| Laser generation and detection of surface acoustic waves (Rayleigh Waves) and Lamb waves were studied theoretically and experimentally. Rayleigh and Lamb waves were generated in a variety of materials using a pulsed laser focused on the sample surface in the form of a line source. Multiple line sources were used to alter the spectral content of the generated waveforms. Results from multiple line sources were compared to those from a single line source. A laser ultrasonic C-scanning system was constructed, and used with surface acoustic waves to perform C-scans. Theoretical support for these experiments was developed. Dispersion relations for Lamb waves in orthotropic materials were determined, and used along with results from a transient thermal diffusion process to simulate Lamb waves. Numerical results for the two lowest modes a0 and s0 were extended to investigate the effect of multiple generation sources. |
