刀具磨损对单晶铝纳米切削过程的影响（英文）

基于分子动力学的理论建立了单晶铝的纳米切削仿真模型,比较研究了在刀具未磨损和刀具磨损条件下对切削过程的影响。研究表明:相比于刀具未磨损,在刀具磨损的情况下,已加工表面质量有所下降,基体上出现了大量的位错等缺陷;切削力也全部有所升高,其中刃口半径磨损对切削力影响最为显著,在相同的切削条件,相比于刀具未磨损升高约为17. 78%,后刀面磨损和前刀面磨损对切削力的影响基本相同,提高了约7. 98%;刀具温度和工件的温度也都有不同程度的升高,其中,工件的温升更高。刀具刃口半径磨损对温升影响最大,达到稳定切削时,刀具的平均温度相比于刀具未磨损升高约为7. 2%。     

切削SiCp/6005Al复合材料的PCD刀具磨损

为研究SiCp/6005Al切削时的刀具磨损机制及刀具磨损对切削力、切削温度、工件表面质量的影响，进行不同转速V和不同进给速度f下的切削试验，观察每组试验刀具切削后的磨损形貌，并通过监测动态切削力和切削温度来探究刀具的磨损机制。结果表明：工件转速提高使切削温度明显升高，但对切削力的影响很小；进给速度提高使切削力明显升高，而切削温度的变化范围较小。改变进给速度带来的力载荷变化是影响前刀面磨损的主要因素，改变工件转速带来的切削温度变化是影响后刀面磨损的主要因素。此外，刀具磨损是磨粒磨损、黏结磨损的综合作用结果，且刀具磨损会对切削力、切削温度和加工表面质量产生不利影响。     

奥氏体不锈钢车削时刀具磨损对切削因素和表面质量的影响研究

研究了奥氏体不锈钢车削加工过程中刀具后刀面磨损对切削力、切削温度、粗糙度及残余应力影响规律。试验结果表明:当刀具后刀面磨损在一定范围内,F_x与F_z随磨损量的增加而显著增大,而F_y基本保持不变;温度随刀具后刀面磨损量增加而显著增大;工件的表面粗糙度随刀具后刀面磨损量增大而增大;当车刀后刀面磨损为0.167 mm时,工件加工表面的残余应力最大。     

表面微织构在切削过程中的研究进展

在切削过程中,临近切削刃的刀具前刀面与切屑、刀具后刀面与已加工表面接触区存在的高温高压情况严重影响了刀具服役寿命和工件表面完整性。表面微织构技术是一种先进的表面改性技术,在刀具表面制备不同尺寸参数、形状参数、分布参数的表面织构能够显著影响刀具的切削性能。当刀具表面微织构制备方法不同时,微织构所呈现的性能也不同。首先从制备技术的原理、制备过程、制备技术特点等方面对当前最先进的刀具表面微织构制备技术进行了综述。然后从切削力、切削温度、刀具磨损、切屑形成、工件表面完整性等角度分析了微织构对刀具切削性能的影响规律与机理。在分析切削力、切削温度、刀具磨损、切屑形成等4个指标时重点关注了刀具前刀面微织构所起的作用,在分析工件表面质量时,同时考虑了刀具后刀面微织构、前刀面微织构的影响。最后,介绍了当前微织构的研究热点,主要包括微织构技术与钝化刃口、润滑剂的协同作用对切削性能的影响,以及微织构刀具在切削过程中发生的衍生切削行为。通过对文献的归纳、总结与深入分析,给出了表面微织构未来的研究方向,为刀具进一步优化提供设计参考。     

刀具几何参数对金属钛纳米切削影响的分子动力学研究

基于分子动力学的基本原理,构建了钛的纳米切削分子动力学仿真模型。工件原子间采用嵌入原子势EAM（Embedded atom method）,工件原子与刀具原子间采用Morse势函数,研究了在不同刃口半径和刀具前角条件下,钛纳米切削过程中工件形态、系统势能、切削力以及工件温度等的变化规律。结果表明：随着刀具刃口半径增大,加工表面粗糙度增加,切削力和工件温度降低,切屑变薄;当刀具前角由负值增加到正值,钛工件承受的压应力逐渐变为剪应力,正前角刀具更有利于切削,同时在不同的刀具前角下,切向力和法向力的大小也有显著变化。     

