Observations and analysis of fretting fatigue crack initiation and propagation

Many factors, such as the amplitude of the cyclic load, the relative rigidity of components and the frictional condition, play important roles in the fretting fatigue process. This study has focused on the local singular stress field at the fatigue crack tip or at the contact edge where the initial crack occurs, based on the numerical analysis results with the use of finite element method (FEM) program ABAQUS. It is proposed that all the effect of test conditions can be contained by the local stress field, which would dominate the fatigue crack initiation and propagation. By comparing with the experimental results, it was found that the initial fatigue crack should occur at the point of maximum shear stress range near the contact edge, and would propagate in the direction of maximum tangential stress range. An analytical simulation of fretting fatigue crack propagation has been carried out. It was found that a fatigue crack was always under the mixed mode conditions, the fracture path could be estimated by the maximum tangential stress theory (Deltasigma(thetamax)), and the propagation curve could be characterized by the stress intensity factor range in this direction (DeltaK(sigmathetamax)).