Fatigue crack curvature under the weld toe in an offshore tubular joint

Experimental tests on offshore tubular joints show that fatigue cracks, as well as curving around the brace/chord intersection, curve under the weld toe as they propagate through the chord wall. However, when producing stress intensity factor solutions for tubular joints, this curvature is usually ignored due to modelling difficulties. In this paper, detailed numerical models of surface cracks in tubular T-joints are used to simulate experimental observations of crack curvature reported in the literature. When compared with the experimental observations, the numerical results help to clarify the mechanism behind crack curvature. Based on the principal stress criterion, an approximate method for predicting crack curvature is proposed.