精選同濟(jì)大學(xué)蘇小卒版土木工程專業(yè)英語翻譯考試整理秘籍

1、同濟(jì)大學(xué)蘇小卒版土木工程專業(yè)英語翻譯考試整理秘籍第一單元Fundamentally, engineering is an end-product-oriented discipline that is innovative, cost-conscious and mindful of human factors. It is concerned with the creation of new entities, devices or methods of solution: a new process, a new material, an improved power source, a

2、more efficient arrangement of tasks to accomplish a desired goal or a new structure. Engineering is also more often than not concerned with obtaining economical solutions. And, finally, human safety is always a key consideration.從根本上，工程是一個以最終產(chǎn)品為導(dǎo)向的行業(yè)，它具有創(chuàng)新、本錢意識，同時也注意到人為因素。 它與創(chuàng)立新的實體、 設(shè)備或解決方案有關(guān)：新工藝、新材

3、料、一個改良的動力來源、任務(wù)的一項更有效地安排，用以完成所需的目標(biāo)或創(chuàng)立一個新的結(jié)構(gòu)。 工程是也不僅僅關(guān)心獲得經(jīng)濟(jì)的解決方案。最終，人類平安才是一個最重要的考慮因素。Engineering is concerned with the use of abstract scientific ways of thinking and of defining real world problems. The use of idealizations and development of procedures for establishing bounds within which behavior c

4、an be ascertained are part of the process.工程關(guān)心的是，使用抽象的科學(xué)方法思考和定義現(xiàn)實世界的問題。理想化的使用和開展建立可以確定行為的邊界的程序，是過程的一局部。Many problems, by their very nature, cant be fully describedeven after the fact, much less at the outset. Yet acceptable engineering solutions to these problems must be found which satisfy the defi

5、ned needs. Engineering, then, frequently concerns the determination of possible solutions within a context of limited data. Intuition or judgment is a key factor in establishing possible alternative strategies, processes, or solutions. And this, too, is all a part of engineering.很多的問題，就其本身的性質(zhì)而言，不能完全

6、被描述 即使這一事實，在其開始之前。然而還必須找到對于這些問題可接受的工程解決方案，來滿足預(yù)定的需求。直覺或判斷是建立可能的替代策略、 流程或解決方案的關(guān)鍵因素。而這也是工程的一局部。Civil engineering is one of the most diverse branches of engineering. The civil engineer plans, designs, constructs, and maintains a large variety of structures and facilities for public, commercial and indus

7、trial use. These structures include residential, office, and factory buildings; highways, railways, airports, tunnels, bridges, harbors, channels, and pipelines. They also include many other facilities that are a part of the transportation systems of most countries, as well as sewage and waste dispo

8、sal systems that add to our convenience and safeguard our health.土木工程是工程的最多樣化的分支機構(gòu)之一。土木工程師方案、設(shè)計、施工，和維護(hù)大量的結(jié)構(gòu)和公共、商業(yè)和工業(yè)使用的設(shè)施。這些結(jié)構(gòu)包括住宅，辦公室和工廠大廈；公路、鐵路、機場、隧道、橋梁、港口、渠道和管道。在其他大多數(shù)的國家它們還包括運輸系統(tǒng)許多其他設(shè)施，以及將為我們的生活帶來便利的和維護(hù)我們的健康污水及廢物處理系統(tǒng)。The term “civil engineer did not come into use until about 1750, when John Smea

9、ton, the builder of famous Eddystone lighthouse near Plymouth, England, is said to have begun calling himself a “civil engineer to distinguish himself from the military engineers of his time. However, the profession is as old as civilization.直到大約1750年，人們才開始使用“土木工程師這一術(shù)語。約翰.斯密頓在英格蘭普利茅斯附近，建造了著名的埃迪斯通燈塔的

10、建造師，開始自稱為“土木工程師來將自己與當(dāng)時的軍事工程師區(qū)分開。然而，土木工程這個職業(yè)卻像文明一樣古老。 In ancient Egypt the simplest mechanical principles and devices were used to construct many temples and pyramids that are still standing, including the great pyramid at Giza and the temple of Amon-Ra at Karnak. The great pyramid, 481 feet(146.6 me

11、ters)high, is made of 2.25 million stone blocks having an average weight of more than 1.5tons (1.4 metric tons). Great numbers of men were used in the construction of such monuments. The Egyptians also made obelisks by cutting huge blocks of stone, some weighing as much as 1000 tons (900 metric tons

