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Development

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Development

    Development

J.Mater.Sci.Techno1.,Vo1.17No.4,2001471

    ;DevelopmentandApplicationofUniversalFormabilityTechnology ;Ya~wuXu

    ;FordMotorCompany,USA

    ;ManuscriptreceivedJune5,2000,inrevisedformNovember8,2000] ;1.Introduction

    ;Usingmathematicalplasticitytheories,universalformability(UF)technologyhasbeendeveloped

    ;andappliedintheautomotivestampingengineeringandproduction.Asaformabilityanalysis

    ;tool,thistechnologyisthemajormethodologyforthedevelopmentofstampingexpertsystem

    ;(solutionprovider)for(a)productdesignandfeasibilityanalysis,(b)materialautomaticselection

    ;usingnomograms,(c)drawdiedesignusingpre-models.and(d)UFandrobustnessanalysisof

    ;dieperformanceinfiniteelementanalysis(FEA)environment. ;Nowadayssheetmetalformingindustryrequires

    ;morenimbleandrobustproceduresfortheengineer

;ingdesignandproductionstabilitycontro1.FEAsim

    ;lllationisusedroutinelyforthedrawdiedesignper

    and-error ;formanceevaluation,butitisstillatrial

    ;procedarewithalimitedrobustnessanalysis--——sev-

    ;eralsimulationshavetoberequiredtodeterminepro- ;cessparameters...——duetotheshortageoffu11descrip- ;tionoftheeaseordifficultyofmakingstampings. ;Therefore.thereremainsaneedforthefurtherforma- ;bilitydevelopment.Thiswillprovideadvancedengi

    ;neeringprinciplesandgeometry/materialdependent

    ;dataforthevirtualmanufacturingprocessinthee

    ;businessenvironmentofstampingindustry. ;2.UniversalFormabilityTechnology

    ;Sheetmetalformingbelongstotheplanestress ;status,whichcanbedescribedinbothstressand ;strainspaces.Duringstamping,either/bothelastic ;or/andplasticdeformationoccur(s)withoneormore ;ofsixtypesofpotentialstampingdefects:(a)spritin ;blank,(b)fractureonblankedge,(c)plasticinsta- ;bility,(d)shapechange(springbackanddistortion), ;(e)lowdeformation,and(f)elasticinstabilitydueto ;residualstress.Seventypesofstampingvariablesare

    ;relatedtothesixtypesofthestampingdefects:(a) ;productgeometry,(b)materialproperty,(c)stamping ;(drawing)process,(d)diesurface,(e)blankshape,(f) ;materialhandling,and(g)miscellaneousfactor.Since ;inter??relationshipsofthestampingdefectsandstamp-- ;ingvariablesarenotfullyclear,thestampingprocess ;isreferredasa”blackbox.’’

    ;Inordertoputlightintothe”blackbox,”theuni—

    ;versalformabilitytechnologyhasbeendeveloped.It ;lmail:xwx0118@hotmail.corn

    ;includesthefollowingcontents:

    ;2.1Formingmodetheory

    ;Basedonphysicalmeaningsofinvariantsof(de- ;viatoric1stressandstraintensors[1l,ausheetmetal ;deformationscai1beclassifiedintosixfotruingmodes ;andsevencriticalpoints.Eachmode/pointhas ;uniquestressandstraincharacteristics.Theydonot ;havegapsoroverlapsinboththestressandstrain ;spaces.Furthermore,thesixformingmodeandseven ;criticalpointsarearrangedasanSshapesequence

    ;diagrambasedonvalueofthefirstinvariantofstress ;tensor.Thistheoryisthefoundationoftheuniver

    ;salformabilitYtechnologyandmechanicscharacteri- ;zationforstampingprocesses.

    ;2.2Universalformabilitytheory

    ;Differenttypesofthestampingdefectshavediffer

    ;entstress/stress(distribution)characteristics.Two ;typesofparameters——geometryandmechanias——de-

    ;scribethecharacteristics.Themechanicsparameters ;arefurtherdividedintotwotypes...——extremeandgra-

    ;dient.Severityofeachtypeofstampingdefectscan ;bedescribedbyuniversalformabilityindexes.Every ;typeofuFindexesincludes(a)oneormoreforming ;modes[2J

    ;,and(b)themechanicsandgeometrypa-

    ;rameters.Asaresult,sixtypesofUFindexesarees- ;tablished:(a)anti-fracturability,(b)shearability,(c) ;anti-wrinklability,(d)shape-fixability,(e)stretchabfl- ;ity,and(f)antibucklability.UsingtheseuFindexes, ;theseverityofallstampingdefectscanbequantita- ;tivelymeasured.

