【机械类毕业论文中英文对照文献翻译】刀具磨损
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机械类毕业论文中英文对照文献翻译
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中原工学院毕业设计翻译 刀具磨损为了避免金属切削刀具失效，第三章讲述了它的最低性能要求，即机械性能和耐热性。刀具失效是指过量的磨损会导致刀具失去切削材料的能力。在本章中，文章主要讲述了降低刀具磨损的累积使用特点和机制，它们是最终导致刀具被替代的因素。在现实生产实践中，有一中表示严重磨损程度的连续谱，在这里没有什么要考虑的和可能在实践中北描述为立即失效的两者之间没有明显的边界.在本章和上一章节中有重复的内容。 第二章和第三种的内容表明，金属切削刀具比普通机床轴承表面承受更大的摩擦力、正应力、高温。在大部分情况下，没有办法避免刀具磨损，但是可以研究如何避免加速刀具磨损的方法。刀具磨损的主要因素刀具表面应力和温度（主要取决于金属切削模式车削、铣削、转削）、刀具和工件材料、切削速度、进给量、切削深度和切削液的类型等。在第二章中，主要讲述了影响刀具磨损的因素的微小变化都会导致磨损的变化。机械加工中，刀具磨损方式和磨损率对金属切削操作和切削条件的变化同样敏感。虽然刀具磨损无法避免，但是通常情况下可以控制磨损方式来减少刀具磨损。4.1节中介绍了刀具磨损的主要方式。主要介绍了机械加工的经济型。为了尽量减少制造成本，不仅需要寻找最合适的刀具和工件材料，而且还要考虑切削刀具寿命。在刀具寿命结束时，刀具必须能够替换或者维修以保证加工工件的精度、表面粗造度或者完整性。4.2节主要介绍了刀具寿命的标准和估算。4.1刀具磨损及其分类4.1.1 刀具磨损的形式根据刀具磨损的程度和磨损进程，刀具磨损可分为两类，即磨损和断裂。磨损（如第二章讨论）是一种粗糙材质表面损失或者微接触，或者磨粒较小，最小至分子或者原子的去除机理。它通常会持续进行直到断裂。另一方面，断裂是比磨损更严重的损害，它的发生具有突然性。正如上面所说，从微磨损到严重断裂是一种连续的损害。图4.1显示了一个典型的磨损模式，在这种情况下的磨损一把硬质合金刀具切割处于高速旋转下的金属工件。月牙洼前刀面磨损，前刀面侧翼侧边磨损和在切削深度末端的凹口磨损，它们是磨损的典型方式。磨损量可以用在4.2节中介绍的VB、KT表示。然而磨损量随着切削材料、切削方式和切削条件的变化而变化，如图4.2。如图4.2(a)显示月牙洼和后刀面磨损存在可疑忽略的沟槽磨损，在开机后用硬质合 金刀具切削高速旋转的45钢的条件下。如果改为铣削，一个有裂缝的大幅度月牙洼磨损将成为磨损的显著特点（图4.2（b）。当陶瓷刀具车削镍基超级合金时（图4.2（c）项）在美国商务部线沟槽磨损是主要的磨损模式，而月牙洼和后刀面磨损几乎可以忽略不计。图4.2（d）给出了一个氮化硅陶瓷车削工具切削碳钢的结果。月牙洼和后刀面磨损会在很短的时间内磨损更大。在切削工件材料变为b相态的情况下，大量的切削材料粘附于钛铝合金的K级硬质合金刀具的侧边部分，这样导致刀具磨损断裂或者破碎。 图4.1典型的硬质合金刀具磨损形式（a）车削45碳钢 （b）端面铣削45碳钢（c）车削铬镍铁718 （d）车削45碳钢（e）车削钛合金典型的工具损伤观察磨损和断裂： (a)刀具：烧结碳化物P10， v = 150 m min1,d = 1.0 mm,f = 0.19 mm rev1，t = 5分钟; (b)刀具：烧结碳化物P10， v = 400 m min1， d = 1.0 mm， f = 0.19mm tooth1，t = 5min; (c)刀具： Al2O3/TiC陶瓷刀具，v = 100 m min1，d = 0.5 mm，f = 0.19 mm rev1，t = 0.5分钟;(d)刀具：Si3N4陶瓷刀具，v = 300 m min1，d = 1.0 mm，f = 0.19 mm rev1，t = 1分钟; (e)刀具：烧结碳化物P10，v = 150 m min1 d = 0.5 mm，f = 0.1 mm rev1，t = 2 min。 4.1.2 刀具磨损的原因第2.4章概述了导致磨料，胶粘剂和化学磨损机理的一般条件。在刀具的磨损，这些机理的重要性和发生的条件，可以按切削温度来划分，如图4.3所示。再图上有三个刀具磨损的因素被确定，分别为机械磨损、热磨损和化学磨损。机械磨损包括腐蚀、剥落、早期断裂和疲劳，它基本上与温度无关。热磨损包括塑性变形、热扩散和作为其典型形式的化学反应，它随着温度的急剧增加。 （应当指出，热扩散和化学反应是不是损害的直接原因。相反，它们会导致刀具表面被削弱，使磨损，抗机械冲击或粘连可以更容易造成材料去除。）基于粘附的磨损被观察到有一个在一定温度范围内的局部最大值。 图4.3刀具磨损和切削温度的关系图4.4机械磨损的分类(1)机械磨损根据刀具磨损的程度和磨损进程，刀具磨损可分为两类，即磨损和断裂。磨损（如第二章讨论）是一种粗糙材质表面损失或者微接触，或者磨粒较小，最小至分子或者原子的去除机理。它通常会持续进行直到断裂。另一方面，断裂是比磨损更严重的损害，它的发生具有突然性。正如上面所说，从微磨损到严重断裂是一种连续的损害。无论机械磨损被列为磨损或断裂，它都视磨粒的大小而定。如图4.4所示的几种不同的磨粒大小模式，它们从小于0.1微米达到约100微米（远大于100微米被视为失效）。磨料磨损（如图2.29示意图）通常是由滑动对刀具硬质颗粒的磨损造成的。硬质颗粒无论是来自工作材料的微观结构，还是从切削边缘破碎的颗粒。磨料磨损减少了刀具相对于粒子和一般取决于距离的切削困难（参见4.2.2节）。摩擦磨损发生在磨料颗粒比磨料磨损比较大的情况下。在刀具与工件之间相互滑动运动，并且刀具材料的颗粒或者晶粒被磨损破坏前，刀具材料的颗粒或者晶粒的机械性能被微细裂缝消弱。接下来主要依据破碎片的大小（有时候它由于它的大小限制被称为细微碎片）。这是由机械冲击载荷的规模导致切削力波动大，而不是固有的波动，导致局部应力磨损。最后断裂颗粒比破碎颗粒大，并分为三类：早期阶段、难以预测阶段和最后阶段。削减如果刀具形状或切割的条件是不适当的，或者如果刀具内部存在一些缺陷，或在其边缘有缺陷，这样刀具磨损会立即发生在开始切削工件后。不可预知的断裂可以发生在任何时间段，如果在切削过程中刀具或者工件尖端的压力突然发生变化，例如抖动或不规则的工件表面硬度不均匀所引起。最后阶段断裂可经常被观察到，特别是在铣削过程中并且刀具寿命末端的时候；这些主要是有机械疲劳或者热应力发生在工作部件凸出部分引起的磨损。(2)热磨损塑性变形当刀具处于高温切削状态下时，刀具尖端部分不能承受气条件下正应力，此时热磨损的塑性变形将被观察到，如图4.3所示。因此，发生于刀具处于高温状态下的硬度将作为塑性变形的显著特点。所以例如一般情况下，高速钢刀具及钴含量高的硬质合金刀具或金属陶瓷刀具用于切削条件苛刻的条件下，特别是在高进给速度的情况下。因此，边缘变形将导致生成一个不正确的形状尺寸的工件和快速去除工件材料的情况。