1、机械工程英语翻译叶邦彦陈统坚第2版59页wordUnit1 Advanced Engineering Materials单靠“死”记还不行,还得“活”用,姑且称之为“先死后活”吧。让学生把一周看到或听到的新鲜事记下来,摒弃那些假话套话空话,写出自己的真情实感,篇幅可长可短,并要求运用积累的成语、名言警句等,定期检查点评,选择优秀篇目在班里朗读或展出。这样,即巩固了所学的材料,又锻炼了学生的写作能力,同时还培养了学生的观察能力、思维能力等等,达到“一石多鸟”的效果。 Types of Materials观察内容的选择，我本着先静后动，由近及远的原则，有目的、有计划的先安排与幼儿生活接近的，能理解
2、的观察内容。随机观察也是不可少的，是相当有趣的，如蜻蜓、蚯蚓、毛毛虫等，孩子一边观察，一边提问，兴趣很浓。我提供的观察对象，注意形象逼真，色彩鲜明，大小适中，引导幼儿多角度多层面地进行观察，保证每个幼儿看得到，看得清。看得清才能说得正确。在观察过程中指导。我注意帮助幼儿学习正确的观察方法，即按顺序观察和抓住事物的不同特征重点观察，观察与说话相结合，在观察中积累词汇，理解词汇，如一次我抓住时机，引导幼儿观察雷雨，雷雨前天空急剧变化，乌云密布，我问幼儿乌云是什么样子的，有的孩子说：乌云像大海的波浪。有的孩子说“乌云跑得飞快。”我加以肯定说“这是乌云滚滚。”当幼儿看到闪电时，我告诉他“这叫电光闪闪。
3、”接着幼儿听到雷声惊叫起来，我抓住时机说：“这就是雷声隆隆。”一会儿下起了大雨，我问：“雨下得怎样?”幼儿说大极了，我就舀一盆水往下一倒，作比较观察，让幼儿掌握“倾盆大雨”这个词。雨后，我又带幼儿观察晴朗的天空，朗诵自编的一首儿歌：“蓝天高，白云飘，鸟儿飞，树儿摇，太阳公公咪咪笑。”这样抓住特征见景生情，幼儿不仅印象深刻，对雷雨前后气象变化的词语学得快，记得牢，而且会应用。我还在观察的基础上，引导幼儿联想，让他们与以往学的词语、生活经验联系起来，在发展想象力中发展语言。如啄木鸟的嘴是长长的，尖尖的，硬硬的，像医生用的手术刀样，给大树开刀治病。通过联想，幼儿能够生动形象地描述观察对象。 材料的类
4、型唐宋或更早之前，针对“经学”“律学”“算学”和“书学”各科目，其相应传授者称为“博士”，这与当今“博士”含义已经相去甚远。而对那些特别讲授“武事”或讲解“经籍”者，又称“讲师”。“教授”和“助教”均原为学官称谓。前者始于宋，乃“宗学”“律学”“医学”“武学”等科目的讲授者；而后者则于西晋武帝时代即已设立了，主要协助国子、博士培养生徒。“助教”在古代不仅要作入流的学问，其教书育人的职责也十分明晰。唐代国子学、太学等所设之“助教”一席，也是当朝打眼的学官。至明清两代，只设国子监（国子学）一科的“助教”，其身价不谓显赫，也称得上朝廷要员。至此，无论是“博士”“讲师”，还是“教授”“助教”，其今日教
5、师应具有的基本概念都具有了。 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(从未有生命的)。 For ind
6、ustrial 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, lubricants, and other
7、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 金属和金属合金 Metals are
8、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 intermetallic co
9、mpounds 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 metalT Pure metals are elements which come from a particular area of the periodic table. Examples of pure metals include copper in electrical wires and aluminum in cooking fo
10、il 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, and chromium;
11、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 usedT Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio. 为什么要使用金属和合金？
12、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，可用于航空航天以节约燃料。许多合金还具有高
13、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 metalsT 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 densities often c
14、ontain 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特性又要求重量轻的场合。 Fra
15、cture toughness can be described as a materials ability to avoid fracture, especially when a flaw is introduced. Metals can generally contain nicT and dents without weakening very much, and are impact resistant. A football player counts on this when he trusts that his facemask wont shatter. 断裂韧性可以描述
16、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 after a strong west w
17、ind. 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 atomic bonding of me
18、tals 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。由于电子能导热和导电，所以用金属
19、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 affect the density, s
20、trength, 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 the rusting proces
21、s, 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 the stipulation tha
22、t “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 Ceramics and Glass
23、es 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 insulators. Some cer
24、amics 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，有些是压电材料，还有些特殊陶瓷在极低温度下是超导
25、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 techniques used for glass
26、 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, ceramic powders ar
27、e 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 fiber contains three l
28、ayers: 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 protect the fiber from
29、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 travel slower, but d
30、oes 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 strikes the core/cl
31、adding 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 intensity.全内反射现象与核心玻璃的
32、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. 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 com
