機(jī)械工程專(zhuān)業(yè)英語(yǔ)PPT課件

1、機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints Bolted joints are one of the most common elements in construction and machine design. They consist of cap screws or studs that capture and join other parts, and are secured with the mating of screw threads.There are two main

2、 types of bolted joint designs. In one method the bolt is tightened to a calculated clamp load, usually by applying a measured torque load. The joint will be designed such that the clamp load is never overcome by the forces acting on the joint (and therefore the joined parts see no relative motion).

3、 The other type of bolted joint does not have a designed clamp load but relies on the shear strength of the bolt shaft. This may include clevis linkages, joints that can move, and joints that rely on locking mechanism (like lock washers, thread adhesives, and lock nuts).第1頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Backgr

4、ound informationLesson 19 Screws, fasteners and joints Bolted joint Screw joint Stud joint 第2頁(yè)/共46頁(yè)Bolt The bolt assembly is used when joint parts are not too thick to drill through holes.螺栓 用于聯(lián)接二通孔薄件第3頁(yè)/共46頁(yè) Stud Stud are used in situations where a part with a through hole and a part with blind tap

5、ped hole.雙頭螺柱 用于聯(lián)接一通孔薄件和一盲孔厚件。第4頁(yè)/共46頁(yè)Screw Screws are mostly used for the cases with small bearing forces. such as inspection covers which have to be removed frequently.螺釘 多用于用于受力不大需要經(jīng)常拆卸的情況第5頁(yè)/共46頁(yè)Nut are used to match the other screw fasteners. 螺母 與其他螺紋件配合使用第6頁(yè)/共46頁(yè)Washer are used to match the ot

6、her screw fasteners. 墊圈 與其他螺紋件配合使用第7頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints Theory The clamp load, also called preload, of a cap screw is created when a torque is applied, and is generally a percentage of the cap screws proof strength. Cap screws are manufac

7、tured to various standards that define, among other things, their strength and clamp load. Torque charts are available that identify the required torque for cap screws based on their property class or grade. When a cap screw is tightened it is stretched, and the parts that are captured are compresse

8、d. The result is a spring-like assembly. External forces are designed to act on the parts that have been compressed, and not on the cap screw.第8頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints Theory The result is a non-intuitive distribution of strain; in this engin

9、eering model, as long as the forces acting on the compressed parts do not exceed the clamp load, the cap screw do not see any increased load. This model is only valid when the members under compression are much stiffer than the cap screw. This is a simplified model. In reality the bolt will see a sm

10、all fraction of the external load prior to it exceeding the clamp load, depending on the compressed parts stiffness with respect to the hardwares stiffness. 第9頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints Theory The results of this type of joint design are: Greate

11、r preloads in bolted joints reduce the fatigue loading of the hardware. For cyclic loads, the bolt does not see the full amplitude of the load. As a result, fatigue life can be increased or, if the material exhibits an endurance limit, extended indefinitely. As long as the external loads on a joint

12、dont exceed the clamp load, the hardware doesnt see any motion and will not come loose (no locking mechanisms are required). In the case of the compressed member being less stiff than the hardware (soft, compressed gaskets for example) this analogy doesnt hold true. The load seen by the hardware is

13、the preload plus the external load.第10頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints 第11頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints Theory The results of this type of joint design are: Greater preloads in bolted joints reduce t

14、he fatigue loading of the hardware. For cyclic loads, the bolt does not see the full amplitude of the load. As a result, fatigue life can be increased or, if the material exhibits an endurance limit, extended indefinitely. As long as the external loads on a joint dont exceed the clamp load, the hard

15、ware doesnt see any motion and will not come loose (no locking mechanisms are required). In the case of the compressed member being less stiff than the hardware (soft, compressed gaskets for example) this analogy doesnt hold true. The load seen by the hardware is the preload plus the external load.第

16、12頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints Thread strength Nut threads are designed to support the rated clamp load of their respective bolts. If tapped threads are used instead of a nut, then their strength needs to be calculated. Steel hardware into tapped

17、steel threads requires a depth of 1.5 thread diameter to support the full clamp load. If an appropriate depth of threads is not available, or the threads are in a weaker material than the cap screw, then the clamp load (and torque) needs to be derated appropriately.第13頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background

