Numerical simulation of transient temperature and residual stresses in friction stir welding of 304L stainless steel

Three-dimensional nonlinear thermal and thermo-mechanical numerical simulations are conducted for the friction stir welding (FSW) of 304L stainless steel. The finite element analysis code—WELDSIM, developed by the authors specifically for welding simulation, was used. Two welding cases with tool rotational speeds of 300 and 500 rpm are analyzed. The objective is to study the variation of transient temperature and residual stress in a friction stir welded plate of 304L stainless steel. Based on the experimental records of transient temperature at several specific locations during the friction stir welding process for the 304L stainless steel, an inverse analysis method for thermal numerical simulation is developed. After the transient temperature field is determined, the residual stresses in the welded plate are then calculated using a three-dimensional elastic–plastic thermo-mechanical simulation. The effect of fixture release after the welding on the residual stresses is also studied. Comparison with the residual stress fields measured by the neutron diffraction technique shows that the results from the present numerical simulation have good agreement with the test data.