機(jī)械專業(yè)英語整理

1、UNIT1 Types of Materials 材料的類型 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. 材料可以按多種方法分類?？茖W(xué)家常根據(jù)狀態(tài)將材料分為：固體、液體或氣體。他們也把材料分為有機(jī)材料(曾經(jīng)有生命的)和無機(jī)材料(

2、從未有生命的)。 For industrial purposes, materials are divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and become parts of products. 就工業(yè)效用而言，材料被分為工程材料和非工程材料。那些用于加工制造并成為產(chǎn)品組成部分的就是工程材料。Nonengineering materials are the chemicals, fuels, lubric

3、ants, and other materials used in the manufacturing process, which do not become part of the product.非工程材料則是化學(xué)品、燃料、潤滑劑以及其它用于加工制造過程但不成為產(chǎn)品組成部分的材料。 Engineering materials may be further subdivided into: Metal Ceramics Composite Polymers, etc. 工程材料還能進(jìn)一步細(xì)分為：金屬材料陶瓷材料復(fù)合材料 聚合材料，等等。 Metals and Metal Alloys 金屬

4、和金屬合金 Metals are elements that generally have good electrical and thermal conductivity. Many metals have high strength, high stiffness, and have good ductility. 金屬就是通常具有良好導(dǎo)電性和導(dǎo)熱性的元素。許多金屬具有高強(qiáng)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.某些金屬能被磁化，例如鐵、鈷和鎳。在極低的溫度下，某些金屬和金屬化合物能轉(zhuǎn)變成超導(dǎo)體。 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 alumi

6、num in cooking foil and beverage cans. 合金與純金屬的區(qū)別是什么？純金屬是在元素周期表中占據(jù)特定位置的元素。例如電線中的銅和制造烹飪箔及飲料罐的鋁。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, nicke

7、l, and chromium; and gold jewelry which usually contains an alloy of gold and nickel.合金包含不止一種金屬元素。合金的性質(zhì)能通過改變其中存在的元素而改變。金屬合金的例子有：不銹鋼是一種鐵、鎳、鉻的合金，以及金飾品通常含有金鎳合金。 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 ra

8、tio. 為什么要使用金屬和合金？許多金屬和合金具有高密度，因此被用在需要較高質(zhì)量體積比的場合。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.某些金屬合金，例如鋁基合金，其密度低，可用于航

9、空航天以節(jié)約燃料。許多合金還具有高斷裂韌性，這意味著它們能經(jīng)得起沖擊并且是耐用的。 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. 金屬有哪些重要特性？ 密度定義為材料的質(zhì)量與其體積之比。大多數(shù)金屬密度相對較高，尤其是和聚合物相比較而言。Materials with high

10、densities 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.高密度材料通常由較大原子序數(shù)原子構(gòu)成，例如金和鉛。然而，諸如鋁和鎂之類的一些金屬則具有低密度，并被用于既需要金

11、屬特性又要求重量輕的場合。 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. 斷裂韌性可以描述為材料防止斷裂特別是出現(xiàn)缺陷時(shí)不斷裂的能力。金屬一般能在有缺口和凹痕的情況下不顯著削弱，并且能抵抗沖擊。橄欖球運(yùn)動(dòng)員據(jù)此相信他的面罩不會裂成碎片。 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 aft

13、er a strong west wind. 塑性變形就是在斷裂前彎曲或變形的能力。作為工程師，設(shè)計(jì)時(shí)通常要使材料在正常條件下不變形。沒有人愿意一陣強(qiáng)烈的西風(fēng)過后自己的汽車向東傾斜。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，有時(shí)我們也能利用塑性變形。汽車上壓皺的區(qū)域在它們斷裂前通過經(jīng)歷塑性變形來吸收能量。 The at

14、omic 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. 金屬的原子連結(jié)對它們的特性也有影響。在金屬內(nèi)部，原子的外層階電子由所有原子共享并能到處自由移

