Simulation of micromechanical damage to obtain mechanical properties of bimodal Al using XFEM

• We model microcrack in microscale simulation of a bimodal Al by using XFEM.
• Predicting the stress–strain behavior from elastic–plastic analyses with fracture.
• The results obtained shown that the CG distribution effects are not significant.
• Grain boundaries are responsible for crack initiation and avoiding crack propagation.

In this paper, we focus on the stress–strain behavior prediction of the bimodal bulk Al5083 series which are comprised of Ultra-Fine Grains (UFG) separated by Coarse Grain (CG) regions. This material is selected due to the availability of the required data in the literature. The CGs in the UFG matrix effectively prevents microcracks from propagation, leading to enhance ductility and toughness while the strength remains high. In this work, initially the dependency of stress–strain behavior of the model on the CG distribution in constant volume fraction is investigated by extraction of RVEs from optical microscopy (OM) images of the real material. Then, XFEM is implemented for bimodal materials considering various fracture criteria for brittle and ductile phases in maximum traction and cohesive law. The solution convergence of such a problem with irregular geometry, plasticity and crack initiation–propagation without any defined pre-cracks demanded extreme effort that accomplished by refining and arranging meshes and adding damage stabilizations. As a result of the above procedures, the sensitivity of the modeling procedure to various RVEs is obtained, the crack initiation–propagation pattern in microscale is predicted and consequently, the global stress–strain behavior result is obtained. It is shown that the predicted results are in good agreement with the available experimental results.