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AluminumforAutomotiveBodySheetPanelsContent1Introduction2Propertiesofaluminumalloysforautomotivebodypanelsheet3Designconsiderations4Formingaluminumautobodysheet5Joiningconsiderationsindesign6Finishing7Summary1IntroductionTheuseofaluminumsavesweight,40%to60%comparedtosteel.Manymorealuminumbodypanelsarenowbeingspecifiedforvehiclesattheconceptualdesignstagesothatdesignerscantakeadvantageoftheadditionalweightsavingsindesignofothersystemslikebrakingandsuspension.Aluminumbodysheethasthemajoradvantagethatitcanbehandled,formed,joined,andfinishedinmuchthesamewaysandusinglargelythesameequipmentofandsystemsthatareusetodayforsteelsheetpanels.Thepurposeofthepublicationistoprovidespecificinformationon:Themechanicalproperties,physicalpropertiesandformabilityofthecurrentgenerationofaluminumalloys.Designconsiderations,blankingandforminginformation,andrelevantdiedesignconsiderations.Joiningtechnology,includingspotwelding,fusionwelding,mechanicalfastening,andadhesivebondingtechnologies.Finishingprocess,includingbothconventionalphosphatingandelectro-coating,plusneweralternativemethodsnowbecomingavailable.2PropertiesofaluminumalloysforautomotivebodypanelsheetThreetypesofaluminumalloys:2xxx(Al-Cu)alloys5xxx(Al-Mg)alloys6xxx(Al-Mg-Si)alloyscompositionThetypicalmechanicalandphysicalpropertiesTypicalmechanicalpropertiesTensilepropertyRepresentativepropertiesofaluminumbodysheetalloysfollowingasimulatedPaintbakecycleFormabilitycomparativeRepresentativefatigueproperties3Designconsiderations3.1Dentresistance3.2Paneldeflection3.3Bendingandtorsionalstiffness3.4Flangedesign3.5Vibration3.6Fatigue3.7AluminumdesignmanualAweightsavingsofapproximately40%-50%canbeobtainedsimplybyconvertinganexistingsteeldesigntoasimilardesigninaluminum,whileadesignoptimizedforaluminumhasprovidedweightsavingsupto65%overacomparablesteelpanel.3.1DentresistanceThedentresistanceofanouterpanelisgovernedby:TheyieldstrengthofthematerialThicknessofthepanelTheshapeTheunsupportedpanelareaTherearetwomethodsforcomparingdentperformanceofautomotivebodypanels:Thresholdvelocity—theminimumimpactvelocityrequiredtoinitiateaperceptibledentEquivalentdepthofdent—considerdepthofdentdevelopedincomponentsatagivenvelocityandmassofobject3.2PaneldeflectionForexteriorpanelapplications,deflectionsofthepanelintheimmediatevelocityoftheappliedloadareanimportantdesignconsideration.Typically,thedeflectionofacomponentorsubassemblyunderloadmustbecontrolledtoavoidcontactwithotherparts.Equallyimportantisthe“Feel”,ordeflectionofapanel,whenacustomerappliespressuretoit.Therearetwoapproachesforminimizingthedeflectionofanaluminumassembly.Eithertheouterpanelthicknessisincreased,orthespanbetweeninnerpanelsupportingbeamsisdecreased.Equaldeflectioncanbeobtainedwithanaluminumpanelwithaspan70%theofasteelpanelofequalthickness.Thesecondapproachismuchmoreefficient.Multi-coneorateacupdesign3.3BendingandtorsionalstiffnessBendingandtorsionalstiffnessisdependenton:panelthicknessthegeometryofthecross-sectionbeamthebeampatternThemulti-clonedesign3.4FlangedesignTypically,eitheradown-standingflangeorahemmedflangeisusedforpanelssuchashoodsanddecklids.3.5VibrationThenaturalfrequencyofvibrationforapartinfree-freestateisproportionaltoitsstiffness(k)andisinverselytoitsproportionaltoitsmass(m).Thestiffnessisdependentonboththegeometryofthepanelandthemodulusofelasticityofthematerialused.Thevibrationresponseofaluminumandsteelpartswiththesamegeometryandthicknessinafree-freestateisidentical.3.6FatigueComponentssubjectedtorepeatedloadsshouldbecarefullycheckedforthepossibilityoffatiguefailure.Carefuldesigncaneliminateconcentrationsinhighlystressedareas,therebymakingthemostefficientuseofmaterial.Connections,holesorotherfeaturesthatcauseofstressconcentrationareareasmostsubjecttofatigue.3.7AluminumdesignmanualTheAluminumdesignmanualprovideabroadreferenceofdesignproperties,specificationsandguidelinesforaluminumalloys4Formingaluminumautobodysheet4.1Formabilitycharacteristicsofaluminumalloys4.2Part,tool,andProcessDesignformanufacturability4.3PresssetupThemostcriticalvariablesduringformingare:FormabilitycharacteristicsofthematerialGeometryofthepartandtoolsresultingfromthepartandtooldesignPresssetupincludinglubricationandcontrolofthebinderpressure4.1FormabilitycharacteristicsofaluminumalloysGenerally,deep-drawability,stretchability,andbendabilityarereducedwithrespecttosteel.Testfordeterminingformabilityfallintotwomaingroups:thosewhichmeasurematerialpropertiesandthosewhichattempttosimulateactualpressformingoperations.MaterialtestsTensileBulgeHardnessPlanestraintensileMarciniakBiaxialstretchtestsSimulativetestsBendtest(bending)Stretchbendtest(stretchingandbending)Holeexpansiontest(stretchflanging)Limitingdrawratiotest(shrinkingflange)Yoshidabucklingtest(wrinklingtendencies)Drawbeadtest(frictionevaluation)Swiftcuptest(drawing)Erichsentest(stretching)Limitingdomeheight(LDH)test(stretching)Fukuitest(stretching-drawcombination)Marciniaktest(stretching)Erichsentest(stretching)4.2Part,tool,andProcessDesignformanufacturabilityPunchcontactBlankdevelopm