会员注册 | 登录 | 微信快捷登录 支付宝快捷登录 QQ登录 微博登录 | 帮助中心 人人文库renrendoc.com美如初恋!
站内搜索 百度文库

热门搜索: 直缝焊接机 矿井提升机 循环球式转向器图纸 机器人手爪发展史 管道机器人dwg 动平衡试验台设计

外文翻译--基于三维有限元方法的AZ31镁合金等通道弯角挤压的模具结构设计 英文版.pdf外文翻译--基于三维有限元方法的AZ31镁合金等通道弯角挤压的模具结构设计 英文版.pdf -- 5 元

宽屏显示 收藏 分享

资源预览需要最新版本的Flash Player支持。
您尚未安装或版本过低,建议您

angularChinaReceived5September2008Accepted17January2009AvailableonlinexxxxKeywordsAZ31magnesiumalloyEqualchannelangularextrusionFiniteelementmethodfinegrainedmicrostructuresinmagnesiumalloys.Itiscrucialtounderstandtheeffectofdiedesignontoobtainthesematerialswithhighstrengthandtoughness.InECAE,aworkpieceispressedthroughadiethatcontainstwochannelswithequalcrosssectionmeetingatanangle.Becausethecrosssectionoftheworkpieceremainsthesameduringextrusion,theprocesscanberepeateduntiltheaccumulateddeformationreachesadesiredlevel.Highstraincanbeachieved.FiniteelementmethodisoneoftheimportantapproachestounderstandtheofbackpressurebySonetal.,theoptimumdiedesignforhomogeneousplasticdeformationbyYoonSCetal.7.However,thesestudiesassumedtwodimensional2Dapproximationofplanestrainconditionanddonotdiscusstheinhomogeneityofstressandstrain.Resultsobtainedby2Danalysisgivelimitedinformation,inadditiontotheinherent2Dapproximationerrors.Someresearchers8–10haveexploredtheECAEprocessusingthreedimensions3Dplasticitytheoreticandsimulationsoftware.LuisPérezandLuri11usedupperboundmethodtoanalyzeinthreedimensionsECAEdiesforrectangularorsquarecrosssecCorrespondingauthor.Fax862368851783.MaterialsandDesignxxx2009xxx–xxxContentslistsavailableandARTICLEINPRESSEmailaddresshhjcqit.edu.cnH.J.Hu.1.IntroductionUltrafinegrainedmaterialshavebeenwidelyinvestigatedduetotheirimprovedmechanicalpropertiessuchashighstrengthandductility.Varioustechniqueshavebeendevelopedtoobtainultrafinegrainedmaterials.SevereplasticdeformationSPDtechniques,likeequalchannelangularextrusionECAE,highpressuretorsionHPT,cyclingchanneldiecompressionCCDCandaccumulativerollbondingARBaremostcommonlyforproducingsubmicrongrainstructuresinmetallicmaterialsatarelativelylowcost.Amongthem,theequalchannelangularextrusionECAE,originallydevelopedbySegal,isoneofthemosteffectivemethodsdeformationoccurringintheECAEprocess.ManyFEMbasedanalyseshavebeenperformedtodeterminethedeformationbehaviorofmaterialsandtoestimatethedevelopedstrainintheECAPprocess.TheseresearchworkincludetheeffectofchannelangleandoutercornerforfrictionlessconditionbyRaghavanS1,theeffectofchannelangleandoutercornerbyKimetal.,theeffectofoutercorneroninhomogeneitybySuhJYetal.2,thecornergapformationanditseffectbyKimandKim3,theeffectofchannelangleandcornerangleonmaterialflowbyLangandShyong4,theextensiveworkondifferentmaterialmodels,outercornerangleandcoefficientoffrictionbyLeeSCetal.5,theworkonoriginofinhomogeneousbehaviorofmetalbyWeietal.6,theeffectOutercornerangleDeformationinhomogeneity02613069/seefrontmatterC2112009Publishedbydoi10.1016/j.matdes.2009.01.022PleasecitethisarticleinpressasHuHJ2009,doi10.1016/j.matdes.2009.01.022thedeformationbehavior,straindistributionandloadrequirement.Inthepapernewthreedimensional3Dgeometricmodelswithdifferentcornerangles90C176,120C176andwithorwithoutinnerroundfilletsinthebottomdieweredesigned.SomeimportantprocessparameterswereregardedastheinitialandboundaryconditionsusedinDEFORMTM3Dsoftwaresuchastemperaturesofthedieandbillet,thefrictioncoefficient,etc.Toensuretheconvergenceofthesimulation,thegeometricalanddisplacementconditionsandreasonableconvergenceerrorlimits,etc.havebeenconsidered.ThedeformationheterogeneityofECAEwasanalyzedfromthesimulationandexperimentalresults.Thedeformationhomogeneitycausedbyfilletsatoutercornerwasimprovedcomparingwiththediewithoutfillets.ThecumulatemaximumstrainsdecreasedwiththefilletsofoutercornermanufacturedinECAEdieandtheinnercorneranglesincreasing.TherequirementextrusionforcedecreasedwiththefilletsmadeatoutercornerangleinECAEdie.TheanalysesshowedthatbetterstructuresofECAEdieincludedappropriateoutercornerfilletsandtheinnercornerangle90C176.Itwasdemonstratedthatthepredictedresultswereingoodagreementwithexperimentsandthetheoreticalcalculationandtheresearchconclusionsfromotherliteratures.C2112009PublishedbyElsevierLtd.ArticlehistoryEqualchannelangularextrusionECAEiswidelyinvestigatedbecauseofitspotentialtoproduceultraThediestructuredesignofequalchannelmagnesiumalloybasedonthreedimensionalHuHongJuna,,ZhangDingFeia,b,YangMingBocaNationalEngineeringResearchCenterforMagnesiumAlloys,ChongqingUniversity,ChongqingbCollegeofMaterialsScienceandEngineering,ChongqingUniversity,Chongqing400045,cCollegeofMaterialsScienceandEngineering,ChongqingInstituteofTechnology,ChongqingarticleinfoabstractMaterialsjournalhomepagewww.elseElsevierLtd.etal.ThediestructuredesignextrusionforAZ31finiteelementmethod400044,China400050,ChinaatScienceDirectDesignvier.com/locate/matdesofequalchannelangularextrusionforAZ31...JMaterDesigntionwherebothinternalandexternalradiiweretakenintoaccountandtheintersectionanglewasmade.The3DsimulationanalysisofECAPwasperformedbyChungetal.12usingacommercialfinitevolumemethodFVMcodetoanalyzetheeffectivestrainandstressforonepassoftheprocess.3DFEMwasappliedtoanalyzethecommercialpureTiCPTibilletsubjectedtofourpassNomenclatureUtheinnercornerangleC176estrainmm/mmeccriticalstrainmm/mmWtheoutercornerangleC1762H.J.Huetal./MaterialsandDesignARTICLEINPRESSECAEprocessat400C176CwithBcrouteinRef.13.Buttherewerefewresearchersadopted3DsimulationtechnologiestoinvestigatethedeformationbehaviorsofmagnesiumAZ31especiallytheinfluencesofdiestructuresonstraindistributionsandextrusionquality.ManyoftheearlystudiesofECAPwerelimitedtotheprocessingofsoftpuremetalsorsolidsolutionalloys.Morerecently,significantattentionhasbeendevotedtothepressingofmorecomplexalloysandsomemetalswithlimitednumbersofslipsystemsespeciallyformagnesiumalloys.Forthesedifficulttoworkmaterials,threedifferentstrategieshavebeenadoptedwiththeoverallobjectiveofachievingsuccessfulprocessingbyECAE.CurrentresearchinterestisintheprocessingtoobtainfinegrainedbulkmagnesiumalloyspecimensfromECAE14–20.AsketchofsuchanECAEdieisshowninFig.1.ThebottomdieconsistsoftwointersectingchannelsofthesamecrosssectionmeetingataninnercornerangleUseeFig.1.Inthisfigure,theangleWdefinestheoutercurvatureoftheintersectionbetweenthetwochannels.Inthiscontext,theuseoftheextremeprinciples,forinstance,theupperboundmethodhasgainedalotofattentiontoestimatethepressureneededfortheplungeraswellastheaccumulatedeffectivestrainresultingfromtheECAEmethod.ThenumericalsimulationwiththehelpofthefiniteelementmethodFEMhasbeenextensivelyusedtobetterunderstatingtheECAEmethod21–25.TheplasticdeformationbehaviorduringECAEisgovernedmainlybythediegeometry,thematerialitselfandtheprocessingconditions.ExperimentaldataandfiniteelementstudyofdiesgeometryinfluenceonECAEprocesshimselfarepresented.ItisnecessarytotheoreticallymodeltheECAEprocessinordertostudyvariouscomplicatedeffectsforbetterprocesscontrol.ThisstudyistonumericallyanalyzethedeformationbehaviorsinequalchannelangularextrusionsECAEofmagnesiumalloyAZ31andpredictthestrainsandextrusionforcesofECAEtoformnanostructureprocessbasedonvariousdiestructures.Fig.1.SchematicdiagramofanECAPdieshowinginnercornerangleUandoutercorneranglew.PleasecitethisarticleinpressasHuHJetal.Thediestructuredesign2009,doi10.1016/j.matdes.2009.01.022Inthepresentwork,aquasistaticsolutiontotheECAEmethodbytheFEMsimulationwascarriedoutusingdieswithintersectinganglesU90C176and120C176byonlyonepassofextrusion.ThefourECAEmodelshavebeenerectedinUGsoftwareandmeshedandsimulatedinDEFORMTM3Dcode.Numericalsimulationproceduresandmodelingofthediesandbillet,boundaryconditions,convergenceerrorlimitsfordeformationsimulationsandelementformulationshavebeenintroduced.TheeffectsofdifferentdiegeometriesonthedeformationinhomogeneityduringECAPwereinvestigated.ExperimentsfortwoECAEdieswithorwithoutfilletshavebeendoneinlaboratorytovalidatethesimulationresults.Becausetheevolutionofthemicrostructuresandmechanicalpropertiesofdeformedmaterialaredirectlyrelatedtotheamountofplasticdeformation,theunderstandingofthephenomenonassociatedwiththestraindevelopmentisveryimportantinECAE.Distributionsofeffectivestressandstrain,influencesofchannelangleonthedeformationindifferentzonesanddeformationhomogeneity,maximumstrainhavebeendiscussedindetail.2.MaterialmodelsandsimulationdetailsThecommercialFEMcode,DEFORM3DVersion5.0,wasusedtocarryoutthesimulationofonepassECAEprocess.2.1.AssumptionsandnumericalsimulationproceduresAwroughtmagnesiumalloyAZ31with3aluminum,1zincwasusedasthebilletmaterialbothincomputersimulationandexperimentalverification.ThenumericalsimulationswereperformedquasistaticallyusingacommercialfiniteelementcodeDEFORMTM3D.DEFORMTM3DwasacommercialpackagedevelopedbySFTCScientificFormingTechnologyCorporation.ItwasafiniteelementmethodFEMbasedprocesssimulationsystemdesignedtoanalyze3Dflowofvariousmetalformingprocesses.Itprovidedvitalinformationaboutmaterialandthermalflowduringformingprocesses.Thebilletwasassumedtobeelastic–plasticmaterial.Thefollowingassumptionswasadoptedinpresentanalysis1boththecontainerandthediearerigidbodies2theextrusionbilletwasarigidplasticmaterialand3thefrictionfactorsbetweentheextrusionbilletandtheram,container,anddiewereconstant.Thesimulationprocedureswereasfollows1the3Dgeometriesbillets,ramsanddiesachievedbyconstructing3DCADmodelsweredefinedinUnigraphicssoftware.Geometriescanbedefinedas3DIGESorSTLfiles.2Stoppingstrokewasset,theRradiusoftheinnercornermm_eeffectivestrainratesC01xxx2009xxx–xxxnumberofstepsdefinedandsimulationmodeandEnglishorSIunitswereselected.3Theobjectsbilletsanddiesweremeshed.Theobjectswerepositioned,withtheworkpieceasthereferenceobjectbothtoolsandramincontactwiththeworkpiece.Thematerialspropertiesweredefined.4Thermalboundaryconditionsweredefined.5Objectstemperatureswereinitialized.6Contactboundaryconditionsweregeneratedandfrictioncoefficientsbetweenbilletsanddies,billetsandramsweredefined.7Rammovementparametersdirectionandspeedwereassigned.8Thedatabasewascheckedandgeneratedandcalculated,FEAtosimulatethehotextrusionprocesswasperformed.9Thesimulationresultswerereadfromthepostprocessor.ofequalchannelangularextrusionforAZ31...JMaterDesign2.2.ModelingofthediesandramsThediegeometriesusedinthesimulationsareshowninFig.2.ThebilletcoordinateaxisxyzemployedinthepresentstudyisshowninFig.2.Thex,yandzdirectionswereparalleltoextrusiondirectionED,verticaldirectionNDandtransversedirectionTD,respectively.ThechannelanglesU90C176andU120C176areconsideredandillustratedrespectivelyinFig.2aandbandthecornerangleWofthediesareassumedtoequalto0.ThemodifiedgeometricmodelswithinnerroundfilletsattheoutercornerareshowninFig.2candd.ThegeometricalparametersofthefourECAEdiesforFig.2arelistedinTable2.Thechannelanglecornerradiusattheintersectionofthetwochannelswas2mmandoutercornerangleradiuswas18mm.Thelengthofinletchannelwas50mmandoutletchannellengthwas25mm.Boththeinletandoutletchannelshadthesamedimensionsofsquarecrosssection£16mm.Table3givesthedimensions,extrusionspeedandtemperatureusedincomputersimulation,etc.,whichareidenticaltothoseappliedinextrusionexperiments.Thespeedoframmoveddownalongtheinletchannelwas10mmsC01asinthesimulationsandexperiments.Thestrokeoframwas50mm.Forthesakeofsimplicity,thediesandpressingramwereassumedtoberigidbodiesthatundergonopermanentdeformation,whichmechanicalpropertiesemployedanH13toolsteelwiththeYoungmodulusandthermalconductiondependentonthetemperatureshowninFig.3aandb.Poissonsratiomwas0.3.FourdistinctgeometricmodelshavebeenanalyzedbyfiniteelementTable2ThegeometricalparametersoftheECAEdie.UC176WC176RrFig.3a90000Fig.3b99182Fig.3c120000Fig.3d12060182Table3Simulationandexperimentalparameters.Billetlengthmm50Billetdiametermm16insiderdiameterofECAEdiemm16outsidediameterofdiemm50InitialbillettemperatureC176C300InitialtoolingtemperatureC176C275StrainraterangeforflowstressmeasurementsC010.01–10TemperaturerangeforflowstressmeasurementC176C250–450Ramspeedmm/s10Frictionfactorofthecontainer–billetinterface0.25Frictionfactorbetweenthebilletanddie0.25H.J.Huetal./MaterialsandDesignxxx2009xxx–xxx3ARTICLEINPRESSFig.2.SchematicdiagramsofthethreedimensionalECAPdieFEMmodelingshowingachannelangleequalto90C176bchannelangleequalto120C176cchannelangle90C176withoutercornerangledchannelangle120C176withoutercornerangle,whererdenotestheradiusofthechannelangle,Rtheradiusoftheoutercornerangle.Table1PhysicalpropertiesoftheAZ31workpiece.PropertyAZ31Poissonsratio0.35Coefficientoflinearexpansion26.8EC06Density1780kg/m3Poissonsratio0.35Youngsmodulus45,000MPaEmissivity0.12PleasecitethisarticleinpressasHuHJetal.Thediestructuredesign2009,doi10.1016/j.matdes.2009.01.022Fig.3.ThematerialpropertiesforH13.ofequalchannelangularextrusionforAZ31...JMaterDesignanalysisFEAtorevealthedeformationbehaviorsandtheirrelationshipwiththedesignconfiguration.2.3.ModelingofthebilletThemagnesiumbilletusedinthecalculationswasaroundcrosssectiondiameter16mmandalengthof50mm£16mmC250mm.TheAZ31wasconsideredasanisotropicelastic–plasticmaterial.Thetensilestress–straincurveat300C176CofAZ31billetannealedat400C176Cfor12h,asshowninFig.4,theflowstress/straindataobtainedfromtheuniaxialcompressiontestswereintroducedintoFEAusingcommercialsoftwarepackagesDEFORMTM3D.TheelasticpropertieswereYoungsmodulusE45GPaandPoissonsratiom0.3.MaterialpropertyparametersoftheAZ31workpiecearelistedinTable1.2.4.MeshingmethodInallsimulations,anautomaticremeshingschemewasusedto4H.J.Huetal./MaterialsandDesignARTICLEINPRESSaccommodatelargestrainsandtotakeintoaccounttheoccurrenceofflowlocalization,whichpreventedfurthercalculationduringthesimulation.TheelementswereautomaticallyremeshediftheybecametoodistortedduringECAEsimulationprocess.Alltheextrusiontoolingincludedinthesimulationwasmeshedwithtetrahedralelementsanditsheatexchangewiththeworkpieceincorporatedintosimulation.ThesimulationparametersusedarelistedinTable3.Toenhancetheefficiencyofsimulationandobtainspecificresolutionsintheareasofparticularinterest,anumberofwindowswithanincreasedelementdensitywereappliedtogeneratelocalfinerelements,especiallyaroundthechannelcornerfordie.Toensuresimulationaccuracyandstability,theabsolutemeshdensitywasusedtokeeptheelementsizeatanypositionnearlyconstantduringthesimulation,becauseitwasthisdensitythatdefinedthenumberofelementsperunitlengthonthesurfaceoftheworkpiece.Theminimumsizeoftheelementwas0.25–0.35mm.Thebilletwasdividedinto20,000fournodetetrahedralelements.Totalnumberofelementsoframanddiewere8000and20,000,respectively.Thenumbersofelementswerefoundtobesufficienttoexpresslocaldeformationofthestrainrateinsensitiveworkpiecesthroughcalculationswithvaryingthenumberofelements.Tolimitthesizesofsimulationdatabasefilesandenhancesimulationspeed,theroundextrudatewascutoffatthelengthof50mmwhenitslengthexceeded50mm.Asmallrelativeinterferencedepthof0.3wasdefinedtotriggertheremeshingproFig.4.Truestress/truestraincurvesofAZ31obtainedfromcompressiontestsat300C176Cunderdifferentstrainrateandcorrectedfordeformationheatingduringthetesting.PleasecitethisarticleinpressasHuHJetal.Thediestructuredesign2009,doi10.1016/j.matdes.2009.01.022cedurewhenanyelementattheedgeoftheworkpiecehadbeenpenetratedintoandthepenetrationdepthexceeded30oftheoriginallengthofthesurfaceedgethathadacontactnodeateachend.2.5.Boundaryconditions2.5.1.ContactandfrictionboundaryconditionsContactboundaryconditionswereappliedtonodesofbillet,andspecifycontactbetweenthosenodesandthesurfaceofram