DP600 dual phase steel thermo-elasto-plastic constitutive model considering strain rate and temperature influence on FEM residual stress analysis of laser welding

The residual stress field during a laser welding of dual phase steel DP600 is simulated by a sequentially coupled thermo-mechanical model. A numerical material constitutive model of elasticity and plasticity of dual phase steel DP600 is performed. Based on the hardening and temperature sensitivity analysis of a previous work, the strain rate sensitivity of dual phase steel DP600 is discussed in details. The elasticity of martensite formed during welding is found to have little influence on residual stresses. A better results is achieved by the proposed hardening term, general strain rate sensitivity model and temperature sensitivity model. The annealing temperature effects on residual stress distribution are analyzed. Residual stresses are higher if annealing temperature is higher. High laser welding power increase distribution area but do not increase magnitude of residual stresses.