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3062 锂电池卷绕机卷绕机构,3062,锂电池卷绕机卷绕机构,锂电池,卷绕,机构
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毕业设计翻译译文题目名称： 锂电池卷绕机卷绕机构 院系名称： 机 电 学 院 班 级： 机 自071班 学 号： 200700314114 学生姓名： 袁 欣 锋 指导教师： 邓 大 立 2011 年 3月- 1 -中原工学院毕业设计翻译译文2.2.2 切屑的几何形状和影响因素图2-1显示了100年以前切屑的形状。图2-4显示了很多现代的切屑图像，这些图像由修饰、刻画快停下截面得到（这个方式在第五章叙述）。它显示了切屑的大范围滑移，它依靠材料和切削条件而自由形成的。所有这些切屑用刀尖形成，切屑斜面贴近切削刀具。待续而又稳定的切屑信息从图2-4（a）中可以看到（同样在图2-2中也有出现）。这个是70/30黄铜的实例，都知道对于机器来说它很容易加工的一种材料。一些材料但能够形成很多段，或锯齿形切屑（如不锈钢图2-4（b）。其它的则很难形成连续的切屑，取而代之的是非连续的切屑。图2-4（C）（对黄铜来说，通过增加引导形成易碎的切屑）和图2-4（d）（低碳钢来说，以一般速切削）分别显示了不连续切屑发生了少量的和大量的塑性变形。但在其它情况下（低碳钢以一般的速度切削图2-4（e）工件做成圆棒料，切屑将沿着刀具边缘脱落，刀具与工件接触边缘，抵抗负载和产生切削热。随着切削，蕅温度和断增加。刀具与工件接触处不能存在（或者不能在前刀面形成。）图2-4（f）（调质钢以高速切削）显示了薄层切削时切屑的形状，不同于图2-4（a）图的形状。这章将要联系最简单类型的切屑形成，连续的切屑通过锋利的前刀面处形成。更进一步，只有直角的情况（2-2-1节）将被考虑。机械学的角色是显示压力和速度的边界条件。刀具接触面和工件材料机械特性决定切屑的流动和压力。连续切屑的形成，切屑最终的流动意味着至少决定于切屑的厚度，它与刀具的长度和弯曲有着联系，这些都不是单单的由刀具的形状而确定。事实上，切屑的形状仍是力学的主要挑战。一旦切屑的形状已知，决定切屑压力的相对比较简单。工件与刀具之间的压力和温度，将影响刀具的寿命和工件的表面粗糙度。它的决定因素有点困难。 （a）（b） （c）（d） （e）（f）图2-4 切屑以0-15mm的速度从车床流出切削速度以m/min表明：（a）70/30黄铜（50）,（b）奥氏体不锈钢（30）,（c）加铅黄铜（120）,（d）低碳钢（5）,（e）低碳钢（25）,（f）低碳钢（25）。图2-5 切屑流（a）大略的从图2-4（a）；（b）简化的和它的速度图表（c）影响切屑流动的主要因素是刀具的倾斜角。切屑与刀具之间的摩擦和硬化的工件材料形成切屑。一些建立在典型工程量的实验观察结果将被呈献，但是这里首先将介绍流动的一些必要的符号和通用的简化（这些内容在第六章将被移除）。图2-5（a）是图2-4（a）的一个草图。它显示了用一个倾斜角为的刀具形成切屑的厚度t，而从未变形厚度f的一个过程。刀具的关联长度OB为l和切屑的弯曲半径为r。塑性变形区用图中画出的影线标记出来。最主要的变形区也就是主要的切除区，存在于线OA的附近。进一步的变形材料经常被与其紧挨的前刀面保护起来。在副切削区域，一个简化的积屑流（图2-5（b）用一个平面取代主要的区域。剪切平面OA和忽略增加的畸形区域（尽管区域中的材料仍在塑性极限之内）。图2-5（b）显示了剪切平面OA与切削方向倾斜角为。被称为剪切平面角。因为剪切平面OA能由f/sin或者由t/cos(-)得到。 (2-2) 图2-5也标识了速度的变化，Uprimary，它发生在主切削平面，由Uwork转变到Uchip它进一步显示了压力R负责切屑的流动，其中对前刀面倾斜一个摩擦角（tan=摩擦系数）和对切削平面OA倾斜一个（-+）角度。它还引入其它的工程量，后面的内容将要提到。等级Uprimary和Uchip结果，相对Uwork能从简化的流动速度图表中找到（图2-5（c）。 （2-3）剪应变发生在切屑的形成过程，它对零件的主切削速度是垂直于切削平面的工件速度的几倍。相同的拉紧是这个的1/倍（附录1）。联合方程（2-3）和方程（2-2），等效应变是： （2-4a）结果，变形的程度由，（-）和切屑厚度的比（t/f）决定。的比也将会看到，它的值常常在0.9到1.3之间变动。所以 （2-4b）Mallock的观察中，切屑厚度受前面已经提到的润滑油影响很大，图2-6显著地阐明这点。它是前角为30度的发具以低速（远低于1m/min的速度）切削铁时的一个快速停止视图。在大气中，形成的切屑厚而直。增加润滑油液体导致切屑变的薄而卷曲。在这种情况下，增加润滑油导致切屑与刀具之间的摩擦系数变成从0.57到0.25（Childs，1972）。（a） （b）图2-6铁以低速切削加工：（a）干（在空气中）和（b）四氯化碳应用到前刀面图2-7（a）铜加工收集的数据，干燥()和润滑（o）；和（b）切削速度大约为1m/min时，润滑油变化的影响情况在这个研究中，使用四氯化碳液体润滑油，CCl4，早期研究员发现用液体是一种最有效的减小摩擦的方法。尽管如此，它有毒且今天已不推荐使用。另外四氯化碳只在低速度切削时起到降低摩擦的效果。图2-7带来切削铜时，几种来源的润滑液，共同作用时的结果。在图2-7（a）它显示了，在空气中和在四氯化碳中以从1到100m/min的切削速度，测量所得到的摩擦系数，它的吃刀量在0.1和0.5mm之间且刀具的刀面角在6度到40度之间。以高一点的速度时，四氯化碳液体润滑油减小摩擦的效果已经消失了，不再起作用。Mallock很是迷惑怎样使润滑油渗入到切屑与刀具之间。润滑油怎样在金属切削过程中起作用将在2-4-2节考虑。在图2-7（a）中，对任一的速度和润滑油，摩擦因数的变化大部分来自刀面角的变化，这些是由数据应用得来的。高一点的摩擦因数与小的刀面角有联系。图2-7（a）也显示了液体润滑油和刀面角共同影响切屑的厚度比。低摩擦和高刀面角导致了低的切屑厚度比。一般的经验，材料和刀面角的变化在图2-7（b）中总结。在金属切削的环境下，低的摩擦系数和切屑等效应变（从方程2-4（b）分别是从0.25到0.5和1 to 3；作为高的摩擦系数和应变是从0.5到1（然而在少数的情况下还要高一点），可高达5。高的材料硬化率也同样通过实验而被发现，从而导致更高的切屑厚度比，尽管在一些在介绍性的部分它还很难支持这种陈述，例如这些。原因是它很困难变化工件的硬化特性，而不去改变它的摩擦系数。一个材料实例，黄铜（70%Cu/30%Zn），它的摩擦系数比其它大多数摩擦系数相比，其更不容易改变，更稳定。图2-8（a）显示了黄铜工件的硬化特性。切屑从工件材料预处理，例如点C，期待通过加工使工件变硬而达到它们最大的硬度。