.InordertoassurethequadraticconvergenceoftheNewton–Raphsonmethodusedinthecode,thecompressivedisplacementsimposedonthebillettopregionintheverticaldirectionwerefixedinincrementsof0.10mmuptoatotaldisplacementof50mm.TheNewton–Raphsonmethodwasrecommendedformostproblemsbecauseitgenerallyconvergedinlessiterationthantheotheravailablemethods.However,solutionsweremorelikelytofailtoconvergewiththismethodthanwithothermethods.Torepresentthefrictionbehaviorasaconsequenceoftheshearstressandthecontactpressure,thegeneralizedCoulombslawwasused.Thefrictionattheworkpiece–toolinginterfaceswasconsideredtobeofsheartype.Itwaswellknownthatthislawstatedproportionalitybetweenshearyieldstressandthecontactpressureduetothepresenceofthefriction.SpecificallyintheDEFORMcode,thisrelationwasverifiedbymeansofvonMisesyieldcriterioncorrectedtothesimpleshearconditionandwasgivenbyEq.1s¼lrffiffiffi3pð1Þwheresisthefrictionalshearstressandristheeffectiveflowstressoftheworkpiece.l06l61thefrictionfactor.Inthepresentsimulations,africtionfactorof0.25atthedie–billetinterfacewaschosen.Thesamefrictionfactorwasassumedattheinterfacebetweenthebilletandram.2.5.2.TemperatureboundaryconditionRegardlessoftheheattransferbetweenthedieandtheambience,theheattransferbetweenthebilletandthediewasconsidered.NewtoncoolingprinciplewasusedandexpressedasEq.2kTxini¼C0hðTC0TwÞð2Þwherehisthecoefficientoftheheattransferbetweenthematerialanddie,Twisthetemperatureofthedie.niisthenormalinidirection.Inthispaper,theambienttemperaturewasconsideredas25C176C,andtemperatureoftheECAEdie275C176C.Theinitialbillettemperaturewaschosentobeatarelativelyhighlevel300C176Cwithoutrunningtheriskofreachingthepressforcelimitduringexperimentsathighramspeeds.Heattransfercoefficientbetweentoolingandbilletwas11N/C176Csmm2,andthevalueHeattransfercoefficientsbetweentooling/billetandairare0.02N/C176Csmm2.EmissivitycoefficientsoftheAZ31andH13toolsteelwere0.12and0.7,respectively.2.6.ConvergencestudiesinsimulationsConvergenceoftheinvestigatedvariabletoaconstantvaluebychangingvariousnumericalparametersisanessentialprocedureinfiniteelementsimulation26.Theparametersthatmustbecontrolledaremeshsizeandtopologytheminimumsizeoftheelementwas0.25–0.35mminthispaper,contactparameters,xxx2009xxx–xxxremeshingparameters,incrementsizetimestepwas0.01s,convergencelimits,solverparametersthedisplacementincrementwas0.1mm,frictionmodelparametersCoulombslawused,ofequalchannelangularextrusionforAZ31...JMaterDesign
编号:201311171559097057    大小:1.77MB    格式:PDF    上传时间:2013-11-17
  【编辑】
5
关 键 词:
教育专区 外文翻译 精品文档 外文翻译
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. 人人文库网仅提供交流平台,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。
  人人文库网所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
0条评论

还可以输入200字符

暂无评论,赶快抢占沙发吧。

当前资源信息

4.0
 
(2人评价)
浏览:8次
英文资料库上传于2013-11-17

官方联系方式

客服手机:13961746681   
2:不支持迅雷下载,请使用浏览器下载   
3:不支持QQ浏览器下载,请用其他浏览器   
4:下载后的文档和图纸-无水印   
5:文档经过压缩,下载后原文更清晰   

相关资源

相关资源

相关搜索

教育专区   外文翻译   精品文档   外文翻译  
关于我们 - 网站声明 - 网站地图 - 友情链接 - 网站客服客服 - 联系我们
copyright@ 2015-2017 人人文库网网站版权所有
苏ICP备12009002号-5