油气冷却技术在车削加工中的应用研究

绿色加工技术是21世纪机械加工业的发展方向.通过采用双热电偶的接触式温度测量方法,测量刀具上两点的温度随切削深度和冷却方式的变化情况,推算刀尖温度的变化情况,比较不同的冷却方式对刀尖的冷却润滑效果.试验结果表明,油气冷却切削加工技术是一种绿色切削加工技术.研究油气润滑冷却切削加工技术,对提高切削加工件的表面质量,降低切削加工的成本等具有重要意义.     

涂层刀具硬态车削H13钢温度场模拟研究

基于有限元方法建立了H13钢硬态车削的仿真模型,应用Ti N、Ti C、Ti Al N、Al2O3涂层刀具对硬态切削H13钢在切削速度100-400m/min范围内的切削温度进行了模拟研究,重点分析了刀具前刀面上关键点的温度变化趋势及切削速度对该点温度的影响。仿真结果表明:涂层材料对切削温度产生一定影响,Ti C涂层刀具切削时温度最低;切削速度对切削温度有直接影响,切削速度越高,切削温度越高,越容易形成锯齿形切屑;刀具前刀面温度最高点出现在前刀面靠近刀尖的一点,即容易形成月牙洼磨损的位置。     

基于AdvantEdge FEM的车刀参数优化试验研究

在金属切削加工中,刀片对切削性能具有重要影响;为实现车削45钢的切削刀片优化,以前角、刃倾角和刀尖圆弧半径作为优化变量,利用正交试验法设计试验方案;在有限元软件AdvantE dge中建立切削模型,对切削过程中的切削力和切削温度进行模拟仿真;最后以切削仿真值作为正交试验值,对切削力和切削温度分别进行极差分析和方差分析,得到最优的刀片参数方案。     

刀具几何参数对铝合金车削性能的影响

根据刀具的主要几何参数设计了单因素实验,在Deform-3D中建立了铝合金7075的车削有限元模型,对车削过程进行仿真,通过数据处理,得出前角、主偏角、刃倾角、刀尖圆弧半径对切削力和切削温度的影响,结果表明:切削力随前角的增大而减小,随刀尖圆弧半径的增大而增大,主偏角和刃倾角对各方向上的力影响不同;切削温度随前角、刃倾角的增大而上升,随刀尖圆弧半径的增大而下降。     

基于神经网络的高速硬车削切削力预测研究

采用PCBN刀具进行高速硬车削AISI P20淬硬钢的切削试验,并通过方差分析研究切削速度、进给量、切削深度和刀尖圆弧半径对切削力的影响.基于获得的试验数据,应用人工神经网络方法建立高速硬车削P20淬硬钢时的切削力预测模型.试验与仿真分析显示,切削力随进给量、切削深度和刀尖圆弧半径的增加而增大,而不同切削速度下的切削力值几乎保持不变;同时,切削深度对切削力的影响最为显著,其次为进给量,再次为刀尖圆弧半径,而切削速度的影响则非常微弱.     

数控机床刀具半径补偿功能的应用研究

数控车削加工是以假想刀尖进行编程,而切削加工时,由于刀尖圆弧半径的存在,实际切削点与假想刀尖不重合,从而产生加工误差。为满足加工精度要求,又方便编程,需对刀尖圆弧半径进行补偿。本文对刀尖半径补偿的概念,刀尖方位的确定、补偿方法和参数设置进行了介绍,同时阐述了刀尖半径补偿的过程,就应用过程中出现的问题加以介绍。     

高速车削镍基高温合金GH4169的切削力仿真研究

基于Deform 3D仿真软件建立了GH4169高温合金高速车削的有限元模型,采用四因素三水平正交试验方法研究了切削用量和刀具几何参数对切削力的影响规律,并建立了切削力经验公式。研究结果表明:在高速车削GH4169的过程中,对切削力影响最大的参数是切削深度,其次是进给量和前角,最后是刀尖圆弧半径;切削力随切削深度和进给量的增大而增大,随前角的增大呈现先降低又升高的趋势,而刀尖圆弧半径增大时切削力变化不大;最佳参数组合为:进给量0.2mm/r,切削深度0.4mm,前角10°,刀尖圆弧半径0.2mm。     

镍基高温合金锥面外圆车削表面粗糙度优化研究

以GH4169镍基高温合金外圆锥面车削加工为研究对象,通过正交实验的方法,研究切削参数对加工表面粗糙度的影响规律。并运用BP神经网络预测的方法建立了表面粗糙度经验模型。经过实验验证,该模型具有较好的预测精度。另外还对工件表面粗糙度与刀尖圆弧半径及切削深度的关系进行了研究。发现较大的刀尖圆弧半径能获得较小的表面粗糙度值,且增大刀尖圆弧半径可进一步减小切削深度对表面粗糙度的影响。该研究结果可为GH4169圆锥面车削加工提供技术指导和理论支持。     

基于Deform 3D的42CrMo钢车削加工仿真研究

42Cr Mo钢是一种应用广泛的高强度合金结构钢,为了研究42Cr Mo钢的车削过程,应用Deform 3D软件进行车削加工仿真,结合仿真结果分析了车削过程中切削力和切削温度的变化规律,为42Cr Mo钢实际车削加工切削力和切削热研究提供理论参考。     