(3)热磨损扩散磨损热扩散磨损的结果发生在高温切削条件下，如果刀具和工件材料的元素会扩散到彼此对方的结构中。这是众所周知的硬质合金刀具，并已被研究了多年。例如Dawihl（1941）、特伦特（1952）、Trigger和Chao（1956年）、武山和村田（1963年）、格雷戈里（1965），库克（1973）、上原（1976）、Narutaki和山根（1976年）、Usui et al（1978）和其他科学家。由扩散控制的速率与绝对温度以指数幂的形式成正比。在磨损的情况下，不同的研究者提出了不同的指前因子的因素：库克研究提出了扩散深度h与相应的时间t之间的关系（公式4.1（a）；更早以前，竹山和村田（1963）也研究提出了这些观点，并且更进一步提出滑动距离可能是一个更基本的变量（方程4.1（b）；随后Usui et al. (1978)根据接触力学和被2.4节提及的磨损提出了磨损会随着正接触应力的增加而加剧（公式4.1（c）。在以上所有例子中可知，磨损率的对数与1/将绘制出一条直线，直线的斜率就是C2。 图示4.5火山口与侧面磨损率深度碳素钢转由P20硬质合金,来自Kitagawa(1988) 的研究图4.5显示了月牙洼和两个侧翼的深度为0.25碳含量处的磨损率和0.46碳含量钢，用P20的硬质合金刀具惊醒切削的结果，此实验为了验证方程的方式（4.1c）。图4.5中出现两个线性区域，并且当1/8.510(-4) K(-1)(或1175K)时是一个临界点。在较高温度斜率（1175K）是钢材和水泥之间的碳化物（库克，1973年）扩散过程的典型。在较低温度下斜率是一个随温度变化的机械磨损过程的典型，例如摩擦磨损。扩散可直接显示在静态条件下的高温。如图4.6显示了一个典型静态的扩散试验结果，其中一个P-级硬质合金刀具在1200摄氏度温度下对一个0.15碳钢持续加载30分钟之间通过硬质合金刀具和钢界面在4Nital（一磺酸的合成酒精）蚀刻下，金相部分显示钢珠光体已经从原来的水平增加。这意味着，硬质合金中的碳已扩散到刚里面。此外，电子探针显微分析仪（EPMA）表明，钴和钨已从工具材料也扩散到钢铁中，并且是铁铁扩散到钢刀具材料。许多研究者都认为相互扩散是硬质合金刀具扩（b） 到界面的距离（um）图示4.6 典型的静态扩散试验结果,因为P10耦合至0.15% C钢(Narutaki和Yamane,1976年) （a）通过Nital蚀刻的接口部分;（b）通过电子探针分析元素的扩散 散磨损的原因，但是没有详细的说明，关于这种现象将导致工件材料的去除效果。Naerheim和遄达（1977）提出，对双方碳化钨钴（金级）和WC的磨损率，（钛，钽，钨）的C -钴（P级）硬质合金是由扩散速率控制钨（和Ti和Ta）和碳原子组合成的工作的材料，如图4.7所示。这种观点是基于透射电子显微镜（TEM）对月牙洼磨损的观察，显示在该工具的碳化物颗粒内无一0.01的工具芯片接口毫米的距离的结构变化。对与于P级比K级材料磨损较慢，这是缓慢扩散，它解释了前者比后者的情况。Naerheim和遄达指出，在他们的切削试验中，被拉伸碳化物颗粒并没有在粘附物的底部被观察到。这不是上原的（1976年）的经验。用K级或者P级含碳量为百分之47的刀具进行切削，他收集切屑，并将它溶解在酸性溶液中提取粘结的碳化物，最后让它通过一个0.1mm过滤嘴，通过这种方案进行分类碳化物尺寸。用K -级刀具，他只观察碳化物小于0.1毫米的大小，这与Trent研究结果相一致。然而，用P-级刀具，他观察到碳化物大于0.1毫米大小。这表明K和P型材料不同的磨损机理。扩散磨损的另一个例子是金刚石切割刀具、硅氮化硅陶瓷刀具和SiC晶须增韧氧化铝陶瓷刀具在加工钢时的严重磨损。碳、硅和氮在高温下它们都极容易扩散到铁中，并且氮化硅和碳化硅很容易溶解于铁水。如果一个层作为扩散屏障沉积在刀具上，这样就可以减少硬质合金刀具的扩散磨损热。在实际生产中有两种这样类型沉积层：一个是由涂层刀具提供;另一种是保护性氧化层沉积在切割过程中的磨损表面，用于还原特殊钢（如钙脱氧钢），即通常有belag之称的层。注：文章来源Metal_Machining。8中原工学院毕业设计英文翻译原文 Tool damageChapter 3 considered cutting tool minimum property requirements (both mechanical and thermal) to avoid immediate failure. By failure is meant damage so large that the tool has no useful ability to remove work material. Attention is turned, in this chapter, to the mech- anisms and characteristics of lesser damages that accumulate with use, and which eventu- ally cause a tool to be replaced. In reality, there is a continuous spectrum of damage severities, such that there is no sharp boundary between what is to be considered here and what might in practice be described as immediate failure. There is some overlap between this chapter and the previous one.Chapters 2 and 3 have demonstrated that cutting tools must withstand much higher fric- tion and normal stresses and usually higher temperatures too than normal machine tool bearing surfaces. There is, in most cases, no question of avoiding tool damage, but only of asking how rapidly it occurs. The damages of a cutting tool are influenced by the stress and temperature at the tool surface, which in turn depend on the cutting mode for exam- ple turning, milling or drilling; and the cutting conditions of tool and work material, cutting speed, feed rate, depth of cut and the presence or not of cutting fluid and its