车辆工程汽车离合器的外文文献翻译.docx
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车辆工程汽车离合器的外文文献翻译.docx
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车辆工程汽车离合器的外文文献翻译
湖北文理学院
毕业设计(论文)英文翻译
题目
有限元热分析的陶瓷离合器
专业
车辆工程
班级
Xxx
姓名
Xxxx
学号
2010138xx
指导教师
职称
Xxx副教授
2014年2月25日
Fethermalanalysisofaceramicclutch
1.Introduction
Abrasivedryrunningvehicleclutchesareforceclosurecouplings.Torqueandspeedtransmissionareensuredbythefrictionalforcegeneratedbetweentwopressedsurfaces.Reasonsfortheapplicationofceramicasafrictionmediumincludegoodheatandwearresistanceproperties,whichprovidetheopportunitytodrivehigherpressures,andalowdensity.Thus,anincreasingpowerdensityisenabledwithaparallelminimizationofconstructionspace.
MeasurementswithafirstprototypeofaclutchdiskusingceramicfacingswereperformedatKarlsruheUniversityinalaboratoryspecializedinpassengercardrivesystemtesting.Inthecourseofanalysisthefiniteelement(FE)modelwastobeconstructedwiththeknowledgeofmeasurementdataandmeasurementconditions.Calculationswereintendedtodeterminethetemperaturedistributionoftheclutchdiskanditsenvironmentateachmomentintimecorrespondingtomeasurements.Itisessentialtobefamiliarwiththetemperaturerangeinordertoexaminethewearcharacteristicsofthesystem.Thus,importantinformationisderivedfrommeasurementdata.Incriticalloadcases,thehighestexpectedtemperaturesmustbeforecastinspaceandtimeinordertoprotectmeasuringinstrumentsclosetothelocationofheatgeneration.
Thegoalofthisstudyistoanalyzeandmodifytheclutchsystemtoprovidebetteroperatingconditionsbyimprovingtheheatconductionandconvectionofthesystemortoincreasetheamountoftheenergyconvertedintofrictionalheat.Furthermore,itisdesiredtofindbetterdesignsolutionsformoreefficientclutchsystems.
CalculationswereperformedbytheCosmosDesignStarsoftware.Duringmodeldevelopment,greatcarehadtobetakenforpropersimplificationofgeometry,theselectionofelementsizes,andthecorrectadjustmentoftimestepsduetothesubstantialhardwarerequirementsfortransientcalculations.Changesinthermalparameterssuchasthesurfaceheatconvectioncoefficientandthermalloadhadtobetakenintoconsiderationonanon-goingbasisintermsoftimeandlocation.Thetwosidesoftheanalyzedtestclutchsystemcanonlybemanagedbytwoindependentmodelslinkedbyheatpartition,accordingtothehypothesisthatthecontacttemperaturemustbeidenticalonbothsideswhilethereispropercontactbetweenthemanditsvaluemustbeadjustedbyiteration.Calculationsrevealedthattheheatpartitionchangedbycycleanditdifferedalongtheinnerandoutercontactrings.Asaresultofthedifferentcoolingcharacteristicsbetweentheceramicandsteelside,aheatflowislaunchedfromtheceramicsidetothesteelside.Thisheatflowwasalsodeterminedbyiteration,itsvaluealsochangesbycycleanddiffersalongtheinnerandoutercontactrings.
2.Firstprototypeofaclutchusingengineeringceramicsasfrictionmaterial
Theexaminedclutchdiskwasdevelopedaccordingtothe“specificceramic”productdevelopmentprocessestablishedattheInstituteforProductDevelopment(IPEK)attheUniversityofKarlsruhe.Thisdevelopmentprocessalreadyhasthepossibilityforconnectiontoarealtransmissionshaft;further,ithasacushionspringdeviceforthefacingsallowinggoodstartbehaviour.Abrasiveclutchesmustcomplywiththefollowingbasicrequirements:
hightorquetransmissionaccordingtohighfrictioncoefficients,
highcomfort(novibrationsthroughself-inducedchattering),
homogeneoustemperaturedistribution,
lowwearcharacteristic.
Acriticalelementoftheswitchistheabrasivedisk.Withregardtothedesignutmostcaremustbetakentoselecttherightmaterial.Ahighandconstantfrictioncoefficient,,wearresistanceandthermalresistancearedesiredcharacteristics.Theclutchdiskhasinsteadofthegenerallyappliedring-shapedabrasiveinlettworowsofSSIC(assintered)ceramicpellets.Thesepelletsareplacedon6separatesegments.Thesegmentsarefixedtothecentralhubbyrivets.Eachsegmentconsistsof4plates,2workingasfacingspringsand2ascarriers.
3.Measurements
MeasurementswereperformedatthedepartmentofpowertraindevelopmentoftheInstituteforProductDevelopment(IPEK)attheKarlsruheUniversity(TH)ResearchUniversity,whereacategoryIVcomponenttestrigisusedfortestsofnewfrictionalmaterialsandexaminationsofnewmaterialsinrealclutchdisks.Realconditionsareappliedbythesimulationofdrivingresistance(e.g.startingintheplane,startingatthehill).Itisacomponenttestrigleveledonthefourthpositionofthetribologicaltestingenvironment.
