1、附录英语翻译LUBRICATIONANDJOURNALBEARINGS1IntroductionAbearingcanbedefinedasamemberspecificallydesignedtosupportmovingmachinecomponents/Themostcommonbearingapplicationisthesupportofarotatingshaftwhichistransmittingpowerfromonelocationtoanother；oneexampleisthecrankshaftbearingsofautomaticengine；anotherexam
2、pleistheshaftbearingsusedalltypesofelectricmotors/Sincethereisalwaysrelativemotionbetweenabearinganditsmatingsurface/frictionisinvolved/Inmanyinstances/suchasthedesignofpulleys/brakesandclutches/frictionisdesirable/However/inthecaseofbearings/thereductionoffrictionisoneofprimeconsiderations/friction
3、resultsinlossofpower/generationofheatandwearofmatingsurfaces/Journalandantifrictionbearingsarethetwogeneraltypesofbearingsexistence/Journalbearingsoperatewithslidingcontact/whereasantifrictionbearingsexperiencepredominantlyrollingcontact/Theamountofslidingfrictioninjournalbearingsdependsonthesurface
4、finishes/materials/slidingvelocitiesandthetypeoflubricantused/Theprinciplemotion-retardingeffectinantifrictionbearingsiscalledrollingresistanceratherthanrollingfriction/Thisissobecausetheresistanceofmotionisessentiallyduetothedeformationoftherollingelementsand/hence/itisnotaslidingphenomenon/Antifri
5、ctionbearingswillbeinchapter1/4/Toreducetheproblemsassociatedwithslidingfrictioninjournalbearings/alubricantisusedinconjunctionwithcompatiblematingmaterials/Whenselectingthelubricantandmatingmaterials/onemusttakeintoaccountbearingpressures/temperaturesandrubbingvelocities/Theprinciplefunctionofthelu
6、bricantinslidingcontactbearingsistopreventphysicalcontactbetweentherubbingsurfaces/Thusthemaintenanceofanoilfilmundervaryingloads/speedsandtemperatureistheprimeconsiderationinslidingcontactbearings/2TheoryofFrictionFrictionistheresistanceonepartexertsonasecondpartwhenrelativeslidingmotionoccursorisa
7、ttempted/Thusfrictiontakesplacewhenevertwosurfacesrubtogether/Thecauseoffrictionistheinevitableinterlockingofthetinyirregularitiesofthetwomatingsurfaces/Aforceisrequiredtodeformthetinypeaksandvalleystopermitmotion/WhenablockofweightWrestsonahorizontalfixedsurface/aforcePisappliedtotheblock/Initially
8、/Pequalszero/butitsvalueconstantlyincreasesasafunctionoftime/Duetofriction/aforceFiscreatedbetweenblockandfixedsurface/Thedirectionofthefrictionalforce/F/isoppositethatofP/becausefrictionalwaysopposesmotionorattemptedmotion/Alsonotethatthenormalforce/N/actingperpendiculartothematingsurfaceisequaland
9、oppositetotheweight/W/oftheblock/RollingContactBearingsTheconcernofamachinedesignerwithballandrollerbearingsisfivefoldasfollows/(a)lifeinrelationtoload；(b)stiffness/i/e/deflectionsunderload；(c)friction；(d)wear；(e)noise/Formoderateloadsandspeedsthecorrectselectionofastandardbearingonthebasisofloadrat
10、ingwillbecomeimportantwhereloadsarehigh/althoughthisisusuallyoflessmagnitudethanthatoftheshaftsorothercomponentsassociatedwiththebearing/Wherespeedsarehighspecialcoolingarrangementsbecomenecessarywhichmayincreasefrictionaldrag/Wearisprimarilyassociatedwiththeintroductionofcontaminants/andsealingarra
11、ngementsmustbechosenwithregardtothehostilityoftheenvironment/Becausethehighqualityandlowpriceofballandrollerbearingsdependsonquantityproduction/thetaskofthemachinedesignerbecomesoneofselectionratherthandesign/Rolling-contactbearingsaregenerallymadewithsteelwhichisthrough-hardenedtoabout900HV/althoug
12、hinmanymechanismsspecialracesarenotprovidedandtheinteractingsurfacesarehardenedtoabout600HV/Itisnotsurprisingthat/owingtothehighstressesinvolved/apredominantformoffailureshouldbemetalfatigue/andagooddealofworkisbasedonacceptedvaluesoflifeanditisgeneralpracticeinthebearingindustrytodefinetheloadcapac
13、ityofthebearingasthatvaluebelowwhich90percentofabatchwillexceedalifeofonemillionrevolutions/Notwithstandingthefactthatresponsibilityforthebasicdesignofballandrollerbearingsrestswiththebearingmanufacturer/themachinedesignermustformacorrectappreciationofthedutytobeperformedbythebearingandbeconcernedno
14、tonlywithbearingselectionbutwiththeconditionsforcorrectinstallation/Thefitofthebearingracesontotheshaftorontothehousingsisofcriticalimportancebecauseoftheircombinedeffectontheinternalclearanceofthebearingaswellaspreservingthedesireddegreeofinterferencefit/Inadequateinterferencecaninduceserioustroubl
15、efromfrettingcorrosion/Theinnerraceisfrequentlylocatedaxiallybyabuttingagainstashoulder/Aradiusatthispointisessentialfortheavoidanceofstressconcentrationandballracesareprovidedwitharadiusorchamfertoallowspaceforthis/Wherelifeisnotthedeterminingfactorindesign/itisusualtodeterminemaximumloadingbytheam
16、ounttowhichabearingwilldeflectunderload/Thustheconceptof“staticload-carryingcapacity”isunderstoodtomeantheloadthatcanbeappliedtoabearing/whichiseitherstationaryorsubjecttoslightswivelingmotions/withoutimpairingitsrunningqualitiesforsubsequentrotationalmotion/Thishasbeendeterminedbypracticalexperienc
17、eastheloadwhichwhenappliedtoabearingresultsinatotaldeformationoftherolling-elementdiameter/Thiswouldcorrespondtoapermanentdeformationof0/0025mmforaball25mmindiameter/Thesuccessfulfunctioningofmanybearingsdependsuponprovidingthemwithadequateprotectionagainsttheirenvironment/andinsomecircumstancesthee
18、nvironmentmustbeprotectedfromlubricantsorproductsofdeteriorationofthebearingdesign/Moreover/sealswhichareappliedtomovingpartsforanypurposeareofinteresttotribologistsbecausetheyarecomponentsofbearingsystemsandcanonlybedesignedsatisfactorilyonthebasisoftheappropriatebearingtheory/Notwithstandingtheiri
19、mportance/theamountofresearcheffortthathasbeendevotedtotheunderstandingofthebehaviorofsealshasbeensmallwhencomparedwiththatdevotedtootheraspectsofbearingtechnology/NumericalControlOneofthemostfundamentalconceptsintheareaofadvancedmanufacturingtechnologiesisnumericalcontrol(NC)/PriortotheadventofNC/a
20、llmachinetoolsweremanuallyoperatedandcontrolled/Amongthemanylimitationsassociatedwithmanualcontrolmachinetools/perhapsnoneismoreprominentthanthelimitationofoperatorskills/Withmanualcontrol/thequalityoftheproductisdirectlyrelatedtoandlimitedtotheskillsoftheoperator/Numericalcontrolrepresentsthefirstm
21、ajorstepawayfromhumancontrolofmachinetools/Numericalcontrolmeansthecontrolofmachinetoolsandothermanufacturingsystemsthroughtheuseofprerecorded/writtensymbolicinstructions/Ratherthanoperatingamachinetool/anNCtechnicianwritesaprogramthatissuesoperationalinstructionstothemachinetool/Foramachinetooltobe
22、numericallycontrolled/itmustbeinterfacedwithadeviceforacceptinganddecodingtheprogrammedinstructions/knownasareader/Numericalcontrolwasdevelopedtoovercomethelimitationofhumanoperators/andithasdoneso/Numericalcontrolmachinesaremoreaccuratethanmanuallyoperatedmachines/theycanproducepartsmoreuniformly/t
23、heyarefaster/andthelong-runtoolingcostsarelower/ThedevelopmentofNCledtothedevelopmentofseveralotherinnovationsinmanufacturingtechnology/1/Electricaldischargemachining/2/Lasercutting/3/Electronbeamwelding/Numericalcontrolhasalsomademachinetoolsmoreversatilethantheirmanuallyoperatedpredecessors/AnNCma
24、chinetoolcanautomaticallyproduceawidevarietyofparts/eachinvolvinganassortmentofwidelyvariedandcomplexmachiningprocesses/Numericalcontrolhasallowedmanufacturerstoundertaketheproductionofproductsthatwouldnothavebeenfeasiblefromaneconomicperspectiveusingmanuallycontrolledmachinetoolsandprocesses/Likeso
25、manyadvancedtechnologies/NCwasborninthelaboratoriesoftheMassachusettsInstituteofTechnology/TheconceptofNCwasdevelopedintheearly1950swithfundingprovidedbytheU/S/Airforce/Initsearlieststages/NCmachineswereabletomakestraightcutsefficientlyandeffectively/However/curvedpathswereaproblembecausethemachinet
26、oolhadtobeprogrammedtoundertakeaseriesofhorizontalandverticalstepstoproduceacurve/Theshorteristhestraightlinesmakingupthesteps/thesmootheristhecurve/Eachlinesegmentinthestepshadtobecalculated/Thisproblemledtothedevelopmentin1959oftheAutomaticallyProgrammedTools(APT)language/Thisisaspecialprogramming
27、languageforNCthatusesstatementssimilartoEnglishlanguagetodefinethepartgeometry/describethecuttingtoolconfiguration/andspecifythenecessarymotions/ThedevelopmentoftheAPTlanguagewasamajorstepforwardinthefurtherdevelopmentofNCtechnology/TheoriginalNCsystemswerevastlydifferentfromthoseusedtoday/Themachineshadhardwiredlogiccircuits/Theinstructionalprogramswerewrittenonpunched
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