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外文翻译--研究汽车液压过程散热器的个部件的作用 英文版.pdf

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外文翻译--研究汽车液压过程散热器的个部件的作用 英文版.pdf

StudyonthehydroformingprocessforautomobileradiatorsupportmembersMunYongLeea,,SungManSohna,ChangYoungKangb,SangYongLeecaSungWooHitechCo.Ltd.,Pusan619731,SouthKoreabPukyungNationalUniversity,PusanSan100,SouthKoreacKoreaInstituteofMachineryandMaterials,Changwon641830,SouthKoreaAbstractTubularhydroformingwasusedtomanufactureradiatorsupportmembersthatsupportradiatorcomponentssuchasaradiatorandacoolingfan,whichisplacedinfrontofcarbody.Newtooldesignconceptnamedmechanicalcamslidingsystemwasintroducedforthepreformingprocessinwhichastartingtubewassimultaneouslyprebendedandnarrowedtoapproximatelyfitthepartshape.Sinceirreversiblewrinklesappearatthebendedregionduringpreformingwithoutinternalpressure,preformingwasperformedafterinternalpressureC24150barwasaddedintothetube.Fromhydroformingtests,itwasknownthatradiatorsupportmemberswerehydroformedattheinternalpressurerangingfrom420to780bar.However,radius20Rofthecorneratrectangularsectionofthepartsshowedlargerthandesignspecification10R.Inordertoinvestigatethestrainhardeningeffectsofthehydroformedparts,tensilepropertiesofthepartshydroformedat420barwerecomparedtothoseofstartingtubes.Throughthisinvestigation,itwasrevealedthattensilestressofhydroformedpartswasincreasedby22.1,whereaselongationofthesepartswasreducedby49.7.Concerningthefunctionofthispart,itisbelievedthatthesectionalshapeandthesetensilevaluesareenoughtoassembleandsupporttheradiatormembers.However,becausetoolwearanddamageoccurringinthepreformingofastartingtubeevidentlyresultindeterioratingdimensionalreproducibility,itisnecessarytosolvethisproblemassociatedwithmechanicalcamslidingsystemwhenconsideringmassproductionofthispart.Inthispaper,thehydroformingprocessofradiatorsupportmembersincludingnewtooldesignconceptwasdescribedindetailandtestresultswereprovidedtoshowhydroformingpossibilityforradiatorsupportmembers.KeywordsHydroformingAutomobileradiatorPreforming1.IntroductionRecentautomobiletechnologiesarefocusedonthedevelopmentoflowemissionandhighperformancevehicles,whichcouldbesuccessfullyrealizedbyreducingtheweightofvehicleswithoutanysacrificeofvehiclesafety.Accordingly,designcriteriaassociatedwithacarbodyandachassishavebeenvariedtoprovidemaximumstiffness,dimensionalstability,fatiguelifeandcrashworthinesswithminimummassandcost.Inordertoachievethesegoals,hydroformingtechnologiesarebeingcurrentlyusedorconsideredtomanufactureseveralautomotivepartsincludedincarbodysystems,chassissystemsandpowertrainsystems1.Inparticular,tubularhydroforming,whichmakesonestepformingofcomplexclosedhollowpartspossible,iseffectivelyusedforhighvolumeapplicationinautomotiveindustrybecausevariousclosedsectionsresultinginthehighestbendingandtorsionalstiffnesssectionalshapecanbeeasilyformedbyuseofthistechnology.ThatisthereasonwhyavarietyofhighvolumeautomotivepartshavebeenhydroformedinEuropeancountriesandtheUS.Inthisviewpoint,hydroformingtechnologieswillbecomemorepopulartomanufacturehighlyengineeredpartscharacterizedbylightweightandhighquality2,3.However,consideringtheapplicationofhydroformingtechnologiesinautomotiveparts,itshouldbealsonotedthatthereareseveralproblemsrelatedtotooldesignanddevicesaswellastheestablishmentoftheoptimumprocessingparameters.Furthermore,sinceautomotivepartshavevariousdifferentdesignshapesaccordingtoautomobilemakersJournalofMaterialsProcessingTechnology130–1312002115–120Correspondingauthor.andtypes,optimumtooldesignandprocessparameterscannotbeunitedasacommontechnologicalstandard.Therefore,whenapartisplannedtodevelopusinghydroforming,thetooldesignandoptimumprocessparameteraswellasthepossibilityofhydroformingshouldbeonlydeterminedbydirecthydroformingtrialsfortheintendedrealparts.Thisstudywascarriedouttocheckthehydroformingpossibilityofarealpart,aradiatorsupportmember,whichisusuallymanufacturedbystampingofsheetmetalsandweldingofstampedparts.2.Experimentalprocedureforhydroformingofradiatorsupportmembers2.1.ExaminationofhydroformabilityforatubematerialSinceradiatorsupportmembersareastructuralcomponent,whichsupportsbothofaradiatorandacoolingfanlocatedinfrontofacarbody,therequirementforthispartisonlyconsideredasstaticstrengthensuringsafesupport.Therefore,whenatubeissubstitutedforaconventionalweldedstructurehavingclosedsection,itispossibletoreducethethicknessofthepartduetohigherstrengthinducedbystrainhardeningaftertubeformingprocess.However,inthisstudy,tubethicknesskeptthesamelevelasthethickness1mmoftheconventionalmembertoavoidtheproblemrelatedtosealing,whichmayoccurwhenthethicknessofthememberisreduced.ThetubematerialusedforthisstudyisahotrolledplateforautomobilestructureSAE1010.Thisplatewasrolledalonglongitudinaldirectionandweldedtomaketubeshapeandthenextrudedtofitthefinalsize.Mechanicalpropertiesaftereachprocess,whichisperformedtoobtainastartingtubeforhydroforming,aresummarizedinTable1.Yieldstressandelongationofasreceivedplateswere32.2kgf/mm2and42.8,respectively.However,aftertubinganddrawing,yieldstresswasreducedto29.2kg/mm2andelongationwasincreasedto43.7,whichwasduetosubsequentannealingtreatment.Accordingly,itwasconfirmedthatstartingtubeshavegoodpropertiesforhydroforming.AccordingtomaindesignfactorsforhydroformingofradiatorsupportmembersdescribedinTable2,itwasexpectedthatthispartcouldbecompletelyformedatbelow1000barwithoutfeeding.Inaddition,comparingforminglimitdiagramFLDtothestraindistributionofahydroformedpartobtainedbyFEManalysisFig.1,itwasassumedthatthepartcouldbesafelyhydroformedwithoutTable1MechanicalpropertiesaftereachprocessforhydroformingofradiatorsupportmembersSAE1010Tensilestresskgf/mm2Yieldstresskgf/mm2ElongationAsreceived41.732.242.8Aftertubing40.935.140.2Afterdrawing37.529.243.7Afterhydroforming45.844.822.0Table2HydroformingdesignfactorsofradiatorsupportmembersFactorsHydroformingstampingSPECmmC31603C2thickness10C21390Expansionratio7MinimumRmm10Internalpressurebar1000FeedingmmNoPresst1000Weightkg1.752.7Thenumberofsubpartsea12Fig.1.ResultsofFEManalysisforhydroformingprocessofaradiatorsupportmemberanddistributionofstrainintheFLDcourtesyHyundaiMotorsCo.Ltd.aafrontviewofdiesetforhydroformingofradiatorsupportmembersbasideviewofdiesetforhydroformingofradiatorsupportmembers.116M.Y.Leeetal./JournalofMaterialsProcessingTechnology130–1312002115–120anyriskresultedfromseverelylocalizedstrain.However,duringrealhydroformingtrials,alotoffailuresoccurredonthebendedregionsofthepartindicatedbyFig.1.Thereasonforfrequentfailuresmaybeassociatedwiththeprestrainsinducedbytheprebendingbeforefinalhydroforming,whichleadstoseverelocalthinningduringfinalforming.Finally,anattentionneedstobepaidregardingthehydroformingadvantageofthispartasdescribedinTable2,theweightandthenumberofsubpartsisreducedusinghydroformingcomparedtotheconventionalparts.2.2.ToolsystemforhydroformingofradiatorsupportmembersUnliketheconventionalhydroforming,inwhichthepreformingispreviouslyconductedbyuseofseparatetools,thetoolusedforthisstudywasspeciallydesignedtodoboththepreformingandthehydroformingwithasingletool.Inparticular,itisnotedthatmechanicalcamslidingsystemwasusedfortubenarrowing,inwhichthecrosssectionalshapeinatubechangesfromcirculartypetoellipticaltype.Fig.2illustratestheschematictooloperatingconcept.Asshowninthisfigure,prebendingiscompletedbydieclosingwhiletheslidersassembledatthebottomdiearelaterallymovedtonarrowatube.Accordingly,thepreformingforthispartwasautomaticallyfinishedwhendieisclosed.Afterthedieiscompletelyclosed,hydroformingisdonetoexpansethepreformedtubebyfeedingthefluid.Duringhydroformingprocess,thecrosssectionalshapeofthepreformedpartwasfittofinaldesignshaperectangularshape.Finally,whenhydroformingisfinishedandupperdieislifted,bothslidersareautomaticallyreturntooriginalpositionbyspringforceandthenthehydroformedpartcanbeeasilyejectedwithoutanyinterferencebetweenapartanddiecavity.Withthisuniquetool,realpartswerehydroformedusing2500thydraulicpress,asshowninFig.3.Sincetheinternalpressureneededforhydroformingofthispartwasevaluatedasbelow1000barthroughpreviousFEMsimulation,itwasassumedthat2500tpresshasenoughcapacityforthistest.2.3.HydroformingofradiatorsupportmembersVariousinternalpressuresfrom420to780barwereusedforhydroformingtrialsofaradiatorsupportmember.Sincealotoftubeswererupturedattheinternalpressureof780barduringhydroforming,internalpressurewasgraduallydiminisheduntil420bar.Byobservingtheexternalappearanceofhydroformedparts,itcouldbefoundthattheparthydroformedattheinternalpressureof420barshowsthealmostsameshapecomparedtotheparthydroformedatthehigherinternalpressureof780bar.Therefore,theinternalpressureof420baristheoptimumvaluetobuildaradiatorsupportmemberusinghydroformingwithouttheriskoftubeburstFig.4.Ofcourse,somecurvedregionsatcornerofthepartwerenotcompletelysatisfiedwithdesignFig.2.Schematicdiagramshowingbasictooloperatingconceptaasupperdieisdescending,astartingtubeisbendedtofitintothediecavitynotespeciallydesignedclampingdevice,wasusedtoavoidsealingproblemthatmayoccurwhentheendregionofthetubeisrotatedbythebendingmomentbasupperdieisdescending,slidersarelaterallymovedtonarrowatube.Lateralmotionofslidersisachievedbythecontactbetweenthesidefacesofslidersandupperdiehavingthematedgradientprofilewitheachothermechanicalcamslidingsystem.M.Y.Leeetal./JournalofMaterialsProcessingTechnology130–1312002115–120117specificationFig.5.However,sincetheseregionsdonotseriouslyinfluencedonthesubsequentassemblingofthispart,itisbelievedthatthedesignspecificationmaybeeasilychangedtopermitthedimensionofthesehydroformedparts.Thereisonethingtobenotedtheinternalpressureofaround150barwaspreviouslyaddedjustbeforethepreformingbecauseirreversiblewrinklesappearedatthebendedregionwithouttheinternalpressureduringthepreformingprocess.Fig.5representsthedetailedhistoryoftheinternalpressureusedforhydroformingoftheseparts.Accordingly,thisprocessissomewhatdifferentfromtheconventionalhydroformingprocesses,inwhichmechanicalpreformingsuchasbendingandnarrowingisperformedinseparatetoolsandformingdeviceswithoutinternalpressure4,5.3.Hydroformingtestresults3.1.SomeproblemsassociatedwithhydroformingprocessesFig.6ashowshydroformedpartshavingincompleteexternalshapeattheupperregionofbothendsintheparts.Moreover,itwasdiscoveredthatmostofthefailuresduringhydroformingoccurredattheseregions.Therefore,itseemsthatthesepositionsweresufferedfromveryseverelocaldeformationcausedbytheprebending.Fig.6bandcshowtwopartsforthecomparisonofexternalshapeoneupperpartwashydroformedafterprebendingwithinternalpressureandtheotherlowerpartwashydroformedafterprebendingwithoutinternalpressure.Fromthecomparisonoftheseparts,itwasknownthatthelattershowedseverewrinklesonthesurface,whichcouldnotberecoveredbyhighinternalpressureexertedonthesubsequenthydroFig.3.Hydroformingdeviceusedforthisstudyabasiclayoutforhydroformingdevicepresscapacity2500tbrealapparatusequippedwithdiesetforhydroformingofradiatorsupportmembers.Fig.4.Thechangeofinternalpressuresduringtubularhydroformingnoteinternalpressureof150barwasexertedonthetubeduringpreformingprocessandthenvariousfinalformingpressureswerereached.Fig.5.Comparisonofcrosssectionaldimensionbetweendesignspecificationandrealpartsadesignspecificationbrealpartshydroformedattheinternalpressureof420bar.Realpartshavelargerradiusateachcornerthandesignspecification.However,sinceflattenareaofeachsideisenoughtoweldotherpartsonthismember,thisdimensionaldifferencemaybepermitted.118M.Y.Leeetal./JournalofMaterialsProcessingTechnology130–1312002115–120

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