机械专英第三课翻译

1、lesson 3 selecting materialswe are surrounded by materials and we rarely think about how these materials are selected我们被材料包围着，我们很少考虑这些材料是如何选定的why was your desk made of solid wood, plywood, or plastic-laminated particleboard?为什么你的桌子是实木、胶合板、或塑料层压刨花板制造的？why have so many plastics replaced steel and zinc

2、 in automobiles?在汽车里为什么有这么多的塑料代替了钢和锌？what is the controversy about using foamed polystyrene plastic to package fast food?有关使用发泡聚苯乙烯塑料包快餐的争议是什么？while you might take for granted the materials that make up your products, you can be sure that the designers did not.虽然你可能会把制造您的产品的材料认为是理所当然，但是可以确保的是设计师却没有。

3、people who design homes, cars, aircraft, clothing, furniture, and other products or systems devote a lot of attention to the selection of the materials they use.房子、汽车、飞机、服装、家具、其它产品或系统的设计者们投入了许多注意力在他所使用的材料 的选择上。material selection might make or break a company.材料的选择可能成就或也可能打破一家公司。but how do the design

4、ers make that selection to arrive at the best material?但设计者如何让该到达的材料的最佳选择呢？what selection criteria are most important?什么选择标准是最重要的？the ideal material （理想的材料）1endless and readily available source of supply无止境、随时可获得的供应来源2. cheap to refine and produce 捉取和生产廉价3 energy efficient 能源效率4. strong, stiff, an d

5、imensionally stable at all temperatures 强度，刚度、尺寸的稳定性在所有温度5. lightweight 轻量6 corrosion resistant 耐腐蚀7. no harmful effects on the environment or people 对环境或人们无害8. biodegradable可生物降解9. numerous secondary uses 众多的辅助用途obstacles to changeswitching from traditional materials such as steel and concrete to n

6、ewer materials such as plastic-based composites seems a simple, straightforward approach for the contemporary designer.从钢铁和混凝土等传统材料切换到较新的材料，如塑料复合材料的对当代设计者是似乎简单、直接的方法。the newer materials are often superior, but sometimes there are complications较新的材料往往性能更优越，但有时有并发症。often, lack of experience with new m

7、aterials causes hesitation by designers通常情况下，新材料与经验不足导致rti设计师设计的犹豫。departures from tried-and-true materials may be costly.、偏离有经验的材料可能代价高昂。it requires time before both designers and fabricators gain sufficient experienceto make products or systems.它需耍设计者和加工者获得使产品或系统成为舒适与新材料及相关的流程所需的足够经验。this problem

8、is exacerbated when human life might be in jeopardy, such aswhen designing for aircraft此问题加剧时人类的生活可能陷入困境，如设计的飞机时。consequently, new materials and processes are usually slower to enter themarketplace than might be expected因此，新的材料和工艺是进入市场上通常比预期慢these issues are all a part of engineering problem solving

9、.这些问题是工程问题需要解决的一部分materials selection is a problem-solving issue that requires an algorithm for its solutio n材料选择是为其解决方案找到-种算法的问题algorithm for materials selection 材料选择算法engineering requires clearly stated, unambiguous steps for problem solving.工程 需耍解决问题的清晰、明确的步骤。algorithms are well-defined methods f

10、or solving specific problems.算法是明确定义 的方法，解决具体问题。computer programs are written after an algorithm has been developed to lie out clearly the steps that the program is to solve.后种算法已经发展到躺着明确的程序是解决 的步骤编写计算机程序。for example, you could write a simple algorithm to calculate the strength required of a light p

11、ole to withstand the pushing forces (compression) from a light fixture例如，您可以编写一个简单的算法来计算所需的一根路灯杆承受推力(压缩)从轻的夹具的强度。a much more complex algorithm would be required to select a piston connecting rod for an internal-combustion engine.复杂得多的算法，将要求选择的内燃机活塞连杆。the first problem requires only the selection of

12、a material of suitable size/strength to hold up the light fixture, and almost any material suffice as long as it was sufficiently strong and pleasing to the user.第一个问题需要只实力支撑灯具，合 适大小的一种材料的选择和儿乎任何材料够了，只要它是足够有力和令人愉快，给用户。on the other hand, a connecting rod will undergo many types of mechanical stress,

13、ranging from compressive to tensile to torsional to gravity forces, in addition to thermal stress from the combustion chamber.另一方面，连接杆会经过许多 类型的机械应力，从压缩到拉伸到扭重力的力量，从燃烧室内的热应力。how does the designer match component requirements with available materials.selection tools设计器与可用的材料与组件要求冇什么匹配。to aid in the cre

14、ation of materials selection algorithms, databases must be available to answer questions on material suitability.为了帮助材料选择算法的创作中，数 据库必须可用回答有关材料适合的问题。a material database involves tables listing properties of material, such as tensile strength, hardness, corrosion resistance, and the ability to withsta

