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外文翻译--搅拌摩擦焊搅拌头在材料流动和焊缝形成时的作用 英文版.pdf

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外文翻译--搅拌摩擦焊搅拌头在材料流动和焊缝形成时的作用 英文版.pdf

MaterialsScienceandEngineeringA4852008367–374TheroleoffrictionstirweldingtoolonmaterialflowandweldK.Kumar,SatishInstituteformAbstracttoolinthereenfltogethergibasedis©2007ElsevierB.V.Allrightsreserved.K1.cessaluminiumjoiningwithnoconsumables.Ingeneral,theprocessiscarriedoutbyplungingarotatingFSWtoolintotheinterfaceoftworigidlyclampedsheets,untiltheshouldertouchesthesurfaceofthematerialbeingwelded,andtraversedalongtheweldline.Thefrictionalunderfrictionaldeformationethesimilarisgeometrytoolandmallystirturalafparenteterswhichcontrolsthematerialflowandheatinput,andinturnthequalityoftheweld.Buffaetal.2numericallyinvestigatedtheeffectoftoolpinangleonvariousweldzones,grainsizeandweldingforces,andtheyhadshownthatthereisagood09215093/doiheatanddeformationheatareutilizedforthebondingtheappliednormalforce1.Theprimaryheatsourceisheatfromtoolshoulderandsecondaryheatsourceisheatfromthetoolpin2.TheprocessandterminologyofFSWareschematicallyxplainedinFig.1.TheadvancingsideASisthesidewherevelocityvectorsoftoolrotationandtraversedirectionareandthesidewherethevelocityvectorsareoppositereferredasretreatingside.Theprocessparametersaretool,axialforce,toolrotationspeed,traversespeedandtiltangle.Tooltiltangleistheanglebetweenthetoolaxisthenormaltothesurfaceofthesheetsbeingwelded.Nor∗Correspondingauthor.Tel.918022932301fax918023600648.Emailaddresssatvkmecheng.iisc.ernet.inS.V.Kailas.agreementbetweentheresultsofexperimentandthemodel.TheexperimentalworkcarriedoutbyKumarandKailas7usingdifferenttoolgeometryexplainstheeffectofshoulderdiameter,pindiameterandpinprofilesonsizeandlocationofdefects,mechanicalpropertiesandfinalgrainsize.But,thereisnotenoughconceptualbackgroundavailableonFSWtooldesign.Inmostoftheresearcharticlesthetoolgeometryisnotreportedduetovariousreasons.AsMishraandMa8pointedout,mostofthetooldesignisbasedonintuitiveconcepts.ThefirststepinderivingtheconceptofFSWtooldesignistounderstandtheroleoftoolinfrictionstirweldformation.Insolidstatewelding,theacceptedprincipleofweldformationisstatedthatthebondingoccurs,whenapairofcontaminationfreesurfacesarebroughttogetherintherangeofinteratomicdistancesandtheforceutilizedforbondingistheinteratomicforce9.Inmostofthesolidstatewelding–seefrontmatter©2007ElsevierB.V.Allrightsreserved.10.1016/j.msea.2007.08.013DepartmentofMechanicalEngineering,IndianReceived30January2007receivedinrevisedInthisinvestigationanattempthasbeenmadetounderstandthemechanisminit.Thishasbeendonebyunderstandingthematerialflowpatternfrictionstirweldingtoolwiththebasematerialiscontinuouslyincreased.gimesinvolvedinthefrictionstirweldformationnamelypindrivtoformadefectfreeweld.TheetchingcontrastintheseregimesonthematerialflowcharacteristicsamechanismofweldformationeywordsFrictionstirweldingMaterialflowMechanismDefectsTooldesignIntroductionTheenvironmentfriendlyfrictionstirweldingFSWproisapotentialandprovenmethodforweldinghighstrengthalloys.ThissolidstatelocalizedthermomechanicalprocessispredominantlyusedforbuttandlapjointsformationV.Kailas∗ofScience,Bangalore560012,India30July2007accepted8August