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外文翻译--有限元模拟的高速硬车削 英文版.pdf

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外文翻译--有限元模拟的高速硬车削 英文版.pdf

ORIGINALARTICLEOnthefiniteelementmodellingofhighspeedhardturningA.G.MamalisJ.KundrákA.MarkopoulosD.E.ManolakosReceived7November2006/Accepted25May2007/Publishedonline14August2007SpringerVerlagLondonLimited2007AbstractTheresultsreportedinthispaperpertaintothesimulationofhighspeedhardturningwhenusingthefiniteelementmethod.Inrecentyearshighspeedhardturninghasemergedasaveryadvantageousmachiningprocessforcuttinghardenedsteels.Amongtheadvantagesofthismodernturningoperationarefinalproductquality,reducedmachiningtime,lowercostandenvironmentallyfriendlycharacteristics.Forthefiniteelementmodellingacommercialprogramme,namelytheThirdWaveSystemsAdvantEdge,wasused.Thisprogrammeisspeciallydesignedforsimulatingcuttingoperations,offeringtotheusermanydesigningandanalysistools.Inthepresentanalysisorthogonalcuttingmodelsareproposed,takingseveralprocessingparametersintoaccountthemodelsarevalidatedwithexperimentalresultsfromtherelevantliteratureanddiscussed.Additionally,obliquecuttingmodelsofhighspeedhardturningareconstructedanddiscussed.Fromthereportedresultsusefulconclusionsmaybedrawnanditcanbestatedthattheproposedmodelscanbeusedforindustrialapplication.KeywordsMachining.Finiteelementmethod.Hardturning1IntroductionHardturning,amachiningoperationusedfortheprocessingofhardmaterialssuchashardenedsteels,hasbeenbroughtintotheforefrontofmodernmetalcuttingoperationswiththeincreasingdemandformanufacturinghighqualitycomponents,e.g.,gears,shafts,bearings,diesandtools,fromthesekindsofmaterials.Cuttingtoolsemployedinhardturningaremadeofspecializedtoolmaterials,suchascubicboronnitriteCBN,thatareabletoovercometheproblemsexperiencedduringtheprocess1.Thesecuttingtoolsareidealformachiningironbasedmaterialsattheseverecuttingconditionsassociatedwithhardturningtheypossessexquisiteproperties,evenatelevatedtemperatures,allowingfortheirapplicationathighcuttingspeedsandwithouttheuseofanycuttingfluids2bydrycuttingnotonlyenvironmentallyfriendlycharacteristicsareattributedtotheprocess,butalsocostreductioncanbeattainedbyomittingbuyinganddisposalcostsofthecuttingfluids3–5.Inadditionthecombinationofhardturningandhighspeedmachiningisprovedtobeveryadvantageoussinceagreatreductioninprocessingtimecanbeachieved1.Hardturningisveryadvantageousforawidespectrumofapplicationsandisalsoconsideredasanalternativeforavarietyofprocesses,sincethesinglestepsuperfinishhardturningcanreplacetheabrasiveprocesses,traditionallyusedasfinishingoperations,ornontraditionalprocesses,suchaselectricaldischargemachiningEDM,inmachininghardparts,offeringaccuracyequaltoorbetterthanthatprovidedsofar,flexibilityandconsiderablemachiningtimeandcostreduction4–7.Note,however,thathardturninghasnotbeenintroducedintomodernindustryasmuchasitshouldbe,mainlybecauseofphenomenasuchasrapidtoolwearorcrackingIntJAdvManufTechnol200838441–446DOI10.1007/s0017000711149A.G.MamalisA.MarkopoulosD.E.ManolakosManufacturingTechnologyDivision,NationalTechnicalUniversityofAthens,Athens,Greeceemailmamaliscentral.ntua.grJ.KundrákDepartmentofProductionEngineering,UniversityofMiskolc,Miskolc,Hungaryandchippingofthecuttingedgeduetoextremepressureandtemperatureimposedonthecuttingtool,whichleadtopoormachiningresults8.Furthermore,asanovelmachiningprocess,itneedstobefurtherstudiedsothatitmaybeoptimized.Mostresearchworkislimitedtoexperimentalresults,but,also,themodellingofhardturningcanprovideusefuldatatobetterunderstandingtheprocess.Numericalmodellingand,especially,thefiniteelementmethodFEMhavebeenwidelyusedinthepastfortheanalysisandthepredictionofthecuttingperformanceinmachiningoperations.FEMhasbeenaverypowerfultoolinthecuttingtechnologyandcanbeappliedtohighspeedhardturningaswell.InthepresentpaperFEMisemployedinordertosimulatedryhighspeedhardturning,investigatingtheinfluenceofthecuttingspeedontheperformanceofthecuttingoperationandpredictingthecrucialprocessingparameters,someofthembeingsometimesverydifficulttobemeasuredorcalculatedotherwise,e.g.,temperaturefieldswithintheworkpieceandthetoolduringtheprocess.However,hardturningisarathercomplexprocess,withcuttingconditionsthataredifferentfromconventionalturningand,thereforeitisdesirabletotakeintoaccountsomespecialcharacteristicsforthispurpose,theFEMprogrammeThirdWaveAdvantEdge,whichisspeciallydesignedtosimulatecuttingoperations,isused.Forthesimulationofhardturningbothanorthogonalandanobliquecuttingmodelareproposed.2FiniteelementmodellingSimulationsofvariousmachiningoperationsusingthefiniteelementmethodhavebeenreportedoverthelastthreedecadesinReferences9,10acollectionofsuchpaperscanbefound.Thefirstmodelsthatappearedinthe1970susedtheEulerianformulationformodellingorthogonalcutting.Inthisapproachthefiniteelementmeshisspatiallyfixedandthematerialflowsthroughit,inordertosimulatethechipformation.Thecomputationaltimeinsuchmodelsisreduced,duetothefewelementsrequiredformodellingtheworkpieceandthechip,anditismainlyusedforsimulatingthesteadystateconditionofthecuttingprocess.Theelementsdonotundergoseveredistortion,sincethemeshisaprioriknown,butthisformulationrequirescomplexprogramming.Furthermore,experimentaldatamustbeonhandpriortotheconstructionofthemodelinordertodeterminethechipgeometry.Althoughthisformulationisstillutilizedbysomeresearchers,theupdatedLagrangianformulationhasbeenproposedandismorewidelyusedtoday.Inthisapproach,theelementsareattachedtothematerialandtheundeformedtoolisadvancedtowardstheworkpiece.Fortheformationofthechip,achipseparationcriterioninfrontofthetooledgeisapplied.Therearemanycriteriaproposedsofarwhichcanbegeometricorphysicalandmayinvolveforexampleacriticaldistancebetweenthetoolandtheworkpiecewhenthetoolreachesthiscriticaldistancefromtheworkpiecetheelementsaheadofthetooledgearedividedandthusthechipisformed.Otherseparationcriteriapertaintocriticalvaluesofe.g.,stressorstraininordertoinitiatethechipformationandevencrackpropagationcriteriahavebeenreportedforthisprocedure.Adisadvantageofthismethodisconnectedtothelargemeshdeformationobservedduringthesimulationduetotheattachmentofthemeshontheworkpiecematerial,themeshisdistortedbecauseoftheplasticdeformationinthecuttingzone.Inordertoovercomethisdisadvantagecontinuousremeshingandadaptivemeshingareusuallyapplied,increasingconsiderablytherequiredcalculationtime.Nevertheless,theadvancesincomputershavemadeitpossibletoreducethetimeneededforsuchananalysistoacceptablelevels.NotethatanarbitraryLagrangianEulerianformulationALEhasalsobeenproposedwiththeaimofcombiningtheadvantagesofthetwomethods,butitisnotaswidelyused.Mostofthemodellingworkpublishedsofarpertainsto2Dmodelsoforthogonalcutting,while3Dmodelsareratherrareintherelevantliterature.Thatismainlybecause,eventhough3Dcuttingismorerealistic,sincecuttingis3Dinnature,itrequiresamuchmorecomplexconsiderationofworkpieceandcuttingtoolgeometry,contactpropertiesand,ofcourseadditionalcomputationaltime.Inparticular,theworkdedicatedtohardturningisevenmorelimited11–15.ThemodelsprovidedbelowaredevelopedemployingtheThirdWaveAdvantEdgesoftware,whichintegratesspecialfeaturesappropriateformachiningsimulation.Theprogrammemenusaredesignedinsuchawaythattheyallowtheusertominimizethemodelpreparationtime.Furthermore,itincludesawidedatabaseofworkpieceandtoolmaterialscommonlyusedincuttingoperations,offeringalltherequireddataforeffectivematerialmodelling.TheAdvantEdgecodeisaLagrangian,explicit,dynamiccode,whichcanperformcoupledthermomechanicaltransientanalysis.TheprogramappliesadaptivemeshingandFig.1Orthogonalcuttingmodelschematicdiagram442IntJAdvManufTechnol200838441–446continuousremeshingforchipandworkpiece,allowingforaccurateresults.ForananalyticaldiscussiononthenumericaltechniquesusedintheprogrammeandacomprehensivepresentationofitsfunctionsseeReference16.3Resultsanddiscussion3.1OrthogonalcuttingmodelsTheorthogonalcuttingschematicdiagramusedintheprogrammeisshowninFig.1.Thedepthofcutisperpendiculartotheplaneshowninthefigureandintheplanestraincase,itisconsideredtobelargeincomparisontothefeed.InthepresentanalysistheworkpiecematerialistheAISIH13hotworktoolsteelanditslengthistakenequaltol3mm.ThetoolmaterialisCBNandthemodellingoftoolchipinterfacefrictionisbasedonCoulombsfrictionlaw,