18、 informationLesson 19 Screws, fasteners and joints Failure modes The most common mode of failure is overloading. Operating forces of the application produce loads that exceed the clamp load and the joint works itself loose, or fails catastrophically.Over torquing will cause failure by damaging the t

19、hreads and deforming the hardware, the failure might not occur until long afterward. Under torquing can cause failures by allowing a joint to come loose. It may also allow the joint to flex and thus fail under fatigue. Brinelling may occur with poor quality washers, leading to a loss of clamp load a

20、nd failure of the joint. Corrosion, embedment and exceeding the shear stress limit are other modes of failure.第14頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、Background informationLesson 19 Screws, fasteners and joints Notes:Brinelling refers to a material surface failure caused by contact stress that exceeds the material

21、limit. This failure is caused by just one application of a load great enough to exceed the material limit. The result is a permanent dent or brinell mark. Embedment is a phenomenon in mechanical engineering in which the surfaces between mechanical members of a loaded joint embed. It can lead to fail

22、ure by fatigue as described below, and is of particular concern when considering the design of critical fastener joints.第15頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、預(yù)備知識(shí)Lesson 19 Screws, fasteners and joints 1、基本類(lèi)型u普通螺栓聯(lián)接：被聯(lián)接件上通孔和螺栓桿間留有間隙，故精度低、結(jié)構(gòu)簡(jiǎn)單。u鉸制孔用螺栓聯(lián)接：孔和螺栓桿多采用基孔制過(guò)渡配合（H7/m6、H7/n6）,精確固定被聯(lián)接件的相對(duì)位置，并可承受橫向載荷。u雙頭螺栓聯(lián)接：被聯(lián)

23、接件之一太厚或經(jīng)常拆裝u螺釘聯(lián)接：不用螺母，比雙頭螺柱簡(jiǎn)單，用途相似，多用于受力不大、不需經(jīng)常拆裝的場(chǎng)合u緊定螺釘聯(lián)接：固定兩零件的相對(duì)位置，可傳遞不太大的扭矩和力u螺栓的類(lèi)型：六角頭螺栓和雙頭螺栓u螺釘?shù)念?lèi)型：半圓頭、平頭、六角頭、圓柱頭、沉頭 第16頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、預(yù)備知識(shí)Lesson 19 Screws, fasteners and joints 2、螺紋的預(yù)緊u預(yù)緊的目的：增強(qiáng)聯(lián)接的可靠性、緊密性，防止受載后被聯(lián)接件間出現(xiàn)縫隙或發(fā)生相對(duì)滑移。選用較大的預(yù)緊力可提高聯(lián)接的可靠性和疲勞強(qiáng)度u預(yù)緊應(yīng)力不超過(guò)其材料的屈服極限的80%。u控制預(yù)緊力的方法： 1）借助測(cè)力

24、矩扳手或定力矩扳手 2）測(cè)定螺栓伸長(zhǎng)量第17頁(yè)/共46頁(yè)機(jī)械工程專(zhuān)業(yè)英語(yǔ)預(yù)備知識(shí) 一、預(yù)備知識(shí)Lesson 19 Screws, fasteners and joints 3、螺紋的防松u螺紋升角小于螺旋副的當(dāng)量摩擦角 ：自鎖性好u螺母與螺栓頭部等支承面上的摩擦力u摩擦防松：鎖緊螺母、彈簧墊圈、自鎖螺母u機(jī)械防松：開(kāi)口銷(xiāo)與槽形螺母、止動(dòng)墊圈u鉚沖防松：端鉚、沖點(diǎn)第18頁(yè)/共46頁(yè)詞 匯 二、詞匯screw 螺釘、螺紋 bolt 螺栓 nut 螺母 stud bolt 雙頭螺栓 washer 墊圈 thread 螺紋機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and

25、joints 第19頁(yè)/共46頁(yè)課文分析機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints Typical methods of fastening and joining parts include the use of such items as bolts, nuts, cap screws, setscrews, rivets, locking devices and keys. Parts may also be joined by welding, brazing, or clipping together. Studies in engi

26、neering graphics and in metal processes often include instruction on various joining methods, and the curiosity of any person interested in engineering naturally results in acquisition of a good background of fastening methods. 第20頁(yè)/共46頁(yè)Typical methods of fastening and joining parts include the use

