




已閱讀5頁(yè),還剩2頁(yè)未讀, 繼續(xù)免費(fèi)閱讀
版權(quán)說(shuō)明:本文檔由用戶(hù)提供并上傳,收益歸屬內(nèi)容提供方,若內(nèi)容存在侵權(quán),請(qǐng)進(jìn)行舉報(bào)或認(rèn)領(lǐng)
文檔簡(jiǎn)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
溫馨提示
- 1. 本站所有資源如無(wú)特殊說(shuō)明,都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請(qǐng)下載最新的WinRAR軟件解壓。
- 2. 本站的文檔不包含任何第三方提供的附件圖紙等,如果需要附件,請(qǐng)聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶(hù)所有。
- 3. 本站RAR壓縮包中若帶圖紙,網(wǎng)頁(yè)內(nèi)容里面會(huì)有圖紙預(yù)覽,若沒(méi)有圖紙預(yù)覽就沒(méi)有圖紙。
- 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
- 5. 人人文庫(kù)網(wǎng)僅提供信息存儲(chǔ)空間,僅對(duì)用戶(hù)上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理,對(duì)用戶(hù)上傳分享的文檔內(nèi)容本身不做任何修改或編輯,并不能對(duì)任何下載內(nèi)容負(fù)責(zé)。
- 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容,請(qǐng)與我們聯(lián)系,我們立即糾正。
- 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時(shí)也不承擔(dān)用戶(hù)因使用這些下載資源對(duì)自己和他人造成任何形式的傷害或損失。
最新文檔
- 傳統(tǒng)紡織工藝研究:手工印染技術(shù)的歷史傳承與創(chuàng)新應(yīng)用
- 民警打分具體管理辦法
- 供水公司主業(yè)管理辦法
- 法蘭西國(guó)族認(rèn)同研究:從“國(guó)族傳奇”看歷史演變
- 民國(guó)茶葉消費(fèi)量與產(chǎn)量動(dòng)態(tài)關(guān)系研究
- 內(nèi)部濕度差異對(duì)硬化水泥漿體特性的影響研究
- 公共物品維護(hù)管理辦法
- 變頻器效率優(yōu)化-洞察及研究
- 跨界共生:“雙師型”教師企業(yè)實(shí)踐激勵(lì)機(jī)制創(chuàng)新探討
- 鞭毛狀微生物阪崎腸桿菌的乳粉檢測(cè)技術(shù)研究
- 辦公室應(yīng)聘題庫(kù)及答案
- 2025年河北中考地理真題含答案
- 鐵礦尾礦清運(yùn)方案(3篇)
- 國(guó)開(kāi)機(jī)考答案 管理學(xué)基礎(chǔ)2025-06-27
- 國(guó)家開(kāi)放大學(xué)《思想道德與法治》社會(huì)實(shí)踐報(bào)告范文一
- 【9語(yǔ)安徽中考卷】2025年安徽省中考招生考試真題語(yǔ)文試卷(真題+答案)
- 2025年空氣過(guò)濾器行業(yè)分析報(bào)告
- 同等學(xué)力人員申請(qǐng)碩士學(xué)位電子科學(xué)與技術(shù)學(xué)科綜合水平全國(guó)統(tǒng)一考試大綱(第二版)
- (高清版)DG∕TJ 08-507-2018 高強(qiáng)混凝土抗壓強(qiáng)度無(wú)損檢測(cè)技術(shù)標(biāo)準(zhǔn)
- 2024年鐵嶺市三支一扶考試真題
- 2024版機(jī)電工程施工質(zhì)量標(biāo)準(zhǔn)化數(shù)字模型圖集
評(píng)論
0/150
提交評(píng)論