A Critical Plane-energy Model for Multiaxial Fatigue Life Prediction of Homogeneous and Heterogeneous Materials

A new critical plane-energy model is proposed in this paper for multiaxial fatigue life prediction of metals. A brief review of existing methods, especially on the critical plane-based and energy-based methods, is given first. Special focus is on the Liu–Mahadevan critical plane approach, which has been shown to work for both brittle and ductile metals. One potential drawback of the Liu–Mahadevan model is that it needs an empirical calibration parameter for non-proportional multiaxial loadings because only the strain terms are used and the out-of-phase hardening cannot be explicitly considered. An energy-based model using the Liu–Mahadevan concept is proposed with the help of the Mroz–Garud plasticity model. Thus, the empirical calibration for non-proportional loading is not needed because the out-of-phase hardening is naturally included in the stress calculation. The model predictions are compared with experimental data from open literature, and the proposed model is shown to work for both proportional and non-proportional multiaxial loadings without the empirical calibration.