1. Metals and Their Use
It is known that metals are very important in our life. Metals have the greatest importance for industry. All machines and other engineering constructions have metal parts; some of them consist only of metal parts.
There are two large groups of metals:
1) Simple metal- more or less pure chemical elements
2) Alloys - materials consisting of a simple metal combined with some other elements.
About two thirds of all elements found in the earth are metals, but not all metals may be used in industry. Those metals which are used in industry are called engineering metals. The most important engineering metal is iron , which in the form of alloys with carbon and other elements, finds greater use than any other metal. Metals consisting of iron combined with some other elements are known as ferrous metals; all the other metals are called nonferrous metals. The most important nonferrous metal are copper , aluminum , lead , zinc , tin , but all these metals are used much less than ferrous metals, because the ferrous metals are much cheaper.
Engineering metals are used in industry in the form of alloys because the properties of alloys are much better than the properties of pure metals. Only aluminum may be largely used in the form of simple metal. Metals have such a great importance because of their useful properties or their strength, hardness, and their plasticity .
Different metals are produced in different ways, but almost all the metal are found in the forms of metal ore (iron ore, copper ore, etcet cetra.)
The ore is a mineral consistence of a metal combined with some impurities . In order to produce a metal from some metal ore, we must separate these impurities from the metal that is done by metallurgy .
2. Plastics and Other Materials
Plastics have specific properties which may make them preferable to traditional materials for certain uses. In comparison with metals, for example, plastics have both advantages and disadvantages. Metals tend to be corroded by inorganic acids , such as sulphuric acid and hydrochloric acid. Plastics tend to be resistant to these acids, but can have dissolved or deformed by solvent , such as carbon tetrachloride , which have the same carbon base as the plastics. Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigid than most plastics while plastics are very light, with a specific gravity normally between 0.9 and 1.8. Most plastics do not readily conduct heat or electricity . Plastics soften slowly and can easily be shaped when they are soft.
塑料具有特殊的性能。对于某种用途而言，这些性能使得塑料比传统材料更为可取。例如，跟金属相比较，塑料既有优点也有缺点。金属易受到无机酸的腐蚀，如硫酸和盐酸，塑料能抵抗这些酸的腐蚀，但可被溶剂所洛解或引起变形，例如溶剂四氯化碳与塑料具有同样的碳基。颜色必定只能涂到金属的表面。而它可以跟塑料混合为一体。金属比大多数塑料刚性要好，而塑料则非常之轻，通常塑料密度在0. 9-1. 8之间。大多数塑料不易传热导电。塑料能缓慢软化，而当其还是在软的状态时，能容易成形。
It is their plasticity at certain temperatures which gives plastics their main advantages over many other materials. It permits the large-scale production of molded articles, such as containers, at an economic unit cost, where other materials require laborious and often costly processes involving cutting, shaping, machining, assembly and decoration.
在某一温度下塑料是处于塑性状态的，这就使塑料具备超过许多其他材料的主要优点。它容许大量生产单位成本低廉的模制式器件，例如，各种容器。于此，若用其他材料则需要大量劳力和往往需要很费钱的加工工艺，比如，切割、成形、加工、装配和装饰。
Plastics not only replace other materials. Their properties can be exploited for entirely new applications. For example, plastics heart valves and other human 'spare parts' have make possible many recent developments in surgery .
There is no single plastics material which is suitable for all applications. It is important that the most suitable plastics should be chosen, and if necessary adapted, for each particular requirement. It is also important that the properties of the plastics chosen should be exploited to the best advantage.
A plastics article may need to differ in design and appearance from a similar article made from another material such as metal or wood. This is due not only to the properties of plastics but also to the techniques employed in fabricating plastics. These techniques include injection molding , blow molding, compression molding, extrusion and vacuum forming.
3. Casting and Die-Casting Alloys
Casting is one of the oldest metal working techniques known to man. Our country made metal castings as early as 2000 B.C., and the process used then is not much different in principle from the one used today.
铸造是入类所掌握的最古老的金属加工技术之一。我国早在公元前2000年就已把金属制成铸件，而所使用的工艺从原理上和今天的工艺没有多大的区别。
Foundry processes consist of making molds, preparing and melting the metal, pouring the metal into the molds, and cleaning the castings. The product of the foundry is a casting, which may vary from a fraction of a kilogram to several hundred tons. It may also vary in composition as practically all metals and alloys can be cast.
铸造工艺由制模、备料和金属熔炼，金属液浇注入模和铸件清砂等。铸造的产品是铸件，铸件可能从零点几公斤到几百吨范围变化。实际上所有金属在成分上也是变化的，而合金也可以铸造。
The metals most frequently cast are iron, steel, aluminum and so on. Of these, iron, because of its low melting point, low price and ease of control, is outstanding for its suitability ✞for casting and is used far more than all the others.
最常铸造的金属是铸铁、钢、铝等等。这些金属中，铸铁，由于其低熔点，低价格和易控制，因而其铸造适应性是最突出的，而且使用也远比所有其他金属多。
Casting is a widely used method of producing metal products, particularly those which are intricate . Since molten materials will readily take the shape of the container into which they are poured, it is nearly as easy to cast fairly complex shapes as to produce simple forms.
由于熔融的物料能容易取得被浇注进去的容器〔模型)的形状，因此，几乎像生产简单形状铸件那样颇为容易地铸造出复杂形状的铸件。
The place where the metals are cast is called a foundry. The most important of cast metals is cast iron which is made from pig iron by remelting it in a special melting furnace called a cupola .
铸造金属的地方叫做铸造车间。最重要的铸造金属是铸铁，铸铁是用生铁在一个特殊的熔炉—叫冲天炉的炉子中重新熔炼而制造出来的。
From the cupola, the cast iron flows into ladles of different size, and from these ladles it is poured into the molds.
