機械設計制造及其自動化專業(yè)英語翻譯超級大全

1、Unit 1 Metals金屬The use of metals has always been a key factor in the development of the social systems of man. Of the roughly 100 basic elements of which all matter is composed, about half are classified as metals. The distinction between a metal and a nonmetal is not always clear-cut. The most basi

2、c definition centers around以為中心 the type of bonding existing between the atoms of the element, and around the characteristics of certain of the electrons某種電子 associated with these atoms. In a more practical way, however, a metal can be defined as an element which has a particular package of properti

3、es.Metals are crystallineadj.晶體的 when in the solid state and, with few exceptions極少例外 (e.g. mercury), are solid at ambient周圍環(huán)境的 temperatures. They are good conductors of heat and electricity and are opaque不透明的 to light. They usually have a comparatively high density. Many metals are ductile柔軟的；易延展的-

4、that is, their shape can be changed permanently永久地，長期不變地 by the application of a force without breaking. The forces required to cause this deformation and those required to break or fracture a metal are comparatively high, although, the fracture forces is not nearly =far from,much less than as high

5、as would be expected from simple consideration of the forces required to tear apart the atoms of the metal.One of the more significant of these characteristics from our point of view is that of crystallinitycrystallinity ,kristlinti. A crystalline solid is one in which the constituent atoms are loca

6、ted in a regular three-dimensional array as if they were located at the corners of the squares of a three-dimensional chessboardn. 棋盤. The spacing of the atoms in the array is of the same order as the size of the atoms, the actual spacing being a characteristic of the particular metal. The direction

7、s of the axes of the array define the orientation of the crystal in space. The metals commonly used in engineering practice are composed of a large number of such crystals, called grains晶粒. In the most general case一般情況下, the crystals of the various grains are randomly oriented in space. The grains a

8、re everywhere in intimate contact with one another and joined together on an atomic scale. The region at which they join is known as a grain boundary.An absolutely pure metal (i.e.也就是 one composed of only one type of atom) has never been produced. Engineers would not be particularly interested in su

9、ch a metal even if it were to be produced, because it would be soft and weak. The metals used commercially inevitably不可避免地 contain small amounts of one or more foreign elements, either metallicmetallic mitlik, me-adj. 金屬的，含金屬的 or nonmetallic. These foreign elements may be detrimental有害的, they may be

10、 beneficial, or they may have no influence at all on a particular property. If disadvantageous, the foreign elements tend to be known as impurities雜質. If advantageous, they tend to be known as alloying elements合金元素. Alloying elements are commonly added deliberately故意地，蓄意地 in substantialadj. 大量的；實質的；

11、內容充實的substantial evidence:實（質）體證據(jù)|實質性證據(jù)|實質證據(jù)substantial order:大宗訂單|大訂單 amounts in engineering materials. The result is known as an alloy.The distinction between the descriptors “metal” and “alloy” is not clear-cut. The term “metal” may be used to encompass both a commercially pure metal and its allo

12、ys. Perhaps it can be said that the more deliberately an alloying addition has been made and the larger the amount of the addition, the more likely it is that the product will specifically be called an alloy. In any event無論如何，不管怎樣, the chemical composition of a metal or an alloy must be known and co

13、ntrolled within certain limits if consistent一致的 performance is to be achieved in service. Thus chemical composition has to be taken into account when developing an understanding of the factors which determine the properties of metals and their alloys.Of the 50 or so metallic elements, only a few are

14、 produced and used in large quantities in engineering practice. The most important by far is iron鐵, on which are based the ubiquitous普遍的，無處不在的 steels and cast irons (basically alloys of iron and carbon). They account for about 98% by weight of all metals produced. Next in importance for structural u

15、ses (that is, for structures that are expected to carry loads) are aluminum鋁, copper, nickel, and titanium taiteinim, ti-n. 化鈦（金屬元素）. Aluminum accounts for about 0.8% by weight of all metals produced, and copper about 0.7%, leaving only 0.5% for all other metals. As might be expected, the remainders

16、 are all used in rather相當 special applications. For example, nickel alloys are used principally主要地 in corrosion-and heat-resistant applications, while titanium is used extensively廣泛地 in the aerospace industry because its alloys have good combinations of high strength and low density. Both nickel and

17、 titanium are used in high-cost, high-quality applications, and, indeed, it is their high cost that tends to restrict their application.We cannot discuss these more esotericadj. 秘傳的；限于圈內人的；難懂的Esoteric Buddhism:密宗|密宗，特別是指西藏的喇嘛教。 properties here. Suffice it to say1. Suffice it to say that you love me.

