Predicting the influence of overload and loading mode on fatigue crack growth: A numerical approach using irreversible cohesive elements

This paper describes an irreversible cohesive zone model to simulate fatigue crack growth. The model includes a three-dimensional (3-D) cohesive law that follows a distinct loading/unloading path and a damage evolution mechanism that reflects a gradual degradation of cohesive properties of the material under the influence of cyclic loading. To overcome convergence difficulties arising from nonlinearity of the cohesive zone model, the stabilization technique and the viscous regularization of the constitutive law are employed. For high-cycle fatigue applications, a damage extrapolation scheme is adopted to reduce computational cost. The irreversible cohesive zone model is implemented in the finite element software ABAQUS through a user defined subroutine and is used to predict fatigue crack growth in a compact-tension-shear (CTS) specimen with an emphasis on the extrinsic influence of overload for different loading modes. The numerical results show good agreement with experimental records documented in the open literature and capture the essential features of fatigue crack growth for various loading conditions. This indicates that the irreversible cohesive zone model can serve both as an accurate and efficient tool for the prediction of fatigue crack growth.