从冲天炉中出来的铁水流入到不同规格的铁水包中，并从这些铁水包中被浇注到模型中。
The molds may be of two kinds: sand molds and metal molds. A metal mold consists of two hollow parts which should be joined for pouring the metal into it. The inside of this mold is covered with carbon or graphite so that the metal could not stick to the wall of the form. When the metal has solidified , these hollow parts are disjoined and the casting is taken out. There are also special molds in which large blocks of steel can be cast. These molds are usually made of cast iron and are called ingot molds, which the blocks of steel produced by pouring the metal into these molds are called ingots and the process is called ingot casting.
模型有两种类型:砂模和金属模。金属模是由两个中空的部件组成，它们应被联结在一起以便将金属液浇入模箱中。这模腔的内侧是要涂以碳粉或石墨，因此金属不玫于粘贴到型腔壁上口当金属液凝固后，这中空的型箱部件被打开并取出铸件。也有一种特殊模型，在该模型中可以铸造大型钢块。这些模型通常用铸铁米制造，并被称为锭模。而浇注金属液到这些模子中生产出的钢块被称为钢锭。该工艺过程叫锭铸。
A relatively wide range of nonferrous alloys can be die-cast. The principal base metals used, in order to commercial importance, are zinc, aluminum, copper, magnesium , lead, and tin. The alloys may be further classified as low-temperature alloys and high-temperature alloys; those having a casting temperature below 538C, such as zinc, tin, and lead, are in the low-temperature class. The low-temperature alloys have the advantages of lower cost of production and lower die-maintenance costs. As the casting temperature increases, alloy and other special steels in the best treated condition are required to resist the erosion and heat checking of die surface. The destructive effect of high temperatures on the dies has been the principal factor in retarding the development of high-temperature die castings.
相当大量的有色金属合金可以进行模铸}h用的主要而基本的金属，按其在工业上应用的重要性的顺序是锌、铝、铜、锰、铅和锡。这些合金可以进一步进行分类为低温类合金和高温类合金。铸造温度低于538℃的那些合金，就像锌、锡和铅,是属于低温类合金。低温类合金具有低生产成本和低的模具维修费用等优点。当铸造温度上升时，需要最佳条件下处理过的合金钢和其他特种钢来抵抗腐蚀及防止模具表面的热裂纹。高温在模具上的损坏作用已经成为阻碍、延缓高温模铸发展的主要因素。
Another factor governing the choice of alloy is the erosive or solvent action of the molten metal on the respective machine parts and dies. This action increases with temperature, although it is more pronounced with some alloys than with others. Aluminum, in particular, has a destructive action on ferrous metals and, for this reason, is seldom melted in the machine, whereas the copper-base alloys are never melted in the machine.
控制选择合金的另外一个因素就是熔融的金属在相关的机器零件上和模具上的腐蚀或溶解作用。这种作用随着温度的升高而增加，甚至某些合金比另一些合金更为明显。特别是.铝对黑色金属有一种破坏作用，为此、铝几乎不熔混于机器零件中，而铜基合金是决
不能熔混于机器构件中的。
4. Forging
Press forging employs a slow squeezing action in deforming the plastic metal, as contrasted with the rapid-impact blows of a hammer. The squeezing action is carried completely to the center of the part being pressed, thoroughly working the entire section . These presses are the vertical type and may be either mechanically or hydraulically operated. The mechanical presses, which are faster operating and most commonly used, range in capacity from 500 to 1000 tons.
与锤锻的快速冲击不同，压力机锻造是用缓慢的挤压作用使塑性金属变形。这挤压作用完全被施加到正在被压锻的零件中心位置上，直至彻底使整个工件得到加工。这些压力机都是立式的，可能是机械操作也可能是液压操作的。机械操作压力机，操作速度比较快，使用最普遍，锻造能力从5400吨到10000吨范围。
For small press forgings, closed impression dies are used and only one stoke of the ram is normally required to perform the forging operation. The maximum pressure is built up at the end of the stroke which forces the metal into shape. Dies may be mounted as separate units, or all the cavities may be put into single block. For small forgings, individual die unites are more convenient. There is some difference in the design of dies for different metals; copper-alloy forgings can be made with less draft than steel, consequently more complicated shapes can be produced. These alloys flow well in the die and are rapidly extruded 对于小型压力锻使用闭式锻模。通常要求锻锤仅一个冲程就完成锻造工艺。在冲程终端产生最大压力，该冲击压力迫使金属成形。模具可由各白独立的单元装配而成，即把所有个别模腔都放到一起，组成整体。对于小型锻件使用分模装置更为方便。对于不同的金属在模具设计上有些区别.铜合金锻件比钢件用较小的拔模斜度，因此可生产更加复杂形状的锻件。这些合金在该种模具中流动性好，而且能快速挤压成形。
In the forging press, a greater proportion of the total work put into the machine is transmitted to the metal than in a drop hammer press. Much of the impact of the drop hammer is absorbed by the machine and foundation. Press reduction of the metal is faster, and the cost of operation is consequently lower. Most press forgings are symmetrical in shape, having surfaces which are quite smooth, and provide a closer tolerance than is obtained by a drop hammer. However, many parts of irregular and complicated shapes can be forged more economically by drop forging. Forging press is often used for sizing operations on parts made by other forging processes.
锻压机比落锤锻，输入到机器里的总能量中有更大部分的能量被传输到金属坯料上。落锤锻的冲击能量被机器和基础吸收得较多(比起压力机来〕。金属上的压力衰减较快，因此生产成本比较低。大多数压力锻锻件形状、产生的表面都是对称的，而且表面非常光滑，并比落锤锻件的公差尺寸更加精确。然而落锤锻造可以锻制形状复杂而不规则的锻件，因而较为经济。锻压机常常用来为其他锻造工艺所生产的锻件进行整形和校正加工用。
In drop forging, a piece of metal, roughly or approximately of the desired shape, is placed between die faces having the exact form of the finished piece, and forced to take thin form by drawing the dies together. Large ingots are now almost always forged with hydraulic presses instead of with steam hammers, since the work done by a press goes deeper. Further, the press can take a cooler ingot and can work to closer dimensions . The forging should be done at about the same temperature as rolling ; the process improves the physical properties of the steel just as
rolling does. In the final forging it is important not to have the steel too hot, for overheated steel will have poor mechanical properties when cooled. In heating for forging, temperature is usually judges by the eye, but where large numbers of the same pattern are made, the piece to be forged are heated in furnaces in which the temperature is indicated by pyrometers , and often is automatically controlled.
