欢迎来到人人文库网! | 帮助中心 人人文档renrendoc.com美如初恋!
人人文库网
全部分类
  • 图纸下载>
  • 教育资料>
  • 专业文献>
  • 应用文书>
  • 行业资料>
  • 生活休闲>
  • 办公材料>
  • 毕业设计>
  • ImageVerifierCode 换一换
    首页 人人文库网 > 资源分类 > PDF文档下载  

    外文翻译--提高板材成形效率的坐标网分析法 英文版.pdf

    • 资源ID:97239       资源大小:250.90KB        全文页数:6页
    • 资源格式: PDF        下载积分:5积分
    扫码快捷下载 游客一键下载
    会员登录下载
    微信登录下载
    三方登录下载: 微信开放平台登录 支付宝登录   QQ登录   微博登录  
    二维码
    微信扫一扫登录

    手机扫码下载

    请使用微信 或支付宝 扫码支付

    • 扫码支付后即可登录下载文档,同时代表您同意《人人文库网用户协议》

    • 扫码过程中请勿刷新、关闭本页面,否则会导致文档资源下载失败

    • 支付成功后,可再次使用当前微信或支付宝扫码免费下载本资源,无需再次付费

    账号:
    密码:
      忘记密码?
        
    友情提示
    2、PDF文件下载后,可能会被浏览器默认打开,此种情况可以点击浏览器菜单,保存网页到桌面,就可以正常下载了。
    3、本站不支持迅雷下载,请使用电脑自带的IE浏览器,或者360浏览器、谷歌浏览器下载即可。
    4、本站资源(1积分=1元)下载后的文档和图纸-无水印,预览文档经过压缩,下载后原文更清晰。
    5、试题试卷类文档,如果标题没有明确说明有答案则都视为没有答案,请知晓。

