Study On Micro-cutting Process Of Pure Iron Through SPH Simulation And Experiment

Industrial pure iron is widely used in the fields of precision physics experiment,electronics,military and aerospace due to its excellent ductility,electromagnetism,electric and thermal conductivity.However,its low hardness and high plasticity lead to a lot of cutting heat,tumour of cuttings and stick knife in the process of machining,which greatly reduces the machining accuracy.Therefore,this paper introduces micro cutting technology to solve the problem of poor machinability of traditional cutting of industry pure iron,and the micro cutting mechanism is studied.Due to the slight machining scale,the existence of tool edge radius has a significant effect on chip formation,size effect and negative rake angle phenomenon.It is difficult to observe these micro phenomena only through micro-cutting experiments,so this paper introduces the SPH simulation method into the micro-cutting of industrial pure iron.Through the combination of simulation analysis and experiment,the micro cutting mechanism and surface quality of pure iron are studied.The SPH simulation model of micro-cutting pure iron with different tool edge radius is established,and the effect of edge radius on the critical cutting depth was studied.The results show that the edge radius has a major effect on chip formation and minimum cutting thickness.When the cutting depth is 0.16 times of the edge radius,the critical condition of continuous chip formation is reached.As the tool radius decreases,the minimum cutting thickness increases,and the formation of continuous chip is easier.At the same time,there is an obvious size effect in the micro-cutting process,the normal cutting force is greater than the tangential cutting force,and with the decrease of the tool edge radius,the smaller the fluctuation of the micro cutting force,the better the cutting stability.The micro-cutting process of pure iron with different cutting depths is simulated by SPH method.The chip formation,cutting force,surface stress distribution and the elastic-plastic deformation of machined surface are analyzed.It is found that the continuous chip formation is mainly determined by the proportional relationship between the cutting depth and the tool edge radius,and the minimum cutting thickness is equal to 0.16 times of the tool edge radius.When the cutting depth is less than the minimum cutting thickness,the cutting force decreases with the increase of the cutting depth,and the normal force is always greater than the tangential force.When cutting at the critical depth,the fluctuation of force and the elastic recovery of surface are both smallest.The closer the cutting depth is to the minimum cutting thickness,the smaller the elastic recovery of surface and the higher the surface flatness of workpiece.At the same time,the chae of stress gradient and the stress distribution region inside the workpiece are smaller under the minimum cutting thickness,so the influence on the subsurface hardness and residual stress of the machined surface is reduced,and the quality of the machined surface is improved.The chip morphology,micro cutting force,machined surface profile and surface roughness are measured by micro-cutting experiments with varying cutting depth of pure iron.When the cutting depth is less than 0.16 times of the tool edge radius,fragmentary chips can be obtained,and when the cutting depth is greater than 0.16 times of the tool edge radius,continuous chips can be formed.Under this critical cutting depth,the surface roughness is minimum and the flatness of surface profile is maximum,which is basically consistent with the simulation analysis results.At the same time,the cutting forces obtained by experiment and simulation are compared,and the changing trend is basically the same,which further verifies the simulation result is accurate and feasible.