Simulation and analysis of fatigue life of 7075 aluminum alloy FSW welded joint

Process parameters influence the temperature field and stress field of friction stir welded (FSW) joints, thereby affecting their fatigue performance. Investigating the relationship among "process parameters-field variations-fatigue life" is crucial for improving the fatigue life of aluminum alloy products. Based on numerical simulation, this study analyzes the temperature and stress field variations of 5mm thick 7075-T6 aluminum alloy joints under different welding parameters, coupling Fe-safe software to explore fatigue life changes. The findings reveal, ① The temperature gradient \nabla f continuously expands from the nugget zone to the base metal zone, leading to more pronounced thermal strain differences and progressively increasing residual stresses. ② The primary factor influencing temperature is the spindle rotation speed, with a 100r/min increase within the parameter range raising peak temperature by approximately 9%. ③ Post-welding residual stresses primarily manifest as longitudinal stresses along the weld direction, proportional to welding speed and inversely proportional to rotation speed. ④ At low welding speeds, fatigue life is inversely related to rotation speed, with the optimal parameter window requiring a rotation-to-welding speed ratio K between 4 ~ 5. However, the relationship with welding speed is irregular. These results, experimentally validated, are reasonable and reliable. They not only provide a theoretical basis for optimizing FSW process parameters but also offer technical support and theoretical justification for the widespread application of 7075 aluminum alloy structural components requiring long service life, demonstrating significant value and practical relevance.