机械制造及其自动化专业英语汇总文档格式.docx

1、例如如 果作用在一个滑动轴承上的力太大,它就会将油膜挤出,造成金属与金属的直接接触,产生过热和使轴承快速失效。如果齿轮相啮合的齿与齿之间的力过大就会将油膜从齿间挤压出来。这会造成金属表层的碎裂和剥落,噪音增大,运动不精确直至报废。在力学研究中,我们主要关心力的大小、方向和作用点。Some of the terms used in mechanics are defined below. 在力学中要用到的一些术语定义如下。Force Our earliest ideas concerning forces arose because of our desire to push , lift ,

2、or pull various objects . So force is the action of one body on another . Our intuitive concept of force includes such ideas as place of application , direction ,and magnitude , and these are called the characteristics of a force . 力 关于力的最早概念是由我们需要推、举或拉各种物体而产生的。因此，力是物体之间的相互作用。力的直接概念包括作用点、大小和方向，这些被称为

3、力的要素。Mass is a measure of the quantity of matter that a body or an object contains . The mass of the body is not dependent on gravity and therefore is different from but proportional to its weight . Thus , a moon rock has a certain constant amount of substance , even though its moon weight is differ

4、ent from its earth weight . This constant amount of substance , or quantity of matter , is called the mass of the rock . 质量 是物体内所包含的物质的量。物体质量不受重力影响，因此与物体重量不同，但是与其成比例。尽管一块月球岩石在月球上和地球上的重量不同，但它的物质含量是不变的。这不变的物质含量就称为岩石的质量。Inertia is the property of mass that causes it to resist any effort to change its m

5、otion . 惯性 是质量所具有的抵抗任何外力改变其本身运动状态的性质。 Weight is the force with which a body is attracted to the earth or another celestial body , equal to the product of the objects mass and the acceleration of gravity . 重量 是地球或其他天体对物体的吸引力，它等于物体的质量与重力加速度的乘积。Particle A particle is a body whose dimensions are so smal

6、l that they may be neglected . 质点 当一个物体尺寸特别小，可以忽略不计时，该物体可以被称为质点。Rigid Body A rigid body does not change size and or shape under the action of forces. Actually, all bodies are either elastic or plastic and will be deformed if acted upon by forces . When the deformation of such bodies is small , they

7、are frequently assumed to be rigid , i.e. , incapable of deformation , in order to simplify the analysis . A rigid body is an idealization of a real body.刚体 刚体在受力后，其大小和形状都不会发生变化。实际上，所有的物体，不管是弹性体还是塑性体，在外力作用下都会发生形变。当物体的变化非常小时，为了简化计算，通畅假设这个物体是刚体，也就是认为它没有发生形变。刚体是实际物体的理想化模型。Deformable Body The rigid body

8、 assumption cannot be used when internal stresses and strains due to the applied forces are to be analyzed . Thus we consider the body to be capable of deforming . Such analysis is frequently called elastic body analysis , using the addit ional assumption that the body remains elastic within the ran

9、ge of the applied forces . 变形体 在分析由于外力的作用所引起物体内部的应力和应变时，不能采用刚体假设。这时，认为物体能够变形。这样的分析通常被称为弹性体分析，这时所用的假设为，在作用力范围内，物体是弹性的。Newtons Laws Newtons three laws are :牛顿定律 牛顿三定律为：Law 1 If all the forces acting on a particle are balanced , the particle will either remain at rest or will continue to move in a stra

10、ight line at a uniform velocity . 第一定律 如果作用在一个质点上的所有外力平衡，那么，这个质点保持原来的静止或者匀速直线运动状态不变。Law 2 If the forces acting on a particle are not balanced , the particle will experience an acceleration proportional to the resultant force and in the direction of the resultant force . 第二定律 如果作用在一个质点上的所有外力都不平衡，那么，这

11、个质点将产生一个与外力合力成正比的加速度，加速度的方向与合力方向相同。Law 3 When two particles react , a pair of interacting forces come into existence ; these forces have the same magnitudes and opposite senses , and they act along the straight line common to the two particles . 第三定律 两个质点相互作用时，存在着一对作用力和反作用力。作用力和反作用力大小相等，方向相反，沿着同一条直线

12、作用在两个质点上。Mechanics deals with two kinds of quantities : scalars and vectors . Scalar quant it ies in mechanics are time , volume ,density , speed , energy , and mass . Vector quantities , on the other hand , possess direction as well as magnitude . Examples of vectors are displacement , velocity , a

13、cceleration , force , moment , and momentum . 力学涉及两种类型的量：标量和矢量。标量是那些只有大小的量。在力学中，标量的例子有时间、体积、密度、速率、能量和质量。另一方面，矢量既有大小又有方向。矢量的例子有位移、速度、加速度、力、力矩和动量。Shafts and CouplingsVirtually all machines contain shafts. The most common shape for shafts is circular and the cross section can be either solid or hollow（

14、hollow shafts can result in weight savings）. Rectangular shafts are sometimes used, as in screwdriver blades, socket wrenches and control knob stems.实际上，几乎所有的机器中都装有轴。轴最常见的形状是圆形，其截面可以是实心的，也可以是空心的（空心轴可以减轻重量）。有时也可以采用矩形轴，例如，螺丝刀的头、套筒扳手和控制旋钮的杆。A shaft must have adequate torsional strength to transmit torq

