Slip Line Field Of Adiabatic Shear Band In Cutting Process

With the wide application of high-speed cutting in the field of machinery manufacturing,more and more difficult-to-machine materials undergo adiabatic shearing during the cutting process.The resulting serrated chips will affect the machinability of the workpiece material.Therefore,it is urgent to establish the slip line field model of the adiabatic shear band in the cutting process that is used to understand the influence mechanism and law.In order to guide the reasonable selection of cutting parameters and serve the production practice,this is of great significance for realizing high-quality and efficient machining of difficult-to-machine material parts.Aiming at the adiabatic shear that occurs in the cutting process,this paper studies the strong plastic deformation of the material in the adiabatic shear zone,studies the slip line field,and analyzes the mechanism and law of influence of the effect of the cutting force and adiabatic shear on the surface quality of the machined surface based on the adiabatic shear behavior.The main research contents are as follows:(1)Using a metallurgical microscope to observe and measure the micro morphology and adiabatic shear band of the sawtooth chips obtained by orthogonal cutting of FV520(B)hardened stainless steel,and obtain the deformation coefficient and the degree of serration of the sawtooth chips and the adiabatic shear,the cutting width and inclination angle change with the cutting speed,tool rake angle and cutting thickness.(2)According to the slip line field theory,for the plastic deformation in the adiabatic shear zone during the cutting process,a slip line field model with four boundaries and five regions is proposed,and the corresponding velocity vector diagram is given.The boundary of the adiabatic shear zone slip line field is defined,and the adiabatic shear zone slip line field is divided into five regions.The matrix operator method is used to determine the geometric parameters of the slip line field model,and a method to solve the stress distribution in the adiabatic shear zone is given.(3)Based on the slip line field of the four boundaries and five zones of the adiabatic shear zone,the method of calculating the shear and normal forces in the first deformation zone,the friction and normal forces acting on the second deformation zone,and the main cutting force and feed force is given.And the average shear strain,average shear strain rate and average temperature in the adiabatic shear zone of FV520(B)stainless steel under different cutting conditions is analyzed.On this basis,the average shear stress in the adiabatic shear zone is obtained according to the material constitutive relationship,the main cutting force and feed force in the cutting process are calculated and analyzed,and the method of calculating the cutting force is verified by orthogonal cutting experiments.(4)The law of crack conduction angle caused by the adiabatic shear zone with the tool rake angle,cutting speed and cutting thickness is calculated and analyzed.With the reduction of cutting speed and tool rake angle and the increase of cutting thickness,the leading angle at the tool tip decreases,and the surface roughness Ra value of the machined surface increases.Through the experimental observation and measurement of the processed surface geometry,the correlation between the lead angle and the quality of the processed surface is confirmed.