type. In Chapter 2, it was described in general that wear is very sensitive to small changes in sliding conditions. In machining, the tool damage mode and the rate of damage are simi- larly very sensitive to changes in the cutting operation and the cutting conditions. While tool damage cannot be avoided, it can often be reduced if its mode and what controls it is understood. Section 4.1 describes the main modes of tool damage.The economics of machining were introduced in Chapter 1. To minimize machining cost, it is necessary not only to find the most suitable tool and work materials for an oper- ation, but also to have a prediction of tool life. At the end of a tools life, the tool must be replaced or reground, to maintain workpiece accuracy, surface roughness or integrity. Section 4.2 considers tool life criteria and life prediction.4.1 Tool damage and its classification4.1.1 Types of tool damageTool damage can be classified into two groups, wear and fracture, by means of its scale and how it progresses. Wear (as discussed in Chapter 2) is loss of material on an asperity or micro-contact, or smaller scale, down to molecular or atomic removal mechanisms. It usually progresses continuously. Fracture, on the other hand, is damage at a larger scale than wear; and it occurs suddenly. As written above, there is a continuous spectrum of damage scales from micro-wear to gross fracture.Figure 4.1 shows a typical damage pattern in this case wear of a carbide tool, cutting steel at a relatively high speed. Crater wear on the rake face, flank wear on the flank faces and notch wear at the depth of cut (DOC) extremities are the typical wear modes. Wear measures, such as VB, KT are returned to in Section 4.2.Damage changes, however, with change of materials, cutting mode and cutting condi- tions, as shown in Figure 4.2. Figure 4.2(a) shows crater and flank wear, with negligible notch wear, after turning a medium carbon steel with a carbide tool at high cutting speed. If the process is changed to milling, a large crater wear with a number of cracks becomes the distinctive feature of damage (Figure 4.2(b). When turning Ni-based super alloys with ceramic tools (Figure 4.2(c) notch wear at the DOC line is the dominant damage mode while crater and flank wear are almost negligible. Figure 4.2(d) shows the result of turning a carbon steel with a silicon nitride ceramic tool (not to be recommended!). Large crater and flank wear develop in a very short time. In the case of turning b-phase Ti-alloys with a K-grade carbide tool, large amounts of work material are observed adhered to the tool, and part of the cutting edge is damaged by fracture or chipping (Figure 4.2(e).4.1.2 Causes of tool damageChapter 2.4 outlined the general conditions leading to abrasive, adhesive and chemical wear mechanisms. In the context of cutting tool damage, the importance and occurrence of these mechanisms can be classified by cutting temperature, as shown in Figure 4.3. Three causes of damage are qualitatively identified in