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外文翻译EFFECTS OF CUTTING EDGE GEOMETRY,WORKPIECE HARDNESS，FEED RATE AND CUTTING SPEED ON SURFACE ROUGHNESS AND FORCES IN FINISH TURNING OF HARDENED AISI H13 STEEL切削刃几何形状、工件硬度、进料率和切削速度对H13 钢精加工表面粗糙度和力的影响 EFFECTS OF CUTTING EDGE GEOMETRY,WORKPIECE HARDNESS, FEED RATE AND CUTTING SPEED ON SURFACE ROUGHNESS AND FORCES IN FINISH TURNING OF HARDENED AISI H13 STEEL Tugrul zel, Tsu-Kong Hsu, Erol Zeren Department of Industrial and Systems Engineering Rutgers, The State University of New Jersey, New Jersey 08854 USA AbstractIn this study, effects of cutting edge geometry, workpiece hardness, feed rate and cutting speed on surface roughness and resultant forces in the finish hard turning of AISI H13 steel were experimentally investigated. Cubic boron nitrite inserts with two distinct edge preparations and through-hardened AISI H-13 steel bars were used. Four factor (hardness, edge geometry, feed rate and cutting speed)- two level fractional experiments were conducted and statistical analysis of variance was performed. During hard turning experiments, three components of tool forces and roughness of the machined surface were measured. This study shows that the effects of workpiece hardness, cutting edge geometry, feed rate and cutting speed on surface roughness are statistically significant. The effects of two-factor interactions of the edge geometry and the workpiece hardness, the edge geometry and the feed rate, and the cutting speed and feed rate are also appeared to be important. Especially, small edge radius and lower workpiece surface hardness resulted in better surface roughness. Cutting edge geometry, workpiece hardness and cutting speed are found to be affecting force components. The lower workpiece surface hardness and small edge radius resulted in lower tangential and radial forces.1. INTRODUCTION Hard turning, machining ferrous metal parts that are hardened usually between 45-70 HRC, can be performed dry using polycrystalline cubic boron nitride (PCBN, commonly CBN) cutting tools as extensively reported in literature 1-8. Research results in the literature concerning mechanism of serrated chip formation in order to relate process characteristics and stability of cutting to the chip shapes during hard turning 9-19. Other research concerning with composition, temperatures and wear characteristics of CBN cutting tools 1,8,20,21,22,28 and effects of work material properties, tool geometry and cutting conditions on surface integrity of the finish machined parts 23-28 indicate challenges in hard turning and identifies various process, equipment and tooling related factors affecting surface quality, tool life and productivity. After reviewing the literature, factors affecting forces, tool wear/failure and roughness and integrity of the finished surfaces in hard turning using CBN cutting tools and their influences on each other are illustrated with a chart shown in Fig. 1. In this chart, the parameters above the horizontal dashed lines are considered as factors or inputs to the hard turning process and they can only be selected in the beginning except tool vibration. All other parameters, that are located below these dashed lines, considered as performance measures or outputs of the hard turning process. Review of the literature reveals that almost all of the factors given in this chart affect performance of the hard turning process. Those factors can be classified as follows:1.1 Cutting tool geometry and material propertiesHard turning with CBN cutting tools demands prudent design of tool geometry. CBN cutting tools have lower toughness than other common tool