Crystal Orientation Effect on SIF in Single Crystals: A Study Based on Coupled Framework of XFEM and Crystal Plasticity Model

Abstract

A coupled framework of extended finite element method (XFEM) and crystal plasticity (CP) is proposed for investigating the effect of crystal orientation on Mode I stress intensity factor (SIF) in pre-cracked single crystals. While XFEM is used to evaluate the local displacement fields in front of the crack tip, CP provides anisotropic material response in front of the crack tip. Three different orientations of single crystal nickel with and without crack having Euler angles (0°, 0°, 0°), (30°, 0°, 0°) and (45°, 0°, 0°) are investigated using the proposed framework. The lattice orientation highly influences the activation of slip system, which consequently results in the change in cumulative plastic slip. Under the action of similar applied displacement loading, higher stresses are observed in (45°, 0°, 0°) oriented cracked and uncracked single nickel crystal followed by (30°, 0°, 0°) and (0°, 0°, 0°) lattice orientations. The proposed framework can be extended to study the short fatigue crack propagation in polycrystalline metals which is highly influenced by local microstructural features such as grain orientation, grain boundaries, phase difference and inclusions.