已阅读5页,还剩2页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
IntJAdvManufTechnol(2002)19:2532592002Springer-VerlagLondonLimitedAnAnalysisofDraw-WallWrinklinginaStampingDieDesignF.-K.ChenandY.-C.LiaoDepartmentofMechanicalEngineering,NationalTaiwanUniversity,Taipei,TaiwanWrinklingthatoccursinthestampingoftaperedsquarecupsandsteppedrectangularcupsisinvestigated.Acommoncharacteristicofthesetwotypesofwrinklingisthatthewrinklesarefoundatthedrawwallthatisrelativelyunsup-ported.Inthestampingofataperedsquarecup,theeffectofprocessparameters,suchasthediegapandblank-holderforce,ontheoccurrenceofwrinklingisexaminedusingfinite-elementsimulations.Thesimulationresultsshowthatthelargerthediegap,themoresevereisthewrinkling,andsuchwrinklingcannotbesuppressedbyincreasingtheblank-holderforce.Intheanalysisofwrinklingthatoccurredinthestampingofasteppedrectangularcup,anactualproductionpartthathasasimilartypeofgeometrywasexamined.Thewrinklesfoundatthedrawwallareattributedtotheunbalancedstretchingofthesheetmetalbetweenthepunchheadandthestepedge.Anoptimumdiedesignforthepurposeofeliminatingthewrinklesisdeterminedusingfinite-elementanalysis.Thegoodagreementbetweenthesimulationresultsandthoseobservedinthewrinkle-freeproductionpartvalidatestheaccuracyofthefinite-elementanalysis,anddemonstratestheadvantageofusingfinite-elementanalysisforstampingdiedesign.Keywords:Draw-wallwrinkle;Stampingdie;Steppedrec-tangularcup;Taperedsquarecups1.IntroductionWrinklingisoneofthemajordefectsthatoccurinthesheetmetalformingprocess.Forbothfunctionalandvisualreasons,wrinklesareusuallynotacceptableinafinishedpart.Therearethreetypesofwrinklewhichfrequentlyoccurinthesheetmetalformingprocess:flangewrinkling,wallwrinkling,andelasticbucklingoftheundeformedareaowingtoresidualelasticcompressivestresses.Intheformingoperationofstamp-ingacomplexshape,draw-wallwrinklingmeanstheoccurrenceCorrespondenceandoffprintrequeststo:ProfessorF.-K.Chen,Depart-mentofMechanicalEngineering,NationalTaiwanUniversity,No.1RooseveltRoad,Sec.4,Taipei,Taiwan10617.E-mail:fkchenL50560.twofwrinklesinthediecavity.Sincethesheetmetalinthewallareaisrelativelyunsupportedbythetool,theeliminationofwallwrinklesismoredifficultthanthesuppressionofflangewrinkles.Itiswellknownthatadditionalstretchingofthematerialintheunsupportedwallareamaypreventwrinkling,andthiscanbeachievedinpracticebyincreasingtheblank-holderforce;buttheapplicationofexcessivetensilestressesleadstofailurebytearing.Hence,theblank-holderforcemustliewithinanarrowrange,abovethatnecessarytosuppresswrinklesontheonehand,andbelowthatwhichproducesfractureontheother.Thisnarrowrangeofblank-holderforceisdifficulttodetermine.Forwrinklesoccurringinthecentralareaofastampedpartwithacomplexshape,aworkablerangeofblank-holderforcedoesnotevenexist.Inordertoexaminethemechanicsoftheformationofwrinkles,Yoshidaetal.1developedatestinwhichathinplatewasnon-uniformlystretchedalongoneofitsdiagonals.Theyalsoproposedanapproximatetheoreticalmodelinwhichtheonsetofwrinklingisduetoelasticbucklingresultingfromthecompressivelateralstressesdevelopedinthenon-uniformstressfield.Yuetal.2,3investigatedthewrinklingproblembothexperimentallyandanalytically.Theyfoundthatwrinklingcouldoccurhavingtwocircumferentialwavesaccordingtotheirtheoreticalanalysis,whereastheexperimentalresultsindi-catedfourtosixwrinkles.NarayanasamyandSowerby4examinedthewrinklingofsheetmetalwhendrawingitthroughaconicaldieusingflat-bottomedandhemispherical-endedpunches.Theyalsoattemptedtorankthepropertiesthatappearedtosuppresswrinkling.Theseeffortsarefocusedonthewrinklingproblemsassocia-tedwiththeformingoperationsofsimpleshapesonly,suchasacircularcup.Intheearly1990s,thesuccessfulapplicationofthe3Ddynamic/explicitfinite-elementmethodtothesheet-metalformingprocessmadeitpossibletoanalysethewrinklingprobleminvolvedinstampingcomplexshapes.Inthepresentstudy,the3Dfinite-elementmethodwasemployedtoanalysetheeffectsoftheprocessparametersonthemetalflowcausingwrinklesatthedrawwallinthestampingofataperedsquarecup,andofasteppedrectangularpart.Ataperedsquarecup,asshowninFig.1(a),hasaninclineddrawwalloneachsideofthecup,similartothatexistinginaconicalcup.Duringthestampingprocess,thesheetmetalonthedrawwallisrelativelyunsupported,andistherefore254F.-K.ChenandY.-C.LiaoFig.1.Sketchesof(a)ataperedsquarecupand(b)netowrinkling.Inthepresentstudy,theeffectofvariousprocessparametersonthewrinklingwasinvestigated.Inthecaseofasteppedrectangularpart,asshowninFig.1(b),anothertypeofwrinklingisobserved.Inordertoestimatetheeffectivenessoftheanalysis,anactualproductionpartwithsteppedgeometrywasexaminedinthepresentstudy.Thecauseofthewrinklingwasdeterminedusingfinite-elementanalysis,andanoptimumdiedesignwasproposedtoeliminatethewrinkles.Thediedesignobtainedfromfinite-elementanaly-siswasvalidatedbyobservationsonanactualproductionpart.2.Finite-ElementModelThetoolinggeometry,includingthepunch,dieandblank-holder,weredesignedusingtheCADprogramPRO/ENGINEER.Boththe3-nodeand4-nodeshellelementswereadoptedtogeneratethemeshsystemsfortheabovetoolingusingthesameCADprogram.Forthefinite-elementsimul-ation,thetoolingisconsideredtoberigid,andthecorrespond-ingmeshesareusedonlytodefinethetoolinggeometryandFig.2.Finite-elementmesh.arenotforstressanalysis.ThesameCADprogramusing4-nodeshellelementswasemployedtoconstructthemeshsystemforthesheetblank.Figure2showsthemeshsystemforthecompletesetoftoolingandthesheet-blankusedinthestampingofataperedsquarecup.Owingtothesymmetricconditions,onlyaquarterofthesquarecupisanalysed.Inthesimulation,thesheetblankisputontheblank-holderandthedieismoveddowntoclampthesheetblankagainsttheblank-holder.Thepunchisthenmoveduptodrawthesheetmetalintothediecavity.Inordertoperformanaccuratefinite-elementanalysis,theactualstressstrainrelationshipofthesheetmetalisrequiredaspartoftheinputdata.Inthepresentstudy,sheetmetalwithdeep-drawingqualityisusedinthesimulations.Atensiletesthasbeenconductedforthespecimenscutalongplanescoincidingwiththerollingdirection(0)andatanglesof45and90totherollingdirection.TheaverageflowstressH9268,calculatedfromtheequationH9268H11005(H92680H110012H926845H11001H926890)/4,foreachmeasuredtruestrain,asshowninFig.3,isusedforthesimulationsforthestampingsofthetaperedsquarecupandalsoforthesteppedrectangularcup.AllthesimulationsperformedinthepresentstudywererunonanSGIIndigo2workstationusingthefinite-elementpro-gramPAMFSTAMP.TocompletethesetofinputdatarequiredFig.3.Thestressstrainrelationshipforthesheetmetal.Draw-WallWrinklinginaStampingDieDesign255forthesimulations,thepunchspeedissetto10msH110021andacoefficientofCoulombfrictionequalto0.1isassumed.3.WrinklinginaTaperedSquareCupAsketchindicatingsomerelevantdimensionsofthetaperedsquarecupisshowninFig.1(a).AsseeninFig.1(a),thelengthofeachsideofthesquarepunchhead(2Wp),thediecavityopening(2Wd),andthedrawingheight(H)arecon-sideredasthecrucialdimensionsthataffectthewrinkling.Halfofthedifferencebetweenthedimensionsofthediecavityopeningandthepunchheadistermedthediegap(G)inthepresentstudy,i.e.GH11005WdH11002Wp.Theextentoftherelativelyunsupportedsheetmetalatthedrawwallispresumablyduetothediegap,andthewrinklesaresupposedtobesuppressedbyincreasingtheblank-holderforce.Theeffectsofboththediegapandtheblank-holderforceinrelationtotheoccurrenceofwrinklinginthestampingofataperedsquarecupareinvestigatedinthefollowingsections.3.1EffectofDieGapInordertoexaminetheeffectofdiegaponthewrinkling,thestampingofataperedsquarecupwiththreedifferentdiegapsof20mm,30mm,and50mmwassimulated.Ineachsimulation,thediecavityopeningisfixedat200mm,andthecupisdrawntothesameheightof100mm.Thesheetmetalusedinallthreesimulationsisa380mmH11003380mmsquaresheetwiththicknessof0.7mm,thestressstraincurveforthematerialisshowninFig.3.Thesimulationresultsshowthatwrinklingoccurredinallthreetaperedsquarecups,andthesimulatedshapeofthedrawncupforadiegapof50mmisshowninFig.4.ItisseeninFig.4thatthewrinklingisdistributedonthedrawwallandisparticularlyobviousatthecornerbetweenadjacentwalls.Itissuggestedthatthewrinklingisduetothelargeunsupportedareaatthedrawwallduringthestampingprocess,also,thesidelengthofthepunchheadandthediecavityFig.4.Wrinklinginataperedsquarecup(GH1100550mm).openingaredifferentowingtothediegap.Thesheetmetalstretchedbetweenthepunchheadandthediecavityshoulderbecomesunstableowingtothepresenceofcompressivetrans-versestresses.Theunconstrainedstretchingofthesheetmetalundercompressionseemstobethemaincauseforthewrink-lingatthedrawwall.Inordertocomparetheresultsforthethreedifferentdiegaps,theratioH9252ofthetwoprincipalstrainsisintroduced,H9252beingH9280min/H9280max,whereH9280maxandH9280minarethemajorandtheminorprincipalstrains,respectively.HosfordandCaddell5haveshownthatiftheabsolutevalueofH9252isgreaterthanacriticalvalue,wrinklingissupposedtooccur,andthelargertheabsolutevalueofH9252,thegreateristhepossibilityofwrinkling.TheH9252valuesalongthecross-sectionMNatthesamedrawingheightforthethreesimulatedshapeswithdifferentdiegaps,asmarkedinFig.4,areplottedinFig.5.ItisnotedfromFig.5thatseverewrinklesarelocatedclosetothecornerandfewerwrinklesoccurinthemiddleofthedrawwallforallthreedifferentdiegaps.Itisalsonotedthatthebiggerthediegap,thelargeristheabsolutevalueofH9252.Consequently,increasingthediegapwillincreasethepossibilityofwrinklingoccurringatthedrawwallofthetaperedsquarecup.3.2EffectoftheBlank-HolderForceItiswellknownthatincreasingtheblank-holderforcecanhelptoeliminatewrinklinginthestampingprocess.Inordertostudytheeffectivenessofincreasedblank-holderforce,thestampingofataperedsquarecupwithdiegapof50mm,whichisassociatedwithseverewrinklingasstatedabove,wassimulatedwithdifferentvaluesofblank-holderforce.Theblank-holderforcewasincreasedfrom100kNto600kN,whichyieldedablank-holderpressureof0.33MPaand1.98MPa,respectively.Theremainingsimulationconditionsaremaintainedthesameasthosespecifiedintheprevioussection.Anintermediateblank-holderforceof300kNwasalsousedinthesimulation.Thesimulationresultsshowthatanincreaseintheblank-holderforcedoesnothelptoeliminatethewrinklingthatoccursatthedrawwall.TheH9252valuesalongthecross-sectionFig.5.H9252-valuealongthecross-sectionMNfordifferentdiegaps.256F.