翻译冲压载荷对椭圆深冲汽车零部件产品的影响.docx
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翻译冲压载荷对椭圆深冲汽车零部件产品的影响.docx
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翻译冲压载荷对椭圆深冲汽车零部件产品的影响
附录
Effectsofpunchloadforellipticaldeepdrawingproduct
ofautomotiveparts
DongHwanPark&PrasadK.D.V.Yarlagadda
Abstract:
Deepdrawingprocess,oneofsheetmetalformingmethods,isveryusefulinindustrialfieldbecauseofitsefficiency.Theproductionofoptimalproductsusingthis
processisdependentontheprocessvariablessuchasblankshapes,profileradiiofpunchanddie,andformabilityofmaterials.Ofthevariables,theblankshapeisveryimportantsinceitcontrolstheformabilityfactor.
Thispaperreportstheinvestigationsonthreekindsofblankshapesandthescribedcircletestonthreedeformationmodes.Thepunchloaddistributionforellipticalformingprocessesweremeasuredunderdifferentconditionsofprofileradiiofpunchanddieanddiscussedhere.Theseexperimentsclarifiedtheinfluenceoftheprofileradiiofthepunchanddieandtheblankshapeonthepunch-loaddistributionfortheellipticaldeepdrawingproductofautomobileparts.Theaimofthisstudyistoinvestigatetheeffectthattheprocessvariableshaveondrawabilityinanon-axisymmetricellipticaldeep-drawingprocessandtoobtainusefuldatafromtheindustrialfield.
Keywords:
Deep-drawingproccss.Blankshape.Punchload.Profileradii.Punchstroke.Processvariables.
1.Introduction
Thesheet-metalformingprocesseshaveanimportantroleinindustriessuchasautomobile,airplane,andelectricapplianceduetotheiradvantagesinreducingdevelopmenttimeandfinalcostoftheproducts.
Ingeneral,sheet-metalformingmayinvolvestretching,drawing,repetitionofbendingandunbendingorvariouscombinationsofthesebasicmodesofdeformation.Manystudiesontheprocessvariablesofcylindricalproductshavebeencarriedoutregardingthefundamentalsofdeepdrawingprocess.Thus,manyshapessuchasrectangular,ellipticalandnon-axisymmetricalhavebeenproduced.
Ingeneral,mostoftheresearchfordeep-drawingprocesshasaddressedtheformabilityofaxisymmetricalshapes,buttherehavebeenfewstudiesdoneontheformabilityofellipticalshapes.
Sheetmetalcandeformonlytoacertainlevelbeforealocalizedzoneofthinningorneckingoccurs.Thislevelisdependentmainlyonthecombinationoftheratioofmajorandminorstrains.Keeler(1965)firstintroducedtheforminglimitdiagram(FLD).Keeler'sworkwaslimitedtoconditionsofbiaxialstretching,i.e.whenbothmajorandminorprincipalsurfacestrainswerepositive.Goodwin(1968)extendedKeeler'sworktoincludethetension-compressionprincipalstrainregion.ThiscombineddiagramisnowwellknownastheKeeler-Goodwinforminglimitdiagram[1].
TheFLDiswidelyusedinindustryasaguideontheformabilityofsheetmetaldeformationprocesses.Inordertoobtaintheoptimumellipticaldeep-drawingproductwithanon-axisymmetricshape,manyprocessvariablessuchasmaterialproperty,profileradiiofpunchanddie,lubricationcondition,ramspeed,blankholdingforce(BHF),clearance,andsoonmustbeconsideredbeforethedrawabilityoftheproductcanbedetermined.Besides,profileradiiofpunchanddieandblankshapearethemostimportantvariablesthatinfluencetheformabilityindeepdrawingprocess[2-4].Theformabilityofthedeep-drawingprocesscanbepromoted,andleadtimeandcostcanbereducedbychoosingbothappropriateprofileradiiofapunchanddieandblankshapeforthedeep-drawingprocess[5-6].
Theformabilityofnon-axisymmetricshapeshasbeenexploredunderthepressconditionsthattheblanksizeisdifferentbetweenthemajorandminoraxesandthatthematerialflowisnon-uniform.Itisimportanttochangetheblankshape,becauseablankcomesintocontactwiththedie.
Astheareaofcontactincreasesbetweentheblankholderandthedie,theblankholdingforceandthepunchforceincrease.Thisisareasonforformingdefectsbyincreaseddeformationresistance.Tosolvethisdefect,manystudiesintotheshapeofblankshavebeenperformedincircularandrectangulardeepdrawing,buttherehavenotbeensufficientstudiesconcerningtheshapeofblanksinellipticaldeepdrawing[7-22].Inthisstudy,theprofileradiiofpunchanddieandblankshapesinfluenceonformabilityintheellipticaldeepdrawingprocesshasbeeninvestigatedbyanalyzingthepunchloaddistribution.
2.Deep-drawingexperiment
2.1Experimentalmaterial
ThematerialusedwasSECD(KS:
Koreanstandards)withhighqualityformabilityandathicknessof1.6mm.Thiswasgalvanizedwith20μmofzinc.Tensiletestswerecarriedoutinthedirectionsof0,45,and900totherollingdirection.Thegaugelengthandwidthofthetensilespecimenswere25and50mm,respectively.ThemechanicalpropertyinthetensiledirectionisindicatedinTable1.Thespecimensforthetensiletestswerecutbyawire-electricsparkmachineandbasedontheKSB0801No.5.ThetensilestrengthofthespecimenswasmeasuredthroughthetensiletestusingUTMwithsettingloadspeedas10mm/min.