2007offrictionstirweldformationandtheroleoffrictionstirweldingtheweldproducedinaspecialexperiment,wheretheinteractionofTheresultsshowthattherearetwodifferentmodesofmaterialflowowandshoulderdrivenflow.Thesematerialflowregimesmergevesrisetoonionringpatterninfrictionstirwelds.Inadditiontothatproposed.,themicrostructuralinvestigationrevealsthatthefrictionweldmenthasfourdifferentregionsbasedonthemicrostrucfeatures,namelyweldnuggetWN,thermomechanicallyfectedzoneTMAZ,heataffectedzoneHAZandbaseormaterial3–6.Toolgeometryisconsideredtobeoneoftheprimeparam368K.Kumar,S.V.Kailas/MaterialsScienceandEngineeringA4852008367–374process,ing,thecontactinterfprocessisfyadditionalbodyarecoalescedture,theonlyysisthecomputationaltheFSWflomarkals.suitableorinitialmaterialtheand19offlocontribal.microstructuraltion20ringformationcofcylindersresultsintheonionringpattern.Fratinietal.20explainedthereasonfortheonionringpatternusingnumericalmodelthatthematerialenteringfromtheretreatingsideenterstheactionvolumeandrotatesatthebackofthetool.But,ingeneral,thereisnoexperimentalevidencethatconfirmsthemechanismofonionringformationproposedbytheresearchers.stir23grooformationandformationinsufinformationformation.posedstirresearch,markmechanismsand2.alloAl–Zn–MgturalalloThewithfrustumdiameterpinetryHDSweldingareThemachinebaseincreasingmaterialangleFig.1.Schematicoffrictionstirweldingprocessandterminology.likeforgewelding,diffusionwelding,frictionweldexplosivewelding,ultrasonicwelding,rollbonding,etc.,bondingisestablishedbygeneratingfreshmetaltometalbyeliminatingoxidelayersandimpuritiesfromtheaceunderrequiredpressureandtemperature10.Theseconditionsmodifythebasematerialinterfacetosatthesolidstateweldingcondition,anddonotgenerateanysurfacesinthematerial.Incontrast,duetothethirdtheFSWtoolinteractioninFSW,additionalinterfacesgeneratedduringtheprocess.Finally,allthesurfacesarewitheachotherbytheappliedpressureandtemperaandthus,thesoundsolidstateweldisproduced.Therefore,mechanismofweldformationinFSWwillbeclearlyknownwhentheroleoftoolisunderstood.ThematerialflowanalisanimportanttooltounderstandtheroleofFSWtoolonofweldformation.Thereareanumberofexperimentalstudies11–15,andwork16–18hasbeencarriedouttoanalyzematerialflow,anditisreportedthatthematerialflowiniscomplexanditisnotclearlyunderstood.Ingeneral,thewvisualizationstudieshavebeenconductedbyintroducingaermaterialintheweldline,orbyweldingdissimilarmateriAfterwelding,themarkermaterialpositionistracedbackbymeans,i.e.,Xrayradiographyortomography11,12differentialetchingprocedure13–15,andcomparedwithitsposition.But,ithasbeensaidthattheinsertionofmarkerintheweldlinecanalterthenatureofmaterialflowinweldduetodifferentmaterialflowcharacteristicsofthebasemarkermaterialsandintroductionofadditionalinterfaces.Ontheotherhand,thematerialflowindissimilarmaterialsdifferentflowpropertiescannotbecomparedwithmaterialwinfrictionstirweldsofsimilarmaterials.TheimportantutiontomaterialflowvisualizationisdonebyFratiniet20.Theyincorporatedthematerialflowandanalysiswithevolution.Aninterestingphenomenoninfrictionstirweldsisformaofringpattern.ThishasbeenstudiedbyFratinietal.andKrishnan21.Krishnan21explainedtheonionformationusingaclaymodel.Hepointedoutthattheofonionringisageometriceffect.Hestatedthatsemiylindricalsheetsofmaterialareextrudedduringeachrotationthetoolandcrosssectionalslicethroughsuchasetofsemilength4.6ofthepinInflothematerialTheotherimportantaspectisdefectformationinfrictionwelds.Kimetal.22andElangovanandBalasubramanianreportedexcessiveflashformation,cavity,tunneldefectandvelikedefects.Andfurthertheyconcludedthatthedefectisduetoinsufficientheatinput,excessiveheatinputabnormalstirring.Zangetal.19reportedthattheporeinafrictionstirweldedmagnesiumalloyisduetoficientpressureunderneaththeshoulder.But,thereisnoavailableontheroleoftoolgeometryondefectInthisinvestigationasimpleexperimentalmethodisprotoanalyzetheroleoffrictionstirweldingtoolonfrictionweldformationbyanalyzingthematerialflow.Inthisthematerialflowisanalyzedwithouttheinsertionofermaterial.Basedonobservationsmadeintheanalysis,offrictionstirweldformation,defectformationonionringformationareproposed.ExperimentalmethodsThebasematerialusedinthisstudyis7020T6.Aluminiumy7020isamediumstrengthprecipitationhardenablealloy,whichisusedinaerospaceindustryforstrucapplications.ThenominalchemicalcompositionoftheyisZn4.63wt.,Mg1.13wt.,andrestaluminium.basematerialdimensionis300mm75mm4.4mmsquareedges.Thetoolusedinthisstudyis4.2mmlongshapedpinof6mmtopdiameterand4mmbottomwith20mmdiameterflatshoulder.ThefrustumshapedprofileischosenaccordingtotheselfoptimizedtoolgeomsuggestedbyPradoandMurr24.ThetoolmaterialisH13,andishardenedto55HRC.Inthisinvestigation,speed,toolrotationspeedandbackwardtooltiltanglekeptconstantat80mm/min,1400rpm,and2◦,respectively.FSWtrialsarecarriedoutonakneetypeverticalmillingwithsquarebuttjointconfiguration.Theexperimentisconductedinsuchawaythatthetoolandmaterialinteractioniscontinuouslyincreasedbylinearlytheinterferencebetweentoolshoulderandthebasesurface.ThisisdonebykeepingthebackingplateatantotheweldlineasshowninFig.2.Initiallythe4.2mmtoolpinisplunged3.8mm,andthetoolplungingreachesmmbytheendoftheweld.Inordertoavoidthedamagethebackingplateanaluminiumsupportpieceiskeptbeneathworkpiece.Theideaoftheexperimentisthattheroleoftoolandshoulderonweldformationcanbeanalyzedseparately.ordertoexplaintheeffectoftoolinteractiononthematerialwandweldformationintermsofheatinputandtemperature,axialloadsaremeasuredforthecorrespondingtoolandbaseinteraction.K.Kumar,S.V.Kailas/MaterialsScienceandEngineeringA4852008367–374369Fig.2.Experimentaldetails.Thebackingplatewaskeptatananglesuchthattheaxialloadcanbelinearlyincreasedfrom4to10.9kNbylinearlyincreasingtheinterferencebetweentoolandmaterialbeingwelded.Afterwelding,metallographicsamplesarepreparedfromtheweldcouponatevery20mminterval.Standardmetallographicpracticeisfollowed,anddilutedKellersreagentisusedforetching.3.Resultsanddiscussion3.1.MaterialflowandweldformationFig.3showsthecrosssectionsoftheweldtakenatvarioustoolinterferencelevelswiththebasematerial,withincreasingaxialloads.Itcanbeseenthatthedefectsizereducesasthetoolinterferenceincreases.Itcanalsobenoticedthattheaxialloadincreasesasthetoolinteractionincreases.Aboveanormalloadof7.4kNFig.3f,defectshavedisappeared.AsBuffaetal.2reported,therequirementforfrictionstirweldingprocesstoproduceadefectfreeweldisbygeneratingsufficientamountoffrictionalheat,therebygeneratingrequiredtemperatureandhydrostaticpressureintheweldline.AsColegroveandShercliff18explained,theshoulderisthesourceoffrictionalheat,anditpreventsthematerialfromflowingoutoftheweldcavity.Inthepresentsetofexperiments,attheinitialstagesoftheweldingthetoolshoulderisnotinfullcontactwiththebasematerial,andhenceaxialloadisinsufficientforheatgeneration.Thefrictionalheatgeneratedinthisstageisduetotheinteractionoftheshoulderandtheflashmaterial,frictionalheatgeneratedbytheinteractionofthepinwiththebasematerialandheatgeneratedduetotheplasticofthedeformedmaterial.Theprimaryreasonforhavingdefectintheweld,attheinitialstages,wheretheaxialloadislessthan7.4kN,isthelackofshouldercontactwiththebasematerial.Whentheshouldercontactincreaseswiththebasematerialtheaxialloadincreases.Whentheaxialloadisabove7.4kN,thetransferredmaterialfromtheleadingedgeisconfinedintheweldcavity,andsufficientamountoffrictionheatandhydrostaticpressureisgeneratedtoproduceadefectfreeweld.Theotherobservationisthattheweldcrosssectionissymmetricabouttheweldlineuntiltheaxialloadexceedthe8.1kNFig.3a–f,andabovethisloadtheweldlosesitssymmetryFig.3gandh.ItisevidentfromFig.3gandhthatthebaseFig.3.Evolutionofadefectfreeweldasafunctionoftheshoulderinteractionwiththebasematerial.Arrowmarksindicatethepresenceofvoidsintheweld.370K.Kumar,S.V.Kailas/MaterialsScienceandEngineeringA4852008367–374materiallosesitssymmetrybecausethebasematerialfromtheretreatingsideisdrawnintotheweldnuggetregion.Itcanbenoticedthatthebasematerialmovementawayfromthepincanonlybeinfluencedbytheshoulder.Whenahardandasoftmaterialarerubbedagainsteachother25thesurfaceandsubsurfacematerialflowsinthedirectionofslidingandtheamountofmaterialflowisafunctionofcontactload.Consequently,infrictionstirwelds,whentheaxialloadincreasesaboveacriticalvaluethesubsurfacematerialflowbecomesintense.Havingthebackwardtooltilt,thecontactpressureinthetrailingedgeofthetoolishigher,andhencethereisbasematerialmovementbeneaththeshoulderinthedirectionoftoolrotation.ThesimilarresulthasbeenreportedbyFratinietal.thatthetoolrotationmovesthematerialfromretreatingsidetoadvancingsideandthefluxisintenseatthebackofthetoolneartheshoulder20.Hence,thefrictionstirweldsareasymmetricabouttheweldlinewhentheaxialloadincreasesaboveacriticalvalueFig.3gandh.ThemagnifiedviewsofadvancingsidesoftheweldcrosssectionsareshowninFig.4.Thefiguresshowthatmorematerialflowstowardstheadvancingsideneartheshoulderasthetoolshoulderandbasematerialinteractionincreasesduetoconfinementoftransferredmaterialwithintheweldcavity.ButthematerialflowbelowcertaindepthinthethicknessZaxisisnotaffectedbytheincreasinginteractionofthetoolshoulder.ItcanbenoticedinFig.4thatthematerialbelowthepartingline,indicatedbythedottedlines,remainsunaffectedbytheaxialload.Thisindicatesthattheflowabovethepartinglineisinfluencedbythetoolshoulderwhilebelowthepartinglineisdrivenbypinalone.Thepindrivenmaterialflowoccursduringtheinteractionofbasematerialwiththetoolpinintheweldcavity.WhentheFig.indicatebetween4.Presenceofpinandshoulderdrivenmaterialflows.Thearrowmarkspinandshoulderdrivenmaterialflowregions.Notethattherelativepositionthedirectionofmaterialflow.Thedottedpartinglinesindicateboundaryofpindrivenlayerisunchanged.

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