Multiaxial fatigue life prediction based on a simplified energy-based model

Thanks to the reliable correlation with experimental data, conventional energy-based models are widely employed in multiaxial fatigue life prediction of structural components, by combining energy-based variables with reference life curves. However, in practical applications, additional calibration factors and incremental plasticity theories are usually indispensable to characterize fatigue damage along multiaxial loading paths, whose procedures are usually rather complicated and time-consuming. In this paper, a simplified energy-based model, as an alternative to the incremental plasticity-based model, is proposed to predict the fatigue life under multiaxial loading. Being different from conventional models, the proposed model is based on a series of multiaxial energy-life curves, which avoids the introduction of additional calibration factors. Particularly, to eliminate the model's dependence on incremental plasticity theory, the effect of loading paths is captured by a loading path-dependent factor which is derived from the non-proportionality factor and the Moment of Inertia method. The availability of the proposed model is validated by reasonable correlations with experimental data of four kinds of materials under diverse loading paths.