Molecular Dynamics Simulation Of The Surface Quality Of Metal Cerium Single-point Diamond Cutting

As an important rare earth material,cerium has been widely used in many fields of industry for its high practical value and research significance.For instance,corrosion resistance is one of the most important factors for improving the performance in the operation,transportation and storage of cerium.Machined surface quality has an important influence on the corrosion resistance of workpiece such as reducing surface roughness or increasing compressive residual stress can effectively improve the corrosion resistance of workpiece.Therefore,it is of significant importance to obtain the ultra-smooth surface of cerium under the ultra-precision diamond cutting,aiming for enhancing the surface corrosion resistance of cerium.In this paper,molecular dynamics simulation according preliminary experimental study of diamond cutting of cerium are carried out to study the quality of machined surface in terms of residual stress and surface roughness.The main results are outlined as follows:(1)The molecular dynamics model of cerium under diamond cutting is established.According to the physical and chemical characteristics of cerium,we establish the atomic structures of single crystalline cerium,polycrystalline cerium and diamond cutting tool The appropriate potential energy functions,boundary conditions,and simulation ensemble are selected for the simulated system.Different transient structures in the cutting process are extracted by employing crystalline defect analysis techniques.Furthermore,algorithms for quantitatively characterize surface roughness,residual stress and mechanical properties in simulations are developed.(2)Molecular dynamics simulation results demonstrates that the formation mechanisms of residual stress and roughness of cerium include the dislocation activity of the plastic deformation and lattice rotation in the cutting process.Based on the fundamental understanding of the formation mechanisms of surface residual stress and surface roughness of cerium under diamond cutting,the influence of different processing parameters on the surface quality of single crystalline cerium and polycrystaline cerium is investigated,including the influence of the tool rake angle,the crystal orientation,grain size of polycrystalline cerium and the depth of cut.Consequently,optimum machining parameters for achieving high machined surface quality of cerium by diamond cutting are derived.(3)Finally,experimental study of cerium under the ultra-precision diamond cutting is carried out,and machined surfaces are characterized by profilometer,white-light interferometer,triboIndenter.The influence of three machining parameters,i.e.,depth of cut,cutting speed and feed rate,on the cutting processes are studied.It is found that the surface roughness of cerium increases with the depth of cut and the cutting speed.With the increase of feed rate,the surface roughness decreases first and then increases.The experimental results are in good agreement with the molecular dynamic simulation results.