15、動(dòng)。由于電子能導(dǎo)熱和導(dǎo)電，所以用金屬可以制造好的烹飪鍋和電線。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?yàn)檫@些階電子吸收到達(dá)金屬的光子，所以透過金屬不可能看得見。沒有光子能通過金屬。 Alloys are compounds consisting of more than one metal. Adding other metals can aff

16、ect the density, strength, fracture toughness, plastic deformation, electrical conductivity and environmental degradation. 合金是由一種以上金屬組成的混合物。加一些其它金屬能影響密度、強(qiáng)度、斷裂韌性、塑性變形、導(dǎo)電性以及環(huán)境侵蝕。For example, adding a small amount of iron to aluminum will make it stronger. Also, adding some chromium to steel will slow

17、the rusting process, but will make it more brittle.例如，往鋁里加少量鐵可使其更強(qiáng)。同樣，在鋼里加一些鉻能減緩它的生銹過程，但也將使它更脆。 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

18、the stipulation that “ceramic” must also be crystalline. 陶瓷通常被概括地定義為無機(jī)的非金屬材料。照此定義，陶瓷材料也應(yīng)包括玻璃；然而許多材料科學(xué)家添加了“陶瓷”必須同時(shí)是晶體物組成的約定。 A glass is an inorganic nonmetallic material that does not have a crystalline structure. Such materials are said to be amorphous. 玻璃是沒有晶體狀結(jié)構(gòu)的無機(jī)非金屬材料。這種材料被稱為非結(jié)晶質(zhì)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 高熔點(diǎn)、低密度、高強(qiáng)度、高剛度、高硬度、高耐磨性和抗腐蝕性是陶瓷和玻璃的一些有用特性。Many ceramics are good electrical and thermal i

20、nsulators. 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.許多陶瓷都是電和熱的良絕緣體。某些陶瓷還具有一些特殊性能：有些是磁性材料，有些是壓電

21、材料，還有些特殊陶瓷在極低溫度下是超導(dǎo)體。陶瓷和玻璃都有一個(gè)主要的缺點(diǎn)：它們?nèi)菀灼扑椤?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?yàn)榇蠖鄶?shù)陶瓷在從液態(tài)冷卻時(shí)將會完全破碎(即形成粉末)。Hence, all the simple and efficient manufacturing techni

22、ques 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，所有用于玻璃生產(chǎn)的簡單有效的諸如澆鑄和吹制這些涉及熔化的技術(shù)都不能用于由晶體物組成的陶瓷的生產(chǎn)。作為替代，一般采用“燒結(jié)”或“焙燒”工藝。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.在燒結(jié)過程中，陶瓷粉末先擠壓成型然后加熱到略低于熔點(diǎn)溫度。在這樣的溫度下，粉末內(nèi)部起反應(yīng)去除孔隙并得到十分致密的物品。 An optical fib

24、er 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 prot

25、ect the fiber from damage. 光導(dǎo)纖維有三層：核心由高折射指數(shù)高純光傳輸玻璃制成，中間層為低折射指數(shù)玻璃，是保護(hù)核心玻璃表面不被擦傷和完整性不被破壞的所謂覆層，外層是聚合物護(hù)套，用于保護(hù)光導(dǎo)纖維不受損。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 t

26、ravel slower, but does not absorb the light. 為了使核心玻璃有比覆層大的折射指數(shù)，在其中摻入微小的、可控?cái)?shù)量的能減緩光速而不會吸收光線的雜質(zhì)或攙雜劑。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

27、strikes the core/cladding interface at an angle greater than the critical angle. 由于核心玻璃的折射指數(shù)比覆層大，只要在全內(nèi)反射過程中光線照射核心/覆層分界面的角度比臨界角大，在核心玻璃中傳送的光線將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 int