withfrictioncoefficientsetconstantatthevalueμ0.5.Acuttingtool,with−5°rakeangle,5°clearanceangleand0.02mmcuttingedgeradius,isusedfortheanalysis.Furthermore,thefeedistakenequaltof0.05mm/rev,whilethreedifferentcuttingspeeds,namelyvc200,250and300m/min,areconsidered.InFig.2aandbtheinitialmeshandatypicalmeshcreatedafterthetoolhascuthalfoftheworkpiecelengthl1.5mmfortimet310−4s,forvc300m/minrespectively,areshown.Inthisfigure,thecontinuousmeshingandtheadaptiveremeshingprocedurescanbeobserved.Note,that,inFig.2athemeshisdensernearthetooltip,wheredeformationisabouttotakeplace,whileinFig.2bnewelementsarecreatedintheshearzonewherethestrainrateisexpectedtobehigh.Note,also,thatthemeshdensityinthechip,especiallyinitsinnerandoutersurfaces,isalsohighbecauseofthedeformationofthematerialinthisareafinermeshcanfollowthecurveofthecurlingmaterialmorecloselyand,furthermore,providemoreaccurateresults.Forthevalidationoftheproposedhardturningmodelexperimentalresultsfromtherelevantliteratureareused,wherethehighspeedturningofhardsteeltubes55HRC,inordertoachieveorthogonalcuttingconditions,isperformed17.InFig.3theexperimentalvaluesofthethrustforceFtandthecuttingforceFcarecomparedtotheonespredictedfromthemodels.Fromthisfigureitcanbeseenthattheexperimentalandthenumericalresultsareinaverygoodagreementand,generally,theyfollowthesametrendsthrustforce,whichisthelargestforcecomponent,decreasesforincreasingcuttingspeed,whilecuttingforceincreasesslightly.Nevertheless,inalmostallthecases,theFig.2aInitialmeshandbmeshatl1.5mmFig.3NumericalandexperimentalresultsofthrustandcuttingforcesforthreedifferentcuttingspeedsIntJAdvManufTechnol200838441–446443numericalvaluesseemtooverestimatetheexperimentaloneswhilethediscrepanciesarelargerforhighercuttingspeedsthismaybeattributedtothelargestrainratesdevelopedduringtheprocessthataltersthematerialbehaviourinsuchawaythattheycannotbetakenintoaccountbythemodelortoinadequatefrictionmodelling,whichmeansthatamoreadvancedfrictiontheoryneedstobemodelled.Note,also,thatitispossible,besidesthecuttingandthrustforces,toextractfromtheproposedmodelpredictionsforvaluesthatitwouldbeverylaboriousorevenimpossibletoobtainotherwise.ExamplesofsuchcasesarethetemperaturedistributionintheworkpieceandtoolintheformofisothermalbandsandthevonMisesstressesdevelopedduringcutting.InFig.4aandbthetemperaturefieldsandthevonMisesstresses,respectively,forcuttingwithvc300m/min,areshown.Thesefiguresdemonstratethemodelatastepoftheanalysis,specificallyforlengthofcutl1.5mm,wherecuttingiswellintothesteadystateregion.Theformoftheresultsissimilarforallconditions,exceptofcoursethemagnitude.Fromtheresultsobtained,itmaybeconcludedthatthemaximumtemperatureincreaseswithincreasingcuttingspeed,being620°C,690°Cand730°Cforthethreedifferentcuttingspeedsconsidered.Thismayexplainthatthethrustforcedecreasesforhighercuttingspeed,sincesofteningofthematerialforhighertemperaturetakesplace.Theregionsthataremostlythermallyloadedarethechipandtherakefaceofthetool,inthechiptoolinterfaceclosetotooltip,duetotheplasticdeformationofthechipandthefrictionalforcesthepartofthechipthatiscurledawayfromtherakefaceisprogressivelycooleddown.Thestresshasanalmostconstantvaluealongthecentreoftheshearzone,whilenearthetooltipithaslowervaluesthiscanbeexplainedduetothetemperatureriseofthisareawhichsoftensthematerial.TheknowledgeofthemaximumtemperatureandofthedistributionofthetemperaturefieldsintherakefaceofthetoolisofgreatinterestbecausehightemperaturesinCBNtoolsareconnectedtowearmechanismsthatreducethetoollife.Withthenumericalresultsprovidedbythemodelitispossibletominimizeunwantedeffectsandtochoosesuitablecuttingconditionsinordertooptimizetheprocess.Anotheroptionoftheproposedorthogonalcuttingmodelistosimulatetheburrformationdevelopedwhenthecuttingtoolexertsthefulllengthoftheworkpiecethiscanbeachievedwhentheanalysisisappropriatelyextended,sothatthecuttingpathofthetoolislongerthanFig.4aTemperaturedistributionandbvonMisesstressesintheworkpiece,thechipandthecuttingtoolFig.5Burrformationandplasticstrainoftheworkpieceandthechip444IntJAdvManufTechnol200838441–446

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