12、). Cutting tools of hard bronze were used.古埃及人用最簡單的機械原理和裝置建造了許多至今仍矗立的廟宇和金字塔，包括吉薩大金字塔和在卡納克的Amon-Ra的寺廟。這個大金字塔，481英尺146.6 米高，由2250000個石塊組成，石塊的平均重量超過1.5噸1.4 噸。建造如此的紀(jì)念性建筑使用了大量的人力。埃及人也作了一些重達(dá)1000噸(900噸)的石頭的大塊切割的方尖塔。硬青銅的切削刀具在其中使用到了。The Egyptians built causeways and roads for transporting stone from the quar

13、ries to the Nile. The large blocks of stone that were erected by the Egyptians were moved by using levers, inclined planes, rollers, and sledges.為了從采石場向尼羅河運輸石材埃及人建造了長堤和道路。由埃及人豎設(shè)的大塊石頭通過使用拉桿、斜平面、滾子和雪橇來移動。The Egyptians were primarily interested in the know-how of construction; They had very little inte

14、rest in why-for of use .In contrast, the Greeks made great strides in introducing theory into engineering problems during the 6th to 3rd centuries B.C. They developed an abstract knowledge of lines, angles, surfaces, and solids rather than referring to specific objects. The geometric base for Greek

15、building construction included figures such as the square, rectangle, and triangle.埃及人主要對如何建造感興趣；他們對為什么這么使用沒有什么太多的興趣。相反，在公元前六世紀(jì)到公元前三世紀(jì)希臘人取得了巨大的進(jìn)步于工程理論的推廣。他們開展了線、角度、面，和實體的抽象的知識，而不是與特定的對象產(chǎn)生聯(lián)系。 希臘建筑施工的幾何根底包括數(shù)字如正方形、矩形和三角形。The Greek architekton was usually the designer, as well as the builder, of archite

16、ctural and engineering masterpieces. He was an architect and engineer. Craftsmen, masons, and sculptors worked under his supervision. In the classical period of Greece all important buildings were built of limestone or marble; the Parthenon, for example, was built of marble.希臘建筑師 通常是建筑工程杰作的設(shè)計師同時也是建造

17、師。 他既是一個建筑師也是工程師。工匠、石匠和雕塑家在他的監(jiān)督下工作。在希臘古典時期所有重要建筑物是由石灰石或大理石建造的；以帕臺農(nóng)神廟為例，由大理石建成的。UNIT 3The principal construction materials of earlier times were wood and masonry-brick, stone, or tile, and similar materials. The courses or layers磚層were bound together with mortar or bitumen, a tarlike substance, or so

18、me other binding agent. The Greeks and Romans sometimes used iron rods or clamps to strengthen their building. The columns of the Parthenon in Athens雅典的帕臺農(nóng)神廟, for example, have holes drilled鉆孔 in them for iron bars that have now rusted away銹蝕殆盡. The Romans also used a natural cement called pozzolana

19、, made from volcanic ash, that became as hard as stone under water. 早期主要的建筑材料是木材和砌體，如磚、石、瓦以及類似的材料。磚層之間通過砂漿、瀝青一種焦油狀的物質(zhì)或其他一些粘合劑粘合在一起。希臘人和羅馬人有時用鐵條或夾子來加固他們的房屋。例如，雅典的帕臺農(nóng)神廟柱子中曾鉆孔以便參加鐵條，如今都已銹蝕殆盡。羅馬人也用稱作白榴火山灰的天然水泥，它用火山灰制作，在水中會變得與石頭一樣堅硬。 Both steel and cement, the two most important construction materials of

20、 modern times, were introduced推廣 in the nineteenth century. Steel, basically an alloy of iron 鐵合金and a small amount of carbon, had been made up to that time到那個時候 by a laborious繁復(fù)的 process that restricted it to such special uses as sword blades刀刃. After the invention of the Bessemer process 貝塞麥煉鋼法in

21、1856, steel was available in large quantities at low prices. The enormous advantage of steel is its tensile strength; that is, it does not lose its strength when it is under a calculated degree (適當(dāng)?shù)? of tension, a force which, as we have seen, tends to 往往pull apart many materials. New alloys have fu

