挤压模具概述外文资料翻译.docx
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挤压模具概述外文资料翻译.docx
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挤压模具概述外文资料翻译
外文资料翻译
Overviewofadaptablediedesignforextrusions
W.A.Gordon.C.J.VanTyne.Y.H.Moon
ABSTRACT
Theterm“adaptablediedesign”isusedforthemethodologyinwhichthetoolingshapeisdeterminedormodifiedtoproducesomeoptimalpropertyineitherproductorprocess.Theadaptablediedesignmethod,usedinconjunctionwithanupperboundmodel,allowstherapidevaluationofalargenumberofdieshapesandthediscoveryoftheonethatproducesthedesiredoutcome.Inorderfortheadaptablediedesignmethodtobesuccessful,itisnecessarytohavearealisticvelocityfieldforthedeformationprocessthroughextrusiondiesofanyshapeandthevelocityfieldmustallowflexibilityinmaterialmovementtoachievetherequiredmaterialflowdescription.Avarietyofcriteriacanbeusedintheadaptablediedesignmethod.Forexample,dieswhichproduceminimaldistortionintheproduct.Adoubleoptimizationprocessisusedtodeterminethevaluesfortheflexiblevariablesinthevelocityfieldandsecondlytodeterminethedieshapethatbestmeetsthegivencriteria.Themethodhasbeenextendedtothedesignofdiesfornon-axisymmetricproductshapes.
©2006ElsevierB.V.Allrightsreserved.
Keywords:
Extrusion;Diedesign;Upperboundapproach;Minimumdistortioncriterion
1.Introduction
Newmetalalloysandcompositesarebeingdevelopedtomeetdemandingapplications.Manyofthesenewmaterialsaswellastraditionalmaterialshavelimitedworkability.Extrusionisametalworkingprocessthatcanbeusedtodeformthesedifficultmaterialsintotheshapesneededforspecificapplications.Forasuccessfulextrusionprocess,metalworkingengineersanddesignersneedtoknowhowtheextrusiondieshapecanaffectthefinalproduct.Thepresentworkfocusesonthedesignofappropriateextrusiondieshapes.Amethodologyispresentedtodeterminedieshapesthatmeetspecificcriteria:
eithershapeswhichpro-duceproductwithoptimalsetofspecifiedproperties,suchasminimumdistortionintheextrudate,orshapeswhichproduceproductbyanoptimizedprocess,suchasminimumextrusionpressure.Theterm“adaptablediedesign”isusedforthemethodnologyinwhichthedieshapeisdeterminedormodifiedtoproducesomeoptimalpropertyineitherproductorprocess.Thisadaptablediedesignmethod,usedinconjunctionwithanupperboundmodel,allowstherapidevaluationofalargenumberofdieshapesandthediscoveryoftheonethatcanoptimizethedesiredoutcome.Thereareseveralconditionsthatneedtobemetfortheadaptablediedesignmethodtobeviable.First,ageneralizedbutrealisticvelocityfieldisneededforuseinanupperboundmodeltomathematicallydescribetheflowofthematerialduringextrusionthroughdiesofanyshape.Second,arobustcrite-
rionneedstobeestablishedfortheoptimizationofthedieshape.Thecriterionmustbeuseablewithinanupperboundmodel.Thefulldetailsofthemethodarepresentedelsewhere[1–6].Inthepresentpaper,followingareviewofpreviousmodelsforextrusion,theflexiblevelocityfieldforthedeformationregioninadirectextrusionwillbebrieflypresented.Thisvelocityfieldisabletocharacterizetheflowthroughadieofalmostanyconfiguration.Theadaptableequation,whichdescribesthedieshape,isalsopresented.Theconstantsinthisdieshapeequationareoptimizedwithrespecttoacriterion.Thecriterion,whichcanbeusedtominimizedistortion,ispresented.Finally,theshapeofanadaptabledie,whichproducesofanextrudedproductwithminimaldistortion,ispresented.Theobjectiveofthepresentpaperistoprovideabriefoverviewoftheadaptablediedesignmethod.
2.Background
2.1.Axisymmetricextrusion
Numerousstudieshaveanalyzedtheaxisymmetricextrusionofacylindricalproductfromacylindricalbillet.Avitzur[7–10]proposedupperboundmodelsforaxisymmetricextrusionthroughconicaldies.ZimermanandAvitzur[11]modeledextrusionusingtheupperboundmethod,butwithgeneralizedshearboundaries.FiniteelementmethodswereusedbyChenetal.[12]andLiuandChung[13]tomodelaxisymmetricextrusionthroughconicaldies.ChenandLing[14]andNagpal[15]analyzedotherdieshapes.Theydevelopedvelocityfieldsforaxisymmetricextrusionthrougharbitrarilyshapeddies.Richmond[16]wasthefirsttoproposetheconceptofastreamlineddieshapeasadieprofileoptimizedforminimaldistortion.Yangetal.[17]aswellasYangandHan[18]developedupperboundmodelsforstreamlineddies.Srinivasanetal.[19]proposedacontrolledstrainratedieasastreamlinedshape,whichimprovedtheextrusionprocessformaterialswithlimitedworkability.LuandLo[20]proposedadieshapewithanimprovedstrainratecontrol.