车削参数对超高强度钢车削性能的影响

通过正交仿真试验分析300M钢在车削过程中切削速度V、背吃刀量a_p、进给量f以及刀尖圆弧半径r_ε对车削300M钢切削力的影响。采用方差分析法和极差分析法确定车削参数的最优组合,并检验4个因素对切削三向力的显著性。结果表明,4个因素中,背吃刀量a_p对切削力的影响最为显著,其次是进给量和刀尖圆弧半径,切削速度对切削力的影响程度最小。使用MATLAB软件对切削三向力与各个因素之间的关系进行多元线性回归分析,并建立切削三向力经验公式。通过对比分析经验公式与仿真分析得到的三向力,确定经验公式准确可靠。     

瞬态切削用智能测温刀具的研究

针对传统切削温度测量手段无法实时测量刀尖切削区域瞬态温度的技术难题,研制一种基于NiCr-NiSi薄膜热电偶的瞬态切削用智能测温刀具,采用直流脉冲磁控溅射技术制备了致密性和绝缘效果良好的SiO₂绝缘薄膜及热电偶电极薄膜;利用自行研制的薄膜热电偶自动标定系统对研制的测温刀片的静、动态技术特性进行测试和分析,结果表明所研制的测温刀片在30～300℃范围内具有良好的线性,其塞贝克系数为40.5 μV/K,最大线性误差不超过0.92%,且响应速度快,时间常数为0.083 ms;可嵌入刀杆的温度测试单元实现了在切削加工过程中对瞬态切削温度数据的实时采集、数据存储与无线传输功能;现场试验结果显示,所研制的智能测温刀具可以快速准确监测0.1 s内刀具刀尖处瞬态切削温度的变化,为瞬态切削温度测试提供了新的方法,为智能测温刀具的研究与开发提供了新的技术途径。     

In-cycle detection of built-up edge (BUE) from 2-D images of cutting tools using machine vision

The built-up edge (BUE) phenomenon that appears under certain machining condition, such as low-to-moderate cutting speed, high depth of cut, dry cutting, cutting of ductile material, etc. is known to have a major effect on the surface quality of the finished workpiece. In the published literature, BUE has been measured using scanning electron microscope and optical microscopes to study its effect on tool life and surface quality. Such measurement methods are only applicable in off-the-machine inspection. Since the BUE extending beyond the tool nose alters the tool geometry and, thus, influences the workpiece roughness profile, detection of BUE outside the nose region is important. This research proposes a new method for detecting BUE from 2-D images of the nose region of the tool using a machine vision approach. Two methods of determining the BUE area are proposed—the subtraction method and polar-radius transformation method. Application of both methods is successfully demonstrated using simulated and real cutting tool images.     

Cutting heat dissipation in high-speed machining of carbon steel based on the calorimetric method

The cutting heat dissipation in chips, workpiece, tool and surroundings during the high-speed machining of carbon steel is quantitatively investigated based on the calorimetric method. Water is used as the medium to absorb the cutting heat; a self-designed container suitable for the high-speed lathe is used to collect the chips, and two other containers are adopted to absorb the cutting heat dissipated in the workpiece and tool, respectively. The temperature variations of the water, chips, workpiece, tool and surroundings during the closed high-speed machining are then measured. Thus, the cutting heat dissipated in each component of the cutting system, total cutting heat and heat flux are calculated. Moreover, the power resulting from the main cutting force is obtained according to the measured cutting force and predetermined cutting speed. The accuracy of cutting heat measurement by the calorimetric method is finally evaluated by comparing the total cutting heat flux with the power resulting from the main cutting force.     

Prediction of cutting temperature distributions on rake face of coated cutting tools

Coated cutting tools have been widely employed in metal cutting operations owing to its excellent abrasion resistance and heat transfer performances. Rake face temperature is the primary factor that determines the temperature distribution in the cutting tool body. Based on the heat source theory, a new prediction model is proposed in this paper to forecast the temperature distribution on the rake face. Infrared image is used to develop a new turning experimental apparatus to measure the rake face temperature of coated tool during the cutting process. Rake face temperature measurement results are used to verify the proposed model prediction results of temperature distribution. Several cutting tests are carried out with monolayer coated tools in the machining of H13 hardened steel. The rake face temperature in monolayer coated tool for machining H13 shows an increase trend as the cutting speed increases. The influence parameters including thermo-physical properties and tool/workpiece frictional coefficient of coating material on temperature distribution in coated tools are discussed and illustrated. The research results presented in this paper can help to access the potential of coated tools used in the hardened steel machining.     

