Multiaxial fatigue life prediction model with relative stress gradient and size effect

Abstract To investigate the effects of notched root stress gradient and geometric size parameters on the fatigue performance of engineering components, a new multiaxial fatigue life prediction model is established. First, based on the energy‐critical plane method, the location of the dangerous plane is determined with the help of finite element (FE) analysis. Second, the sixth‐order multinomial stress function is used to study the stress/strain distribution state on the critical plane, and the relative stress gradient (RSG) function is used to find the stationary point to determine the RSG value and the magnitude of the fatigue damage zone boundary value. Specifically, for specimens with different notch types, the indexes to determine the high‐stress influence zone and the size influence factor are proposed. Finally, a multiaxial fatigue life prediction model considering RSG and size effect is established, and the compared results show that the new model has a high fatigue life prediction capability.