矩阵算子法构建切削滑移线场的分析

刀具与切屑接触的摩擦因数呈不均匀分布增加了正交切削分析的难度,缺少一个完善的解析模型。针对于此,本文采用矩阵算子法构建了一种考虑在刀-屑接触面上变摩擦因数的滑移线场。通过Oxley的剪切切削理论找出工件表面材料塑性剪切变形的位置,为滑移线场的添加几何约束条件,从而求解滑移线参数。根据滑移线场,导出刀-屑接触长度,推算出切削力的解析式。模型计算结果与GH4169切削有限元仿真结果对比发现：刀-屑接触长度误差在9.8%内,两者的切削力在变化趋势上一致且数值上相近,验证了滑移线场的准确性。上述研究成果为变摩擦因数的正交切削分析刀-屑接触长度和切削力提供了理论方法。     

基于有限元法的硬质合金微槽车刀刀——屑接触摩擦模型研究

刀—屑接触界面的应力应变状态对金属切削过程尤其是刀具的摩擦磨损研究有着重要影响,摩擦模型是该区域应力应变的数学表达形式。本文基于有限元仿真平台,重点分析微槽车刀切削过程中刀—屑接触界面的摩擦状态,确定出刀—屑接触总长度和内外摩擦区各自的范围,对比分析了原车刀和微槽车刀的刀—屑接触界面摩擦状态,从而获得两车刀相应的摩擦模型。研究发现:微槽的置入使得刀—屑粘结摩擦区长度缩短,带来的直接影响便是第二变形区内的主要发热区缩小,进而发热量也相应减小。研究结果为金属切削过程刀—屑接触摩擦模型研究提供一定理论参考。     

基于正应力摩擦模型的金属切削有限元仿真

刀-屑摩擦模型是金属切削仿真的关键问题,采用基于前刀面正应力的摩擦系数模型能够真实反映刀-屑接触长度内的摩擦状况,通过仿真和试验证明,采用该模型可获得较好的仿真精度,而且通过降低工件材料的剪切流动应力能够较好地模拟切削液的润滑效果对切削过程的影响.     

织构刀-屑界面滑移区微通道特性数值研究

刀-屑界面滑移区的接触及微通道分布特性直接影响切削液的渗入和刀-屑界面摩擦,对金属切削过程有着重要的影响,针对滑移区接触及微通道分布特性测量难、切削液在刀-屑界面渗入不易量化等问题,建立微织构粗糙刀-屑界面滑移区的接触数值模型,分析滑移区的接触、微通道分布特性以及微织构作用机制。研究表明:滑移区存在3种不同的宏观接触特性,分别为近黏结特性、微通道特性和近分离特性;在近黏结特性区内,刀-屑界面不存在微通道,微织构主要功能为减少刀-屑界面接触面积;在微通道特性区内,刀-屑界面存在大量微通道,微织构主要功能为连接微通道;在近分离特性区内,刀-屑界面微通道消失,微织构主要功能为存储切削液。刀-屑界面应力分布系数对各特性区长度有影响,应力分布系数减小,近黏结区和微通道区长度增大,而近分离区长度相应减小。     

基于有限元法分析超精密切削中的摩擦问题

基于更新的拉格朗日公式,建立了热-机械耦合的平面应变大变形正交切削模型.根据此模型,对金刚石车削过程中的摩擦问题进行了仿真研究.对两种摩擦模型仿真所得的切削力与实验数据进行了比较,验证了前刀面上的摩擦状态应是粘结-滑移摩擦同时存在,并研究了刀具摩擦系数各向异性对超精密切削中切屑变形、切削力、剪切角的影响.     

