机械类外文文献及翻译

机械类外文文献及翻译（文档含中英文对照即英文原文和中文翻译）原文：GEARANDSHAFTINTRODUCTIONAbstract:Theimportantpositionofthewheelgearandshaftcan'tfalterintraditionalmachineandmodernmachines.Thewheelgearandshaftsmainlyinstallthedirectionthatdeliversthedintattheprincipalaxisbox.Thepassingtoprocesstomakethemcanisdividedintomanymodelnumbers,usingformanysituationsrespectively.Sowemustbethemultilayerstotheunderstandingofthewheelgearandshaftinmanyways.Keywords:Wheelgear;ShaftIntheforceanalysisofspurgears,theforcesareassumedtoactinasingleplane.Weshallstudygearsinwhichtheforceshavethreedimensions.Thereasonforthis,inthecaseofhelicalgears,isthattheteetharenotparalleltotheaxisofrotation.Andinthecaseofbevelgears,therotationalaxesarenotparalleltoeachother.Therearealsootherreasons,asweshalllearn.Helicalgearsareusedtotransmitmotionbetweenparallelshafts.Thehelixangleisthesameoneachgear,butonegearmusthavearight-handhelixandtheotheraleft-handhelix.Theshapeofthetoothisaninvolutehelicoid.Ifapieceofpapercutintheshapeofaparallelogramiswrappedaroundacylinder,theangularedgeofthepaperbecomesahelix.Ifweunwindthispaper,eachpointontheangularedgegeneratesaninvolutecurve.Thesurfaceobtainedwheneverypointontheedgegeneratesaninvoluteiscalledaninvolutehelicoid.Theinitialcontactofspur-gearteethisalineextendingallthewayacrossthefaceofthetooth.Theinitialcontactofhelicalgearteethisapoint,whichchangesintoalineastheteethcomeintomoreengagement.Inspurgearsthelineofcontactisparalleltotheaxisoftherotation;inhelicalgears,thelineisdiagonalacrossthefaceofthetooth.Itisthisgradualoftheteethandthesmoothtransferofloadfromonetoothtoanother,whichgivehelicalgearstheabilitytotransmitheavyloadsathighspeeds.Helicalgearssubjecttheshaftbearingstobothradialandthrustloads.Whenthethrustloadsbecomehighorareobjectionableforotherreasons,itmaybedesirabletousedoublehelicalgears.Adoublehelicalgear(herringbone)isequivalenttotwohelicalgearsofoppositehand,mountedsidebysideonthesameshaft.Theydevelopoppositethrustreactionsandthuscanceloutthethrustload.Whentwoormoresinglehelicalgearsaremountedonthesameshaft,thehandofthegearsshouldbeselectedsoastoproducetheminimumthrustload.Crossed-helical,orspiral,gearsarethoseinwhichtheshaftcenterlinesareneitherparallelnorintersecting.Theteethofcrossed-helicalfearshavepointcontactwitheachother,whichchangestolinecontactasthegearswearin.Forthisreasontheywillcarryoutverysmallloadsandaremainlyforinstrumentalapplications,andaredefinitelynotrecommendedforuseinthetransmissionofpower.Thereisondifferencebetweenacrossedheli:www.ChinaCwww.CAD.NameBBS.CAD.Namewww.ChinaCcalgearandahelicalgearuntiltheyaremountedinmeshwitheachother.Theyaremanufacturedinthesameway.Apairofmeshedcrossedhelicalgearsusuallyhavethesamehand;thatis,aright-handdrivergoeswitharight-handdriven.Inthedesignofcrossed-helicalgears,theminimumslidingvelocityisobtainedwhenthehelixangleareequal.However,whenthehelixanglearenotequal,thegearwiththelargerhelixangleshouldbeusedasthedriverifbothgearshavethesamehand.Wormgearsaresimilartocrossedhelicalgears.Thepinionorwormhasasmallnumberofteeth,usuallyonetofour,andsincetheycompletelywraparoundthepitchcylindertheyarecalledthreads.Itsmatinggeariscalledawormgear,whichisnotatruehelicalgear.Awormandwormgearareusedtoprovideahighangular-velocityreductionbetweennonintersectingshaftswhichareusuallyatrightangle.Thewormgearisnotahelicalgearbecauseitsfaceismadeconcavetofitthecurvatureoftheworminordertoprovidelinecontactinsteadofpointcontact.However,adisadvantageofwormgearingisthehighslidingvelocitiesacrosstheteeth,thesameaswithcrossedhelicalgears.Wormgearingareeithersingleordoubleenveloping.Asingle-envelopinggearingisoneinwhichthegearwrapsaroundorpartiallyenclosestheworm..Agearinginwhicheachelementpartiallyenclosestheotheris,ofcourse,adouble-envelopingwormgearing.Theimportantdifferencebetweenthetwoisthatareacontactexistsbetweentheteethofdouble-envelopinggearswhileonlylinecontactbetweenthoseofsingle-envelopinggears.Thewormandwormgearofasethavethesamehandofhelixasforcrossedhelicalgears,butthehelixanglesareusuallyquitedifferent.Thehelixangleonthewormisgenerallyquitelarge,andthatonthegearverysmall.Becauseofthis,itisusualtospecifytheleadangleontheworm,whichisthecomplementofthewormhelixangle,andthehelixangleonthegear;thetwoanglesareequalfora0-deg.Shaftangle.Whengearsaretobeusedtotransmitmotionbetweenintersectingshaft,someofbevelgearisrequired.Althoughbevelgearareusuallymadeforashaftangleof0deg.Theymaybeproducedforalmostanyshaftangle.Theteethmaybecast,milled,orgenerated.Onlythegeneratedteethmaybeclassedasaccurate.Inatypicalbevelgearmounting,oneofthegearisoftenmountedoutboardofthebearing.Thismeansthatshaftdeflectioncanbemorepronouncedandhaveagreatereffectonthecontactofteeth.Anotherdifficulty,whichoccursinpredictingthestressinbevel-gearteeth,isthefacttheteetharetapered.Straightbevelgearsareeasytodesignandsimpletomanufactureandgiveverygoodresultsinserviceiftheyaremountedaccuratelyandpositively.Asinthecaseofsqurgears,however,theybecomenoisyathighervaluesofthepitch-linevelocity.Inthesecasesitisoftengo:www.ChinaCwww.CAD.NameBBS.CAD.Namewww.ChinaCoddesignpracticetogotothespiralbevelgear,whichisthebevelcounterpartofthehelicalgear.Asinthecaseofhelicalgears,spiralbevelgearsgiveamuchsmoothertoothactionthanstraightbevelgears,andhenceareusefulwherehighspeedareencountered.Itisfrequentlydesirable,asinthecaseofautomotivedifferentialapplications,tohavegearingsimilartobevelgearsbutwiththeshaftoffset.Suchgearsarecalledhypoidgearsbecausetheirpitchsurfacesarehyperboloidsofrevolution.Thetoothactionbetweensuchgearsisacombinationofrollingandslidingalongastraightlineandhasmuchincommonwiththatofwormgears.Ashaftisarotatingorstationarymember,usuallyofcircularcrosssection,havingmounteduponitsuchelementsasgears,pulleys,flywheels,cranks,sprockets,andotherpower-transmissionelements.Shaftmaybesubjectedtobending,tension,compression,ortorsionalloads,actingsinglyorincombinationwithoneanother.Whentheyarecombined,onemayexpecttofindbothstaticandfatiguestrengthtobeimportantdesignconsiderations,sinceasingleshaftmaybesubjectedtostaticstresses,completelyreversed,andrepeatedstresses,allactingatthesametime.Theword“shaft”coversnumeariations,suchasaxlesandspindles.Anaxleisashaft,witherstationaryorrotating,norsubjectedtotorsionload.Ashirtrotatingshaftisoftencalledaspindle.Wheneitherthelateralorthetorsionaldeflectionofashaftmustbeheldtocloselimits,theshaftmustbesizedonthebasisofdeflectionbeforeanalyzingthestresses.Thereasonforthisisthat,iftheshaftismadestiffenoughsothatthedeflectionisnottoolarge,itisprobablethattheresultingstresseswillbesafe.Butbynomeansshouldthedesignerassumethattheyaresafe;itisalmostalwaysnecessarytocalculatethemsothatheknowstheyarewithinacceptablelimits.Wheneverpossible,thepower-transmissionelements,suchasgearsorpullets,shouldbelocatedclosetothesupportingbearings,Thisreducesthebendingmoment,andhencethedeflectionandbendingstress.AlthoughthevonMises-Hencky-Goodmanmethodisdifficulttouseindesignofshaft,itprobablycomesclosesttopredictingactualfailure.Thusitisagoodwayofcheckingashaftthathasalreadybeendesignedorofdiscoveringwhyaparticularshafthasfailedinservice.Furthermore,thereareaconsiderablenumberofshaft-designproblemsinwhichthedimensionareprettywelllimitedbyotherconsiderations,suchasrigidity,anditisonlynecessaryforthedesignertodiscoversomethingaboutthefilletsizes,heat-treatment,andsurfacefinishandwhetherornotshotpeeningisnecessaryinordertoachievetherequiredlifeandreliability.Becauseofthesimilarityoftheirfunctions,clutchesandbrakesaretreatedtogether.Inasimplifieddynamicrepresentationofafrictionclutch,orbrake,twoin:www.ChinaCwww.CAD.NameBBS.CAD.Namewww.ChinaCertiasIandItravelingattherespectiveangularvelocitiesWandW,oneofwhichmaybezerointhecaseofbrake,aretobebroughttothesamespeedbyengagingtheclutchorbrake.Slippageoccursbecausethetwoelementsarerunningatdifferentspeedsandenergyisdissipatedduringactuation,resultinginatemperaturerise.Inanalyzingtheperformanceofthesedevicesweshallbeinterestedintheactuatingforce,thetorquetransmitted,theenergylossandthetemperaturerise.Thetorquetransmittedisrelatedtotheactuatingforce,thecoefficientoffriction,andthegeometryoftheclutchorbrake.Thisisprobleminstatic,whichwillhavetobestudiedseparatelyforeathgeometricconfiguration.However,temperatureriseisrelatedtoenergylossandcanbestudiedwithoutregardtothetypeofbrakeorclutchbecausethegeometryofinterestistheheat-dissipatingsurfaces.Thevarioustypesofclutchesandbrakesmaybeclassifiedasfllows:.Rimtypewithinternallyexpandingshoes.Rimtypewithexternallycontractingshoes.Bandtype.Diskoraxialtype.Conetype.MiscellaneoustypeTheanalysisofalltypeoffrictionclutchesandbrakesusethesamegeneralprocedure.Thefollowingsteparenecessary:.Assumeordeterminethedistributionofpressureonthefrictionalsurfaces..Findarelationbetweenthemaximumpressureandthepressureatanypoint.Applytheconditionofstaticalequilibriumtofind(a)theactuatingforce,(b)thetorque,and(c)thesupportreactions.Miscellaneousclutchesincludeseveraltypes,suchasthepositive-contactclutches,overload-releaseclutches,overrunningclutches,magneticfluidclutches,andothers.Apositive-contactclutchconsistsofashiftleverandtwojaws.Thegreatestdifferencesbetweenthevarioustypesofpositiveclutchesareconcernedwiththedesignofthejaws.Toprovidealongerperiodoftimeforshiftactionduringengagement,thejawsmayberatchet-shaped,orgear-tooth-shaped.Sometimesagreatmanyteethorjawsareused,andtheymaybecuteithercircumferentially,sothattheyengagebycylindricalmating,oronthefacesofthematingelements.Althoughpositiveclutchesarenotusedtotheextentofthefrictional-contacttype,theydohaveimportantapplicationswheresynchronousoperationisrequired.Devicessuchaslineardrivesormotor-operatedscrewdriversmustruntodefinitelimitandthencometoastop.Anoverload-releasetypeofclutchisrequiredfortheseapplications.Theseclutchesareusuallyspring-loadedsoastoreleaseatapredeterminedtoque.Theclickingsoundwhichisheardwhentheoverloadpointisreachedisconsideredtobeadesirablesignal.Anoverrunningclutchorcouplingpermitsthedrivenmemberofamachineto“freewheel^or“overrun"becausethedriverisstoppedorbecauseanothersourceofpowerincreasethespeedofthedriven.This:www.ChinaCwww.CAD.NameBBS.CAD.Nametypeofclutchusuallyusesrollersorballsmountedbetweenanoutersleeveandaninnermemberhavingflatsmachinedaroundtheperiphery.Drivingactionisobtainedbywedgingtherollersbetweenthesleeveandtheflats