Inspection of cracks with focused angle beam laser ultrasonic wave

In this work, in order to improve the detecting ability of laser ultrasonic testing technique for inner cracks in metals, an arc-line-focused laser source is proposed to generate focused angle-beam bulk waves in thermoelastic regime. The arc-line-focused laser source is achieved by passing an expanded and collimated laser beam through a convex and axicon lens off-center. The distribution of the shear waves generated by the arc-line laser source were detected by a laser interferometer to evaluate the focal area. Finally, the measurement of artificial cracks at the bottom surface of aluminum specimen with using the focused angle-beam bulk waves is investigated by experiment.