Experimental Study on the Mode Conversion of Lamb Waves in a Metal Plate of Stepped Thickness Using Optical Detection

Abstract

The optical observation of the propagation of Lamb waves in an aluminum plate with stepped thickness is described. Lamb waves passing through the aluminum plate were analyzed by two-dimensional Fourier transformation to discriminate modes and thus determine mode conversion. S0-mode and A0-mode Lamb waves corresponding to theoretical dispersion curves were experimentally found to propagate in the aluminum plate. Conversion from A0-mode to S0-mode waves at the thickness step was also observed. This mode conversion of Lamb waves is thus a useful index for detecting defects such as ablation, wear and wall reduction.