刀具几何参数对金属钛纳米切削影响的分子动力学研究（英文）

基于分子动力学的基本原理,构建了钛的纳米切削分子动力学仿真模型。工件原子间采用嵌入原子势EAM(Embedded atom method),工件原子与刀具原子间采用Morse势函数,研究了在不同刃口半径和刀具前角条件下,钛纳米切削过程中工件形态、系统势能、切削力以及工件温度等的变化规律。结果表明:随着刀具刃口半径增大,加工表面粗糙度增加,切削力和工件温度降低,切屑变薄;当刀具前角由负值增加到正值,钛工件承受的压应力逐渐变为剪应力,正前角刀具更有利于切削,同时在不同的刀具前角下,切向力和法向力的大小也有显著变化。     

振动切削参数对纳米振动切削过程的影响

采用分子动力学的方法建立了金属钛的纳米振动切削模型,通过切削仿真研究了振动切削参数变化对整个振动切削过程的影响。研究发现:振动频率和振幅的增大会使接触率、切削力及切削温度的数值减小。切削速度增大会使接触率、切削力及切削温度升高,相比对切削力的改变,在切削速度小于100m/s的情况下对切削温度的影响效果更显著。刀具刃口半径的增大会使切削过程中已加工面的变质层厚度增加,表面粗糙度增大,切削力与切削温度的数值随刃口半径的增大而增加,当刃口半径跟切削厚度之比大于1时,背吃刀力及切削温度提升的速率更快。     

基于数值模拟的复合涂层枞树型刀具磨损研究

采用数值模拟法分析了复合涂层枞树型刀具切削过程中切削力、切削温度变化以及刀具磨损情况。基于Deform-3D和Johnson-Cook本构模型,建立切削加工仿真模型,对未涂层的刀具和不同膜厚的Ti N-Ti CN复合涂层枞树型刀具半精加工汽轮机转子轮槽进行切削仿真。结果表明:仿真切削与实际切削结果相比具有一致性。未涂层刀具后期切削力波动剧烈,涂层刀具全程切削力波动稳定,5μm涂层刀具切削力最小;未涂层刀具切削温度显著高于涂层刀具,前中期10μm涂层刀具切削温度略高于5μm刀具,中后期5μm涂层刀具切削温度略高于10μm刀具;刀具磨损最严重出现在前刀面距离刀尖1.89 mm的区域,5μm涂层刀具磨损较轻,未涂层刀具磨损较严重。5μm Ti N-Ti CN多层涂层枞树型刀具切削力小,切削温度较低,刀具磨损量小。     

高温合金切削刀具表面凹槽织构参数的优化研究

为获得切削性能优异的镍基高温合金专用切削刀具,采用有限元仿真和切削试验研究车刀前、后刀面直线型织构凹槽的织构角度、凹槽间距和凹槽宽度对镍基高温合金GH4169切削过程中切削力和切削温度的影响规律。仿真结果表明:前刀面织构能降低刀具切削力和切削温度;与织构间距和凹槽宽度相比,凹槽织构的角度对刀具切削力和切削温度的影响更显著;当在刀具前刀面平行主切削刃建立凹槽状织构,织构间距60μm、凹槽宽度20μm时,切削力较低,切削温度最低。同时,切削试验显示平行于切削刃的织构刀具耐磨损性能和切削寿命均最好。织构刀具的工作寿命相比于无织构刀具提升了66.7%。     

TiN涂层刀具切削淬硬H13钢切削性能试验研究

为研究TiN涂层刀具切削淬硬H13钢的切削性能,进行了TiN涂层刀具车削加工淬硬H13钢试验。分析了切削用量与切削力、切削温度的关系及涂层刀具磨损机制。研究得出切削速度、切削深度、进给量都对主切削力Fz和切深抗力Fx影响较大,对切削进给抗力Fy影响相对较小;切削速度对切削温度的影响最大;对刀具磨损观察发现刀具的前刀面有明显的月牙洼磨损,刀尖部位出现了微崩刃现象,后刀面出现磨粒磨损。研究结果为生产加工中优化切削用量及提高刀具寿命提供了技术支持和试验依据。     

Effects of micro-milling conditions on the cutting forces and process stability

Determining stable cutting conditions for corresponding cutting tools with specific geometries is essential for achieving precision micro-milling with high surface quality. Therefore, this paper investigates the influence of the tool rake angle, tool wear and workpiece preheating on the cutting forces and process stability. An advanced micro-milling cutting force model considering the tool wear is proposed. The micro-milling cutting forces are predicted and compared with experimentally obtained results for two cutting conditions and four edge radii measured at different stages of the tool wear. It is found that the cutting forces increase by increasing the edge radius. It is also observed that the cutting forces are higher at a rake angle of 0° compared with a rake angle of 8°. The increase of the cutting forces is mainly associated with the change of the friction conditions between the tool and workpiece contact. Stability lobes are obtained for different edge radii, rake angles of 0° and 8°, initial workpiece temperature and different measured static run-outs. The predicted stability lobes are compared with the micro-milling force signals transformed into the frequency domain. It is observed that the predicted stability limits result in good correlation with the experimentally obtained chatter free conditions. Also, the stability limits are higher at smaller edge radii, higher preheating workpiece temperature and positive rake angles.     