18、只要說你愛我就夠了。2. Suffice it to say that the gun was his.只需說這槍是他的就夠了。 that a whole complex of properties in addition to structural strength is required of an alloy before it will be accepted into, and survive in, engineering practice. It may, for example, have to be strong and yet have reasonable corrosi

19、on resistance; it may have to be able to be fabricated by a particular process such as deep drawing, machining, or welding; it may have to be readily容易地 recyclable; and its cost and availability may be of critical importance.在人類社會的發(fā)展中，金屬的應用起著關鍵性的作用。構成物質的大約100種基本元素中，大約有一半為金屬。金屬和非金屬之間的區(qū)別不是特別明顯。最基本的定義集

20、中在元素原子間存在的連接形式和與這些原子相關聯(lián)的電子的某些特性。然而，在實際應用中，可以將具有某些特性集合金屬定義為某種元素。除了少數(shù)例外金屬在常溫下是固態(tài)的。它們是熱和電的良導體，不透光。它們往往具有較高的密度。許多金屬具有延展性，也就是說，在不被破壞的情況下它們的形狀在外力的作用下可以發(fā)生變化。引起永久變形所需的力和最終使金屬斷裂所需的力相當大，盡管發(fā)生斷裂所需的力遠沒有像所預期的撕開金屬原子所需的力那么大。從我們的觀點來看，在所有的特性中結晶性是最重要的。結晶體是這樣一種結構，組成它的原子定位在規(guī)則的三維排列中，仿佛位于三維棋盤的方格的角上。原子間距隨著原子大小呈規(guī)律性變化，原子間距是金

21、屬的一種特性。三維排列的軸線決定了晶體在空間中的方向。在工程實踐中應用的金屬由大量的晶體組成，這些晶體稱之為晶粒。在大多數(shù)情況下，晶粒在空間中是自由排列的。在原子范圍內，晶粒之間相互接觸緊密結合。晶粒之間連接區(qū)域被稱為晶界。絕對純凈的金屬從來也沒有被生產出來過。即使絕對純凈的金屬可以生產出來，工程師們對它們也并不會特別感興趣，因為它們很柔軟、脆弱。實際應用中的金屬往往都包含著一定數(shù)量的一種或多種外來金屬或非金屬元素，這些外來元素可能是有害的也可能是有益的或者它們對某種特定的屬性沒有影響。如果是有害的，這些外來元素被認為是雜質。如果是有益的，它們被認為是合金元素。在工程材料中往往被特意地加入一定

22、數(shù)量的合金元素。得到的物質被叫做合金。金屬和合金區(qū)別不大。金屬這個詞可以包括工業(yè)用純金屬和它的合金。也許可以這樣說，合金元素越故意的被添加，被添加的合金元素的量越大，那么生產出來的產品越傾向于被稱之為合金。不管怎樣，如果想使一種金屬或合金在使用中表現(xiàn)出穩(wěn)定一致的特性，在其中添加何種化學成分，它的量多大都應該在控制范圍之內。因此，當想了解決定金屬和合金性質的因素時，應充分考慮它們的化學組成。在50種左右的金屬元素里，工程實踐中只有少數(shù)金屬被大量生產和使用。到目前為止最重要的是鐵，以它為基礎構成了處處可見的鋼和鑄鐵。（主要由鐵和碳構成的合金）它們的重量占所有生產出來的金屬重量的98%。在結構應用（

23、也就是說，可以承受載荷的結構）中居于其次位置的是鋁、銅、鎳和鈦。在所有的金屬產量中，鋁占0.8，銅占0.7，剩下的占0.5。剩下的金屬用于相對特殊的用途。例如，鎳合金主要用于抗磨損和耐高溫的用途，由于鈦合金具有高強度和低密度的綜合特性，鈦被廣泛應用于航空工業(yè)中。鎳合鈦有高成本和高質量的使用特性，事實上，它們高的成本限制了它們的應用。我們不能在這里討論這些深奧的特性。在合金材料被采用和應用于工程實際之前，掌握其結構強度和它的綜合性質就夠了。舉例來說，它可以強度很高，并且有好的耐磨性；它可以被例如拉伸加工，機械加工，或焊接等特殊工藝來加工出來；它可以被循環(huán)利用；它的成本和實用性是首要的。Unit

