Study And Optimizing Control On Residual Stress Field Of Workpiece In Laser Peen Forming

Laser peen forming (LPF) is a novel technique that laser-induced shock wave is used to impart residual stress field in the material and finally shape the sheet metal. It is the combination of traditional peen process and new laser process. It is the key to optimize and control the residual stress field in the LPF to shape the sheet precisely. In this paper, the main contents were as following:Firstly, the forming mechanism of the laser-induced shockwave was analyzed theoretically, the propagation and attenuation of shock waves was probed. The dynamic response of sheet metal acted on the linear dimension strain compress of the Shockwave loading was described. The mechanism of residual stress in the material and the primary factors having effect on residual stress were also analyzed.Secondly, the numerical model of Shockwave loading was established based on the ANSYS/LS-DYNA soft, considering the trait of LPF and the finite element theory. The residual stress field in the LPF was simulated by the explicit-implicit sequential solving method. It was presented that the shock path had great impact on the entire distribution of residual stress in deformed sheet metal.Thirdly, the optimizing model of residual stress in the LPF was established. The range of laser parameters was preliminary optimized by estimating the laser energy in sheet deformation, and optimized further by orthogonal method based on the numerical simulation. The preferable level compages was gained. The shock path, shock times and prestress process were used to control the stress modality.Finally, the experiments of LPF with 6061-T6 AL alloy and SUS304 stainless steel were carried out to investigate the influence of different materials, shock paths and shock times to the stress distribution and sheet deformation. The residual stress test of typical sample indicated that both the top and bottom of the sheet in the peened zone were compressive.