机械工程英语第二版翻译

1、第一单元 Types of Materials 材料的类型 Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materials. 材料可以按多种方法分类。科学家常根据状态将材料分为：固体、液体或气体。他们也把材料分为有机材料(曾经有生命的)和无机材料(从

2、未有生命的)。 For industrial purposes, materials are divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and become parts of products. 就工业效用而言，材料被分为工程材料和非工程材料。那些用于加工制造并成为产品组成部分的就是工程材料。Nonengineering materials are the chemicals, fuels, lubrica

3、nts, and other materials used in the manufacturing process, which do not become part of the product.非工程材料则是化学品、燃料、润滑剂以及其它用于加工制造过程但不成为产品组成部分的材料。 Engineering materials may be further subdivided into: Metal Ceramics Composite Polymers, etc. 工程材料还能进一步细分为：金属材料陶瓷材料复合材料 聚合材料，等等。 Metals and Metal Alloys 金属和

4、金属合金 Metals are elements that generally have good electrical and thermal conductivity. Many metals have high strength, high stiffness, and have good ductility. 金属就是通常具有良好导电性和导热性的元素。许多金属具有高强度、高硬度以及良好的延展性。Some metals, such as iron, cobalt and nickel, are magnetic. At low temperatures, some metals and

5、intermetallic compounds become superconductors.某些金属能被磁化，例如铁、钴和镍。在极低的温度下，某些金属和金属化合物能转变成超导体。 What is the difference between an alloy and a pure metal? Pure metals are elements which come from a particular area of the periodic table. Examples of pure metals include copper in electrical wires and alumin

6、um in cooking foil and beverage cans. 合金与纯金属的区别是什么？纯金属是在元素周期表中占据特定位置的元素。例如电线中的铜和制造烹饪箔及饮料罐的铝。Alloys contain more than one metallic element. Their properties can be changed by changing the elements present in the alloy. Examples of metal alloys include stainless steel which is an alloy of iron, nickel

7、, and chromium; and gold jewelry which usually contains an alloy of gold and nickel.合金包含不止一种金属元素。合金的性质能通过改变其中存在的元素而改变。金属合金的例子有：不锈钢是一种铁、镍、铬的合金，以及金饰品通常含有金镍合金。 Why are metals and alloys used? Many metals and alloys have high densities and are used in applications which require a high mass-to-volume rat

8、io. 为什么要使用金属和合金？许多金属和合金具有高密度，因此被用在需要较高质量体积比的场合。Some metal alloys, such as those based on aluminum, have low densities and are used in aerospace applications for fuel economy. Many alloys also have high fracture toughness, which means they can withstand impact and are durable.某些金属合金，例如铝基合金，其密度低，可用于航空

9、航天以节约燃料。许多合金还具有高断裂韧性，这意味着它们能经得起冲击并且是耐用的。 What are some important properties of metals? Density is defined as a materials mass divided by its volume. Most metals have relatively high densities, especially compared to polymers. 金属有哪些重要特性？ 密度定义为材料的质量与其体积之比。大多数金属密度相对较高，尤其是和聚合物相比较而言。Materials with high d

10、ensities often contain atoms with high atomic numbers, such as gold or lead. However, some metals such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight.高密度材料通常由较大原子序数原子构成，例如金和铅。然而，诸如铝和镁之类的一些金属则具有低密度，并被用于既需要金属

11、特性又要求重量轻的场合。 Fracture toughness can be described as a materials ability to avoid fracture, especially when a flaw is introduced. Metals can generally contain nicks and dents without weakening very much, and are impact resistant. A football player counts on this when he trusts that his facemask wont

12、shatter. 断裂韧性可以描述为材料防止断裂特别是出现缺陷时不断裂的能力。金属一般能在有缺口和凹痕的情况下不显著削弱，并且能抵抗冲击。橄榄球运动员据此相信他的面罩不会裂成碎片。 Plastic deformation is the ability of bend or deform before breaking. As engineers, we usually design materials so that they dont deform under normal conditions. You dont want your car to lean to the east afte