2.2Experimentalequipmentandconditions
Figure1showstheappliedequipment,hydraulicpress(100tons)withadie-cushiontocontroltheblankholdingforceandlimittheswitchtodetermineastrokeofupperramaccordingtotheprocesses.Alsotheequipmenthasacomputerwhichhasalinearvariabledifferentialtransform-er(LVDT).Whenthesteelsheetisformedinthisequipment,theLVDTmeasuresthepunchloadaccordingtopunchstroke.
Table2showstheexperimentalconditionsforprofileradiiofthepunchanddie.Thepunchprofileradius(Rp)wasfixedat6.4mm,thedieprofileradius(Rd)wasselectedbasedonwoconditions.Thepunchstrokefortheexperimentconsistsofthreestrokeswhichare
(1)46mminthefirstprocess;
(2)62mminthesecondprocess;and(3)74mminthethirdprocess.Theblankholdingpressurewasappliedto2N/mmThelubricantfortheoperationofdeepdrawingusedwasasolubleoillubricationforplasticworking.Figure2presentsthediegeometryofthenon-axisymmetricellipticaldeepdrawingprocessusedinthistest.
2.3Scribedcircletest
Theplanedeformationresultingfromtheformationofasheetmetalworkpiececanbemeasuredbyusinganarrayofsmalldiameter(10mm)circles,printedontheblanksurfaceinthecriticalstrainregions.Figure3showsscribedcirclemarksofanon-axisymmetricblank.Thecirclesdeformintovariousshapesduringforming,themajorandminoraxesindicatethedirectionofthemajorandminorprincipalstrains.Likewise,themeasureddimensionsareusedtodeterminethemajorandminorprincipalstrainmagnitudes.Thiscirculargridtechniqueofmeasuringstrainscanbeusedtodiagnosethecausesofneckingandfractureinindustrialpracticeandtoinvestigatewhetherthesedefectswerecausedbyvariationsinthepropertiesofthematerial,wearofthetools,changesinlubrication,orincorrectpresssettings.
Innon-axisymmetricellipticaldeepdrawing,threemodesofformingregimesarefound:
draw,stretch,andplanestrain.Thedrawmodefornon-axisymmetricellipticaldeepdrawingcouldbedefinedwhenthemajorandminorstrainsarepositive.Thestretchmodecouldbedefined
whenthemajorstrainispositiveandminorstrainisnegative,andplanestrainmodecouldbedefinedwhenthemajorstrainispositiveandminorstrainiszero.Figures4,5,and6presentthemajorandminorstraindistributionbyscribedcircletestafterthefirstdrawingaccordingtothe
punchanddieradii.Fromtheresultofthescribedcircletest,thethreedeformationmodesofthemajorandminorstrainsfornon-axisymmetricellipticaldeepdrawingareshowninFig.7.Thewallandflangeofdeformationzonesaremainlyappliedtothedrawmode,thepunchheadisappliedtotheplanestrainmode,andthecornerisappliedtothestretchmode.
Fig.3Scribedcirclemarksofnon-axisymmetricblank
3Blankshapedesign
Generally,thetrial-and-errormethodbasedontheexperiencesofskilledtoolmakers,whichincreasestheamountoftimeandcosts,hasbeentriedfordevelopingtheblankshape.Therefore,inthisstudy,inordertodesigntheblankshapewhichisequivalenttothesurfaceareaofthefinal
product,wecalculatedthesurfaceareaofthefinalproductbymeansofthree-dimensionalmodeling[4–6].Weusedthreekindsofblanks,whichhaveanequivalentsurfaceareatothefinalproduct.Figure8showsthegeometryofshapes.TheoutlineofthetypeAblankislargerthanthetypeBandCblanks.TheshortsidelengthofthetypeBblankissmallerthanthetypeCblank.Ontheotherhand,thelongsidelengthofthetypeBblankisalittlelargerthanthetypeCblank.Theprocessoftheappliedproductintheexperimentconsistsofsevenstagesofthedeepdrawingprocessandthreestagesoftrimming,restrikingetc.So,thetotalnumberofmulti-deepdrawingstagesis10.Inthisstudy,theexperimenttomeasurepunchloadwasperformedfromthefirstprocesstothethirdprocess.Figure9showstheproductshapeofeachtypeblankaccordingtoprocess.
4Resultanddiscussions
Figure10showsthecomparisonofthepunchloadalongtheblanktypesinthefirstprocess.Thepunchprofileradius(Rp)wasfixedat6.4mm,thedieprofileradius(Rd1)ofthefirsprocesswasselectedundertwoconditions,11.2and16mmAsanon-axisymmetricblankdrawsinthediecavity,theinitialpunchloadincreasedrapidlycausinginflowresistanceofthelongandshortsidesandthenthemaximumpunchloadismeasuredas55%ofthepunchstroke.Afterthemaximumpunchload,theloadwasreducedandthenformingwascompleteduntilthebottomdeadcenter(BDC)ofthepunchstroke.WorkhardeningofthesteelsheeoccurredduetotheincreaseoftheamountofdeformationasthepuncharrivesattheBDCofpunchstroke.Thepunchstrokeis
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