28、ensity.全內(nèi)反射現(xiàn)象與核心玻璃的高純度一樣，使光線幾乎無強(qiáng)度損耗傳遞長距離成為可能。 Composites 復(fù)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、 復(fù)合材料由兩種或更多材料構(gòu)成。例子有聚合物/陶瓷和金屬/陶瓷復(fù)合材料。之所以使用復(fù)合材料是因?yàn)槠淙嫘阅軆?yōu)于組成部分單獨(dú)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/陶瓷復(fù)合材料具有比聚合

30、物成分更大的模量，但又不像陶瓷那樣易碎。 復(fù)合材料有兩種：纖維加強(qiáng)型復(fù)合材料和微粒加強(qiáng)型復(fù)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. 纖維加強(qiáng)型復(fù)合材料 加強(qiáng)纖維可以是金屬、陶瓷、玻璃或是已變成石墨的被

31、稱為碳纖維的聚合物。纖維能加強(qiáng)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.沿著纖維長度有很強(qiáng)結(jié)合力的共價(jià)結(jié)合在這個(gè)方向上給予復(fù)合材料很高的模量，因?yàn)橐獡p壞或拉伸纖維就必須破壞或移除這種結(jié)合。 Fibers are difficult to process into composite

32、s, making fiber-reinforced composites relatively expensive. 把纖維放入復(fù)合材料較困難，這使得制造纖維加強(qiáng)型復(fù)合材料相對昂貴。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 polym

33、er matrix. 纖維加強(qiáng)型復(fù)合材料用于某些最先進(jìn)也是最昂貴的運(yùn)動(dòng)設(shè)備，例如計(jì)時(shí)賽競賽用自行車骨架就是用含碳纖維的熱固塑料基材制成的。Body parts of race cars and some automobiles are composites made of glass fibers (or fiberglass) in a thermoset matrix. 競賽用汽車和某些機(jī)動(dòng)車的車體部件是由含玻璃纖維(或玻璃絲)的熱固塑料基材制成的。 Fibers have a very high modulus along their axis, but have a low modul

34、us perpendicular to their axis. Fiber composite manufacturers often rotate layers of fibers to avoid directional variations in the modulus. 纖維在沿著其軸向有很高的模量，但垂直于其軸向的模量卻較低。纖維復(fù)合材料的制造者往往旋轉(zhuǎn)纖維層以防模量產(chǎn)生方向變化。Particle-reinforced composites Particles used for reinforcing include ceramics and glasses such as smal

35、l mineral particles, metal particles such as aluminum, and amorphous materials, including polymers and carbon black.微粒加強(qiáng)型復(fù)合材料 用于加強(qiáng)的微粒包含了陶瓷和玻璃之類的礦物微粒，鋁之類的金屬微粒以及包括聚合物和碳黑的非結(jié)晶質(zhì)微粒。 Particles are used to increase the modulus of the matrix, to decrease the permeability of the matrix, to decrease the ductil

36、ity 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、減少基材的滲透性和延展性。微粒加強(qiáng)型復(fù)合材料的一個(gè)例子是機(jī)動(dòng)車胎，它就是在聚異丁烯人造橡膠聚合物基材中加入了碳黑微粒。 Polymers 聚合材料 A polymer has a repeating structure, usuall

37、y based on a carbon backbone. The repeating structure results in large chainlike molecules. Polymers are useful because they are lightweight, corrosion resistant, easy to process at low temperatures and generally inexpensive. 聚合物具有一般是基于碳鏈的重復(fù)結(jié)構(gòu)。這種重復(fù)結(jié)構(gòu)產(chǎn)生鏈狀大分子。由于重量輕、耐腐蝕、容易在較低溫度下加工并且通常較便宜，聚合物是很有用的。 Some

38、 important characteristics of polymers include their size (or molecular weight), softening and melting points, crystallinity, and structure. The mechanical properties of polymers generally include low strength and high toughness. Their strength is often improved using reinforced composite structures

