Analysis of elastic wave propagation excited by acoustic non-contact method

Evaluation of optimal slope angle of an air-coupled transducer (ACT) is important, to allow for effective generation of Lamb waves in solid structures. This effectiveness relies on both generation of desired wave modes, amplitude of measured signals and large coverage area for damage detection. Phenomenon of non-contact elastic waves generation in plate based on ACT is considered assuming few approaches. Numerical modeling in COMSOL is related to the analysis of different plate thicknesses and ACT excitation frequencies. Experimental research is based on wave excitation using piezoceramic ACT with a base excitation frequency of 40 kHz and SLDV measurements for a 1 mm-thick plate. A comprehensive investigation of optimal ACT slope angle for the generation of A0 mode is included. Propagation of S0 mode was not observed in numerical as well as experimental results. Optimal slope angle values were estimated in different ways numerically and experimentally with the use of dispersion curves and based on the amplitude of generated waves. Finally, the optimal angle value was determined and utilized for damage detection and localization problem in an aluminum plate.