materials, thus chipping ismore likely 2. Therefore, a nose radius and proper edge preparation are essential to increase the strength of cutting edge and attain favorable surface characteristics on finished metal components 23. CBN cutting tools designed for hard turning feature negative rake geometry and edge preparation (a chamfer or a hone, or even both). Specifications of the edge preparation design are often finalized after extensive experimentation. Fig. 2 shows the types of edge preparations common for CBN cutting tools. According to recent studies, it is evident that effect of edge geometry on surface quality is significant 23-28.Fig. 1. A flow chart illustrating relationships of factors in hard turning.Theile et al. 24, 25, presented research results of an experimental investigation of effects of cutting edge geometry and workpiece hardness on residual stresses in finish hard turning of AISI 52100 steel. They indicated that both factors are significant for the surface integrity of finish hard turned components. Specifically, they showed that large hone radius tools produce more compressive stresses, but also leave “white-layers”. zel 26 investigated the influence of edge geometry in CBN tools with respect to stress and temperature development through finite element simulations in hard turning. Chou et al. 28 experimentally investigated the influence of CBN content on surface quality and tool wear in hardened AISI 52100 steel tool. This study concluded that low content CBN tools produce better surface roughness with respect to higher content CBN tools and depth of cut has minor effect on tool wear rate.Fig. 2. Type of edge preparations for CBN cutting tools.1.2 Workpiece hardness Due to the changes in properties of hardened workpiece material, basic shearing process and formation of chips differ in hard turning 5. Prior research showed that workpiece hardness has a profound effect on the performance of the CBN tools 1,2,8 and also integrity of finish machined surfaces 23,25. Matsumoto et al. On the return trip the bottom coal is mined with the advantage of a free face and a smaller proportion of the leading drum cutting coal; consequently leading to less restrictions of the haulage speed due to the specific cutting energy of the material. The shearer sumps in mid seam near the head gate to the full web without invoking unproductive cycle time. 23 and Thiele et al. 25 studied the effect of workpiece hardness on residual stresses. In a recent study, Guo and Liu 27 investigated material properties of hardened AISI 52100 bearing steel using temperature controlled tensile tests and orthogonal cutting tests and demonstrated that hardness greatly influences the material properties accounting for high variation in flow stress properties.1.3 Cutting speed, feed rate and depth of cut Performance of CBN cutting tools is highly dependent on the cutting conditions i.e. cutting speed, feed, feed-rate, and depth of cut 7. Especially cutting speed and depth of cut significantly influence tool life 22. Increased cutting speed and depth of cut result in increased temperatures at the cutting zone. Since CBN is a ceramic material, at elevated temperatures chemical wear becomes a leading wear mechanism and often accelerates weakening of cutting edge, resulting in premature tool failure (chipping), namely edge breakage of the cutting tool. In addition, Thiele et al. 24 noticed that when feed rate is increased, residual stresses change from compressive to tensile. 