39、. 聚合材料具有一些重要特性，包括尺寸(或分子量)、軟化及熔化點(diǎn)、結(jié)晶度和結(jié)構(gòu)。聚合材料的機(jī)械性能一般表現(xiàn)為低強(qiáng)度和高韌性。它們的強(qiáng)度通?？刹捎眉訌?qiáng)復(fù)合結(jié)構(gòu)來改善。Important Characteristics of Polymers Size. Single polymer molecules typically have molecular weights between 10,000 and 1,000,000g/molthat can be more than 2,000 repeating units depending on the polymer structure! 聚合材

40、料的重要特性 尺寸：單個(gè)聚合物分子一般分子量為10,000到1,000,000g/mol之間，具體取決于聚合物的結(jié)構(gòu)這可以比2,000個(gè)重復(fù)單元還多。The mechanical properties of a polymer are significantly affected by the molecular weight, with better engineering properties at higher molecular weights.聚合物的分子量極大地影響其機(jī)械性能，分子量越大，工程性能也越好。 Thermal transitions. The softening poi

41、nt (glass transition temperature) and the melting point of a polymer will determine which it will be suitable for applications. These temperatures usually determine the upper limit for which a polymer can be used. 熱轉(zhuǎn)換性：聚合物的軟化點(diǎn)(玻璃狀轉(zhuǎn)化溫度)和熔化點(diǎn)決定了它是否適合應(yīng)用。這些溫度通常決定聚合物能否使用的上限。For example, many industrially

42、important polymers have glass transition temperatures near the boiling point of water (100, 212), and they are most useful for room temperature applications. Some specially engineered polymers can withstand temperatures as high as 300(572).例如，許多工業(yè)上的重要聚合物其玻璃狀轉(zhuǎn)化溫度接近水的沸點(diǎn)(100, 212)，它們被廣泛用于室溫下。而某些特別制造的聚合

43、物能經(jīng)受住高達(dá)300(572)的溫度。 Crystallinity. Polymers can be crystalline or amorphous, but they usually have a combination of crystalline and amorphous structures (semi-crystalline). 結(jié)晶度：聚合物可以是晶體狀的或非結(jié)晶質(zhì)的，但它們通常是晶體狀和非結(jié)晶質(zhì)結(jié)構(gòu)的結(jié)合物(半晶體)。 Interchain interactions. The polymer chains can be free to slide past one anoth

44、er (thermo-plastic) or they can be connected to each other with crosslinks (thermoset or elastomer). Thermo-plastics can be reformed and recycled, while thermosets and elastomers are not reworkable. 原子鏈間的相互作用：聚合物的原子鏈可以自由地彼此滑動(dòng)(熱可塑性)或通過交鍵互相連接(熱固性或彈性)。熱可塑性材料可以重新形成和循環(huán)使用，而熱固性與彈性材料則是不能再使用的。 Intrachain str

45、ucture. The chemical structure of the chains also has a tremendous effect on the properties. Depending on the structure the polymer may be hydrophilic or hydrophobic (likes or hates water), stiff or flexible, crystalline or amorphous, reactive or unreactive. 鏈內(nèi)結(jié)構(gòu)：原子鏈的化學(xué)結(jié)構(gòu)對性能也有很大影響。根據(jù)各自的結(jié)構(gòu)不同，聚合物可以是親水

46、的或憎水的(喜歡或討厭水)、硬的或軟的、晶體狀的或非結(jié)晶質(zhì)的、易起反應(yīng)的或不易起反應(yīng)的。Unit7 The importance of machining processes can be emphasised by the fact that every product we use in our daily life has undergone this process either directly or indirectly. (1) In USA, more than $100 billions are spent annually on machining and related

47、operations. 機(jī)加工過程的重要性可通過日常生活使用的每件產(chǎn)品都直接或間接經(jīng)歷這一過程的事實(shí)來強(qiáng)調(diào)。 (1)在美國，每年花在機(jī)加工及其相關(guān)作業(yè)上的費(fèi)用都多于千億美元。 (2) A large majority (above 80%) of all the machine tools used in the manufacturing industry have undergone metal cutting. (3) An estimate showed that about 10 to 15% of all the metal produced in USA was converte

