated exactly with the theory of characteristics. Also the theory of singular surfaces is integrated into the theory of characteristics in the context of this work. The numerical integration on wave surfaces makes use of the continuity of the internal derivatives occurring in the compatibility conditions. However, the disadvantage of this method is that the wave surfaces have to be constructed as supports of the discontinuities in each calculation point. This makes the methods of characteristics less flexible and their development comparatively complex if - unlike in this thesis - shock waves are explicitly to be considered.]},
 bibtype = {phdthesis},
 author = {Staat, Manfred}
}

Beschleunigungswellen breiten sich mit Unstetigkeiten der Beschleunigungegn und gewisser anderer zweiter Ableitungen des Verschiebungsfeldes aus. Nichtlineare Ausbreitungsprobleme lassen sich mit der Charakteristikentheorie weitgehend exakt behandeln. Auch die Theorie singulärer Flächen wird im Rahmen dieser Arbeit in die Charakteristikenheorie eingeordent. Bei der numerischen Intergration in Welleffächen macht man von der Stetigkeit der in den Verträglichkeitsbedingungen auftretenden inneren Ableitungen wesentlichen Gebrauch. Damit nimmt man jedoch als Verfahrensnachteil in Kauf, daß die Wellenflächen als Träger der Unstetigkeiten in jedem Rechenpunkt konstruiert werden müssen. Dadurch sind die Cahrakteristikenverfahren weniger flexibel und ihre Entwicklung vergleichsweise aufwendig, wenn - anders als in dieser Arbeit - Stoßwellen explizit zu berücksichtigen sind. [Acceleration waves propagate with discontinuities of acceleration and certain other second derivatives of the displacement field. Nonlinear propagation problems can be treated exactly with the theory of characteristics. Also the theory of singular surfaces is integrated into the theory of characteristics in the context of this work. The numerical integration on wave surfaces makes use of the continuity of the internal derivatives occurring in the compatibility conditions. However, the disadvantage of this method is that the wave surfaces have to be constructed as supports of the discontinuities in each calculation point. This makes the methods of characteristics less flexible and their development comparatively complex if - unlike in this thesis - shock waves are explicitly to be considered.]

@article{
 title = {Anisotrope Wellenausbreitung in isotropen hyperelastischen Scheiben},
 type = {article},
 year = {1987},
 pages = {T241-T243},
 volume = {67},
 websites = {http://doi.wiley.com/10.1002/zamm.19870670406},
 publisher = {WILEY-VCH Verlag (Akademie Verlag GmbH)},
 id = {e7362369-fa06-3b49-9f2a-392d170e829f},
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 abstract = {Isotrope nichtlinearelastische Körper zeigen bei Wellenausbreitung lösungsabhängige anisotrope Effekte. Die Ausbreitung einer Punktstörung kann durch Linearisierung um eine homogene Vorverformung in Analogie zur linearen Elastizitat transversisotroper Medien diskutiert werden. Zur Berechnung von Wellenvorgängen in beliebig, insbesondere in homogen verzerrten Scheiben wird ein numerisches Charakteristikenverfahren 2. Ordnung vorgestellt, das die Anisotropie der Wellenausbreitung lokal berücksichtigt und auch global erhält.},
 bibtype = {article},
 author = {Staat, Manfred},
 doi = {10.1002/zamm.19870670406},
 journal = {ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik},
 number = {4}
}

Isotrope nichtlinearelastische Körper zeigen bei Wellenausbreitung lösungsabhängige anisotrope Effekte. Die Ausbreitung einer Punktstörung kann durch Linearisierung um eine homogene Vorverformung in Analogie zur linearen Elastizitat transversisotroper Medien diskutiert werden. Zur Berechnung von Wellenvorgängen in beliebig, insbesondere in homogen verzerrten Scheiben wird ein numerisches Charakteristikenverfahren 2. Ordnung vorgestellt, das die Anisotropie der Wellenausbreitung lokal berücksichtigt und auch global erhält.

@inbook{
 type = {inbook},
 year = {1985},
 pages = {235-252},
 websites = {http://linkinghub.elsevier.com/retrieve/pii/B9780444425201500153},
 publisher = {Elsevier, Amsterdam},
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 abstract = {The propagation of mechanical waves in plates of isotropic elastic material is investigated. After a short introduction to the understanding of focussing of stress waves in a plate with a curved boundary, the method of characteristics is applied to a plate of hyperelastic material. Using this method the propagation of acceleration waves is discussed. Based on this a numerical difference scheme is developed for solving initial-boundary-value problems and applied to two examples: propagation of a point disturbance in a homogeneously finitely strained non-linear elastic plate and geometrical focussing in a linearly elastic plate.},
 bibtype = {inbook},
 author = {Ballmann, Josef and Raatschen, Hans-Jürgen and Staat, Manfred},
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 chapter = {High stress intensities in focussing zones of waves},
 title = {Local Effects in the Analysis of Structures.}
}

The propagation of mechanical waves in plates of isotropic elastic material is investigated. After a short introduction to the understanding of focussing of stress waves in a plate with a curved boundary, the method of characteristics is applied to a plate of hyperelastic material. Using this method the propagation of acceleration waves is discussed. Based on this a numerical difference scheme is developed for solving initial-boundary-value problems and applied to two examples: propagation of a point disturbance in a homogeneously finitely strained non-linear elastic plate and geometrical focussing in a linearly elastic plate.

@inproceedings{
 title = {Anisotrope Ausbreitung und Fokussierung von Beschleunigungswellen in vorgespannten nichtlinearelastischen Scheiben},
 type = {inproceedings},
 year = {1985},
 pages = {140-158},
 institution = {RWTH Aachen},
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 author = {Staat, Manfred and Ballmann, Josef},
 booktitle = {Wellenfokussierung, Kolloquium des SFB 27, Juli 3-4, 1985, Aachen, Germany}
}

@phdthesis{
 title = {Untersuchung der Biegeschwingungsanregung gerader elastischer Führungen durch bewegte, schwere Körper mit Hilfe der Methode der Finiten Elemente},
 type = {phdthesis},
 year = {1980},
 institution = {RWTH Aachen University, Faculty of Mechanical Engineering},
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