当从不同的预处理样品上形成切屑时，可以得到摩擦系数和切屑厚度比而以15度刀面角的高速钢刀具、大约为0.2mm的吃刀量和从1 到 50m/min切削速度，这些内容在图2-8（b）（Childetal-1972）都显示了出来。预期在以后的部分，在图2-8（b）中工件硬化的测量可独立自主的变化，它在等效应力到最大等效应力上增加比例，是由加工导致的。对于材料D、C和B，厚一点切屑发生在工件硬化大一点的材料，尽管它是一个摩擦系数是一个常量。材料A也显示了厚一点的切屑，但它的摩擦系数也少量地增加了。比较图2-8（b）和图2-7（b），改变工件硬化和摩擦系数对切屑厚度比影响很相似。结果，刀面角、摩擦和工件硬化等都影响切屑的形成。在描述力学加工条件上为获得进一步的发展， 系统强迫规定的参数和力矩平衡一定要介绍。- 13 -图2-8（a）70/30的黄铜工件硬化和（b）摩擦系数和切屑厚度的比来测量标本钢化数量如标记的A到D注：文章来源Metal_Machining。2.2.2 Chip geometries and influencing factorsFigure 2.1 shows views of chips observed more than 100 years ago. Figure 2.4 shows more modern images, photographs taken from polished and etched quick-stop sections (in the manner described in Chapter 5). It shows the wide range of chip flows that are free to be formed, depending on the material and cutting conditions. All these chips have been created in turning tests with sharp, plane rake face cutting tools. Steady or continuous chip formation is seen in Figure 2.4(a) (as has been assumed in Figure 2.2). This example is for70/30 brass, well known as an easy to machine material. Some materials, however, can form a more segmented, or saw tooth, chip (e.g. stainless steel Figure 2.4(b). Others do not have sufficient ductility to form continuous chips; discontinuous chips are formed instead. Figures 2.4(c) (for a brass made brittle by adding lead) and 2.4(d) (for a mild steel cut at very low cutting speed) are, respectively, examples of discontinuous chips showing a little and a lot of pre-failure plastic distortion. In other cases still (mild steel at an intermediate cutting speed Figure 2.4(e) work material cyclically builds up around, and breaks away from, the cutting edge: the chip flows over the modified tool defined by the shape of the built-up edge. The built-up edge has to withstand the loads and temperatures generated by the chip formation. As cutting speed, and hence the temperature, increases ,the built-up edge cannot survive (or does not form in the first place): Figure 2.4(f) (mildsteel at higher speed) shows the thin layer of build-up that can exist to create a chip geometry that does not look so different from that of Figure 2.4(a).This chapter will be concerned with only the most simple type of chip formation continuous chip formation (Figures 2.4(a) and (f) by a sharp, plane rake face tool. Further, only the orthogonal situation (Section 2.2.1) will be considered. The role of mechanics is to show how the force and velocity boundary conditions at the chip tool interface and the work material mechanical properties determine the flow of the chip and the forces required for cutting. For continuous chip formation, determining the flow means at least determining the thickness of the chip, its contact length with the tool and its curvature: none of these are fixed by the tool shape alone. In fact, determining the chip shape is the grand challenge for mechanics. Once the shape is known, determining the cutting forces is relatively simple; and determining