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。     

Ti6Al4V钛合金切削力与切削温度场的研究

基于ABAQUS仿真理论,分别建立材料本构模型、摩擦模型和断裂准则,采用局部网格细化使仿真更精确,并对边界条件和材料参数的设置进行了分析,模拟车削加工过程中的切削力和切削温度场,分析了切削力和切削温度场的变化规律,并借助切削试验对切削力进行分析,验证了有限元仿真模型的正确性和仿真结果的可靠性。     

GH4169三维车削力与温度有限元仿真

针对航空难加工材料GH4169高温合金加工过程切削力大且加工易变形的问题,对其车削加工过程中的温度与切削力进行研究。通过对有限元仿真关键技术的讨论,应用Abaqus有限元分析软件,对GH4169材料建立了三维车削模型,对车削过程中的温度场和应力场进行分析;在同样切削条件下,分别得到了三维仿真切削力、实验切削力以及二维切削力,通过切削力的对比分析,验证了三维切削仿真模型的正确性。应用所建立的三维模型模拟出不同切削参数下的切削力,得到了不同切削参数对切削力的影响规律。     

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。     

热源参数对切削性能影响的有限元分析

从工件塑性变形和刀具与工件摩擦的角度出发,分析了切削仿真过程中热量的来源,分别针对不考虑切削热、只考虑塑性热、只考虑摩擦热、同时考虑塑性热及摩擦热四种工况,研究了切削仿真过程中的切削力、切削温度、工件应力和应变以及能量的变化规律,并对不同工况下的仿真效率进行了对比分析.结果表明:在热源参数的软化作用下,切削力和工件应力...     

ABAQUS的高速铣削二维仿真分析

在铣削模型二维等效简化的基础上,对高速切削仿真的关键技术进行了研究,用J-C模型建立工件材料模型,用剪切失效准则实现切屑和工件分离,切屑和刀具的接触摩擦模型采用修正的库仑摩擦定律,在ABAQUS软件中实现了对45钢的高速铣削仿真,对切削力和切屑温度场、应力场的仿真结果进行了分析,验证了有限元模型的合理性.     

薄壁件立铣切削力的有限元模拟与实验研究

薄壁件铣削加工中铣削力是导致加工变形的直接原因,是加工误差的主要影响因素.在考虑刀具变形、工件及刀具材料性能参数的基础上,建立了三维斜角切削力有限元模型,利用有限元分析软件ABAQUS对薄壁件斜角切削过程进行了仿真模拟.其次,针对铣削过程进行了切削力测试,结果表明本文提出的切削力有限元模拟方法具有较高的精度,对切削参数的优化提供了理论依据和便利工具.     

薄壁件加工变形控制快速仿真平台开发

为控制薄壁件装夹变形和加工变形,建立了集装夹优化、加工变形预测、切削参数优化及误差补偿功能为一体的快速仿真平台.在平台实现中,装夹方案的优化采用基于形位公差控制的方法,通过多种装夹方案的比较,确定优化方案.加工变形预测时考虑了前-层变形对后-层切削深度的影响,并使切削力和加工变形达到动态平衡.为获得优化切削参数,建立了以变形控制为目标的优化模型.采用有限元法计算加工变形,采用遗传算法求解优化模型.为解得优化补偿量,仿真时考虑了变形与力的耦合效应.完成了基于ABAQUS的快速仿真平台开发.以镜座零件为例进行仿真,求得了优化的装夹方案和切削参数,验证了平台的可行性.     

基于ABAQUS的TC4合金切削变形区有限元仿真

在不同的切削速度和平面应力应变厚度下,对工件切削变形区的温度和切削力进行了研究。基于弹塑性有限元理论建立TC4合金的二维有限元模型,运用ABAQUS有限元分析软件对TC4合金进行了弹塑性仿真分析。通过分析工件切削变形区的温度变化云图和切削力变化曲线可知:切削速度的变化对工件切削变形区的温度影响较大,平面应力应变厚度影响较小,切削力随着平面应力应变厚度的增加而变大。     

基于正交切削的铝合金切削力理论计算方法

基于传统正交切削力学模型,采用Johnson-Cook材料本构和失效模型,建立同时考虑前刀面和后刀面双摩擦因素的切削力理论计算模型。采用双摩擦切削力模型模拟7050航空铝合金切削力的计算,获得了与试验结果非常吻合的切削力理论计算值。用本文模型计算了不同Johnson-Cook材料本构参数下的切削力,获得了与文献仿真值非常一致的结果。双摩擦切削力模型引入的后刀面摩擦分量,在航空铝合金切削仿真中,占主切削力的比重较少(约占12.5%),但不可忽略。     

