拉深模设计中拉深壁起皱的分析毕业课程设计外文文献翻译、中英翻译、外文翻译

1ANANALYSISOFDRAWWALLWRINKLINGINASTAMPINGDIEDESIGNFKCHENANDYCLIAODEPARTMENTOFMECHANICALENGINEERING,NATIONALTAIWANUNIVERSITY,TAIPEI,TAIWANWRINKLINGTHATOCCURSINTHESTAMPINGOFTAPEREDSQUARECUPSANDSTEPPEDRECTANGULARCUPSISINVESTIGATEDACOMMONCHARACTERISTICOFTHESETWOTYPESOFWRINKLINGISTHATTHEWRINKLESAREFOUNDATTHEDRAWWALLTHATISRELATIVELYUNSUPPORTEDINTHESTAMPINGOFATAPEREDSQUARECUP,THEEFFECTOFPROCESSPARAMETERS,SUCHASTHEDIEGAPANDBLANKHOLDERFORCE,ONTHEOCCURRENCEOFWRINKLINGISEXAMINEDUSINGFINITEELEMENTSIMULATIONSTHESIMULATIONRESULTSSHOWTHATTHELARGERTHEDIEGAP,THEMORESEVEREISTHEWRINKLING,ANDSUCHWRINKLINGCANNOTBESUPPRESSEDBYINCREASINGTHEBLANKHOLDERFORCEINTHEANALYSISOFWRINKLINGTHATOCCURREDINTHESTAMPINGOFASTEPPEDRECTANGULARCUP,ANACTUALPRODUCTIONPARTTHATHASASIMILARTYPEOFGEOMETRYWASEXAMINEDTHEWRINKLESFOUNDATTHEDRAWWALLAREATTRIBUTEDTOTHEUNBALANCEDSTRETCHINGOFTHESHEETMETALBETWEENTHEPUNCHHEADANDTHESTEPEDGEANOPTIMUMDIEDESIGNFORTHEPURPOSEOFELIMINATINGTHEWRINKLESISDETERMINEDUSINGFINITEELEMENTANALYSISTHEGOODAGREEMENTBETWEENTHESIMULATIONRESULTSANDTHOSEOBSERVEDINTHEWRINKLEFREEPRODUCTIONPARTVALIDATESTHEACCURACYOFTHEFINITEELEMENTANALYSIS,ANDDEMONSTRATESTHEADVANTAGEOFUSINGFINITEELEMENTANALYSISFORSTAMPINGDIEDESIGNKEYWORDSDRAWWALLWRINKLESTAMPINGDIESTEPPEDRECTANGULARCUPTAPEREDSQUARECUPS1INTRODUCTIONWRINKLINGISONEOFTHEMAJORDEFECTSTHATOCCURINTHESHEETMETALFORMINGPROCESSFORBOTHFUNCTIONALANDVISUALREASONS,WRINKLESAREUSUALLYNOTACCEPTABLEINAFINISHEDPARTTHEREARETHREETYPESOFWRINKLEWHICHFREQUENTLYOCCURINTHESHEETMETALFORMINGPROCESSFLANGEWRINKLING,WALLWRINKLING,ANDELASTICBUCKLINGOFTHEUNDEFORMEDAREAOWINGTORESIDUALELASTICCOMPRESSIVESTRESSESINTHEFORMINGOPERATIONOFSTAMPINGACOMPLEXSHAPE,DRAWWALLWRINKLINGMEANSTHEOCCURRENCEOFWRINKLESINTHEDIECAVITYSINCETHESHEETMETALINTHEWALLAREAISRELATIVELYUNSUPPORTEDBYTHETOOL,THEELIMINATIONOFWALLWRINKLESISMOREDIFFICULTTHANTHESUPPRESSIONOFFLANGEWRINKLESITISWELLKNOWNTHATADDITIONALSTRETCHINGOFTHEMATERIALINTHEUNSUPPORTEDWALLAREAMAYPREVENTWRINKLING,ANDTHISCANBEACHIEVED2INPRACTICEBYINCREASINGTHEBLANKHOLDERFORCEBUTTHEAPPLICATIONOFEXCESSIVETENSILESTRESSESLEADSTOFAILUREBYTEARINGHENCE,THEBLANKHOLDERFORCEMUSTLIEWITHINANARROWRANGE,ABOVETHATNECESSARYTOSUPPRESSWRINKLESONTHEONEHAND,ANDBELOWTHATWHICHPRODUCESFRACTUREONTHEOTHERTHISNARROWRANGEOFBLANKHOLDERFORCEISDIFFICULTTODETERMINEFORWRINKLESOCCURRINGINTHECENTRALAREAOFASTAMPEDPARTWITHACOMPLEXSHAPE,AWORKABLERANGEOFBLANKHOLDERFORCEDOESNOTEVENEXISTINORDERTOEXAMINETHEMECHANICSOFTHEFORMATIONOFWRINKLES,YOSHIDAETAL1DEVELOPEDATESTINWHICHATHINPLATEWASNONUNIFORMLYSTRETCHEDALONGONEOFITSDIAGONALSTHEYALSOPROPOSEDANAPPROXIMATETHEORETICALMODELINWHICHTHEONSETOFWRINKLINGISDUETOELASTICBUCKLINGRESULTINGFROMTHECOMPRESSIVELATERALSTRESSESDEVELOPEDINTHENONUNIFORMSTRESSFIELDYUETAL2,3INVESTIGATEDTHEWRINKLINGPROBLEMBOTHEXPERIMENTALLYANDANALYTICALLYTHEYFOUNDTHATWRINKLINGCOULDOCCURHAVINGTWOCIRCUMFERENTIALWAVESACCORDINGTOTHEIRTHEORETICALANALYSIS,WHEREASTHEEXPERIMENTALRESULTSINDICATEDFOURTOSIXWRINKLESNARAYANASAMYANDSOWERBY4EXAMINEDTHEWRINKLINGOFSHEETMETALWHENDRAWINGITTHROUGHACONICALDIEUSINGFLATBOTTOMEDANDHEMISPHERICALENDEDPUNCHESTHEYALSOATTEMPTEDTORANKTHEPROPERTIESTHATAPPEAREDTOSUPPRESSWRINKLINGTHESEEFFORTSAREFOCUSEDONTHEWRINKLINGPROBLEMSASSOCIATEDWITHTHEFORMINGOPERATIONSOFSIMPLESHAPESONLY,SUCHASACIRCULARCUPINTHEEARLY1990S,THESUCCESSFULAPPLICATIONOFTHE3DDYNAMIC/EXPLICITFINITEELEMENTMETHODTOTHESHEETMETALFORMINGPROCESSMADEITPOSSIBLETOANALYSETHEWRINKLINGPROBLEMINVOLVEDINSTAMPINGCOMPLEXSHAPESINTHEPRESENTSTUDY,THE3DFINITEELEMENTMETHODWASEMPLOYEDTOANALYSETHEEFFECTSOFTHEPROCESSPARAMETERSONTHEMETALFLOWCAUSINGWRINKLESATTHEDRAWWALLINTHESTAMPINGOFATAPEREDSQUARECUP,ANDOFASTEPPEDRECTANGULARPARTATAPEREDSQUARECUP,ASSHOWNINFIG1A,HASANINCLINEDDRAWWALLONEACHSIDEOFTHECUP,SIMILARTOTHATEXISTINGINACONICALCUPDURINGTHESTAMPINGPROCESS,THESHEETMETALONTHEDRAWWALLISRELATIVELYUNSUPPORTED,ANDISTHEREFOREPRONETOWRINKLINGINTHEPRESENTSTUDY,THEEFFECTOFVARIOUSPROCESSPARAMETERSONTHEWRINKLINGWASINVESTIGATEDINTHECASEOFASTEPPEDRECTANGULARPART,ASSHOWNINFIG1B,ANOTHERTYPEOFWRINKLINGISOBSERVEDINORDERTOESTIMATETHEEFFECTIVENESSOFTHEANALYSIS,ANACTUALPRODUCTIONPARTWITHSTEPPEDGEOMETRYWASEXAMINEDINTHEPRESENTSTUDYTHECAUSEOFTHEWRINKLINGWASDETERMINEDUSINGFINITEELEMENTANALYSIS,ANDANOPTIMUMDIEDESIGNWASPROPOSEDTOELIMINATETHEWRINKLESTHEDIE3DESIGNOBTAINEDFROMFINITEELEMENTANALYSISWASVALIDATEDBYOBSERVATIONSONANACTUALPRODUCTIONPARTSKETCHESOFAATAPEREDSQUARECUPSKETCHESOFBASTEPPEDRECTANGULARCUPFIG12FINITEELEMENTMODELTHETOOLINGGEOMETRY,INCLUDINGTHEPUNCH,DIEANDBLANKHOLDER,WEREDESIGNEDUSINGTHECADPROGRAMPRO/ENGINEERBOTHTHE3NODEAND4NODESHELLELEMENTSWEREADOPTEDTOGENERATETHEMESHSYSTEMSFORTHEABOVETOOLINGUSINGTHESAMECADPROGRAMFORTHEFINITEELEMENTSIMULATION,THETOOLINGISCONSIDEREDTOBERIGID,ANDTHECORRESPONDINGMESHESAREUSEDONLYTODEFINETHETOOLINGGEOMETRYANDARENOTFORSTRESSANALYSISTHESAMECADPROGRAMUSING4NODESHELLELEMENTSWASEMPLOYEDTOCONSTRUCTTHEMESHSYSTEMFORTHESHEETBLANKFIGURE2SHOWSTHEMESHSYSTEMFORTHECOMPLETESETOFTOOLINGANDTHESHEETBLANKUSEDINTHESTAMPINGOFATAPEREDSQUARECUPOWINGTOTHESYMMETRICCONDITIONS,ONLYAQUARTEROFTHESQUARECUPISANALYSEDINTHESIMULATION,THESHEETBLANKISPUTONTHEBLANKHOLDERANDTHEDIEISMOVEDDOWNTOCLAMPTHESHEETBLANKAGAINSTTHEBLANKHOLDERTHEPUNCHISTHENMOVEDUPTODRAWTHESHEETMETALINTOTHEDIECAVITYINORDERTOPERFORMANACCURATEFINITEELEMENTANALYSIS,THEACTUALSTRESSSTRAINRELATIONSHIPOFTHESHEETMETALISREQUIREDASPARTOFTHEINPUTDATAINTHEPRESENTSTUDY,SHEETMETALWITHDEEPDRAWINGQUALITYISUSEDINTHESIMULATIONSATENSILETESTHASBEENCONDUCTEDFORTHESPECIMENSCUTALONGPLANESCOINCIDINGWITHTHEROLLINGDIRECTION0ANDATANGLESOF45AND90TOTHEROLLINGDIRECTIONTHEAVERAGEFLOWSTRESS,CALCULATEDFROMTHEEQUATION（024590）/4,FOREACHMEASURED4TRUESTRAIN,ASSHOWNINFIG3,ISUSEDFORTHESIMULATIONSFORTHESTAMPINGSOFTHETAPEREDSQUARECUPANDALSOFORTHESTEPPEDRECTANGULARCUPALLTHESIMULATIONSPERFORMEDINTHEPRESENTSTUDYWERERUNONANSGIINDIGO2WORKSTATIONUSINGTHEFINITEELEMENTPROGRAMPAMFSTAMPTOCOMPLETETHESETOFINPUTDATAREQUIREDFORTHESIMULATIONS,THEPUNCHSPEEDISSETTO10MS_1ANDACOEFFICIENTOFCOULOMBFRICTIONEQUALTO01ISASSUMEDFIG2FINITEELEMENTMESHFIG3THESTRESSSTRAINRELATIONSHIPFORTHESHEETMETAL3WRINKLINGINATAPEREDSQUARECUPASKETCHINDICATINGSOMERELEVANTDIMENSIONSOFTHETAPEREDSQUARECUPISSHOWNINFIG1AASSEENINFIG1A,THELENGTHOFEACHSIDEOFTHESQUAREPUNCHHEAD2WP,THEDIECAVITYOPENING2WD,ANDTHEDRAWINGHEIGHTHARECONSIDEREDASTHECRUCIALDIMENSIONSTHATAFFECTTHEWRINKLINGHALFOFTHEDIFFERENCEBETWEENTHEDIMENSIONSOFTHEDIECAVITYOPENINGANDTHEPUNCHHEADISTERMEDTHEDIEGAPGINTHEPRESENTSTUDY,IEGWDWPTHEEXTENTOFTHERELATIVELYUNSUPPORTEDSHEET5METALATTHEDRAWWALLISPRESUMABLYDUETOTHEDIEGAP,ANDTHEWRINKLESARESUPPOSEDTOBESUPPRESSEDBYINCREASINGTHEBLANKHOLDERFORCETHEEFFECTSOFBOTHTHEDIEGAPANDTHEBLANKHOLDERFORCEINRELATIONTOTHEOCCURRENCEOFWRINKLINGINTHESTAMPINGOFATAPEREDSQUARECUPAREINVESTIGATEDINTHEFOLLOWINGSECTIONS31EFFECTOFDIEGAPINORDERTOEXAMINETHEEFFECTOFDIEGAPONTHEWRINKLING,THESTAMPINGOFATAPEREDSQUARECUPWITHTHREEDIFFERENTDIEGAPSOF20MM,30MM,AND50MMWASSIMULATEDINEACHSIMULATION,THEDIECAVITYOPENINGISFIXEDAT200MM,ANDTHECUPISDRAWNTOTHESAMEHEIGHTOF100MMTHESHEETMETALUSEDINALLTHREESIMULATIONSISA380MM380MMSQUARESHEETWITHTHICKNESSOF07MM,THESTRESSSTRAINCURVEFORTHEMATERIALISSHOWNINFIG3FIG4WRINKLINGINATAPEREDSQUARECUPG50MMTHESIMULATIONRESULTSSHOWTHATWRINKLINGOCCURREDINALLTHREETAPEREDSQUARECUPS,ANDTHESIMULATEDSHAPEOFTHEDRAWNCUPFORADIEGAPOF50MMISSHOWNINFIG4ITISSEENINFIG4THATTHEWRINKLINGISDISTRIBUTEDONTHEDRAWWALLANDISPARTICULARLYOBVIOUSATTHECORNERBETWEENADJACENTWALLSITISSUGGESTEDTHATTHEWRINKLINGISDUETOTHELARGEUNSUPPORTEDAREAATTHEDRAWWALLDURINGTHESTAMPINGPROCESS,ALSO,THESIDELENGTHOFTHEPUNCHHEADANDTHEDIECAVITYOPENINGAREDIFFERENTOWINGTOTHEDIEGAPTHESHEETMETALSTRETCHEDBETWEENTHEPUNCHHEADANDTHEDIECAVITYSHOULDERBECOMESUNSTABLEOWINGTOTHEPRESENCEOFCOMPRESSIVETRANSVERSESTRESSESTHEUNCONSTRAINEDSTRETCHINGOFTHESHEETMETALUNDERCOMPRESSIONSEEMSTOBETHEMAINCAUSEFORTHEWRINKLINGATTHEDRAWWALLINORDERTOCOMPARETHERESULTSFORTHETHREEDIFFERENTDIEGAPS,THERATIOOFTHETWOPRINCIPALSTRAINSISINTRODUCED,6BEINGMIN/MAX,WHEREMAXANDMINARETHEMAJORANDTHEMINORPRINCIPALSTRAINS,RESPECTIVELYHOSFORDANDCADDELL5HAVESHOWNTHATIFTHEABSOLUTEVALUEOFISGREATERTHANACRITICALVALUE,WRINKLINGISSUPPOSEDTOOCCUR,ANDTHELARGERTHEABSOLUTEVALUEOF,THEGREATERISTHEPOSSIBILITYOFWRINKLINGTHEVALUESALONGTHECROSSSECTIONMNATTHESAMEDRAWINGHEIGHTFORTHETHREESIMULATEDSHAPESWITHDIFFERENTDIEGAPS,ASMARKEDINFIG4,AREPLOTTEDINFIG5ITISNOTEDFROMFIG5THATSEVEREWRINKLESARELOCATEDCLOSETOTHECORNERANDFEWERWRINKLESOCCURINTHEMIDDLEOFTHEDRAWWALLFORALLTHREEDIFFERENTDIEGAPSITISALSONOTEDTHATTHEBIGGERTHEDIEGAP,THELARGERISTHEABSOLUTEVALUEOFCONSEQUENTLY,INCREASINGTHEDIEGAPWILLINCREASETHEPOSSIBILITYOFWRINKLINGOCCURRINGATTHEDRAWWALLOFTHETAPEREDSQUARECUP32EFFECTOFTHEBLANKHOLDERFORCEITISWELLKNOWNTHATINCREASINGTHEBLANKHOLDERFORCECANHELPTOELIMINATEWRINKLINGINTHESTAMPINGPROCESSINORDERTOSTUDYTHEEFFECTIVENESSOFINCREASEDBLANKHOLDERFORCE,THESTAMPINGOFATAPEREDSQUARECUPWITHDIEGAPOF50MM,WHICHISASSOCIATEDWITHSEVEREWRINKLINGASSTATEDABOVE,WASSIMULATEDWITHDIFFERENTVALUESOFBLANKHOLDERFORCETHEBLANKHOLDERFORCEWASINCREASEDFROM100KNTO600KN,WHICHYIELDEDABLANKHOLDERPRESSUREOF033MPAAND198MPA,RESPECTIVELYTHEREMAININGSIMULATIONCONDITIONSAREMAINTAINEDTHESAMEASTHOSESPECIFIEDINTHEPREVIOUSSECTION（ANINTERMEDIATEBLANKHOLDERFORCEOF300KNWASALSOUSEDINTHESIMULATION）THESIMULATIONRESULTSSHOWTHATANINCREASEINTHEBLANKHOLDERFORCEDOESNOTHELPTOELIMINATETHEWRINKLINGTHATOCCURSATTHEDRAWWALLTHEVALUESALONGTHECROSSSECTIONCOMPAREDWITHONEANOTHERFORTHESTAMPINGPROCESSESWITHBLANKHOLDERFORCEOF100KNAND600KNTHESIMULATIONRESULTSINDICATETHATTHE_VALUESALONGTHECROSSSECTIONMNAREALMOSTIDENTICALINBOTHCASESINORDERTOEXAMINETHEDIFFERENCEOFTHEWRINKLESHAPEFORTHETWODIFFERENTBLANKHOLDERFORCES,FIVECROSSSECTIONSOFTHEDRAWWALLATDIFFERENTHEIGHTSFROMTHEBOTTOMTOTHELINEMN,ASMARKEDINFIG4,AREPLOTTEDINFIG6FORBOTHCASESITISNOTEDFROMFIG6THATTHEWAVINESSOFTHECROSSSECTIONSFORBOTHCASESISSIMILARTHISINDICATESTHATTHEBLANKHOLDERFORCEDOESNOTAFFECTTHEOCCURRENCEOFWRINKLINGINTHESTAMPINGOFATAPEREDSQUARECUP,BECAUSETHEFORMATIONOFWRINKLESISMAINLYDUETOTHELARGEUNSUPPORTEDAREAATTHEDRAWWALLWHERELARGECOMPRESSIVETRANSVERSESTRESSESEXISTTHEBLANKHOLDERFORCEHASNOINFLUENCEONTHEINSTABILITYMODEOFTHEMATERIALBETWEENTHE7PUNCHHEADANDTHEDIECAVITYSHOULDERDISTANCEMMFIG5VALUEALONGTHECROSSSECTIONMNFORDIFFERENTDIEGAPSFIG6CROSSSECTIONLINESATDIFFERENTHEIGHTSOFTHEDRAWWALLFORDIFFERENTBLANKHOLDERFORCESA100KNB600KN4STEPPEDRECTANGULARCUPINTHESTAMPINGOFASTEPPEDRECTANGULARCUP,WRINKLINGOCCURSATTHEDRAWWALLEVENTHOUGHTHEDIEGAPSARENOTSOSIGNIFICANTFIGURE1BSHOWSASKETCHOFAPUNCHSHAPEUSEDFORSTAMPINGASTEPPEDRECTANGULARCUPINWHICHTHEDRAWWALLCISFOLLOWEDBYASTEPDEANACTUALPRODUCTIONPARTTHATHASTHISTYPEOFGEOMETRYWASEXAMINEDINTHEPRESENTSTUDYTHEMATERIALUSEDFORTHISPRODUCTIONPARTWAS07MMTHICK,ANDTHESTRESSSTRAINRELATIONOBTAINEDFROMTENSILETESTSISSHOWNINFIG3THEPROCEDUREINTHEPRESSSHOPFORTHEPRODUCTIONOFTHISSTAMPINGPARTCONSISTSOFDEEPDRAWINGFOLLOWEDBYTRIMMINGINTHEDEEPDRAWINGPROCESS,NODRAWBEADISEMPLOYEDONTHEDIESURFACETOFACILITATETHEMETALFLOWHOWEVER,OWINGTOTHESMALLPUNCHCORNERRADIUSANDCOMPLEXGEOMETRY,ASPLITOCCURREDATTHETOPEDGEOFTHEPUNCHANDWRINKLESWEREFOUNDTOOCCURATTHEDRAWWALLOFTHEACTUALPRODUCTIONPART,ASSHOWNINFIG7ITISSEENFROMFIG7THATWRINKLESAREDISTRIBUTEDONTHEDRAW8WALL,BUTAREMORESEVEREATTHECORNEREDGESOFTHESTEP,ASMARKEDBYADANDBEINFIG1BTHEMETALISTORNAPARTALONGTHEWHOLETOPEDGEOFTHEPUNCH,ASSHOWNINFIG7,TOFORMASPLITFIG7SPLITANDWRINKLESINTHEPRODUCTIONPARTFIG8SIMULATEDSHAPEFORTHEPRODUCTIONPARTWITHSPLITANDWRINKLESINORDERTOPROVIDEAFURTHERUNDERSTANDINGOFTHEDEFORMATIONOFTHESHEETBLANKDURINGTHESTAMPINGPROCESS,AFINITEELEMENTANALYSISWASCONDUCTEDTHEFINITEELEMENTSIMULATIONWASFIRSTPERFORMEDFORTHEORIGINALDESIGNTHESIMULATEDSHAPEOFTHEPARTISSHOWNFROMFIG8ITISNOTEDFROMFIG8THATTHEMESHATTHETOPEDGEOFTHEPARTISSTRETCHEDSIGNIFICANTLY,ANDTHATWRINKLESAREDISTRIBUTEDATTHEDRAWWALL,SIMILARTOTHOSEOBSERVEDINTHEACTUALPARTTHESMALLPUNCHRADIUS,SUCHASTHERADIUSALONGTHEEDGEAB,ANDTHERADIUSOFTHEPUNCHCORNERA,ASMARKEDINFIG1B,ARECONSIDEREDTOBETHEMAJORREASONSFORTHEWALLBREAKAGEHOWEVER,9ACCORDINGTOTHERESULTSOFTHEFINITEELEMENTANALYSIS,SPLITTINGCANBEAVOIDEDBYINCREASINGTHEABOVEMENTIONEDRADIITHISCONCEPTWASVALIDATEDBYTHEACTUALPRODUCTIONPARTMANUFACTUREDWITHLARGERCORNERRADIISEVERALATTEMPTSWEREALSOMADETOELIMINATETHEWRINKLINGFIRST,THEBLANKHOLDERFORCEWASINCREASEDTOTWICETHEORIGINALVALUEHOWEVER,JUSTASFORTHERESULTSOBTAINEDINTHEPREVIOUSSECTIONFORTHEDRAWINGOFTAPEREDSQUARECUP,THEEFFECTOFBLANKHOLDERFORCEONTHEELIMINATIONOFWRINKLINGWASNOTFOUNDTOBESIGNIFICANTTHESAMERESULTSAREALSOOBTAINEDBYINCREASINGTHEFRICTIONORINCREASINGTHEBLANKSIZEWECONCLUDETHATTHISKINDOFWRINKLINGCANNOTBESUPPRESSEDBYINCREASINGTHESTRETCHINGFORCESINCEWRINKLESAREFORMEDBECAUSEOFEXCESSIVEMETALFLOWINCERTAINREGIONS,WHERETHESHEETISSUBJECTEDTOLARGECOMPRESSIVESTRESSES,ASTRAIGHTFORWARDMETHODOFELIMINATINGTHEWRINKLESISTOADDDRAWBARSINTHEWRINKLEDAREATOABSORBTHEREDUNDANTMATERIALTHEDRAWBARSSHOULDBEADDEDPARALLELTOTHEDIRECTIONOFTHEWRINKLESSOTHATTHEREDUNDANTMETALCANBEABSORBEDEFFECTIVELYBASEDONTHISCONCEPT,TWODRAWBARSAREADDEDTOTHEADJACENTWALLS,ASSHOWNINFIG9,TOABSORBTHEEXCESSIVEMATERIALTHESIMULATIONRESULTSSHOWTHATTHEWRINKLESATTHECORNEROFTHESTEPAREABSORBEDBYTHEDRAWBARSASEXPECTED,HOWEVERSOMEWRINKLESSTILLAPPEARATTHEREMAININGWALLTHISINDICATESTHENEEDTOPUTMOREDRAWBARSATTHEDRAWWALLTOABSORBALLTHEEXCESSMATERIALTHISIS,HOWEVER,NOTPERMISSIBLEFROMCONSIDERATIONSOFTHEPARTDESIGN10FIG9DRAWBARSADDEDTOTHEDRAWWALLSONEOFTHEADVANTAGESOFUSINGFINITEELEMENTANALYSISFORTHESTAMPINGPROCESSISTHATTHEDEFORMEDSHAPEOFTHESHEETBLANKCANBEMONITOREDTHROUGHOUTTHESTAMPINGPROCESS,WHICHISNOTPOSSIBLEINTHEACTUALPRODUCTIONPROCESSACLOSELOOKATTHEMETALFLOWDURINGTHESTAMPINGPROCESSREVEALSTHATTHESHEETBLANKISFIRSTDRAWNINTOTHEDIECAVITYBYTHEPUNCHHEADANDTHEWRINKLESARENOTFORMEDUNTILTHESHEETBLANKTOUCHESTHESTEPEDGEDEMARKEDINFIG1BTHEWRINKLEDSHAPEISSHOWNINFIG10THISPROVIDESVALUABLEINFORMATIONFORAPOSSIBLEMODIFICATIONOFDIEDESIGNFIG10WRINKLEFORMEDWHENTHESHEETBLANKTOUCHESTHESTEPPEDEDGE11FIG11CUTOFFOFTHESTEPPEDCORNERFIG12SIMULATEDSHAPEFORTHEMODIFIEDDIEDESIGNANINITIALSURMISEFORTHECAUSEOFTHEOCCURRENCEOFWRINKLINGISTHEUNEVENSTRETCHOFTHESHEETMETALBETWEENTHEPUNCHCORNERRADIUSAANDTHESTEPCORNERRADIUSD,ASINDICATEDINFIG1BTHEREFOREAMODIFICATIONOFDIEDESIGNWASCARRIEDOUTINWHICHTHESTEPCORNERWASCUTOFF,ASSHOWNINFIG11,SOTHATTHESTRETCHCONDITIONISCHANGEDFAVOURABLY,WHICHALLOWSMORESTRETCHTOBEAPPLIEDBYINCREASINGTHESTEPEDGESHOWEVER,WRINKLESWERESTILLFOUNDATTHEDRAWWALLOFTHECUPTHISRESULTIMPLIESTHATWRINKLESAREINTRODUCEDBECAUSEOFTHEUNEVENSTRETCHBETWEENTHEWHOLEPUNCHHEADEDGEANDTHEWHOLESTEPEDGE,NOTMERELYBETWEENTHEPUNCHCORNERANDTHESTEPCORNERINORDERTOVERIFYTHISIDEA,TWOMODIFICATIONSOFTHEDIEDESIGNWERESUGGESTEDONEISTOCUTTHEWHOLESTEPOFF,ANDTHEOTHERISTOADDONEMOREDRAWINGOPERATION,THATIS,TODRAWTHEDESIREDSHAPEUSINGTWODRAWING12OPERATIONSTHESIMULATEDSHAPEFORTHEFORMERMETHODISSHOWNINFIG12SINCETHELOWERSTEPISCUTOFF,THEDRAWINGPROCESSISQUITESIMILARTOTHATOFARECTANGULARCUPDRAWING,ASSHOWNINFIG12ITISSEENINFIG12THATTHEWRINKLESWEREELIMINATEDINTHETWOOPERATIONDRAWINGPROCESS,THESHEETBLANKWASFIRSTDRAWNTOTHEDEEPERSTEP,ASSHOWNINFIG13ASUBSEQUENTLY,THELOWERSTEPWASFORMEDINTHESECONDDRAWINGOPERATION,ANDTHEDESIREDSHAPEWASTHENOBTAINED,ASSHOWNINFIG13BITISSEENCLEARLYINFIG13BTHATTHESTEPP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