1.4 Surface integrity, residual stresses and tool wear In general, residual stresses become more compressive as workpiece hardness increases. The hardness and fracture toughness of CBN tools decrease with reduced CBN content 8. Owing to ceramic binder phase, CBN-L tools have a lower thermal conductivity, which causes increasing temperatures of cutting edge during hard turning. Chou and Barash 9 reported that CBN-L tools are more suitable for finish turning of hardened steel. At low cutting speeds, tool life of CBN-L is superior to CBN-H, whereas at higher cutting speeds, the reverse is true, and also surface roughness is less favorable when using CBN-H tool 28. Thiele et al. 24 reported that residual stresses generated by large edge hone tools are typically more compressive than stresses produced by small edge hone tools and they also leave white-layers. In addition, the effects of edge geometry play an important role in thermoplastic deformation of the workpiece. Koenig et al. 3 reported that an increase in feed rate raises the compressive residual stress maximal and deepens the affected zone. It was also suggested that the chamfer is unfavorable in terms of attainable surface finish when compared to honed or sharp edges.1.5 Accuracy and rigidity of the machine tool Another parameter that is often ignored is tool vibration. In order to reduce tool vibration it is necessary provide sufficiently rigid tool and workpiece fixtures. Assuring that there is minimal tool vibration is an easy way to improve surface roughness. It is also necessary that the tooling system be extremely rigid to withstand the immense cutting forces. It is well known that the radial force is the largest among force components during hard turning. Many researchers indicated that extremely rigid, high power, and high precision machine tools are required for hard turning because CBN tools are brittle and prone to chipping 3, 7, 8, 14, 23. It is also suggested that having higher rigidity in machine tool-clamping-tooling system achieves better surface quality on the part. It is well known that vibration and chatter are important problems that degrade part quality and tool performance. To improve the overall efficiency of finish hard turning, it is necessary to have a complete process understanding. To this end, a great deal of research has been performed in order to quantify the effect of various hard turning process parameters to surface quality. In order to gain a greater understanding of the hard turning process it is necessary to understand the impact of each of these variables, but also the interactions between them. It is impossible to find all of the variables that impact surface quality in finish hard turning. In addition, it is costly and time-consuming to discern the effect of every variable on the output.2. EXPERIMENTAL PROCEDURE 2.1 Workpiece material The workpiece material used in this study was AISI H13 hot work tool steel, which is used for high demand tooling. The cylindrical bar AISI H13 specimen that are utilized in this experiments had a diameter of 1.25 inches and length of 2 feet. The bar specimens were heat treated (through-hardened) at in-house heat treatment facility in order to obtain the desired hardness values of 50 and 55 HRC. However, the subsequent hardness tests by using Future Tech Rockwell type hardness tester revealed that the actual hardness of each specimen was 51.31.0 and 54.70.5 HRC. Henceforth, the hardness values are defined by the mean values of the measured workpiece hardness. 