铝合金高速铣削机理三维仿真建模与分析

为了研究铝合金7050-T7451高速铣削机理,建立了能反应实际铣削状态的斜角切削有限元模型.该模型采用双刃螺旋立铣刀进行模拟,模拟过程考虑刀具的进给运动和旋转运动,工件材料模型通过高温拉伸实验与高速压缩实验得到,刀-屑接触摩擦采用可自动识别滑动摩擦区和粘结摩擦区的修正库仑定律,切削温度模型等效为窄带热源.采用建立的有限元仿真模型模拟了铣削过程中的切屑成形状态,分析了应力、应变和温度分布情况以及铣削力值.研究结果表明,铝合金高速铣削加工形成连续带状切屑,最大应力发生在第一变形区,切屑形成时应变最大,最高温度出现在刀、屑接触部位,模拟得到的铣削力可以接受.     

45淬硬钢干式切削刀-屑接触区域温度场分布研究

针对45淬硬钢干切削过程,考虑刀-屑接触区域热流密度不均匀性和热分配率不均匀性等因素,基于热源法建立前刀面刀-屑接触区域三维温度场解析模型,并利用验证试验和解析模型,研究前刀面刀-屑接触区域温度场分布规律。结果表明:模型预测值与实验值相吻合,两者误差低于3.26%;且前刀面刀-屑接触区域温度场分布呈均匀梯度分布;最高温度位置出现在刀-屑接触界面粘结摩擦区域结束处附近,最高温度位置受切削速度影响较小;最低温度位置出现在刀-屑接触界面边缘处。该模型具有较高准确度,对研制新型刀具、降低刀具磨损、提高加工效率和加工质量具有重要指导意义。     

极端重载切削条件下的刀-屑粘结失效

以筒节材料2.25Cr-1Mo-0.25V钢切削试验为基础,研究极端重型切削过程中刀-屑粘结失效问题,为实际生产过程中避免刀具粘结失效提供理论依据。分析极端重型车削过程变载荷波动特性;在仿真分析和试验分析的基础上,进而研究波动温度和机械载荷对刀具表层强度的影响,进行刀-屑粘结失效分析;进行综合理论分析,确立极端重载切削条件下刀-屑粘结发生的理论判据,并结合试验测试数据进行验证分析;从技术手段和工艺参数优化方面,提出刀-屑粘结预防措施。研究结果表明,切削区域的波动热-机械耦合冲击是引起刀-屑粘结失效产生的主要因素,且粘结程度与刀具和工件材料接触区域的应力大小有关。     

基于热力耦合模型的金属切削过程有限元分析

基于有限元理论和热力耦合模型的研究,通过讨论切削过程中的关键技术,主要包括切削加工有限元方程的建立：构件材料的Johnson-Cook本构模型;切屑分离准则;材料断裂准则;接触摩擦模型;切削热的产生和分布;残余应力的分析和切削力的比较分析等,建立了二位金属切削过程模型,通过采用粘结．滑移摩擦模型,有效地模拟了航空钛合金的切削加工过程,对此类材料加工的切削力、切屑温度以及应力场和应变的分布进行了分析。     

刀具表面微织构对刀——屑界面特性的影响研究

刀—屑界面的剧烈摩擦和高温会导致刀具快速磨损和加工效率低下。微织构作为用于刀具表面改善刀—屑界面特性和提高金属切削性能的一种方法,经证明效果明显。目前,关于微织构对刀—屑界面特性的影响机理及量化关系的研究较少,刀具微织构技术发展缓慢。本文利用激光打标机在刀具表面加工出不同参数的微织构,通过金属切削试验和理论模型解析,得到微织构刀具对刀—屑界面摩擦特性、刀—屑接触长度和刀—屑界面应力场等的影响关系。研究结果表明:刀具表面微织构降低了刀—屑界面的摩擦系数,减小了刀—屑接触和粘结区长度,改变了切削刃处的正应力和刀具表面应力场,为刀具表面微织构的研究和设计提供理论参考。     

