【作者】 王阳；

【导师】 王敏杰；

【作者基本信息】 大连理工大学 ， 测试计量技术及仪器， 2021， 硕士

【摘要】 随着高速切削在机械制造领域的广泛应用,越来越多的难加工材料在切削过程中发生绝热剪切,由此导致的锯齿形切屑会影响工件材料的切削加工性,因此亟需通过建立切削过程中绝热剪切带的滑移线场模型来认识影响机理和规律。以此指导切削加工参数的合理选择,为生产实践服务,这对实现难加工材料零部件的高质高效加工具有重要的意义。本文针对切削过程中发生的绝热剪切,对绝热剪切带内材料的强烈塑性变形,进行了滑移线场研究,分析了基于绝热剪切行为的切削力和绝热剪切对于已加工表面质量的影响机理及规律。主要研究内容如下:(1)采用金相显微镜对正交切削FV520(B)硬化不锈钢获得的锯齿形切屑微观形貌和绝热剪切带进行了观察测量,获得了锯齿形切屑的变形系数和锯齿化程度以及绝热剪切带宽度和倾角随着切削速度、刀具前角和切削厚度的变化规律。(2)根据滑移线场理论,对于切削过程中绝热剪切带内的塑性变形,提出了一种四边界五区域滑移线场模型,并给出了相应的速矢图。定义了绝热剪切带滑移线场边界,将绝热剪切带滑移线场划分为五个区域。采用矩阵算子法确定了滑移线场模型的几何参量,给出了求解绝热剪切带内应力分布的方法。(3)基于绝热剪切带四边界五区域的滑移线场,给出了计算第一变形区内剪切力和法向力、作用在第二变形区的摩擦力和法向力以及主切削力和进给力的方法,分析了不同切削条件下FV520(B)不锈钢材料绝热剪切带内平均剪应变、平均剪应变率和平均温度。在此基础上,依据材料本构关系获得了绝热剪切带内平均剪切应力,计算分析了切削过程的主切削力和进给力,并通过正交切削实验对计算切削力的方法进行了验证。(4)计算分析了由绝热剪切带引起的导裂角随刀具前角、切削速度和切削厚度的变化规律。随着切削速度和刀具前角的减小、切削厚度的增加,刀尖处导裂角随之减小,已加工表面粗糙度Ra值增大。通过已加工表面几何形貌实验观察测量,印证了导裂角与已加工表面质量的相关性。更多还原

【Abstract】 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.更多还原