Investigation On The Influence Of Welding Residual Stress On Fatigue Life Of SAF2205 Stainless Steel

Welding residual stress is the key factor affecting the fatigue life of welded structures.It is of great significance for fatigue design based on residual stress regulation to accurately predict welding residual stress,to deeply understand the mechanism of residual stress affecting fatigue life of welded components,and to establish a fatigue life prediction method considering the effect of welding residual stress.In this paper,SAF2205 stainless steel was taken as the research object.By modifying the fatigue damage constitutive model,a life calculation method considering the evolution law of residual stress was established,which provided a reference for joint life prediction.The main work and conclusions are as follows:(1)The numerical simulation and experimental study on welding residual stress of SAF2205 stainless steel were carried out.The DFLUX subroutine of the double ellipsoid heat source model was compiled,and the welding temperature field was obtained by using the unit life-and-death technique.The thermal-mechanical sequential coupling method was used to predict the residual stress results,and the results were compared with those measured by borehole method.The results show that the residual stresses in the middle and heat-affected zone of the weld are relatively large,and the maximum longitudinal stress is close to the yield strength of the material,which is the focus of fatigue damage analysis.The residual stresses far away from the weld gradually decrease,and the compressive stresses appear at both ends of the weld.The numerical results are in good agreement with the experimental results of drilling method,which verifies the accuracy of the finite element simulation.(2)By modifying the fatigue damage parameters,a fatigue damage constitutive model considering the influence of multiaxial stress was established.Firstly,damage coupling parameters and hardening parameters were obtained according to fatigue test results.Then,the USDFLD subroutine was written to simulate the damage evolution of the round bar specimens under fatigue load,and the damage location and fatigue life were compared with the test results.The results show that the modified damage model can well describe the failure and damage evolution of materials,which is in good agreement with the experimental results.(3)By calculating the fatigue life of plate specimens with and without residual stresses,the fatigue damage propagation process of the two specimens was simulated,and the influence of welding residual stresses on fatigue performance was systematically analyzed.The effect of stress relief heat treatment process parameters on fatigue life was investigated.The results show that the fatigue damage concentrates near the tensile stress of the weld.The damage extends from the middle part of the weld to both ends.The tensile stress reduces the fatigue life,and the compressive stress enhances the fatigue performance.The residual stress has little effect on low-cycle fatigue,but has a greater impact on high-cycle fatigue.The higher the heat treatment temperature,the better the stress relief and fatigue performance and the optimization effect of holding time is not obvious...