外文翻译--机构和机器原理.doc

英文原文MECHANISMSANDMACHINETHEORY1.IntroductiontoMechanism：Thefunctionofamechanismistotransmitortransformmotionfromonerigidbodytoanotheraspartoftheactionofamachine.Therearethreetypesofcommonmechanicaldevicesthatcanbeusedasbasicelementsofamechanism.1、Gearsystem,inwhichtoothedmembersincontacttransmitmotionbetweenrotatingshafts.2、Camsystem,whereauniformmotionofaninputmemberisconvertedintoanonuniformmotionoftheoutputmember.3、Planeandspatiallinkagesarealsousefulincreatingmechanicalmotionsforapointorrigidbody.Akinematicchainisasystemoflinks,thatis,rigidbodies,whichareeitherjointedtogetherorareincontactwithoneanotherinamannerthatpermitsthemtomoverelativetooneanother.Ifoneofthelinksisfixedandthemovementofanyotherlinktoanewpositionwillcauseeachoftheotherlinkstomovetodefinitepredictableposition,thesystemisaconstrainedkinematicchain.Ifoneofthelinksisheldfixedandthemovementofanyotherlinktoanewpositionwillnotcauseeachoftheotherlinkstomovetoadefinitepredictablepositionthenthesystemisanunconstrainedkinematicchain,Amechanismorlinkageisaconstrainedkinematicchain,andisamechanicaldevicethathasthepurposeoftransferringmotionand/orforcefromasourcetoanoutput.Alinkageconsistsoflinks(orbars),generallyconsideredrigid,whichareconnectedbyjoints,suchaspinCorrevolute)orprismaticjoints,toformopenorclosedchains(orloops).Suchkinematicchains,withatleastonelinkfixed,becomemechanismsifatleasttwootherlinksremainmobility,orstructuresifnomobilityremains.Inotherwords,amechanismpermitsrelativemotionbetweenitsrigidlinks；astructuredoesnot.Sincelinkagesmakesimplemechanismsandcanbedesignedtoperformcomplextasks,suchasnonlinearmotionandforcetransmissiontheywillreceivemuchattentioninmechanismstudy.Mechanismsareusedinagreatvarietyofmachinesanddevices.Thesimplestclosed-looplinkageisthefour-barlinkage,whichhasthreemovinglinks(plusonefixedlink)andfourpinjoints.Thelinkthatisconnectedtothepowersourceorprimemoverandhasonemovingpivotandonegroundpivotiscalledtheinputlink.Theoutputlinkconnectsanothermovingpivottoanothergroundpivot.Thecouplerorfloatinglinkconnectedthetwomovingpivots,therebycouplingtheinputtotheoutputlink.Thefour-barlinkagehassomespecialconfigurationscreatedbymakingoneormorelinksinfiniteinlength.Theslider-crank(orcrankandslider)mechanismisafour-barchainwithasliderreplacinganinfinitelylongoutputlink.Theinternalcombustionengineisbuiltbasedonthismechanism.Otherformsoffour-linkmechanismsexistinwhichasliderisguidedonamovinglinkratherthanonafixedlink.Thesearecalledinversionsoftheslider-crank,producedwhenanotherlink(thecrank,coupler,orslider)isfixedlink.Althoughthefour-barlinkageandslider-crankmechanismareveryusefulandfoundinthousandsofapplications,wecanseethattheselinkageshavelimitedperformancelevel.Linkageswithmoremembersareoftenusedinmoredemandingcircumstances.Howeveritisoftendifficulttovisualizethemovementofamultilooplinkage,especiallywhenothercomponentsappearinthesamediagram.Thefirststepinthemotionanalysesofmorecomplicatedmechanismsistosketchtheequivalentkinematicorskeletondiagram.Theskeletondiagramservesapurposesimilartothatoftheelectricalschematicorcircuitdiagram.Organizationmovementanalysissecondstep:Drawsagraphicchart,ismustdeterminetheorganizationthenumberofdegreesoffreedom.Basedondegreeoffreedom,butItalyrefersneedscertainindependentinputsthemovementnumber,bydeterminedorganizationallcomponentsareoppositeinthegroundposition.Thepeoplehavethousandsofdifferenttypesconceivablythelinkmotiongear.Youmayimagineabagcontainingmassivelinkmotiongearthecomponent:Twopolegroups,threepolegroups,fourpolegroupsandsoon,aswellascomponents,rotation,motion,camfollower,gear,toothchain,chainwheel,leatherbelt,beltpulleyandsoon.