13、r a strong west wind. 塑性变形就是在断裂前弯曲或变形的能力。作为工程师，设计时通常要使材料在正常条件下不变形。没有人愿意一阵强烈的西风过后自己的汽车向东倾斜。However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they break.然而，有时我们也能利用塑性变形。汽车上压皱的区域在它们断裂前通过经历塑性变形来吸收能量。 The ato

14、mic bonding of metals also affects their properties. In metals, the outer valence electrons are shared among all atoms, and are free to travel everywhere. Since electrons conduct heat and electricity, metals make good cooking pans and electrical wires. 金属的原子连结对它们的特性也有影响。在金属内部，原子的外层阶电子由所有原子共享并能到处自由移动

15、。由于电子能导热和导电，所以用金属可以制造好的烹饪锅和电线。It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal. No photons pass through.因为这些阶电子吸收到达金属的光子，所以透过金属不可能看得见。没有光子能通过金属。 Alloys are compounds consisting of more than one metal. Adding other metals can affe

16、ct the density, strength, fracture toughness, plastic deformation, electrical conductivity and environmental degradation. 合金是由一种以上金属组成的混合物。加一些其它金属能影响密度、强度、断裂韧性、塑性变形、导电性以及环境侵蚀。For example, adding a small amount of iron to aluminum will make it stronger. Also, adding some chromium to steel will slow t

17、he rusting process, but will make it more brittle.例如，往铝里加少量铁可使其更强。同样，在钢里加一些铬能减缓它的生锈过程，但也将使它更脆。 Ceramics and Glasses陶瓷和玻璃 A ceramic is often broadly defined as any inorganic nonmetallic material By this definition, ceramic materials would also include glasses; however, many materials scientists add t

18、he stipulation that “ceramic” must also be crystalline. 陶瓷通常被概括地定义为无机的非金属材料。照此定义，陶瓷材料也应包括玻璃；然而许多材料科学家添加了“陶瓷”必须同时是晶体物组成的约定。 A glass is an inorganic nonmetallic material that does not have a crystalline structure. Such materials are said to be amorphous. 玻璃是没有晶体状结构的无机非金属材料。这种材料被称为非结晶质材料。Properties of

19、Ceramics and Glasses Some of the useful properties of ceramics and glasses include high melting temperature, low density, high strength, stiffness, hardness, wear resistance, and corrosion resistance.陶瓷和玻璃的特性 高熔点、低密度、高强度、高刚度、高硬度、高耐磨性和抗腐蚀性是陶瓷和玻璃的一些有用特性。Many ceramics are good electrical and thermal in

20、sulators. Some ceramics have special properties: some ceramics are magnetic materials; some are piezoelectric materials; and a few special ceramics are superconductors at very low temperatures. Ceramics and glasses have one major drawback: they are brittle.许多陶瓷都是电和热的良绝缘体。某些陶瓷还具有一些特殊性能：有些是磁性材料，有些是压电材

21、料，还有些特殊陶瓷在极低温度下是超导体。陶瓷和玻璃都有一个主要的缺点：它们容易破碎。 Ceramics are not typically formed from the melt. This is because most ceramics will crack extensively (i.e. form a powder) upon cooling from the liquid state. 陶瓷一般不是由熔化形成的。因为大多数陶瓷在从液态冷却时将会完全破碎(即形成粉末)。Hence, all the simple and efficient manufacturing techniq

22、ues used for glass production such as casting and blowing, which involve the molten state, cannot be used for the production of crystalline ceramics. Instead, “sintering” or “firing” is the process typically used. 因此，所有用于玻璃生产的简单有效的诸如浇铸和吹制这些涉及熔化的技术都不能用于由晶体物组成的陶瓷的生产。作为替代，一般采用“烧结”或“焙烧”工艺。In sintering,

23、ceramic powders are processed into compacted shapes and then heated to temperatures just below the melting point. At such temperatures, the powders react internally to remove porosity and fully dense articles can be obtained.在烧结过程中，陶瓷粉末先挤压成型然后加热到略低于熔点温度。在这样的温度下，粉末内部起反应去除孔隙并得到十分致密的物品。 An optical fibe

24、r contains three layers: a core made of highly pure glass with a high refractive index for the light to travel, a middle layer of glass with a lower refractive index known as the cladding which protects the core glass from scratches and other surface imperfections, and an out polymer jacket to prote

