Evolution of the Die-Wall Pressure during the Compression of Biconvex Tablets: Experimental Results and Comparison with FEM Simulation. Mazel, V.; Diarra, H.; Busignies, V.; and Tchoreloff, P. Journal of Pharmaceutical Sciences, 104(12):4339–4344, December, 2015.
Evolution of the Die-Wall Pressure during the Compression of Biconvex Tablets: Experimental Results and Comparison with FEM Simulation [link]Paper  doi  abstract   bibtex   
Capping is a classical manufacturing problem for tablets, which is known to affect more biconvex tablets than flat-faced ones. One reason could be the development of a higher residual die-wall pressure during unloading. Unfortunately, contradictory results were published on the subject. In this work, the evolution of the die-wall pressure during the compaction of biconvex tablets was studied experimentally and using finite element method (FEM) modeling. It was compared with the case of flat-faced tablets. Experimental and numerical results showed that during the compression of biconvex tablet, a lower maximum die-wall pressure and a higher residual die-wall pressure were obtained compared with the case of flat-faced tablet. Moreover, both approaches showed, for biconvex tablets, a temporary increase of the die-wall pressure at the end of the unloading phase. FEM demonstrated that this phenomenon was due to a gradual loss of contact between the punch and the tablet from the side to the center. This complex unloading behavior causes the temporary increase of the die-wall pressure and the development of a shear stress between the convex part and the land of the tablet. This could explain the capping tendency of biconvex tablets.
@article{mazel_evolution_2015,
	title = {Evolution of the {Die}-{Wall} {Pressure} during the {Compression} of {Biconvex} {Tablets}: {Experimental} {Results} and {Comparison} with {FEM} {Simulation}},
	volume = {104},
	issn = {0022-3549},
	shorttitle = {Evolution of the {Die}-{Wall} {Pressure} during the {Compression} of {Biconvex} {Tablets}},
	url = {http://www.sciencedirect.com/science/article/pii/S0022354915000994},
	doi = {10.1002/jps.24682},
	abstract = {Capping is a classical manufacturing problem for tablets, which is known to affect more biconvex tablets than flat-faced ones. One reason could be the development of a higher residual die-wall pressure during unloading. Unfortunately, contradictory results were published on the subject. In this work, the evolution of the die-wall pressure during the compaction of biconvex tablets was studied experimentally and using finite element method (FEM) modeling. It was compared with the case of flat-faced tablets. Experimental and numerical results showed that during the compression of biconvex tablet, a lower maximum die-wall pressure and a higher residual die-wall pressure were obtained compared with the case of flat-faced tablet. Moreover, both approaches showed, for biconvex tablets, a temporary increase of the die-wall pressure at the end of the unloading phase. FEM demonstrated that this phenomenon was due to a gradual loss of contact between the punch and the tablet from the side to the center. This complex unloading behavior causes the temporary increase of the die-wall pressure and the development of a shear stress between the convex part and the land of the tablet. This could explain the capping tendency of biconvex tablets.},
	number = {12},
	urldate = {2017-08-25},
	journal = {Journal of Pharmaceutical Sciences},
	author = {Mazel, Vincent and Diarra, Harona and Busignies, Virginie and Tchoreloff, Pierre},
	month = dec,
	year = {2015},
	keywords = {compression, excipients, powder technology, tablet, tableting},
	pages = {4339--4344}
}
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