22、rther increased the strength of steel and eliminated some of its problems, such as fatigue, which is a tendency for it to weaken as a result of continual changes in stress連續(xù)的應(yīng)力變化. 作為現(xiàn)代兩種最重要的建筑材料，鋼材與水泥在十九世紀(jì)得到了推廣。直到那個時候，鋼材才通過繁復(fù)的過程制造出來，根本上是鐵合金，并含有少量的碳，因而被限制在一些特殊的用途如刀刃。在1856年創(chuàng)造了貝塞麥煉鋼法后，鋼材才得以大量低價獲得。鋼材巨大的

23、優(yōu)勢即是它的抗拉強度，也就是當(dāng)它在適當(dāng)?shù)睦ο虏粫姸龋缥覀兯吹降?，該力往往能夠?qū)⒑芏嗖牧侠_。新的合金進(jìn)一步提高了鋼材的強度，并消除了一些缺點，如疲勞，即在連續(xù)的應(yīng)力變化下導(dǎo)致強度減弱的趨勢。Modern cement, called Portland cement, was invented in 1824. It is a mixture of limestone石灰石 and clay, which is heated and then ground into a powder磨成粉末. It is mixed at or near the construction site

24、 施工現(xiàn)場with sand, aggregate (small stones, crushed rock, or gravel), and water to make concrete. Different proportions of the ingredients 配料produce concrete with different strength and weight. Concrete is very versatile; it can be poured, pumped, or even sprayed into 噴射成all kinds of shapes. And wherea

25、s steel has great tensile strength, concrete has great strength under compression. Thus, the two substances complement each other互補. 現(xiàn)代水泥創(chuàng)造于1824年，稱為波特蘭水泥。它是石灰石和粘土的混合物，加熱后磨成粉末。在或靠近施工現(xiàn)場，將水泥與砂、骨料小石頭、壓碎的巖石或礫石、水混合而制成混凝土。不同比例的配料會制造出不同強度和重量的混凝土?；炷恋挠猛竞芏啵梢詽仓?、泵送甚至噴射成各種形狀?；炷辆哂泻艽蟮目箟簭姸龋摬木哂泻艽蟮目估瓘姸?。這樣，兩種材料可以互

26、補。 They also complement each other in another way: they have almost the same rate of contraction and expansion. They therefore can work together in situations where在情況下 both compression and tension are factors主要因素. Steel rods鋼筋 are embedded in埋入concrete to make reinforced concrete in concrete beams

27、or structures where tension will develop出現(xiàn). Concrete and steel also form such a strong bond - the force that unites粘合 them - that the steel cannot slip滑移 with the concrete. Still還有 another advantage is that steel does not rust in concrete. Acid酸 corrodes steel, whereas concrete has an alkaline chemi

28、cal reaction, the opposite of acid. 它們也以另外一種方式互補：它們幾乎有相同的收縮率和膨脹率。因此，它們在拉、壓為主要因素時能共同工作。在出現(xiàn)拉力的混凝土梁或結(jié)構(gòu)中，將鋼筋埋入混凝土而成鋼筋混凝土?；炷僚c鋼筋形成如此強大的結(jié)合力這個力將它們粘合在一起以致于鋼筋在混凝土中不會滑移。還有另一個優(yōu)勢是鋼筋在混凝土中不會銹蝕。酸能腐蝕鋼筋，而混凝土?xí)l(fā)生堿性的化學(xué)反響，與酸相反。 The adoption of structural steel and reinforced concrete caused major changes in traditional

29、construction practices施工作業(yè). It was no longer necessary to use thick walls of stone or brick for multistory buildings, and it became much simpler to build fire-resistant floors防火地面. Both these changes served to有利于 reduce the cost of construction. It also became possible to erect建造buildings with great

30、er heights and longer spans. 結(jié)構(gòu)鋼與鋼筋混凝土的采用使傳統(tǒng)的施工作業(yè)發(fā)生了明顯的變化。對多層建筑，再也沒必要采用厚的石墻或磚墻，且施工防火地面變?yōu)槿菀椎枚?。這些變化有利于降低建筑的本錢。它也使建造高度更高和跨度更大的建筑物成為可能。 Since the weight of modern structures is carried承受 by the steel or concrete frame, the walls do not support the building. They have become curtain walls, which keep out

31、 the weather and let in light. In the earlier steel or concrete frame building, the curtain walls were generally made of masonry; they had the solid look of bearing walls承重墻. Today, however, curtain walls are often made of lightweight materials such as glass, aluminum, or plastic, in various combina

