滚动轴承机械外文翻译中英文.docx
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滚动轴承机械外文翻译中英文.docx
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滚动轴承机械外文翻译中英文
附录
附录1
英文原文
RollingContactBearings
Theconcernofamachinedesignerwithballandrollerbearingsisfivefoldasfollows:
(a)lifeinrelationtoload;(b)stiffness,i.e.deflectionsunderload;(c)friction;(d)wear;(e)noise.Formoderateloadsandspeedsthecorrectselectionofastandardbearingonthebasisofaloadratingwillbecomeimportantwhereloadsarehigh,althoughthisisusuallyoflessmagnitudethanthatoftheshaftsorothercomponentsassociatedwiththebearing.Wherespeedsarehighspecialcoolingarrangementsbecomenecessarywhichmayincreasefricitionaldrag.Wearisprimarilyassociatedwiththeintroductionofcontaminants,andsealingarrangementsmustbechosenwithregardtothehostilityoftheenvironment.
Becausethehighqualityandlowpriceofballandrollerbearingdependsonquantityproduction,thetaskofthemachinedesignerbecomesoneofselectionratherthandesign.Rolling-contactbearingsaregenerallymadewithsteelwhichisthrough-hardenedtoabout900HV,althoughinmanymechanismsspecialracesarenotprovidedandtheinteractingsurfacesarehardenedtoabout600HV.Itisnotsurprisingthat,owingtothehighstressesinvolved,apredominantformoffailureshouldbemetalfatigue,andagooddealofworkisbasedonacceptvaluesoflifeanditisgeneralpracticeinbearingindustrytodefinetheloadcapacityofthebearingasthatvaluebelowwhich90percentofabatchwillexceedlifeofonemillionrevolutions.
Notwithstandingthefactthatresponsibilityforbasicdesignofballandrollerbearingsrestswithhebearingmanufacturer,themachinedesignermustformacorrectappreciationofthedutytobeperformedbythebearingandbeconcernednotonlywithbearingselectionbutwiththeconditionsforcorrectinstallation.
Thefitofthebearingracesontotheshaftorontothehousingsisofcriticalimportancebecauseoftheircombinedeffectontheinternalclearanceofthebearingaswellaspreservingthedesireddegreeofinterferencefit.Inadequateinterferencecaninduceserioustroublefromfrettingcorrosion.Theinnerraceisfrequentlylocatedaxiallybyagainstashoulder.Aradiusatthispointisessentialfortheavoidanceofstressconcentrationandballracesareprovidedwitharadiusorchamfertofollowspaceforthis.
Wherelifeisnotthedeterminingfactorindesign,itisusualtodeterminemaximumloadingbytheamounttowhichabearingwilldeflectunderload.Thustheconceptof"staticload-carryingcapacity"isunderstoodtomeantheloadthatcanbeappliedtoabearing,whichiseitherstationaryorsubjecttoslightswivelingmotions,withoutimpairingitsrunningqualitiesforsubsequentrotationalmotion.Thishasbeendeterminedbypracticalexperienceastheloadwhichwhenappliedtoabearingresultsinatotaldeformationof0.0025mmforaball25mmindiameter.
Thesuccessfulfunctioningofmanybearingsdependsuponprovidingthemwithadequateprotectionagainsttheirenvironment,andinsomecircumstancestheenvironmentmustbeprotectedfromlubricantsorproductsofdeteriorationofthebearingdesign.Moreover,sealswhichareappliedtomovingpartsforanypurposeareofinteresttotribologistsbecausetheyarecomponentsofbearingsystemsandcanonlybedesignedsatisfactorilyonbasisoftheappropriatebearingtheory.
Notwithstandingtheirimportance,theamountofresearcheffortthathasbeendevotedtotheunderstandingofthebehaviorofsealshasbeensmallwhencomparedwiththatdevotedtootheraspectsofbearingtechnology.
Lathes
Lathesarewidelyusedinindustrytoproduceallkindsofmachinedparts.Somearegeneralpurposemachines,andothersareusedtoperformhighlyspecializedoperations.
Enginelathes
Enginelathes,ofcourse,aregeneral-purposemachineusedinproductionandmaintenanceshopalloverthetheworld.Sizedrangerfromsmallbenchmodelstohugeheavydutypiecesofequipment.Manyofthelargerlathescomeequippedwithattachmentsnotcommonlyfoundintheordinaryshop,suchasautomaticshopforthecarriage.
TracerorDuplicatingLathes
Thetracerorduplicatinglatheisdesignedoproduceirregularlyshapedpartsautomatically.Thebasicoperationofthislatheisasfallows.Atemplateofeitheraflatorthree-dimensionalshapeisplacedinaholder.Aguideorpointerthenmovesalongthisshapeanditsmovementcontrolsthatofthecuttingtool.Theduplicationmayincludeasquareortaperedshoulder,grooves,tapers,andcontours.Worksuchasmotorshafts,spindles,pistons,rods,caraxles,turbineshafts,andavarietyofotherobjectscanbeturnedusingthistypeoflathe.