the stresses and temperatures in the work and tool, which influence tool life and the quality of the machined surface, is only a little more difficult.The main factors that affect the chip flow are the rake angle of the tool, the friction between the chip and the tool and the work hardening of the work material as it forms the chip. Some experimental observations that establish typical magnitudes of the quantities involved will now be presented, but first some essential notation and common simplifications to the flow (to be removed in Chapter 6) will be introduced. Figure 2.5(a) is a sketch of Figure 2.4(a). It shows the chip of thickness t being formed from an undeformed layer.（a）（b） （c）（d） （e）（f）Fig. 2.4 Chip sections from turning at a feed of about 0.15 mm cutting speeds as ndicated (m/min): (a) 70/30 brass (50), (b) austenitic stainless steel (30), (c) leaded brass (120): (d) mild steel (5), (e) mild steel (25), (f) mild steel (55)Fig. 2.5 Chip flow (a) sketched from Figure 2.4(a); (b) simplified and (c) its velocity diagramof thickness f (the feed) by a tool of rake angle a. The contact length with the tool, OB, is l and the chip radius is r. Regions of plastic flow are identified by the hatched markings. The main deformation zone, known as the primary shear zone, exists around the line OA .Further strain increments are frequently detectable next to the rake face, in the secondary shear zone. A simplified flow (Figure 2.5(b) replaces the primary zone by a straight surface, the shear plane OA and neglects the additional deformations in the secondary zone(although the region might still be at the plastic limit). Figure 2.5(b) shows OA inclined at an angle f to the cutting speed direction. f is called the shear plane angle. As the length of the shear plane OA can be obtained either from (f/sin) or from (t/cos(-), (2.2)Figure 2.5 also identifies the velocity change, Uprimary, that occurs on the primary shear plane, which converts Uwork to Uchip. It further shows the resultant force R responsible for the flow, inclined at the friction angle l to the rake face normal (tan l = the friction coefficient m) and thus at (-+) to OA. It also introduces other quantities referred to later.The magnitude of Uprimary, and of the resulting Uchip, relative to Uwork, can be found from the velocity diagram for the simplified flow (Figure 2.5(c): （2.3）The shear strain that occurs as the chip is formed is the ratio of the primary shear velocity to the component of the work velocity normal to the shear plane. The equivalent strain is 1/times this (Appendix 1). Combining this with equations (2.3) and (2.2), the equivalent strain is: （2.4a）Thus, the severity of deformation is determined by a, (f a) and the chip thickness ratio (t/f ). The ratio/, as will be seen, is almost always in the range 0.9 to 1.3.So （2.4b）Mallocks (188182) observation that chip thickness is strongly influenced by lubrication has already been