Excitation characteristics and defect detection application of arc laser ultrasound based on light source modulation

In order to improve the efficiency of bulk wave excitation and defect detection capability in the thermoelastic mode, this paper built a laser ultrasonic detection platform based on the modulation method of laser light source. The propagation characteristics of ultrasonic bulk wave in a single layer of metal plate stimulated by arc laser were analyzed theoretically and experimentally, and the layered defects in multi-layer metal plate were detected on this basis. The experimental results showed that, under the thermoelastic mode, the arc laser was able to excite stronger bulk wave signals compared with the conventional point laser; the arc radius had a significant effect on the bulk wave excitation efficiency, while the excitation efficiency was positively correlated with the arc angle. In addition, the arc laser had the ability to detect small defects, but its detection capability and detection resolution were constrained by each other.