Fracture Mechanics based Estimation of Fatigue Life of Welds

This paper presents a mechanism based approach for lifetime prediction of welded joints, subjected to a multiaxial non- proportional loading. Assuming the existence of crack-like flaws after the welding process, the stage of a fatigue crack initiation becomes insignificant and the threshold for the initial crack propagation can be taken as a criterion for very high cycle fatigue (VHCF) whereas crack growth analysis can be used for low and high cycle fatigue (LCF, HCF). The proposed deterministic method, which is based on the welding process simulation, thermophysical material modeling and fracture mechanics, considers the most important aspects for fatigue of welds. Applying worst case assumptions, fatigue limits derived by this method can be then used for the fatigue assessment of complex welded structures. The capability of the approach is validated by S-N curves provided at the Recommendations of the IIW.