The Nano-cutting Mechanism Research Of Single Crystal Germanium Based On Molecular Dynamics

With the wide application of hard and brittle materials such as single crystal germanium in optical manufacturing,aerospace and other high-tech fields,the requirement of product accuracy has reached nanometer level,which puts forward higher requirements for ultra-precision processing in manufacturing industry.Material in actual processing generally contains defects,such as vacancies and dislocations.Enterprises often rely on experience to complete manufacturing and processing of materials.There is a lack of corresponding theoretical and experimental data analysis in nano-cutting of single crystal germanium materials containing defects.From the point of view of brittleplastic transition of hard and brittle materials,aiming at the cutting process of single crystal germanium with vacancies and dislocations,the molecular dynamics simulation model of nano-cutting of single crystal germanium with vacancies and dislocations is constructed by using molecular dynamics software,and the stable system state is obtained by relaxing the system.The change of system potential energy in cutting process is considered from the atomic point of view.The change of cutting force explains the material removal process and the formation mechanism of chip,and analyses the influence of vacancy and dislocation defects on cutting.The results show that the more vacancies in single crystal germanium crystals,the greater the potential energy of the basic system.With the progress of cutting,the potential energy of the system increases gradually,indicating that the increase of vacancy defects will lead to the increase of instability of the system.The cutting force required for the crystal plane of single crystal germanium material(111)containing vacancy defects is the smallest,and the chip is the most coherent,which is the most suitable for cutting.The crystal plane.In the cutting process of single crystal germanium materials containing edge dislocations,it is found that the slip and damage of dislocation structure will release the stored strain energy,which will cause the fluctuation of system potential energy.The existence of edge dislocations will hinder the cutting process,and the cutting force will fluctuate greatly in the dislocation part,showing an upward trend.The greater the cutting depth,the greater the average cutting force required.In order to compare the accuracy and feasibility of the simulation,experimental verification is made.Firstly,the dislocation etching pit morphology of single crystal germanium material is obtained by corrosion method and metallographic microscope observation.The influencing factors of dislocation etching pit morphology are analyzed and the dislocation density is calculated.After that,nano-scratch experiments were carried out on the surface of materials which had been observed by dislocation corrosion.The influence of dislocation density on cutting characteristics was analyzed with the observation of nano-scratch instrument under microscope,and the influence of cutting depth on surface cutting characteristics under different loads was also studied.The results show that the dislocation will affect the cutting process.It is found that when the probe passes through the area with high dislocation density,the dislocation will hinder the cutting process and the fluctuation of cutting force will increase.The cutting force of the probe is stable when it passes through a region with low dislocation density or without dislocation.At the same time,the conclusion is verified that the larger the cutting depth is,the larger the cutting force is.