ON THE INFLUENCE OF SPECIMEN GEOMETRY, SIZE, LOADING AND BOUNDARY CONDITIONS ON FRACTURE RESISTANCE BEHAVIOR OF REACTOR GRADE STEELS USING NONLOCAL DAMAGE MODELS

摘要

For components made of ductile materials, finite element approaches which incorporate material damage constitutive 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. One way to avoid this problem is to use a fixed mesh size near the crack tip. This mesh size is usually related to the mean distance between the relevant inclusions and second phase particles in a material. However, problem arises when one needs to simulate large stress gradients and model miniaturized specimens, where the fixed mesh size is large enough for a converged solution. 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 version of the Rousselier's damage model and showed that the results of this model are mesh-independent. However, the ability of the model to predict the effect of specimen size, geometry, crack depth, loading and boundary conditions etc. on the load-displacement and fracture resistance behaviour has not been studied before in detail. In this work, we use the nonlocal Rousselier's model to investigate these effects on the response of two different types of fracture mechanics specimens. The differences between the results of local and nonlocal model were compared. It was shown that local damage models are not able to predict several of these effects including the important aspect of the use of symmetric boundary conditions in finite element analysis.