Multiaxial fatigue life prediction of notched components considering normal and shear energy gradient

Theory of critical distance (TCD) is a simple and reliable evaluation criterion. In view of the fact that the model based on energy parameters can take both stress and strain responses into account, the energy-based TCD is constructed. Meanwhile, the modified energy gradient is used to characterize the notch geometric feature effect, which integrates the notch effect and the geometric size effect. The normal/shear energy gradient is employed to correct normal/shear critical distance, and a novel approach for calculating equivalent strain energy density is presented. The critical plane gradient ratio is defined to depict the effect of shear energy and normal energy on fatigue damage. As to the analysis above, an energy-based TCD and prediction procedure of notched components are developed. The fatigue test of Q355(D) is carried out, and the existing test data of materials (En8 steel, En3B steel, C40 steel, TC4 alloy, 7050-T7451 alloy) are selected to verify the proposed model. The calculation results of the energy-TCD approach (point method and line method) are compared with other typical energy-based models (SWT model, MSWT model, Liu model, CXH model), and the proposed model obtained better precision.