A Comparative Assessment of Local and Nonlocal Damage Models for Prediction of Fracture Behavior during Mixed-Mode Loading

For components made of ductile materials, finite element approaches which incorporate material damage con titutive models are able to predict the failure behaviour and the corresponding process with high accuracy. However, these local approaches suffer from the problem of mesh-dependency of the results. Problem arises when one needs to simulate large stress gradients and model miniaturized specimens with a pre-determined mesh-size. Nonlocal regularization of the material state variables can alleviate this problem and this has been investigated by various researchers over the years. Recently, the authors have developed a nonlocal form of the Rousselier's damage model and have used it to demonstrate that the results of the model are independent of mesh size. In this work, the issue of simulation of mixed-mode loading with the damage models will be discussed. The crack growth and the fracture resistance behavior of a standard compact tension specimen, loaded in mode-I and mixed mode, have been simulated with the use of local as well as the nonlocal damage models. In case of mixed mode loading, the calculation with the local model predicts a crack growth direction nearly parallel to the crack plane, which is not physical and it contradicts with experimental observation. This issue has been resolved with the help of the nonlocal formulation.