Study On The Generation Mechanism Of Surface Layer And Mechanical Characteristics In Nanomachining Of Polycrystalline Copper

Nanotechnology,as the focus of research in twenty-first Century,has been developing rapidly in recent years.How to apply the increasingly perfect nanotechnology theory to practical problems is still a difficult problem to be solved.The development of nanotechnology is limited by the functional structure and device fabrication of nanometer scale.Due to the lack of the basic theory of nanoscale machining,nanoscale machining technology,as an important means to obtain nanoscale structure,has not been further broken.Molecular dynamics simulation can be used to simulate the mechanical process at nanometer scale.It is an effective way to study nanomaterials mechanism besides nanoscale experiments.In this paper,the molecular dynamics method is used to simulate the process of nanoscale processing of polycrystalline copper materials.The mechanism of polycrystalline copper nanomachining is studied systematically.The cutting experiments of diamond cutting tools and nanoindentation experiments are carried out to verify the simulation results.Firstly,polycrystalline model is established based on the Poisson-Voronoi method.The polycrystalline model is further divided into four kinds of microstructures,which are grain cell,grain boundary,trible junction and vertex points,that can help us to observe the internal micro phenomenon of the material in the process of nanomachining from a more detailed point of view.Secondly,the simulation of nanoscratching for polycrystalline copper is constructed,and the microstructure evolution of the internal defects and the formation of the machined surface during the process of the probe are studied.The simulation results of single grain cell are extracted and analyzed.The process of nucleation expansion of dislocation and stress transfer in the grain is more clearly analyzed,which is helpful for further understanding of the mechanism of nanoscratching.Thirdly,MD simulation of nanomachining on polycrystalline copper is carried out.The influence of different cutting parameters on cutting force,surface quality and residual stress can be explored,which can guide the optimization of cutting parameters in actual processing.Finally,nanomachining experiments with different cutting parameters on polycrystalline copper workpiece are conducted.The surface roughness of the workpiece is measured.The influence of the cutting parameters on machining quality is analyzed,and molecular dynamics simulation work of this paper is verified by comparing with the experiments results.The surface of the machined workpiece is tested by the nano-indentation instrument,and the indentation force-indentation depth curve is obtained.The influence of the cutting parameters on the working hardening of the workpiece is analyzed.