Fatigue analysis of welded joints with the aid of real three-dimensional weld toe geometry

Fatigue analysis of welded joints usually assumes weld toes of ‘mathematically perfect’ geometry for the required weld toe stress state. However, the weld toe geometry certainly cannot be defined by simple mathematical functions. In the current study, the three-dimensional laser scanning technology was used to preserve the real geometry of welded specimens. Finite element models of the specimens were then constructed with the scanned results. The weld toe regions were carefully arranged so that the geometrical features of weld toes were captured in the models. Linear elastic finite element analyses were then carried out to estimate the stress concentration factors along the weld direction of each specimen. Subsequently, the low-high block loading fatigue tests were performed on the specimens. The beachmark sets left on the specimen fracture surfaces, which can be used as a guide for the location of early- to mid-stage cracks, were examined. The location of weld toes under plastic deformation was also determined from the calculated stress concentration factors. When the beachmark location of cracks was compared to the location of yielded weld toes, it was found that the locations were highly correlated. These results illustrate a possibility of predicting the morphology of fracture surfaces or the evolution of crack shape of welded joints with the aid of the real three-dimensional weld toe geometry.