Acoustic Signature Measurement to Identify Laser-Induced Breakdown in Water during Laser Shock Peening

A prevalent non-destructive evaluation method for identifying and analyzing the acoustic waves produced by material deformation and damage is acoustic emission monitoring. In this work, laser shock peening was used in conjunction with acoustic emission monitoring. To determine the acoustic event of laser-induced breakdown in water, the acoustic signals were analyzed. To attain the required compressive residual stresses and prevent undesirable damage, the acoustic emission signals can also be utilized to optimize the laser shock peening parameters, such as the laser energy and spot size. Thus, to investigate the possibilities of acoustic emission monitoring as a tool for the in-situ characterization of laser shock peening, offering insights into the underlying physical processes and help improving the quality of the treated parts. It was found that the plasma breakdown during the laser shock peening intensely hinders the performance as a compressive residual stress on the surface were observed halved (from –216 MPa to –82 MPa) when comparing the setups with and without the plasma breakdown. Thus, by utilizing the acoustic signals the harmful laser-induced breakdown can be detected and optimizing it can enhance process efficacy.