2.2 Tooling and edge geometry CBN inserts with two distinct representative types of edge preparations were investigated in this study. These edge preparations include: a) “chamfered” (T-land) edges and b) “honed” edges as illustrated in Fig.2. Solid top CBN inserts (TNM-433 and GE Superabrasives BZN 8100 grade) inserts were used with a Kennametal DTGNR-124B right hand tool holder with 00 lead and 50 rake angles. Honed and chamfered insert edge geometry were measured in coordinated measurement machine with three replications using a high precision touch-trigger probe. For the honed inserts, an average radius of 10.5 4.0 m was found. Chamfered insert edge geometry was found to have 200 chamfer angle and 0.1 0.03 mm chamfer width using same instruments with three replications and was approximated to an equivalent hone radius of 101.6 5.1 m. A categorization of shearer loader cutting sequences is realised by four major parameters . Firstly, one can separate between mining methods, which mine coal in two directions meaning from the head to the tailgate and on the return run as well or in one direction only. Secondly, the way the mining sequence deals with the situation at the face ends, to advance face line after extract-ing the equivalent of a cutting web, is a characteristic parameter for each separate method. The nec-essary travel distance while sumping varies between the sequences, as does the time needed to per-form this task, too. Another aspect defining the sequences is the proportion of the web cutting coal per run. Whereas traditionally the full web was used, the introduction of modern AFC and roof sup-port automation control systems allows for efficient operations using half web methods. The forth parameter identifying state of the art shearer loader cutting sequences is the opening created per run.2.3 Experimental design A four factor two level factorial design was used to determine the effects of the cutting edge geometry, workpiece hardness, feed rate and cutting speed on surface roughness and resultant forces in the finish hard turning of AISI H 13 steel. The factors and factor levels are summarized in Table 1. These factor levels results in a total of 16 unique factor level combinations. Sixteen replications of each factor level combinations were conducted resulting in a total of 256 tests. Each replication represents 25.4 mm cutting length in axial direction. The response variables are the workpiece surface roughness and the cutting forces.Longitudinal turning was conducted on a rigid, high-precision CNC lathe (Romi Centur 35E) at a constant depth of cut at 0.254 mm. The bar workpieces were held in the machine with a collet to minimize run-out and maximize rigidity. The length of cut for each test was 25.4 mm in the axial direction. Due to availability constraints, each insert were used for one factor level combination, which consisted of 16 replications. (A total of three honed and three chamfer inserts were available). In this manner each edge preparation was subject to the same number of tests and the same axial length of cut. Finally, surface roughness and tool wear measurements were conducted when the cutting length reached 203.2 mm (8 inches) and 406.4 mm (16 inches) during each factor level combination. The surface roughness was measured with a Taylor-Habson Surtronic 3+ profilometer and Mitutoyo SJ-digital surface analyzer, using a trace length of 4.8 mm, a cut-off length of 0.8 mm. The surface roughness values were recorded at eight equally spaced locations around the circumference every 25.4 mm distance from the edge of the specimen to obtain statistically meaningful data for each factor level combination. CBN inserts were examined using a tool-maker microscope to measure flank wear depth and detect undesirable features on the edge of the cutting tool by interrupting finish hard turning process. 