27、of such items as bolts, nuts, cap screws, setscrews, rivets, locking devices and keys.課文分析典型的緊固件和聯(lián)接件包括諸如螺栓、螺帽、有頭螺釘、緊定螺釘、鉚釘、鎖緊裝置和鍵。 Parts may also be joined by welding, brazing, or clipping together. 零件聯(lián)接也可以用熔焊、銅焊和夾緊的方法。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第21頁(yè)/共46頁(yè)Studies in engineering g

28、raphics and in metal processes often include instruction on various joining methods, and the curiosity of any person interested in engineering naturally results in acquisition of a good background of fastening methods. 課文分析在工程圖和金屬加工工藝研究中常常包括關(guān)于各種聯(lián)接方法的說(shuō)明，在工程上對(duì)此很感興趣的，求知欲強(qiáng)的任何人自然會(huì)獲得關(guān)于固緊方法上良好的基礎(chǔ)知識(shí)。 機(jī)械工程專(zhuān)業(yè)

29、英語(yǔ)Lesson 19 Screws, fasteners and joints 第22頁(yè)/共46頁(yè)課文分析機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints If an uninformed person were asked to choose the dullest and most uninteresting subject in mechanical design that he could imagine, he might well choose the subject of fasteners, that is, nuts and bo

30、lts. In fact, the term “nuts and bolts” is synonymous with hard and monotonous work, necessary but totally uninteresting tasks. Could one seriously imagine a group of nut and bolt manufacturers organizing an association and getting together for annual meeting? What subject could possibly be of any i

31、nterest? 第23頁(yè)/共46頁(yè)If an uninformed person were asked to choose the dullest and most uninteresting subject in mechanical design that he could imagine, he might well choose the subject of fasteners, that is, nuts and bolts. 課文分析如果讓一個(gè)對(duì)緊固件不甚了解的人去選擇他能想象的機(jī)械設(shè)計(jì)方面最枯燥無(wú)味的學(xué)科的話(huà)，那么他就會(huì)選擇緊固件學(xué)科，即螺栓和螺帽。 In fact, the

32、term “nuts and bolts” is synonymous with hard and monotonous work, necessary but totally uninteresting tasks. 事實(shí)上，術(shù)語(yǔ)“螺栓和螺帽”是與艱苦、單調(diào)的工作同義，乏味但必須的工作。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第24頁(yè)/共46頁(yè)Could one seriously imagine a group of nut and bolt manufacturers organizing an association and ge

33、tting together for annual meeting? What subject could possibly be of any interest? 課文分析可以認(rèn)真地設(shè)想有一群螺栓螺帽制造者組成一個(gè)協(xié)會(huì)并在一起召開(kāi)年會(huì)嗎？那么還有什么學(xué)科不能讓人感興趣呢？ In spite of this taint, the subject is one of the most interesting in the entire field of mechanical design. 盡管存在這一偏見(jiàn)，但是這一學(xué)科在機(jī)械設(shè)計(jì)整個(gè)領(lǐng)域中卻是最使人感興趣的學(xué)科之一。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesso

34、n 19 Screws, fasteners and joints 第25頁(yè)/共46頁(yè)The number of new inventions in the fastener field over any period you might care to mention has been tremendous. 課文分析在緊固件領(lǐng)域新發(fā)明的數(shù)目巨大超過(guò)你能注意到的任何時(shí)期There is an overwhelming variety of fasteners available for the designers selection. 數(shù)不勝數(shù)的緊固件可供設(shè)計(jì)者任意選擇使用。 機(jī)械工程專(zhuān)業(yè)英

35、語(yǔ)Lesson 19 Screws, fasteners and joints 第26頁(yè)/共46頁(yè)Another thing: did you know that a good bolt material should be strong and tough, but a good nut material should be soft and ductile? 課文分析還有，你知道嗎？好的螺栓的材料應(yīng)該是堅(jiān)固而有韌性，而好的螺帽的材料應(yīng)該是軟而有塑性的。 Or did you know that there are certain applications where you should

36、tighten the bolt as tightly as possible and, if it does not fail by twisting the bolt in two during tightening, there is a very good possibility that the bolt never will fail? 或者你知道嗎?在某些應(yīng)用中你應(yīng)該盡可能地把它們旋緊，如果在上緊過(guò)程中，由于旋緊這螺栓過(guò)程中而未發(fā)生失效現(xiàn)象，那么螺栓將可能永遠(yuǎn)不會(huì)失效。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第27頁(yè)/共46

