武科大机械专业英语Lesson4.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Lesson 4 Shafts and Couplings,Terminology,Text tour,1/24/2026,1,机械工程专业英语教程,Terminology,1/24/2026,2,机械工程专业英语教程,Coupling,A coupling is a device for connecting the ends of adjacent,shafts,.,联轴器：联轴器是用来把相邻的两个轴的轴端联接起来的装置,机械工程专业英语教程,1/24/2026,Socket wrench,A,wrench,with a usually interchangeable socket to fit over a,nut,or,bolt,3,套筒扳手：通常带有可替换套筒以适于螺帽或螺栓的扳手,机械工程专业英语教程,1/24/2026,Keyway,A slot for a,key,in the,hub,or,shaft,of a wheel,键槽：轮毂里或轴上装键的沟槽,Bolt,螺栓,螺杆,4,机械工程专业英语教程,1/24/2026,screw:,螺钉,Screw driver:,螺丝刀,socket:,插座，插口，套筒扳手,wrench:,扳手，拧，扳紧，扭转,5,机械工程专业英语教程,1/24/2026,stem:,杆，棒，柄，柱，轴,clutch:,抓住，捏紧，离合器,Cold-roll:,冷轧，冷轧机,forge:,锻造，打制，锻工车间,key:,键,Keyway:,键槽，销座,6,机械工程专业英语教程,1/24/2026,propeller:,螺旋桨，推进器,flange:,凸缘，法兰盘,hub:,衬套，轮毂,Flexible coupling:,弹性联轴器，挠性联轴器,7,Virtually,（,in fact,）,all machines contain shafts,The most common shape for shafts is,circular,and the,cross section(,截面,),can be either solid or hollow(hollow shafts can,result in weight savings,减轻重量,),机械工程专业英语教程,1/24/2026,Text tour,8,Rectangular shafts are sometimes used,，,as in,screwdriver blades,，,socket wrenches and control knob stems,（螺丝,刀,的头、套筒扳手和控制旋扭的杆）,A shaft must have adequate,torsional,strength,（抗扭强度）,to transmit,torque,and not be over stressed,机械工程专业英语教程,1/24/2026,9,Generally speaking,，,the angle of twist,（扭转角）,should not exceed one degree in a shaft length equal to 20 diameters,It must also be,torsionally,stiff,（刚度）,enough so that one mounted component does not deviate excessively from its,original,angular position relative to a second component mounted on the same shaft,Shafts are mounted in,bearings,and transmit power through such devices as,gears,，,pulleys,，,cams and clutches,（齿轮、皮带轮、凸轮和离合器）,机械工程专业英语教程,1/24/2026,10,These devices introduce forces which attempt to,bend,the shaft,；,hence,，,the shaft must be,rigid,enough to prevent overloading of the supporting,bearings,In general,，,the,bending deflection,of a shaft should not exceed 0.01,in,per,ft,of length between bearings supports,In addition,，,the shaft must be able to sustain a combination of,bending and,torsional,loads,（弯矩和扭矩）,Thus an,equivalent,（等效的，当量的）,load,must be considered which,takes into account,both,torsion,and,bending,机械工程专业英语教程,1/24/2026,11,Also,，,the allowable stress must contain,a factor of safety,which includes,fatigue,，,since,torsional,and bending stress,reversals,（交变）,occur,For diameters less than 3 in.,the usual shaft material is,cold-rolled,steel containing about 0.4 percent,carbon,机械工程专业英语教程,1/24/2026,12,Shafts are either,cold,rolled,or,forge,（锻造）,in sizes from 3 in.to 5 in.,For sizes about over 5 in.,，,shafts are,forged,and,machined,to size,机械工程专业英语教程,1/24/2026,13,Plastic,shafts are widely used for light load applications,One advantage of using,plastic,is safety in electrical applications,，,since plastic is a,poor conductor,（导体）,of electricity,Components such as gears and,pulleys,are mounted on shafts by means of,key,机械工程专业英语教程,1/24/2026,14,The design of the,key,and the corresponding,keyway,（,键槽）,in the shaft must be properly evaluated,（分析，判断）,For example,，,stress concentrations,（应力集中）,occur in shafts due to,keyways,，,and the material removed to form the keyway further weakens the shaft,If shafts are run at,critical,（临界的）,speeds,，,severe,（严重的，强烈的）,vibrations,can occur which can seriously damage a machine,机械工程专业英语教程,1/24/2026,15,It is important to know the magnitude of these critical speeds so that they can be avoided,As a,general rule of,thumb,（一般,凭经验来说），,the,difference between the operating speed and the critical speed,should be at least 20 percent,Many shafts are supported by three or more,bearings,which means that the problem is,statically indeterminate,（静不定的，超静定的）,.,机械工程专业英语教程,1/24/2026,16,Texts on,strength of materials,（材料力学）,give methods of solving such problems.The design effort should be in,keeping with,the economics of a given situation.,Another important aspect of shaft design is the method of directly connecting one shaft to another,This is accomplished,（完成）,by devices such as,rigid and flexible couplings(,刚性或者弹性联轴器,),机械工程专业英语教程,1/24/2026,17,A,coupling,is a device for connecting the ends of,adjacent,（相邻的）,shafts,In machine construction,，,couplings are used to effect a,semipermanent,（半永久性的）,connection between adjacent rotating shafts,机械工程专业英语教程,1/24/2026,18,The connection is permanent in the sense that it is not mean to be broken,（拆开，破坏）,during the useful life of the machine,，,but it can be,broken and restored,（再安装）,in an emergency or when,worn parts,（磨损的零件）,are replaced,机械工程专业英语教程,1/24/2026,19,There are several types of shaft,couplings,，,theirs characteristics depend on the purpose for which they are used,If an exceptionally long shaft is required in a,manufacturing plant,or a,propeller,shaft on a ship,，,it is made in sections that are coupled together with rigid couplings,A common type of rigid coupling consists of two,mating radial flanges(disks,）（,配对的法兰（盘,),that are attached by,key,driven hubs(,靠键传动的轴套,)to the ends of adjacent shaft sections and,bolted,together through the,flanges,to form a rigid connection,Alignment,（找正，找平）,of the connected shafts is usually effected by means of a,rabbet joint,（连接缺口）,on the face of the,flanges,(,靠法兰面槽口来对准,),In connecting shafts belonging to separate devices(such as an electric motor and a gearbox,），,precise aligning of the shafts(,精确地对准,)is difficult and a,flexible coupling,is used,This coupling connects the shafts in such a way as to minimize the harmful effects of shaft,misalignment,（不同心）,Flexible couplings also permit the shafts to deflect,（偏离）,under their separate systems of loads and to move freely,（,float,）,in the axial direction without,interfering with,one another,Flexible couplings can also serve to,reduce the intensity of shock loads and vibrations,transmitted from one shaft to another,