纳米切削过程中刀-屑接触区应力分布研究

高速切削时刀屑接触区的应力分布直接影响切削过程、切削温度及刀具磨损。利用分子动力学技术对纳米切削过程中刀屑接触区的应力分布特征进行研究,分别采用EAM势、Tersoff 势及Morse势计算单晶铜原子间、单晶硅原子间、工件原子与刀具原子间的相互作用力。分析纳米尺度下刀屑接触长度随切削距离变化的规律,探讨刀具前角对刀屑接触区应力分布的影响,通过描述刀屑接触区切屑原子的运动情况,为阐释刀屑接触区的应力分布特征提供依据。研究结果表明在刀-铜屑接触区,正应力在切削刃处最大,随着到切削刃距离的增大而减小,在刀-硅屑接触区,正应力以规则的波动形式逐渐减小。而切应力在切削刃处为负值,随着到切削刃距离的增大,切应力在刀屑接触长度的三分之二处增大到最大值后逐渐减小至零。     

基于黏结-滑移摩擦模型的304不锈钢切削力仿真研究*

通过预测加工304不锈钢时产生的切削力,从而对切削参数和刀具几何参数进行优化,是提高304不锈钢的加工精度、切屑控制及保障刀具寿命的基础。建立304不锈钢切削仿真模型,为提高模型的精确性,选择Johnson-Cook本构方程和黏结-滑移摩擦模型。结果表明：采用黏结-滑移摩擦模型的切削力预测结果更为准确,表明相对于纯剪切摩擦与库仑摩擦模型,黏结-滑移摩擦模型能更准确地描述刀-屑摩擦特性。展开不同参数下的切削力研究,研究发现：切削力随着刀具前角、后角和切削速度的增大而减小,随切削刃钝圆半径和切削厚度、宽度的增大而增大,其中切削宽度、厚度及前角对切削力大小影响较大。研究结果为304不锈钢切削效率的提高和切削机制的研究提供了理论依据。     

刀-屑接触区摩擦润滑的毛细管模型研究

切削时刀-屑接触区为边界摩擦状态,冷却润滑剂难以进入,其作用可用毛细管理论解释.在切削试验与理论分析的基础上,提出了圆锥形毛细管模型.动力学分析结果表明:冷却润滑剂的微粒尺寸越小,冷却润滑效果越好.刀-屑接触面的吸附作用能形成边界润滑膜,圆锥形毛细管能限制冷却润滑剂的渗透深度,负压力可为冷却润滑剂的渗透提供动力.     

Analysis of tool-chip interface characteristics of self-lubricating tools with nanotextures and WS<Subscript>2</Subscript>/Zr coatings in dry cutting

The environmental obligations of manufacturing industries have resulted in the development of new cutting tools during metal machining without cutting fluids. According to the green manufacturing principles and to further improve the cutting performance of tools in dry cutting, novel cutting tools combined with nanotextures and WS₂/Zr coatings (AN-AW) are developed, and cutting tests without cutting fluids on hardened steel exhibit that the AN-AW tool is the most effective in reducing the cutting forces compared with the WS₂/Zr-coated tool (AS-W) and conventional tool (AS). Based on the experiments and theoretical models, the tool-chip interface characteristics are further investigated quantitatively to analyze the mechanism of the AN-AW tool. Results show that the AN-AW tool has a significant effect on the tool-chip interface characteristics. The AN-AW tool is the most effective in reducing the friction coefficient and tool-chip contact length; meanwhile, it changes the stress distribution at the tool-chip interface. The reduced tool-chip contact length and sticking-total contact length ratio as well as the lubricant film formed by the WS₂/Zr coatings at the tool-chip interface may be responsible for the changes of friction and stress distribution for the AN-AW tool.     

