A Study On Mechanism Of Nano-cutting Monocrystal Material

Single-point Diamond Cutting is one kind of Ultraprecision machining technology and can produce high-quality surfaces in terms of form accuracy, surface finish, and surface integrity for precision components. When the undeformed chip thickness is down to several atoms, plastic removing can be realized for the brittle material during the machining process. It is difficult to explain the mechanism of the nanoscale cutting using the traditional cutting theory. Molecular dynamics (MD) analysis at the nanometric scale has been found to be a powerful tool for understanding the deformation mechanisms of materials.MD simulation and experimental verification of nonometric scale cutting will be conducted in this dissertation.. 3D MD simulation model was established based on the MD theory and the measured radius of the Single-point diamond tool. The following is the research based on the monocrystilline material nanoscale cutting.In simulating the nanocutting process, various boundary conditions of the workpiece modeling can be applied. The influence of these workpiece boundary conditions to cutting results is systematically studied, including the boundary conditions of only bottom, bottom and cut-in side, bottom and cut-out side, and bottom and both side and full scale WBC or not. The results of the simulation confirm that the boundary condition of bottom and closed cut-out side is best suited to the nanometric cutting process. The parameter of Tersoff potential is also discussed.In the nanocutting process, including excluding and shearing of the material removing mode. This paper researched that the material removing mode for the different rake angles and cutting radius.A cutting tool with a 3D shape in the MD simulation can be established. By analyzing the chip forming and the forming position, the results of MD simulation are close to the real cutting process. There exist two different stages of the material removal: only elastic deformation and plastic deformation. It is the critical value of the undeformed chip thickness 0.314nm between the elastic deformation and the plastic removal during the brittle material nanocutting process. When the undeformed chip thickness is 40nm, the chip is amorphous and monocrystalline by the TEM observation. It can be gained that the lattice deformation is less than 40nm in the nanocutting process.The cutting tool of the radius 10nm is made by using the FIB successfully. During the MD simulation cutting, 0.512nm is the critical value of the undeformed chip thickness between the elastic deformation and the plastic removal. And make a monocrystalline copper experiment. The copper crystal lattice is amorphous on the edge, polycrystalline in the chip by observation using TEM.