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外文翻译---花键轴开模冷挤压中局部镦粗问题的解决和相关光塑性研究 英文版.doc

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外文翻译---花键轴开模冷挤压中局部镦粗问题的解决和相关光塑性研究 英文版.doc

JournalofMaterialsProcessingTechnology1142001185±188SolutiontothebulgingproblemintheopendiecoldextrusionofasplineshaftandrelevantphotoplastictheoreticalstudyZhaohuiHuanga,,PeifuFubaForgingDivision,BeijingInstituteofAeronauticalMaterials,Beijing100095,PRChinabDepartmentofMaterialsScienceandEngineering,JilinUniversityofTechnology,Changchun130025,PRChinaReceived21June1999AbstractComparedwithotherformingmethods,thecoldextrusionofasplineshafthasmanyadvantages.However,theproblemofbulgingatthedieentrance,whichisnotyetsolved,resiststhewideapplicationofthisnetornearnetshapetechnology.Tosolvethebulgingproblem,themethodofaddingaguidinglengthuponthedieentranceinthediedesigningisputforwardinthispaper.Onthebasisofphotoplasticexperiments,atheoreticalanalysismodelofthesolutionisfound,andthecalculatingmethodfortheguidinglengthisalsosubmitted.Theappropriateprocessingparametersarechosenbasedonthecalculatedresults,andasatisfactoryeffecthasbeenobtainedintheactualprocessing.2001ElsevierScienceB.V.Allrightsreserved.KeywordsSplineshaftColdextrusionBulgingPhotoplasticity1.IntroductionInrecentyears,netornearnetshapetechnologieswiththeirpossibilitiesofproducingpartswithreadytobuiltinfunctionalsurfaceshavebecomemoreandmoreinteresting,evenfortheproductionofcomplexparts.Thecoldextrusionofasplineshafthasagreaterpotentialthancutting,¯atdiethreadrollingandrolling,becauseofitsmanyoutstandingadvantagessuchasthesavingofrawmaterials,highproductivity,superiorproductqualityandlowcost.However,thediedesignandthechoiceoftheprocessparametersrelyonempiricalfactorsduetothelackofsystematicanalysisandsothebilletusuallybulgesatthedieentrance,whichleadstothefailureofextrusionintheactualprocess.Recently,thisbulgingproblemhasbeenmainlysolvedbyexpensivetrialanderrorinmajorplants,whichlimitsgreatlytheapplicationofthisadvancedprocess.Thecalculationoftheformingforceandtheparametersofformingprocessofthecoldextrusionofasplineshafthavebeenstudiedbysomeresearchers1±5,butstudyonthebulgingproblemhasnotbeenreported.Thispaperputsemphasisonthesolutionofthebulgingproblem,andrelevantexperimentalandtheoreticalanalysis.Correspondingauthor.Emailaddresshuaping.xiongbiam.ac.cnZ.Huang.2.Theformationofbulginganditssolution2.1.HowtoavoidbulgingDuringtheprocessingoftheopendieextrusionofasplineshaft,thatpartofthebilletwhichhasnotyetenteredtheplasticzoneofthedieandcannotberestrainedbythedie,shouldnotbedeformed.Thustheformingconditionofopendieextrusionispsswherepistheunitformingforceonthecrosssectionofthebillet,andssistheyieldlimitoftheextrudedmaterial.Ifpss,thenpartofthebilletinfrontoftheentranceoftheconicaldiewillbedeformedfirstandsubsequentlybulged.Finally,themetalflowisrestrictedandtheopendieextrusionfails.Whichparameteristhemajorfactorfordiedesigningandhowtojudgethesuccessorfailureoftheopendieextrusionisaproblem.Somestudiesaboutthisproblemweredonewiththeupperboundmethod6,7.Whentheotherparametersarefixed,therearetwocriticalvaluesofsemiconeangleacr1andacr2acr1acr2,consequently,bulgingcannotbeavoided.Onthebasisofexperiments,afeasiblemethodofsolvingthebulgingproblemissubmittedasfollowsaddingaguidinglengthL0atthedieentrancetorestraintheexpansionofthebulgingsothattheotherpartsofthebilletareextrudedcontinuously.Correspondingexperimentshavebeendone,beginningwithL040mm,andthendecreasingL0progressivelyiftheextrusionissuccessfuluntiltheextrusionfails.OtherparametersareasfollowsR1radiusoftoothroof101mmR2radiusoftoothroot79mmbtoothwidth395mmztoothnumber6RA3059.Thematerialusedis20CrMosteellubricatedbyphosphatecoating.TheresultsarelistedinTable1.WhenL031mm,theidealsplineshaftcanbeobtained.ForL028mm,itsconditionisunstableasshowninFig.2a,alittlebulgingappearsatthedieentrance,andtherearesome®necracksonthesurfaceofTable1EffectofdifferentguidinglengthonformingabilityGuidinglengthL0mm43.73.43.12.82.5FormingabilityOKOKOKOKUnsteadyPoorastearsandburnsonthesurfaceoftheextrudedsplineandonlyashortlengthofsplinedshaftiscompleted.Withtheincreaseofbulging,normalextrusionfailsasFig.2b.ItisconcludedfromabovethatasuitableguidinglengthL0canrestrainbulging,andenableextrusiontobecarriedoutsuccessfully,evenifaisoutsidetheformabilityrangeaacr2.3.TheoreticalanalysismodelandcalculationmethodfortheguidinglengthL03.1.PhotoplasticexperimentsIto8stated®rstlythatpolycarbonatePCcanreplacecelluloidasaphotoplasticmodelmaterial,andPCalsocansimulatecoldforming.Inthispaper,theauthorsselectaphysicalsimulationmethod9tostudytheabovesolutiontothebulgingproblem,theaimbeingtoobtainatheoreticalanalysismodelbytheobjectivesimulatedmethod.ThesimulatedmaterialisPC,andtwodieangles,a30anda45,arechosen.Fig.3aandbpresentstheisochromaticpatternsforalongitudinalslicewithoutbulginga30andtheisochromaticpatternsforalongitudinalslicewithbulginga45.Itisfoundthatwhenaacr2a45,thebilletbecomesbulgeduponenteringthedieangle,andthefringesinthiszoneareveryclose,signifyingthataconcentrationofstrainoccurs.However,uponthebulging,thereisalsothezoneofzerodegreefringes.AsliceofcrosssectionatthebulgingisillustratedinFig.3c.Therearesixsymmetricalzonesoffringes,whilsttheothersarezonesofzerodegreefringes,wherenoplasticdeformationoccurred.Thediameterofthesixfringedzonesislargerthanthatoftheotherzones,becauseinthesezones,theextrudedbilletisdeformedintheradialdirection,andexpandedtotheguidinglengthinterface,leadingtobulging.Z.Huang,P.Fu/JournalofMaterialsProcessingTechnology1142001185±188Fig.4.Thetheoreticalanalysismodeloftheguidinglength.187Fig.3.Thefringesofphotoplasticexperimentsatheisochromaticpatternsforalongitudinalslicewithoutbulginga30btheisochromaticpatternsforalongitudinalslicewithbulginga45ctheisochromaticpatternsforatransversesliceatthebulging.3.2.TheoreticalanalysismodelThetheoreticalanalysismodelofthesolutiontobulgingisthuspresentedonthebasisoftheabovephotoplasticexperimentsinFig.4.Whenaacr2,themetaldistortionissoseriousthatpss,resultinginbulging.WhenaguidinglengthL0isaddedatthedieentrancetorestraintheexpansionofthebulging,thebulgedmetalformsadeadzone.Theotherpartshearsthroughtheeasiest¯owingchannelalsonamedthedeadzoneanglea1,whichwillminimizethetotalpowerrequiredwhenadeadzoneforms.Inthiswaythenormalopendieextrusioncanbeaccomplishedsmoothlyevenifaacr2.Duetoa1acr2.Themetalinthedeadzoneadherestothedieandcannotmovesothatashearingsurfaceisgeneratedattheconeanglea1,andthedeadzoneactsasthediesurfacethroughwhichthemetalis¯owing.Atthesurfacea1,thefrictionbetweenthedeadmetalandthe¯owingmetalisnothigherthantheshearingstrengthofthemetalusedts0310,11.Then,whenaacr2,aismadeastheoptimalparameter,andtheoriginalfrictionconditionisreplacedusingm1.SubstitutingthesefactorsintotheUBM5,6,thevalueofa1canbeobtainedwhenminimizingthepvalue,andtherefore,thevalueofL0limisdeterminedbycalculatingthedistanceofa1andaintheaxialdirection.4.ExperimentsandanalysisInthissection,thetheoreticalanalysismodelandcalculationmethodforL0limareveri®edbyexperiment.Threedifferentsizesofsplineareused,andthreeexperimentalmaterialsareappliedpolycabonate,20CrMosteeland20CrMnTisteel.Theirstress±straincurvesareobtained188Table2Z.Huang,P.Fu/JournalofMaterialsProcessingTechnology1142001185±188andthatthetheoreticalanalysisandcalculationmethodareComparisonofexperimentalvalueswithcalculatedvaluesExperimentalmaterialPolycarbonate20CrMosteel20CrMnTisteelExperimentalvalue5.602.863.42ofL0limmmCalculatedvalueof7.203.524