Numerical Simulation Study of Defect Detections by Using Laser Array Generated Giant Acoustic Waves

Based on the classical theory of laser ultrasound generation in a thermoelastic regime, the generation of ultrasound by laser array source irradiation is simulated by the finite element method. The propagation and interaction of the laser-generated ultrasound with a bulk defect are studied. By changing the trigger time delay of a spatially evenly distributed laser array source, giant bulk waves with specific wavefronts and amplitudes several times larger than those of waves generated by a single laser source can be obtained. The interaction between giant acoustic waves and a bulk defect is compared with that in the model without the defect obtained under the same conditions. Results show that compared with a single-pulse generated acoustic wave, the detectability of multiple-source generated giant acoustic waves to defects can be improved significantly.