Laser Shock Processing Of 40Cr Steel And Numerical Simulation Of Residual Stress Field Induced By LSP

Laser shock processing (LSP) is a new surface modification technology. In the process of LSP, the laser with high power density and burst pulse irradiates on metallic material, the coating on surface of material vaporized rapidly, forming plasma, the plasma exploded to induce a high pressure shock wave, which can modify the microstructure of material superficial layer and results in a high compressive residual stress in material superficial layer. So that LSP can improve some mechanical properties of metallic materials, such as surface hardness, wear strength, corrosion resistance, fatigue resistance and so on. LSP can effectively strengthen materials without changing chemical components of material surface, especially can prolong the fatigue life of metallic materials greatly. LSP has extensive applied foreground in some modern manufacturing such as aerospace industry, automotive engineering, internal combustion engine manufactory and so on.In this paper, the character of laser shock wave was discussed .According to the theory of plasticity dynamics and the theory of stress wave, the constitutive equations of material was analyzed when laser shock wave propagates in material, the propagation course of typical laser shock wave in material was analyzed. The effects of laser shock processing on the surface micro-hardness, residual stress of 40Cr steel surface layer were studied. The experimental result indicated that LSP induced high density dislocation in the surface layer of 40Cr steel, increased the micro-hardness of 40Cr steel surface, resulted in high compressive residual stress in the 40Cr steel surface layer .The finite element software ANSYS/LS-DYNA was applied to simulate the residual stress field of 40Cr steel surface layer induced by laser shock processing. The solutions to the main problems about building finite element model of LSP in ANSYS were given. The three dimensional finite element model of laser shock processing of 40Cr steel had been built. The numerical simulation of residual stress field of 40Cr steel surface layer induced by laser shock processing was realized. The results of numerical simulation were discussed. The simulated data of residual stress had a good consistent with the measured data of residual stress by comparison. The effects of laser parameters on the residual stress field of 40Cr steel surface layer were studied by simulation. The experiment of laser shock processing of 35CD4 steel which did by P. Ballard was simulated by ANSYS/LS-DYNA. The experimental result of residual stress and simulation result of residual stress were analyzed by comparison. The comparison indicated that the simulation result of residual stress also had a good consistent with the measured result.