切削深度对超精密切削过程影响的有限元分析

基于大变形有限元理论和更新的拉格朗日方程式 ,建立了热耦合的平面应变正交切削有限元仿真模型。采用通用的商业非线性有限元软件 ,对无氧铜超精密切削加工过程进行了仿真 ,研究超精密切削过程中切削深度对切削力、残余应力、等效应力、等效应变和切削温度的影响。通过对超精密切削有限元仿真结果的分析 ,可以优选出合理的切削参数。     

Ultraprecision turning of electroless nickel: effects of crystal orientation and origin of diamond tools

This paper deals with (i) the performance of natural and artificial diamond tools and (ii) the effects of crystal orientations at rake face of diamond tool for long distance (>200 km) ultraprecision machining of electroless nickel. The criteria for cutting performance of the diamond tool include flank wear, crater wear, workpiece surface finish, and cutting forces. Experimental results show that the natural diamond tool has superior performance compared to the artificial one as it experienced lower cutting forces and lower flank and crater wears. It was also found that the cutting tool with {110} crystal orientation at rake face performs better than the tool with {100} crystal orientation in terms of amount of wear, surface finish, and cutting forces.     

TOOL FORCE MODEL FOR DIAMOND TURNING

A new tool force model to be presented is based upon process geometry and the characteristics of the force system, in which the forces acting on the tool rake face, the cutting edge rounding and the clearance face have been considered, and the size effect is accountable for the new model. It is desired that the model can be well applicable to conventional diamond turning and the model may be employed as a tool in the design of diamond tools. This approach is quite different from traditional investigations primarily based on empirical studies. As the depth of cut becomes the same order as the rounded cutting edge radius, sliding along the clearance face due to elastic recovery of workpiece material and plowing due to the rounded cutting edge may become important in micro-machining, the forces acting on the cutting edge rounding and the clearance face can not be neglected. For this reason, it is very important to understand the influence of some parameters on tool forces and develop a model of the relatio     

Elliptical vibration cutting of hardened die steel with coated carbide tools

Elliptical vibration cutting of hardened die steel with coated carbide tools is examined in this research in order to achieve low-cost high-precision machining. Diamond coated tools are applied because of superior hardness of their polycrystalline diamond coating and its low manufacturing cost. TiN coated tools are also tested, since they are widely used for conventional machining of steels. Machinability of hardened die steel by the elliptical vibration cutting with coated carbide tools is discussed in three aspects in this study, i.e. transferability of cutting edge profile to cut surface, cutting force, and tool life. The transferability is evaluated quantitatively by calculating correlation coefficients of measured roughness profiles. It is clarified that the diamond coated tools have high transferability which leads to diffraction of light on the surface machined at micro-scale pick feed. Total cutting forces including ploughing components are measured at various feed rates, and then shearing components and ploughing components are separated utilizing linear regression. The measured results indicate, for example, that the all forces become considerably smaller only when elliptical vibration is applied to the TiN coated tool without cutting fluid. It is also found that this considerable reduction of forces interestingly corresponds to higher friction coefficient, which is identified from the ploughing components. Tool life tests are carried out by various machining methods, i.e. elliptical vibration/ordinary wet/dry cutting with diamond/TiN coated tools. The result shows, for example, that the flank wear is smallest in the wet elliptical vibration cutting with the diamond coated tool.     

Finite element simulation of diamond tool geometries affecting the 3D surface topography in fly cutting of KDP crystals

Diamond tool has significant influences on the finished surface quality in fly cutting of potassium dihydrogen phosphate (KDP) crystals. In this work, the nanoindentation and dimensional analysis are employed to establish the material constitutive equation of KDP crystals, i.e., the variation curve of flow stress vs. plastic strain. As expected, a novel 3D finite element (FE) model is developed for diamond fly cutting of KDP crystals, and the generation of 3D surface topography is simulated by multi-run cutting calculations, in which the movements of diamond tool are configured to be identical to the actual feed rate and cutting velocity. Subsequently, the coordinates of the nodes on the topmost surface as freshly machined are collected to evaluate the surface roughness, which enables the detailed analyses of the effect of diamond tool geometries on the achieved surface roughness of KDP crystals. The results suggest an optimal selection of tool geometries, i.e. ?25° rake angle and 8° clearance angle. With the increment of tool nose radius, surface roughness decreases correspondingly. Moreover, the larger defect or sharpness of tool cutting edge produces the worse surface roughness. Diamond fly cutting experiments are carried out with different rake angles, in which the cutting parameters are the same as the values used in FE simulations. The measured surface roughness has a satisfied consistency with the simulated data, which demonstrates that the developed 3D FE cutting model and the related simulations are reliable.     

