Micromechanical damage simulation to obtain effect of coarse grains distribution on mechanical properties of bimodal AL using 2D XFEM

摘要

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. 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, XFEM is implemented for bimodal materials considering various fracture criteria for brittle and ductile phases in maximum traction and cohesive law. Then the stress-strain behavior dependency of the model on the CG distribution in a constant volume fraction is investigated by extraction of RVEs from optical microscopy (OM) images of the real material. The solution convergence of such a problem with irregular geometry, plasticity and crack initiation-propagation demanded extreme efforts that accomplished by refining and arranging meshes as well as 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 calculated. It is shown that the predicted results are in good agreement with the available experimental results.