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河南理工大学本科毕业设计（英文翻译）研究工程陶瓷的钻石工具钻孔 Q.H. Zhanga, J.H. Zhanga, D.M. Sunb, G.D. Wangca中国济南250061精实路73号山东大学机械工程系,b中国济南山东大学材料工程系 c中国济南机械设计与研究院摘要：应用钻石工具在工程陶瓷上钻孔的技术已经形成。 在这个方法中，钻孔工具通过摩擦力而旋转。钻孔机械的机制是基于被分析过的断裂力学概念以及一种关于物质清除率的理论模型。 按照这个模式，通过增加静态载荷应力、钻探工具的转速以及磨料的颗粒大小可以增大物质清除率。选择含有99.5Al2O3的陶瓷作为研究物质进行了实验。结果显示，钻石钻孔在工程陶瓷制造上是一种有效的方法。关键字：工程陶瓷； 钻石工具；钻井； 机械机制1.前言工程陶瓷有许多良好的物理和机械特性：高硬度、高热能阻力、化学稳定性高、低导热和电气热等等。由于具有这些特性，工程陶瓷越来越多的应用于一些高技术领域,从电子和光学器件发热到穿抗零件1-3都有应用。但是直到今天,他们大多仅限于应用光学、电子仪器的应用。原因之一是：烧结之前的形成过程具有限制，这一过程中的限制和复杂几何难以确保有足够的准确性和表面的完善性。另外，在目前的使用过程中，也有相当的逆差生产或者在烧结过程中强硬的机械几何作用，加上系统本身的限制以及大多数程序中的能力形成都是限制因素。制造工程陶瓷的最早规模是通过传统方法，这种方法非常的费时费力。强大的压缩力和接受力，以及可以接受的表面和地表的破坏在某种程度上是一个巨大损失。因此，近些年里，在这一领域中的研究已经开始应用更有效的替代物质程序来获得动力，尤其是如何减少发生故障或表面裂缝的工程陶瓷4-6的制作途径和方法上。本文通过使用扶轮钻石工具来研究一种在工程陶瓷上的机械钻孔方法，它能提高物质清除率，并且可以改善表面完善性。本文将要探讨基本机制钻钻石工具在陶瓷钻孔上的知识，从而使提高预测物质迁移率而计算的静态负载应力，摩擦力的表面积和钻孔工具的合理转速。2.钻石工具钻孔的机制钻石工具钻孔过程概略图如图1所示。这个工具在钻孔过程是旋转的，工件是固定装置的。物质迁移的微观机制已通过观察钉磨损的表面得到了普遍调查。物质迁移过程被认为是类似于一个切割工具，在任何情况下，可以取代单人工具或部分工具或破裂的颗粒表面的工作。该工件物质被认为是一件刺的方式很多部分颗粒磨料上应用。由此得到的结论是,工程陶瓷的脆性断裂出现主要在钻石钻探工具。理解了这一进程,有利于掌握脆性材料的相似性，由于磨料颗粒在工件表面类似于硬度实验中压头的工作。 图1.钻石工具钻孔进程的概略图：(1)大件，(2)水，(3)工件， (4)工具， (5)进水外壳。2.1陶瓷凹槽的研究通过维克压头在陶瓷正常接触的情况下的变形和断裂的说明如图2所示。 图2 基于凹槽的陶瓷的正常的变形和断裂直接的说这一个区域是压变形。两大裂缝系统已经确定，它们是来自区塑胶:中/测裂缝和横向裂缝。 这两种行为的裂缝的残余变形的弹性来自塑料/塑料材料。径向裂缝是由一个楔子固定着在运行时，这样可以继续发挥在卸货条件下由于剩余张力而形成的力。横向裂缝向下展开，强调只有在剩余的负荷被替换的条件下，才会发生辐射,伴随着横向裂缝将大大促进物质迁移的过程。 如如图 2所示，在最后发生辐射和横向裂缝是最易导致材料变脆的。一种主要的力Pc在辐射断裂时的反应可以这样描述7： 在此是量纲几何因素有关的压、断裂韧性，KIC是工件的断裂紧固性，而Hv是工件材料的维克硬度。 由直径或裂缝的辐射数Cr和横向裂缝CL，分别可以依据如下等式得出8： 其中P是承压应力，而1和2是比例常数。 人们普遍认为横向裂缝深度Ch是的一部分： 其中是39中的比例常量。 从以上的数据中我们可以得到这样的结论，位/径向的尺寸大小或横向裂缝的变化是随着负荷的不断增加和工件材料断裂韧性的不断减少。到目前为止，研究的结果对理解实际的钻石工具在工程陶瓷钻孔过程提供了有用的信息。2.2. 物质清除率和不同参数之间的关系根据陶瓷凹槽的测试结果表明，由于单一物质磨损而引起一种模型物质清除率的边已经达到了论证，正如图3中所示。 图3 切削形成过程的概略图模型仅考虑沿着表面线性案子的磨料类型。假定单个磨料循线道路，伴随着深度不断降低、工件材料体积被装置替换为磨料(压)在正常负荷P比例大小的横向裂缝长度和输送长度d 。清除材料的数量V0件,这样得到的结果 (见图 4): 图4 钻孔工具内表面的该略图 其中CL是在横向裂缝长度，Ch是横向裂缝深度，d代表运动距离。 然后，为一种物质清除率所给出的数值是： 其中是工具的转速，r是裂缝轨道的半径。 假设有效切削颗粒的密度是，颗粒的有效面积是dA(见图 4)： 然后,工具的物质清除率是： 工具表面的有效颗粒数量是10: 其中R1是钻石钻孔工具的外半径，R2是钻石钻孔工具的内半径，K1是比例常数不变；Vg是磨损颗粒的速度，d0是磨损颗粒的平均直径。然后: 在一个磨损颗粒中的承压运动是： 把等式（2），（3），（9），（10）代入等式（7）中： 把等式（11）简化为： 其中K是比例常数不变。 根据等式(12)，物质迁移率Mv将会增加,主要是通过增加静态负载应力W，工具的旋转速度和磨损颗粒的大小d0。3. 实验程序对钻机进行了试验。钻石钻孔工具的设计是为了接受冷却(见图 1)，是一种特殊的钻石轮外部半径R2=10毫米，内部半径R1=6毫米。我们准备了三类钻石钻孔工具，而它们的粒度分别是80、120和160，而它们的集合率都是100%。选择含有99.5%Al2O3的陶瓷作为研究对象，水作为冷却材料。精确度的衡量一个通过千分表，准确度为毫米。钻孔深度每分钟可以衡量一个千分表，然后才能计算物质清除率，(物质清除率的截面积是钻孔工具乘以钻孔工具每分钟钻的深度). 表面粗糙度的测量用(英格兰)4度量，具有5%的误差度。4. 实验结果和讨论 4.1 静态负荷的影响试验结果表明，随着静态负荷的增加，物质迁移率趋向增加，正如图5所示，这和等式(12)很相似。 经研究发现表面粗糙度略受静载荷应力的影响，它随着静电负荷的增加而提高。目前的实验已在下列条件下进行： =7.20 rev/min，C=80。 在静态载荷W为25、35、45、55、65N时，表面粗糙度（Ra）分别时0.0040、0.0040、0.0042、0.0045、0.0045毫米。 图5 静态负荷的影响4.2 钻孔工具转速的影响图6中显示了钻孔工具在不同转速下得到的物质清除率的效果。还有其他的因素影响物质清除率，例如裂缝部位的切屑和磨损颗粒的自我完善。物质清除率与钻孔工具的转速并不都是一致。对切削提高物质清除率是非常重要的。由于越来越多的转速的钻探工具，不少切屑形成，来越难走冲。这也将影响磨损颗粒的自我完善。一般来说，自我完善包括两个部分，磨损颗粒通过逐步分割而自我完善和通过整体的分开而自我完善。当切屑不能完全用水冲走，整体和磨损颗粒难以分割，影响到钻孔工具的效率：从而物质清除率将会受到影响。此外，切屑与冲的冷却压力也会有所影响。在本实验中的冷却压力是2.0*104Pa，在这种情况下，当钻孔工具的转速达到1200rpm时，负荷就会发生。 图6 钻孔工具转速的影响4.3 颗粒大小的影响根据等式(12)，物质迁移率的增加将会随着颗粒大小的增加而增加，这是由测试结果论证得到的，如图7所示。 图7 颗粒大小的影响磨损颗粒的大小将大大影响表面粗糙度。表面粗糙度主要取决于磨损颗粒的大小。颗粒越大，制成品的表面越粗糙。最近实验的完成是根据以下条件：W=55N， =720rev/min. 当C是80、120和160时，对应的表面粗糙度(RA)分别是0.0045、0.0040和0.0020mm。5. 结论 本文主要对钻石钻孔工具在陶瓷方面的基本机制做了研究，对材料清除率的影响因素做了探索。试验结果表明不论时增加静态负荷，提高钻孔工具的转速，还是增大磨损颗粒的面积，都会达到增加物质迁移率的效果。