机械工程专业英语PPT学习教案

1、会计学1机械工程专业英语机械工程专业英语机械工程专业英语机械工程专业英语预备知识预备知识 一、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 o

2、f screw threads.There are two main 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 joi

3、ned parts see no relative motion). 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 n

4、uts).第1页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Bolted joint Screw joint Stud joint 第2页/共46页Bolt The bolt assembly is used when joint parts are not too thick to drill through holes.螺栓螺栓 用于联接二通孔薄件用于联接二通孔薄件第3页/共46页 Stud Stud are used in situations

5、 where a part with a through hole and a part with blind tapped hole.双头螺柱双头螺柱 用于联接一通孔薄件和一盲孔厚件。用于联接一通孔薄件和一盲孔厚件。第4页/共46页Screw Screws are mostly used for the cases with small bearing forces. such as inspection covers which have to be removed frequently.螺钉螺钉 多用于用于受力不大需要经常拆卸的情况多用于用于受力不大需要经常拆卸的情况第5页/共46页Nu

6、t are used to match the other screw fasteners. 螺母螺母 与其他螺纹件配合使用与其他螺纹件配合使用第6页/共46页Washer are used to match the other screw fasteners. 垫圈垫圈 与其他螺纹件配合使用与其他螺纹件配合使用第7页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Theory The clamp load, also called preload, o

7、f a cap screw is created when a torque is applied, and is generally a percentage of the cap screws proof strength. Cap screws are manufactured to various standards that define, among other things, their strength and clamp load. Torque charts are available that identify the required torque for cap sc

8、rews based on their property class or grade. When a cap screw is tightened it is stretched, and the parts that are captured are compressed. 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页/共46页机械工程专业英语机械工程专

9、业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Theory The result is a non-intuitive distribution of strain; in this engineering 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 mo

10、del 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 small fraction of the external load prior to it exceeding the clamp load, depending on the compressed parts stiffness with respect to the hardwares sti

11、ffness. 第9页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Theory The results of this type of joint design are: Greater preloads in bolted joints reduce the fatigue loading of the hardware. For cyclic loads, the bolt does not see the full amplitude of t

12、he 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 hardware doesnt see any motion and will not come loose (no locking mechanisms are required). In the cas

13、e 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10页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints 第

14、11页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Theory The results of this type of joint design are: Greater 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.

15、 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 hardware doesnt see any motion and will not come loose (no locking mechanisms are required). In the case of the

16、 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12页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Thread st

17、rength 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 steel threads requires a depth of 1.5 thread diameter to support the full clamp load. If an a

18、ppropriate 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页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Failure modes The most commo

19、n 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 threads and deforming the hardware, the failure might not occur until long after

20、ward. 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 and failure of the joint. Corrosion, embedment and exceeding the shear stress li

21、mit are other modes of failure.第14页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background informationLesson 19 Screws, fasteners and joints Notes:Brinelling refers to a material surface failure caused by contact stress that exceeds the material limit. This failure is caused by just one application of a load g

22、reat 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 failure by fatigue as described below, and is of particular concern w

23、hen considering the design of critical fastener joints.第15页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、预备知识一、预备知识Lesson 19 Screws, fasteners and joints 1、基本类型、基本类型u普通螺栓联接：被联接件上通孔和螺栓杆间留有间隙，故普通螺栓联接：被联接件上通孔和螺栓杆间留有间隙，故精度低、结构简单。精度低、结构简单。u铰制孔用螺栓联接：孔和螺栓杆多采用基孔制过渡配合（铰制孔用螺栓联接：孔和螺栓杆多采用基孔制过渡配合（H7/m6、H7/n6）,精确固定被联接件的相对位置，并可

24、承受精确固定被联接件的相对位置，并可承受横向载荷。横向载荷。u双头螺栓联接：被联接件之一太厚或经常拆装双头螺栓联接：被联接件之一太厚或经常拆装u螺钉联接：不用螺母，比双头螺柱简单，用途相似，多用螺钉联接：不用螺母，比双头螺柱简单，用途相似，多用于受力不大、不需经常拆装的场合于受力不大、不需经常拆装的场合u紧定螺钉联接：固定两零件的相对位置，可传递不太大的紧定螺钉联接：固定两零件的相对位置，可传递不太大的扭矩和力扭矩和力u螺栓的类型：六角头螺栓和双头螺栓螺栓的类型：六角头螺栓和双头螺栓u螺钉的类型：半圆头、平头、六角头、圆柱头、沉头螺钉的类型：半圆头、平头、六角头、圆柱头、沉头 第16页/共46