the figure: mechanical, thermal and adhesive. Mechanical damage, which includes abrasion, chipping, early fracture and fatigue, is basi- cally independent of temperature. Thermal damage, with plastic deformation, thermal diffu- sion and chemical reaction as its typical forms, increases drastically with increasing temperature. (It should be noted that thermal diffusion and chemical reaction are not the direct cause of damage. Rather, they cause the tool surface to be weakened so that abrasion, mechanical shock or adhesion can then more easily cause material removal.) Damage based on adhesion is observed to have a local maximum in a certain temperature range.Mechanical damage Whether mechanical damage is classified as wear or fracture depends on its scale. Figure 4.4 illustrates the different modes, from a scale of less than 0.1 mm to around 100 mm (much greater than 100 mm becomes failure).Abrasive wear (illustrated schematically in Figure 2.29) is typically caused by sliding hard particles against the cutting tool. The hard particles come from either the work mater- ials microstructure, or are broken away from the cutting edge. Abrasive wear reduces the harder is the tool relative to the particles and generally depends on the distance cut (see Section 4.2.2).Attrition wear occurs on a scale larger than abrasion. Particles or grains of the tool material are mechanically weakened by micro-fracture as a result of sliding interaction with the work, before being removed by wear.Next in size comes chipping (sometimes called micro-chipping at its small-scale limit). This is caused by mechanical shock loading on a scale that leads to large fluctuations in cutting force, as opposed to the inherent local stress fluctuations that cause attrition.Finally, fracture is larger than chipping, and is classified into three types: early stage, unpredictable and final stage. The early stage occurs immediately after beginning a cut if the tool shape or cutting condition is improper; or if there is some kind of defect in the cutting tool or in its edge preparation. Unpredictable fracture can occur at any time if the stress on the cutting edge changes suddenly, for example caused by chattering or an irreg- ularity in the workpiece hardness. Final stage fracture can be observed frequently at the end of a tools life in milling: then fatigue due to mechanical or thermal stresses on the cutting edge is the main cause of damage.Thermal damage plastic deformationThe plastic deformation type of thermal damage referred to in Figure 4.3 is observed when a cutting tool at high cutting temperature cannot withstand the compressive stress on its cutting edge. It therefore occurs with tools having a high temperature sensitivity of their hardness as their weakest characteristic. Examples are high speed steel tools in general; and high cobalt content cemented carbide tools, or cermet tools, used in severe conditions, particularly at a high feed rate. Deformation of the edge leads to generation of an improper shape