Analysis And Evaluation Of Three Dimensional Residual Stress Field Induced By Laser Shot Peening

Residual compressive stresses are used to improve anti-fatigue properties of material. The three-dimensional residual stress field induced by laser shot peening (LSP) are studied preliminarily. The main contents are as follows:The mechanical response of metal material and generative mechanism of residual stress under high amplitude shock wave loading were discussed, the spatial distribution of three-dimensional residual stress were analyzed. Based on X-ray measuring technique, the measurement of three-dimensional residual stress along surface and depth was introduced.Based on the FEA code ABAQUS, FEA model of the LSP process was established. Some key techniques, such as the constitutive model of material and shock wave space-time loading were discussed and the dynamic variation process of stress-strain in LSP was simulated. The value and spatial distribution of the three-dimensional residual stress induced by LSP, especially the impact on the three-dimensional residual stress field under various LSP process parameters were studied.The model of fuzzy comprehensive evaluation of residual stress field was established based on fuzzy mathematics theory. The two-band fuzzy comprehensive evaluation was applied. Not only all the influencing factors were considered but also all the information of every evaluation stage was reserved and three-dimensional residual stress field was evaluated synthetically to determine its advantages and disadvantages. On this basis, by use of fatigue analysis software MSC.Fatigue, the fatigue property analysis method under three-dimensional residual stress field was investigated, which provides an effective way to evaluate the effect of anti-fatigue further after LSP and also verifies the feasibility of fuzzy comprehensive evaluation for three-dimensional residual stress field.LSP experiments were carried out with 6061-T6 aluminum alloy plate, the surface and in-depth residual stresses distribution were measured using X-ray diffraction combining with double-sided electrolytic polishing removal of layer method. The surface morphology of impact craters, micro-hardness and microstructure were analyzed before and after LSP, and the reasons were explained. The internal relations between the micro-hardness and residual stress distribution along the depth were explored. The experiment results showed good consistency with the numerical simulation results.