Influence of Post-Heat Treatment Conditions on the Fatigue Life of T-Type Plate Fillet Welds

Improving the fatigue life of welded steel structures remains a critical topic in structural engineering. Numerous studies have shown that residual stress and welding-induced deformation significantly influence fatigue performance. Post-weld heat treatment (PWHT) is widely employed to relieve residual stress; however, its effectiveness varies depending on the treatment temperature and method. Moreover, while PWHT can reduce residual stress, it may also increase or decrease welding deformation depending on the applied process, thereby affecting fatigue life.In this study, fatigue finite element (FE) analyses were conducted to evaluate the heating temperature and optimal positions of post-weld heat treatment (PWHT) to enhance the fatigue life of T-type plate fillet welds. Fillet welding was applied to a T-shaped steel specimen to reproduce welding-induced residual stress and deformation. The study investigated how the reduction in residual stress by post-weld heat treatment (PWHT), along with the accompanying welding deformation, affects fatigue life. A three-stage FE simulation was performed: (1) 3D non-steady heat conduction FE analysis to reproduce the post-heat treatment temperature, (2) 3D thermo-elasto-plastic FE analysis to assess the reduction in residual stress and changes in deformation, and (3) 3D fatigue analysis to investigate the resulting effects on fatigue life. The findings provide insight into optimizing PWHT parameters for improving the fatigue performance of welded steel structures.