金属切削过程有限元仿真关键技术及应考虑的若干问题

华侨大学摘要:有限元仿真是研究金属切削的一门有效而重要的技术。本文介绍在金属切削过程模拟中有限元仿真技术的应用和发展,深入分析和研究工件材料模型、自适应网格划分、切屑分离判别、刀—屑接触面摩擦模型以及刀—屑接触长度确定等五项关键技术;讨论了在实际金属切削过程有限元仿真中的真实性、可操作性、效率等方面应考虑的若干问题。     

Modeling chip formation with grooved tools

A slip-line field model for orthogonal cutting with a tool containing a groove-like feature on its rake face is proposed. Primary contact at the tool-chip interface is taken to be plastic. Based on experimental observations, it is assumed that the chip flows into the groove, and is forced to curl by Coulomb friction contact with the groove back wall. Solutions obtained for different groove geometries, groove positions relative to the cutting edge, rake angles and tool-chip interface friction using the matrix operator method are presented and discussed. The calculated results are in general agreement with experimental observations. It is found that the model can be formulated so that it can be used to predict the cutting geometry for obstruction-type chip breakers as well.     

Development and validation of a new friction model for cutting processes

The International Journal of Advanced Manufacturing Technology - The friction model in the tool-chip interface has significant influences on predicting chip forms, cutting forces, and cutting tool...     

在刀-屑界面持续润滑刀具切削45钢的性能及润滑机理

为提高刀具润滑性能,尽量减少切削液的使用,制备出在刀屑界面持续润滑的新型刀具,能够将切削液通过微通道直接输送到刀屑接触界面内部。采用该新型刀具与普通刀具在干切削和浇注切削液条件下分别进行切削45钢试验,测量了切削三向力,对刀具前刀面磨损面进行SEM微观形貌分析及元素检测,分析了刀具的摩擦磨损特性及润滑机理。试验结果表明,与普通刀具在干切削和浇注切削液条件下相比,刀屑界面持续润滑刀具能够有效减少切削过程中的摩擦磨损,而切削液用量只有传统浇注式切削的1/120。分析前刀面的元素可知,切削液能够更加深入到离主切削刃更近的区域,并能持续供给,这是该刀具具有更好的减摩抗磨效果的主要原因。尽管新型刀具的黏结情况大大缓解,但刀具的磨损机理仍然以黏结磨损和氧化磨损为主。     

Slip-line solution for orthogonal cutting with a chip breaker and flank wear

A slip-line field model for orthogonal cutting with chip breaker and flank wear has been developed. For a worn tool, this slip-line field includes a primary deformation zone with finite thickness; two secondary shear zones, one along the rake face and the other along the flank face; a predeformation zone; a curled chip; and a flank force system. It is shown that the cutting geometry is completely determined by specifying the rake angle, tool-chip interface friction and the chip breaker constraint. The chip radius of curvature, chip thickness, and the stresses and velocities within the plastic region are readily computed. Grid deformation patterns, calculated with the velocity field determined, demonstrate that the predicted effects of changes in frictional conditions at the tool-chip interface and of the rake angle on chip formation are in accord with experimental observations. The calculated normal stress distribution at the tool-chip interface is in general agreement with previously reported experimental measurements. The model proposed predicts a linear relationship between flank wear and cutting force components. The results also show that non-zero strains occur at and below the machined surface when machining with a worn tool. Severity and depth of deformation below the machined surface increases with increasing flank wear. Forces acting on the chip breaker surface are found to be small and suggest that chip control for automated machining may be feasible with other means.     

Modeling of cutting force coefficients in cylindrical turning process based on power measurement

The cutting force is an important physical quantity in metal cutting, and the cutting force coefficients are the basis for establishing the cutting force model. In this paper, the relation between the cutting power and the cutting force coefficients is established. A cutting power model was established with a linear relationship between the spindle power and material removal rate (MRR). The power-based model of the main cutting force coefficients is proposed by extracting the linear equation coefficients of the power-MRR function. The power-based model of feed force coefficients is established as a quadratic polynomial equation between the motor power of the feed axis and feed rate. And the cutting force coefficients and the edge force coefficients of feed force are expressed respectively by the two orders of coefficients of the equation. The thrust force coefficients are indirectly calculated from the relation between tangential cutting force and thrust force with friction angle of tool-chip. The power-based models were verified by a series of cutting tests regarding material properties, cutting parameters, and axial directions. The results show that the cutting force coefficients obtained by measuring the cutting power have good correspondence with that identified by dynamometer.