2.2.Distortionanddieshapeanalysis
Numerousanalyticalandexperimentalaxisymmetricextrusioninvestigationshaveexaminedthedieshapeandresultingdistortion.Avitzur[9]showedthatdistortionincreaseswithincreasingreductionanddieangleforaxisymmetricextrusionthroughconicaldies.ZimermanandAvitzur[11]andPanetal.[21]proposedfurtherupperboundmodels,includingoneswithflexibilityinthevelocityfieldtoallowthedistortedgridtochangewithfriction.Theyfoundthatincreasingfrictioncausesmoredistortionintheextrudedproduct.Chenetal.[12]con-firmedthatdistortionincreaseswithincreasingreduction,dieangle,andfriction.Otherresearchworkhasfocusedonnon-conicaldieshapes.Nagpal[15]refinedtheupperboundapproachtostudyalter-nativeaxisymmetricdieshapes.ChenandLing[14]usedtheupperboundapproachtostudytheflowthroughcosine,elliptic,andhyperbolicdiesinanattempttofindadieshape,whichminimizedforceandredundantstrain.RichmondandDevenpeck[16,22,23],insteadofassumingaparticulartypeofdieshape,decidedtodesignadiebaseduponsomefeatureoftheextrudedproduct.Usingsliplineanalysisandassumingidealandfrictionlessconditions,Richmond[16]proposedastream-linedsigmoidaldie,whichhassmoothtransitionsatthedieentranceandexit.Thestreamlineddieshapeisthebasisformanyeffortsinaxisymmetricextrusiondiedesign.Yangetal.[17],YangandHan[18],andGhulmanetal.[24]developedupperboundmodelsusingstreamlineddies.Certainmaterials,suchasmetalmatrixcomposites,canbesuccessfullyextrudedonlyinanarroweffectivestrainraterange,leadingtothedevelopmentofcontrolledstrainratedies.Thecontrolofthestrainrateinthedeformationzonecamefromstudiesthatshowedfiberbreakageduringtheextrusionofwhiskerreinforcedcompositesdecreaseswhenpeakstrainratewasminimized[25].InitiallydevelopedbySrinivasanetal.[19],thestreamlineddieshapeattemptstoproduceaconstantstrainratethroughoutalargeregionofthedeformationzone.LuandLo[20]usedarefinedslabmethodtoaccountforfrictionandmaterialpropertychangesinthedeformationzone.Kimetal.[26]usedFEMtodesignanaxisymmetriccontrolledstrainratedie.TheyusedBeziercurvestodescribethedieshapeandminimizedthevolumetriceffectivestrainratedeviationinthedeformationzone.
2.3.Three-dimensionalnon-axisymmetricextrusionanalysis
Boththeupperboundandfiniteelementtechniqueshavebeenusedtoanalyzethree-dimensionalnon-axisymmetricextrusions.Nagpal[27]proposedoneoftheearliestupperboundanalysesfornon-axisymmetricextrusion.UpperboundandfiniteelementmodelsweredevelopedBasilyandSansome[28],Boeretal.[29],andBoerandWebster[30].Kiuchi[31]studiednon-axisymmetricextrusionsthroughstraightconvergingdies.GunasekeraandHoshino[32–34]usedanupperboundmodeltostudytheextrusionofpolygonalshapesthroughconvergingdiesaswellasthroughstreamlineddies.WuandHsu[35]proposedaflexiblevelocityfieldtoextrudepolygonalshapesthroughstraightconvergingdies.Hanetal.[36]createdavelocityfieldfromtheirpreviousaxisymmetricupperboundmodel[37]inordertostudyextrusionthroughstreamlineddiesthatproducedclover-shapedsections.Yangetal.[37]appliedageneralupperboundmodeltostudyextrusionofellipticandrectangularsections.HanandYang[38]modeledtheextrusionoftrocoidalgears.Yangetal.[39]alsousedfiniteelementanalysistocon-firmtheexperimentalandupperboundanalysisofthecloversections.Non-axisymmetricthree-dimensionalextrusionshavebeenstudiedfurtherbyusingupperboundelementaltechnique[40]andspatialelementaryrigidzones[41,42].Streamlineddieshavebeentheproposeddieshapeformostthree-dimensionalextrusion.Theshapeofthediebetweentheentranceandexithasbeenselectedbyexperienceandfeelratherthanrigorousengineeringprinciples.Nagpaletal.[43]assumedthatthefinalpositionofapointthatwasinitiallyonthebilletisdeterminedbyensuringthatareareductionoflocalsegmentswasthesameastheoverallareareduction.Oncethefinalpositionofamaterialpointwasassumed,athirdorderpolynomialwasfitbetweenthedieentranceandexitpoints.Gunasekeraetal.[44]refinedthismethodtoallowforre-entrantgeometries.Ponalagusamyetal.[45]proposedusingBeziercurvesfordesigningstreamlinedextrusiondies.KangandYang[46]usedfiniteelementmodelstopredicttheoptimalbearinglengthforan“L”shapeextrusion.Studiesonthedesignofthree-dimensionalextrusiondieshavebeenlimited.Thecontrolledstrainrateconcepthasonlybeenappliedtoaxisymmetricextrusionsandnottothree-dimensionalextrusions[19,20,26].
3.Theadaptablediedesignmethod
Theadaptablediedesignmethodhasbeendevelopedandisdescribedindetailinaseriesofpapers[1–5].Themethodhasbeenex
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