在落锤锻中，一块金属坯料，粗糙的即大体像所要求零件形状那样，被放入到具有成品件那样精确形状的模面之间，然后施加压力使模具紧紧结合在一起以锻取模腔形状。这一方法广泛用来制造钢件和黄钢件。大型金属锭现在几乎都是用液压压力机来锻造的，而不用蒸汽锤。因为用压力机锻造，变形更加深透。将来压力机可对付冷金属锭并能加工得到更加精确的尺寸。锻造将在大约与辊轧同样的温度下进行，这种工艺正像轧制那样可改善金属的物理性能。最后火锻时，不使钢太热很重要，因为过热钢冷却后，其机械性能较差。为锻件加热，温度通常是以肉眼来判断的，但在生产大量相同锻件的场合，要锻造的坯件是在有高温计指示温度的炉子中来加热，并且常常是自动控制的。
5. Soldering and Welding
There are a number of methods of joining metal articles together, depending on the type of metal and the strength of the joint which is required.
把金属件连接在一起的方法有若干个，用哪一种方法，要根据金属种类和所要求的焊缝强度来决定。
Soldering is the process of joining two metals by a third metal to be applied in the molten state. Solder consists of tin and lead, while bismuth and cadmium are often included to lower the melting point. One of the most important operations in soldering is that of cleaning the surface to be joint, this may be done by some acid cleaner.
软焊是要用溶融状态的第三种金属来使两件金属连接在一起的工艺。焊料由锡和铅组成。而常常含有铋和镉。目的是要降低熔点。软钎焊中最重要的工序之一就是清理焊缝表面。这可以用某种酸性清除剂来进行。
Soldering gives a satisfactory joint for light articles of steel, copper or brass , but the strength of a soldered joint is rather less than a joint which is brazed , riveted or welded . These methods of joining metal are normally adopted for strong permanent joints.
软钎焊能为轻型钢件、铜件和黄铜件生产满意的焊缝，但软钎焊的焊缝强度比起硬钎焊、铆接和焊接来要弱些。连接金属的这些方法，通常用来产生强固的永久性的焊缝。
The simplest method of welding two pieces of metal together is known as pressure welding. The ends of metal are heated to a white heat-for iron, the welding temperature should about 1300C-in a flame . At this temperature the metal becomes plastic. The ends are then pressed or hammered together, and the joint is smoothed off. Care must be taken to ensure that the surfaces are thoroughly clean first, for dirt will weaken the weld. Moreover, the heating of iron or steel to a high temperature causes oxidation , and a film of oxide is formed on the heated surfaces. For this reason, a flux is applied to the heated metal. At welding heat, the flux melts, and the oxide particles are dissolved in it together with any other impurities which may be present. The metal surfaces are pressed together, and the flux is squeezed out from the center of the weld. A number of different types of weld may be used, but for fairly thick bars of metal, a v-shaped weld should normally be employed . It is rather stronger than the ordinary but weld.
把两件金属焊在一起的最简单的方法称做压力焊。用火焰把金属两端加热到白炽状态—铁的焊接温度为1300C左右—在这一温度下，金属变成塑性，然后对两端施压或锤击使之
结合在一起。最后再将焊缝清理千净。必须注意首先保证表面完全清洁，因脏物将会使焊缝强度削弱。此外，加热铸铁或钢到高温会引起氧化井在焊接表面形成氧化皮。因此用助焊剂施于加热的金属上。达到焊接温度时刻，助焊剂熔化，将氧化物粒子跟任何其他可能存在的杂质一起都熔解于助焊剂中，金属表面被压合在一起，而助焊剂就从焊缝中间被挤出。可能使用若干不同类型的焊缝，但对于颇为粗厚的金属件，通常使用V型焊缝。该焊缝比起普通的对接焊缝来要强固些。
The heat for fusion welding is generated in several ways, depending on the sort of metal which is being welded and on its shape. An extremely hot flame can be produced from an oxy-acetylene torch. For certain welds an electric arc is used. In this method, an electric current is passed across two electrodes , and the metal surfaces are placed between them. The electrodes are sometimes made of carbon, but more frequently they are metallic . The work itself constitutes one of them and the other is an insulated filler rod. An arc struck between the two, and the heat which is generated melts the metal at the weld. A different method is usually employed for welding sheets or plates of metal together. This is known as spot welding. Two sheets or plates are placed together with a slight overlap, and a current is passed between the electrodes. At welding temperature, a strong pressure is applied to the metal sheets. The oxide film, and any impurities which are trapped between the sheets, are squeezed out, and the weld is made.
可用几种方法来产生溶焊的热，用何种方法，要根据将要焊接的金属种类和根据其形状来决定。由氧乙炔焰可产生强烈的火焰。对于某种焊缝，可用电弧来焊接。在这一系列重要的焊接过程中，电弧可为熔化金属供热，而焊剂起着保护和清理焊缝的作用，而且常常也是起着熔炼控制作用。最广泛使用的助焊剂保护电弧焊的形式是一种称作金属弧焊的手工操作工艺。在这一方法中，电流经两个电极流过，而金属表面则被置于两电极之间。电极(电焊条)有时用碳棒制作，但更常用金属来制作。工件本身构成它们中的一极而另一极是一具有绝缘填充剂的焊条。两极之间电弧放电，由此产生的热去熔化在焊缝处的金属。通常使用不同的方法去把金属薄板或厚板焊接在一起。这就叫做点焊。两块薄板或厚板以边沿稍稍搭叠的方式放在一起，一电流从两极之间通过.达到焊接温度时刻，对金属板施加强压，氧化皮和陷入薄板中间任何杂质都会被挤出，而完成了焊缝连接.