用解析法计算高速切削单涂层刀具瞬态温度分布

为研究涂层在切削中对刀具温度的影响,为设计刀具涂层提供理论依据,分析高速切削过程中切削热的产生和刀具边界情况,建立单涂层刀具热传导物理模型和数学模型,用数学解析的方法推导出正交高速干切削过程中单涂层刀具体内部的温度分布公式。利用推导出的温度公式对TiN、TiC、Al2O3涂层刀具的切削温度分布进行解析计算,并将解析计算结果与数值分析结果进行比较。结果表明,解析计算结果与数值计算结果吻合很好;涂层材料与基体材料的热物理性能以及涂层的厚度对刀具的温升有重要影响;随着热流密度的增加,涂层厚度对刀具内部的温度影响增大。     

Extraction of flank wear growth models that correlates cutting edge integrity of ball nose end mills while machining titanium

The application of titanium alloys are increasingly seen at aerospace, marine, bio-medical and precision engineering due to its high strength to weight ratio and high temperature properties. However, while machining the titanium alloys using solid carbide tools, even with jet infusion of coolant lower tool life was vividly seen. The high temperatures generated at the tool?Cwork interface causes adhesion of work-material on the cutting edges; hence, shorter tool life was reported. To reduce the high tool?Cwork interface temperature positive rake angle, higher primary relief and higher secondary relief were configured on the ball nose end-mill cutting edges. However, after an initial working period, the growth of flank wear facilitates higher cutting forces followed by work-material adhesion on the cutting edges. Therefore, it is important to blend the strength, sharpness and surface integrity on the cutting edges so that the ball nose end mill would demonstrate an extended tool-life. Presently, validation of tool geometry is very tedious as it requires extensive machining experiments. This paper illustrates a new feature-based ball-nose-end-mill?Cwork interface model with correlations to the material removal mechanisms by which the tool geometry optimization becomes easier. The data are further deployed to develop a multi-sensory feature extraction/correlation model to predict the performance using wavelet analysis and Wagner Ville distribution. Conclusively, this method enables to evaluate the different ball nose end mill geometry and reduces the product development cycle time.     

Investigation of dry machining with embedded heat pipe cooling by finite element analysis and experiments

This paper investigates the performance of a cutting tool embedded with a heat pipe on reducing cutting temperature and wear in machining. The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy, as well as the tool life in machining. A new embedded heat pipe technology has been developed to effectively remove the heat generated at the tool–chip interface in machining, thereby, reducing tool wear and prolonging tool life. In particular, the technique can effectively minimize pollution and contamination of the environment caused by cutting fluids, and the health problems of skin exposure and particulate inhalation in manufacturing. The ANSYS finite element analysis simulations show that the temperature near the cutting edge drops significantly with an embedded heat pipe during machining. Temperature measurements at several locations on the cutting tool insert agree with the simulation results both with and without the heat pipe. Experiments were carried out to characterize the temperature distributions when performing turning experiments using a cutting tool installed with an embedded heat pipe. The performance of the heat pipe on reducing the cutting tool temperature was further supported by the observations of cutting tool material color, chip color, and the chip radius of curvature.     

On-line monitoring of tool wear in turning operation in the presence of tool misalignment

A vision system using high-resolution CCD camera and back-light was developed for the on-line measurement of nose wear of cutting tool inserts. Initial study showed that the system is sensitive to several factors in the work environment such as misalignment of cutting tool, presence of micro-dust particles, vibration and intensity variation of ambient light. An algorithm using Wiener filtering, median filtering, morphological operations and thresholding was developed to decrease the system error caused by these factors. A conforming method was used to overcome misalignment of the tool insert during offline and on-line measurement. The algorithm, combined with a subtraction method, was applied to measure the nose wear area of the inserts under different machining conditions.     

Investigation of heat partition in dry turning assisted by heat pipe cooling

Dissipation of the cutting heat through the cutting tool assisted by the heat pipe is a new cooling method in metal cutting. However, as an important indicator to evaluate the cooling performance, the heat partition in the cutting process for the heat pipe cutter has not been reported in the previous publications. This investigation is concerned with the estimation of the amount of heat flowing into the heat pipe cutter and that dissipated by the heat pipe. The aim is to characterize the heat partition of the heat pipe cutter and thus evaluate its cooling performance. Experimental results are presented of temperature measurements at the accessible positions on the cutter during orthogonal cutting. With these measured temperatures, the finite different methods and an inverse procedure are utilized to solve the heat flux loaded on the tool–chip interface and the amount of heat flowing into each part of the heat pipe cutter. It is shown that the installation of the heat pipe increases the heat flowing into the tool; however, much greater amount of heat can be dissipated by the heat pipe; this results in the reduction of the temperature at tool–chip interface.     

AN EXPERIMENTAL EVALUATION OF CUTTING TEMPERATURES DURING HIGH SPEED MACHINING OF HARDENED D2 TOOL STEEL

This paper investigates experimentally the effects of different process parameters on the cutting edge temperature during high speed machining of D2 tool steel using polycrystalline cubic boron nitride (PCBN) tools. The cutting edge temperature is measured using thermocouples. The process parameters considered are cutting speed, feed rate, nose radius, rake angle, and tool wear. The effects of different edge preparations including sharp, honed and chamfered are also investigated. The results show that increasing cutting speed and feed rate increases the cutting temperature while increasing nose radius reduces the cutting edge temperature. In addition, there is an optimum rake angle value at which minimum cutting temperature is generated.