25、页机械工程专业英语机械工程专业英语预备知识预备知识 一、预备知识一、预备知识Lesson 19 Screws, fasteners and joints 2、螺纹的预紧、螺纹的预紧u预紧的目的：增强联接的可靠性、紧密性，防止预紧的目的：增强联接的可靠性、紧密性，防止受载后被联接件间出现缝隙或发生相对滑移。选用受载后被联接件间出现缝隙或发生相对滑移。选用较大的预紧力可提高联接的可靠性和疲劳强度较大的预紧力可提高联接的可靠性和疲劳强度u预紧应力不超过其材料的屈服极限的预紧应力不超过其材料的屈服极限的80%。u控制预紧力的方法：控制预紧力的方法： 1）借助测力矩扳手或定力矩扳手）借助测力矩扳手或定力

26、矩扳手 2）测定螺栓伸长量）测定螺栓伸长量第17页/共46页机械工程专业英语机械工程专业英语预备知识预备知识 一、预备知识一、预备知识Lesson 19 Screws, fasteners and joints 3、螺纹的防松、螺纹的防松u螺纹升角小于螺旋副的当量摩擦角螺纹升角小于螺旋副的当量摩擦角 ：自锁性好：自锁性好u螺母与螺栓头部等支承面上的摩擦力螺母与螺栓头部等支承面上的摩擦力u摩擦防松：锁紧螺母、弹簧垫圈、自锁螺母摩擦防松：锁紧螺母、弹簧垫圈、自锁螺母u机械防松：开口销与槽形螺母、止动垫圈机械防松：开口销与槽形螺母、止动垫圈u铆冲防松：端铆、冲点铆冲防松：端铆、冲点第18页/共46页

27、词词 汇汇 二、词汇二、词汇screw 螺钉、螺纹螺钉、螺纹 bolt 螺栓螺栓 nut 螺母螺母 stud bolt 双头螺栓双头螺栓 washer 垫圈垫圈 thread 螺纹螺纹机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第19页/共46页课文分析课文分析机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints Typical methods of fastening and joining parts include the use of such items as b

28、olts, nuts, cap screws, setscrews, rivets, locking devices and keys. Parts may also be joined by welding, brazing, or clipping together. Studies in engineering graphics and in metal processes often include instruction on various joining methods, and the curiosity of any person interested in engineer

29、ing naturally results in acquisition of a good background of fastening methods. 第20页/共46页Typical methods of fastening and joining parts include the use of such items as bolts, nuts, cap screws, setscrews, rivets, locking devices and keys.课文分析课文分析典型的紧固件和联接件包括诸如螺栓、螺帽、有头典型的紧固件和联接件包括诸如螺栓、螺帽、有头螺钉、紧定螺钉、铆钉

30、、锁紧装置和键。螺钉、紧定螺钉、铆钉、锁紧装置和键。 Parts may also be joined by welding, brazing, or clipping together. 零件联接也可以用熔焊、铜焊和夹紧的方法。零件联接也可以用熔焊、铜焊和夹紧的方法。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第21页/共46页Studies in engineering graphics and in metal processes often include instruction on various joining

31、methods, and the curiosity of any person interested in engineering naturally results in acquisition of a good background of fastening methods. 课文分析课文分析在工程图和金属加工工艺研究中常常包括关于各种在工程图和金属加工工艺研究中常常包括关于各种联接方法的说明，在工程上对此很感兴趣的，求知联接方法的说明，在工程上对此很感兴趣的，求知欲强的任何人自然会获得关于固紧方法上良好的基欲强的任何人自然会获得关于固紧方法上良好的基础知识。础知识。 机械工程专业英语

32、机械工程专业英语Lesson 19 Screws, fasteners and joints 第22页/共46页课文分析课文分析机械工程专业英语机械工程专业英语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, th

33、at is, nuts and bolts. 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 po

34、ssibly be of any interest? 第23页/共46页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. 课文分析课文分析如果让一个对紧固件不甚了解的人去选择他能想象如果让一个对紧固件不甚了解的人去选择他能想象的机械设计方面最

35、枯燥无味的学科的话，那么他就的机械设计方面最枯燥无味的学科的话，那么他就会选择紧固件学科，即螺栓和螺帽。会选择紧固件学科，即螺栓和螺帽。 In fact, the term “nuts and bolts” is synonymous with hard and monotonous work, necessary but totally uninteresting tasks. 事实上，术语事实上，术语“螺栓和螺帽螺栓和螺帽”是与艰苦、单是与艰苦、单调的工作同义，乏味但必须的工作。调的工作同义，乏味但必须的工作。 机械工程专业英语机械工程专业英语Lesson 19 Screws, faste

36、ners and joints 第24页/共46页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 interest? 课文分析课文分析可以认真地设想有一群螺栓螺帽制造者组成一个协可以认真地设想有一群螺栓螺帽制造者组成一个协会并在一起召开年会吗？那么还有什么学科不能让会并在一起召开年会吗？那么还有什么学科不