2.4 Cutting force measurements The cutting forces were measured with a three-component force dynamometer (Kistler Type 9121) mount on the turret disk of the CNC lathe via a custom designed turret adapter (Kistler type 9121) for the toolholder creating a very rigid tooling fixture. The charge signal generated at the dynamometer was amplified using charge amplifiers (Kistler Type 5814B1). The amplified signal is acquired and sampled by using data acquisition PCMCIA card and Kistler DyanoWare software on a laptop computer at a sampling frequency of 2000 Hz per channel. Time-series profiles of the acquired force data reveal that the forces are relatively constant over the length of cut and factors such as vibration and spindle run-out were negligible. Three components of the resultant force are shown schematically in Fig. 3. Fig. 3. Measured cutting-force components.3. RESULTS AND DISCUSSION An analysis of variance (ANOVA) was conducted to identify statistically significant trends in the measured surface roughness and cutting force data. Separate ANOVA analyses were conducted for Ra surface roughness values and for each component of the cutting force i.e. axial (feed), radial (thrust), and tangential (cutting) forces. Additionally, plots of significant factors corresponding to each ANOVA analysis were constructed. These plots provide a more in-depth analysis of the significant factors related to the surface roughness and cutting forces in finish hard turning of AISI H13 steel using chamfered and honed CBN inserts.3.1 ANOVA results ANOVA tables for Ra surface roughness parameters are given in Table 2. In addition to degree of freedom (DF), mean square (MS) and F values (F) the table shows the P-values (P) associate with each factor level and interaction. A low P-value indicates an indication of statistical significange for the source on the response. Table 2 show that the main effects of edge geometry, cutting speed and feed rate except hardness, interactions between edge geometry and hardness, feed rate, and cutting speed, the interactions between cutting speed and feed rate are significant to surface roughness. Feed rate is the dominant parameter associated with the surface roughness. This is expected because it is well known that the theoretical surface roughness is primarily a function of the feed for a given nose radius and varies as the square of the feed rate 8.The advantage of the half- or, more precisely, partial- opening cutting sequence is the fact that the face is extracted in two passes. Figure 2b shows that the upper and middle part of the seam is cut during the pass towards the tailgate. Whereas the last part of this trip for the equivalent of a ma-chine length the leading drum is raised to cut the roof to allow the roof support to be advanced. On the return trip the bottom coal is mined with the advantage of a free face and a smaller proportion of the leading drum cutting coal; consequently leading to less restrictions of the haulage speed due to the specific cutting energy of the material. The shearer sumps in mid seam near the head gate to the full web without invoking unproductive cycle time. Like for the trip the tailgate the leading drum has to be lowered a machine length ahead of the main gate.The radial force is usually the largest, tangential force is the middle and the axial (feed) force is the smallest in finish hard turning. In general, cutting force components are influences by cutting speed, edge geometry and feed rate. Tables 3-5 are ANOVA tables corresponding to the radial, axial (feed force) and tangential components of the cutting force, respectively. These tables show that the main effects of workpiece hardness, the edge geometry, cutting speed