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 posed, about half are classified as metals. The distinction between a metal and a nonmetal is not always clear-cut. The most basic

2、definition centers around以為中心 the type of bonding e*isting between the atoms of the element, and around the characteristics of certain of the electrons*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 properties

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

4、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 paratively high, although, the fracture forces is not nearly =far from,much less than as high as would

5、 be e*pected 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 ,krist'linti. A crystalline solid is one in which the constituent atoms are located

6、 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 directions o

7、f the a*es of the array define the orientation of the crystal in space. The metals monly used in engineering practice are posed 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 are everyw

8、here 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 posed of only one type of atom) has never been produced. Engineers would not be particularly interested in such a metal e

9、ven if it were to be produced, because it would be soft and weak. The metals used mercially inevitably不可防止地 contain small amounts of one or more foreign elements, either metallicmetallic mi'tælik, me-adj. 金屬的，含金屬的 or nonmetallic. These foreign elements may be detrimental有害的, they may be ben

10、eficial, 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 monly added deliberately成心地，蓄意地 in substantialadj. 大量的；實質的；內容充實的su

11、bstantial evidence:實質體證據|實質性證據|實質證據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 enpass both a mercially pure metal and its alloys. Perhaps it can

12、 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 position of a metal or an alloy must be known and controlled within certai

13、n limits if consistent一致的 performance is to be achieved in service. Thus chemical position 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 produced and used in lar

14、ge 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. Ne*t in importance for structural uses (that is, for structu

15、res that are e*pected to carry loads) are aluminum鋁, copper, nickel, and titanium tai'teinim, 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 e*pected, the remainders are all used in rathe

16、r相當 special applications. For e*ample, nickel alloys are used principally主要地 in corrosion-and heat-resistant applications, while titanium is used e*tensively廣泛地 in the aerospace industry because its alloys have good binations of high strength and low density. Both nickel and titanium are used in hig

17、h-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*的喇嘛教。 properties here. Suffice it to say1. Suffice it to say that you love me.只要說你愛我就夠了。2. Suffice it to

18、 say that the gun was his.只需說這槍是他的就夠了。 that a whole ple* 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 e*ample, have to be strong and yet have reasonable corrosion resistance; it may have to

19、 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.在人類社會的開展中，金屬的應用起著關鍵性的作用。構成物質的大約100種根本元素中，大約有一半為金屬。金屬和非金屬之間的區別不是特別明顯。最根本的定義集中在元素原子間存在的連接形式和與這些原子相關聯的電子的*些

20、特性。然而，在實際應用中，可以將具有*些特性集合金屬定義為*種元素。除了少數例外金屬在常溫下是固態的。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則大。從我們的觀點來看，在所有的特性中結晶性是最重要的。結晶體是這樣一種構造，組成它的原子定位在規則的三維排列中，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律性變化，原子間距是金屬的一種特性。三維排列的軸線決定了晶體在空間中的方向。在工程

21、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。在大多數情況下，晶粒在空間中是自由排列的。在原子圍，晶粒之間相互接觸嚴密結合。晶粒之間連接區域被稱為晶界。絕對純潔的金屬從來也沒有被生產出來過。即使絕對純潔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*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參加一定數量的合金元素。得到的物質被叫做合金。金屬和合金區別不大。金屬這

22、個詞可以包括工業用純金屬和它的合金。也許可以這樣說，合金元素越成心的被添加，被添加的合金元素的量越大，則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出穩定一致的特性，在其中添加何種化學成分，它的量多大都應該在控制圍之。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金屬被大量生產和使用。到目前為止最重要的是鐵，以它為根底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%。在構造應用也就是說，可以承受載荷的構造中居于其次位置的是鋁、銅、鎳和鈦。在所有的金屬產

23、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中。鎳合鈦有高本錢和高質量的使用特性，事實上，它們高的本錢限制了它們的應用。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，掌握其構造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；它可以被循環利用；它的本錢和實用性是首要的。Unit 2 Selection of Construction Materials工程

24、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:dn'biltin. 可硬化性；淬硬性, price, and availability ,veil'bilti是產品在被調用時能夠運行即未處于失效或修復狀態的概率。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。

25、, 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 mi'stirisadj. 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 range of properties is available in

26、 any steel after heat treatment; this is particularly true of alloy steels.在鋼之間沒有太大的區別；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*些能力，或者是*種鋼具有神奇的名字。經過熱處理后，任何一種鋼都具有大圍的特性；這種性質同樣在合金鋼中存在。Considerations in fabrication(制造)The properties of the final part(hardness, strengt

27、h, and machinability m,i:n'biltin. 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 白費力，都改變不了既定的現 實to improve its

28、 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。可鍛性與材料的最后特性聯系不大；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展細化，大尺寸晶粒是最好的。Low-carbon, nickel-chromium(鉻) steels are just about幾乎

29、，差不多jas plastic at high temperature under a single 520-ft·lb(1 ft·lb=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-carbon steels. Chromium

30、seems to harden steel at forging temperatures, but vanadium(釩) has no discernible(可區分的) 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-ft·lb的沖擊下表現出與一樣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。FormabilityThe cold-f

31、ormability of steel is a function(功能) of its tensile strength bined 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 without cracking. The force

32、 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

33、否則在發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場變形。與此同時，加工硬化也同時發生，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 be done leisurely緩慢地，沉著不迫地 in two

34、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現有時可通過一次快速加載完成大拉伸，但以緩慢的方式兩三次加載卻不能實現。如果拉伸進展了一半就停頓

35、了，則在再加工之前應先退火，也就是說工件是否有時間進展加工硬化。這不是一種科學的表達方法，但確實是發生了。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 operation and the warpage翹曲，扭曲 in any任何一種 sub

