Stress Intensity Factors For Subsurface Fatigue Crack Growth Under Contact Loading

Abstract

The paper describes a general computational model for simulation of subsurface fatigue crack growth in the contact area of mechanical elements. The model assumes that the initial crack develops along the slip line in a single crystal grain, where the maximum equivalent stress exceeds the local material strength. The position and magnitude of the maximum equivalent stress are determined with the Finite Element Analysis of the equivalent contact model, which is based on the Hertzian contact conditions with the addition of frictional forces. The Virtual Crack Extension method is then applied to the same model and used for simulation of the fatigue crack propagation from the initial to the critical crack length, when the surface material layer breaks away and pit appears on the surface. The pit shapes and relationships between the stress intensity factor and the crack length are determined for various combinations of contacting surface curvatures and contact loadings. The computational results prove that the model can reliable simulate the subsurface fatigue crack growth under contact loading and can be used for computational service life predictions of various contacting mechanical elements in regard to the surface pitting.