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

The modelcontainsaVisco-elasticfrequency-dependentmaterial.

Pre-Requisites:

SoftwareConfigurationsthatareneededtorunthetutorial:

∙LicensestosetupthecaseinLMSVirtual.Lab:

"Desktop（VL-HEV.21.1orequivalent）"and"FiniteElementAcoustics（VL-"

∙Whensolvingtheacousticresponsecase,thelicenseforproduct"LMSVirtual.LabFEMVibro-AcousticsStructuralSolverVL-VAM.45.2"isneeded.

∙SolvingtheRandomPost-processingcasetogettheTransmissionLosscurvewillrequirethelicensefor"RandomVibroAcousticAnalysis（VL-"

TutorialDataFiles:

StructuralGroups.xml

SAFyoung.xls

LaminatedStructure.bdf

FPmesh.bdf

AMLsender.bdf

AMLreceiver.bdf

AcousticGroups.xml

[AlldatafilescanbefoundontheAPPSnDOCSDVD,inanarchivecalled VAM_DirectVA-TL.Foreaseofuse,itisbesttocopyallfilestoalocalfolder.]

STEPBYSTEPTutorial:

STEP1

AfterstartingLMSVirtual.Lab,createanewdocumentintheAcousticHarmonicFEMWorkbench（Start

Acoustics

AcousticHarmonicFEM）.

STEP2

SelectFile

Importfromthemainmenu.[TheImportcommandcanalsobeselectedfromthecontextualmenuoftheLinksManager,byrightclicking]

Afileselectorwindowappearsallowingyoutospecifythefiletypeandthefilename.[Formoredetails,seeImportingData]

SelectthefiletypeNASTRANBulkFile（*.bdf,*.NS,*.nas,*.dat）andbrowseforthefileLaminatedStructure.bdfandclicktheOpenbutton.Anewdialogboxappearsrequestingtheselectionofdatathatneedstobeimportedfromthefile.Thedataentriesthatarenotavailableinthefilearegrayedout.

SelectinSplitintoMultipleMeshPartsunderMeshCreationandsettheunitsystemtoMeter,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

MassDensity

YoungModulus

PoissonRatio

MassDensity

Real

Imaginary

0.23

2500kg_m3

FrequencyDependent

0.49

1066kg_m3

7.15e+011N_m2

1.401e+009N_m2

ThePVBmaterialatthecenterofthewindshieldhasstrongfrequencydependentstiffnesspropertiesandisnearlyincompressible.Thefrequencydependencycanbeincorporatedinaviscoelasticmaterialusinganeditedloadfunction.ThevaluescanbeimportedfromtheExceldocumentSAFyoung.xlsasfollows:

CheckFrequencyDependent,andright-clicktheinputfield.

SelectNewFunction.

IntheAttributestab,enterasNameYoung’smodulusPVB.

IntheValuestab,clicktheImportafilebutton,andbrowsetotheexcelfiletoselectit.

SwitchtheDataFormattoLinearAmplitude/Phase（deg）becausethefilecontainsthevalueslikethat.ClicktheImportbutton.

ClicktheOKbuttonoftheFunctionEditorGUI.

ClicktheOKbuttonontheMaterialGUI.

OntheEditedLoadFunctionSet,create（usingthecontextmenu）a2DdisplayoftypeComplex（EditedLoadFunction）ontheYoung’smodulusandcheckthecurve:

STEP4

DefiningtwoStructural3DpropertiesforGlassandPVB,appliedtothestructuralgroupsGlass（withthedefinedmaterialGlass）andPVB（withthedefinedmaterialPVB）.

Insert

Properties

NewStructuralProperties

Create3D-Property

[Right-clickonthePropertiesfeatureintheSpecificationTree

NewStructuralProperties

Create3D-Property]

BeforethefollowingstepspleasemakesuretheMeshPartsaredefinedastypes:

PROPERTY0–Structural

Glass–Structural

PVB–Structural

ThiscanbedonebygoingtoTools

SetMeshPartsType

[Right-clickonthemeshintheSpecificationTree,SetMeshPartType

SetasStructuralMeshPart]

STEP5

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

File

ImportAcousticMesh

ModelMesh...,andselectthefileAMLreceiver.bdf

UseMeter,KilogramandSecondsunits,andincludethematerialsandproperties.

Similarly,importAMLsender.bdf.

