FATIGUE ANALYSIS OF WELDED JOINTS BASED ON NOTCH STRESS METHOD

The notch stress method (NSM) is a local method of welding fatigue analysis, which has attracted much attention in recent years. Traditionally, the nominal stresses in welded structures are difficult to determine and the weld root stress cannot be defined, but NSM can not only successfully overcome these problems but also assess the effects of welded joint fatigue strength with local welding post-processing. In this paper, 3D notch stress models of typical welded joints are presented to solve the notch stress concentration factors (nSCF) in a weld toe. Some fatigue test data from butt joints and longitudinal fillet joints are referenced from literature, which include two conditions:As-weld and ultrasonic peening treatment (UPT); then unified S-N curves under notch stress system are obtained by combining the nSCF and fatigue data. Compared to the referenced fatigue-life curve of International Institute of Welding (ⅡW:m=3, FAT=225) at the same survival probability, it shows that these fitting curves have higher fatigue classes and shallower slopes.