外文翻译三维注射成型流动模拟的研究.docx
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外文翻译三维注射成型流动模拟的研究.docx
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外文翻译三维注射成型流动模拟的研究
中文2900字
附录
NumericalFillingSimulationofInjectionMolding
UsingThree—DimensionalModel
Abstract:
Mostinjectionmoldedpartsarethree-dimensional,withcomplexgeometricalconfigurationsandthick/thinwallsections.A3Dsimulationmodelwillpredictmoreaccuratelythefillingprocessthana2.5Dmode1.Thispapergivesamathematicalmodelandnumericmethodbasedon3Dmodel,inwhichanequal-ordervelocity-pressureinterpolationmethodisemployedsuccessfully.Therelationbetweenvelocityandpressureisobtainedfromthediscretizedmomentumequationsinordertoderivethepressureequation.A3Dcontrolvolumeschemeisemployedtotracktheflowfront.Thevalidityofthemodelhasbeentestedthroughtheananalysisoftheflowincavity.
Keywords:
threedimension;equal-orderinterpolation;simulation;injectionmolding
1Introduction
Duringinjectionmolding,thetheologicalresponseofpolymermeltsisgenerallynon-Newtonianandnoisothermalwiththepositionofthemovingflowfront.Becauseoftheseinherentfactors,itisdifficulttoanalyzethefillingprocess.Therefore,simplificationsusuallyareused.Forexample,inmiddle-planetechniqueanddualdomaintechnique[1],becausethemostinjectionmoldedpartshavethecharacteristicofbeingthinbutgenerallyofcomplexshape,theHele-Shawapproximation[2]isusedwhileananalyzingtheflow,i.e..Thevariationsofvelocityandpressureinthegapwise(thickness)dimensionareneglected.Sothesetwotechniquesareboth2.5Dmoldfillingmodels,inwhichthefillingofamoldcavitybecomesa2Dprobleminflowdirectionanda1Dprobleminthicknessdirection.
However,becauseoftheuseoftheHele-Shawapproximation,theinformationthat2.5Dmodelscangenerateislimitedandincomplete.Thevariationinthegapwise(thickness)dimensionofthephysicalquantitieswiththeexceptionofthetemperature,whichissolvedbyfinitedifferencemethod,isneglected.Withthedevelopmentofmoldingtechniques,moldedpartswillhavemoreandmorecomplexgeometryandthedifferenceinthethicknesswillbemoreandmorenotable,sothechangeinthegapwise(thickness)dimensionofthephysicalquantitiescannotbeneglected.Inaddition,theflowsimulatedlooksunrealisticinasmuchasthemeltpolymerflowsonlyonsurfacesofcavity,whichappearsmoreobviouswhentheflowsimulationisdisplayedinamouldcavity.
3Dsimulationmodelhasbeenaresearchdirectionandhotspotinthescopeofsimulationforplasticinjectionmolding.In3Dsimulationmodel,velocityinthegapwise(thickness)dimensionisnotneglectedandthepressurevariesinthedirectionofpartthickness,and3Dfiniteelementsareusedtodiscretizethepartgeometry.Aftercalculating,completedataareobtained(notonlysurfacedatabutalsointernaldataareobtained).Therefore,a3Dsimulationmodelshouldbeabletogeneratecomplementaryandmoredetailedinformationrelatedtotheflowcharacteristicsandstressdistributionsinthinmoldedpartsthantheoneobtainedwhenusinga2.5Dmodel(basedontheHele-Shawapproximation).Ontheotherhand,a3Dmodelwillpredictmoreaccuratelythecharacteristicsofmoldedpartshavingthickwalledsectionssuchasencounteredingasassistedinjectionmolding.Severalflowbehaviorsattheflowfront.suchas“fountainflow”.which2.5Dmodelcannotpredict,canbepredictedby3Dmode1.Meanwhile,theflowsimulationlooksmorerealisticinasmuchastheoverallananalysisresultisdirectlydisplayedin3Dpartgeometryortransparentmouldcavity.
ThisPaperpresentsa3Dfiniteelementmodeltodealwiththethree—dimensionalflow,whichemploysanequa1-ordervelocity-pressureformulationmethod[3,4].Therelationbetweenvelocityandpressureisobtainedfromthediscretizedmomentumequations,thensubstitutedintothecontinuityequationtoderivepressureequation.A3Dcontrolvolumeschemeisemployedtotracktheflowfront.Thevalidityofthemodelhasbeentestedthroughtheanalysisoftheflowincavity.
2GoverningEquations
Thepressureofmeltisnotverybigduringfillingthecavity,inaddition,reasonablemoldstructurecanavoidoverbigpressure,sothemeltisconsideredincompressible.Inertiaandgravitationareneglectedascomparedtotheviscousforce.
Withtheaboveapproximation,thegoverningequations,expressedincartesiancoordinates,areasfollowing:
Momentumequations
Continuityequation
Energyequation
where,x,y,zarethreedimensionalcoordinatesandu,v,warethevelocitycomponentinthex,y,zdirections.P,T,ρandηdenotepressure,temperature,densityandviscostyrespectively.
Crossviscositymodelhasbeenusedforthesimulations:
where,n,γ,rarenon-Newtonianexponent,shearrateandmaterialconstantrespectively.Becausethereisnonotablechangeinthescopeoftemperatureofthemeltpolymerduringfilling,Anheniusmodel[5]forη
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- 外文 翻译 三维 注射 成型 流动 模拟 研究