mentioned. Figure 2.6 dramatically illustrates this. It is a quick-stop view of iron cut by a 30 rake angle tool at a very low cutting speed (much less than 1 m/min). In an air atmosphere the chip formed is thick and straight. Adding a lubricating fluid causes the chip to become thinner and curled. In this case, adding the lubricant caused the friction coefficient between the chip and tool to change from 0.57 to 0.25 (Childs, 1972).The lubricating fluid used in this study was carbon tetrachloride, CCl4, found by early researchers to be one of the most effective friction reducing fluids. However, it （a） （b）Fig. 2.6 Machining iron at low speed: (a) dry (in air) and (b) with carbon tetrachloride applied to the rake faceFig. 2.7 (a) Collected data on the machining of copper, dry () and lubricated (o); and (b) lubricant ffects for a range of conditions at cutting speeds around 1 m/minis toxic and not to be recommended for use today. In addition, CCl4 only acts to reduce friction at low cutting speeds. Figure 2.7 brings together results from several sources on the cutting of copper. It shows, in Figure 2.7(a), friction coefficients measured in air and CCl4 atmospheres at cutting speeds from 1 to 100 m/min, at feeds between 0.1 and 0.25 mm and with cutting tools of rake angle 6 to 40. At the higher speeds the friction-reducing effect of the CCl4 has been lost. Mallock was right to be puzzled by how the lubricant reaches the interface between the chip and tool. How lubricants act in metal cutting is considered further in Section 2.4.2.The range of friction coefficients in Figure 2.7(a) for any one speed and lubricant partly comes from the range of rake angles to which the data apply. Higher friction coefficients are associated with lower rake angles. Figure 2.7(a) also shows how both lubricating fluid and rake angle affect the chip thickness ratio. Both low friction and high rake angles lead to low chip thickness ratios. General experience, for a range of materials and rake angles, is summarized in Figure 2.7(b). In the context of metal cutting, low friction coefficients and chip equivalent strains (from equation 2.4(b) are 0.25 to 0.5 and 1 to 3 respectively; whereas high friction coefficients and strains are from 0.5 to 1 (and in a few cases higher still) and up to 5.High work hardening rates are also found experimentally to lead to higher chip thickness ratios although it is difficult to support this statement in a few lines in an introductory section such as this. The reason is that it is difficult to vary work hardening behaviour without varying the friction coefficient. One model material, with a friction coefficient more constant than most, is a-brass (70%Cu/30%Zn). Figure 2.8(a) shows the work hardening characteristics of this metal. The chips from work material pre-strained, for example to point C, may expect to be work hardened to their maximum hard
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