Study on Effect of Nonlinear Distribution Stress on Surface Crack Growth at Thick Welded Joints Using Finite Element Analysis

摘要

The local stress increase near the weld toe of welded joints can be subdivided into membrane stress, shell bending stress and the nonlinear distribution stress (NDS) caused by the weld itself. The NDS is often ignored in the stress intensity factor (SIF) estimation of a surface crack at the weld toe, because the influence area of the NDS is very small. However, for thick welded joints, the influence area of the NDS becomes so large that the propagation of small surface cracks will be highly affected. The purpose of this paper is to investigate the effect of the NDS on the surface crack propagation at fillet welds, based on finite element (FE) analysis. A series of transversely loaded butt welds are selected as FE models, because stress increase at the toe of butt welds is just equal to the NDS. For simulating the crack growth at the fillet welds, geometric parameters of the butt welds are assumed to be similar to those of the fillet welds. Finite element model results show that the NDS not only increases the SIF of shallow surface cracks, but also changes the crack shape, which both obviously lead to the fatigue life reduction of welded joints.