32、tions. 由于現(xiàn)代結(jié)構(gòu)的重量由鋼或混凝土框架承受，墻體不再支承建筑物。它們成為幕墻，將日曬風(fēng)吹雨打阻擋在外，而讓光線進(jìn)入。在較早的鋼或混凝土框架建筑中，幕墻一般由砌體構(gòu)成；它們具有承重墻的結(jié)實外觀。但是今天，幕墻通常由輕質(zhì)材料組成，如玻璃、鋁或塑料，并形成不同的組合。 Another advance in steel construction結(jié)構(gòu) is the method of fastening together連在一起 the beams. For many years the standard method was riveting. A rivet is a bolt with

33、a head that looks like a blunt screw圓頭螺絲釘 without threads螺紋. It is heated, placed in holes through the pieces of steel鋼構(gòu)件, and a second head is formed at the other end by hammering錘擊it to hold it in place固定就位. Riveting has now largely been replaced by welding, the joining together of pieces of steel

34、 by melting熔化 a steel material between them under high heat. 鋼結(jié)構(gòu)中的另一個進(jìn)步是梁的連接方式。在很多年里，連接的標(biāo)準(zhǔn)方式是鉚接。鉚釘是個有頭的螺栓，看上去象個沒有螺紋的圓頭螺絲釘。鉚釘加熱后穿過鋼構(gòu)件之間的孔洞，并通過錘擊另一端而形成第二個鉚釘頭，從而將其固定就位。如今鉚接已大量地被焊接所替代，鋼構(gòu)件間的連接通過在高熱下熔化它們之間的鋼材料即焊條進(jìn)行。 Prestressed concrete is an improved form of reinforcement加強方法. Steel rods are bent into th

35、e shapes to give them the necessary degree of tensile strength. They are then used to prestress 對.預(yù)加應(yīng)力concrete, usually by one of two different methods. The first is to leave channels in a concrete beam that correspond to相應(yīng)于 the shapes of the steel rods. When the rods are run through the channels, t

36、hey are then bonded to the concrete by filling the channels with grout, a thin mortar or binding agent. In the other (and more common) method, the prestressed steel rods are placed in the lower part of a form模板 that corresponds to the shape of the finished structure成品結(jié)構(gòu), and the concrete is poured a

37、round them. Prestressed concrete uses less steel and less concrete. Because it is so economical, it is a highly desirable非常理想 material. 預(yù)應(yīng)力混凝土是加強法的改良形式。將鋼筋彎成一定的形狀以使它們具有必要的抗拉強度，然后用該鋼筋對混凝土施加預(yù)應(yīng)力，通?？刹捎脙煞N不同方法中的任何一種。第一種方法是在混凝土梁中按鋼筋的形狀留下孔道，當(dāng)鋼筋穿過孔道后，通過在孔道內(nèi)灌注薄砂漿一種稀薄的砂漿或粘合劑將鋼筋與混凝土粘結(jié)在一起。另一種更常用的方法是將預(yù)應(yīng)力鋼筋置于按成品結(jié)構(gòu)

38、的形狀設(shè)置的模板的較低部位，然后將混凝土倒入模板而包圍著鋼筋。預(yù)應(yīng)力混凝土使用了較少的鋼筋和混凝土，由于它是如此的經(jīng)濟(jì)，因此是一種非常理想的材料。 Prestressed concrete has made it possible to develop建造 buildings with unusual shapes, like some of the modern sports arenas, with large space unbroken by any obstructing supports阻礙的支撐物. The uses for this relatively new structu

39、ral method are constantly being developed不斷地擴(kuò)大. 預(yù)應(yīng)力混凝土使建造獨特形狀的建筑物成為可能，象一些現(xiàn)代的運動場，它具有不受任何支撐物阻擋視線的大空間。這種較新的結(jié)構(gòu)方法的使用正在不斷地被擴(kuò)大。 The current tendency is to develop采用 lighter materials, aluminum, for example, weighs much less than steel but has many of the same properties. Aluminum beams have already been us

40、ed for bridge construction and for the framework of a few buildings. 目前的趨勢是采用較輕的材料。例如，鋁的重量比鋼輕得多，但具有很多相同的性能。鋁材梁已經(jīng)用于橋梁建筑和一些建筑的框架。 Lightweight concretes, another example, are now rapidly developing開展 throughout the world. They are used for their thermal insulation(絕熱性). The three types are illustrated