37、能让人感兴趣呢？人感兴趣呢？ In spite of this taint, the subject is one of the most interesting in the entire field of mechanical design. 尽管存在这一偏见，但是这一学科在机械设计整尽管存在这一偏见，但是这一学科在机械设计整个领域中却是最使人感兴趣的学科之一。个领域中却是最使人感兴趣的学科之一。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第25页/共46页The number of new inventions in t

38、he fastener field over any period you might care to mention has been tremendous. 课文分析课文分析在紧固件领域新发明的数目巨大超过你能注意到的在紧固件领域新发明的数目巨大超过你能注意到的任何时期任何时期There is an overwhelming variety of fasteners available for the designers selection. 数不胜数的紧固件可供设计者任意选择使用。数不胜数的紧固件可供设计者任意选择使用。 机械工程专业英语机械工程专业英语Lesson 19 Screws,

39、 fasteners and joints 第26页/共46页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? 课文分析课文分析还有，你知道吗？好的螺栓的材料应该是坚固而有还有，你知道吗？好的螺栓的材料应该是坚固而有韧性，而好的螺帽的材料应该是软而有塑性的。韧性，而好的螺帽的材料应该是软而有塑性的。 Or did you know that there are certain a

40、pplications where you should 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? 或者你知道吗或者你知道吗?在某些应用中你应该尽可能地把它们在某些应用中你应该尽可能地把它们旋紧，如果在上紧过程中，由于旋紧这螺栓过程中旋紧，如果在上紧过程中，由于旋紧这螺栓过程中而未发生失效

41、现象，那么螺栓将可能永远不会失效。而未发生失效现象，那么螺栓将可能永远不会失效。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第27页/共46页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. 课文分析课文分析在下面的文字中你将发现这些问题的原因。你将掌在下面的文字中你将发现这些

42、问题的原因。你将掌握螺栓、螺帽为什么会松动和你必须怎样令它保持握螺栓、螺帽为什么会松动和你必须怎样令它保持旋紧状态。旋紧状态。 Methods of joining parts are extremely important in the engineering of a quality design, and it is necessary to have a thorough understanding of the performance of fasteners and joints under all conditions of use and design. 联接件的联接方法在保证

43、工程设计质量方面是极端联接件的联接方法在保证工程设计质量方面是极端重要的。在设计和使用的各种情况下，充分了解紧重要的。在设计和使用的各种情况下，充分了解紧固件和联接件的性能那是必要的。固件和联接件的性能那是必要的。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第28页/共46页Jumbo jets such as Boeings 747 and Lockheeds 1011 require as many as 2.5 million fasteners, some of which cost several dollars a

44、piece. 课文分析课文分析大型喷气发动机客机像被音大型喷气发动机客机像被音747和洛克希德和洛克希德1011，需要需要250万个紧固件，有些每个要花数美元。万个紧固件，有些每个要花数美元。 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 30,000 squeeze rivets priced at 50 cents e

45、ach, installed. 例如波音例如波音747，大约需要装，大约需要装70000个钛合金紧固件，个钛合金紧固件，全部大约要花全部大约要花150000美元；美元；400000个具有精密公差个具有精密公差的其他紧固件，大约要花的其他紧固件，大约要花250000美元；和美元；和30000个个挤压用铆钉，安装后每个价值挤压用铆钉，安装后每个价值50美分。美分。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第29页/共46页To keep cost down, Boeing, Lockheed, and their subcont

46、ractors constantly review new fastener designs, installation techniques, and tooling. 课文分析课文分析为了降低成本，波音、洛克希德和他们的承包商为了降低成本，波音、洛克希德和他们的承包商不断重新审查紧固件的设计、安装和切削加工。不断重新审查紧固件的设计、安装和切削加工。 Cost-saving designs and tooling will find a ready market, which will grow in value as jumbo jets proliferate. 节省的设计和加工成本将

47、开发一个畅销市场，增长节省的设计和加工成本将开发一个畅销市场，增长的价值那将像坐上喷气式飞机一样。的价值那将像坐上喷气式飞机一样。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints pru5lifreitvi. 激增激增; 繁殖繁殖; 增增生生第30页/共46页Fasteners are named according to how they are intended to be used rather than how they are actually employed in specific instances. 课文分析课文分

48、析紧固件是根据将如何使用他们来命名的，而不是紧固件是根据将如何使用他们来命名的，而不是根据其在具体例子中的实际应用命名的。根据其在具体例子中的实际应用命名的。 If this basic fact is remembered, it will not be difficult to distinguish between a screw and a bolt. 如果记住了这个基本事实，就将不难区别螺钉和螺如果记住了这个基本事实，就将不难区别螺钉和螺栓。栓。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第31页/共46页If a

