A new path-dependent fatigue damage model for non-proportional multi-axial loading

• Presented a Moment of Load Path model for computing non-proportional fatigue damage.
• Provided an interpretation as a form of strain energy densities in stress plane.
• Validated by correlating a large amount of test data in both LCF and HCF regimes.

This paper presents a new path-dependent multi-axial fatigue damage model which is formulated based on an incremental form of Moment of Load Path (MLP) on either σ-βτ stress plane or ε-βεγ strain plane. The resulting MLP-based fatigue damage parameter can be shown to be related to an integral form of strain energy densities contributed by normal and shear deformation and each weighted by a path-dependent function. Then, the MLP-based damage parameter in terms of either equivalent stress range or strain range, in conjunction with path-dependent maximum-range cycle counting procedure (Dong et al., 2010; Wei and Dong, 2010), has been shown effective in correlating a large amount of test data obtained under non-proportional multi-axial loading conditions both for welded joints under stress-controlled conditions in high cycle fatigue regime and non-welded components under strain-controlled conditions in low-cycle regime.