6. Heat Treatment and Hot Working of Metals
We can alter the characteristics of steel in various ways. In the first place, steel which contains very little carbon will be milder than steel which contains a higher percentage of carbon, up to the limit of about 1.5%. Secondly, we can heat the steel above a certain critical temperature, and then allow it to cool at different rates. At this critical temperature, changes begin to take place in the molecular structure of the metal. In the process known as annealing , we heat the steel above the critical temperature and permit it to cool very slowly. This causes the metal to become softer than before, and much easier to machine. Annealing has a second advantage; it helps to relieve any internal stresses which exist in the metal. These stresses are liable to occur through hammering or working the metal, or thorough rapid cooling. Metal which we cause to cool rapidly contracts more rapidly on the outside than on the inside. This produces unequal contractions, which may give rise to distortion or cracking . Metal which cools slowly is less liable to have these internal stresses than metal which cools quickly.
On the other hand, we can make steel harder by rapid cooling. We heat it up beyond the
critical temperature, and then quench it in water or some other liquid. The rapid temperature drop fixes the structure change in the steel which occurred at the critical temperature, and makes it very hard. But a bar of this hardened steel is more liable to fracture than normal steel. We therefore heat it again to a temperature below the critical temperature, and cool it slowly. This treatment is called tempering . It helps to relieve the internal stresses, and makes the steel less brittle than before. The properties of tempered steel enable us to use it in the manufacture of tools which need fairly hard steel. High carbon steel is harder than tempered steel, but it is more difficult to work.
These heat treatments take place during the various shaping operations. We can obtain bars and sheets of steel by rolling the metal through huge rolls in a rolling mill . The roll pressures must be much greater for cold rolling than for hot rolling, but cold rolling enables the operators to produce rolls of great accuracy and uniformity , and with a better surface finish. Other shaping operations include drawing into wire, casting in moulds, and forging.
The mechanical working of metal is the shaping of metal in either a cold or hot state by some mechanical means. This does not include the shaping of metals by machine or grinding, in which processes metal is actually machined off, not does it include the casting of molten metal into some form by use of molds. In mechanical working processes, the metal is shaped by pressure-actually forging, bending , squeezing, drawing, or shearing it to its final shape. In these processes the metal may be either cold-or hot- worked. Although normal room temperatures are ordinarily used for cold working of steel, temperatures up to the recrystallization range are sometimes used. Hot working of metals takes place above the recrystallization or work-hardening range. For steel, recrystallization starts around 650 to 700C, although most hot work on steel is done at temperature considerably above this range. There is no tendency for hardening by mechanical work until the lower limit of the recrystalline range is reached. Some metals, such as lead and tin, have a low recrystalline range and can be hot-worked at room temperature, but most commercial metal require some heating. Alloy composition has a great influence upon the proper working range, the usual result being to raise the recrystalling range temperature. This range may also be increased by prior cold working.
7. Kinds of Steels, Mechanical Properties of Metals
There are two general kinds of steel: carbon steel and alloy steel. Carbon steel contains only iron and carbon, while alloy steel contains some other alloying elements such as nickel , chromium , manganese , molybdenum , tungsten , vanadium , etc.
1. Carbon steels
(1) Low carbon steel containing from 0.05 to 0.15 percent carbon; this steel is also known as machine steel.
(2) Medium carbon steel containing from 0.15 to 0.60 percent carbon.
(3) High carbon steel containing from 0.6 to 1.50 percent carbon: this steel is sometimes called "tool steel".
2. Alloy steels
(1) Special alloy steel, such as nickel steel, chromium steel.
(2) High-speed steel also known as self-hardening steel.
Carbon steels are the most common steels used in industry. The properties of these steels depend on the percentage of carbon they contain. Low-carbon steels are very soft and can be used
for bolts and for machine parts that do not need strength.
Medium carbon steel is a better grade and stronger than low carbon steel. It is also more difficult to cut than low carbon steel.
High carbon steel may be hardened by heating it to a certain temperature and then quickly cooling in water. The more carbon the steel contains and the quicker the cooling is, the harder it becomes. Because of its high strength and hardness, this grade of steel may be used for tools and working parts of machines.
But for some special uses, for example, for gears , bearings , springs , shafts and wire , carbon steels cannot be always used because they have no-properties needed for these parts.
Mechanical properties are the characteristic responses of a material to applied forces. The knowledge of mechanical properties of materials is very essential in order to construct a mechanically sound structure such as a bridge on the river. Mechanical properties can be determined by conducting experimental tests on the material specimen . Some important mechanical properties of materials are:
(1) Strength (in tension, compression, shear and bending)
(2) Stiffness
(3) Ductility
(4) Impact strength
(5) Hardness
(6) Toughness
1. Strength or mechanical strength of a material may be defined as the ability of the material to sustain loads without undue distortion or failure. Material should have adequate strength when subjected to tension, compression, shear, bending or torsion as per the intended use.
For example the crankshaft of an automobile should have proper torsion strength.
2. Stiffness. Stiffness is the ability of a material or shape to resist elastic deflection . For identical shapes, the stiffness is proportional to the modulus of elasticity . A material which deforms less under a given load is more stiff than on which deforms more.
