Study on the Estimation Method for Welding Fatigue Mean Stress Effect Independently from Failure Mode and Joint Type

Bending fatigue tests with stress ratio R = -1 and 0 of as welded (AW) relieved (SR) root-failed plug weld (PW) specimens toe-failed out-of-plane gusset (GW) T-joint (TJ) are performed. The welding residual (WRS) at the root notch toe AW SR measured by XRD method. mean effect test results analyzed using modified MIL-HDBK-5D equivalent σeq based on hot spot (HSS) 'root local (RLS)' determined two-points extrapolation. It is found that all can be approximated a single S-N curve regardless failure mode, joint type, external load treatment when RLS so HSS curve. As an alternative means for cases where HSS-based inapplicable, 'EPLSC method', in which from elastic-plastic cycle (EPLSC) calculated cyclic loading thermal elastic plastic FE analyses very fine mesh, proposed. PW GW various EPLSC considered proposed method effective large number root-failure cases.