41、below舉例說明如下: (a) Concretes made with lightweight aggregates; (b) Aerated concretes (US gas concretes) foamed起泡 by whisking攪拌or by some chemical process during casting; (c) No-fines concretes. 另一個例子是輕質(zhì)混凝土，如今已在全世界快速地開展，因它們的絕熱性而被采用，其三種類型舉例說明如下：(a)輕質(zhì)骨料制成的混凝土；(b)通過澆筑時攪拌或一些化學(xué)方法起泡而成的加氣混凝土US加氣混凝土；(c)無細(xì)骨料混凝土

42、。 All three types are used for their insulating properties絕熱性, mainly in housing, where they give high非常 comfort in cold climates and a low cost of cooling降溫本錢in hot climates. In housing, the relative weakness of lightweight concrete walls is unimportant, but it matters有重大關(guān)系 in roof slabs, floor sla

43、bs and beams. 這三種類型的混凝土都是由于它們的絕熱性而被使用，主要用于房屋，使其在寒冷的氣候中非常舒服，在炎熱的氣候中降溫的本錢不高。在房屋中，墻采用較薄弱的輕質(zhì)混凝土不重要，但是屋面板、樓面板和梁采用輕質(zhì)混凝土那么有重大關(guān)系。 In some locations, some lightweight aggregates cost little more than幾乎等于 the best dense致密 aggregates and a large number of 大量 floor slabs have therefore been built of lightweight

44、 aggregate concrete purely for its weight saving, with no thought of沒考慮 its insulation value. 在某些地區(qū)，一些輕質(zhì)骨料的費用幾乎等于最致密的骨料，因此大量的樓面板采用輕骨料混凝土制作純粹是節(jié)約重量，而沒考慮它的絕熱價值。 The lightweight aggregate reduces the floor dead load恒載 by about 20 per cent resulting in導(dǎo)致considerable savings in the floor樓蓋結(jié)構(gòu) steel in ever

45、y floor and the roof, as well as in the column steel and (less) in the foundations. One London contractor承包商prefers to use lightweight aggregate because it gives him the same weight reduction in the floor slab as the use of hollow tiles, with simpler organization and therefore higher speed and profi

46、t. The insulation value of the lightweight aggregate is only important in the roof insulation, which is greatly improved改良. 輕質(zhì)骨料使樓面的恒載減少了約20%，因而大量的節(jié)約了每層樓面以及屋面的樓蓋結(jié)構(gòu)中的鋼材和柱子與根底中較少的鋼材使用量。一位倫敦的承包商寧愿使用輕質(zhì)骨料，因為這使樓面板上減少的重量與用空心磚相同，且組織更簡單，因而速度和利潤更高。輕質(zhì)骨料的絕熱價值只在屋面絕熱時顯得重要，它已被大大地改良了。UNIT 4 Mechanics of Materials d

47、eals with研究the response of various bodies, usually called members構(gòu)件, to applied forces施加力. In Mechanics of Engineering Materials the members have shapes that either exist in actual structures or are being considered for their suitability根據(jù)其需要as parts of proposed擬建的engineering structures. The materia

48、ls in the members have properties that are characteristic of commonly used常用的engineering materials such as steel, aluminum, concrete, and wood. 材料力學(xué)用以研究不同物體通常稱為構(gòu)件對施加力的響應(yīng)。在工程材料力學(xué)中，構(gòu)件的形狀可以是實際結(jié)構(gòu)中存在的，也可以根據(jù)其需要而進(jìn)行考慮設(shè)計，作為擬建工程結(jié)構(gòu)的部件。構(gòu)件中材料的性能即是常用的工程材料如鋼材、鋁材、混凝土和木材的特性。 As you can see already from the variety o

49、f materials, forces, and shapes mentioned, Mechanics of Engineering Materials is of interest to對.有價值all fields of engineering. The engineer uses the principles of Mechanics of Materials to determine if the material properties and the dimensions of a member are adequate to足以ensure that it can carry i

50、ts loads safely and without excessive distortion. In general通常, then, we are interested in both the safe load that a member can carry and the associated相關(guān)的deformation. Engineering design would be a simple process if the designer could take into consideration考慮the loads and the mechanical properties

51、of the materials, manipulate利用an equation, and arrive at得到suitable dimensions. Design is seldom that simple. Usually通常, on the basis of根據(jù)experience, the designer selects a trial試算 member and then does an analysis to see if that member meets the specified requirements. Frequently常常, it does not and t

