張 月琳

This paper proposes a health monitoring system for detecting a blockage in a pipe using the acoustic vibration excitation with high power laser. Non-contact acoustic impulse excitation can be applied to acoustic fields by using a shock wave generated by laser-induced breakdown in air. A high-power Nd:YAG pulse laser is used in the present vibration testing system for generating the laser-induced breakdown in acoustic fields. The laser excitation makes a precise measurement of the acoustic resonant frequency in wide frequency range possible with high reproducibility. The acoustic resonant frequency changes by the blockage and its position in the pipe. In this study, the detection of the blockage in the pipe is focused. The acoustic resonant frequencies in the pipe with/without the blockage are measured by a microphone. Then the position of the blockage is identified by evaluating the cross section ratio between the pipe and the blockage analyzed from the measured data.