24、2 Selection of Construction Materials工程材料的選擇There is not a great difference between “this” steel and “that” steel; all are very similar in mechanical properties. Selection must be made on factors such as hardenability ,h:dnbiltin. 可硬化性；淬硬性, price, and availability ,veilbilti是產品在被調用時能夠運行（即未處于失效或修復狀態(tài)）

25、的概率。此量度考慮了產品的可靠性（多久會失效）和可用性（多久能被修復）。 , and not with the idea that “this” steel can do something no other can do because it contains 2 percent instead of 1 percent of a certain alloying element, or because it has a mysterious mistirisadj. 神秘的；不可思議的；難解的(神秘的，不可思議的) name. A tremendousadj. 極大的，巨大的；驚人的 ra

26、nge of properties is available in any steel after heat treatment; this is particularly true of alloy steels.在鋼之間沒有太大的區(qū)別；所有的鋼在機械性能方面都是近似的。它們的選取標準是諸如脆硬性，價格，和可用性等。不僅僅是因為這種鋼含有2的合金元素另一種鋼含有1而使前者具有了后者沒有的某些能力，或者是某種鋼具有神奇的名字。經(jīng)過熱處理后，任何一種鋼都具有大范圍的特性；這種性質同樣在合金鋼中存在。Considerations in fabrication(制造)The properties o

27、f the final part (hardness, strength, and machinability m,i:nbiltin. 切削性；機械加工性), rather than properties required by forging, govern the selection of material. The properties required for forging have very little relation to the final properties of the material; therefore, not much can be done無論做什么都是

28、 白費力，都改變不了既定的現(xiàn) 實 to improve its forgeability. Higher-carbon steel is difficult to forge. Large grain size is best if subsequent heat treatment will refine the grain size.關于加工的考慮最后零件的特性（硬度、強度和可加工性）而不是鍛造特性決定了材料的選擇?？慑懶耘c材料的最后特性聯(lián)系不大；因此，提高金屬的可鍛造性價值不大。高碳鋼很難鍛造。如果在隨后的熱處理過程進行細化，大尺寸晶粒是最好的。Low-carbon, nickel-ch

29、romium(鉻) steels are just about幾乎，差不多j as plastic at high temperature under a single 520-ftlb(1 ftlb=1.35582J) blowat a single blow= at one blowat a single blow:一下子|一舉|一擊 as plain steels of similar carbon content. Nickel decreases forgeability of medium-carbon steels, but has little effect on low-ca

30、rbon steels. Chromium seems to harden steel at forging temperatures, but vanadium(釩) has no discernible(可辨別的) effect; neither has the method of manufacture any effect on high-carbon steel.在高溫下低碳，鎳鉻合金鋼在受到520-ftlb的沖擊下表現(xiàn)出與相同碳含量普通鋼幾乎同樣的塑性。鎳減少了中碳鋼的可鍛性，但對低碳鋼影響不大。鉻在鍛造溫度下時使鋼硬化，但釩沒有明顯的效果；兩種加工方法對高碳鋼沒有影響。Forma

31、bilityThe cold-formability of steel is a function(功能) of its tensile strength combined with ductility. The tensile strength and yield point must not be high or too much work will be required in bending（彎曲）; likewise（同樣地）, the steel must have sufficient（充足的） ductility to flow to the required shape wi

32、thout cracking. The force required depends on the yield point, because deformation starts in the plastic range above the yield point of steel. Work-hardening also occurs here, progressively（日益增多地） stiffening（使變硬） the metal and causing difficulty, particularly（獨特的，顯著的） in the low-carbon steels.成形鋼的冷成

33、形是它的拉伸強度和延展性相結合的結果。拉伸強度和屈服點不能太高否則在發(fā)生彎曲時需要做很多工作；與之相類似，鋼應該有高延展性，使其在沒有斷裂的情況下成形。加工力的大小取決于屈服點，因為鋼在屈服點之上才開始變形。與此同時，加工硬化也同時發(fā)生，金屬變得越來越硬，增加加工難度，尤其在低碳鋼中容易發(fā)生。It is quite interesting in this connection（關于這一點，就此而論） to discover that deep draws can sometimes be made in one rapid operation that could not possibly b

34、e done leisurely（緩慢地，從容不迫地） in two or three. If a draw is half made and then stopped, it may be necessary to anneal（退火） before proceeding, that is（換句話說）, if the piece is given time to work-harden. This may not be a scientific statement, but it is actually what seems to happen.在這方面，相當有趣的是你將發(fā)現(xiàn)有時可通過一次快