25、ct the fiber from damage. 光导纤维有三层：核心由高折射指数高纯光传输玻璃制成，中间层为低折射指数玻璃，是保护核心玻璃表面不被擦伤和完整性不被破坏的所谓覆层，外层是聚合物护套，用于保护光导纤维不受损。In order for the core glass to have a higher refractive index than the cladding, the core glass is doped with a small, controlled amount of an impurity, or dopant, which causes light to tr

26、avel slower, but does not absorb the light. 为了使核心玻璃有比覆层大的折射指数，在其中掺入微小的、可控数量的能减缓光速而不会吸收光线的杂质或搀杂剂。Because the refractive index of the core glass is greater than that of the cladding, light traveling in the core glass will remain in the core glass due to total internal reflection as long as the light s

27、trikes the core/cladding interface at an angle greater than the critical angle. 由于核心玻璃的折射指数比覆层大，只要在全内反射过程中光线照射核心/覆层分界面的角度比临界角大，在核心玻璃中传送的光线将仍保留在核心玻璃中。The total internal reflection phenomenon, as well as the high purity of the core glass, enables light to travel long distances with little loss of inte

28、nsity.全内反射现象与核心玻璃的高纯度一样，使光线几乎无强度损耗传递长距离成为可能。 Composites 复合材料 Composites are formed from two or more types of materials. Examples include polymer/ceramic and metal/ceramic composites. Composites are used because overall properties of the composites are superior to those of the individual components.

29、复合材料由两种或更多材料构成。例子有聚合物/陶瓷和金属/陶瓷复合材料。之所以使用复合材料是因为其全面性能优于组成部分单独的性能。For example: polymer/ceramic composites have a greater modulus than the polymer component, but arent as brittle as ceramics. Two types of composites are: fiber-reinforced composites and particle-reinforced composites.例如：聚合物/陶瓷复合材料具有比聚合物

30、成分更大的模量，但又不像陶瓷那样易碎。 复合材料有两种：纤维加强型复合材料和微粒加强型复合材料。Fiber-reinforced Composites Reinforcing fibers can be made of metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon fibers. Fibers increase the modulus of the matrix material. 纤维加强型复合材料 加强纤维可以是金属、陶瓷、玻璃或是已变成石墨的被称

31、为碳纤维的聚合物。纤维能加强基材的模量。The strong covalent bonds along the fibers length give them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved.沿着纤维长度有很强结合力的共价结合在这个方向上给予复合材料很高的模量，因为要损坏或拉伸纤维就必须破坏或移除这种结合。 Fibers are difficult to process into composites

32、, making fiber-reinforced composites relatively expensive. 把纤维放入复合材料较困难，这使得制造纤维加强型复合材料相对昂贵。Fiber-reinforced composites are used in some of the most advanced, and therefore most expensive sports equipment, such as a time-trial racing bicycle frame which consists of carbon fibers in a thermoset polyme

33、r matrix. 纤维加强型复合材料用于某些最先进也是最昂贵的运动设备，例如计时赛竞赛用自行车骨架就是用含碳纤维的热固塑料基材制成的。Body parts of race cars and some automobiles are composites made of glass fibers (or fiberglass) in a thermoset matrix. 竞赛用汽车和某些机动车的车体部件是由含玻璃纤维(或玻璃丝)的热固塑料基材制成的。 Fibers have a very high modulus along their axis, but have a low modulu

34、s perpendicular to their axis. Fiber composite manufacturers often rotate layers of fibers to avoid directional variations in the modulus. 纤维在沿着其轴向有很高的模量，但垂直于其轴向的模量却较低。纤维复合材料的制造者往往旋转纤维层以防模量产生方向变化。Particle-reinforced composites Particles used for reinforcing include ceramics and glasses such as small

35、 mineral particles, metal particles such as aluminum, and amorphous materials, including polymers and carbon black.微粒加强型复合材料 用于加强的微粒包含了陶瓷和玻璃之类的矿物微粒，铝之类的金属微粒以及包括聚合物和碳黑的非结晶质微粒。 Particles are used to increase the modulus of the matrix, to decrease the permeability of the matrix, to decrease the ductili

