Simulation And Experiment Of Ultra-precision Cutting Single Crystal Silicon

Single crystal silicon and other brittle materials are widely used in infrared ray optical components, micro-mechanical and other high-tech areas. As to the methods of processing the single crystal silicon, polishing after grinding were adopt nowadays.However, the single point diamond turning shows a huge advantage of causing less surface damage improving the efficiency and so on. Single crystal silicon belongs to hard and brittle materials, and the DBT(ductile to brittle transition) is the key to achieve ductile regime cutting and obtain the smooth surface. Although scholars have conducted many experiments and successfully achieved the ductile regime cutting, the problems of high cost of tests and the difficulty of explaining the complex process hinder the development of SPDT(single point diamond turning) of single crystal silicon. Single crystal silicon exists the property of anisotropy, so obtaining the cutting thickness of DBT in the whole surface of different directions plays the key role in obtaining uniformly smooth surface. In this paper, the values of DBT cutting thickness were obtained through combining with theoretical prediction, simulation analysis and fly-cutting tests, and the experiments of SPDT of single crystal silicon were conducted, as result of realizing the high-quality and uniformly smooth machined surface The research is of great significance for further understanding the SPDT of brittle materials.The basic mechanics parameters and the load-displacement curves were obtained through the nanoindentation tests in the surface of single crystal silicon. The cutting thickness judgment condition for ductile regime cutting was ensure through the analysis of maximum undeformed chip thickness model, the DBT cutting thickness and the minimum cutting thickness. And the trend of cutting forces and DBT cutting thickness were predicted in certain condition based on the cutting model built for brittle materials.Simulation model was established by FEA software and the influence of cutting parameters and the rake angle of tool on cutting process were discussed.Through the analysis of stress distribution, chip formation caused by the increasing of depth of cutting, the DBT thickness was obtained. The XFEM(extended finite element method)was adopt to analysis the crack generation in the process of cutting. The depth-changing cutting simulation model was built to simulate the DBT of single crystal silicon, and the range of DBT cutting thickness were obtained.The fly-cutting experiments were conducted on the ultra-precision turning-lathe so as to make sure the values of DBT cutting thickness and verify the correct of the simulation. Because of the anisotropic phenomena of cutting surface, tests in different directions were carried out and the anisotropy of DBT cutting thickness was summarized. Finally, after choosing the cutting parameters based on the model of maximum undeformed cutting thickness, experiments of SPDT of single crystal silicon were conducted and the high-quality uniformly smooth cutting surface was obtained successfully.