车辆工程汽车离合器的外文文献翻译Word格式.docx
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车辆工程汽车离合器的外文文献翻译Word格式.docx
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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·
p[Wm2]。
wherepisthethepressurecalculatedasaratiooftheforceandthecontactingsurface。
Astheceramictabletsareplacedattwodifferentradiialongtheclutchdisk,theheatgeneratedmustbecalculatedseparatelyforeachradii。
Slidingcanbedividedintotwosections。
Inthefirstsection,theceramicsideiskeptinastationarypositionbybraking,meanwhiletheaxialloadisincreased;
thereforecompressionchangesinthecourseoftimewhilethespeeddifferencebetweenthetwosidesisconstant。
Inthesecondsection(atsynchronization)thespeeddifferenceisequalizedwhiletheforcevalueisconstant,sovelocitychangesintime.Onthebasisthereof,theheatgeneratedis
.
Thenominalcontactareaistheaggregateofthecontactingsurfacesofthe24and18ceramictabletsonthegivenring.Thediameterofceramictabletsis:
。
Calculationswereperformedfortheloadcasetobecharacterizedbythefollowingparameters:
Basedonexperimentalmeasurementsaconstantfrictioncoefficientof0.4wasestablished.
Thevelocitycanbecalculat
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