Indentation Experiment And Finite Element Simulation Research On KDP Crystal

As a excellent nonlinear optics crystal, The Potassium Dihydrogen Phosphate(KDP) crystal is used in laser and nonlinear optics field, but KDP crystal is a kind of gentle-brittle material, and its machining is difficult, so machining of KDP crystal is the limit of ICF technology. Its intensity anisotropy in mechanical and physical property gives the machining plenty of inconvenience. So, it is important to research the regularity of anisotropy and mechanical property of KDP crystal to ultra-precision machining.Firstly, several groups of nano indentation experiment are conducted to KDP crystal,and the elasticity modulus and hardness value of different crystal planes and different orientation of KDP crystal are obtained. The experiment result indicate the intensity anisotropy on mechanical character of KDP crystal. By the use of ABAQUS software, the indentation 3 dimension finite element simulation model of KDP crystal is constructed. The stress variation of KDP crystal indentation experiments in loading and unloading process is concluded and the relation between the load and displacement of KDP crystal was calculated .Through fitting the load-displacement curve of finite element simulation and the experiments, a yield stress and stress-strain curve of different crystal and different orientation of KDP crystal are obtained.Secondly, Vickers indentation experiments are done on the different orientation of KDP crystal to research the variable rules of Vickers hardness. Through measuring the size of crack, the fracture toughness of different crystal and different orientation of KDP crystal are obtained. The crack-initiation threshold of middle crack was calculated. The variation rules of critical cutting thickness on the different crystal and different orientation of KDP crystal are obtained by theoretic calculate. Through the research of the rules of hardness, fracture toughness and critical cutting thickness on different orientation, the best cutting orientation of different planes are obtained. 90°orientation is the best cutting orientation of (001) crystal plane, and 45°orientation is the best cutting orientation ofⅡplane.