Atthispointthemeshpartstypedefinitionwindowshouldlooklikethis:

STEP6

InsertingtheNewMaterialandpropertiesforthenewimportedmeshes

InsertanewAcousticmaterialasfollows（usethedefaultvaluesforair）:

InsertalsoaNewFluidProperty.Callitalsoair,usethejustdefined material'Air',andapplyittothetwoAcousticmeshparts（SenderandReceiverside）.

STEP7

Tofacilitatethecreationofthestructuralandacousticmodel,someelementgroupshavebeenpredefinedinxmlfiles.Toimportthesegroups,firstcreatemeshgroupsets.

InsertaNewGroupSet,eitherfromthecontextualmenuorwith Insert

MeshGrouping

GroupSet....

ByrightclickingtheGroupSetfeatureintheSpecificationTree,insertameshgroupnamedStructuralGroups,andinitimportthe5groupsfromthefileStructuralGroups.xml.

Right-clicktheGroupSet,anduseMeshGrouping

GroupSelectionDialog…:

SimilarlyinsertameshgroupnamedAcousticGroups,andinitimportthe4groupsfromthefileAcousticGroups.xml

Right-clickthegroupset,anduseagain MeshGrouping

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...withaRefinementLevelof2,aRadiusof4m,andanAcousticPressureon1Pa.Theplanewaveswillbeusedtoexcitethesystemandtocalculatethetransmissionlosscharacteristicsofthepanel.

Sincethepanelisnotalignedwiththexyplane,thiscoordinateplanecannotbeusedtodefinethelocationoftheplanewavesources.So,fortheHalfSpacePlaneselectPlanedefinedbyGroupandselecttheacousticgroupCouplingSender.

SelecttheNegativeHalfSpaceside.

ClicktheOKbuttontogenerateasetof12spatiallydistributedplanewaves.

Bynowthemodelshouldlooksimilartothis:

Step4

Wewillnowrestraintheborderoftheglasspanel.

Right-clicktheRestraintSet,addanAdvancedRestraintonthe3TranslationalDOFs,anduseassupporttheStructuralGroupBCs.

Step5

Couplingsurfacedefinitionwillbeusedtocoupletheupperandlowersurfacesofthepaneltotheenvelopesurfaceoftheacousticcavity.WhensettingtheCouplingSurface,thecouplingbetweenthestructureandthefluidisonbothsides.

Tocorrectlydefinethetwo-sidedcouplinginatransmissionlosscalculation,twocouplingsurfacesneedtobecreated.FromtheCouplingSurfaceSet.1feature,double-clicktheCouplingSurfaceSet.1,andaddthetwo surfaces:

StructuralGroupCouplingSenderandAcousticGroupCouplingSender.Useatoleranceof10mmandselectasCouplingTypeOneside.ClicktheApplybutton.

DothesamefortheReceiverSideintheendyoushouldhavetwoCouplingsurfaces:

Step6

Double-clickontheDirectVibro-AcousticResponsesolutiontoupdatetheanalysisparameters.Inthecurrenttutorial,theresponseatthecenterfrequenciesofthethirdoctavebandsbetween160Hzand2000Hzwillbeanalyzed.IntheResultSpecificationstab,selectUserDefinedvaluesfortheArgumentAxisDefinitionandremovethestandardanalysisfrequencyrange.AddanewfrequencyrangedefinitionandselectaLogarithmicStepdefinitionwithastartingfrequencyof160Hz,anendingfrequencyof2000Hzandastepof1.8.ClicktheOKbuttontoaddthefrequencyrangedefinition.

RequestVectorresultsatFieldPointsandfortheAcousticPotentials.NoneedtosolveforStructuralDisplacementsfornow.

AdjusttheSolvingParameters.Ifyoursystemissetupforparallelprocessing（seetheAdvancedAcousticInstallationmanual）,tryoneoftheParallelismtypes.UsetheDirectsolver.

AdjustalsotheJobandResources,e.g.tousemultiplethreads.

LeavetheOutputSetsempty,meaningthatresultswillbecomputedwhereverpossible.

Step7

UpdatetheDirectVibro-AcousticResponseSolutiontocomputetheacousticpressurefieldsandstructuraldeformations.Thiswilltakeawhile,asthereare23frequenciesand12loadconditions.Saveyourmodel.

Step8

Displaying