关系粗糙度制成品表面的粗糙度和各参数的关系是：提高静态负荷，减少转速，提高磨料颗粒大小都会使成品表面粗糙度增加。参考资料1 R.W.Davidge 巴黎陶瓷机械行为.剑桥大学出版社,剑桥,1979年 2 T.Warren.陶瓷地面:一般模式及制造,并拟转型脆模型.38(4) (1998) 257-275. 3 S.Reschke,C.Bogdanow 陶瓷工程:新观点通过增值(多)功能. 175-176 (1999)1-10. 4 K.Uematsu,T.Mishiro,新机使用方法陶瓷超音波激荡工具, (1)42 (1993)375-378. 5 K.P. Rajurkar,Z.Y.Kuppattan、微型陶瓷材料拆除(研究所)的精密超音波机械 23(1999)73-70.6 K.Sugita,T.Hiraga .组成办法清除机制陶瓷材料 (1)40(1991)61-64. 7 A.G.Evans, D.B.Marshell基本摩擦机械材料1981,PP. 439-442. 8 I.A.Markov 超声机械与材料, 1966年. 9 M.Komaraiah,P.N.Reddy,研究影响产业超音波机械装置代理.美国 (3)33 (1993)495-505. 10 U.Kuniaki,E.Kazuhito超声磨削试验建筑机械设备及特色 (1)52 (1986)107-113.10Study on the diamond tool drilling of engineering ceramicsQ.H. Zhanga,*, J.H. Zhanga, D.M. Sunb, G.D. WangcaCollege of Mechanical Engineering, Shandong University, No. 73, Jingshi Road, Jinan 250061, PR ChinabCollege of Material Engineering, Shandong University, Jinan, PR ChinacShandong Machine Design and Research Institute, Jinan, PR ChinaReceived 27 December 2000AbstractA method for drilling holes in engineering ceramics by using a diamond tool has been developed. In this method, a drilling tool rotates withfixedabrasives.Themachiningmechanismofdrillingbasedonthefracturemechanicsconceptisanalyzed,andanewtheoreticalmodelofthematerial removal rate is proposed. According to this model, the material removal rate increases in accordance with the increase of the staticload applied, the rotational speed of the drilling tool, and the grain size of the abrasive. Selecting 99.5% Al2O3ceramics as the workpiecematerial, experiments have been carried out. The results show that diamond drilling is an effective method for machining engineeringceramics. # 2002 Published by Elsevier Science B.V.Keywords: Engineering ceramic; Diamond tool; Drilling; Machining mechanism1. IntroductionEngineering ceramics have numerous excellent physicaland mechanical properties: high hardness, high thermal resi-stance, chemical stability, and low thermal and electricalconductivity, to name but a few. Because of these specialqualities, engineering ceramics are expected to be usedincreasingly in a number of high-performance applicationsranging from electronic and optical devices to heat- andwear-resistant parts 13. Until today, their applicationshave mostly been limited to electronic and optical devices.One reason is to be found in the limitation on the formingprocess prior to sintering, which restricts the generation ofcomplex geometry and makes it difficult to ensure adequateaccuracy and surface finish. There is also a considerabledeficit in terms of the production or machining of morecomplex geometries in the hardened post-sintering state,with limitations on either the performance or the formingcapacity of the majority of the processes in current use.Machining engineering ceramics to final dimensions byconventional methods is extremely laborious and time con-suming. Tight tolerances and dimensions with acceptablesurface and sub-surface damage are something only attain-able at great cost. Thus research into the areas of moreefficient material removal processes have been beginning togathermomentum inrecent years,especiallyinthewaysandmeans of reducing the occurrence of faults or cracks in thesub-surface of the machined ceramics 46.A kind of machining method for drilling holes in engi-neering ceramics by using a rotary diamond tool is proposedin