.52L0limmmError28.6231.3032.25Fig.5.Splineshaftsawithoutandbwithadeadzone.bytensiletesting.TherangeofcriticalangleisgainedbytheUBM6,7,thenanexperimentaldieanglelargerthanthecriticalangleischosenandthecoldextrusionofasplineiscarriedout.TheexperimentalvaluesandcalculatedresultsarecomparedinTable2.Thecalculatedresultsagreewellwiththeexperimentalresults,theerroroftheUBMbeing30orso.ConsideringthatthevaluescalculatedbytheUBMarealwaysgreaterthanorequaltotheactualvalues,theauthorsbelievethatitissafetochoosethesevaluesintheengineeringdesign.Finally,theactualformingprocessofthecoldextrusionofthesplineshaftofamotorcycletransmissionisdoneonthebasisoftheaboveresults.Here20CrMnTisteelisused,andtheparametersofthestraightsidesplinewith6teethareasfollowsR110125mm,R2832mm,b4825mm.Themaximumcriticalsemiangleisacr22668valueobtainedfromtheUBM7.Intheexperiments,twodieangles,a30anda45,arechosen.Whena45,theguidinglengthisL0lim481mm7.Intheexperiments,theguidinglengthL0,4.9mm,isaddedinsuchacondition.Twogroupsofbilletsareannealedforsoftening,andlubricatedbyphosphatecoating,andthencoldextruded.TheresultsareshowninFig.5.Fig.5agivesthecriticalstatea30,wherenobulgingappears.Alloftheaboveaccordswellwiththecalculatedresults.InFig.5b,thedieangleisa45largerthanacr2,andthereisadeadmetalzoneuponthedieangleentrance,exhibitingawhitezoneontheextrudedshaftbecausethelocallubricantsaretornaway.Withenoughguidinglength,thecoldextrusionofasplineshaftcanbeaccomplishedsmoothly.Aboveexperimentsalsoverifythatthesolutionmethodofbulgingisfeasible,reasonable.5.Conclusions1.Themethodofsolvingthebulgingproblemisputforwardasfollowsaddingaguidinglengthatthedieentrancetorestraintheexpansionofthebulgingsothattheextrusioncanbeaccomplishedsuccessfully.2.Thetheoreticalanalysismodelofthesolutiontothebulgingproblemisfound.Whenaacr2,theguidinglengthrestrainsbulgingsothatthebulgedmetalformsadeadzone,whiletheotherpartshearsthroughtheeasiestflowingchannel,andthensoundmetalflowcontinues.3.ThecalculationmethodforL0limisalsopresented.Whenaacr2,m1isselectedandaisusedasoptimalparameter.AllofthesefactorsaresubstitutedintotheUBM,whenminimizingthepvalue,theoptimalangleisjusta1,andL0limisdeterminedbycalculatingthedistancebetweena1andaintheaxialdirection.4.Thegoodagreementofthecalculatedresultswiththetheoreticalvaluesshowsthatnotonlyisthesolutionmethodofthebulgingproblemfeasible,butalsotherelevanttheoreticalanalysisandcalculationarereliable.References1S.Fujikawa,H.Yoshioka,S.Shimamura,Coldandwarmforgingapplicationsintheautomotiveindustry,J.Mater.Process.Technol.351992317±341.2H.Hirschrogel,V.Donmelen,Someapplicationsofcoldandwarmforging,J.Mater.Process.Technol.351992343±356.3Z.C.Zhang,J.Li,Experimentalstudyonopendiecoldextrusionformingtechniqueforinvolatesplineshaft,ChineseJ.Mech.Eng.919966±12inChinese.4L.L.Jia,Anupperboundanalysisforextrusionofspline,inAdvancedTechnologyofPlasticity,ProceedingoftheFourthInternationalConferenceonTechnologyofPlasticity,Beijing,China,1993,pp.582±586.5D.Y.Yang,C.H.Han,M.U.Kim,Ageneralizedmethodforanalysisofthreedimensionalextrusionofarbitrarilyshapedsections,Int.J.Mech.Sci.281986517±534.6P.F.Fu,Z.H.Huang,Studyontheformingconditionofopendiecoldextrusionforsplineshaft,J.Agric.Mech.281997129±133inChinese.7Z.H.Huang,Ph.D.Thesis,JilinUniversityofTechnology,China,1998inChinese.8K.Ito,Newmodelmaterialsforphotoelasticityandphotoplasticity,Agric.Mech.21962373±376.9Z.H.Huang,P.F.Fu,Threedimensionalphotoelasticstudyonthedeformationofasplineshaftincoldextrusion,J.Exp.Mech.14199935±40inChinese.10B.Avitzur,MetalFormingProcessandAnalysis,LehighUniversity,NewYork,1979,pp.50±20011B.Avitzur,HandbookofMetalformingProcess,LehighUniversity,NewYork,1983,pp.61±130

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