Nondestructive detection of small defect by laser ultrasonics

摘要

The inside defect in carbon steel with the diameter of 100 μm was successfully detected by laser ultrasonics technique. Irradiation of a Q-switched Nd:YAG laser was used for ultrasonic generation, and a frequency doubled CW Nd:YAG laser combined with a Fabry-Perot etalon were used for detection of ultrasonic vibration on the specimen surface. The ratio of the inside defect diameter to the ultrasonic wavelength was estimated to be ～0.067. We also measured the dependence of the amplitude ratios of the first defect signal and the second longitudinal wave to the first longitudinal wave on the defect diameter.