Molecular Dynamic Study On Ultra-precision Cutting On The Surface Of Monocrystalline Silicon

Because of the accuracy of ultra-precision machining has reached a very high level,in the cutting process,sometimes the cutting depth is a few atom layers or some atoms, so nano processing mode of material removal is a discrete process of atoms.This has the very big difference with the traditional machining.If it continues to use the old cutting theory to explain and analysis,it will be very inappropriate.Limited by the processing conditions and cost,it is too difficult to carry out experimental study on it in the actual environment.Therefore, It need to use computer and molecular simulation methods for the machining process, so as to analyze the mechanism of the nano machining process.In the process of machining,it simulates monocrystalline silicon cutting with diamond cutting tool by molecular dynamics.With the help of choosing the potential function reasonably,it establishes the 3D simulation model,and from the instantaneous image of processing,atomic potential energy and cutting force, analyzes the machining mechanism: With the tip cutting, atoms on the silicon surface are extruded and sheared,atomic bond are broken.These atoms extend continuously with the push of tool.A part of deformed atoms recombine with cracked bond and form the machined surface.The rest of deformed atoms pile up in front of cutting tool and become chip.In order to further understand the process,it also investigates on the process under different cutting parameters by molecular dynamics simulation and the results show that:with the increase of cutting depth,the cutting force increases and the surface roughness will also become large.The increasing of cutting speed will cause that the cutting force has dramatic changes in a short period of time,but the effect on surface roughness is not obvious. Appropriate negative rake is good for improving the surface quality of the workpiece.Because spherical and conical tools have negative rake angle,so the surface quality of the workpiece that they process is better than rectangular and diamond cutting tool processing.