48、d into chips. (2) 用于制造業(yè)的全部機(jī)床中的大多數(shù)(多于80%)都經(jīng)歷過金屬切削。 (3) 有估計(jì)顯示美國生產(chǎn)的所有金屬中約10到15%轉(zhuǎn)變成了切屑。 These facts show the importance of metal cutting in general manufacturing. It is therefore important to understand the metal cutting process in order to make the best use of it. 這些事實(shí)說明了金屬切削在常規(guī)制造中的重要性。因此了解金屬切削過程以充分利用它

49、是重要的。A number of attempts have been made in understanding the metal cutting process and using this knowledge to help improve manufacturing operations which involved metal cutting.在了解金屬切削過程并運(yùn)用這些知識幫助改善與金屬切削有關(guān)的制造作業(yè)方面已經(jīng)做了許多努力。 A typical cutting tool in simplified form is shown in Fig.7.1. The important

50、features to be observed are follows. 典型切削刀具的簡化形式如圖7.1所示。要注意的重要特征如下。 1. Rake angle. It is the angle between the face of the tool called the rake face and the normal to the machining direction. Higher the rake angle, better is the cutting and less are the cutting forces, increasing the rake angle redu

51、ces the metal backup available at the tool rake face. 1.前角：它是被稱為前傾面的刀具面與垂直機(jī)加工方向的夾角。前角越大，則切削越好且切削力越小，增加前角可以減少刀具前傾面上產(chǎn)生的金屬阻塞。This reduces the strength of the tool tip as well as the heat dissipation through the tool. Thus, there is a maximum limit to the rake angle and this is generally of the order of

52、 15°for high speed steel tools cutting mild steel. It is possible to have rake angles at zero or negative.但這會和減少通過刀具散發(fā)的熱量一樣減少刀尖強(qiáng)度。因此前角有一最大限制，用高速鋼刀具切削低碳鋼通常為15°。前角取零度或負(fù)值也是可能的。 2. Clearance angle. This is the angle between the machined surface and the underside of the tool called the flank fa

53、ce. The clearance angle is provided such that the tool will not rub the machined surface thus spoiling the surface and increasing the cutting forces. A very large clearance angle reduces the strength of the tool tip, and hence normally an angle of the order of 56°is used. 2. 后角：這是機(jī)加工面與被稱為后側(cè)面的刀具

54、底面夾角。后角使刀具不產(chǎn)生會損壞機(jī)加工面的摩擦和增加切削力。很大的后角會削弱刀尖的強(qiáng)度，因此一般采用56°的后角。 The conditions which have an important influence on metal cutting are work material, cutting tool material, cutting tool geometry, cutting speed, feed rate, depth of cut and cutting fluid used. 對金屬切削有重要影響的條件有工件材料、刀具材料、刀具幾何形狀、切削速度、進(jìn)給率、切削深

55、度和所用的切削液。 The cutting speed, v, is the speed with which the cutting tool moves through the work material. This is generally expressed in metres per second (ms-1). 切削速度v指切削刀具經(jīng)過工件材料的移動(dòng)速度。通常用米每秒 (ms-1)表示。 Feed rate, f, may be defined as the small relative movement per cycle (per revolution or per strok

56、e) of the cutting tool in a direction usually normal to the cutting speed direction. Depth of cut, d, is the normal distance between the unmachined surface and the machined surface. 進(jìn)給率f可定義為每循環(huán)(每轉(zhuǎn)或每行程)切削刀具在通常為垂直于切削速度方向的次要相對運(yùn)動(dòng)。 切削深度d是未加工面與已加工面之間的垂直距離。 Chip Formation 切屑的形成 Metal cutting process is a very complex process. Fig.7.2 shows the basic material removal operation schematically. 金屬切削過程是一個(gè)很復(fù)雜的過程。圖7.2用圖的形式顯示了基本材料去除作業(yè)。The metal in front of the tool rake face gets immediately compressed, first elastically and then plastically. This zone is tra