A model of cleavage crack propagation in a BCC polycrystalline solid based on the extended finite element method

The first 3D model to simulate cleavage crack propagation in a body center cubic (BCC) polycrystalline solid is presented. The model was developed based on the extended finite element method (XFEM). Crack shape as well as a polycrystal were modeled independently from the finite element mesh. Cleavage crack planes formed on the (100) planes based on the local fracture stress criterion. Crack propagation was simulated by an iterative calculation with updating cleavage planes. Model validations were conducted with experimental fractography using a ferrite-pearlite steel. The results showed that the proposed model successfully simulated complicated cleavage crack propagation behavior, including the wraparound behavior noted in local crack propagation direction as well as the formation of numerous micro-cracks under the main fracture surface. In particular, the comparison of the distribution of the cleavage plane directions quantitatively validated the proposed model. The proposed model in the present study showed potential to help clarify the relationship between microstructure and cleavage crack propagation resistance. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.