(Spheremovement,screwvice-aswellasthepermissionthreedimensionalrelativemotionotherconnectionsnotyetincludes,here,discussesinparallelplanesmerelyplanemotion).Moreoveryouconceivableputthesecomponentsvarioustypeslinkmotiongearpossibilitywhichformsinthesameplace.Howexistshelpsthepeopletocontrolformstheseorganizationstherule?Infact,themajorityorganizationdutyisrequestsasoleinputtotransmittoasoleoutput.Thereforethesingledegreeoffreedomorganizationusesmostonekindoforganizationtype.Forexample,namelymayseebytheintuition:Fourpoleorganizationsareasingledegreeoffreedomlinkmotiongear.Thepicturemotiondiagramandthedeterminationorganizationdegreeoffreedomprocess,isthemovementanalysisandthesynthesisprocessfirststage.Inthemovementanalysis,addsonitscharacteristicaccordingtotheorganizationgeometryshapewhichpossiblyknew(forexampleinputangle,speed,angleaccelerationandsoon)studiesthedeterminationconcreteorganization.Ontheotherhand,themovementsynthesisisdesignsanorganizationtocompletethedutyprocesswhichaninstituterequests.Inthis,choosestheneworganizationthetypeandthesizeisamovementsynthesispart.Conceivestherelativemotionability,canguessthereasonthatdesignsanorganizationthereasonandmakestheimprovementtoaconcretedesignabilityislikethisasuccessfulorganizationscientistssymbol.Althoughtheseabilitiescomefromthecongenitalcreativity,howevermoreisbecausehasgraspedthetechnologywhichenhancesfromthepractice.1.1Themovementanalysis：simpleoneofmostusefulorganizationsisfourpoleorganizations.Inonfollowingelaborationmajorityofcontentcentralismdiscussionlinkmotiongear,butthisprocedureisalsosuitableforthemorecomplexlinkmotiongear.Wealreadyknewfourpoleorganizationshaveadegreeoffreedom.Aboutfourpoleorganizations,hastheusefulmorecontentswhichmustknow?Indeedissome!ThesepulltheXiaohusbandcriterionincludingthestandard,thetransformationconcept,theblindspotposition(divergencepoint),branchoffice,transmissionangle,withtheirsmovementcharacteristic,includingposition,speedandacceleration.Fourpoleorganizationsmayhaveonekindofbeingcalledascrankrockerorganizationform,onekindofdoublerockingleverorganization,onekindofdoublecrank(tensionbar)doestheorganization,whichoneformsendiniscalledastheorganization,isdecidedintwopolemovementscopeswhich(fixedcomponent)connectswiththerack.Thecrankrockerorganizationinputcomponent,thecrankmayrevolvethrough360andthecontinuousrotation,butoutputsthecomponenttomaketheundulationmerely(i.e.swingmember).Asanexceptionalcase,intheparallelfourpoleorganization,inputsthepolethelengthtobeequaltooutputsthepolethelength,thego-betweenlengthandthefixedlink(rack)length,alsoisequal.Itsinputandtheoutputallmaymakethecompletealternationrotationortransformthebeingcalledasantiparallelquadrangleorganizationtheoverlappingstructure.ThestandardpullstheXiaohusbandcriterion(theorem)toindicatethat,Ifinfourpoleorganizations,betweentwopolescandowillfullyrelativelyrotatescontinuously,that,itslongestpolelengthissmallerthansumofwiththeshortestpolelengthorisequaltosumoftheothertwopolelength.Shouldpayattention:Thesamefourpoleorganization,mayhavethedifferentform,whichpoleisthisdecidedinwasstipulated(i.e.makesfixedlink)astherack.Themovementtransformationprocessisinthefixedorganizationtransmissionchaindifferentmemberhasthedifferentorganizationrateprocess.Besideshasaboutthecomponentrotationscopeknowledge,butalsomusthavehowcausestheorganizationbeforethemanufactureonenergy“therevolution”thegoodmeasure,thatwillbeveryuseful.Hardenbergh(Hartenberg)speaksof:“Therevolution”isterminology,itssignificancepassestooutputsthecomponentthemovementvalidity.Itmeanttherevolutionissteady,inwhichcaninoutputinthecomponenttohaveastrengthorthetorquebiggestforcecomponentiseffective.Notonlyalthoughthefinaloutputstrengthorthetorquearetheconnectingrodgeometricfigurefunctions,moreoveralsoisgenerallythepowerortheforceofinertiaresult,thatisfrequentlybigtolikestaticstrengthseveraltimes.Inordertoanalyzetheidlingorinordertoeasytoobtainhowcancauseanyorganization“therevolution”theindex,thetransmissionangleconceptisextremelyuseful.Inorganizationmovementperiod,thetransmissionanglevalueischanging.Thetransmissionangle0mayoccurinthespecialposition.Willoutputthepolebutinthisspecialpositionthemovementwithnottoexertinputsonthepolethestrengthmanytohavenothingtodowithgreatly.Infact,asaresultofthemovementvice-frictioninfluence,thegeneralbasispracticalexperience,withthetransmissionangleplanningboardwhichisbiggerthantherating.Theweightlinkmotiong