49、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 used with a nut, it is a bolt. 课文分析课文分析如果所设计的产品其主要目的是把它装入到已攻如果所设计的产品其主要目的是把它装入到已攻丝的螺纹孔中，那就是螺钉

50、。这样螺钉是要在螺丝的螺纹孔中，那就是螺钉。这样螺钉是要在螺钉头上施加扭矩来旋紧的。如果所设计的产品打钉头上施加扭矩来旋紧的。如果所设计的产品打算跟螺母配合使用，那就是螺栓。算跟螺母配合使用，那就是螺栓。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第32页/共46页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

51、nd receives a nut. 课文分析课文分析螺栓是靠在螺母上施加扭矩来旋紧的。双头螺栓螺栓是靠在螺母上施加扭矩来旋紧的。双头螺栓就像刻了螺纹的杆，一端旋入螺纹孔中，另一端就像刻了螺纹的杆，一端旋入螺纹孔中，另一端再装上螺帽。再装上螺帽。It is the intent, rather than the actual use, which determines the name of a product. 因而根据使用的目的来确定产品名称，并不是根据因而根据使用的目的来确定产品名称，并不是根据其实际使用来命名的。其实际使用来命名的。 机械工程专业英语机械工程专业英语Lesson 19

52、Screws, fasteners and joints 第33页/共46页Thus it may be desirable on various occasions to use a drill to drill a hole through two sheets of steel, say, and joint them using a screw and a nut. 课文分析课文分析这样，在各种场合用钻头给两块钢板钻通孔，人这样，在各种场合用钻头给两块钢板钻通孔，人们就会用螺栓和螺帽来连接它们，这可能是人们们就会用螺栓和螺帽来连接它们，这可能是人们所希望的。所希望的。 There ar

53、e four forms of head most commonly used with cap screw: hexagon head, fillister head, flat head and hexagon socket head. 有帽螺钉最常用的四种螺钉头的形式是：六角头，有帽螺钉最常用的四种螺钉头的形式是：六角头，槽头，平头和内六角沉头。槽头，平头和内六角沉头。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第34页/共46页When a connection is desired which can be disa

54、ssembled 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 using hardened washers is a good solution. 课文分析课文分析当需要一个螺纹联接即可以拆开又不破坏被联接当需要一个螺纹联接即可以拆开又不破坏被联接件，而且这个联接又要有足够的强度以承受外拉件

55、，而且这个联接又要有足够的强度以承受外拉力和剪力或这两种力的合力时，使用带淬火垫圈力和剪力或这两种力的合力时，使用带淬火垫圈的简单螺栓联接是一个很好的解决方法。的简单螺栓联接是一个很好的解决方法。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第35页/共46页In such a joint the bolt has first been tightened to produce an initial tensile preload, after which the external tensile load and the ex

56、ternal shear load are applied. 课文分析课文分析在这种螺纹联接中，首先把螺栓上紧以产生一预在这种螺纹联接中，首先把螺栓上紧以产生一预紧载荷初拉力，而后施加外拉力载荷和剪切载荷。紧载荷初拉力，而后施加外拉力载荷和剪切载荷。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第36页/共46页The effect of the preload is to place the parts in compression for better resistance to the external tensile l

57、oad and to create friction between the parts to resist the shear load. 课文分析课文分析预载荷的作用是使被连接件处于压应力状态以更预载荷的作用是使被连接件处于压应力状态以更好地抵抗外部拉伸载荷和产生摩擦力以抵抗剪切好地抵抗外部拉伸载荷和产生摩擦力以抵抗剪切载荷。载荷。The importance of preloading of bolts cannot be overestimated. A high preload improves both the fatigue resistance of a bolted conn

58、ection and the locking effect. 螺栓预加载荷的重要性不能被过高地估计。较高预螺栓预加载荷的重要性不能被过高地估计。较高预载荷即提高螺栓联接的抗疲劳能力又改善锁紧作用。载荷即提高螺栓联接的抗疲劳能力又改善锁紧作用。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第37页/共46页Having learned that a high preload is very desirable in important bolted connections, we must next consider means

59、of assuring that the preload is actually developed when the parts are assembled. 课文分析课文分析已经知道：高预载荷在重要的螺栓联接中是非常已经知道：高预载荷在重要的螺栓联接中是非常希望的。下一步我们要考虑的是，当要装配零件希望的。下一步我们要考虑的是，当要装配零件时，如何确保设计情况下该预载荷的产生。时，如何确保设计情况下该预载荷的产生。 机械工程专业英语机械工程专业英语Lesson 19 Screws, fasteners and joints 第38页/共46页If the overall length L

60、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 elasticity of the bolt material. 课文分析课文分析如果横截面积为如果横截面积为A、总长度为、总长度为L的螺栓装配时，实的螺栓装配时，实际上是可以用千分尺来测量