15、ue and not be overstressed. It must also be torsionally stiff enougth so that one mounted component does not deviate excessively from its original angular position relative to a second component mounted on the same shaft . Generally speaking, the angle of twist should not exceed one degree in a shaf

16、t length equal to 20 diameters.为了在传递扭矩时不发生过载，轴应该具有适当的抗扭强度。轴还应该具有足够的抗扭刚度，以确保同一个轴上的两个转动零件之间的相对转角不会过大。一般来说，当轴的长度等于其直径的20倍时，扭转角不应该超过1度。Shafts are mouted in bearings and transmit power though such devices as gears,pulleys,cams and clutches.these devices introduce forces which attempt to bend the shaft;he

17、nce,the shaft must be rigid enough to prevent overloading of the supporting bearings.Ingeneral,the bending deflection of a shaft should not exceed 0.5 mm per meter of length berween bearing supports.轴安装在轴承中，通过齿轮、皮带轮、凸轮和离合器等零件传递动力。通过这些零件传来的力可能会使轴产生弯曲变形。因此，轴应该有足够的刚度以防止支承轴受力过大。总而言之，在两个轴承支承之间，轴在每米长度上的弯曲

18、变形不应该超过0.5mm。In addition,the shaft must be able to sustain a combination of bending and torsional loads.Thus an equivalent load must be considered which takes into account both torsion and bending.Also,the allowable stress must contain a factor of safety which includes fatigue,since torsional and be

19、nding stress reversals occur. 此外，轴还必须能够承受弯矩和扭矩的组合作用。因此，要考虑扭矩与弯矩的当量载荷。因为扭矩和弯矩会产生交变应力，在许用应力中也应该有一个考虑疲劳现象的安全系数。For diameters less than 75 mm,the usual shaft material is cold-rolled steel containing about 0.4 percent carbon.Shafts are either cold-rolled or forged in sizes from 75 mm to 125 mm.For sizes

20、above 125 mm,shafts are forged and machined to the required size.Plastic shafts are widely used for light load applications.One adwantage of using plastic is safety in electrical applications,since plastic is a poor conductor of electricity.直径小于75mm的轴可以采用含碳量大约为0.4%的冷轧钢，直径在75125mm之间的轴可以采用冷轧钢或锻造毛坯。当直径

21、大于125mm时，则要采用锻造毛坯，然后机械加工到所要求的尺寸。轻载时，广泛采用塑料轴。由于塑料是电的不良导体，在电器中用他作轴比较安全。Components such as gears and pulleys are mounted on shafts by means of key.The design of the key and the corresponding keyway in the shaft must be properly evaluated.For example,stress concentrations occur in shafts due to keyways,

22、and the material removed to from the keyway further weakens the shaft.齿轮和皮带轮等零件通过键连接在轴上。在对键及轴上与之相应的键槽进行设计时，必须进行认真的计算。例如，轴上的键槽会引起应力集中，由于键槽的存在将使轴的横截面积减小，会进一步减弱轴的强度。If shafts are run at critical speeds, severe vibrations can occur which can seriously damage a machine. It is important to know the magnit

23、ude of these critical speeds so that they can be avoided. As a general rule of thumb, the difference between the operating speed and the critical speed should be at least 20 percent.如果轴以临界速度转动，将会发生强烈地振动。可能会毁坏整台机器。知道这些临界速度的大小是很重要的，应这样可以避开它。根据一般经验来说，工作速度与临界速度之间至少应该相差20%。Another important aspect of sha

24、ft design is he method of directly connecting one shaft to another. This is accomplished by devices such as rigid and flexible couplings.轴的设计工作的另一个重要方面是轴与轴之间的直接连接方法。这是有刚性或者弹性联轴器来实现的。A coupling is a device for connecting the ends of adjacent shafts. In machine construction ,coupling are used to effec

25、t a semipermanent connection between adjacent rotating shafts. The connection is permanent in the sense that it is not meant to be broken during the useful life of the machine,but it can be broken and restored in an emergency or when worn parts are replaced.联轴器是用来把两个相邻的轴端连接起来的装置。在机械结构中，联轴器被用来实现相邻的两根

26、转轴之间的半永久连接。在机器的正常试用期间内，这周连接一般不必拆开，在这种意义上，可以说联轴器的连接时永久性的。但是在紧急情况下，或者需要更换需要更换已磨损的零件时，可以先把联轴器拆开，然后再连接上。There are several types of shaft coupling,their characteristics depend on the purpose for which they are used.If an exceptional long shaft on a ship,it is made in sections that are coupled together wi

27、th rigid coupling.A common type of rigid coupling consist of two mating radial flanges that are attached by key-driven hubs to the ends of adjacent shaft section and bolted together through the flanges to form a rigid connection.Alignment of the connected shafts is usually effected by meant of a rabbet joint on the face of the flanges.联轴器有几种类型，它们的特性随其用途而定。如果制造工厂中或者传播的螺旋桨需要一根特别长的轴，可以采用分段的方式将其制造出来，然后采用刚性联轴器将各段连接。一种常用的联轴器使用两个配对的法兰盘组成，这两个法兰盘借助靠键传动的轴套连接到相邻两节轴的两端，然后用螺栓穿过法兰连接起来形成刚性接头。相互俩你就饿的两根轴通常是靠法兰面上的槽口来进行找正的。In connecting shafts belongs to separate devices