this paper. It can increase the material removal rate, andimprove the surface finish.This paper intends to further the understanding of thebasic mechanisms the diamond tool drilling of ceramics andthus to enable the prediction of the material removal rate interms ofthestaticload applied,thegrainsizeofthe abrasive,and the rotational speed of the drilling tool.2. The mechanism of diamond tool drillingThe process of diamond tool drilling is shown schemati-cally in Fig. 1. The tool is rotating in the drilling process, theworkpiece is stationary. The material removal mechanismhas been investigated generally by microscopic observationof the abraded surface. The process of material removal isthought to be similar to that of a single tool cutting in that inall cases material is removed by an individual tool or particledisplacing or fracture the work surface. The workpiecematerial is found to be stabbed off in the form of manyminute particles by the abrasive grains grinding.It is concluded that the removal of engineering ceramicoccurs primarily by brittle fracture in diamond tool drilling.Tounderstandthisprocess,itishelpfultostudytheindentationJournal of Materials Processing Technology 122 (2002) 232236*Corresponding author.E-mail address: (Q.H. Zhang).0924-0136/02/$ see front matter # 2002 Published by Elsevier Science B.V.PII: S0924-0136(02)00016-Xof brittle materials, because the abrasivegrains acting on theworkpiece surface are just like indenters.2.1. Investigation of indentation in ceramicsThe deformation and fracture pattern observed under thenormal contact of ceramics by a Vickers indenter is illu-strated in Fig. 2. Directly under the indenter is a zone ofplastic deformation. Two principal crack systems have beenidentified, which emanate from the plastic zone: median/radial cracks and lateral cracks. The behavior of both typesof cracks is effected by residual stresses from the non-uniform plastic deformation in the elastic/plastic material.Radial cracks are initiated by a wedge-like action duringloading, and they may continue to propagate during unload-ing due to residual tensile stresses acting on the crack-tip. Lateral cracks are observed to initiate and propagateby residual stresses only as the indenting load is removed.The initiation and propagation of radial as well as lateralcracks are considered to contribute greatly to the materialremoval process. As shown in Fig. 2, the initiation andpropagation of these radial and lateral cracks at the end leadto chipping of the brittle material. A critical load Pcforinitiating a radial crack is given by 7:Pc aK4ICH3V(1)where a is a dimensionless factor related to the indentergeometry, KICis the fracture toughness of workpiece, andHVis the Vickers hardness of the workpiece material.For the size of the median or radial crack Crand lateralcrack CL, respectively, the following equations have beenderived 8:Cr x1P1=2H1=4VK1=3ICCL x2PKIC?3=4(2)where P is the load applied, and x1and x2are proportionalconstants.It is generally regarded that the depth of the lateral crackChis proportional to P=HV1=2:Ch x3PHV?1=2(3)where x3is a proportionality constant 9.It is concluded from these results that the size of themedian/radial or lateral crack grows with an increase inthe load and with a decrease in the fracture toughness ofthe workpiece material. Investigations on indentation