Laser Generated Rayleigh and Lamb waves

Abstract

Laser Generated Rayleigh and Lamb waves are studied in Aluminum samples. Broadband Rayleigh waves are generated using a TEM00 mode Nd:YAG laser. In the thermoelastic regime the Rayleigh wave impulse response from a laser line source is a negative going (inward displacement) delta function. It is shown how aperturing the laser beam produces high thermal gradients resulting in large amplitude broadband Rayleigh waves. The symmetric and antisymmetric Lamb wave modes in thin aluminum plates are also studied and a simple model showing that there is a 50:50% energy split between these two modes is developed.