Experimental study on the effect of the remaining absorbing layer on laser shock processing

Remaining absorbing layers have a significant influence on the shock effects of metal samples in laser shock processing(LSP). However, the influence laws are still pending. In this paper, the experiments of LSP were conducted with different materials as the absorbing layers. The influence of the thicknesses of the absorbing layer was also studied. To guarantee that there were remaining absorbing layers on the target surface after shock, the laser parameters were carefully chosen. The influence laws of the remaining absorbing layers on the laser shock effect were researched by measuring the laser shock induced-pit sizes and the mechanical properties of the shocked zones. Furthermore, the shock wave signals on the back of the metal samples were tested by PVDF detector. Experimental results show that, the remaining absorbing layers can attenuate shock wave seriously. Therefore, the shock effects are weakened accordingly. Through the experimental and theoretical research, it can be found that there exist an ideal absorbing layer with the optimal acoustic impedance, when the confinement layer and metal sample are determined. With the ideal absorbing layer, we can get the strongest shock effect. For achieving good results in LSP, the absorbing layer material should be carefully chosen according to the confinement layer and metal sample. In the same time, the thickness of an absorbing layer should be controlled reasonably. The results of this paper can provide guidance for choosing the most appropriate absorbing layer for different metal samples in LSP.