Numerical study on the effect of residual stresses on stress intensity factor and fatigue life for a surface-cracked T-butt welded joint using numerical influence function method

Fatigue crack propagation (FCP) is the most threatening failure to welded joints due to high local stress concentration and the effect of welding residual stress (WRS). Therefore, fatigue life assessment of welded joints considering residual stress distribution is an important procedure in designing and maintaining of welded structures. In this study, fatigue life of welded structures is evaluated using the fracture mechanics approach. The WRS is predicted by using the thermal elastic-plastic-finite element analysis (TEP-FEA). Stress intensity factors (SIFs) of surface-cracked welded joints under constant amplitude (CA) loadings are evaluated using the numerical Influence Function Method (IFM). The effects of WRS on the behavior of SIFs are discussed. Fatigue life estimations are calculated for CA loadings with different stress ranges using Paris-Elber law. Calculated fatigue life considering WRS is compared with those ignored WRS. The results show that the fatigue life of welded structure decreases significantly when the WRS is considered in the calculated SIFs. This study demonstrates the applicability of IFM-based SIF calculation system to the fatigue life estimation considering WRS. The proposed approach provides accurate solutions and an efficient calculation system for fatigue analysis under different loading conditions.