难句翻译： Unit2 1There is no tendency for hardening by mechanical work until the lower limit of the crystlline range is reached. 没有倾向硬化机械工作直到crystlline下限达到的范围。 . 2The mechanical working of metal is the shaping of metal in either a cold or a hot state by some mechanical means. This does not include the shaping of metals by maching or grinding, in which processes metal is actually machined off, nor does it include the casting of molten metal into some form by use of molds. 在机械加工的金属成形的金属是要么在冷或热状态的一些机械设备。这并不包括成形的金属加工或磨,金属加工过程实际上是掉,也不包括铸造的熔融金属成某种形式的模具的使用。 3.Alloy composition has a great influence upon the proper working range, the usual result being to raise the re-crystalline range temperature. 合金成分具有很大的影响在适当的工作范围,通常的结果是提高再保险结晶温度范围。Unit3 1. 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. 连接是永久性的,在这个意义上,这并不意味着在有用的生活被打破的机器,但它可以被打破,恢复在紧急或当磨损部件所取代。 internal threads, for example, are seldom produced by any means other than machining and small holes in presswork parts may be machined following the press working operations. 内部线程,例如,很少产生的任何其他方式加工和小洞在印刷的部分可能被加工后的新闻工作操作。
Lesson 16 Basic Concepts of Mechanisms A combination of interrelated parts(相关零件的组合体) having definite（确定的）motions and capable of performing useful work may be called machine. 具有确定的运动轨迹,并且能做有用的功联接在一起的零件的组合称为机器. A mechanism is a component of a machine consisting of two or more bodies arranged so that the motion of one compels the motion of the others. 机构是机器的组成要素.机器由二个及以上的机构组合而成.因此其中一个构件的运动会带动其它的构件的连锁运动. Kinematics is the study of motion in mechanisms without reference to the forces that act on the mechanism 运动学仅研究机构的运动而不考虑作用在机构上的力. Dynamics is the study of motion individual bodies and mechanisms under the influence of forces and torques. 动力学研究独立构件的运动及力和扭矩作用下对机构的影响. The study of forces and torques in stationary systems (and systems with negligible inertial effects) is called statics 研究平衡中的力和扭矩,该系统忽略惯性影响,称之为静力学. Synthesis is the procedure by which a product (a mechanism, for example) is developed to satisfy a set of performance requirements 合成是一个程序,通过该程序能够不断改进一个产品(例如一个机构)直到满足一系列的性能要求. If a product configuration is tentatively specified and then examined to determine whether the performance requirements are met, the process is called analysis. 如果需要探索性的详细阐述产品的构造结构,然后检验,判断该产品是否满足性能要求,这个过程称为分解. The design of mechanisms involves both synthesis and analysis. 机构设计包括合成和分解. The design process begins with the recognition of a need. A set of requirements is then listed 设计从对于需求的确认开始,罗列出一系列的要求. Detailed analyses of displacements, velocities, and accelerations are usually required 通常需要对位移,速度,加速度进行具体分析. This part of the design process is followed by an analysis of forces and torques. 设计过程中的这个部分是紧跟在对力和扭矩的分析之后. The design process may continue long after（很久以后）the first models have been produced and may include redesigns of components that affect velocities, accelerations, forces, and torques 在制造完毕第一个模型之后,该设计过程仍有可能持续很长一段时间. 并且有可能会重新设计这些会影响速度,加速度及所知扭矩的零部件 In order to successfully compete from year to year, most manufactures must continuously modify their product and their methods of production 为了在年复一年的技术中取得优势,大多数制造商必须不断调整修改他们的产品及加工方式 .Increases in the production rate, upgrading of product performance, redesign for cost and weight reduction are frequently required ,为了增加出产率,提高产品的性能,经常需要重新设计来降低成本以及减轻重量. Success may hinge on（决定于） the accuracy of the kinematic and dynamic analysis 对问题进行正确的运动学和动力学分析是成功的关键. Many of the basic linkage configurations have been incorporated into（成为……的一部分）machines designed centuries ago, and the terms we use to describe them have changed over the years 很久以前,许多基本的连杆构造就已经运用在机器设计中去了,并且我们用来称呼它们的术语在不断的变化,. Thus, definitions and terminology are not consistent throughout thetechnical literature. 因此技术供应文献中的定义和说明不是一成不变的 In most cases, however, meanings will be clear from the context of the descriptive matter. 在大多数的情况下,然而定义,义意可以在的解释性的描述内容中清晰的获得, A few terms of particular interest to the study of kinematics and dynamics of machines are defined below 下面定义了在学习,研究机构运动学和动力学中一些特别重要的术语. Link A link is one of the rigid bodies or members joined together to form a kinematic chain. 杆件是一个刚体或者连接在一起形成运动链的零部件,因此被称为刚性构件或者是简单构件. The term rigid link, or sometimes simply link, is an idealization used in the study of mechanisms that does not consider small deflections due to strains in machine members 刚性构件是在机械装置中的理想化模型.这样就不无需考虑由机器零部件所产生的应力造成的微小偏移量. A perfectly rigid or inextensible link can exist only as a textbook type of model of a real machine member. 一个绝对刚性或不可延展的构件只能存在于教科书上的机械零部件的模型. For typical machine parts, the maximum changes in dimension are on the order of only a one-thousandth of the part length. 