37、頁(yè)In the material to follow you will discover the why of these questions. You will learn why a nut or bolt loosens and what you must do to keep it tight. 課文分析在下面的文字中你將發(fā)現(xiàn)這些問(wèn)題的原因。你將掌握螺栓、螺帽為什么會(huì)松動(dòng)和你必須怎樣令它保持旋緊狀態(tài)。 Methods of joining parts are extremely important in the engineering of a quality design, and

38、it is necessary to have a thorough understanding of the performance of fasteners and joints under all conditions of use and design. 聯(lián)接件的聯(lián)接方法在保證工程設(shè)計(jì)質(zhì)量方面是極端重要的。在設(shè)計(jì)和使用的各種情況下，充分了解緊固件和聯(lián)接件的性能那是必要的。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第28頁(yè)/共46頁(yè)Jumbo jets such as Boeings 747 and Lockheeds 1011 re

39、quire as many as 2.5 million fasteners, some of which cost several dollars apiece. 課文分析大型噴氣發(fā)動(dòng)機(jī)客機(jī)像被音747和洛克希德1011，需要250萬(wàn)個(gè)緊固件，有些每個(gè)要花數(shù)美元。 The 747, for example, needs about 70,000 titanium fasteners, costing about $150,000 in all; 400,000 other close-tolerance fasteners, costing about $250,000; and 30,00

40、0 squeeze rivets priced at 50 cents each, installed. 例如波音747，大約需要裝70000個(gè)鈦合金緊固件，全部大約要花150000美元；400000個(gè)具有精密公差的其他緊固件，大約要花250000美元；和30000個(gè)擠壓用鉚釘，安裝后每個(gè)價(jià)值50美分。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第29頁(yè)/共46頁(yè)To keep cost down, Boeing, Lockheed, and their subcontractors constantly review new fastene

41、r designs, installation techniques, and tooling. 課文分析為了降低成本，波音、洛克希德和他們的承包商不斷重新審查緊固件的設(shè)計(jì)、安裝和切削加工。 Cost-saving designs and tooling will find a ready market, which will grow in value as jumbo jets proliferate. 節(jié)省的設(shè)計(jì)和加工成本將開(kāi)發(fā)一個(gè)暢銷(xiāo)市場(chǎng)，增長(zhǎng)的價(jià)值那將像坐上噴氣式飛機(jī)一樣。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints pru5lifr

42、eitvi. 激增; 繁殖; 增生第30頁(yè)/共46頁(yè)Fasteners are named according to how they are intended to be used rather than how they are actually employed in specific instances. 課文分析緊固件是根據(jù)將如何使用他們來(lái)命名的，而不是根據(jù)其在具體例子中的實(shí)際應(yīng)用命名的。 If this basic fact is remembered, it will not be difficult to distinguish between a screw and a bo

43、lt. 如果記住了這個(gè)基本事實(shí)，就將不難區(qū)別螺釘和螺栓。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第31頁(yè)/共46頁(yè)If a product is designed so that its primary purpose is assembly into a tapped hole, it is a screw. Thus a screw is tightened by exerting torque on the head. If a product is designed so that it is intended to be use

44、d with a nut, it is a bolt. 課文分析如果所設(shè)計(jì)的產(chǎn)品其主要目的是把它裝入到已攻絲的螺紋孔中，那就是螺釘。這樣螺釘是要在螺釘頭上施加扭矩來(lái)旋緊的。如果所設(shè)計(jì)的產(chǎn)品打算跟螺母配合使用，那就是螺栓。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第32頁(yè)/共46頁(yè)A bolt is tightened by exerting torque on the nut. A stud resembles a threaded rod; one end assembles into a tapped hole, the other e

45、nd receives a nut. 課文分析螺栓是靠在螺母上施加扭矩來(lái)旋緊的。雙頭螺栓就像刻了螺紋的桿，一端旋入螺紋孔中，另一端再裝上螺帽。It is the intent, rather than the actual use, which determines the name of a product. 因而根據(jù)使用的目的來(lái)確定產(chǎn)品名稱(chēng)，并不是根據(jù)其實(shí)際使用來(lái)命名的。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第33頁(yè)/共46頁(yè)Thus it may be desirable on various occasions to use a