    外文翻译--提高板材成形效率的坐标网分析法 英文版.pdf

    JournalofMaterialsProcessingTechnology140(2003)616621EfficiencyenhancementinsheetmetalforminganalysiswithameshregularizationmethodJ.H.Yoon,H.HuhDepartmentofMechanicalEngineering,KoreaAdvancedInstituteofScienceandTechnologyScienceTown,Daejeon305-701,SouthKoreaAbstractThispapernewlyproposesameshregularizationmethodfortheenhancementoftheefficiencyinsheetmetalforminganalysis.Theregularizationmethodsearchesfordistortedelementswithappropriatesearchingcriteriaandconstructspatchesincludingtheelementstobemodified.Eachpatchisthenextendedtoathree-dimensionalsurfaceinordertoobtaintheinformationofthecontinuouscoordinates.Inconstructingthesurfaceenclosingeachpatch,NURBS(non-uniformrationalB-spline)surfaceisemployedtodescribeathree-dimensionalfreesurface.Onthebasisoftheconstructedsurface,eachnodeisproperlyarrangedtoformunitelementsascloseastoasquare.Thestatevariablescalculatedfromitsoriginalmeshgeometryaremappedintothenewmeshgeometryforthenextstageorincrementalstepofaforminganalysis.Theanalysisresultswiththeproposedmethodarecomparedtotheresultsfromthedirectforminganalysiswithoutmeshregularizationinordertoconfirmthevalidityofthemethod.©2003ElsevierB.V.Allrightsreserved.Keywords:Meshregularization;Distortedelement;NURBS;Patch;Finiteelementanalysis1.IntroductionNumericalsimulationofsheetmetalformingprocessesenjoysitsprosperitywithaburstofdevelopmentofthecom-putersandtherelatednumericaltechniques.Thenumericalanalysishasextendeditscapabilitiesforsheetmetalformingofcomplicatedgeometrymodelsandmulti-stageforming.Inthecaseofacomplicatedgeometrymodel,however,severelocaldeformationoccurstoinducetheincreaseofthecom-putingtimeanddeterioratetheconvergenceoftheanalysis.Distortionandseveredeformationofthemeshgeometryhasaneffectonthequalityofforminganalysisresultsespeciallyinthecaseofmulti-stageforminganalysiswhenthemeshgeometryformedbytheforminganalysisatthefirststageisusedfortheforminganalysisatthenextstage.Thisillbehaviorofthedistortedmeshcanbeavoidedbytherecon-structionofthemeshsystemsuchasthetotalortheadaptiveremeshingtechniques.Theadaptiveremeshingtechniqueisknowntobeanefficientmethodtoreducedistortionofelementduringthesimulation,butitstillneedstremen-douscomputingandputsrestrictionsamongsubdividedelements.Correspondingauthor.Tel.:+82-42-869-3222;fax:+82-42-869-3210.E-mailaddress:hhuhkaist.ac.kr(H.Huh).Effectivemethodstoconstructameshsystemhavebeenproposedbymanyresearchers.Typicalmethodscouldber-method1inwhichnodalpointsareproperlyrearrangedwithoutthechangeofthetotaldegreesoffreedomofthemeshsystem,h-method2inwhichthenumberofmeshesisincreasedwithelementsofthesamedegreesoffreedom,andp-method3inwhichthetotaldegreesoffreedomofthemeshsystemisincreasedtoenhancetheaccuracyofso-lutions.SluiterandHansen4andTalbertandParkinson5constructedtheanalysisdomainasacontinuousloopandcreatedelementsinsub-loopsdividedfromthemainloop.Lo6constructedtriangularelementsinthewholedomainandthenconstructedrectangularelementsbycom-biningadjacenttriangularelements.Inthispaper,ameshregularizationmethodisnewlyproposedinordertoenhancetheefficiencyoffiniteele-mentanalysesofsheetmetalforming.Themeshregular-izationmethodautomaticallyfindsoutdistortedelementswithsearchingcriteriaproposedandcomposespatchestobemodified.Eachpatchisthenextendedtothree-dimensionalsurfacesinordertoobtaintheinformationofthecontinuouscoordinatesonthethree-dimensionalsurface.Thesurfaceenclosingeachpatchisdescribedasathree-dimensionalfreesurfacewiththeuseofNURBS(non-uniformrationalB-spline).Onthebasisoftheconstructedsurface,eachnodeisproperlyarrangedtocomposeregularelementsclosetoasquare.Thestatevariablescalculatedfromitsoriginalmesh0924-0136/$seefrontmatter©2003ElsevierB.V.Allrightsreserved.doi:10.1016/S0924-0136(03)00801-XJ.H.Yoon,H.Huh/JournalofMaterialsProcessingTechnology140(2003)616621617geometryaremappedintothenewmeshgeometryfortheforminganalysisatthenextstage.Numericalresultscon-firmtheefficiencyoftheproposedmethodandtheaccuracyoftheresult.Itisalsonotedthatthepresentmethodiseffec-tiveinthecrashanalysesofsheetmetalmembersobtainedfromtheformingsimulation.2.RegularizationofthedistortedelementTheregularizationproceduretomodifydistortedele-mentsisintroducedinordertoenhancetheefficiencyofanalysisforthenextfiniteelementcalculation.Thedistortedelementsareselectedwithappropriatesearchingcriteriaandallocatedtoseveralpatchesforregularization.Thepatchesareextendedtothree-dimensionalsurfaceswiththeuseofNURBSforfullinformationofthecontinuouscoor-dinatesonthethree-dimensionalsurface.Onobtainingthenewcoordinatesofeachnode,thedistortedelementsareregularizedtoaregularelementthatisclosetoasquare.2.1.ThecriterionofmeshdistortionDistortedmeshesareselectedwiththetwogeometricalcriteria:oneistheinnerangle;andtheotheristheaspectratiooftheelementside.2.1.1.InnerangleTheinnerangleofaquadrilateralelementshouldbeclosetotherightangleforgoodresultsfromfiniteelementcalcu-lation.Zhuetal.7definedthereasonableelementwhenthefourinneranglesareformedwiththeangleof90±45whileLoandLee8proposedtheinnerangleof90±52.5asthesamecriterion.ThecriterionofmeshdistortionfortheinnerangleisdeterminedbyconstitutingEq.