对于典型的零部件,最大的尺寸变化量仅仅是沿着该部件长度方向的千分之一. We are justified（合理的） in neglecting this small motion when considering the much greater motion characteristic of most mechanisms 当考虑到大多数的机构相对较为显着的运动特征,忽略这点微量的偏移是合情合理的. The word link is used in a general sense to include cams, gears, and other machine members in addition to cranks, connecting rods and other pin-connected（铰接）components 通常意义所说的杆件包括凸轮,齿轮以及它的机器零件的曲柄,连杆机构和其它的销件连接部分. Frame The fixed or stationary link in a mechanism is called the frame 机架机械装置中固定或静止不动的构件称为机架. When there is no link that is actually fixed, we may consider one as being fixed and determine the motion of the other links relative to it 如果实际中确实没有构件是固定的,我们可以假设其中某个是固定的,这样可以判断出其它与之相连构件的运动. In an automotive engine, for example, the engine block (see Fig.14.1) is considered the frame, even though the automobile may be moving 例如汽车发动机,我们通常是把发动机气缸视为机架,让它保持静止不动,实际上整部汽 车者是运动的. Degree of Freedom The number of degrees of freedom of a linkageis the number of independent parameters required to specify the position of every link relative to the frame or fixed link 自由度连杆机构的自由度是给定独立参数的数目，需要自由度来确定某一个与机架或固定杆件相连接的构件的位置， If the instantaneous configuration of a system may be completely defined be specifying one independent variable, that system has one degree of freedom 如果系统的瞬间结构完全可以由一个独立的变量来确定，这样系统就具有一个自由度，An unconstrained rigid body has six degrees of freedom: 大多数实际上运用的机构装置只有一个自由度。 translation in three coordinate directions and rotation about three coordinate axes 一个不受约束的刚体它有六个自由度，沿着三个坐标平面的平移和绕着三个坐标轴的转动。 If the body is restricted to motion in a place, there are three degrees of freedom: ?如果刚体受到约束在平面上移动，那么就有三个自由度， ?translation in two coordinate directions and rotation within the plane. 沿着两个坐标方向的移动以及在平面方向的转动。 Lower and Higher Pairs Connections between rigid bodies consist of lower and higher pairs of elements. 低副和高副刚体连接的构件由低副和高副组成， The two elements of a lower pair have theoretical surface contact with one another 低副的两个构件理论上是通过平面接触。 while the two elements of a higher pair have theoretical point or line contact (if we disregard deflections). 高副的两个构件理论上是点和线的接触（如果我们忽略变形）。 Kinematic Chain A kinematic chain is an assembly（集合） of links and pairs (joints). Each link in a closed-loop kinematic chain is connected to two or more other links 运动链是若干个构件或运动链联接结合在一起，在闭式运动链中，每个构件都有相同两个及两个以上的其它构件相连接, A linkage failing to meet the closed-loop criterion is an open-loop kinematic chain. 运动链没有满足闭式运动链的标准则称为开环运动链。 Linkage Since we may wish to examine kinematic chains without regard to their ultimate（最后） use, it is convenient to identify any assemblage of rigid bodies connected by kinematic joints as a linkage 连杆机构由于我们希望检验运动链而不考虑它们的最终用途,可以非常方便的区分出任何做为连接机构的刚体的集合,这些连杆机构刚体是通过运动链连接在一起的，Thus, both mechanisms and machines may be considered linkages 因此机构与机器都被视为连杆机构, In some references, however, the term linkage is restricted to kinematic chains made up of lower pairs. 然而在某些参考文献中,linkage这个词仅仅限于由低副组成的运动链。 Planar Motion and Planar Linkages If all points in a linkage may be described as a planar linkage 平面移动和平面连杆机构如果连杆机构上所有的点都同一平面内移动,则说明系统正在平移. If we examine the linkage made up of the crank, connecting rod, and piston in a piston engine, we see that it is a planar linkage. 在活塞发动机中由曲柄,连杆和活塞组成的连杆机构,我们视为平面连杆机构. Most of the mechanisms in common use may be treated as planar linkages. 大多数普遍使用的机械装置都被视平面连杆机构. Spatial Motion and Spatial Linkages 空间运动和空间连杆机构 The more general case in which motion cannot be described as taking place in parallel planes is called spatial motion, 在更多一般情况下,不能在平面内进行运动的称为空间运动. and the linkage may be described as a spatial or three-dimensional (3D) linkage. 该连杆机构被称为空间或三维连杆机构, Inversion The absolute motion of a linkage depends on which of the links is fixed, that is, which link is selected as the frame 连杆机构的绝对移动取决于哪根连杆是构件是固定的,简而言之就是选择哪根杆件做为机架, If two otherwise equivalent linkages(等效连杆机构) have different fixed link, 如果两根相当的连杆机构的固定机架是不同的, then each is an inversion of the other. Relative motion will be the same in both linkages.那么一个就是另外一个的倒置.这在两个连杆机构中相当的运动都是相 同的. 1 / 2
第一单元：梦想的阴暗之面 艾力克斯? 哈利 许多人怀有美好的愿望，期望能成为作家，但是能够梦想成真的人不多。艾力克斯? 哈利也想成为作家，可是他成功了。阅读下面这篇文章，看一看他成功的原因。 许多青年人对我说，他们想成为作家。我一直鼓励这样的人，但是我也向他们解释“成为作家”和写作之间存在着巨大的差别。多数情况下这些年轻人梦寐以求的是财富与名誉，从未想到要孤身一人长久地坐在打字机旁。“你们渴望的应该是写作，”我对他们说，“而不应该是当作家。” 事实上，写作是一项孤单寂寞而又收入微薄的工作。有一个被命运之神垂青的作家，就有成千上万个永远无法实现梦想的人。即使那些成功人士也经常受到长久的冷落，穷困不堪。我便是其中之一。 我放弃了在海岸警卫队做了二十年的工作，为的是成为一名自由撰稿人，这时，我根本没有前途可言。我所拥有的只是一位住在纽约市的朋友，乔治? 西姆斯，他和我是在田纳西州的赫宁一起长大的。乔治为我找了个家，位于格林威治村公寓大楼中的一间腾空的储藏室，而他是那幢大楼的管理员。房子里冷嗖嗖的，没有卫生间，不过这没什么。我马上买了一台旧的手动打字机，感觉自己颇象一位名符其实的作家。 然而，大约一年后，我的写作生涯依然没有任何起色，我开始怀疑自己。卖出一篇小说是如此艰难，以至我几乎填不饱肚子。但是，我清楚的是我想写作，我已梦寐以求了许多年。我并不准备成为一名到死时还在想假如的人。我会坚持把我的梦想付诸实践--即使这梦想意味着不稳定的生活和对失败的恐惧。这是希望的阴暗面，任何心存梦想的人都必须学会在这阴暗面下生存。 后来有一天，我接到了一个电话，由此改变了我的一生。这并不是一位代理人或编辑打来电话，主动要求与我签大的稿约。恰恰相反--是一声鸣笛，诱使我放弃梦想。打电话来的是海岸警卫队的老熟人，现在在旧金山。他曾经借给我几美元，喜欢催我还给他。“我什么时候才能拿到那十五美元，艾力克斯？”他逗我说。 “等我下一次卖出作品吧。” “我有个好主意，”他说，“我们这儿需要一位新的公共信息管理员，年薪六千美元。若想干，那就是你的了。” 年薪六千美元！这个数目在1960年可真是值钱啊。我可以有一套上好的公寓，一辆二手车，可以还清债务，也许还可有些结余。另外，我还可以业余写作。 当这些美元在我的脑海里晃动时，某种东西却使我神志清醒起来。我的内心深处升起一个坚强的信念。我曾经梦想成为一名作家--一名专业作家。那才是我的追求。“谢谢你，但是我不去，”我听见自己在说。“我会坚持到底来写作。” 后来，我在蜗居里踱来踱，开始觉得自己象个傻瓜。我打开橱柜--一只钉在墙上的桔黄色板条箱--把里面的东西全部弄了出来：两罐沙丁鱼。我把手伸进口袋，只摸出十八美分。我把罐头和硬币一起塞进一个皱巴巴的纸袋中。你看，艾力克斯，我自言自语道，你迄今为止努力的结果都在这里。我不知道，自己是不是曾经情绪如此低落过。 我希望自己能说，情况马上开始好转。但是并没有。感谢上帝，幸亏有乔治帮我渡过了难关。 通过乔治，我结识了另外一些正在艰苦奋斗的艺术家，象乔? 德拉尼，一位来自田纳西州科诺科斯威尔市的老画家。乔经常常没吃饭的钱，于是就去光顾附近社区的一位屠户和一个食品商。屠户会送给他一些带点肉的大骨头，从食品商那里他可以弄到一些枯萎的蔬菜。
机械工程专业英语第一课 机械工程专业英语概述 English in Mechanical Engineering 一、专业英语概述 1. 什么是翻译： 翻译就是将一种语言文字的意义用另?a种语言文字表达出来。 机械工程英语翻译就是将机械工程学科的英语原著由原作语言(source language)用译文语言(target language)忠实、准确、严谨、通顺、完整地再现出来，使人们能够借助汉语译文准确无误地了解英语机械工程著作所阐述的工程技术内容和科学理论。 机械工程专业英语概述 English in Mechanical Engineering 2. 翻译例句 例1. Control Center, Smoking Free. 例2. The tolerance should not be so big. 例3. A dog driver stop the rotation of the wheel. 例 4. Connect the black pigtail with the dog-house. 例5. The importance of computer in the use of manufacturing can not be overestimated. 机械工程专业英语概述 English in Mechanical Engineering 例1. Control Center, Smoking Free. 错误译法：控制中心，吸烟自由。 正确译法：控制中心，严禁吸烟。 例2. The tolerance should not be so big. a. 此公差不应给这么大。（机械学） b. 忍耐力不会有这么大。(关于人体的耐受性) c. 抗毒性不会有这么强。（医学） 例3. A dog driver stop the rotation of the wheel. 错误译法：狗驾驶员使轮子停转。 专业译法：止动器使轮子停止旋转。 机械工程专业英语概述 English in Mechanical Engineering 例4. Connect the black pigtail with the dog-house. 错误译法：把黑色的猪尾巴系在狗窝上。 专业译法：将黑色的引出线接在高频高压电源屏罩上。例 5. The importance of computer in the use of manufacturing can not be overestimated. 错误译法：计算机在制造业应用上的重要性不能被估计过高。 正确译法：计算机在制造业应用上的重要性怎么估计也不会过高。 机械工程专业英语概述 English in Mechanical Engineering 3.专业英语与基础英语的不同： 首先，专业英语在词义上具有不同于基础英语的特点和含义。掌握专业词汇是学好专业英语的基础，专业词汇的含义和上下文有关，因此查阅专业书籍的Index并参照课文确定词意是学习和掌握专业词汇的有效方法。 其次，英语科技文章在结构上也具有很多自身的特点，如长句多，被动语态多，大量的名词化结构等，这都给对英文原文的理解和翻译带来了基础英语中很难解决的困难。 再者，专业英语对听说读写译的侧重点不同，其主要要求在于“读”和“译”，也就是通过大量的阅读对外文资料进行正确的理解和翻译，在读和译的基础上，对听、说、写进行必要的训练。 机械工程专业英语概述 English in Mechanical Engineering 此外，专业外文资料由于涉及科技内容而往往极为复杂难以理解，加之这类文章的篇幅通常很长，所以只有经过一定的专业外语训练，才能完成从基础英语到专业英语的过渡，达到英语学以致用的最终目的。 作为工程技术人员，阅读专业英语文献的目的是理解掌握文献所叙述的理论或方法，以便在科研或生产实践中实施这些理论方法，或是进一步发展改进这些理论方法。为了达到这些目的，首先要准确地理解原文。另一方面科技文献的写作特点是严谨，简洁。在论述理论和方法时一般都只给出重要的步骤。对有关的基础知识一般不详细阐述，也不给出公式的详细推导过程。 机械工程专业英语概述 English in Mechanical Engineering 读者往往需要通过认真地思索才能俯所述的关键问题。因此专业英语阅读与普通英语的快速阅读方法也有所不同，专业英语阅读要把准确理解放在首
1. Metals and Their Use It is known that metals are very important in our life. Metals have the greatest importance for industry. All machines and other engineering constructions have metal parts; some of them consist only of metal parts. There are two large groups of metals: 1) Simple metal- more or less pure chemical elements 2) Alloys - materials consisting of a simple metal combined with some other elements. About two thirds of all elements found in the earth are metals, but not all metals may be used in industry. Those metals which are used in industry are called engineering metals. The most important engineering metal is iron , which in the form of alloys with carbon and other elements, finds greater use than any other metal. Metals consisting of iron combined with some other elements are known as ferrous metals; all the other metals are called nonferrous metals. The most important nonferrous metal are copper , aluminum , lead , zinc , tin , but all these metals are used much less than ferrous metals, because the ferrous metals are much cheaper. Engineering metals are used in industry in the form of alloys because the properties of alloys are much better than the properties of pure metals. Only aluminum may be largely used in the form of simple metal. Metals have such a great importance because of their useful properties or their strength, hardness, and their plasticity . Different metals are produced in different ways, but almost all the metal are found in the forms of metal ore (iron ore, copper ore, etcet cetra.) The ore is a mineral consistence of a metal combined with some impurities . In order to produce a metal from some metal ore, we must separate these impurities from the metal that is done by metallurgy . 2. Plastics and Other Materials Plastics have specific properties which may make them preferable to traditional materials for certain uses. In comparison with metals, for example, plastics have both advantages and disadvantages. Metals tend to be corroded by inorganic acids , such as sulphuric acid and hydrochloric acid. Plastics tend to be resistant to these acids, but can have dissolved or deformed by solvent , such as carbon tetrachloride , which have the same carbon base as the plastics. Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigid than most plastics while plastics are very light, with a specific gravity normally between 0.9 and 1.8. Most plastics do not readily conduct heat or electricity . Plastics soften slowly and can easily be shaped when they are soft. 塑料具有特殊的性能。对于某种用途而言，这些性能使得塑料比传统材料更为可取。例如，跟金属相比较，塑料既有优点也有缺点。金属易受到无机酸的腐蚀，如硫酸和盐酸，塑料能抵抗这些酸的腐蚀，但可被溶剂所洛解或引起变形，例如溶剂四氯化碳与塑料具有同样的碳基。颜色必定只能涂到金属的表面。而它可以跟塑料混合为一体。金属比大多数塑料刚性要好，而塑料则非常之轻，通常塑料密度在0. 9-1. 8之间。大多数塑料不易传热导电。塑料能缓慢软化，而当其还是在软的状态时，能容易成形。
