Damage detection in pipes based on acoustic excitations using laser-induced plasma

A health-monitoring system is proposed to detect holes drilled in a pipe based on laser plasma acoustic excitations and acoustic measurements. In this system, an acoustic excitation is applied to a pipe via a laser-induced plasma in air generated by a high-power Nd: YAG pulse laser. Laser-induced plasmas can realize non-contact acoustic impulse excitations. A microphone is used to measure the time response of the acoustic pressure. In this study, we focus on the detection of a hole in the pipe. The reflection of the acoustic wave due to a hole drilled in the pipe induces a change in the time response of the acoustic pressure. Applying a continuous wavelet transform to the measured time response data with/without the hole can locate the position of the hole. This study demonstrates the effectiveness of the present damage detection method based on an acoustic excitation using a laser-induced plasma.