A Nonlinear‐Coupled Generalized Strain Energy Model With Dynamic Mean Shear Stress Sensitivity for Biaxial Fatigue Life Prediction

ABSTRACT

This paper proposes an improved generalized strain energy damage parameter model based on the critical plane method to predict fatigue life under biaxial loading conditions. The model comprehensively characterizes the energy dissipation mechanisms during crack initiation and propagation by nonlinearly coupling shear strain energy with normal strain energy. The model systematically characterizes the effects of mean stress and nonproportional hardening by incorporating the maximum normal stress and absolute shear mean stress terms. Furthermore, the paper establishes a dynamic mean shear stress sensitivity coefficient, enabling adaptive reflection of material‐specific responses to mean shear stress without requiring predefined weighting parameters. Independent of additional material constants, the model is applicable to uniaxial, proportional, and nonproportional biaxial loading paths. The model is validated using 187 sets of experimental data from six materials under 19 loading paths, primarily focusing on typical biaxial scenarios. Results demonstrate excellent predictive accuracy of the proposed model across diverse loading conditions: 88.5%, 94.6%, and 97.2% of predictions fall within the life factor of three for uniaxial loading, proportional, and nonproportional biaxial tension–torsion conditions, respectively.