52、hen a new trial member is selected and the analysis repeated. This design cycle設(shè)計周期 continues until a satisfactory solution is obtained. The number of cycles循環(huán)次數(shù) required to find an acceptable design diminishes as the designer gains experience. 正如你已經(jīng)從提到的各種各樣的材料、力和形狀所看到的，工程材料力學(xué)對所有的工程領(lǐng)域都有價值。工程師利用材料力學(xué)的

53、原理來確定是否該材料的性能和構(gòu)件尺寸足以保證它能平安地承受荷載且沒有過多的變形。通常，我們關(guān)心的是構(gòu)件能承受的平安荷載及其相應(yīng)的變形。如果設(shè)計者能通過考慮荷載和材料的力學(xué)性能，并利用公式得到適宜的構(gòu)件尺寸，那么工程設(shè)計將是一個簡單的過程。然而設(shè)計很少那么簡單。通常，根據(jù)經(jīng)驗，設(shè)計者選擇一個試算構(gòu)件，然后進(jìn)行分析，看它是否滿足規(guī)定的要求。它常常不會滿足要求，那么再選擇一個新的試算構(gòu)件，再進(jìn)行分析。這樣的設(shè)計不斷重復(fù)，直至得到一個滿意的結(jié)果。當(dāng)設(shè)計師擁有一定的經(jīng)驗后，為得到一個可接受的設(shè)計所需要的循環(huán)次數(shù)會減少。 Design of Axially Loaded Members 軸向力構(gòu)件的設(shè)計

54、To give you some insight into 使.有一些了解the design cycle, an extremely simple member will be dealt with first. That member is a prismatic bar with a force, P, acting along its longitudinal axis in the direction縱軸向such that it tends to elongate the bar. Such a force is referred to as稱為an axial tensile l

55、oad軸向拉力, and we can readily imagine it trying to努力.pull the fibers apart and to cause failure on a transverse plane橫向平面. It is safe to assume that all fibers of the bar, in regions remote from遠(yuǎn)離the point of application of the load, are being pulled apart with the same load intensity荷載強度. With this a

56、ssumption, the load intensity or stress is uniform on a transverse plane and is given by 為了使你對設(shè)計周期有一些了解，首先研究一個非常簡單的構(gòu)件。構(gòu)件是個棱形的桿件，其上沿著它的縱軸向作用一個力P，這樣往往使桿件在該方向上伸長。這樣的力稱為軸向拉力，我們能容易地想象它在努力地將纖維拉開，導(dǎo)致橫向平面的破壞。平安地假定桿件的所有纖維在遠(yuǎn)離荷載施加點的區(qū)域以相同的荷載強度被拉開。在此假定下，荷載強度或應(yīng)力在橫向平面上是均勻的，為 when P is in以.為單位Newtons and A is in squ

57、are metres, stress, ,is in Newtons per square metre (N/m2), which is by definition根據(jù)定義Pascals (Pa).當(dāng)P的單位為牛頓、A的單位為平方米時，應(yīng)力的單位為牛頓每平方米N/m2，根據(jù)定義為帕斯卡Pa。 For a given axial load and given dimensions, the stress can be calculated from (4-1) and compared with與.相比the stress that can be safely carried by the ma

58、terial. The safe stress, known as稱為the design stress or allowable stress許用應(yīng)力, is determined by tests performed on material made to按照 the same specifications as the part being considered. A safety factor平安系數(shù), frequently imposed by a legally established code法規(guī), is applied to the strength, as determine

59、d by tests, to give the allowable stress. The allowable stress, a , is given by 對的軸向力和構(gòu)件尺寸，可根據(jù)公式4-1計算出應(yīng)力，并與材料能平安承受的應(yīng)力作比擬。平安應(yīng)力，稱為設(shè)計應(yīng)力或許用應(yīng)力，它是通過對材料的試驗來確定的，該試驗材料按照與所考慮驗算的桿件相同的標(biāo)準(zhǔn)制作。根據(jù)法規(guī)規(guī)定，通常對試驗所確定的強度考慮平安系數(shù)后得到許用應(yīng)力。許用應(yīng)力 a 為where f is the stress at which the material fails (failure to be defined later) and

60、 n is the safety factor.這里，f 為材料失效失效在下文有定義時的應(yīng)力，而n為平安系數(shù)。 It might at first起先seem that the designer would always dimension選定.的尺寸the cross section橫截面 so that the stress would exactly equal the allowable stress. However, it may be very costly to produce parts that have nonstandard sizes, so it is usuall