Fracture mechanics based approach to fatigue analysis of welded joints

Decades of operating experience related to welded T-joint connections in metallic structures have shown that fatigue cracks generally develop at welding due to both material heterogeneity (mismatch) and stress concentration. In the present paper, the fatigue behaviour of a metallic welded T-joint subjected to cyclic bending is analysed. A semi-elliptical surface crack is assumed to exist at the welding. The crack propagation is numerically examined by using the stress-intensity factor (SIF) values obtained from finite element analyses, and extensively presented in a recent work. Geometry and sizes of the welded T-joint are chosen in order to compare numerical results with experimental data available in literature, related to an actual welded joint of a common Francis turbine runner.