车辆工程汽车离合器的外文文献翻译.docx

车辆工程汽车离合器的外文文献翻译.docx

《车辆工程汽车离合器的外文文献翻译.docx》由会员分享，可在线阅读，更多相关《车辆工程汽车离合器的外文文献翻译.docx（9页珍藏版）》请在冰豆网上搜索。

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.

.

Thevelocitycanbecalculat