36、ty of the matrix. An example of particle-reinforced composites is an automobile tire which has carbon black particles in a matrix of polyisobutylene elastomeric polymer. 微粒用于增加基材的模量、减少基材的渗透性和延展性。微粒加强型复合材料的一个例子是机动车胎，它就是在聚异丁烯人造橡胶聚合物基材中加入了碳黑微粒。Polymers Size. Single polyme molecules typically have molec

37、ular weights between 10,000 and 1,000,000g/molthat第二单元 The understanding of heat treatment is embraced by the broader study of metallurgy. Metallurgy is the physics, chemistry, and engineering related to metals from ore extraction to the final product. 对热处理的理解包含于对冶金学较广泛的研究。冶金学是物理学、化学和涉及金属从矿石提炼到最后产物的

38、工程学。Heat treatment is the operation of heating and cooling a metal in its solid state to change its physical properties. According to the procedure used, steel can be hardened to resist cutting action and abrasion, or it can be softened to permit machining. 热处理是将金属在固态加热和冷却以改变其物理性能的操作。按所采用的步骤，钢可以通过硬化

39、来抵抗切削和磨损，也可以通过软化来允许机加工。With the proper heat treatment internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior. The analysis of the steel must be known because small percentages of certain elements, notably carbon, greatly affect the

40、 physical properties.使用合适的热处理可以去除内应力、细化晶粒、增加韧性或在柔软材料上覆盖坚硬的表面。因为某些元素(尤其是碳)的微小百分比极大地影响物理性能，所以必须知道对钢的分析。 Alloy steel owe their properties to the presence of one or more elements other than carbon, namely nickel, chromium, manganese, molybdenum, tungsten, silicon, vanadium, and copper. Because of their

41、improved physical properties they are used commercially in many ways not possible with carbon steels. 合金钢的性质取决于其所含有的除碳以外的一种或多种元素，如镍、铬、锰、钼、钨、硅、钒和铜。由于合金钢改善的物理性能，它们被大量使用在许多碳钢不适用的地方。 The following discussion applies principally to the heat treatment of ordinary commercial steels known as plain carbon st

42、eels. With this process the rate of cooling is the controlling factor, rapid cooling from above the critical range results in hard structure, whereas very slow cooling produces the opposite effect. 下列讨论主要针对被称为普通碳钢的工业用钢而言。热处理时冷却速率是控制要素，从高于临界温度快速冷却导致坚硬的组织结构，而缓慢冷却则产生相反效果。 A Simplified Iron-carbon Diagr

43、am简化铁碳状态图 If we focus only on the materials normally known as steels, a simplified diagram is often used. 如果只把注意力集中于一般所说的钢上，经常要用到简化铁碳状态图。Those portions of the iron-carbon diagram near the delta region and those above 2% carbon content are of little importance to the engineer and are deleted. A simpl

44、ified diagram, such as the one in Fig.2.1, focuses on the eutectoid region and is quite useful in understanding the properties and processing of steel. 铁碳状态图中靠近三角区和含碳量高于2%的那些部分对工程师而言不重要，因此将它们删除。如图2.1所示的简化铁碳状态图将焦点集中在共析区，这对理解钢的性能和处理是十分有用的。 The key transition described in this diagram is the decomposit

45、ion of single-phase austenite() to the two-phase ferrite plus carbide structure as temperature drops. 在此图中描述的关键转变是单相奥氏体() 随着温度下降分解成两相铁素体加渗碳体组织结构。Control of this reaction, which arises due to the drastically different carbon solubility of austenite and ferrite, enables a wide range of properties to b

46、e achieved through heat treatment.控制这一由于奥氏体和铁素体的碳溶解性完全不同而产生的反应，使得通过热处理能获得很大范围的特性。 To begin to understand these processes, consider a steel of the eutectoid composition, 0.77% carbon, being slow cooled along line x-x in Fig.2.1. At the upper temperatures, only austenite is present, the 0.77% carbon b

47、eing dissolved in solid solution with the iron. When the steel cools to 727(1341), several changes occur simultaneously. 为了理解这些过程，考虑含碳量为0.77%的共析钢，沿着图2.1的x-x线慢慢冷却。在较高温度时，只存在奥氏体，0.77%的碳溶解在铁里形成固溶体。当钢冷却到727 (1341)时，将同时发生若干变化。 The iron wants to change from the FCC austenite structure to the BCC ferrite s