and feed rate (except for axial force) are all significant with respect to the forces in the radial, axial and tangential directions.Table 3 shows that the main effects of the edge geometry, cutting speed, hardness and the interactions between edge geometry and hardness, cutting speed, feed rate are significant with respect to the forces in the axial (feed) direction. Axial (feed) force is not much influence by the change in feed rate. Table 4 shows that the main effects of the edge geometry, cutting speed, hardness and only the interactions between edge geometry and cutting speed, feed rate are significant with respect to the forces in the radial direction.Table 5 shows that the main effects of the edge geometry, cutting speed, hardness, feed and only the interactions between edge geometry and hardness, cutting speed, feed rate are significant with respect to the forces in the tangential direction.3.2 Effect of feed rate and edge preparation on surface roughness Graphs of Ra surface roughness parameters are shown in Figures 4 and 5. These figures have been constructed to illustrate the main effects of edge geometry and feed rate parameters on the surface roughness. Based on the previous analysis, the main effect of the interaction between edge geometry and feed rate are found to be statistically significant on surface roughness Ra. Fig. 4 shows the effect of edge geometry and feed rate on the Ra surface roughness parameter for 54.7 HRC, cutting speed 200 m/min and cutting length of 406.4 mm. Fig. 5 shows the effect of edge geometry and feed rate on the Ra surface roughness parameter for 51.3 HRC with cutting speed of 100 m/min and cutting length of 25.4 mm.Fig. 4. Effect of cutting edge geometry and feed rate on surface roughness (high levels).Fig. 5. Effect of cutting edge geometry and feed on surface roughness (low levels).These two figures show that all edge preparations are confounded at the lowest feed rate (0.05mm/rev). However, the large edge radius resulted in better surface roughness when higher hardness and cutting speed selected, whereas it is the opposite when lower hardness and cutting speed selected. Finally, it should be noted that the main effect due to feed is readily apparent for each edge preparation. Specifically, the surface roughness increases as the feed rate increases as the surface roughness being proportional to the square of the feed rate. 3. 3 Effect of surface hardness and edge preparation on surface roughness Fig. 6 is constructed to illustrate the main effects of edge geometry and surface hardness parameters on the surface roughness with cutting speed 200 m/min, feed rate 0.2 mm/rev and cutting length 406.4 mm. Based on the previous analysis, the main effect of the interaction between edge geometry and workpiece surface hardness are statistically significant to surface roughness Ra parameters. The figure shows that small edge radius and lower workpiece surface hardness resulted in better surface roughness.Fig. 6. Effect of cutting edge geometry and hardness on surface roughness.3.4 Effect of surface hardness and edge preparation on tangential, radial and axial (feed) forces Graphs of the force components as functions of edge geometry and workpiece surface hardness are shown in Figs. 7-9. These figures show that chamfered edge geometry and higher workpiece surface hardness result in higher tangential and radial forces but not in axial (feed) force. Additionally, small honed radius edge geometry results in higher forces in the axial (feed) directions. Fig. 7: Effect of cutting edge geometry and surface hardness on tangential force.Fig. 8: Effect of cutting edge geometry and surface hardness on radial force.Fig. 9: Effect of cutting edge geometry and surface hardness on axial force.3.5 Effect of cutting speed and cutting edge geometry on tangential force Fig. 10 is obtained to illustrate the main effects of edge geometry and cutting speed parameters on tangential force. Based on the previous analysis, the main effect of the edge geometry and cutting speed are statistically significant to tangential force. Fig. 10 shows that higher cutting speed and smaller edge radius resulted in lower tangential force. 