des-cribed so far provide useful information for understandingthe practical diamond drilling process of ceramics.2.2. The relationship between the material removal rateand various parametersAccording to the test results of ceramics in indentation, amodel of material removal caused by a single abrasive isproposed, as shown in Fig. 3. The model takes into accountthe linear tangential motion of the abrasive along the sur-face. Assuming that an individual abrasive grain follows alinear path with a constant depth of cut, the volume ofworkpiece material removed by an abrasive grain (indenter)under a normal load P is proportional to the dimensions ofthe lateral crack and the length of travel d. The volume ofFig. 1. Schematic diagram of the diamond tool drilling process: (1) chuck,(2) water, (3) workpiece, (4) tool, (5) water jacket.Fig. 2. Localized deformation and fracture of ceramics due to indentation.Fig. 3. Schematic model of chip formation.Q.H. Zhang et al./Journal of Materials Processing Technology 122 (2002) 232236233removed workpiece material V0for one grain is obtained as(see Fig. 4):V0 2CLChd(4)where CLis the length of the lateral crack, Chis the depth ofthe lateral crack, d is the acting distance of the grain.Then, the material removal rate for one grain is given by:MV0 4pCLChor(5)where o is the rotational speed of the tool, and r is the radiusof the grains track.Assuming that the density of the effectivecutting grains isl, the number of effective grains in area dA (see Fig. 4) is:n ldA 2lpr dr(6)Then, the material removal rate of the tool is:MVZR2R18p2lCLChor2dr 83p2lCLChoR32? R31(7)The number of effective grains in the terminal face of thetool is 10:N lA K1d206ugp?2=3pR22? R21(8)where A pR22? R21, R2is the external radius of thediamond drilling tool, R1is the internal radius of thediamond drilling tool, K1is proportionality constant; ugisthe concentration of abrasive grains, and d0the meandiameter of the abrasive grains. Then:l K1d206ugp?2=3(9)The load acting on a single abrasive grain is:P WN Wd20pK1?6ugp?2=3R22? R21?1(10)Substituting Eqs. (2), (3), (9), (10) into Eq. (7):MV83p3=4x1x2od20K1?1=46ugp?1=6? K?3=4ICH?1=2VW5=4R32? R31R22? R215=4(11)Eq. (11) can be simplified to:MV Kd1=20u?1=6gK?3=4ICH?1=2VoW5=4(12)where K is a proportional constant.According to Eq. (12), the material removal rate MVwillbe increased with the increase of the applied static load W,the rotationalspeed ofthe tool o,and the size ofthe abrasivegrains d0.3. Experimental procedureExperiments were performed on a drilling machine. Thediamond drilling tool, which was especially designed toaccept coolant (see Fig. 1), was a special diamond wheelwith a external radius of R2 10 mm and an internal radiusof R1 6 mm. Three types of diamond drilling tool wereprepared, their grits being 80, 120, and 160, and theirconcentrations were being 100%.A 99.5% Al2O3ceramic was selected as the workpiecematerial and water was selected as the coolant.The MRR is measured through a dial gauge with anaccuracy of 0.001 mm. The depth of drilling per minutecan be measured with a dial gauge, and then the MRR canbe calculated (The MRR is the cross-sectional area of thedrilling tool multiplied by the depth of drilling per minute.).The surface roughness is measured using a Talysurf 40(England) surface measuring instrument with a relativeaccuracy of 5%.4. Experimental results and discussion4.1. The effect of the static loadTest results show that the material removal rate tends toincrease with the increase of the static load, as shown inFig. 