A Multiscale Framework for Predicting Fracture Toughness of Polycrystalline Metals

Abstract

Microstructure has a strong influence on fracture toughness of materials through the activation of different fracture mechanisms. To tailor the fracture resistance through microstructure design, it is important to establish relations between microstructure and fracture toughness. A multiscale computational framework based on the Cohesive Finite Element Method (CFEM) is introduced to facilitate relations between microstructure and the fracture toughness of ductile polycrystalline materials. This material design framework includes 3D image based microstructure reconstruction, 3D meshing, and finite element implementation. It allows the material fracture toughness to be predicted through explicit simulation of fracture processes involving arbitrary crack paths, crack tip microcracking, and branching. Cohesive elements are embedded both within the grains and along the grain boundaries to resolve the different material separation processes. The calculations carried out concern Ti-6Al-4V alloy and focused on the two primary fracture mechanisms which are correlated with microstructure characteristics, constituent properties, and deformation behaviors. The methodology is potentially useful for both the selection of materials and tailoring of microstructure to improve fracture resistance.

From micro to macro

“…An example of an MHCA model is the embedded cell approach (ECA). The ECA minimizes the boundary effects by using an ideally homogeneous buffer around the statistical computed window Li, McDowell, & Zhou 2013;Trias et al, 2006). In this way, the boundary effects may be decided before the scale transfer.…”