Notch stress stress to assess multiaxial fatigue of complex welded structures under non-proportional loading

It has been verified that notch stress is effective for stress field and fatigue strength of complex engineering structures, which could consider the influence of welding geometry. However, due to the limitations of applicable conditions of criterion, the results of multiaxial fatigue assessment are not ideal, especially for multiaxial non-proportional loading. Therefore, based on the notch stress approach, several complex fatigue tests are extracted and re-analyzed in six common used multiaxial fatigue criteria. Correspondingly, the fitting notch stress S-N curves are described and analyzed statistically. It is found that the multiaxial non-proportional evaluation results are highly dispersive and unreliable. In order to obtain a more ideal evaluation result, the modified Findley criterion is renewed and re-evaluated based on the correction of stress ratio K-sigma and phase difference K-delta.