机械工程专业英语课件L.ppt

English for Mechanical Engineering,机械工程专业英语,常州工学院机电工程学院徐红丽,Slotted cone pointed set screw.Hex nut.Slotted nut.Bright washer.Spring washer.Tab washer 锥端紧定螺钉 六角螺母 六角槽形螺母 平垫圈 弹簧垫圈 外舌止动垫圈,Hexagon head bolt.Stud.Slotted cheese head screw.Slotted pan head screw.Slotted countersunk screw.Hexagon socket cap 六角头螺钉 双头螺柱头 圆柱头螺钉 盘头螺钉 沉头螺钉 圆柱头内六角螺钉,Types of screw fasteners 螺纹紧固件的种类,Parts with threads used for joining and fastening are called screw fasteners.The most widely used components as screw fasteners are bolts,double screw bolts-stud,screws,nuts and washers。用螺纹联接并起紧固作用的零件称为螺纹紧固件。常用的螺纹紧固件有螺栓、双头螺柱、螺钉、螺母、垫圈等。,Lesson 19 Screws,fasteners and joints,机械工程专业英语,机械工程专业英语,预备知识,一、Background information,Lesson 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 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).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).,机械工程专业英语,预备知识,一、Background information,Lesson 19 Screws,fasteners and joints,Bolted joint,Screw joint,Stud joint,Bolt 螺 栓,The bolt assembly is used when joint parts are not too thick to drill through holes.螺栓 用于联接二通孔薄件,Stud 双头螺柱,Stud are used in situations where a part with a through hole and a part with blind tapped hole.双头螺柱 用于联接一通孔薄件和一盲孔厚件。,Screw 螺 钉,Screws are mostly used for the cases with small bearing forces.such as inspection covers which have to be removed frequently.螺钉 多用于用于受力不大需要经常拆卸的情况,Nut 螺 母,Nut are used to match the other screw fasteners.螺母 与其他螺纹件配合使用,Washer 垫 圈,弹簧垫圈 平垫圈,Washer are used to match the other screw fasteners.垫圈 与其他螺纹件配合使用,机械工程专业英语,预备知识,一、Background information,Lesson 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 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 screws 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.,机械工程专业英语,预备知识,一、Background information,Lesson 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 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 small fraction of the external load prior to it exceeding the clamp load,depending on the compressed parts stiffness with respect to the hardwares stiffness.,机械工程专业英语,预备知识,一、Background information,Lesson 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.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 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.,机械工程专业英语,预备知识,一、Background information,Lesson 19 Screws,fasteners and joints,机械工程专业英语,预备知识,一、Background information,Lesson 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.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 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.,机械工程专业英语,预备知识,一、Background information,Lesson 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 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.,机械工程专业英语,预备知识,一、Background information,Lesson 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 threads 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 and failure of the joint.Corrosion,embedment and exceeding the shear stress limit are other modes of failure.,机械工程专业英语,预备知识,一、Background information,Lesson 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 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 failure by fatigue as described below,and is of particular concern when considering the design of critical fastener joints.,机械工程专业英语,预备知识,一、预备知识,Lesson 19 Screws,fasteners and joints,1、基本类型普通螺栓联接：被联接件上通孔和螺栓杆间留有间隙，故精度低、结构简单。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，并可承受横向载荷。双头螺栓联接：被联接件之一太厚或经常拆装螺钉联接：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螺栓的类型：六角头螺栓和双头螺栓螺钉的类型：半圆头、平头、六角头、圆柱头、沉头,机械工程专业英语,预备知识,一、预备知识,Lesson 19 Screws,fasteners and joints,2、螺纹的预紧预紧的目的：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。选用较大的预紧力可提高联接的可靠性和疲劳强度预紧应力不超过其材料的屈服极限的80%。控制预紧力的方法：1）借助测力矩扳手或定力矩扳手 2）测定螺栓伸长量,机械工程专业英语,预备知识,一、预备知识,Lesson 19 Screws,fasteners and joints,3、螺纹的防松螺纹升角小于螺旋副的当量摩擦角：自锁性好螺母与螺栓头部等支承面上的摩擦力摩擦防松：锁紧螺母、弹簧垫圈、自锁螺母机械防松：开口销与槽形螺母、止动垫圈铆冲防松：端铆、冲点,词 汇,二、词汇,screw 螺钉、螺纹 bolt 螺栓 nut 螺母 stud bolt 双头螺栓 washer 垫圈 thread 螺纹,机械工程专业英语,Lesson 19 Screws,fasteners and joints,课文分析,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 bolts,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 engineering naturally results in acquisition of a good background of fastening methods.,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,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、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。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,Studies in engineering 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.,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础知识。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,课文分析,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,that 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 possibly be of any interest?,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,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。,In fact,the term“nuts and bolts”is synonymous with hard and monotonous work,necessary but totally uninteresting tasks.,事实上，术语“螺栓和螺帽”是与艰苦、单调的工作同义，乏味但必须的工作。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,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,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,Lesson 19 Screws,fasteners and joints,The number of new inventions in the fastener field over any period you might care to mention has been tremendous.,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。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,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,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。,Or did you know that there are certain applications 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?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,Lesson 19 Screws,fasteners and joints,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,在下面的文字中你将发现这些问题的原因。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，充分了解紧固件和联接件的性能那是必要的。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,Jumbo jets such as Boeings 747 and Lockheeds 1011 require as many as 2.5 million fasteners,some of which cost several dollars apiece.,课文分析,大型喷气发动机客机像被音747和洛克希德1011，需要250万个紧固件，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 each,installed.,例如波音747，大约需要装70000个钛合金紧固件，全部大约要花150000美元；400000个具有精密公差的其他紧固件，大约要花250000美元；和30000个挤压用铆钉，安装后每个价值50美分。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,To keep cost down,Boeing,Lockheed,and their subcontractors constantly review new fastener designs,installation techniques,and tooling.,课文分析,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。,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。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,pru5lifreitvi.激增;繁殖;增生,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,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。,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栓。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,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 used with a nut,it is a bolt.,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算跟螺母配合使用，那就是螺栓。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,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 end receives a nut.,课文分析,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，并不是根据其实际使用来命名的。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,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,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。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,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 using hardened washers is a good solution.,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件，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,Lesson 19 Screws,fasteners and joints,In such a joint the bolt has first been tightened to produce an initial tensile preload,after which the external tensile load and the external shear load are applied.,课文分析,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。,机械工程专业英语,Lesson 19 Screws,fasteners and joints,The effect of the preload is to place the parts in compression for better resistance to the external tensile load and to create friction between the parts to resist the shear load.,课文分析,预载荷的作用是使被连接