3.6 Effect of cutting speed and feed rate on tangential force Fig. 11 is obtained to illustrate the main effects of cutting speed and feed rate parameters on tangential force. Based on the previous analysis, the interaction of cutting speed and feed rate are statistically significant to tangential force. Fig. 11 shows that lower cutting speed and lower feed rate resulted in lower tangential force.Fig. 10 Effect of cutting speed and cutting edge geometry on tangential force.Fig. 11. Effect of cutting speed and feed rate on tangential force.4. CONCLUSIONS In this study, a detailed experimental investigation is presented for the effects of cutting edge preparation geometry, workpiece surface hardness and cutting conditions on the surface roughness and cutting forces in the finish hard turning of AISI H13 steel. The results have indicated that the effect of cutting edge geometry on the surface roughness is remarkably significant. The cutting forces are influenced by not only cutting conditions but also the cutting edge geometry and workpiece surface hardness. This study shows that the effects of workpiece hardness, cutting edge geometry, feed rate and cutting speed on surface roughness are statistically significant. The effects of two-factor interactions of the edge geometry and the workpiece hardness, the edge geometry and the feed rate, and the cutting speed and feed rate are also appeared to be important. Especially, small edge radius and lower workpiece surface hardness resulted in better surface roughness. Cutting edge geometry, workpiece hardness and cutting speed are found to be affecting force components. The lower workpiece surface hardness and small edge radius resulted in lower tangential and radial forces.5.ACKNOWLEDGMENTS Authors would like to acknowledge Mr. Joseph Lippencott and Talat Khaireddin for their assistance in conducting experiments.REFERENCES 1. N. Narutaki, Y. Yamane, “Tool wear and cutting temperature of CBN tools in machining of hardened steels”, Annals of the CIRP, Vol. 28/1, 1979, pp. 23-28. 2. T. Hodgson, P.H.H. Trendler, G. F. Michelletti, “Turning hardened tool steels with Cubic Boron Nitride inserts”, Annals of CIRP, Vol. 30/1, 1981, pp. 63-66. 3. W. Koenig, R. Komanduri, H. K. Toenshoff, G. Ackeshott, “Machining of hard metals”, Annals of CIRP, Vol.33/2, 1984, pp. 417-427 4. W. Koenig, M. Klinger, “Machining hard materials with geometrically defined cutting edges Field of applications and limitations”, Annals of CIRP, Vol. 39/1, 1990, pp. 61-64. 5. W. 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Evans, “On chip morphology, tool wear and cutting mechanics in finish hard turning”, Annals of the CIRP, Vol.45/1, 1996, pp.77-82. 12. M. A. Elbestawi, A. K. Srivastava, T. I. El-Wardany, “A model for chip formation during machining of hardened steel”, Annals of the CIRP, Vol.45/1, 1996, pp. 71-76. 13. V. P. Astakhov, S.V. Shvets, M.O.M. Osman, “Chip structure classification based on mechanism of its formation”, Journal of Materials Processing and Technology, Vol. 71, 1997, pp. 247-257.摘要本文对H13钢的切削刃几何形状、工件硬度、进料速率和切削速度对表面粗糙度和合力的影响进行了实验研究。