35、速加載完成大拉伸，但以緩慢的方式兩三次加載卻不能實現(xiàn)。如果拉伸進行了一半就停止了，那么在再加工之前應先退火，也就是說工件是否有時間進行加工硬化。這不是一種科學的敘述方法，但確實是發(fā)生了。Internal stressesCold forming is done above the yield point in the work-hardening range, so internal stresses can be built up easily. Evidence of this is the springback（回彈） as the work leaves the forming ope

36、ration and the warpage（翹曲，扭曲） in any（任何一種） subsequent heat treatment. Even a simple washer might, by virtue of由于，憑借(依靠) the internal stresses resulting from punching（沖壓） and then flattening（整平）, warp（彎曲） severely（嚴格地，激烈地） during heat treating. （virtue n.德行, 美德, 貞操, 優(yōu)點, 功效, 效力, 英勇 believed in the vir

37、tue of prayer.相信祈禱的力量內應力在高于屈服點的加工硬化區(qū)進行冷加工很容易產生內應力。例如工件停止成型加工后會發(fā)生回彈，在隨后的熱處理后，工件會發(fā)生翹曲。即使是一個簡單的墊圈，由于打孔和隨后的平整加工中產生內應力，也會在熱處理中呈現(xiàn)嚴重的翹曲。When doubt exists as to（關于） whether internal stresses will cause warpage, a piece can be checked by heating it to about 1100 and then letting it cool. If there are interna

38、l stresses, the piece is likely to（可能） deform. Pieces that will warp severely while being heated have been seen, yet （然而）the heat-treater熱處理爐 was expected to有望做某事；被期待做某事 put them throughput through 完成 and bring them out better than they were in the first place.當是否內應力會引起翹曲的懷疑存在時，可以通過將工件加工至1100然后進行冷卻來

39、驗證。如果存在內應力，工件會發(fā)生變形。經(jīng)過熱處理的工件像我們看到的那樣會發(fā)生嚴重的翹曲，但是我們仍然希望工件被扔到熱處理爐中被處理，這樣好過它存在內應力的狀態(tài)。WeldingThe maximum carbon content of plain carbon steel safe for welding without preheating or subsequent heat treatment is 0.3%. higher-carbon steel is welded every day, but only with proper preheating. There are two im

40、portant factors: the amount of heats that is put in ; the rate at which it is removed.焊接不需要預熱或之后進行熱處理就能安全焊接的最高碳含量為0.3。高碳鋼通過合適的預熱通常也可焊接。有兩點值得注意：吸收熱量的多少；移除速度。Welding at a slower rate puts in more heat and heats a large volume of metal, so the cooling rate due to loss of heat to the base metal is decre

41、ased(減少). A preheat will do the same thing. For example, sae4150 steel, preheated to 600 or 800, can be welded readily（容易地）. When the flame or arc is taken away from the weld, the cooling rate is not so great, owing to the higher temperature of the surrounding metal and slower cooling results. Even

42、the most rapid air-hardening（風硬鋼） steels are weldable if preheated and welded at a slow rate.低速焊接帶來了更多的熱量，這對金屬的大量體積進行了加熱，所以冷卻速度降低。預熱可以取得與之相當?shù)男Ч?。例如?被預熱至 或 時可以很好的焊接。由于周圍金屬的較高溫度，當焊接弧移開焊接點后，冷卻速度不會太快，產生了低速冷卻的結果。即使是冷作硬化速度最快的金屬也可以通過預熱和慢速焊接達到良好的焊接效果。MachinabilityMachinability（機械加工性能） means several things.

43、To production men it generally means being able to remove metal at the fastest rate, leave the best possible finish, and obtain the longest possible tool life. Machinability applies to（應用于） the tool-work（工具，零件） combination.可加工性可加工性意味著幾件事情。對于加工者來說，它意味著可以快速的移除金屬，取得最好的加工效果，得到最長的刀具壽命。可加工性是刀具和零件的結合。It is

44、 not determined by hardness（硬度） alone, but by the toughness（韌性）, microstructure, chemical composition（成分）, and tendency（傾向） of a metal to harden under cold work. In the misleading expression “too hard to machine”, the word “hard” is usually meant to be synonymous（同義的） with “difficult”. Many times a

45、material is actually too soft to machine readily. Softness and toughness may cause the metal to tear（撕裂） and flow ahead of the cutting tool rather than cut cleanly. Metal that are inherently（天性地，固有地） soft and tough are sometimes alloyed to improve their machinability at some sacrifice skrifais n. 犧牲