(1).AmeshisregardedasdistortedwhenEq.(1)islessthan/3or(i)maxinEq.(3)9isgreaterthan/6.Thecriterionisratherstrictinordertoavoidthegeometricallimitationincaseofapplyingtheregularizationmethodinconfinedregions:vectorfQ=1e1+2e2+3e3+4e4(1)|vectorfQ|=radicaltpradicalvertexradicalvertexradicalbt4summationdisplayi=1(i)2(2)i=vextendsinglevextendsinglevextendsingle12ivextendsinglevextendsinglevextendsingle(3)2.1.2.AspectratiooftheelementTheidealaspectratiooftheelementsideshouldbeunitywhenthefoursidesofanelementhavethesamelength.TheaspectratioisdefinedasEq.(4)andthenthedistortionisdefinedwhenitislessthan5thatcouldbemuchlessforastrictcriterion:maxr12,r23,r34,r41minr12,r23,r34,r41(4)whererijisthelengthofeachelementside.Fig.1.Processforconstructionofapatch.2.2.Domainconstruction2.2.1.ConstructionofthepatchDistortedelementsselectedbythecriteriaofmeshdistor-tionaredistributedinvariousregionsaccordingtothecom-plexityoftheshapeofformedgeometry.Theseelementsareallocatedtopatchesconstructedfortheefficiencyofthealgorithm.Theshapeofpatchesismadeupforrectangu-larshapesincludingalldistortedelementsforexpandingtheregionofregularizationandapplyingtoNURBSsurfaceex-plainedinnextsection.ThisprocedureisshowninFig.1.Whenholesandedgesarelocatedbetweendistortedele-ments,theregionsarefilleduptomakepatchesarectangularshape.Thepatchisthenmappedtoathree-dimensionalfreesur-facebyusingNURBSsurface.Theprocedureisimportanttoobtainentireinformationofthecontinuouscoordinatesonthethree-dimensionalsurface.NURBSsurfacecande-scribethecomplexshapequicklybyusinglessdatapointsanddoesnotchangetheentiredomaindataduetothelocalchange.2.2.2.NURBSsurfaceNURBSsurfaceisgenerallyexpressedbyEq.(5)asthep-orderintheu-directionandtheq-orderinthev-direction10:S(u,v)=summationtextni=0summationtextmj=0Ni,p(u)Nj,q(v)wi,jPi,jsummationtextni=0summationtextmj=0Ni,p(u)Nj,q(v)wi,j(5)wherePi,jisthecontrolpointsastheu-,v-direction,wi,jtheweightfactorandNu,p(u),Nj,q(u)thebasisfunctionthatareexpressedbyEq.(6):Ni,0=braceleftBigg1ifuiuui+1,0otherwise,Ni,p(u)=uuiui+puiNi,p(u)+ui+p+1uui+p+1ui+1Ni+1,p1(u)(6)Inordertomapthenodesfromthepatchesontothecon-structedsurface,anumberofpointsarecreatedfortheircoordinatesontheNURBSsurface.Thelocationofeach618J.H.Yoon,H.Huh/JournalofMaterialsProcessingTechnology140(2003)616621Fig.2.Selectingdirectionofdistortedelements.movingnodebyapplyingaregularizationmethodisdeter-minedsuchthatthelocationofapointhastheminimumdistancebetweennodesonNURBSsurface.Theinforma-tiononthecoordinatesofthenodalpointstobemovedisstoredtoconstructanewmeshsystem.2.3.RegularizationprocedureTheregularizationmethodiscarriedoutwiththeunitofapatchthatformsarectangularshape.FiniteelementstoberegularizedisselectedbytheorderofFig.2.Eachselectedelementisdividedbytwotriangularelementsandthenthedividedelementismadeofarighttriangularelementbyrelocatingthevertexonthecirclehavingthediameterfromvectorx1tovectorx2asshowninEq.(7)andFig.3.Whentheprocedureterminates,thesameprocedureisrepeatedintheoppositedirection:vectorx1+vectorx22=vectorxcen,|vectorx1vectorx2|2=r,vectorxcurvectorxcen=vectorxdir,vectorxnew=vectorxdir|vectorxdir|r×factor+vectorxcen(7)Thefinallocationofanoderelocatedbyusingthereg-ularizationmethodissubstitutedforthelocationofapointonNURBSsurface.Aftertheregularizationproce-dureisfinished,asimplesoothingprocedureiscarriedoutbyEq.(8)fortheroughregiongeneratedduringtheFig.3.Regularizationschemebymovingnodes.procedure:PN=summationtextNi=1AiCisummationtextNi=1Ai(8)wherePNisthecoordinateofanewnode,AitheareasofadjacentelementsandCithecentroidoftheadjacentelements.2.4.LevelofdistortionAsadistortionfactor,levelofdistortion(LD)isnewlyproposed.LDcanbeusedtoevaluatethedegreeofimprove-mentintheelementquality:LD=A×B(9)whereA=summationtext4i=1|sini|4,B=tanhparenleftbigk×Bprimeparenrightbig(10)Bprime=minr12,r23,r34,r41maxr12,r23,r34,r41,k=tanh1()(11)LDhasthevaluebetween0and1;whenLD=1,theele-mentisanidealelementofasquareandwhenLD=0,thequadrilateralelementbecomesatriangularelement.iarethefourinneranglesofanelement,soAisthefactorfortheinnerangle.BisthefactorfortheaspectratioofelementsidesandisdefinedbythehyperbolictangentfunctioninordertomakeLDlesssensitivetothechangeofB.Forex-ample,whenthereasonableaspectratiooftheelementsideis1:4,thevalueofBcanbeadjustedbyapplying=0.25and=0.6suchthattheslopeofthefunctionBischangedabruptlyaroundthevalueofBprime=0.25.Consequently,thevalueofLDdecreasesrapidlywhentheaspectratioBprimeislessthan0.25whilethevalueofLDincreasesslowlywhentheBprimeisgreaterthan0.25.Thisschemecanregulatethein-nerangleandtheaspectratiotohavetheequaleffectontheLD.2.5.MappingofthestatevariablesWhentheregularizedmeshsystemisusedforthenextcalculationoftheforminganalysisorthestructuralanaly-sis,mappingofthestatevariablesisneededformoreaccu-rateanalysisconsideringthepreviousforminghistory.Themappingprocedureistomapthecalculatedstatevariablesintheoriginalmeshsystemontotheregularizedmeshsys-tem.AsshowninFig.4,asphereisconstructedsurround-inganewnodesuchthatthestatevariablesofnodesinthespherehaveaneffectonthestatevariablesofthenewnode.ThestatevariablesofthenewnodearedeterminedfromthestatevariablesoftheneighboringnodesinthespherebyimposingtheweightingfactorinverselyproportionaltothedistancebetweenthetwonodesasshowninEq.(12):Vc=summationtextmj=1Vj/rjsummationtextmi=11/ri(12)J.H.Yoon,H.Huh/JournalofMaterialsProcessingTechnology140(2003)616621619Fig.4.Controlsphereformappingofthestatevariables.whereVjisthestatevariablecalculatedontheoriginalmeshsystem,andrjthedistancebetweenthenewnodeandtheneighboringnodes.3.Numericalexamples3.1.ForminganalysisofanoilpanWhileoilpansareusuallyfabricatedwithatwo-stageprocessinthepressshop,thepresentanalysisiscarriedoutwithasingle-stageprocessasshowninFig.5thatdescribesthepunchanddieset.Theregularizationmethodcanbeappliedtothefiniteele-mentmeshsystemwheneverneededforenhancementofthecomputationefficiency.Inthisexamplefordemonstration,themethodisappliedtotheanalysisofoilpanformingattwoformingintervalsforregularizationofdistortedmeshesasdirectedinFig.6.Fig.7explainstheprocedureoftheregularizationmethod.Fig.7(a)showsthedeformedshapeatthepunchstrokeofFig.5.Punchanddiesetforoilpanforming.60%forming6080%forming100%formingRegularizationRegularizationFig.6.Applyingtheregularizationmethodtotheforminganalysis.Fig.7.Procedureofregularization:(a)searchingdistortedelements;(b)constructingpatchesfordistortedelements;(c)regularizationofdistortedelements.60%andthreepartsofmeshdistortionbytheformingpro-cedure.Itindicatesthatthenumberofpatchestobecon-structedis3.Distortedmeshesareselectedaccordingtothetwogeometricalcriteriaformeshdistortion.Andthenthepatchesofarectangularshapeareformedtoincludealldis-tortedelementsasshowninFig.7(b).Finally,theelementsinthepatchesareregularizedasshowninFig.7(c).Inordertoevaluatethedegreeofimprovementintheel-ementqualityafterapplyingtheregularizationmethod,thevalueofLDfortheregularizedmeshsystemiscomparedtheonefortheoriginalmeshsystem.TheLDvaluesforthereg-ularizedmeshsystemhaveuniformdistributionthroughouttheelementswhilethosefortheoriginalmeshsystemhavewidevariationasshowninFig.8.Itmeansthatthequalityoftheregularizedmeshsystemisenhancedwiththesameleveldistortion.Consequently,explicitfiniteelementcomputationwiththeregularizedmeshsystemcanbeprecededwithalargerincrementaltimestepasshowninFig.9.Inthisanal-ysisofoilpanforming,thecomputingtimewiththeregular-izedmeshsystemisreducedabout12%evenaftertwotimesofregularization.Theamountofreductioninthecomputingtimecanbeincreasedwithmorefrequentregularization.3.2.CrashanalysisofafrontsidememberThecrashanalysisisusuallycarriedoutwithoutconsid-eringtheformingeffectandadoptsthemeshsystemapartformtheforminganalysis.Incasethattheformingeffectisconsideredtoimprovetheaccuracyandreliabilityoftheanalysisresults,themeshsystemfortheforminganalysiscouldbedirectlyusedinthecrashanalysisfortheefficiencyoftheanalysis.Themeshsystemaftertheforminganalysis,

    注意事项

    本文(外文翻译--提高板材成形效率的坐标网分析法 英文版.pdf)为本站会员(上***)主动上传,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,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知人人文库网(点击联系客服),我们立即给予删除!

    温馨提示:如果因为网速或其他原因下载失败请重新下载,重复下载不扣分。




    关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服 - 联系我们

    网站客服QQ:2881952447     

    copyright@ 2020-2025  renrendoc.com 人人文库版权所有   联系电话:400-852-1180

    备案号:蜀ICP备2022000484号-2       经营许可证: 川B2-20220663       公网安备川公网安备: 51019002004831号

    本站为文档C2C交易模式,即用户上传的文档直接被用户下载,本站只是中间服务平台,本站所有文档下载所得的收益归上传人(含作者)所有。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,对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私,请立即通知人人文库网,我们立即给予删除!