Experimental studies of cutting force variation in face milling

The purpose of this paper is to present a developed cutting force model for multi-toothed cutting processes, including a complete set of parameters influencing the cutting force variation that has been shown to occur in face milling, and to analyse to what extent these parameters influence the total cutting force variation for a selected tool geometry. The scope is to model and analyse the cutting forces for each individual tooth on the tool, to be able to draw conclusions about how the cutting action for an individual tooth is affected by its neighbours.A previously developed cutting force model for multi-toothed cutting processes is supplemented with three new parameters; eccentricity of the spindle, continuous cutting edge deterioration and load inflicted tool deflection influencing the cutting force variation. A previously developed milling force sensor is used to experimentally analyse the cutting force variation, and to give input to the cutting force simulation performed with the developed cutting force model.The experimental results from the case studied in this paper show that there are mainly three factors influencing the cutting force variation for a tool with new inserts. Radial and axial cutting edge position causes approximately 50% of the force variation for the case studied in this paper. Approximately 40% arises from eccentricity and the remaining 10% is the result of spindle deflection during machining. The experimental results presented in this paper show a new type of cutting force diagrams where the force variation for each individual tooth when two cutting edges are engaged in the workpiece at the same time. The wear studies performed shows a redistribution of the individual main cutting forces dependent on the wear propagation for each tooth.     

Multi-grooved cutting tool to reduce cutting force and temperature during bone machining

The cutting temperature of a cutting tool are required to be low during bone machining for preventing damage to bone cells. However, conventional tools are practically the same as those used for metal cutting, and many operational limitations have been reported. In this study, a dedicated cutting tool was designed for reducing cutting force and temperature. A short contact between the workpiece and the cutting edge leads to a reduction in the cutting force. Furthermore, a straight-line edge improves surface roughness. The effectiveness was evaluated using bovine bone, and the cutting force was found to be decreased by about 40%.     

An investigation of workpiece temperature variation in end milling considering flank rubbing effect

Better prediction about the magnitude and distribution of workpiece temperatures has a great significance for improving performance of metal cutting process, especially in the aviation industry. A thermal model is presented to describe the cyclic temperature variation in the workpiece for end milling. Owing to rapid tool wear in the machining of aeronautical components, flank rubbing effect is considered. In the proposed heat source method for milling, both the cutting edge and time history of process are discretized into elements to tackle geometrical and kinematical complexities. Based on this concept, a technique to calculate the workpiece temperature in stable state, which supposes the tool makes reverse movement, is developed. And a practicable solution is provided by constructing a periodic temperature rise function series. This investigation indicates theoretically and experimentally the impact of different machining conditions, flank wear widths and cutter locations on the variation of workpiece temperature. The model results have been compared with the experimental data obtained by machining 300M steel under different flank wear widths and cutting conditions. The comparison indicates a good agreement both in trends and values. With the alternative method, an accurate simulation of workpiece temperature variation can be achieved and computational time of the algorithm is obviously shorter than that of finite element method. This work can be further employed to optimize cutting conditions for controlling the machined surface integrity.     

The effect of tool nose radius in ultrasonic vibration cutting of hard metal

A tool edge with a small nose radius can alleviate the regenerative chatter. In general, it is important for conventional cutting to use the smallest possible tool nose radius. However, a sharp tool shape has an adverse effect on tool strength and the instability of machining process still occurs. Previous researches have shown that vibration cutting has a higher cutting stability as compared with conventional cutting. In the present paper, the influence of tool nose radius on cutting characteristics including chatter vibration, cutting force and surface roughness is investigated by theory. It is found from the theoretical investigation that a steady vibration created by motion between the tool and the workpiece is still obtained even using a large nose radius in vibration cutting. This article presents a vibration cutting method using a large nose radius in order to solve chatter vibration and tool strength problem in hard-cutting. With a suitable nose radius size, experimental results show that a stable and a precise surface finish is achieved.     

