Analysis of crack propagation of annular butt weld and distribution of weld-induced residual stress

Abstract

The circumferential surface crack propagation and the effect of weld-induced residual stress were analyzed to comprehensively understand the mechanical behavior and fracture resistance of dissimilar girth welded joints of steel castings. The evaluation of stress intensity factors is conducted for circumferential cracks on internal surfaces, aiming to predict the fracture toughness of dissimilar welded joints. The distribution of weld-induced residual stress is obtained by thermal elastic-plastic finite element methods. The impact of residual stress on the propagation of cracks is investigated through the application of extended finite element theory. The high-stress intensity factors were found in such dissimilar welded joints due to the local bending and distortion caused by the asymmetrical weld geometry. The tensile residual stress and distortion were applied to the weld root area and its vicinity. Both the asymmetrical weld geometry and tensile residual stress contribute to the tensile distortion of the inner surface around the weld root, and enable the growth of internal surface cracks in the circumferential direction and radially from inside out of the welded joint. The fracture resistance decreases with the simultaneous influence of residual stress and welds’ asymmetry.