Virtuallab声固耦合的隔声量仿真分析教程.docx

Virtuallab声固耦合的隔声量仿真分析教程.docx

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Virtuallab声固耦合的隔声量仿真分析教程

FEMDirectVibro-AcousticAnalysisCaseTutorial

Objective:

Thegoalofthistutorialistocalculatetheacousticresponseofaglass/PVBplate（alaminatedsafetyglasswithaPolyvinylbutyrallayerinbetween）・

Thetutorialincludesusingthefollowinganalysiscases:

•StructuralModalcase

•DirectStructuralForcedResponse

•DirectStructuralVibro-AcousticResponse

•TransmissionLoss

ThemodelcontainsaVisco-elasticfrequency-dependentmaterial・

Pre-Requisites:

SoftwareConfigurationsthatareneededtorunthetutorial:

•LicensestosetupthecaseinLMSVirtual.Lab:

uDesktop（VL-HEV.21.1orequivalent）1'and"FiniteElementAcoustics（VL-"

•Whensolvingtheacousticresponsecase,thelicenseforproductULMSVirtual.LabFEMVibro-AcousticsStructuralSolverVL-VAM.45.2”isneeded・

•SolvingtheRandomPost-processingcasetogettheT「ansmissionLosscurvewillrequirethelicensefornRandomVibroAcousticAnalysis（VL-n

TutorialDataFiles:

StructuralGroups・xml

SAFyoung・xls

LaminatedStructure・bdf

FPmesh・bdf

AMLsender・bdf

AMLreceiver・bdf

AcousticGroups・xml

[AlldatafilescanbefoundontheAPPSnDOCSDVD,inanarchivecalledVAM_DirectVA-TL.Foreaseofuse,itisbesttocopyallfilestoalocalfolder.]

STEPBYSTEPTutorial:

STEP1

AfterstartingLMSVirtual.Lab,createanewdocumentintheAcousticHarmonicFEM

Workbench（Start-^Acoustics-^AcousticHarmonicFEM）.

STEP2

SelectFile-^Importfromthemainmenu・[TheImportcommandcanalsobeselectedfromthecontextualmenuoftheLinksManager,byrightclicking]

Afileselectorwindowappearsallowingyoutospecifythefiletypeandthefilename・[Formoredetails,see]

SelectthefiletypeNASTRANBulkFile（匸bdf,*・NS#^.nasf\dat）andbrowseforthefileLaminatedstructure・bdfandclicktheOpenbutton.Anewdialogboxappearsrequestingtheselectionofdatathatneedstobeimportedfromthefile.Thedataentriesthatarenotavailableinthefilearegrayedout.

SelectinSplitintoMultipleMeshPa「tsunderMeshCreationandsettheunitsystemtoMeter,Kilogram,Second,clicktheOKbuttOn.

STEP3

Next,thedifferentstructuralmaterialswillbedefined・ThetwoouterlayersofthepanelaremadeofGlass・Toincorporatethe2%structuraldampingofthismaterial,itwillbemodeledasaviscoelasticmaterialwithaconstantcomplexYoungmodulus・TheinnerlayerismadeofPVB.

Insert-^Materials-^NewMaterials-^NewViscoelasticMaterial...

[Right-clickontheMaterialsfeatureintheSpecificationTree-^NewMaterials-^NewViscoelasticMaterial]

Definethematerialsasfollows:

GLASS

PVB

YoungModulus

Constant

PoissonRatio

Mass

Density

YoungModulus

Poisson

Ratio

MassDensity

Real

Imaginary

0・23

2500

kg_m3

Frequency

Dependent

0・49

1066kg_m3

7・15e+011

N_m2

:

L・401e+009

N_m2

ThePVBmaterialatthecenterofthewindshieldhasstrongfrequencydependentstiffnesspropertiesandisnearlyincompressible・Thefrequencydependencycanbeincorporatedinaviscoelasticmaterialusinganeditedloadfunction.ThevaluescanbeimportedfromtheExceldocumentSAFyoung.xlsasfollows:

CheckFrequencyDependent,andright-clicktheinputfield・

SelectNewFunction・

IntheAttributestab,enterasNameYoung"smoduluspvb・

IntheValuestab,clicktheImportafilebutton,andbrowsetotheexcelfiletoselectit.

SwitchtheDataFormattoLinearAmpHtude/Phase（deg）becausethefilecontainsthevalueslikethat.ClicktheImportbutton.

ClicktheOKbuttonoftheFunctionEditorGUL

ClicktheOKbuttonontheMaterialGUL

OntheEditedLoadFunctionSet,create（usingthecontextmenu）a2Ddisplay&typeComp/ex（EditedLoadFunction）ontheYoung'smodulusandcheckthecurve:

STEP4

DefiningtwoStructural3DpropertiesforGlassandPVB,appliedtothestructuralgroupsGlass（withthedefinedmaterialGlass）andPVB（withthedefinedmaterialPVB）.

Insert-^Properties-^NewStructuralProperties-^Create3D-Property

[Right-clickonthePropertiesfeatureintheSpecificationTree-^-NewStructuralProperties-^•Create3D-Property]

BeforethefollowingstepspleasemakesuretheMeshPartsaredefinedastypes:

PROPERTY0一Structural

Glass一Structural

PVB一Structural

ThiscanbedonebygoingtoTools-^SetMeshPartsType

[Right-clickonthemeshintheSpecificationTree,SetMeshPartType-^SetasStructuralMeshPart]

STEP5

Inthenextstep,themodelmeshwillbeimportedfromtwoNastraninputfiles・TheyeachcontainameshonwhichwewillapplyanAMLproperty（AutomaticallyMatchedLayer）,oneonthereceiverside,andoneonthesenderside.:

File-^ImportAcousticMesh-^ModelMesh...,andselectthefileAMLreceiver.bdf

UseMeter,KilogramandSecondsunits,andineludethematerialsandproperties・

Similarly,importAMLsender・bdf・

Atthispointthemeshpartstypedefinitionwindowshouldlooklikethis:

STEP6

InsertingtheNewMaterialandpropertiesforthenewimportedmeshes

InsertanewAcousticmaterialasfollows（usethedefaultvaluesforair）:

InsertalsoaNewFluidProperty.Callitalsoair,usethejustdefinedmaterial'Air',andapplyittothetwoAcousticmeshparts（SenderandReceiverside）.

