机械工程专业英语 施平 没翻译课文补充.docx

1、机械工程专业英语 施平 没翻译课文补充4、工程机械概述 As we look around us we see a world full of “things”: machines, devices, tools; things that we have designed, built, and used; things made of wood, metals, ceramics, and plastics. We know from experience that some things are better than others; they last longer, cost less

2、, are quieter, look better, or are easier to use. 正如我们环顾四周 我们看到世界的“东西” 机器全 设备 工具;事情 我们已经设计 建造和使用;木材 金属 陶瓷制成的东西 和塑料。我们从经验知道 有些事情是比别人做得更好 他们去年更长 成本更低 更安静 看起来更好 或者更容易使用。理想的情况. Ideally, however, every such item has been designed according to some set of “functional requirements” as perceived by the desi

3、gners that is, it has been designed so as to answer the question, “Exactly what function should it perform?” In the world of engineering, the major function frequently is to support some type of loading due to weight, inertia, pressure, etc. 但是 每个这样的项目已按设计一些“功能要求 ”由设计者认为 也就是说 它的设计 以回答这个问题 “究竟是什么职能应是

4、执行 在工程世界” 频繁的主要功能是如此的支持 由于一些装载重量 惯性 压力式 From the beams in our homes to the wings of an airplane, there must be an appropriate melding of materials, dimensions, and fastenings to produce structures that will perform their functions reliably for a reasonable cost over a reasonable lifetime. 从我们家中的光束 飞

5、机的一个机翼等 必须对产品的材料 尺寸适当的融合 和紧固件生产结构 将执行一个较合理的成本合理的一生中其职能可靠。 In practice, engineering mechanics methods are used in two quite different ways: (1) The development of any new device requires an interactive, iterative consideration of form, size, materials, loads, durability, safety, and cost. (2) When a

6、device fails (unexpectedly) it is often necessary to carry out a study to pinpoint the cause of failure and to identify potential corrective measures. Our best designs often evolve through a successive elimination of weak points. 在实践中 工程力学方法用于在两个完全不同的方式 1.任何新设备的发展需要一个互动 形式 尺寸 材料 载荷 耐久性 安全性和cost. 2.迭

7、代审议。当一个设备出现故障 往往是要进行一项研究 以查明故障原因 并找出潜在的纠正措施。我们最优秀的设计往往演变的薄弱环节 通过逐步消除。 To many engineers, both of the above processes can prove to be absolutely fascinating and enjoyable, not to mention (at times) lucrative. 对许多工程师 上述过程都可以被证明是绝对精彩和愉快的 更不用提有利可图。 In any “real” problem there is never sufficient good, u

8、seful information; we seldom know the actual loads and operating conditions with any precision, and the analyses are seldom exact. While our mathematics may be precise, the overall analysis is generally only approximate, and different skilled people can obtain different solutions. In the study of en

9、gineering mechanics, most of the problems will be sufficiently “idealized” to permit unique solutions, but it should be clear that the “real world” is far less idealized, and that you usually will have to perform some idealization in order to obtain a solution. 在任何“真正”的问题从来就没有足够好的 有用的信息 我们很少知道实际的载荷和

10、精确操作的任何条件 准确的分析很少。虽然我们可以精确的数学 综合分析 一般只是近似 不同技能的人可以得到不同的解决方案。在工程力学研究中 大多数问题都将得到充分的“理想化”允许独特的解决方案 但应该清楚 “现实世界”远不如理想 而且你通常会在命令必须执行一些理想化获得一个解决方案。 The technical areas we will consider are frequently called “statics” and “strength of materials,” “statics” referring to the study of forces acting on station

11、ary devices, and “strength of materials” referring to the effects of those forces on the structure (deformations, load limits, etc.). 在技术领域中 我们将考虑的是通常称为“静”与“材料力学” “静”指的是对固定设备作用力学风和“材料力学”指的是这些部队在结构上的影响。 While a great many devices are not, in fact, static, the methods developed here are perfectly appl

12、icable to dynamic situations if the extra loadings associated with the dynamics are taken into account (we shall briefly mention how this is done). static 尽管许多设备都没有 事实上 静态的 这里开发的方法是完全适用于动态的情况如果与动态相关联的额外负荷 考虑。. Whenever the dynamic forces are small relative to the static loadings, the system is usual

13、ly considered to be 每当动态势力相对较小的静态负荷 系统通常被认为是静态的。 In engineering mechanics, we will appreciate the various types of approximations that are inherent in any real problem: Primarily, we will be discussing things which are in “equilibrium,” i.e., not accelerating. However, if we look closely enough, eve

14、rything is accelerating. We will consider many structural members to be “weightless” but they never are. We will deal with forces that act at a “point” but all forces act over an area. We will consider some parts to be “rigid” but all bodies will deform under load. 在工程力学 我们赞赏逼近了在任何类型的固有的各种现实问题 首先 我们

15、将要讨论的事情 这是在“均衡” 即没有加速。但是 如果我们仔细观察的话 一切都正在加速。我们会考虑很多构件是“失重” 但是他们从来没有的。我们将按 照部队的这种行为在一个“点” 但所有力量在一个区域的行为。我们会考虑的某些部分“刚性” 但所有机构将在负荷下变形。 We will make many assumptions that clearly are false. But these assumptions should always render the problem easier, more tractable. You will discover that the goal is

16、to make as many simplifying assumptions as possible without seriously degrading the result. 我们会作出这样的假设显然是错误的。但是 这些假设应始终呈现的问题更容易 更容易处理。你会发现 他们的目标是使尽可能多的简化假设没有严重退化的结果。 Generally there is no clear method to determine how completely, or how precisely, to treat a problem: If our analysis is too simple, w

