Fatigue Life Estimation of Steel Welded Joints Under Multiaxial Constant and Variable Amplitude Loadings Including Partial Weld Penetration and Start/Stops

ABSTRACT In many weldment applications, fatigue failures occur under multiaxial cyclic loadings. The current literature on multiaxial fatigue life prediction of welded joints is largely centered on weld toe failures considering simplified weld geometry and under constant amplitude loading conditions. The focus of this work is on application of crack initiation‐based fatigue life estimation approaches to steel welded joints with partial weld penetration and preserved start/stop regions as realistic conditions in practice yet rarely studied. The experimental dataset used for validation includes single‐ and multi‐channel axial and torsional load types with and without mean stress and phase shift effects under constant and variable amplitude conditions. Fatigue life estimation methods used include nominal stress, local strain, and critical plane approaches. To account for the notch stress concentration and gradient effects of the welded joint hotspot, the theory of critical distance was employed. The critical plane approach resulted in the highest accuracy, robustness, and conservatism of life predictions for the loading conditions considered with reasonable estimations of micro‐crack plane orientations in the welded joints.