Welding numerical simulation of 316L stainless steel based on nonlinear mixed hardening model and mechanical melting point

Objective Elastoplastic materials often exhibit mechanical characteristics of both dynamic hardening and isotropic hardening. Nonlinear mixed hardening model can accurately reflect cyclic mechanical behavior of elastoplastic materials. Besides, when welding temperature reaches or exceeds mechanical melting point, accumulated plastic strain at high temperatures becomes zero. When the temperature cools down to mechanical melting point, plastic strain recovers. The aim of the paper is to verify influence of nonlinear mixed hardening model and mechanical melting point on welding numerical simulation results of 316L stainless steel. Methods Isothermal multi-stage cyclic load tests have been conducted at different temperatures, cyclic hardening characteristics of material has been obtained, and nonlinear mixed hardening models have been proposed to characterize stress-strain evolution process of elastoplastic materials during the welding process at different temperatures. Then, Satoh tests have been carried out by Gleeble 3500 testing machine to research stress evolution process in different regions of welded joints, relationship between residual stress and peak temperature has been established, and mechanical melting point of material has been calculated. Finally, welding process of 316L stainless steel plates with a three-slot weld has been simulated using finite element method, and effects of constitutive model and mechanical melting point on welding residual stress have been studied. Results Nonlinear mixed hardening model for 316L stainless steel has been established, and this model can accurately predict stress-strain curve under cyclic loading. Mechanical melting point has been calculated, and the value is 870 ℃. Effects of hardening model and mechanical melting point on welding residual stress have been analyzed. Conclusion The experimental and numerical simulation results show that considering mechanical melting point and nonlinear mixed hardening model, welding residual stress can be more accurately obtained.