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1、ActaMaterialia55(2007)883–895www.actamat-journals.comThree-dimensionalheatandmaterialflowduringfrictionstirweldingofmildsteela,*abaR.Nandan,G.G.Roy,T.J.Lienert,T.DebroyaDepartmentofMaterialsScienceandEngineering,ThePennsylvaniaStateUniversity,UniversityPark,PA16802,USAbMaterialsSci
2、enceandTechnology,LosAlamosNationalLaboratory,LosAlamos,NM,USAReceived15April2006;receivedinrevisedform3September2006;accepted7September2006Availableonline4December2006AbstractThree-dimensionalviscoplasticflowandheattransferduringfrictionstirweldingofmildsteelwereinvestigatedbothex
3、perimentallyandtheoretically.Theequationsofconservationofmass,momentumandenergyweresolvedinthreedimensionsusingspatiallyvariablethermo-physicalpropertiesandamethodologyadaptedfromwell-establishedpreviousworkinfusionwelding.Non-Newtonianviscosityforthemetalflowwascalculatedconsideri
4、ngtemperatureandstrainratedependentflowstress.Thecomputedresultsshowedsignificantviscoplasticflownearthetoolsurface,andconvectionwasfoundtobetheprimarymechanismofheattransferinthisregion.Also,theresultsdemonstratedthestrongthree-dimensionalnatureofthetransportofheatandmass,reaffirmingt
5、heneedforthree-dimensionalcalculations.Thestreamlinesofplasticflowindicatedthatmaterialwastransportedmainlyalongtheretreatingside.Thecomputedtem-peratureswereingoodagreementwiththecorrespondingexperimentallydeterminedvalues.Ó2006PublishedbyElsevierLtdonbehalfofActaMaterialiaInc.Key
6、words:Frictionstirwelding;Numericalmodeling;Mildsteel;Plasticflow;Heattransfer1.Introductionsimultaneouslyoccurringphysicalprocessesaffecttheheat-ingandcoolingratesandthestructureandpropertiesofFrictionstirwelding(FSW)isasolid-stateweldingpro-theweldedjoints.cess.Thetoolusuallyhasal
7、arge-diametershoulderandaTheFSWprocesswasdiscoveredin1991atTWI[1].smallerthreadedpin.TheplatestobeweldedarealignedSincethenFSWhasbeenwidelystudiedbothexperimen-togetherandclampedusingfixtures.Acylindricalholeistallyandtheoreticallytobetterunderstandboththeweld-drilledatoneendofthew
8、orkpieceonthecenterlineandingproc
