Modeling and simulation on the effect of tool rake angle in diamond turning of KDP crystal

In this work, to investigate the effect of tool rake angle in diamond turning of KDP crystal, a novel theoretical model that considers the material properties, tool geometries, cutting parameters and the suppression of hydrostatic pressure is established by formulating the relative length of crack (RLC). Subsequently, interrupted-cutting experiments with different tool rake angles are performed, and an effective method for crack evaluation is used to acquire the experimental results of RLC. Moreover, using the inverse analysis for material model parameters by nanoindentation test and dimensional analysis method, a novel 3D hybrid model with the use of smoothed particle hydrodynamics and finite element method is constructed to simulate the diamond turning process of KDP crystal. As expected, the dynamic distribution of hydrostatic pressure ahead of the active cutting edge is successively investigated to reveal the underlying mechanism of tool rake angle, which is a significant factor that affects crack propagation, surface generation and chip formation. The results show that the developed theoretical model which considers the suppression of hydrostatic pressure has a satisfactory accuracy in predicting the quantitative relationship between tool rake angle and crack propagation. Large negative rake angles from −25° to −45° are suggested for the diamond turning process of KDP crystal.