Laser ultrasonic technology and its applications in nondestructive testing in solids

Abstract

As a new branch of ultrasonics, laser-induced ultrasonics is developed quickly, and has wide applications in many areas recently, for its advantages such as non-contract operation, non-destructive testing, broad bandwidth, high time resolution, high space resolution, no shape limits on samples, etc. Firstly, the principles of the laser-induced ultrasonic generation, e.g., the thermoelastic excitation theory and the ablation excitation theory, were introduced. This paper also described the laser-induced ultrasonic detection by means of the confocal Fabry-Perot interferometer (CFPI). And then its applications in non-destructive testing in solids were introduced in detail. Based on the principles of the laser-induced ultrasonic generation and detection, the structure of the laser ultrasonic detection system was presented. From the velocities of compress wave and surface wave measured by the detection system, elastic constants of aluminium were worked out. The experimental results were in good accordance with the theoretical predictions, which demonstrated that laser ultrasonic technique is practical, reliable and effective. Future prospects for such technology were pointed out finally.