1.With low-power machinery or vehicles the operator can usually apply sufficient force through a simple mechanical linkage from the pedle or handle to the stationary part of the brake. In many cases, however, this force must be multiplied by using an elaborate braking system（P5.） 用低能机器或传力工具，操作者通过向踏板或把手的一个简单机械连接构件作用足够的力 量到车闸固定的部分。大多数情况，然而，用一个详细（复杂）的车闸系统使这个力量成 倍增加。 2.The fundamental principle involved is the use of compressed air acting through a piston in a cylinder to set block brakes on the wheels. The action is simultaneous on the wheels of all the cars in the train. The compressed air is carried through a strong hose from car to car with couplings between cars; its release to all the separate block brake units, at the same time, is controlled by the engineer. (Braking Systems)（ P5） 相关的基本原理是使用压缩气体，通过气缸内的活塞将闸块压在车轮起作用。列车的所有 车厢上的车轮同时动作。压缩气体通过一个坚固的管道在由联轴器连接的车厢之间传输； 工程师控制其在同一时间释放到所有独立的闸块单元。 3.When the brake pedal of an automobile is depressed,a force is applied to a piston in a master cylinder.The piston forces hydraulic fluid through metal tubing into a cylinder in each wheel where the fluid ’ s pressure moves two pistons that press the brake shoes against the drum. (Braking Systems)（P5） 当踩下汽车刹车的踏板，在主汽缸中的活塞上施加一个力。活塞驱动液压流体通过金属管 道进入每个车轮气缸，在那里液压移动两个活塞将闸片压向轮圈。 4.Machinery ontology including mechanical rack, mechanical connections and mechanical transmission, which is the basis of mechanical-electrical integration, plays a role in supporting the other functional units of the system and transmitting motion and power. Compared to purely mechanical products, the performance and functionality of integration technology in electrical and mechanical systems have been improved a lot, which requires mechanical ontology to adapt its new status in mechanical structure, materials, processing technology, as well as the areas of geometry. Accordingly, the new ontology is with high efficient, multi-functional, reliable and energy-saving, small, light-weighted and aesthetically pleasing characteristics. (Mechatronics System) （ P7） 机械体包括机架、机械联接和机械传动，它是机电一体化的基础，作用是支撑系统其他功 能单元，传递运动和动力。和纯机械产品相比，一体化技术的性能和功能在机电系统中大 幅提高，它要求机械本体适应在机械结构、材料、加工技术以及这些领域中的几何学下的 新环境。相应的，新的一体化具有高效、多功能、可靠、节能、小轻和美学的令人赏心悦 目的特征。 5.Detecting sensor detecting sensor part includes a variety of sensors and signal detection circuit, and its function is to detect the process of mechatronic systems in the work itself and the changes of relevant parameters in external environment and transmit the information to the electronic control unit. Electronic control unit check the information and sends the corresponding control issues to the actuator. (Mechatronics System)（P7） 检测传感器部分包括各类传感器、信号检测电路，它的功能是检测机电系统自身工作的工 程，在外部环境下的相关参数的改变，将其信息传给电子控制单元。电子控制单元通过检 查信息，送出相应的指令到执行机构。 6.Electronic control unit, also known as ECU, is the core of mechatronic systems, responsible for the external commands and the signals output by sensors. It centralizes stores, computes and analyzes the information. Based on the results of information processing,instruction are issued according to a certain extent and pace to control the destination for the entire system. (Mechatronics System) （ P7） 电子控制单元，也被称为控制单元（ ECU）控制，是机电系统的核心，负责外部命令和传 感器的信号输出。它集中、存储、计算并分析信息。基于信息处理的结果，按照一定的范围 和步调发出命令来实现控制整个系统的目标。 7. It is put into a fairly standard machine tool that has had position sensing and motors on the
机械工程专业英语参考译文 机械工程专业英语参考译文 机械工程是一门涉及设计、制造、控制和维护机械系统的学科，涉及到许多不同的领域，包括制造业、航空航天、汽车、能源和医疗设备等。机械工程专业英语是机械工程领域中非常重要的语言工具，以下是一些常见的机械工程专业英语词汇和短语: 1. Machine Tools - 机器工具 Machine tools are tools that are used to perform precision machining operations on materials. They include drills, mills, lathes, routers, and other tools that are used to create precision parts and assemblies. 2. Material - 材料 Material is any substance that is in a solid, liquid, or gas state. It can be made from a variety of materials, such as metals, ceramics, plastics, and papers. In engineering, material refers to the physical and chemical properties of a material that determine its behavior in a particular application. 3. Design - 设计 Design refers to the process of creating a plan or concept for a particular object or system. It involves analyzing the needs and requirements of a particular application, and then