and rapid material removal.Thermal damage diffusionWear as a result of thermal diffusion occurs at high cutting temperatures if cutting tool and work material elements diffuse mutually into each others structure. This is well known with cemented carbide tools and has been studied over many years, by Dawihl (1941), Trent (1952), Trigger and Chao (1956), Takeyama and Murata (1963), Gregory (1965), Cook (1973), Uehara (1976), Narutaki and Yamane (1976), Usui et al. (1978) and others. The rates of processes controlled by diffusion are exponentially proportional to the inverse of the absolute temperature q. In the case of wear, different researchers have proposed different pre-exponential factors: Cook (1973) suggested depth wear h should increase with time t (equation 4.1(a); earlier, Takeyama and Murata (1963) also suggested this and the further possibility of sliding distance s being a more fundamental variable (equation 4.1(b); later Usui et al. (1978), following the ideas of contact mechanics and wear considered in Chapter 2.4, proposed wear should also increase with normal contact stress sn (equation 4.1(c). In all these cases, a plot of ln(wear rate) against 1/q gives a straight line, the slope of which is C2 igure 4.5 shows experimental results for both the crater and flank depth wear rates of a 0.25%C and a 0.46%C steel turned by a P20 grade carbide tool, plotted after the manner of equation (4.1c). Two linear regions are seen: in this case the boundary is at 1/q 8.5 104 K1 (or q 1175 K). The slope of the higher temperature data (q 1175 K) is typi- cal of diffusion processes between steels and cemented carbides (Cook, 1973). The smaller slope at lower temperatures is typical of a temperature dependent mechanical wear process, for example abrasion. Diffusion can be directly demonstrated at high temperatures in static conditions. Figure 4.6 shows a typical result of a static diffusion test in which a P-grade cemented carbide tool was loaded against a 0.15% carbon steel for 30 min at 1200C. A metallographic section through the interface between the carbide tool and the steel, etched in 4% Nital (nitric acid and alcohol) shows that the pearlite in the steel has increased from its original level. This means that carbon from the cemented carbide has diffused into the steel. Furthermore, elec- tron probe micro-analysis (EPMA) shows that Co and W from the tool material also diffuse into the steel; and iron from the steel diffuses into the tool material. Many researchers agree that mutual diffusion is the cause of carbide tool diffusion wear, but there is not agreement in detail as to the mechanism that then results in material removal.Naerheim and Trent (1977) have proposed that the wear rates of both WC-Co (K-grade) and WC-(Ti,Ta,W)C-Co (P-grade) cemented carbides are controlled by the rate of diffusion of tungsten (and Ti and Ta) and carbon atoms together into the work material, as indicated in Figure 4.7. This view is based on
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