TurretLathes
Whenmachiningacomplexworkpieceonageneral-purposelathe,agreatdealoftimeisspentchangingandadjustingtheseveraltoolsthatareneededtocompletethework.Oneofthefirstadaptationsoftheenginelathewhichmadeitsuitabletomassproductionwastheadditionofmulti-toolinplaceofthetailstock.Althoughmostturretshavesixstations,somehaveasmanyaseight.
High-productionturretlathesareverycomplicatedmachineswithawidevarietyofpoweraccessories.Theprincipalfeatureofallturretlathes,however,isthatthetoolscanperformaconsecutiveserialsofoperationsinpropersequence.Oncethetoolshavebeensetandadjusted,littleskillisrequiretorunoutduplicateparts.
AutomaticScrewMachine
Screwmachinesaresimilarinconstructiontoturretlathes,exceptthattheirheadsaredesignedtoholdandfeedlongbarsofstock.Otherwise,theirislittledifferentbetweenthem.Botharedesignedformultipletooling,andbothhaveadaptationsforidenticalwork.Originally,theturretlathewasdesignedasachuckinglatheformachiningsmallcasting,forgings,andirregularlyshapedworkpieces.
Thefirstscrewmachinesweredesignedtofeedbarstockandwireusedinmakingsmallscrewparts.Today,however,theturretlatheisfrequentlyusedwithacollectattachment,andtheautomaticscrewmachinecanbeequippedwithachucktoholdcastings.
Thesingle-spindleautomaticscrewmachine,asitsnameimplies,machinesworkononlyonebarofstockatatime.Abar16to20feetlongisfeedthroughtheheadstockspindleandisheldfirmlybyacollect.Themachiningoperationsaredonebycuttingtoolsmountedonthecrossslide.Whenthemachineisinoperation,thespindleandthestockarerotatedatselectedspeedsfordifferentoperations.Ifrequired,rapidreversalofspindledirectionisalsopossible.
Inthesingle-spindleautomaticscrewmachine,aspecificlengthofstockisautomaticallyfedthroughthespindletoamachiningarea.Atthispoint,theturretandcrossslidemoveintopositionandautomaticallyperformwhateveroperationsarerequired.Afterthemachinedpieceiscutoff,stockisagainfedintothemachiningareaandtheentirecycleisrepeated.
Multiple-spindleautomaticscrewmachineshavefromfourtoeightspindleslocatedaroundaspindlecarrier.Longbarsofstock,supportedattherearofthemachine,passthoughthesehollowspindlesandaregrippedbycollects.Withthesinglespindlemachines,theturretindexesaroundthespindle.Whenonetoolontheturretisworking,theothersarenot.Withamultiplespindlemachine,however,thespindleitselfindex.Thusthebarsofstockarecarriedtothevariousendworkingandsideworkingtools.Eachtooloperatesinonlyoneposition,buttollsoperatesimultaneously.Therefore,fourtoeightworkpiecescanbemachinedatthesametime.
VerticalTurretLathes
Averticalturretisbasicallyaturretlathethathasbeenstoodonitsheadstockend.Itisdesignedtoperformavarietyofturningoperations.Itconsistsofaturret,arevolvingtable,andasideheadwithasquareturretforholdingadditionaltools.Operationsperformedbyanyofthetoolsmountedontheturretorsideheadcanbecontrolledthroughtheuseofstops.
MachiningCenters
Manyoftoday'smoresophisticatedlathesarecalledmachiningcenterssincetheyarecapableofperforming,inadditiontothenormalturningoperations,certainmillinganddrillingoperations.Basically,amachiningcentercanbethoughtofasbeingacombinationturretlatheandmillingmachine.Additionalfeaturesaresometimesincludedbytheversatilityoftheirmachines.
NumericalControl
Oneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol(NC).PriortotheadventofNC,allmachinetoolsweremanuallyoperatedandcontrolled.Amongthemanylimitationsassociatedwithmanualcontrolmachinetools,perhapsnoneismoreprominentthanlimitationofoperatorskills.Withmanualcontrol,thequalityoftheproductisdirectlyrelatedtoandlimitedtotheskillsoftheoperator.Numericalcontrolrepresentsthefirstmajorstepawayfromhumancontrolofmachinetools.
Numericalcontrolmeansthecontrolofmachinetoolsandothermanufacturingsystemsthroughtheuseofprerecorded,writtensymbolicinstructions.Ratherthanoperatingamachinetool,anNCtechniciantooltobenumericallycontrolled,itmustbeinterfacedwithadeviceforacceptinganddecodingtheprogrammedinstructions,knownasareader.
Numericalcontrolwasdevelopedtoovercomethelimitationofhumanoperators,andithasdoneso.Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines,theycanproducepartsmoreuniformly,theyarefaster,andthelong-runtoolingcostsarelower.ThedevelopmentofNCledtothedevelopmentofseveralotherinnovationsinmanufacturingtechnology:
1.Electricaldischargemachining.
2.Lasercutting.
3.Electronbeamwelding.
Numericalcontrolhasalsomademachinestoolsmoreversatilethantheirmanuallyoperat
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