EFFECT OF LOCAL MATERIALS AND GEOMETRIES OF WELD JOINT ROOT ON FATIGUE CRACK INITIATION AND PROPAGATION LIFE

Abstract

In recent years, fatigue has become a major problem in infrastructures, and many failure cases have been reported. Above all, the cracks initiated from weld joint root are difficult to detect visually from the surface of the weld bead, so it is important to clarify the factors governing the fatigue performance and to make an evaluation method with high accuracy. In this study, we investigated the various factors that affect fatigue damage starting from the weld joint root by numerical analysis. In particular, the local behavior of the root was analyzed by nonlinear FEM analysis and X-FEM analysis based on linear fracture mechanics, and crack intiation life and propagation life were discussed. As a result, it was found that the fatigue crack propagation process dominates the fatigue damage of the weld root where the stress concentration factor is high, and the influence by the local material property and the root gap is small. On the other hand, the effect of angular distortion correction on the fatigue life is large, and the result that the fatigue life extension effect is suggested by the additional process of introducing compressive stress at the weld root was obtained.