46、；祭品；供奉All gains are made at some sacrifice.Most people might choose to divert the course of the train, and sacrifice only one child.（犧牲） in ductility. Examples are use of lead（鉛） in brass（黃銅） and of sulfur slf（硫磺） in steel.加工性不僅僅只由硬度決定，它還由韌性，微觀結構，化學成分和在冷加工下金屬所呈現(xiàn)的硬化特性所決定。在容易混淆的表示“難加工”中，“hard”與“diffic

47、ult”同義。許多時候，因為材料過軟而難于穩(wěn)定加工。材料柔軟性和韌性能夠產生金屬撕裂，使金屬在完成切削前流動至刀具前端。柔軟的金屬往往會被加入合金從而犧牲它的延展性來提高加工性能。如黃銅中加入鉛鋼中加入硫磺。Machinability is a term used to indicate the relative（比較的） ease（不費力） with which a material can be machined by sharp cutting tools in operations such as turning（車）, drilling（鉆）, milling（銑）, broachi

48、ngbuti n. 拉削；拉孔；推削；擴孔v. 鉆孔；開口（拉削）, and reaming（鉸）.機械加工性能是在指對工件材料使用刀具進行諸如車、鉆、銑、拉削、鉸加工時的難易程度。In the machining of metal, the metal being cut, the cutting tool, the coolant, the process and type of machine tool（機床）, and the cutting conditions all influence the results. By changing any one of these facto

49、rs, different results will be obtained. The criterion kraitirinn. （批評判斷的）標準；準則；規(guī)范；準據(jù)（標準） upon which the ratings（等級） listed are based(等級評定的標準) is the relativeadj. 相對的；有關系的；成比例的 volume of various（不同種） materials that may be removed by turning under fixed conditions to produce an arbitrary（任意的） fixed am

50、ount of tool wear. 在對金屬進行加工時，被切削的金屬，切削刀具，冷卻液，使用的機床的種類，切削條件均影響著切削效果。改變任何一種均會產生不同的切削效果。切削效果評定的準則是：車削時在固定的切削條件下產生一定量的刀具磨損時，被加工試件相應的材料去除量。淬透性：指在規(guī)定條件下，決定鋼材淬硬深度和硬度分布的特性。即鋼淬火時得到淬硬層深度大小的能力，它表示鋼接受淬火的能力。鋼材淬透性好與差，常用淬硬層深度來表示。淬硬層深度越大，則鋼的淬透性越好。鋼的淬透性是鋼材本身所固有的屬性，它只取決于其本身的內部因素，而與外部因素無關。鋼的淬透性主要取決于它的化學成分，特別是含增大淬透性的合金元

51、素及晶粒度，加熱溫度和保溫時間等因素有關。淬透性好的鋼材，可使鋼件整個截面獲得均勻一致的力學性能以及可選用鋼件淬火應力小的淬火劑，以減少變形和開裂。 淬透性主要取決于其臨界冷卻速度的大小，而臨界冷卻速度則主要取決于過冷奧氏體的穩(wěn)定性，影響奧氏體的穩(wěn)定性主要是：1.化學成分的影響 碳的影響是主要的，當C小于1.2時，隨著奧氏體中碳濃度的提高，顯著降低臨界冷卻速度，C曲線右移，鋼的淬透性增大；當C大于時，鋼的冷卻速度反而升高，C曲線左移，淬透性下降。其次是合金元素的影響，除鈷外，絕大多數(shù)合金元素溶入奧氏體后，均使C曲線右移，降低臨界冷卻速度，從而提高鋼的淬透性。2.奧氏體晶粒大小的影響 奧氏體的實

52、際晶粒度對鋼的淬透性有較大的影響，粗大的奧氏體晶粒能使C曲線右移，降低了鋼的臨界冷卻速度。但晶粒粗大將增大鋼的變形、開裂傾向和降低韌性。3.奧氏體均勻程度的影響 在相同冷度條件下，奧氏體成分越均勻，珠光體的形核率就越低，轉變的孕育期增長，C曲線右移，臨界冷卻速度減慢，鋼的淬透性越高。4.鋼的原始組織的影響 鋼的原始組織的粗細和分布對奧氏體的成分將有重大影響。5.部分元素，例如Mn，Si等元素對提高淬透性能起到一定作用，但同時也會對鋼材帶來其他不利的影響。可鍛性(forgeability)金屬具有熱塑性，在加熱狀態(tài)(各種金屬要求溫度不同)，可以進行壓力加工，稱為具有可鍛性?？慑懶裕褐附饘俨牧显趬?/p>

