Abstract：For multiaxial conditions, the local stress-strain history at the notch danger point is used to predict the fatigue life in the local stress-strain method (LSSM), but this method does not take into account the influence of the non-proportional additional hardening and the stress gradient effect on the fatigue damage. Based on the analysis of shear stress and normal stress distribution on the crack initiation plane (critical plane), a mathematical calculation method is proposed to calculate the fatigue damage affected area of multiaxial notched specimen, and a life prediction model is established considering shear/normal stress gradient and non-proportional additional strengthening effect. Firstly, based on the energy method and the critical plane theory, the material plane with the largest strain energy density is defined as the critical plane by using the coordinate transformation principle, and the energy-critical plane method is established to determine the direction of crack initiation. Secondly, taking a specific path on the critical plane as the integral direction, the three-dimensional problem of notched specimen is transformed into a linear problem to simplify the calculation process. Then, the contribution of peak stress and equivalent stress field strength to multiaxial fatigue life is considered comprehensively, and the damage parameter representing the fatigue damage evolution process of multiaxial notched specimen is established. Finally, the feasibility and accuracy of the proposed model are verified by multiaxial fatigue tests of and TC4 alloy, and compared with LSSM model, FS model, SWT model.
2023, Vol. 44 