15、nd heat.材料数 据库涉及表格列出了屈性的材料，如拉伸强度、硬度、耐腐蚀性和热的承受能力。thousands of reference books are available with such data提供此类数据与成千上力的 参考书籍。much of these data are computerized to allow easier access.许多这些数据计算机化以 允许更容易访问。certain graphical techniques aid the designer in materials selection某些图形技术援 助在材料选择中的设计器。properties

16、 of materials 材料的性能periodicals can provide current data and performance criteria that involve structural materials:当前数据和涉及结构材料的性能标准，可提供期刊：1 strenghth (tensile, compressive, flexural, shear, and torsional)关于我们(拉伸、压 缩、弯曲、剪切、扭)2 resistance to elevated temperatures 耐高温3. fatigue resistance(repeated load

17、ing and unloading)抗疲劳(重复装载和卸载4. toughness(resistance to impact)韧性(抗冲击性能)5 wear resistance(hardness)耐磨性(硬度)6 corrosion resistance 耐腐蚀such publications present values for the performance criteria (properties) for metals, polymers, and ceramics, with updates on newer materials such as aramid fibers, zi

18、nc aluminum alloys, and super alloys.这类岀版物使用较新的材料，如芳纶纤维、锌铝合金材料和超级合金上更新现有的金属、聚合物和陶瓷 的标准(属性)的值。various periodicals have annual materials selectors that provide general information on properties for a long list of materials.各类期刊有一长串的材料属性提供一般信息的年度材料选择清单。the many tables, covering representative materials

19、, provide general data on properties for a simple comparison许多表格，覆盖代表的材料，提供一般数据属性作简单的比较。selection of specific materials requires many more detailed specifications.具体材料的选择，需要很多更详细的规格。general databases from hand books will provide much detail, but the flnalselection often requires that material manufa

20、ctures supply their own properties database for their product lines手册会提供很多详细信息，但最终的选择往往需要为他们的产品线材料制品提供他们口己的属性数据库。while databases are imperative in the initial selection steps, there are other factors that complicate materials selection虽然数据库都必须在初始选择的步骤中，但也有其它复杂材料选择的因素。materials systems 材料系统materials

21、rarely exist in isolation without interacting with other materials.材料很少存在分离而不与其它材料进行交互。rather, a combination of materials is selected to complement one another.相反，选择的材料组合相互补充。in a successful materials system, each component is compatible with the others while contributing its distinctive properties

22、to the overall characteristics of the system of which it is a part在成功的材料系统屮，每个组件同时促进了其独特的属性，其中相当一部分的总体特点是系统的与其他兼 容的。a state-of-the-art telephone is a good example先进的电话是一个好例子。the casing might be a tough abs plastic, which houses a microchip (a solid-state ceramic device) that provides memory and soun

23、d-transmission capabilities.石油套管可能强硬的abs塑料，提供了内存和声音传输功能的芯片(固态陶瓷设备)的房子copper leads join the circuitry together.铜导线将电路连接起來。there might be a battery and a ceramic light-emitting diode to show when the battery is low.电池较低时可能有一个电池和陶瓷发光二极管显示。the acid in the battery must be isolated to prevent corrosion, a

24、nd the copper leads must be insulated so that they do not short out.电池中的酸必须隔离，防止腐蚀，并必须绝缘铜的线索，以便他们不短路。each component is made of materials that meet the demands of the physical and chemical environment normally encountered when using the system每个组件rti满足系统的物理和化学坏境要求的材料组成。additional selection criteria 更

25、多选择条件existing speciheations have a lot of influence on the choice of material现有规范有很多对材料的选择的影响。these specifications or “standards” are used when redesigning an improved model of the product.重新设计产品的一种改进的模型时，将使用这些规格或”标准”。when the materials-selection algorithm results in selection of a new material, it

26、might not be covered by current speciflcations from standardization agencies 当 材料选择算法产生一种新材料的选择时，它不可能涵盖的电流规格标准化机构。the conditions of safety must be met by those involved in the manufacture or use of goods and services安全的条件必须符合的那些参与制造或使用的商品和服务。it might take considerable time for these agencies to alte

27、r their specifications to include the new material or they might not approve its use.可能需耍相当长的时间来改变他们以包括新材料的规范这些机构或他们可能不会批准其使用。availability is another concern of the designer.可用性是设计者的另一个关注的问题。will the material be easily available in the quantities and sizes required by the production demands?材料在容易获得所

28、需的数量和大小吗？in addition, will it be available in many varieties of standard shapes, such as round, oval, and square tubing此外，在多种的形状标准如圆、椭圆和平方油管屮可用吗？in the past, designers were limited to existing materials such as metal alloys, woods, or concrete在过去，设计师们限于现有的材料，如金属合金、树林或混凝土。now , it is possible to star

29、t from scratch at the synthesis stage to have materials engineers design a materials system to provide properties to meet the expected needs现在，很可能有材料工程师设计材料系统提供属性，以满足预期的需求合成阶段从零开始。processibility, the ease with which raw materials can be transformed into a flnished product, is of paramount concern绝缘性

30、、易用的原料都能变成成品，是极为关注的问题。much of the current focus is on low-energy processing低能量处理是很多的当前焦点。companies may have difficulty processing the new material on existing equipment.公司可能难以处理现有的设备上的新材料can they afford to invest in new equipment?他们可以承受投资新设备吗？today, the reverse question is usually asked: can we affo

31、rd not to use the new material and process?今天，反通常问这样的问题：我们能不使用新材料和过程吗？if we do not, the competition might make the change and run us out of business with their superior product.如果我们不这样做，竞争可能进行更改，其优越的产品可能使我们被逐出局。many new technologies are now available.现在很多的新技术是可用的quality and performance are two aspec

32、ts that achieve consumer satisfaction质量和性能是使消费者满意的两个方血。the high cost of most durable goods and the competition for customer acceptance has resulted in extended warranties最耐用物品的高成本和接受客户的竞争延长了产品的保修期。materials selection must ensure that parts will not rust, break under repeated stress, or fail to perfo

33、rm in any other way for the predicted service life of the product.材料选择必须确保零件将不生锈、反复胁迫、破坏或任何其他方式不会降低产品的预期寿命。consumer acceptance includes many factors beyond excellent quality and high performance; there are also societal aspects消费者接受包括许多因素除了超越卓越的品质和高性能，也有社会方面的问题。society as a whole as well as governme

34、ntal agency is requiring a closer look at manufactured products作为一个整体，以及政府机构的社会需要仔细看看制造的产品。any product has to be considered in terms of its total life cycle.任何产品，必须从其全生命周期的角度考虑。what are the results of the processing methods?处理方法的结果是什么？are polluting gases being released into the environment, or are t

35、oxic metals and chemicals being flushed into our rivers and streams?正在污染气体被释放到环境中，或者是有毒金属和化学品冲入河流及溪涧吗？during use, does the product safeguard our health?该产品在使用屮维护我们的健康吗？at the end of the produces useful life, how can it be disposed of safely?在该产品的使用寿命结朿时，如何可以安全处置它？municipal solid waste is hidden prod

36、uct cost that we pay in the form of higher taxes and a poorer quality of life?都市固体废物是我们以形式更高的税收和贫穷的生活质量我们付出的隐藏的产品成本吗？fast-food restaurant chains moved away from polystyrene packages because the public felt these plastic containers were more harmful to the environment than paper packaging连锁快餐餐馆不用聚苯乙烯

37、包装带，因为市民认为这些塑料容器都对环境比纸包装更有害。soft-drink manufactures are moving toward reusable plastic bottles.软性饮料制造业正在走向可重复使用的塑料瓶。design for disassembly has become a theme in much of product design by major corporations 面向拆卸设计已成为很多大公司的产品设计的一个主题。europe, which has a higher degree of ecological concern, has led the

38、way.拥有较高程度的生态关怀的欧洲走在世界前列主导这种设计。with the desire to facilitate recycling, manufacturers of small appliances and durable goods are establishing procedures to ensure that products can be broken into components for easy sorting prior to recycling随着人们希望有利于废品的回收，一些小型电器和耐用品厂家开始建立一种方法来确保他们生产的产品能 够被分解成很小的部件来便

39、于回收利用。among the procedures are reducing the variety of plastics, adding labels to plastics for easy identification of plastic type, and eliminating screws and adhesives so that parts will disassemble easily.来便于各部分零件的拆卸。one of the latest software programs is designed specifically to make products eas

40、ier to fix.又一个最新的软件是专门用来设计如何使产品更容易拆装的known as design for service, this program takes its place alongside previous software programs called design for assembly and design for manufacturability.就像我们知道的面向维修的设计，这个程序取代了别的先前的面向装备配设计和面向可制造性的设计 这两种程序。this new program helps product designers consider repair

41、issues early in the design stage这种新型的程序帮助了产品设计者在设计阶段就开始考虑维修的问题。objectives of the program include making repairs less costly and extending the functioning life of products这个程序的作用包括 了使产品获得更加低廉的维修费用和更长时间的使用寿命。environmental issues such as recycling are directly addressed by this new computer software, w

42、hich may have customers fixing products rather than tossing them out.关于环境因素，就像循环利用，这个软件能够直接帮你解决，比如可能使顾客固定产品而不是抖动in addition, this software augments product for whatever reason另外，这个软件无论如何都增涨了产品。more often than not, cost is the primary selecting criterion that will determine the final choice of material.材料成本的主要选择标准通常将决定材料的最后决世。in other words, if several materials have the specified physical, mechnical, and ch