Laser-generated ultrasound with an array of melting sources

We investigated the YAG laser-generated ultrasonic wave in a solid with an array of rectilinear sources in the melting regime. By adapting the melting rectilinear sources, a 31.2 gain factor of amplitude of the excited ultras ound can be obtained for the aluminum (Al) sample in comparison with the ul trasound generated by rectilinear sources in the thermoelastic regime. In t he melting regime, the sample surface remains undamaged during the inspecti on. Calculations and experimental results show that the array characteristi cs and the detection point will decide the increase of amplitude, center fr equency, bandwidth, and directivity pattern of the narrow-band ultrasound s ignals generated by a melting-source array. Through our research, the array of melting sources is proved to be a useful tool to enhance the generation efficiency and detection sensitivity in nondestructive inspection.