.Theclutchisthereforeequivalenttoapawlandratchetwithaninfinitenumberofteeth.Magneticfluidclutchorbrakeisarelativelynewdevelopmentwhichhastwoparallelmagneticplates.Betweentheseplatesisalubricatedmagneticpowdermixture.Anelectromagneticcoilisinsertedsomewhereinthemagneticcircuit.Byvaryingtheexcitationtothiscoil,theshearingstrengthofthemagneticfluidmixturemaybeaccuratelycontrolled.Thusanyconditionfromafullsliptoafrozenlockupmaybeobtained.齿轮和轴的介绍摘要:在传统机械和现代机械中齿轮和轴的重要地位是不可动摇的。齿轮和轴主要安装在主轴箱来传递力的方向。通过加工制造它们可以分为许多的型号，分别用于许多的场合。所以我们对齿轮和轴的了解和认识必须是多层次多方位的。关键词:齿轮；轴在直齿圆柱齿轮的受力分析中，是假定各力作用在单一平面的。我们将研究作用力具有三维坐标的齿轮。因此，在斜齿轮的情况下，其齿向是不平行于回转轴线的。而在锥齿轮的情况中各回转轴线互相不平行。像我们要讨论的那样，尚有其他道理需要学习，掌握。斜齿轮用于传递平行轴之间的运动。倾斜角度每个齿轮都一样，但一个必须右旋斜齿，而另一个必须是左旋斜齿。齿的形状是一溅开线螺旋面。如果一张被剪成平行四边形（矩形）的纸张包围在齿轮圆柱体上，纸上印出齿的角刃边就变成斜线。如果我展开这张纸，在血角刃边上的每一个点就发生一渐开线曲线。直齿圆柱齿轮轮齿的初始接触处是跨过整个齿面而伸展开来的线。斜齿轮轮齿的初始接触是一点，当齿进入更多的啮合时，它就变成线。在直齿圆柱齿轮中，接触是平行于回转轴线的。在斜齿轮中，该先是跨过齿面的对角线。它是齿轮逐渐进行啮合并平稳的从一个齿到另一个齿传递运动，那样就使斜齿轮具有高速重载下平稳传递运动的能力。斜齿轮使轴的轴承承受径向和轴向力。当轴向推力变的大了或由于别的原因而产生某些影响时，那就可以使用人字齿轮。双斜齿轮（人字齿轮）是与反向的并排地装在同一轴上的两个斜齿轮等效。他们产生相反的轴向推力作用，这样就消除了轴向推力。当两个或更多个单向齿斜齿轮被在同一轴上时，齿轮的齿向应作选择，以便产生最小的轴向推力。交错轴斜齿轮或螺旋齿轮，他们是轴中心线既不相交也不平行。交错轴斜齿轮的齿彼此之间发生点接触，它随着齿轮的磨合而变成线接触。因此他们只能传递小的载荷和主要用于仪器设备中，而且肯定不能推荐在动力传动中使用。交错轴斜齿轮与斜齿轮之间在被安装后互相捏合之前是没有任何区别的。它们是以同样的方法进行制造。一对相啮合的交错轴斜齿轮通常具有同样的齿向，即左旋主动齿轮跟右旋从动齿轮相啮合。在交错轴斜齿设计中，当该齿的斜角相等时所产生滑移速度最小。然而当该齿的斜角不相等时，如果两个齿轮具有相同齿向的话，大斜角齿轮应用作主动齿轮。蜗轮与交错轴斜齿轮相似。小齿轮即蜗杆具有较小的齿数，通常是一到四齿，由于它们完全缠绕在节圆柱上，因此它们被称为螺纹齿。与其相配的齿轮叫做蜗轮，蜗轮不是真正的斜齿轮。蜗杆和蜗轮通常是用于向垂直相交轴之间的传动提供大的角速度减速比。蜗轮不是斜齿轮，因为其齿顶面做成中凹形状以适配蜗杆曲率，目的是要形成线接触而不是点接触。然而蜗杆蜗轮传动机构中:www.ChinaCwww.CAD.NameBBS.CAD.Namewww.ChinaC存在齿间有较大滑移速度的缺点，正像交错轴斜齿轮那样。蜗杆蜗轮机构有单包围和双包围机构。单包围机构就是蜗轮包裹着蜗杆的一种机构。当然，如果每个构件各自局部地包围着对方的蜗轮机构就是双包围蜗轮蜗杆机构。着两者之间的重要区别是，在双包围蜗轮组的轮齿间有面接触，而在单包围的蜗轮组的轮齿间有线接触。一个装置中的蜗杆和蜗轮正像交错轴斜齿轮那样具有相同的齿向，但是其斜齿齿角的角度是极不相同的。蜗杆上的齿斜角度通常很大，而蜗轮上的则极小，因此习惯常规定蜗杆的导角，那就是蜗杆齿斜角的余角；也规定了蜗轮上的齿斜角，该两角之和就等于0度的轴线交角。当齿轮要用来传递相交轴之间的运动时，就需要某种形式的锥齿轮。虽然锥齿轮通常制造成能构成0度轴交角，但它们也可产生任何角度的轴交角。轮齿可以铸出，铣制或滚切加工。仅就滚齿而言就可达一级精度。在典型的锥齿轮安装中，其中一个锥齿轮常常装于支承的外侧。这意味着轴的挠曲情况更加明显而使在轮齿接触上具有更大的影响。另外一个难题，发生在难于预示锥齿轮轮齿上的应力，实际上是由于齿轮被加工成锥状造成的。直齿锥齿轮易于设计且制造简单，如果他们安装的精密而确定，在运转中会产生良好效果。然而在直齿圆柱齿轮情况下，在节线速度较高时，他们将发出噪音。在这些情况下，螺旋锥齿轮比直齿轮能产生平稳的多的啮合作用，因此碰到高速运转的场合那是很有用的。当在汽车的各种不同用途中，有一个带偏心轴的类似锥齿轮的机构，那是常常所希望的。这样的齿轮机构叫做准双曲面齿轮机构，因为它们的节面是双曲回转面。这种齿轮之间的轮齿作用是沿着一根直线上产生滚动与滑动相结合的运动并和蜗轮蜗杆的轮齿作用有着更多的共同之处。轴是一种转动或静止的杆件。通常有圆形横截面。在轴上安装像齿轮，皮带轮，飞轮，曲柄，链轮和其他动力传递零件。轴能够承受弯曲，拉伸，压缩或扭转载荷，这些力相结合时，人们期望找到静强度和疲劳强度作为设计的重要依据。因为单根轴可以承受静压力，变应力和交变应力，所有的应力作用都是同时发生的。“轴”这个词包含着多种含义，例如心轴和主轴。心轴也是轴，既可以旋转也可以静止的轴，但不承受扭转载荷。短的转动轴常常被称为主轴。当轴的弯曲或扭转变形必需被限制于很小的范围内时，其尺寸应根据变形来确定，然后进行应力分析。因此，如若轴要做得有足够的刚度以致挠曲不太大，那么合应力符合安