48、tructure, but the ferrite can only contain 0.02% carbon in solid solution. 铁需要从面心立方体奥氏体结构转变为体心立方体铁素体结构，但是铁素体只能容纳固溶体状态的0.02%的碳。The rejected carbon forms the carbon-rich cementite intermetallic with composition Fe3C. In essence, the net reaction at the eutectoid is austenite 0.77%Cferrite 0.02%C+cemen

49、tite 6.67%C.被析出的碳与金属化合物Fe3C形成富碳的渗碳体。本质上，共析体的基本反应是奥氏体0.77%的碳铁素体0.02%的碳+渗碳体6.67%的碳。 Since this chemical separation of the carbon component occurs entirely in the solid state, the resulting structure is a fine mechanical mixture of ferrite and cementite. Specimens prepared by polishing and etching in a

50、 weak solution of nitric acid and alcohol reveal the lamellar structure of alternating plates that forms on slow cooling. 由于这种碳成分的化学分离完全发生在固态中，产生的组织结构是一种细致的铁素体与渗碳体的机械混合物。通过打磨并在弱硝酸酒精溶液中蚀刻制备的样本显示出由缓慢冷却形成的交互层状的薄片结构。This structure is composed of two distinct phases, but has its own set of characteristic

51、 properties and goes by the name pearlite, because of its resemblance to mother- of- pearl at low magnification.这种结构由两种截然不同的状态组成，但它本身具有一系列特性，且因与低倍数放大时的珠母层有类同之处而被称为珠光体。 Steels having less than the eutectoid amount of carbon (less than 0.77%) are known as hypo-eutectoid steels. Consider now the transf

52、ormation of such a material represented by cooling along line y-y in Fig.2.1. 含碳量少于共析体(低于0.77%)的钢称为亚共析钢。现在来看这种材料沿着图2.1中y-y 线冷却的转变情况。At high temperatures, the material is entirely austenite, but upon cooling enters a region where the stable phases are ferrite and austenite. Tie-line and level-law cal

53、culations show that low-carbon ferrite nucleates and grows, leaving the remaining austenite richer in carbon.在较高温度时，这种材料全部是奥氏体，但随着冷却就进入到铁素体和奥氏体稳定状态的区域。由截线及杠杆定律分析可知，低碳铁素体成核并长大，剩下含碳量高的奥氏体。At 727(1341), the austenite is of eutectoid composition (0.77% carbon) and further cooling transforms the remainin

54、g austenite to pearlite. The resulting structure is a mixture of primary or pro-eutectoid ferrite (ferrite that formed above the eutectoid reaction) and regions of pearlite.在727(1341)时，奥氏体为共析组成(含碳量0.77%)，再冷却剩余的奥氏体就转化为珠光体。作为结果的组织结构是初步的共析铁素体(在共析反应前的铁素体)和部分珠光体的混合物。 Hypereutectoid steels are steels that

55、 contain greater than the eutectoid amount of carbon. When such steel cools, as shown in z-z of Fig.2.1 the process is similar to the hypo-eutectoid case, except that the primary or pro-eutectoid phase is now cementite instead of ferrite. 过共析钢是含碳量大于共析量的钢。当这种钢冷却时，就像图2.1的z-z线所示，除了初步的共析状态用渗碳体取代铁素体外，其余类

56、似亚共析钢的情况。As the carbon-rich phase forms, the remaining austenite decreases in carbon content, reaching the eutectoid composition at 727(1341). As before, any remaining austenite transforms to pearlite upon slow cooling through this temperature.随着富碳部分的形成，剩余奥氏体含碳量减少，在727(1341)时达到共析组织。就像以前说的一样，当缓慢冷却到这温

57、度时所有剩余奥氏体转化为珠光体。 It should be remembered that the transitions that have been described by the phase diagrams are for equilibrium conditions, which can be approximated by slow cooling. With slow heating, these transitions occur in the reverse manner. 应该记住由状态图描述的这种转化只适合于通过缓慢冷却的近似平衡条件。如果缓慢加热，则以相反的方式发生这种转化。However, when alloys are cooled rapidly, entirely diff