机械工程专业英语复习资料

务，例如非线性运动和力的传递运动。它们在机构学研究中将受到更多的关注。）

3. The four-bar linkage may take form of a so-called crank-rocker or a double-rocker or a double-crank (drag-link) linkage, depending on the range of motion of the two links connected to the ground link. The input crank of a crank-rocker type can rotate continuously through 360, while the output link just \the length of the input link equals that of the output link and the lengths of the coupler and the ground link are also the same, both the input and output link may rotate entirely around or switch into a crossed configuration called an antiparallelogram linkage. [1] Grashof's criteria states that the sum of the shortest and longest links of a planar four-bar linkage cannot be greater than the sum of the remaining two links if there is to be continuous relative rotation between any two links.（四杆机构可具有一种称作曲柄摇杆机构的形式，一种双摇杆机构，一种双曲柄（拉杆）机构，致于称作哪一种形式的机构，取决于跟机架（固定构件）相连接的两杆的运动范围。曲柄摇杆机构的输入构件，曲柄可旋转通过360°并连续转动，而输出构件仅仅作摇动（即摇摆的杆件）。作为一个特例，在平行四杆机构中，输入杆的长度等于输出杆的长度，连接杆的长度和固定杆（机架）的长度，也是相等的。其输入和输出都可以作整周转动或者转换成称作反平行四边形机构的交叉结构。格拉肖夫准则（定理）表明：如果四杆机构中，任意两杆之间能作连续相对转动，那么，其最长杆长度与最短杆长度之和就小于或等于其余两杆长度之和。）

4. Besides having knowledge of the extent of the rotations of the links, it would be useful to have a measure of how well a mechanism might \that \implies smooth operation, in which a maximum force component is available to produce a force or torque in an output member. Although the resulting output force or torque is not only a function of the geometry of the linkage, but is generally the result of dynamic or inertia force, which are often several times as large as the static force. For the analysis of low-speed operations or for an easily obtainable index of how any mechanism might run, the concept of the transmission angle is extremely useful. During the motion of a mechanism, the transmission angle changes in value. A transmission angle of 0 degree may occur at a specific position, on which the output link will not move regardless of how large a force is applied to the input link. In fact, due to friction in the joints, the general rule of thumb, is to design mechanisms with transmission angle of larger than a specified value. Matrix-based definitions have been developed which measure the ability of a linkage to transmit motion. The value of a determinant (which contains derivatives of output motion variables with respect to an input motion variable for a given linkage geometry[2] ) is a measure of the movability of the linkage in a particular position.

（除了具备关于构件回转范围的知识之外，还要具备如何使机构在制造之前就能“运转”的良好措施，那将是很有用的。哈登伯格（Hartenberg）说到：“运转”是一个术语，其意义是传给输出构件的运动的有效性。它意味着运转平稳，其中能在输出构件中产生一个力或扭矩的最大分力是有效的。虽然最终的输出力或扭矩不仅是连杆几何图形的函数，而且一般也是动力或惯性力的结果，那常常是大到如静态力的几倍。为了分析低速运转或为了易于获得如何能使任一机构“运转”的指数，传动角的概念是非常有用的。在机构运动期间，传动角的值在改变。传动角0°可发生在特殊位置上。在此特殊位置上输出杆将不运动而与施加到输入杆上的力多大无关。事实上，由于运动副摩擦的影响，一般根据实际经验，用比规定值大的传动角去设计机构。衡量连杆机构传递运动能力的矩阵基础的定义已经研究出来。一个决

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定性因素的值（它含有对于某个给定机构图形，位置的输出运动变量对输入变量的导数）是该连杆机构在具体位置中的可动性的一个尺度。）

5. Mechanisms form the basic geometrical elements of many mechanical devices including automatic packaging machinery, typewriters, mechanical toys, textile machinery, and others. A mechanism typically is designed to create a desired motion of a rigid body relative to a reference member. Kinematic design, or kinematic syntheses, of mechanisms often is the first step in the design of a complete machine. When forces are considered, the additional problems of dynamics, bearing loads, stresses, lubrication, and the like are introduced, and the larger problem becomes one of machine design.

（机构是形成许多机械装置的基本几何结构单元，这些机械装置包括自动包装机、打印机、机械玩具、纺织机械和其他机械等。典型的机构要设计成使刚性构件相对基准构件产生所希望的运动。机构的运动设计即运动的综合，第一步常常是先设计整部机器。当考虑受力时，要提出动力学方面的问题，轴承的荷载、应力、润滑等类似的问题，而较大的问题是机器结构问题。）

6. A kinematician defined kinematics as \creating them.\The first part of this definition deals with kinematic analysis. Given a certain mechanism, the motion characteristics of its components will be determined by kinematic analysis. The statement of the tasks of analysis contains all principal dimensions of the mechanism, the interconnections of its links, and the specification of the input motion or method of actuation. The objective is to find the displacements, velocities, accelerations, shock or jerk (second acceleration), and perhaps higher accelerations of the various members, as well as the paths described and motions performed by certain elements. In short, in kinematic analysis we determine the performance of a given mechanism. The second part of definition may be paraphrased in two ways:

（运动学家把运动学定义为“研究机构的运动和创建机构的方法”。这个定义的第一部分就涉及运动学分析。已知一个机构，其构成的运动特性将由运动学分析来确定。叙述运动分析的任务包含机构的主要尺寸、构件间的相互连结和输入运动的技术特性或驱动方法。目的是要找出位移、速度、加速度、冲击或跳动（二次加速度），和可能发生的各构件的高阶加速度以及所描述径迹和由某些构件来实现的运动。定义的第二部分可用以下两方面来解释：） (1) The study of methods of creating a given motion by means of mechanisms (2) The study of methods of creating mechanisms having a given motion.

