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.
