This paper proposes a non-contact and non-destructive method to generate Lamb waves against a target structure using the impulse excitation force generated by laser-induced plasma (LIP). When a high power pulse laser is irradiated in air and its laser fluence exceeds 1015 W/m2, a plasma is formed. While the plasma in air expands in high speed, shock waves on the spherical surface are generated and these shock waves become the impulse excitation force against a target structure, resulting in the non-contact and non-destructive approach. A 2024 aluminum alloy plate is used as the test piece in the experiment, and the dynamic characteristics of the Lamb waves generated from LIP shock waves are measured. Phase velocity and group velocity of generated Lamb waves were compared to the calculated values from Rayleigh-Lamb frequency equations and we found that maximum error was 5% and its frequency component included at least 400 kHz. Further, we investigated the relationship between the distance from the LIP shock wave–generating location to a test piece and the dynamic characteristics of the generated Lamb waves. This method can control the amplitude and the frequency components of generated Lamb waves by changing this distance.
ASJC Scopus subject areas