46、 drill to drill a hole through two sheets of steel, say, and joint them using a screw and a nut. 課文分析這樣，在各種場(chǎng)合用鉆頭給兩塊鋼板鉆通孔，人們就會(huì)用螺栓和螺帽來(lái)連接它們，這可能是人們所希望的。 There are four forms of head most commonly used with cap screw: hexagon head, fillister head, flat head and hexagon socket head. 有帽螺釘最常用的四種螺釘頭的形式是：六角頭，

47、槽頭，平頭和內(nèi)六角沉頭。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第34頁(yè)/共46頁(yè)When a connection is desired which can be disassembled without destructing the parts assembled and which is strong enough to resist both external tensile load and shear load, or a combination of these, then the simple bolted joint

48、using hardened washers is a good solution. 課文分析當(dāng)需要一個(gè)螺紋聯(lián)接即可以拆開(kāi)又不破壞被聯(lián)接件，而且這個(gè)聯(lián)接又要有足夠的強(qiáng)度以承受外拉力和剪力或這兩種力的合力時(shí)，使用帶淬火墊圈的簡(jiǎn)單螺栓聯(lián)接是一個(gè)很好的解決方法。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第35頁(yè)/共46頁(yè)In such a joint the bolt has first been tightened to produce an initial tensile preload, after which the external t

49、ensile load and the external shear load are applied. 課文分析在這種螺紋聯(lián)接中，首先把螺栓上緊以產(chǎn)生一預(yù)緊載荷初拉力，而后施加外拉力載荷和剪切載荷。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第36頁(yè)/共46頁(yè)The effect of the preload is to place the parts in compression for better resistance to the external tensile load and to create friction betwee

50、n the parts to resist the shear load. 課文分析預(yù)載荷的作用是使被連接件處于壓應(yīng)力狀態(tài)以更好地抵抗外部拉伸載荷和產(chǎn)生摩擦力以抵抗剪切載荷。The importance of preloading of bolts cannot be overestimated. A high preload improves both the fatigue resistance of a bolted connection and the locking effect. 螺栓預(yù)加載荷的重要性不能被過(guò)高地估計(jì)。較高預(yù)載荷即提高螺栓聯(lián)接的抗疲勞能力又改善鎖緊作用。 機(jī)械工程專(zhuān)

51、業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第37頁(yè)/共46頁(yè)Having learned that a high preload is very desirable in important bolted connections, we must next consider means of assuring that the preload is actually developed when the parts are assembled. 課文分析已經(jīng)知道：高預(yù)載荷在重要的螺栓聯(lián)接中是非常希望的。下一步我們要考慮的是，當(dāng)要裝配零件時(shí)，如何確保設(shè)計(jì)

52、情況下該預(yù)載荷的產(chǎn)生。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第38頁(yè)/共46頁(yè)If the overall length L of a bolt with cross area A can actually be measured with a micrometer when it is assembled, the bolt elongation d due to the preload F can be computed using the formula d=FL/AE, where E is the modulus of ela

53、sticity of the bolt material. 課文分析如果橫截面積為A、總長(zhǎng)度為L(zhǎng)的螺栓裝配時(shí)，實(shí)際上是可以用千分尺來(lái)測(cè)量的，由于預(yù)載力F的作用而使螺栓伸長(zhǎng)量為d，d可以利用公式dFLAE來(lái)計(jì)算，式中E是螺栓材料的彈性模量。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第39頁(yè)/共46頁(yè)Then simply tighten the nut until the bolt elongation through the distance d. This assures that the desired preload has been

54、 attained. 課文分析那么只要旋緊螺母直至使螺栓伸長(zhǎng)達(dá)到d。這就保證了已經(jīng)達(dá)到了所希望的預(yù)緊載荷。 However, the elongation of a screw cannot usually be measured because the threaded end may be in a blind hole. 然而，螺釘?shù)纳扉L(zhǎng)量通常是不能測(cè)量的，因?yàn)槁葆敹瞬靠赡苁窃诿た變?nèi)。 機(jī)械工程專(zhuān)業(yè)英語(yǔ)Lesson 19 Screws, fasteners and joints 第40頁(yè)/共46頁(yè)It is also impractical in many cases to measure bolt elongation. In such cases the wrench torque required to develop the specified preload must be e