Crack detection with gas-coupled laser acoustic detection technique

Gas-coupled laser acoustic detection (GCLAD) is an unestablished ultrasonic detection technique based on the displacement that a laser beam sustains when intersected by an acoustic wave travelling in a fluid. In the present work, GCLAD for the noncontact detection of ultrasound is applied to identify surface defects on metal plates. Two GCLAD configurations are analysed, each associated with different sensitivities to cracks; specifically, GCLAD exhibits the highest sensitivity when inclined perpendicularly to the ultrasonic propagation direction in the air. The high angular selectivity allows evidencing only specific waves, those directly travelling in the component or reflected by defects. A higher ultrasonic amplitude is highlighted for GCLAD compared to air-coupled probes. The work ultimately demonstrates GCLAD's major advantage: the possibility of instantly performing an inspection over an entire line, rather than on a point as for traditional transducers.

Automated summary

Gas-coupled laser acoustic detection (GCLAD) is an unestablished technique for noncontact ultrasound detection based on the interaction of laser and acoustic waves, showing high sensitivity to surface defects on metal plates, especially when perpendicular to the ultrasonic propagation direction in air. It demonstrates a major advantage of instantly inspecting an entire line rather than just a point like traditional transducers.