STEP7

Tofacilitatethecreationofthestructuralandacousticmodel,someelementgroupshavebeenpredefinedinxmlfiles・Toimportthesegroups,firstcreatemeshgroupsets・

InsertaNewGroupSet,eitherfromthecontextualmenuorwithInsert-^MeshGrouping-^•GroupSet....

ByrightclickingtheGroupSetfeatureintheSpecificationTree,insertameshgroupnamedStructuralGroups,andinitimportthe5groupsfromthefilestructuralGroups・xml・

Right-clicktheGroupSet,anduseMeshGrouping-^GroupSelectionDialog...:

SimilarlyinsertameshgroupnamedAcousticGroups,andinitimportthe4groupsfromthefileAcousticGroups・xml

Right-clickthegroupset,anduseagainMeshGrouping->GroupSelectionDialog...:

Step8

Savetheanalysis,butwithoutclosing.

SETTINGUPTHEACOUSTICCASES

Step1

Insertanewacousticautomaticallymatchedlayerpropertytotakeintoaccountthesemi-infiniteextentofthesenderandreceiverrooms・InsertanewAMLpropertybyright-clickingProperties,useNewAcousticProperties-^AutomaticallyMatchedLayerProperty....

ApplyittothetwoAcousticgroupsAMLReceiverandAMLSender.SwitchtheRadiationsurfacetoUserDefined,andselecttheamlReceivergroup・

Step2

InsertaDirectVibro・AcousticResponseAnalysisCasetocomputethestructuralresponseandacousticpressurefieldsinboththesenderandreceiveracousticdomainsforeachofthedistributedplanewaveexcitations:

ToperformthiscalculationuseNoLoadfunctionSetandNoLoadVectorSet.

Createnewsetsforalltherest.

STEP3

ExpandtheDirectVibro・AcousticResponseAnalysisCasefromtheSpecificationTree,right-clicktheBoundaryConditionSetanduseAcousticSources-^DistributedPlaneWaves...withaRefinementLeveled2,aRadius&4m,andanAcousticPressureonlPa.Theplanewaveswillbeusedtoexcitethesystemandtocalculatethetransmissionlosscharacteristicsofthepanel.

Sincethepanelisnotalignedwiththexyplane,thiscoordinateplanecannotbeusedtodefinethelocationoftheplanewavesources・So,fortheHalfSpacePlaneselectPlanedefinedbyGroupsndselecttheacousticgroupcouplingsender・

SelecttheNegativeHalfSpaceside.

ClicktheOKbuttontogenerateasetof12spatiallydistributedplanewaves・

Bynowthemodelshouldlooksimilartothis:

Step4

Wewillnowrestraintheborderoftheglasspanel.

Right-clicktheRestraintSet,addanAdvancedRestraintqv\the3TranslationalDOFs,anduseassupporttheStructuralGroupBCs.

Step5

Couplingsurfacedefinitionwillbeusedtocoupletheupperandlowersurfacesofthepaneltotheenvelopesurfaceoftheacousticcavity・WhensettingtheCouplingSurface,thecouplingbetweenthestructureandthefluidisonbothsides.

Tocorrectlydefinethetwo-sidedcouplinginatransmissionlosscalculation,twocouplingsurfacesneedtobecreated・FromtheCouplingSurfaceSet.1feature,double-clicktheCouplingSurfaceSet.1,andaddthetwosurfaces:

StructuralGroupCouplingSenderandAcousticGroupCouplingSender.Useatoleraneeof10mmandselectasCouplingTypeOneside.ClicktheApplybutton.

DothesamefortheReceiverSideintheendyoushouldhavetwoCouplingsurfaces:

Step6

Double-clickontheDirectVibro-AcousticResponsesolutiontoupdatetheanalysisparameters.Inthecurrenttutorial,theresponseatthecenterfrequenciesofthethirdoctavebandsbetween160Hzand2000Hzwillbeanalyzed・IntheResultSpecificationstab,selectUserDefinedfortheArgumentAxisDefinitionandremovethestandardanalysisfrequencyrange・Addanewfrequency「angedefinitionandselectaLogarithmicStepdefinitionwithastartingfrequencyof160Hz,anendingfrequencyof2000Hzandastepof1・8.ClicktheOKbuttontoaddthefrequency「angedefinition.

RequestlectorresultsatFieldPointsandfortheAcousticPotentials.NoneedtosolveforStructuralDisplacementsfornow・

AdjusttheSolvingParameters・Ifyoursystemissetupforparallelprocessing（seetheAdvaneedAcousticInstallationmanual）,tryoneoftheParallelismtypes・UsetheDirectsolver.

AdjustalsotheJobandResources,e.g.tousemultiplethreads・

LeavetheOutputSetsempty,meaningthatresultswillbecomputedwhereverpossible.

Step7

UpdatetheDirectVibro-AcousticResponseSolutiontocomputetheacousticpressurefieldsandstructuraldeformations.Thiswilltakeawhile,asthereare23frequenciesand12loadconditions.Saveyourmodel.

Step