A Crystal Plasticity-Based Model for Orthogonal Machining Mechanics of Single-Crystal Materials

Microstructural anisotropy caused by single crystal orientation, or by thermal gradients in casting and additive manufacturing processes pose significant direction-dependency in the machining behavior of materials. Effect of crystal orientation on the machining mechanics has not been fully explored yet. This study introduces a phenomenological crystal plasticity model to predict the cutting forces in orthogonal machining of single crystals, addressing the unique challenge of crystal orientation induced anisotropy. The proposed model incorporates temperature, strain rate, and strain hardening effects by adapting the Johnson-Cook constitutive law and integrating it into the crystal plasticity framework for accurate simulation of the machining mechanics. The model evaluates the shear angle, cutting forces, and the specific cutting pressures in two orthogonal directions by minimizing the cutting energy for any machining conditions such as uncut chip thickness, cutting speed, tool geometry, and friction coefficient. Comparison of the predicted cutting force coefficients with the experimental results on single-crystal copper demonstrates that the proposed model can accurately predict the specific cutting pressures and the impact of crystallographic orientation on the orthogonal machining mechanics. The introduced model offers a computationally efficient approach to better understand the deformation behavior in single-crystal machining and provides a basis for further extension to polycrystalline materials and milling operations.