Numerical Simulation Of Residual Stress Field Induced By Laser Shock Processing On Fe-Ni Alloy

Based on the mechanism of LSP inducing residual stress field, in this paper, the residual stress field of Fe-Ni alloy was simulated and then experimental research was made on LSP of Fe-Ni alloy. The main contents were as following:The mechanism of laser shock wave was described. Fabbro model and its corrected model in the confined mode were analyzed. According to the theory of plastic-elasticity dynamics and the theory of shock wave, the constitutive equations of material were analyzed when laser shock wave propagated in material in one dimension strain compress.Combined with the constitutive equations in one dimension strain compress , the forming processing of residual stress field induced by LSP was analyzed. Then the main influencing factors of residual stress field were analyzed, especially the shock parameter.Based on ANSYS/LS-DYNA software, the FEA analysis model was founded, considering the finite element theory. Some key problems were discussed. The results of numerical simulation were analyzed. The effects of laser shock parameters on the residual stress field of Fe-Ni alloy were studied by numerical simulation, which indicated that:The peak surface residual compressive stress increased as the laser power density increased when the laser power density was below a fixed value, and then decreased. At the same time, the depth of the residual compressive stress was increasing all the time. The maximum and the depth of the residual compressive stress increased as the laser pulse duration increased, which showed it could improve the residual compressive stress field by increasing the laser pulse duration. The simulated results also revealed that increasing the laser spot size could resulted in an increase in the maximum and the depth of the residual compressive stress, especially the latter.Experimental research was made on LSP of Fe-Ni alloy, the results of the experiment were analyzed. The results indicated that the average microhardness of the shock zone of the samples increased by about 16%. The results also showed LSP induced martensitic transformation,cellular dislocation of high density and twin. In contrast with FEA and experimental data, the simulated data of residual stress field was well consistent with the experimental data.