53、力加工時，能改變形狀而不產生裂紋的性能。它包括在熱態(tài) 或 冷態(tài)下能夠進行錘鍛，軋制，拉伸，擠壓等加工?？慑懶缘暮脡闹饕c金屬材料的化學成分有關討論 元素在鋼中的形成物對可鍛性的影響1C 與Fe形成滲碳體Fe3C，與其它合金元素形成合金滲碳體(FeM)3C或合金碳化物。所有碳化物都有硬度高、塑性低、熔點高的特點，但滲碳體型碳化物在加熱到鍛造溫度時經(jīng)適當保溫可大部分或全部溶入固溶體中，而合金碳化物較難溶入固溶體中，對鋼的可鍛性影響最大。一般高合金工具鋼含碳高，故具有變形抗力大，塑性差，碳化物不易被粉碎等特點。2Mn 在鋼中形成MnS以代替FeS。因MnS熔點高（1620），且呈斷續(xù)分布，不像FeS

54、熔點988，呈網(wǎng)狀分布在晶界，所以可減少熱脆。錳對鋼的過熱性（粗晶）很敏感，鋼錠加熱溫度過高，易生粗晶，使鍛造困難。錳對珠光體鋼的可鍛性影響較小，奧氏體錳鋼臨界點將降低。3 Ni煉鋼時有Ni極易吸收氫形成大量氣泡，鍛造時引起開裂。Ni與Mn的作用相反，它促使硫化物成網(wǎng)狀分布于晶界，使鍛造時開裂，所以不宜在含硫的爐氣中加熱。珠光體Ni鋼在鍛造時易形成片狀破裂和帶狀組織。為了消除這種組織可采用鐓粗和拔長交錯進行，或在10001100下長時期擴散退火。4 Cr鉻在鋼中形成較穩(wěn)定的碳化物，提高碳化物在鋼中的溶解溫度，減慢溶解速度。鉻能促進使鑄錠生成大晶粒，冷卻時沿晶界形成內裂。高鉻鋼在空氣中冷卻即能淬

55、火，常在表面生裂，所以不易鍛造。5 V與碳形成穩(wěn)定碳化物V能使鋼生成細晶組織，阻止過熱，適當加入對鍛性有利。6 Mo鉬的熔點高，能降低鋼的過熱傾向它和Ni一樣，使硫化物以網(wǎng)狀分布在晶界。含有0.7%C，25%Mo的鉬鋼，鍛造時無特殊困難。這些鋼在空冷時間淬火，要防止冷裂。Mo提高鋼的熱強性，提高變形抗力。7 W與碳形成穩(wěn)定的碳化物提高鋼的熱強性，增大變形抗力8 Cu銅在鋼中可溶于鐵素體中，也可沿晶界析出游離銅銅中含0.15%Cu時，加熱不當，表面易生裂紋，高溫軋制時易產生熱脆9 B硼能細化晶粒，能溶解在和固溶體中，與Fe化合成Fe2B鋼中含B0.007%時，鍛造易裂10 S在鋼中形成硫化物或共

56、晶體，如FeS、Fe的熔點為985，且成網(wǎng)狀布于晶界顯著降低可鍛性（紅脆）11 P促成偏析，使晶粒粗大，容易引起鍛件表面龜裂降低可鍛性Unit 3 Mechanical Properties of MaterialsThe material properties can be classified into three major headings: (i) Physical, (ii) Chemical, (iii) Mechanical.Physical propertiesDensity or specific gravity, moisture mist n. 水分；濕度；潮濕；降雨量

57、 content, etc., can be classified under this category.Chemical propertiesMany chemical properties come under歸入 this category. These include acidity sidti n. 酸度；酸性；酸過多；胃酸過多 or alkalinity,lklinti n. 堿度；堿性, reactivity化學反應的活性 and corrosion. The most important of these is corrosion which can be explained

58、 in laymans terms as the resistance of the material to decay腐朽，腐爛 while in continuous use in a particular atmosphere.Mechanical propertiesMechanical properties include the strength properties like tensile, compression, shear, torsion, impact, fatigue and creepn. 爬行；毛骨悚然的感覺；諂媚者vi. 爬行；蔓延；慢慢地移動；起雞皮疙瘩creep:蠕變|潛變|