In either version, the motion is given and the mechanism is to be found. This is the essence of kinematic synthesis. Thus kinematic synthesis deals with the systematic design of mechanisms for a given performance. The area of synthesis may be grouped into two categories. 1．研究借助机构来产生给定运动的方法 2．研究建造能产生给定运动机构的方法

在两个方案中，运动是给定的而机构是创建的。这就是运动综合的本质。这样运动综合涉及到为给定性能的机构的系统设计。运动综合方面又可归结为以下两类

(1) Type synthesis. Given the required performance, what type of mechanism will be suitable? (Gear trains? Linkages? Cam mechanisms?) Also, how many links should the mechanism have? How many degrees of freedom are required? What configuration is desirable? And so on. Deliberations involving the number of links and degrees of freedom are often referred to as the

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province of a subcategory of type synthesis called number synthesis.

(2) Dimensional synthesis. The second major category of kinematic synthesis is best defined by way of its objective : Dimensional synthesis seeks to determine the significant dimensions and the starting position of a mechanism of preconceived type for a specified task and prescribed performance. 1．类型综合。规定所要求的性能，怎样一种类型的机构才是合适的？（齿轮系，连杆机构？还是凸轮机构？）而机构应具有多少构件？需要多少个自由度？怎样的轮廓结构才是所希望的？等等。关于杆件数目和自由度的考虑通常被认为是类型综合中被称作为数量综合的一个分支领域。

2．尺寸综合。运动综合的第二个主要类型是通过目标法来确定的最佳方法。尺寸综合试图确定机构的重要尺寸和起动位置，该机构是为着实现规定的任务和预期的性能而事先设想的。

of their contacting profiles must be such that the common normal passes through a fixed point on the line of the centers.

齿轮是借助于轮齿成功啮合来传递运动的机器零件。齿轮从一根回转轴到另一回转轴传递运动或传递运动到一传动齿条。多数应用中都以恒定角速比（或常定扭矩比）而存在。恒定角速比应用中必定是轴向传动。在各种各样有用的齿轮类型基础上，输入轴和输出轴需要在一直线上或需要互相平行都不受什么限制。由于使用非圆齿轮，非线性角速比也是很有用的。为了保持恒定的角速度，各个齿轮齿廓必须服从齿轮啮合的基本规律：为了一对齿能传递恒定角速比，他们接触齿廓的形状必须是要这样：公法线通过两齿轮中心连线上的固定点。

1：把下列英文单词翻译成中文： (1) threshold

参考答案：开端，开始 (2) graphics terminal

参考答案：图像终端 (3) a translate command

参考答案：平移指令 (4) construction robotics

参考答案：建筑（结构）机器人 (5) a power-driven device 参考答案：力驱动装置

2：把下列中文词组翻译成英文： (6) 热加工

参考答案：hot working (7) 非正常晶体生长

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参考答案：abnormal grain growth (8) 再结晶

参考答案：recrystallization (9) 机械效益

参考答案：mechanical advantage (10) 力放大器

参考答案： a force multiplier 二、句型 （20分）（每个题目为4分）（翻译的内容，达到意思一致即算正确） 请将下列英文句子翻译成中文

（1） Efficiency and mechanical advantage are used to gauge the performance

of mechanical machine .

参考答案：效率和机械效益是用来检测机械装置的工作性能的。

（2） Methods of extracting , producing and treating metals are being developed

all the time to meet engineering requirements .

参考答案：为了满足工程需要，提炼、生产和处理金属的方法一直处于发展进步之中。 (3) The common metallic materials possess the metallic properties of luster , thermal conductivity, and electrical conductivity ；are relatively ductile； and some have good magnetic properties .

参考答案：常见的金属材料拥有的金属性能如：光泽、导热性和导电性，并且有较好的延展性，此外，还有一些金属材料具有好的磁性。

(4) It is their plasticity at certain temperatures , which gives plastics their main advantage over many other materials .

参考答案：一定温度下的塑料的塑性，使得塑料相对其他材料而言，具有的主要的优势。 （5） Die life and die failure are greatly affected by the mechanical properties of the die materials under the conditions that exit in a given deformation process . 参考答案：在给定的成型工艺下，模具材料的机械性能对模具寿命和模具损坏有很大的影响。 三、段落：（40分）

（1）Although the four—bar linkage and slider—crank mechanism are very useful and found in thousands of applications , we can see that these linkages have limited performance level . Linkages with more members are often used in more demanding circumstances . However it is often difficult to visualize the movement of a multiloop linkage , especially when other components appear in the same diagram . The first step in the motion analysis of more complicated mechanisms is to sketch the equivalent kinematic or skeleton diagram . The skeleton diagram serves a purpose similar to that of the electrical schematic or circuit diagram in that it displays only the essential skeleton of the mechanism , which , however , embodies the key dimensions that affect its motion .

参考答案（满分20分）（翻译的内容，达到意思一致即算正确）：虽然四杆机构和曲柄-

滑块机构的用途很大，但是我们还是可以发现，这些机构的实际操作水平还是有限的。机构的构件越多，机构的用途也就越大。人们很难直观地想象出多环链连

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