5, which is similar to Eq. (12).The surface roughness is found to be slightly affected bythe applied static load, increasing with the increase of thestatic load. The present experiments were conducted underFig. 4. Schematic diagram of the terminal face of the drilling tool.Fig. 5. The effect of the static load.234Q.H. Zhang et al./Journal of Materials Processing Technology 122 (2002) 232236the following conditions: o 720 rev/min, C 80. Whenthe static load W is 25, 35, 45, 55, 65 N, the surfaceroughness (Ra) is 0.0040, 0.0040, 0.0042, 0.0045, and0.0045 mm, respectively.4.2. The effect of the rotational speed of the drilling toolFig.6showstheeffectoftherotationalspeedofthedrillingtool on the MRR. An increase of the rotational speed of thedrillingtoolcausesanincreaseintheMRR.Astherearesomeother factors affecting the MRR, for example the flushing ofswarf and the self-sharpening of abrasive grains, the MRR isnot proportional to the rotational speed of the drilling tool.It is very important for high material removal rate to flushaway the swarf. With the increase of the rotational speed ofthedrillingtool,alotofswarfisformed,andflushingitawaybecomes increasingly more difficult. This will also affectthe self-sharpening of the abrasive grains. Generally speak-ing, self-sharpening of abrasive grains include two compo-nents, self-sharpening through progressive abrasive grainfragmentation and self-sharpening through progressivebonderosion. When the swarf is not completely flushed away,bond erosion and abrasive grain fragmentation becomedifficult, resulting in the dulling of the drilling tool: thusthe MRR will be affected. Additionally, the flushing ofswarf is related to the pressure of the coolant. In the presentexperiments, the pressure of the coolant is 2:0 ? 104Pa.Under this condition, loading occurred when the rotationalspeed of the drilling tool was 1200 rpm.The surface roughness decreases with an increase of therotational speed of the drilling tool. The present experimentswere conducted under the following conditions: W 55 N,C 80. When the rotation speed o is 520, 720, 900 and1120 rev/min, the surface roughness (Ra) is 0.0055, 0.0045,0.0042, and 0.0042 mm, respectively.4.3. The effect of the grain sizeAccording to Eq. (12), the material removal rate willincrease with the increase of the grain size, and this isconfirmed by the test results, as shown in Fig. 7.The size of the abrasive grain can greatly affect thesurface roughness. The surface roughness depends mainlyon the size of the abrasive grains. The greater is the grainsize, the rougher is the finished surface. The present experi-ments were conducted under the following conditions:W 55 N, o 720 rev/min. When the C is 80, 120, and160, the surface roughness (Ra) is 0.0045, 0.0040, and0.0020 mm, respectively.5. ConclusionsThe basic mechanism of the diamond tool drilling ofceramics has been studied, and the effect on the materialremoval rate has been explored. The test results showthat any increase in terms of the static load applied, therotational speed of the drilling tool, and the size of abrasivegrains, results in an increase of the material removal rate.The relationship between th