Inordertogiveanideaofdimensions:
theequipmentlengthisabout4-5m.Thetwoelectricmotorsandtheaxialforcearecontrolledindependentlybycomputer;therebymanyoperationalstatescanberealized.Thisenablestheequipmenttocompleteamyriadoftribologicalmeasurementsallwhileproperlymodelingtheoperationofaclutchdiskinapassengercar.ItisalsoequippedwithanautomaticITmeasurementsystem.Measurablequantitiesincludethefollowing:
twoheavy-dutyelectricmotors(150KW,BaumullerDS160L-305),
devicesuitableforexertingaxialforce,
torquemeter(MannerSensortelemetrieMF100),
axialforcemeter,
steeldiskinfriction,
replaceableheadtoaffixthedevicetobetested,
temperaturealongtwodifferentradiiat0.4mmbelowtheabrasivesurfaceofthesteeldisk(OmegaHJMTSS-IM100U-150-2000,J-typeiro-constantanthermocouples),
revolutionsperminuteforbothsides(PolyteneLSV065).
Thegreatestchallengeoutoftheseistemperaturemeasurementaswewouldliketoknowthetemperatureoftherevolvingsteeldisk.Thetwothermoelementsplacedinthesteeldiskforwarddatatothecomputerthroughawirelessbluetoothsystemandareplaced0.4mmbelowtheabrasivesurfaceofthesteeldiskonthetwooppositearcsoftheclutchdisk.
3.2.Measurementprocess
Duetocomponentanalysesandcostreductiononlyonesideoftheclutchdiskismountedwithceramicfacings.Thus,theclutchdiskanditsfittingwillbereferredtoastheceramicside,andtheabrasivesteeldiskwithitsenvironmentrevolvingtogetherwillbereferredtoasthesteelside.Inthecourseofmeasurements,datawerecollectedatasamplingfrequencyof100and1000HZ.Measurementswereconductedaccordingtothetimecurves.
Themeasurementstartsbyincreasingtherevolutionsperminuteofthesteelside(thedrivingside)toaspecificvalue(1500rpmhere).Thentheceramicside(thedrivenside),heldatzerorpm,ispushedtowardsthesteeldiskandtheaxialforceisapplieduntiladesignatedvalueisreached(nominally4200Nhere).Uponreachingthedesignatedaxialforcetheceramicsideisreleasedandthetwosidesstarttosynchronize.Afewsecondsaftersynchronization,theaxialloadisdiscontinuedandaftersometimeboththesteelandtheceramicsides—revolvingatthesamespeed—aresloweddown.Thisisdeemedtobeonemeasurementcycle.Tencyclesarecompletedinthecourseofasinglemeasurement.Duringapplicationoftheaxialforcetheceramicsideisheldatzerorpmuntilthedesiredforceisreachedtoensuresynchronizationoccursatnearlythesametimeofeachcycle.Thisisunfavorablefromtheviewpointofbothmeasurementsandcalculations.Measurementsareusuallyconductedbychangingonly3parameters:
thespeed,theaxialloadandtheinertia.Thefollowingfiguresareappliedinvariouscombinations:
speedn:
700,1100and1500(rpm),
axialforceF:
4200,6400and8400(N)and
inertiaI:
1,1.25and1.5(kgm2).
Experimentalmeasurementsarelaunchedwithapprox.10-15minintervals,duringwhichthesystemcoolsdowntoabout30-401C.Thismakescalculationsdifficult,astheexacttemperaturedistributionofthesystemisnotknownatthecommencementofthemeasurement.However,itcanbeassumedthataperiodof10-15minissufficientforanearlyhomogeneoustemperaturedistributiontobeproduced.Theparametersforthefollowingsimulationhavebeenchosenforanintermediatecasewithaspeedn=1500rpm,anaxialforceF=4200NandaninertiaI=1kgm2.
4.Calculationsofheatgeneration
Themechanicalenergyconsumedduringthefrictionoftwobodiesistransformedintoheat.Thegeneratedheatcanbecalculatedbythefollowingsimpleformula:
Q=μ·ν·F[W].
wheremisthethefrictionalcoefficient;vistheslidingvelocity;Fistheforceperpendicularlycompressingthesurfaces.Andtheheatfluxdensitypersurfaceunitisq=μ·ν·p[Wm2].
wherepisthethepressurecalculatedasaratiooftheforceandthecontactingsurface.Astheceramictabletsareplacedattwodifferentradiialongtheclutchdisk,theheatgeneratedmustbecalculatedseparatelyforeachradii.Slidingcanbedividedintotwosections.Inthefirstsection,theceramicsideiskeptinastationarypositionbybraking,meanwhiletheaxialloadisincreased;thereforecompressionchangesinthecourseoftimewhilethespeeddifferencebetweenthetwosidesisconstant.Inthesecondsection(atsynchronization)thespeeddifferenceisequalizedwhiletheforcevalueisconstant,sovelocitychangesintime.Onthebasisthereof,theheatgeneratedis
.
Thenominalcontactareaistheaggregateofthecontactingsurfacesofthe24and18ceramictabletsonthegivenring.Thediameterofceramictabletsis:
.
Calculationswereperformedfortheloadcasetobecharacterizedbythefollowingparameters:
.
Basedonexperimentalmeasurementsaconstantfrictioncoefficientof0.4wasestablished.
.
Thevelocitycanbec
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