Study On Response And Mechanical Properties Of Material After Micro-scale Laser Shot Peening

Micro-scale laser shot peening (μLSP) technique was proposed, it uses mechanical effect of the high amplitude shock wave induced by high-energy laser to improve the material properties. In this paper, the primary process and mechanism ofμLSP were studied and numerical simulations and experiments of theμLSP were conducted. Main contents are shown as following:The wave-solid interaction and strengthening mechanism in micro-scale were studied. Based on the ellipsoidal wave propagation theory, a model ofμLSP process was establised and the shock wave velocity was obtained. By means of detonation wave and explosive gas dynamics theory, temporal and spatial distribution of shock wave pressure was investigated and the analytical equation was deduced, the results provided guidance for the further study of mechanism and numerical analysis ofμLSP process.Finite element method (FEM) was applied to the investigation of theμLSP process. An appropriate analysis mode for the FEM simulation ofμLSP was established with ABAQUS code, some key technical issues in the simulations were solved and the simulation process forμLSP was also designed. The relationship betweenμLSP induced surface dynamic stress, residual stress characteristics and processing parameters were researched, meanwhile surface micro-topography of shin films after micro-scale laser peening were analyzed, which provided theoretical basis for optimization of processing parameters and effective controlling of surface quality duringμLSP.Box-Behnken method of Design Expert software was used to carry out experimental design, the characteristics of residual stress measured from various laser processing parameters were extracted and treated, the influence of the various factors and interaction of factors to characterization of the residual stress was established. Quadratic regression model of prediction of average surface residual stress was established, and the reliability of model was tested. Finally, the optimal combination of laser process parameters oriented to average surface residual stress was optimized, which provided guidance forμLSP process parameters optimization and residual stress control.μLSP experiments were carried out on typical copper materials. Surface coating morphology, shocking shoot morphology, micro-hardness of material and superficial coat microstructure of thin films afterμLSP were tested and analyzed, the creation reasons were analyzed also, which would provide good guidance for further study ofμLSP.