将四个因素(硬度、边缘几何、进给率和切削速度)进行二级分数实验，并进行方差统计分析。在硬车削试验中，测量了刀具力的三分量和加工表面的粗糙度。研究表明，工件硬度、切削刃几何尺寸、进料速率和切削速度对表面粗糙度的影响具有统计学意义。边缘几何和工件硬度、边缘几何和进给速率、切削速度和进给速率等两个因素相互作用的影响也显得尤为重要。尤其是减小半径、降低工件表面硬度可获得更好的表面粗糙度。尖端的几何形状、工件硬度和切削速度被视为最具影响力的构件。表面硬度较低、小半径的工件具有较低的边缘切向力和径向力。1.简介 硬车削通常应用于加工硬有色金属零件，在各类文献中有广泛报道。研究结果表明：锯齿形切屑的形成与工艺特点和切削的切屑形状在硬车削中的稳定性机制有关。其他成分的研究显示，其关于CBN刀具的组成、温度和磨损特性的研究及工作材料性能、刀具几何和切削条件对精加工零件表面完整性的影响指出在硬车削过程中遇到的挑战，并识别出影响表面质量、刀具寿命和生产率的各种工艺、设备和模具的相关因素。在查阅文献后,对CBN刀具在硬车削中的影响因素、刀具磨损/破坏、粗糙度、完整性等方面进行了分析，并以图1为例进行了说明。在此图表中，水平虚线上方的参数被视为硬车削过程的因素或输入，只能在开始时选择，除非刀具振动。所有其他参数 (位于这些虚线下面) 被视为硬车削过程的性能度量或输出。对文献的回顾表明，本图中所给出的几乎所有因素都影响了硬车削过程的性能。这些因素可归类如下:图1 一个因素流程图的切削关系1.1刀具几何形状和材料特性硬车削与CBN 切割工具要求谨慎设计工具几何形状。CBN刀具的韧性比其他常用工具材料都低，因此为了提高切削刃的强度，获得成品金属部件的良好表面特性，必须要有适当的边缘准备。为硬车削而设计的CBN刀具，具有负耙几何和边缘准备(倒角或磨刀，甚至两者都有)。边缘准备设计的规格通常是经过广泛试验后确定的。图2显示了CBN刀具常用的边缘准备类型。根据最近的研究，很明显，边缘几何对表面质量的影响是显著的。 切削刃的几何形状和工件的硬度实验表明，硬车削AISI 52100钢的残余应力会影响实验研究结果。他们表示，这两个因素是显著完成硬表面完整性的转向组件。具体地说，他们指出大磨练半径工具产生更多的压应力，但也留下“白层”。本文的研究结论表明，低含量CBN工具生产的切削深度更好的高含量CBN刀具对刀具磨损率的影响较小。图2 预置型号的边缘CBN刀具1.2 工件硬度由于硬化的工件材料的性能的变化，基本的剪切过程和芯片的形成不同的硬车削。先前的研究表明，工件硬度对CBN工具的性能有深刻影响，能够达成加工表面的完整性。在回程过程中，底部煤开采的优势是自由工作面和较小比例技术领先的滚筒切割煤。由此可知由于材料的特定切削能，降低了运输速度的限制。采煤机污水坑在头门附近的中煤层中，不需要调用无效率的循环运动。科学家研究了工件硬度对残余应力的影响。在最近的一项研究中，通过温度控制拉伸试验和正交切削试验研究硬化的52100轴承钢的材料性能，并演示了硬度对材料的影响很大。1.3切削速度、进给速率和切削深度CBN刀具性能的高度依赖切割条件即切削速度、切削率和切削深度。尤其是切削速度、切削深度明显影响刀具寿命。提高切削速度、切削深度导致切削区温度的增加。自从CBN是在高温陶瓷材料,化学因素就变成了一个领先的磨损机理和切削刃经常加速减弱,导致早产(切削刀具的失效),即边缘破损的刀具。此外,泰勒注意到当进给量增加时,残余应力的变化,从抗压抗拉。CBN刀具的性能高度依赖于切削速度、进料量、进料率和切割深度。特别是切削速度和切口深度对刀具寿命有显著影响。切割速度和切割深度的增加，会使切削区的温度升高。由于CBN是一种陶瓷材料，在高温下，化学磨损成为一种常见的磨损机制，往往会加速切削刃的弱化，导致刀具过早失效 (剥落)，即刀具的边缘破损。此外，蒂勒等人注意到，当饲料速率增加时，残余应力会从压缩到拉伸变化。1.4表面完整性，残余应力和刀具磨损一般而言，随着工件硬度的增加，残余应力将会减小。刀具的硬度和断裂韧性随 CBN含量的降低而降低。在陶瓷粘结剂作用下，CBN L 型刀具导热系数较低，导致切削刃在硬车削时温度升高。报告表明，CBN L 工具更适合于完成淬火钢的车削。在低切削速度下，CBN L 的刀具寿命优于 CBN H，而在较高的切削速度下则反之。当使用CBN H工具时，对表面粗糙度的改进也不太有利。大刃磨工具产生的残余应力通常比小刃磨工具所产生的应力更受压缩，而且它们也会留下白色层。此外，边缘几何效应对工件的热塑性变形起着重要的作用。增加饲料率提高压缩残余应力最大，并加深受影响的区域。还有人建议，当与磨砺或锋利的边缘相比时倒角不利于达到的要求的表面光洁度。2. 实验过程2.1 工件材料本研究采用的工件材料为 H13 热工工具钢，适用于高要求模具。本实验所用的圆柱杆 H13 试样直径为1.25 英寸，长度为2英尺。在实验室通过硬化在内部热处理设施，以获得所需的硬度值为50和55的标本。然而，采用未来技术洛克韦尔型硬度计的硬度测试结果表明，各试样的硬度均为51.31.0 和54.70.5。此后，硬度值由实测工件硬度的平均值确定。2.2 工装和边缘的几何形状本文研究了两种具有代表性的边缘制剂的 CBN 刀片，如图2所示。采用高精度触点触发探针，在三复制的协调测量机上测量了珩磨和斜切插入边缘的几何形状。珩磨的刀片平均半径为10.5 4.0m。斜切的插入边缘几何为200倒角和0.1 英寸0.03 毫米倒角，使用宽度相同的仪器与近似到等效的磨练半径101.6 5.1m。采用四大参数实现采煤机截割序列的分类。首先，可以将采煤方法分为两个方向，即从头到尾板以及返回运行，或者只在一个方向上进行分离。其次，采矿序列采用处理面端情况的方式，在提取出等效的切割网后，推进面线，这是每个分离方法的特征参数。不同的序列，也需要时间来完成这项任务。定义序列的另一个参数是每个切割煤的运行比例。传统意义上,采用现代AFC和顶盖港口自动化控制系统是有效的操作使用方法。采煤机截割序列的四个参数识别状态是每个运行创建的开始。2.3 实验设计两级阶乘设计可用来确定的影响工件几何形状、切削刃的硬度、进给速率及切削速度对13钢精轧硬车削表面粗糙度和合力的影响。在表1中概述了各因素和因素水平。这些因素水平导致总共16个独特的因子水平组合。进行了十六次各因子级组合的复制，共进行了256项测试。每个复制表示轴向方向的 25.4 mm 切割长度。响应变量为工件表面粗糙度和切削力。每次试验在轴向力的方向进行，切的长度是25.4毫米。在可用性约束的条件下,每个插入值都被用于一个因素水平组合,其中包括16次重复。(一共有三个磨练和三槽被插入选项)。以这样的方式每个边的准备工作都遵守同样的测试数量和相同的轴向长度。最后,采用工具制造显微镜对CBN刀片进行了检测，通过中断完成硬车削工艺，测量刀具侧面的磨损深度，并检测出刀具边缘的不良特征。2.4 切削力的测量切切削力的测量与三分量力测功器通过一个定制的炮塔适配器安装在炮塔盘上的 CNC 车床上，为刀柄创建一个刚性工装夹具。利用电荷放大器放大测功器产生的电荷信号。通过在便携式计算机上使用数据采集数据，力量数据的时间序列概要显示力量是相对恒定的，裁减的长度和其他因素例如震动和纺锤奔跑是可忽略的。图3显示了合力的三分量。图3 cutting-force元件测量3. 结果和讨论通过方差分析，确定了测量表面粗糙度和切削力数据的统计趋势。分别对表面粗糙度值和切削力的每个分量，即轴向 (进给)、径向 (推力) 和切向 (切削) 力进行了方差分析。此外，还构建了与各方差分析相对应的重要因素。这些块提供了一个更深入的分析模式，研究了与表面粗糙度和切削力的重要因素有关的 H13 钢完成硬车削的斜切。3.1 方差分析结果表2提供了方差分析面粗糙度参数，表明主要影响的边缘几何、切削速度、进给速率之间的相互作用,除了硬度及硬度,边缘加入几何、切削速度、切削速度之间的相互作用具有重要意义和喂入表面粗糙度。进给量是占优势的参数与之关联的表面粗糙度。这是被期望的,因为众所周知,理论表面粗糙度的主要是功能给定的要求,加入不同半径的平方。径向力通常是最大的，完成硬车削中切向力是中间和轴力是最小的。一般而言，切削力元件受切削速度、边缘几何和进给速率的影响。表3-5 分别对应于切削力的径向、轴向 (进给力) 和切线分量的方差分析表。这些表表明，在径向、轴向和切线方向上，工件硬度、边缘几何、切削速度和进给速率 (轴向力除外) 的主要影响都是显著的。表3显示的主要影响的边缘几何、切削速度、硬度和几何学之间的相互作用关系及硬度,边缘切削速度、进给
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