Investigation of cutting forces,surface integrity,and tool wear when high-speed milling of high-volume fraction SiC<Subscript>p</Subscript>/Al6063 composites in PCD tooling

This paper focused on high-speed milling of Al6063 matrix composites reinforced with high-volume fraction of small-sized SiC particulates and provided systematic experimental study about cutting forces, thin-walled part deformation, surface integrity, and tool wear during high-speed end milling of 65% volume fraction SiC_p/Al6063 (Al6063/SiC_p/65p) composites in polycrystalline diamond (PCD) tooling. The machined surface morphologies reveal that the cutting mechanism of SiC particulates plays an important role in defect formation mechanisms on the machined surface. In high-speed end milling of Al6063/SiC_p/65p composites, the cutting forces are influenced most considerably by axial depth of cut, and thus the axial depth of cut plays a dominant role in the thin-walled parts deformation. Increased milling speed within a certain range contributes to reducing surface roughness. The surface and sub-surface machined using high-speed milling suffered from less damage compared to low-speed milling. The milling speed influence on surface residual stress is associated with milling-induced heat and deformation. Micro-chipping, abrasive wear, graphitization, grain breaking off, and built-up edge are the dominated wear mechanism of PCD tools. Finally, a series of comparative experiments were performed to study the influence of tool nose radius, average diamond grain size, and machining parameters on PCD tool life.     

Performance of single crystal diamond tools with different rake angles during micro-grooving on electroless nickel plated die materials

In this study, experiments were carried out to establish the effect of tool rake angle on the performance of single crystal diamond tools in micro-grooving of electroless nickel plated molding dies. Diamond tools with rake angles of 0⁰,+5⁰ and ?5⁰ were used in the study, and it was found that the diamond tool with 0⁰ rake angle has superior performance in terms of tool wear, cutting forces, and machined surface roughness. For a cutting distance of up to 11.69 km, the 0⁰ rake tool machined satisfactorily without any sign of tool wear while the tools with +5⁰ and ?5⁰ rake angles suffered from progressive wear with a corresponding increase in cutting forces. However, it was noted that despite the increase in wear on tools with +5⁰ and ?5⁰ rake angles, and cutting forces on the diamond tools with all three different rake angles did not significantly affect the surface roughness. The effects of various cutting parameters such as spindle speed and infeed rate on the cutting forces and surface roughness are also presented in the study. It was observed that cutting forces increase proportionately with spindle speed and infeed rate without any significant variation of surface roughness. Surface quality of up to 3 nm Ra was achieved during micro-grooving of electroless nickel.     

Tool force model development for diamond turning

Accurate determination of forces in the three-dimensional turning process is important for the development of a model to describe diamond turning (DT). This paper describes a dynamometer system which measures force magnitude in steady-state cutting. To build a quantitative model, the forces are experimentally separated into components. The response of these components to a variation of cutting parameters is explained in part by a hardness gradient near the part surface. This gradient is due to work hardening by the tool during previous passes. The extent of plastic work, and thus the hardness gradient, is dependent on the tool edge sharpness (≈ 100 nm). Therefore, the turning forces are strongly influenced by the condition of the tool edge. This paper illustrates the feasibility of finding the connection between edge sharpness and tool forces. It also demonstrates the ability to monitor tool forces over extended periods of time. These relationships are important in predicting the diamond tool edge condition from tool forces during a turning operation.     

Microgrooving on electroless nickel plated materials using a single crystal diamond tool

Diamond tools are used in ultra precision machining for their outstanding hardness and crystalline structure, which enable the fabrication of very sharp cutting edges. Single crystal diamond tools are thus extremely useful to machine electroless nickel-plated dies which are generally used for making molds for optical components. This paper deals with the objective to evaluate the performance and suitability of a single crystal diamond tool during microgrooving on electroless nickel plated workpieces. Effects of different machining parameters on overall machining performance were also investigated. The experimental results revealed that long distance (50 km) machining of microgrooves on electroless nickel is possible with a single crystal diamond tool without any significant tool wear. Some groove wear on the rake face were found after machining 28.5 km. No evidence of chipping or wear had been observed on the flank face during the total machining length. The surface roughness range of the machined workpieces was found to be 4–6 nm. Both thrust and cutting components of the machining forces showed an increasing trend with increasing machining distance, though magnitude of the thrust forces were found to increase more than the cutting forces.