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英文原文ConnectingrodInareciprocatingpistonengine,theconnectingrodorconrodconnectsthepistontothecrankorcrankshaft.Theconnectingrodwasinventedsometimebetween1174and1200whenaMusliminventor,engineerandcraftsmannamedalJazaribuiltfivemachinestopumpwaterforthekingsoftheTurkishArtuqiddynastyoneofwhichincorporatedtheconnectingrod.Transferringrotarymotiontoreciprocatingmotionwasmadepossiblebyconnectingthecrankshafttotheconnectingrod,whichwasdescribedintheBookofKnowledgeofIngeniousMechanicalDevices.Thedoubleactingreciprocatingpistonpumpwasthefirstmachinetoofferautomaticmotion,butitsmechanismsandotherssuchasthecam,wouldalsohelpinitiatetheIndustrialRevolution.InternalcombustionenginesInmodernautomotiveinternalcombustionengines,theconnectingrodsaremostusuallymadeofsteelforproductionengines,butcanbemadeofaluminiumforlightnessandtheabilitytoabsorbhighimpactattheexpenseofdurabilityortitaniumforacombinationofstrengthandlightnessattheexpenseofaffordabilityforhighperformanceengines,orofcastironforapplicationssuchasmotorscooters.Theyarenotrigidlyfixedateitherend,sothattheanglebetweentheconnectingrodandthepistoncanchangeastherodmovesupanddownandrotatesaroundthecrankshaft.Thesmallendattachestothepistonpin,gudgeonpintheusualBritishtermorwristpin,whichiscurrentlymostoftenpressfitintotheconrodbutcanswivelinthepiston,afloatingwristpindesign.Thebigendconnectstothebearingjournalonthecrankthrow,runningonreplaceablebearingshellsaccessibleviatheconrodboltswhichholdthebearingcapontothebigendtypicallythereisapinholeboredthroughthebearingandthebigendoftheconrodsothatpressurizedlubricatingmotoroilsquirtsoutontothethrustsideofthecylinderwalltolubricatethetravelofthepistonsandpistonrings.Theconrodisundertremendousstressfromthereciprocatingloadrepresentedbythepiston,actuallystretchingandrelaxingwitheveryrotation,andtheloadincreasesrapidlywithincreasingenginespeed.Failureofaconnectingrod,usuallycalledthrowingarodisoneofthemostcommoncausesofcatastrophicenginefailureincars,frequentlyputtingthebrokenrodthroughthesideofthecrankcaseandtherebyrenderingtheengineirreparableitcanresultfromfatiguenearaphysicaldefectintherod,lubricationfailureinabearingduetofaultymaintenance,orfromfailureoftherodboltsfromadefect,impropertightening,orreuseofalreadyusedstressedboltswherenotrecommended.Despitetheirfrequentoccurrenceontelevisedcompetitiveautomobileevents,suchfailuresarequiterareonproductioncarsduringnormaldailydriving.Thisisbecauseproductionautopartshaveamuchlargerfactorofsafety,andoftenmoresystematicqualitycontrol.Whenbuildingahighperformanceengine,greatattentionispaidtotheconrods,eliminatingstressrisersbysuchtechniquesasgrindingtheedgesoftherodtoasmoothradius,shotpeeningtoinducecompressivesurfacestressestopreventcrackinitiation,balancingallconrod/pistonassembliestothesameweightandMagnafluxingtorevealotherwiseinvisiblesmallcrackswhichwouldcausetherodtofailunderstress.Inaddition,greatcareistakentotorquetheconrodboltstotheexactvaluespecifiedoftentheseboltsmustbereplacedratherthanreused.Thebigendoftherodisfabricatedasaunitandcutorcrackedintwotoestablishprecisionfitaroundthebigendbearingshell.Therefore,thebigendcapsarenotinterchangeablebetweenconrods,andwhenrebuildinganengine,caremustbetakentoensurethatthecapsofthedifferentconrodsarenotmixedup.Boththeconrodanditsbearingcapareusuallyembossedwiththecorrespondingpositionnumberintheengineblock.RecentenginessuchastheFord4.6literengineandtheChrysler2.0literengine,haveconnectingrodsmadeusingpowdermetallurgy,whichallowsmoreprecisecontrolofsizeandweightwithlessmachiningandlessexcessmasstobemachinedoffforbalancing.Thecapisthenseparatedfromtherodbyafracturingprocess,whichresultsinanunevenmatingsurfaceduetothegrainofthepowderedmetal.Thisensuresthatuponreassembly,thecapwillbeperfectlypositionedwithrespecttotherod,comparedtotheminormisalignmentswhichcanoccurifthematingsurfacesarebothflat.Amajorsourceofenginewearisthesidewaysforceexertedonthepistonthroughtheconrodbythecrankshaft,whichtypicallywearsthecylinderintoanovalcrosssectionratherthancircular,makingitimpossibleforpistonringstocorrectlysealagainstthecylinderwalls.Geometrically,itcanbeseenthatlongerconrodswillreducetheamountofthissidewaysforce,andthereforeleadtolongerenginelife.However,foragivenengineblock,thesumofthelengthoftheconrodplusthepistonstrokeisafixednumber,determinedbythefixeddistancebetweenthecrankshaftaxisandthetopofthecylinderblockwherethecylinderheadfastensthus,foragivencylinderblocklongerstroke,givinggreaterenginedisplacementandpower,requiresashorterconnectingrodorapistonwithsmallercompressionheight,resultinginacceleratedcylinderwear.CompoundrodsManycylindermultibankenginessuchasaV12layouthavelittlespaceavailableforthatmanyconnectingrodjournalsonalimitedlengthofcrankshaft.Thisisadifficultcompromisetosolveanditsconsequencehasoftenledtoenginesbeingregardedasfailures.Thesimplestsolution,almostuniversalinroadcarengines,istousesimplerods.Thisrequirestherodbearingstobenarrower,increasingbearingloadandtheriskoffailureinahighperformanceengine.Thisalsomeanstheopposingcylindersarenotexactlyinlinewitheachother.Incertaintypesofengine,themasterrodcarriesoneormoreringpinstowhichareboltedthemuchsmallerbigendsofslaverodsonothercylinders.Radialenginestypicallyhaveamasterrodforonecylinderandslaverodsforalltheothercylindersinthesamebank.CertaindesignsofVenginesuseamaster/slaverodforeachpairofoppositecylinders.Adrawbackofthisisthatthestrokeofthesubsidiaryrodisslightlyshorterthanthemaster,whichincreasesvibrationinaveeengine.Theusualsolutionforhighperformanceaeroenginesisaforkedconnectingrod.Onerodissplitintwoatthebigendandtheotheristhinnedtofitintothisfork.Thejournalisstillsharedbetweencylinders.TheRollsRoyceMerlinusedthisstyle.CranklinkageofthetypeandcharacteristicsTheuseoftheinternalcombustionenginecranklinkageofmanytypes,accordingtokinematicsperspectivecanbedividedintothreecategories,namelyHeartcranklinkage,theeccentriccranklinkageandthemainvicelinkcranklinkage.Centrecranklinkageischaracterizedbythecylinderthroughthecenterlineofthecrankshaftrotationcentreandperpendiculartotheaxisofrotationofthecrank.Thistypeoflinkageintheinternalcombustionenginecrankinthemostwidelyused.Thesingleenginegeneral,tiedforlinkagewiththeuseoftheVshapedchaxinglinktheinternalcombustionengine,andthehomeofthepistoninternalcombustionenginecranklinkagefallintothiscategory.Eccentriccranklinkageischaracterizedbyverticalcylindercenterlineofthecrankshaftrotatinginthecenter,butnotbycrankshaftrotarycentre,thecylindercenterlinedistancebetweenthecrankshaftwitharotaryaxisoffsete.Thiscranklinkageinstitutionscanreducetheswellingintheitineraryofthepistonandcylinderintramurallargestlateralpressuresothatthepistonsintheexpansionprogrammeandpressurereductionprogrammeinthecylinderwallattheroleoflateralpressureonbothsidesoftherelativelyuniformsize.Vicelinkthemaincranklinkageischaracterizedbytheinternalcombustionenginecylinderwithamainlink,theotheroutvicelinkcylinderused,thesearenotdirectlinktothebottomofthecrankpins,butonsalethroughthedeputylinkwithinthemainlinkofthebigheads,formedajointmovement,suchinstitutionsalsosometimesreferredtoasjointsongstalklinkage.Cranklinkageinthejoint,acrankcanputafewofconnectingrodandpiston,Thisstructurewillshortenthelengthoftheinternalcombustionengine,compactandwidelyusedinhighpowerlocomotivesusedtanksandVshapedinternalcombustionengine.BoringInmachining,boringistheprocessofenlargingaholethathasalreadybeendrilledorcast,bymeansofasinglepointcuttingtoolorofaboringheadcontainingseveralsuchtools,forexampleasinboringacannonbarrel.Boringisusedtoachievegreateraccuracyofthediameterofahole,andcanbeusedtocutataperedhole.Thetermboringisalsosometimesusedfordrillingahole.MachineBoringTheboringprocesscanbecarriedoutonalatheforsmalleroperations,butforlargerproductionpiecesaspecialboringmillworkpiecerotationaroundaverticalaxisorahorizontalboringmachinerotationaroundhorizontalaxisareused.Ataperedholecanalsobemadebyswivelingthehead.TheboringmachinessimilartothemillingmachinessuchastheclassicVanNormancomeinalargevarietyofsizesandstyles.Workpiecediametersarecommonly14m312ftbutcanbeaslargeas20m60ft.Powerrequirementscanbeasmuchas200hp.Thecontrolsystemscanbecomputerbased,allowingforautomationandincreasedconsistency.Becauseboringismeanttodecreasetheproducttolerancesonpreexistingholes,severaldesignconsiderationsmustbemade.First,largelengthtoborediametersarenotpreferredduetocuttingtooldeflection.Next,throughholesarepreferredoverblindholesholesthatdonottraversethethicknessoftheworkpiece.Interruptedinternalworkingsurfaceswherethecuttingtoolandsurfacehavediscontinuouscontactshouldbeavoided.Theboringbaristheprotrudingarmofthemachinethatholdscuttingtools,andmustbeveryrigid.ForgingForgingisthetermforshapingmetalbyusinglocalizedcompressiveforces.Coldforgingisdoneatroomtemperatureornearroomtemperature.Hotforgingisdoneatahightemperature,whichmakesmetaleasiertoshapeandlesslikelytofracture.Warmforgingisdoneatintermediatetemperaturebetweenroomtemperatureandhotforgingtemperatures.Forgedpartscanrangeinweightfromlessthanakilogramto170metrictons.Forgedpartsusuallyrequirefurtherprocessingtoachieveafinishedpart.TheselectionofbaseandpositioningThebasepositionisprotocolmachiningline,determinetheprocessingplanoftheimportantworktodofirstMake.Choosecorrectly,theyankeeswilldirectlyinfluencethereasonableornot,themachiningofqualityandproductivity.Whenselectingpositionintheplane,needtoconsiderthefollowingquestions1inwhichasurfaceastheessenceandsurfaceorunifiedstandards,2toensuremachiningprecision,3Makethemachiningprocesssmoothly4forprocessingthepureplaneorunity,5shouldbeadoptedasaroughsurfaceplane6whetherindividualprocessesforspecialprocessingrequirements,7needtoemployunifiedstandardsofplaneoutsideAccordingtotheessenceandtheyankeeschoicefine,fineandselectionprinciplesshouldbeconsideredwhenthefirst,thebenchmarkoverlapInmay,namely,underthesituationofthemachinedsurfaceshouldbechosenforthelocatingdatumdesignstandards.Intheprocessofconnectingthemachiningprocess,mostofaspecifiedprocessselectionofendandsmallheadholeAsthemainbase,withbigholeinthesideoutsidethedesignatedasanotherroundfaceincludessurface.Thisisduetotheface.Largearea,morestable,Withlittleheadpositioncandirectlycontrolsizeholeholecenterdistanceofthehead.ItmakesTheprocessoflocatingdatum,reducepositioningerror.Furtherstudyagain,Accordingtothedrawing,thesizeoftheconnectingpartshaveaheadholesurfacenamelytherightendinaflatsurface,Therefore,butcanalsobeprocessedanotherendleftisnotanend,fortheplaneasItisdisadvantageouspositiondatum.Therefore,intheprocessofthelocalizationplantoidea.Astheyankeesroundholesmallhead,solittleheadoutsidesurfaceprocessingroundholearrangementearly.InsmallheadandlargeBeforetheyankeesheadholeasorientationofthemachiningprocessesanddrilling,reaming,theseproceduresforprocessingaftertheholeTheholeisparallelwiththatsometimesaffectstheprocessingprecisionfollowupprocesses,therefore,shouldbeinprocessingNotethatchoosesreas
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