Multiaxial fatigue life assessment of welded joints using the super ellipse criterion under consideration of support effects

• Accurate fatigue life prediction of welded joints under multiaxial loading. • Fatigue life assessment independent of the weld geometry with a unified approach. • Evaluation of the super ellipse criterion with design SN curves and extensive data. • Presentation of a standardized and easy-to-use assessment procedure. • Evaluation of effective stress concepts based on uni- and multiaxial loading. The super ellipse criterion has recently been developed as an easy-to-use method reliably predicting multiaxial fatigue life of welded joints based on experimentally determined S-N curves. This paper evaluates the application of the super ellipse criterion using design S-N curves on the basis of so-called effective stresses. In contrast to the established stress concepts such as the nominal, the structural, or the notch stress concept, effective stresses incorporate both the local weld geometry and the support effect of the material surrounding the failure critical weld notch allowing fatigue assessment using S-N curves independent of the weld geometry, such as the weld toe or the weld root. Based on a comprehensive database of welded steel joints under multiaxial loading, the super ellipse criterion is found to accurately and precisely predict multiaxial fatigue life using effective normal and effective shear stresses derived by the critical distance or the stress averaging approach, achieving root mean square logarithmic errors of 0.36 and 0.35. Moreover, the assessment procedure is unified by providing parameters for deriving effective stresses for different stress components and plate thicknesses.