Lamb wave evaluation of concrete plates. Tofeldt, O. & University, L. Ph.D. Thesis.
abstract   bibtex   
This thesis is about the application of Lamb waves for non-destructive evaluation of plate-like concrete structures under one-sided access test condition using a portable equipment consisting of an accelerometer and impact hammer. With this type of equipment and based on array signal processing, the impact-echo (IE) method can be extended with measurements of surface waves; this extension allows an evaluation with Lamb waves. For both the conventional impact-echo method as well as evaluations based on Lamb waves, results in the literature report a systematically underestimated plate thickness. This error is investigated and reproduced in a numerical study and further verified in a measurement. A main source of uncertainty is related to the estimation of a longitudinal wave velocity from first arrivals. To reduce this uncertainty, a new approach for estimation of Poisson’s ratio is proposed. The new approach is based on the amplitude polarization of the S1ZGV Lamb mode: a through-thickness representative estimate of Poisson’s ratio is thereby obtained leading to an overall improved estimation of the Lamb wave plate parameters.
@phdthesis{tofeldt_lamb_nodate,
	title = {Lamb wave evaluation of concrete plates},
	abstract = {This thesis is about the application of Lamb waves for non-destructive evaluation of plate-like concrete structures under one-sided access test condition using a portable equipment consisting of an accelerometer and impact hammer. With this type of equipment and based on array signal processing, the impact-echo (IE) method can be extended with measurements of surface waves; this extension allows an evaluation with Lamb waves. For both the conventional impact-echo method as well as evaluations based on Lamb waves, results in the literature report a systematically underestimated plate thickness. This error is investigated and reproduced in a numerical study and further verified in a measurement. A main source of uncertainty is related to the estimation of a longitudinal wave velocity from first arrivals. To reduce this uncertainty, a new approach for estimation of Poisson’s ratio is proposed. The new approach is based on the amplitude polarization of the S1ZGV Lamb mode: a through-thickness representative estimate of Poisson’s ratio is thereby obtained leading to an overall improved estimation of the Lamb wave plate parameters.},
	language = {en},
	author = {Tofeldt, Oskar and University, Lund},
}

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