17、e may not get a pertinent answer; if our analysis is too detailed, we may not be able to obtain any answer. It is usually preferable to start with a relatively simple analysis and then add more detail as required to obtain a practical solution. 一般来说 没有明确的方法来确定如何彻底 或如何精确地说 对待一个问题 如果我们的分析过于简单 我们可能无法获得

18、相关的答案 如果我们的分析过于详细 我们可能无法获得任何答案。它通常是最好先从相对简单的分析 然后添加更多的细节 因为需要得到实际的解决办法。 During the past two decades, there has been a tremendous growth in the availability of computerized methods for solving problems that previously were beyond solution because the time required to solve them would have been prohib

19、itive. At the same time the cost of computer capability and use has decreased by orders of magnitude. We are experiencing an influx of “personal computers” on campus, in the home, and in business. 在过去的二十年来 一直在为解决以往无法解决的问题 进行电脑化方法的途径巨大增长 因为所需的时间来解决这些问题将被禁止。在同一时间内 计算机能力和使用成本下降了几个数量级。我们正经历一个“个人电脑”校园涌入

20、在家里 和商业活动中。 26、车床 The general characteristics of the machine tools used in cutting operations are reviewed in this text. The equipment can be classified in different categories depending on their function and the accessories involved. The major categories are described below. 在切割操作中使用的机床的一般特征 在这篇文章进

21、行阐述。依据功能和所包含的配件 设备可分为不同类别。主要类别如下所述。 Lathes Lathes are generally considered to be the oldest machine tools and were developed in the 1750s.The basic operations carried out on a lathe are turning, boring, and facing. 车床 车床通常被认为是最古老的机床 并在1750s产生.车床上进行基本操作有车削 镗 和端面车削。 The basic components of the most co

22、mmon lathe( engine lathe ) are the bed, headstock, tailstock, and carriage. One end of the workpiece is clamped in a chuck that is mounted on the spindle, the spindle rotates in the headstock. The other end of the workpiece is supported by the tailstock. The headstock contains the drive gears for th

23、e spindle speeds, and through suitable gearing and the feed rod, drives the carriage and cross slide assembly. The carriage provides motion parallel to the axis of rotation, and the cross slide provides motion normal to it. A cutting tool, attached to a tool post and to the carriage, removes materia

24、l by traveling along the bed. The cutting operation is performed at a certain desired peripheral speed of the workpiece, feed rate, and depth of cut 最常见的车床 普通车床 的基本组成部分是床身 床头 尾座和.托架。工件的一端是被一个安装在主轴的夹头夹紧 主轴在床头旋转。工件的另一端是由尾座支撑。床头包含主轴转速传动齿轮 并通过适当的齿轮和进给杆 驱动车架 使滑动装配滑动。托架提供运动平行旋转轴 横滑板提供了正常的运动。切削刀具 连接到一个刀架和托

25、架 沿床消除材料。切割操作是按工件所需的一定的外设速度 进给速度 切削深度运行。 A further development is the automatic lathe. The movements and controls are actuated by various mechanical means, such as cams and numerical and computer control, thus reducing labor or requiring less skilled labor. 进一步发展的是自动车床。通过各种机械手段 运动和控制更加精确。 如凸轮和数控和计算机

26、控制 从而减轻了工人的劳动或要求不太熟练的劳动力。 Turret lathes (developed in the 1850s)carry out multiple cutting operations, such as turning, boring, drilling, thread cutting, and facing. Various cutting tools, usually up to six are installed on a turret. The operation is quite versatile. It may be operated by hand or au

27、tomatically and, once set up properly, it does not require skilled labor. There are a great variety of turret lathes available for different purposes. 转塔车床 在19世纪50年代开发的 能够进行了多种切割操作 如车削 镗 钻 线切割 端面车削。各种切削工具 通常在最多六个炮塔上安装。操作相当灵活。它可能是手工操作或自动 一旦正确安装 它并不需要熟练的劳动力。有种类繁多的炮塔车床可用于不同的目的 Screw machines (the first

28、 screw lathe was developed in the 1770s)are designed for high production rate machining of screws and similar parts. All the operations are performed automatically with tools attached to a special turret. The bar stock is fed automatically after each screw has been machined to a finished product. Th

29、ese machines may be equipped with single or multiple spindles to reduce the cycle time per piece. 螺杆机 在18世纪70年代开发了第一个螺丝车床 是专为高产率 自动化生产螺钉 和类似部件的设计的。所有的操作都由连接到一个特殊的炮塔的工具自动执行。每个螺丝加工成成品后 棒料自动送入。这些机器可能会配有单个或多个主轴 Milling Machines These are among the most versatile and useful machine tools because they are

30、 capable of performing a variety of cutting operations. There is a large selection of milling machines (developed in the 1860s)available with numerous features. The basic types are outlined below.Knee-and-column type milling machines are the most common and are used for general-purpose machining. Th

31、e spindle, to which the milling cutter is attached, may be horizontal (for slab milling), or vertical (for face milling). 铣床 铣床是最通用和最有用的工具机 因为它们能够执行各种切割操作。有大量的提供众多特性的铣床可供选择 在19世纪60年代开发的 。基本类型概述如下。 升降台式铣床是最常见的 用于一般用途的加工。连接铣刀的主轴 可水平 板坯铣削 或垂直 面铣 。 Bed-type milling machines have the table mounted on a bed (replacing the knee) and can move only in the longitudinal direction. These machines are simple and rigidly constructed and are used for high-quantity production. The spindles may be horizontal or vertical and can be of duplex or triplex types (that is, with two or three spindl