3H-4 Measurement of Spatial Distribution of Crack Tips Using Low Power Laser Pulses

An interesting system to detect plane micro cracks in solid materials is proposed. In this system, we have made use of two techniques, two-layered self-made transducers and the low power laser pulses to induce short elastic waves. Here, the two-layered transducer has two roles, transmission of the large amplitude low frequency wave (500 kHz) from PZT transmitter and wideband receiver made of PVDF film. The low frequency excitation causes the fluctuation of closed cracks. With the combination of these techniques, we have succeeded in the measurement of interesting two dimensional images which are in good accordance with the expected position of crack tips