Effect of the Cutting Edge Radius and its Manufacturing Procedure, on the Milling Performance of PVD Coated Cemented Carbide Inserts

The fatigue and wear behaviour of PVD coatings on cemented carbide inserts with various cutting edge radii are investigated experimentally and analytically in milling. The inserts with cutting edge radii from 8 up to 35 μm were manufactured by honing and micro-blasting. The tool wear progress was depicted through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) microspectral analysis. The Finite Elements Method (FEM) simulation of the contact between the tool and the workpiece highlights the effect of the cutting edge radius on the first coating fracture and the further wear development. The wear behaviour of the cutting edge radii manufactured by honing, in comparison to the corresponding ones by means of micro-blasting, is significantly enhanced, whereas the cutting edge radius increasing can lead to a higher tool life.     

Minor cutting edge–workpiece interactions in drilling of an advanced nickel-based superalloy

Drilling is one of the key machining operations for manufacturing safety critical components that must comply with strict surface quality standards. The influence of major flank wear of drilling tools on workpiece surface quality has been well established; however, similar information concerning minor cutting edge is currently missing from literature. This paper presents a comprehensive analysis and discussions of the influence of the drill's minor cutting edge to workpiece surface integrity and residual stress distribution for RR1000, a newly developed nickel-based superalloy. These effects are critical to the acceptance of this new material in relation to tool geometry and machining strategies. The thickness of material drag in the hoop direction has been found to be the highest at the top and the least at the bottom of the hole, which is directly related to the contact duration between the minor cutting edge and workpiece surfaces; moreover this difference increased at higher levels of wear of the minor cutting edge. On-line process monitoring techniques have been employed to further understand the material drag phenomena, including feed force, torque and acoustic emission. Compressive axial and tensile hoop stresses at the surface of the holes have been measured as a function of depth and correlated both with metallurgical analysis of drilled surfaces and the process monitoring signals. It was found that the increased material drag associated with a worn tool resulted in compressive hoop surface residual stresses near the entrance hole in correspondence with trends in the processed acoustic emission signal. This work suggests that material drag increases with the duration of the minor cutting edge–workpiece interaction such that plastic deformation is the greatest near the drill entrance holes and that process monitoring of the degree of material drag in hoop direction can be practicable.     

PcBN刀具连续车削淬硬钢性能的研究

为了研究PcBN刀具在干式连续车削条件下刀具的性能,选用两种不同的PcBN刀具,在不同切削速度及不同工件硬度条件下,对淬硬钢进行车削试验。在此基础上,对刀具前、后刀面的显微形貌特征进行了观察,分析了刀具的失效机理。结果表明:切削速度对刀具的切削寿命影响很大,随着切削速度的增加刀具寿命几乎线性下降。硬度也是影响刀具切削寿命的重要因素之一,当v190 m/m in时,刀具切削硬度为(64±1)HRC工件的寿命比相同条件下切削硬度为(61±1)HRC工件的寿命下降约40%~60%。刀尖温度随着切削速度的增加不多,切屑温度要比刀尖温度高出许多。在本试验中,刀具的失效判据为崩刃或后刀面平均磨损超过0.3 mm。     

Cutting temperature of ceramic tools in high speed machining of difficult-to-cut materials

This paper deals with an experimental and analytical investigation into the different factors which influence the temperature distribution on Al₂O₃---TiC ceramic tool rake face during machining of difficult-to-cut materials, such as case hardened AISI 1552 steel (60–65 Rc) and nickel-based superalloys (e.g. Inconel 718). The temperature distribution was predicted first using the finite element analysis. Temperature measurements on the tool rake face using a thermocouple based technique were performed and the results were verified using the finite element analysis. Experiments were then performed to study the effect of cutting parameters, different tool geometries, tool conditions, and workpiece materials on the cutting edge temperatures. Results presented in this paper indicate that for turning case hardened steel, increasing the cutting speed, feted, and depth of cut will increase the cutting edge temperature. On the other hand, increasing the tool nose radius, and angle of approach reduces the cutting edge temperature, while increasing the width of the tool chamfer will slightly increase the cutting ege temperature. As for the negative rake angle, it was found that there is an optimum value of rake angle where the cutting edge temperature was minimum. For the Inconel 718 material, it was found that the cutting edge temperature reached a minimum at a speed of 510 m/min, and feed of 1.25 mm/rev. However, the effect of the depth of cut and tool nose radius was almost the same as that determined in the turning of case hardened steel. It was also observed in turning Inconel 718 with ceramic tools that, cutting forces and different types of tool wear were reduced with increasing the feed.