Analysis on the fatigue damage evolution of notched specimens with consideration of cyclic plasticity

This paper presents a damage mechanics method applied successfully to assess fatigue life of notched specimens with plastic deformation at the notch tip. A damage-coupled elasto-plastic constitutive model is employed in which nonlinear kinematic hardening is considered. The accumulated damage is described by a stress-based damage model and a plastic strain-based damage model, which depend on the cyclic stress and accumulated plastic strain, respectively. A three-dimensional finite element implementation of these models is developed to predict the crack initiation life of notched specimens. Two cases, a notched plate under tension-compression loadings and an SAE notched shaft under bending-torsion loadings including non-proportional loadings, are studied and the predicted results are compared with experimental data.