A finite element analysis of sawing stress in fixed-abrasive wire saw slicing KDP crystal

Abstract

Potassium dihydrogen phosphate (KDP) crystal is the preferred nonlinear optical crystal used in pockels cell and frequency multiplier. Slicing machining is the first process for KDP crystal, which has an important effect on the yield rate. However, KDP crystal is easy to crack when sliced due to the maximum tensile stress. This paper presents the finite element analysis of sawing stress in fixed-abrasive wire saw slicing KDP crystal. The finite element model of wire sawing KDP crystal is found, and the sawing forces are analyzed and loaded to the cutting kerf that are simplified as the normal sawing pressure p contrary to the workpiece feed direction and the tangential sawing pressure q along the wire moving direction, based on the analysis of fixed-abrasive wire saw cutting mechanism. The dynamic distribution and variation rule of the sawing stress and the coupling of sawing stress with crystal initial internal stress have been analyzed when slicing the (001) crystal plane optical device, and the critical initial internal stress of the KDP crystal to avoid cracking in wire saw cutting is discussed. Numerical simulation results show that the sawing stress for cutting KDP crystal without initial internal stress is a low-stress machining way, but a larger tensile stress produces due to the initial stress gathering in the kerf coupled with the low sawing stress. A greater crystal initial internal stress can lead to the more intense concentration of sawing stress; it suggests that the initial internal stress inside the sawed KDP crystal should be less than 2.294 MPa. The research results help to further understand the sawing stress field distribution and change in the process of slicing KDP crystal.