-K.ChenandY.-C.LiaoMN,asmarkedinFig.4,arecomparedwithoneanotherforthestampingprocesseswithblank-holderforceof100kNand600kN.ThesimulationresultsindicatethattheH9252valuesalongthecross-sectionMNarealmostidenticalinbothcases.Inordertoexaminethedifferenceofthewrinkleshapeforthetwodifferentblank-holderforces,fivecross-sectionsofthedrawwallatdifferentheightsfromthebottomtothelineMN,asmarkedinFig.4,areplottedinFig.6forbothcases.ItisnotedfromFig.6thatthewavinessofthecross-sectionsforbothcasesissimilar.Thisindicatesthattheblank-holderforcedoesnotaffecttheoccurrenceofwrinklinginthestamp-ingofataperedsquarecup,becausetheformationofwrinklesismainlyduetothelargeunsupportedareaatthedrawwallwherelargecompressivetransversestressesexist.Theblank-holderforcehasnoinfluenceontheinstabilitymodeofthematerialbetweenthepunchheadandthediecavityshoulder.4.SteppedRectangularCupInthestampingofasteppedrectangularcup,wrinklingoccursatthedrawwalleventhoughthediegapsarenotsosignificant.Figure1(b)showsasketchofapunchshapeusedforstampingasteppedrectangularcupinwhichthedrawwallCisfollowedbyastepDE.Anactualproductionpartthathasthistypeofgeometrywasexaminedinthepresentstudy.Thematerialusedforthisproductionpartwas0.7mmthick,andthestressstrainrelationobtainedfromtensiletestsisshowninFig.3.Theprocedureinthepressshopfortheproductionofthisstampingpartconsistsofdeepdrawingfollowedbytrimming.Inthedeepdrawingprocess,nodrawbeadisemployedonthediesurfacetofacilitatethemetalflow.However,owingtothesmallpunchcornerradiusandcomplexgeometry,asplitoccurredatthetopedgeofthepunchandwrinkleswerefoundtooccuratthedrawwalloftheactualproductionpart,asshowninFig.7.ItisseenfromFig.7thatwrinklesaredistributedonthedrawwall,butaremoresevereatthecorneredgesofthestep,asmarkedbyADandBEinFig.1(b).Themetalistornapartalongthewholetopedgeofthepunch,asshowninFig.7,toformasplit.Inordertoprovideafurtherunderstandingofthedefor-mationofthesheet-blankduringthestampingprocess,afinite-elementanalysiswasconducted.Thefinite-elementsimulationwasfirstperformedfortheoriginaldesign.ThesimulatedshapeofthepartisshownfromFig.8.ItisnotedfromFig.8thatthemeshatthetopedgeofthepartisstretchedFig.6.Cross-sectionlinesatdifferentheightsofthedrawwallfordifferentblank-holderforces.(a)100kN.(b)600kN.Fig.7.Splitandwrinklesintheproductionpart.Fig.8.Simulatedshapefortheproductionpa
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 厂房土地转让合同8篇
- 期末模拟卷(试题)2023-2024学年统编版语文一年级上册
- 跨界融合“时尚新品”典型案例申报表
- 《行政职业能力测验》2023年公务员考试北京市丰台区考前冲刺试题含解析
- 汉英植物词文化联想意义的对比研究
- 秘书资格考试:秘书三级必看题库知识点
- 部编版五年级上册英语专项-词汇-一
- 苏少版四年级书法下册《7 戈字旁》教学设计
- 人力资源管理实践实训实验总结
- 2024年团购项目融资计划书
- GB/T 10000-2023中国成年人人体尺寸
- 少儿播音主持-课件
- 质量管理小组基础知识课件
- 人教A版高中数学选择性必修第三册《条件概率与全概率公式》说课稿
- 输血科全系统应急预案
- 教科版六年级科学下册全套测试卷
- 长沙理工大学高数下题库
- 依法治校自评报告
- 管理专员岗位职责
- 模拟联合国介绍课件
- 外科学运动系统畸形
评论
0/150
提交评论