外文翻译三维注射成型流动模拟的研究.docx

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