36、sequent 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，劇烈地 during heat treating. virtuen.德行, 美德, 貞操, 優點, 成效, 效力, 英勇 believed in the virtue of prayer.相信祈禱的力量應力在高于屈服點的加工硬化區進展冷加工很容易產生應力。例如工件停頓成型

37、加工后會發生回彈，在隨后的熱處理后，工件會發生翹曲。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應力，也會在熱處理中呈現嚴重的翹曲。When doubt e*ists 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 internal stresses, the piece is likely to可能 deform. Pieces that will

38、 warp severely while being heated have been seen, yet 然而the heat-treater熱處理爐was e*pected to有望做*事；被期待做*事put them throughput through 完成 and bring them out better than they were in the first place.當是否應力會引起翹曲的疑心存在時，可以通過將工件加工至1100然后進展冷卻來驗證。如果存在應力，工件會發生變形。經過熱處理的工件像我們看到的那樣會發生嚴重的翹曲，但是我們仍然希望工件被扔到熱處理爐中被處理，這樣好

39、過它存在應力的狀態。WeldingThe ma*imum 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 important factors: the amount of heats that is put in ; the rate at whic

40、h it is removed.焊接不需要預熱或之后進展熱處理就能平安焊接的最高碳含量為0.3。高碳鋼通過適宜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 decreased(減少). A preheat will do the same thing. For e*ample, sae4150 steel

41、, 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 the most rapid air-hardening風硬鋼 steels are weldable if preheated and wel

42、ded 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展了加熱，所以冷卻速度降低。預熱可以取得與之相當的效果。例如當 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到達良好的焊接效果。MachinabilityMachinability機械加工性能 means several things. To production men it generally means being able to remove metal at the faste

43、st 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 bination.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 not determined by hardness硬度 alone, but by the toughness韌性, microstructure, chemic

44、al position成分, and tendency傾向 of a metal to harden under cold work. In the misleading e*pression “too hard to machine, the word “hard is usually meant to be synonymous同義的 with “difficult. Many times a material is actually too soft to machine readily. Softness and toughness may cause the metal to tea

45、r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 'sækrifais n. 犧牲；祭品；供奉All gains are made at some sacrifice.Most people might choose to divert the course of

46、the train, and sacrifice only one child.犧牲 in ductility. E*amples 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，微觀構造，化學成分和在冷加工下金屬所呈現的硬化特性所決定。在容易混淆的表示“難加工中，“hard與“difficult同義。許多時候，因為材料過軟而難于穩定加工。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參加合金從而犧牲它的延展性來提高加工性能。如黃銅中參加鉛鋼

47、中參加硫磺。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, broaching'buti 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展諸如車、鉆、銑、拉削、鉸加工時的難易程度。In the machining

48、 of metal, the metal being cut, the cutting tool, the coolant, the process and type of machine tool機床, and the cutting conditionsall influence the results. By changing any one of these factors, different results will be obtained. The criterion krai'tirinn. 批評判斷的標準；準則；規*；準據標準 upon which the ratin

49、gs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 fi*ed conditions to produce an arbitrary任意的 fi*ed amount of tool wear. 在對金屬進展加工時，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

50、磨損時，被加工試件相應的材料去除量。淬透性：指在規定條件下，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，它表示鋼承受淬火的能力。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定性，

51、影響奧氏體的穩定性主要是：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 在一樣冷度條件下，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

52、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.局部元素，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(各種金屬要求溫度不同)，可以進展壓力加工，稱為具有可鍛性。可鍛性：指金屬材料在壓力加工時，能改變形狀而不產生裂紋的性能。它包括在熱態 或 冷態下能夠進展錘鍛，軋制，拉伸，擠壓等加工。可鍛性的好壞主要與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

53、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適當保溫可大局部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，且呈斷續分布，不像FeS熔點988，呈網狀分布在晶界，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。3Ni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

54、反，它促使硫化物成網狀分布于晶界，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織進展，或在10001100下長時期擴散退火。4Cr鉻在鋼中形成較穩定的碳化物，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，冷卻時沿晶界形成裂。高鉻鋼在空氣中冷卻即能淬火，常在外表生裂，所以不易鍛造。5V與碳形成穩定碳化物V能使鋼生成細晶組織，阻止過熱，適當參加對鍛性有利。6Mo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

55、火，要防止冷裂。Mo提高鋼的熱強性，提高變形抗力。7W與碳形成穩定的碳化物提高鋼的熱強性，增大變形抗力8Cu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，外表易生裂紋，高溫軋制時易產生熱脆9B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10S在鋼中形成硫化物或共晶體，如FeS、Fe的熔點為985，且成網狀布于晶界顯著降低可鍛性紅脆11P促成偏析，使晶粒粗大，容易引起鍛件外表龜裂降低可鍛性Unit 3 Mechanical Properties of MaterialsThe material properties can

56、 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 content, etc., can be classified under this category.Chemical propertiesMany chemical properties e under歸入 this category. These i

57、nclude acidity 'sidti n. 酸度；酸性；酸過多；胃酸過多 or alkalinity,ælk'linti n. 堿度；堿性, reactivity化學反響的活性 and corrosion. The most important of these is corrosion which can be e*plained in laymans terms as the resistance of the material to decay腐朽，腐爛 while in continuous use in a particular atmosphere.

58、Mechanical propertiesMechanical properties include the strength properties like tensile, pression, 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|漸變creep strength:蠕變強度|潛變強度|蠕變弱度creep strain:蠕變變形|蠕動應變|蠕變應變. The tensile strength of a material is obtained by dividing the ma*i