Simulation research on the anisotropic cutting mechanism of KDP crystal using a new constitutive model

Potassium dihydrogen phosphate (KDP) exhibits anisotropic and hydrostatic pressure-dependent mechanical characteristics during processing. However, none of the existed material models is capable of describing the mechanical properties of the crystal. Thus, a new constitutive model, which combines the anisotropic elastic and pressure-dependent plastic model has been proposed in this paper. In addition, the tensile stress failure criterion is adopted as the fracture criterion of KDP crystal. Subroutine of the new material model is programmed and integrated into the commercial finite element software LS-DYNA. On the basis of that, the unknown material parameters of KDP are successfully identified with the aid of the nanoindentation/scratch technique and finite-element simulation. Finally, 2-D and 3-D cutting simulations applying the new model are performed to investigate the influence of cutting parameters on the brittle ductile transition depth and cutting force. The simulation results show good agreement with the KDP cutting experiment results, which confirm the validity and capability of the proposed constitutive model.