    ;2.3Stampingprocesswindow

    ;Fromthestampingengineeringperspective,all ;stampingvariables,whichareclassifiedintomajors

    ;andminors,mustbekeptincertainrangestomake ;thestampingprocessesmorerobustandnimble.In ;ordertosimplifyengineeringrequirements,partof ;

    ;472J.Mater.Sci.Techno1.,Vo1.17No.4,2001 ;thestampingvariablescapribedeterminedwithsingle ;values,sucha,sthestamping(draw)process.After ;leveragingalltypesofthestampingvariables,major ;parametersofmaterialanddiegeometry,plustheme- ;chanicsandgeometryparametersthatarethesa~rD.eas ;theUFindexes,areselectedtodescribethestamping ;processwindow.SPWincludesthreesub-windows———

    ;tooling,material,andmechanicswindows.AIIsub- ;windowscallbemeasuredinbothphysical(circlegrid ;analysis)andnumerical(FEA)envixonments.SPWis ;usedfor(a)therobustnessanalysisandmeasurement ;ofdrawdieperformance,and(b)productionstability ;contro1.

    ;2.4Controlprinciplesofmetalflowtendency ;Usingtheformingmodeanduniversalformability ;theories,twotypesofCPMFTshavebeendeveloped: ;thefundamentalandapplicationones.Theformers

    ;axeusedfortheanalysisofstress/straingradients; ;thelattersareappliedforthedrawdiesurfacedesign. ;BothcaD.beusedforthestampingproblemsolving. ;2.5Deformationmechanismmodels

    ;Dieradiicontrolmetalflow.Basedonstressdis- ;tributionsalongradiussections,therearetwotypesof ;radii2Dand3D.The2Dradiihastwofunctions:

    ;(a)toidentifyelasticorplasticdeformationinthe ;stageofinitialstampingprocesses,and(b)toadjust ;metalflowamountduringplasticdeformation.Using ;thedieradius,sheetmetalthickness,stressstates, ;anddeformationprocedures,thirty.six(36)deforma- ;tionmechanismmodels,whichcoverall2Dradii,have ;beendeveloped.Asforthe3Dradii,itexistsonlyin ;thestageofplasticdeformationduringstamping.It ;carlbedescribedwithprocessmodelsdevelopedbv ;YoshidataJ.

    ;2Dand3Dradiiareusedfor(a)product

    ;anddiesurfacedesign,and(b)metalflowcontro1. ;2.6Universalformabilitysimilaritytheory ;Therearetwotypesofsimilaritiesduringstamp- ;inganalysis:(a)stampingvariablesimilarity,which

    ;meansthatoneormorestampingvariablescanbe ;simulatedinasimulationprocedure;andfb1me. ;chanicsvariablesimilarity,whichmea3-/sthatmechaD. ;-

    ;icsparameters,describedby

    ;anddeformationmechanism

    ;boththeformingmodes

    ;parametersshownbyei-

    ;ther2Ddeformationmechanismmodelsor3Dprocess ;models,caD.besimulatedinasimulationprocedure. ;Sixtypesofsimulationmethodsareavailable:(a) ;mechanicstest,(b)formingoperation(2Dand3D) ;test[

    ;,(c)finiteelementanalysis,(d)prototyping, ;(e)softtool,and(f)industrialtest.Differentsimu- ;lationmethodscanachievedifferentsimilaritylevels. ;Whenthesimilaritylevelisdetermined,asimulation ;methodcanbeselectedforthesimulationprocedure. ;Thistheoryisusedfor(a)characterizationanalysisof ;productgeometry,(b)selectionofsimulationmethod, ;and(c)pre-modelizationofdiedesign,and(d)archi- ;tecturedesignofstampingexpertsystem.

;3.Application

    ;Theuniversalformabilitytechnologyhasbeenap- ;pliedfortheautomotivedieengineeringandproduc- ;tion.Usingthistechnology,aprototypeofstamping ;expertsystemhasbeendevelo.ped.Theexpertsystem ;includesfourroodtries:(a)productfeasibilityanal- ;ysis,(b)materialselectionusingnomograms[5],(c) ;drawdiedesignusingpremodels,and(d)stamping ;CAE.SuchsystemcaD.achievefullfunctionsthrough ;combiningboththeinformationtechnology(IT)and ;knowledgebasedengineering(KBE)inthee-business ;environments.

    ;4.Conclusions

    ;(1)Theuniversalformabilitytechnologyhasbeen ;developed.Itcan(a)fullymeasuretheedgeordif- ;ficultyofmakingstampingsregardingalltypesof ;stampingdefects,(b)guideproductandtoolingde- ;sign,(c)selectsheetmetals,(d)establishrobustness ;shownbySPWs,and(e)solvestampingproblemsin ;bothengineeringandproductionphases.

    ;(2)Thetechnologyhasbeenpartiallyappliedfor ;automotivestampingengineeringandproduction.It

    ;canbefullyappliedforthedevelopmentofstamping ;exper~systemsforthesheetmetalformingindustry. ;REFERENCES

    ;l1ZongrenwANGeta1.:Fundamenta/ofPlasticWork- ;ingMechanics,NationalDefensePress,Beijing,1989. ;(inChinese)

    ;J2lY.Xu:EStuttgart,1997.

    ;I3IK.Y0shida:inFormability2000A.D.,ASTMSympo- ;slum,Chicago,1980.

    ;14iK.Gubkin:MetalPlasticDeformation(translatedinto ;Chinese),NationalIndustryPress,Beijing,1963. ;I5IY.XuandX.Chen:Material?rjndowDatabasefor

    ;StampingAnalysis,IDDRG,AnnArbor,2000. ;

    ;

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