Cavitation Damage Evaluation Using Laser Impacts

Ultrasonic waves generated by a pulsed Nd-YAG laser are being adopted to evaluate the cavitation damage, so-called pitting, caused by proton beam injection in pulsed neutron sources. The wave's propagation behavior depends on the density and depth of the pits. To quantitatively understand the relationship between the pits and the wave propagation behavior, the artificial pits were imposed on the evaluated specimen while controlling the density and depth. A laser Doppler vibrometer was used to remotely detect the ultrasonic waves generated by the Nd-YAG laser. It was found that the two parameters, namely, the maximum negative peak value and the attenuation of received waveforms were useful for quantitatively evaluating the damage. As a result, cavitation damage with a peak-to-peak roughness of more than 15 mu m was successfully evaluated.