Virtual.lab声固耦合的隔声量仿真分析教程

1、 FEMDirectVibro-AcousticAnalysisCaseTutorialObjective:Thegoalofthistutorialistocalculatetheacousticresponseofaglass/PVBplate(alaminatedsafetyglasswithaPolyvinylbutyrallayerinbetween).Thetutorialincludesusingthefollowinganalysiscases:StructuralModalcaseDirectStructuralForcedResponseDirectStructuralVi

2、bro-AcousticResponseTransmissionLossThemodelcontainsaVisco-elasticfrequency-dependentmaterial.Pre-Requisites:SoftwareConfigurationsthatareneededtorunthetutorial:LicensestosetupthecaseinLMSVirtual.Lab:Desktop(VL-HEV.21.1orequivalent)andFiniteElementAcoustics(VL-VAM.36.2)Whensolvingtheacousticresponse

3、case,thelicenseforproductLMSVirtual.LabFEMVibro-AcousticsStructuralSolverVL-VAM.45.2isneeded.SolvingtheRandomPost-processingcasetogettheTransmissionLosscurvewillrequirethelicenseforRandomVibroAcousticAnalysis(VL-NVP.20.3)TutorialDataFiles:StructuralGroups.xmlSAFyoung.xlsLaminatedStructure.bdfFPmesh.

4、bdfAMLsender.bdfAMLreceiver.bdfAcousticGroups.xmlAlldatafilescanbefoundontheAPPSnDOCSDVD,inanarchivecalledVAM_DirectVA-TL.Foreaseofuse,itisbesttocopyallfilestoalocalfolder.STEPBYSTEPTutorial:STEP1AfterstartingLMSVirtual.Lab,createanewdocumentintheAcousticHarmonicFEMWorkbench(Start-AcousticsAcousticH

5、armonicFEM).STEP2SelectFile-Importfromthemainmenu.TheImportcommandcanalsobeselectedfromthecontextualmenuoftheLinksManager,byrightclickingAfileselectorwindowappearsallowingyoutospecifythefiletypeandthefilename.Formoredetails,seeImporting_DataSelectthefiletypeNASTRANBulkFile(*.bdf,*.NS,*.nas,*.data)nd

6、browseforthefileLaminatedStructure.bdfandclicktheOpenbutton.Anewdialogboxappearsrequestingtheselectionofdatathatneedstobeimportedfromthefile.Thedataentriesthatarenotavailableinthefilearegrayedout.SelectinSplitintoMultipleMeshPartsunderMeshCreationandsettheunitsystemtoMeter,Kilogram,Second,clicktheOK

7、button.ModeUnitSystem丄iD已riveUnitsoFFciitesFromUnitSystemLengthMassTimennple：TemperatureOKICancslScejricLjcldjLoddlisQSEiESSFiniteElementMeshLoddlMajSuKSBLoadsIirportFE/TestDataSetsLarrin-dtedStruLture-NcdesandElementsSpitintoMultipleMeshPartsAnalysisCaseImport丄PropertiesandMaterials沁h歸畔AcousticMesh

8、MeshCr&atlonLarrinatedStrucztLiFm-WireFramervleehLarriridtedEtruLture-AcousticMeshFopropertiesFileTypeNA5TR.AkTBijikTle(*.bdf,+.N5;+.nas/.dat)FileNamed：tempLaminated5tructure.bdfMeshModelImportIReimportFileChang已千KiloqramSecundRadian匚dsiusdegreeMeterSTEP3Next,thedifferentstructuralmaterialswillbedef

9、ined.ThetwoouterlayersofthepanelaremadeofGlass.Toincorporatethe2%structuraldampingofthismaterial,itwillbemodeledasaviscoelasticmaterialwithaconstantcomplexYoungmodulus.TheinnerlayerismadeofPVB.InsertMaterialsNewMaterialsNewViscoelasticMaterial.Right-clickontheMaterialsfeatureintheSpecificationTree-J

10、-NewMaterialsNewViscoelasticMaterialDefinethematerialsasfollows:GLASSPVBYoungModulusPoissonRatioMassYoungPoissonMassDensityConstantDensityModulusRatioRealImaginary0.232500Frequency0.491066kgm3kgm3Dependent7.15e+0111.401e+009Nm2Nm2ViscoelasticMaterrF|1=1|E|NameGlassMaterialID:KII讲Apply匚血也ThePVBmateri

11、alatthecenterofthewindshieldhasstrongfrequencydependentstiffnesspropertiesandisnearlyincompressible.Thefrequencydependencycanbeincorporatedinaviscoelasticmaterialusinganeditedloadfunction.ThevaluescanbeimportedfromtheExceldocumentSAFyoung.xlsasfollows:CheckFrequencyDependen,tandright-clicktheinputfi

12、eld.SelectNewFunction.Vi5coelasticMarteriaIPVBMaterialID:YoungModiulus:RealO匚onstant0Nm2QImaginary0N_m2dFrequencyDependentPoissonR.atio:*NewFunction疼1ModifyFunction电ConstantRealRemoveFun匚tianOFrequencyDependentXQeleteFunction-MassDensity:11066kgm3QKII人叩“Gri胡IntheAttributestab,enterasNameYoungsmodulu

13、sPVB.IntheValuestab,clicktheImportafilebutton,andbrowsetotheexcelfiletoselectit.3I畅piinJpgAttributesJIni吋说FuhI血IReHWni2AllCommands0N/m2Enterl?eletESelectAllInvEftSElEction匚前1LoadFunctionEditnrLd轨21U74?21142kltfLEl|(lN/m2DispkyValueas|加LOaginaryValues：OvEr.ieuMMesges|Recorder|StackLeviel;皿匚QuOUDLASwi

14、tchtheDataFormattoLinearAmplitude/Phase(deg)becausethefilecontainsthevalueslikethat.ClicktheImportbutton.ClicktheOKbuttonoftheFunctionEditorGUI.ClicktheOKbuttonontheMaterialGUI.OntheEditedLoadFunctionSet,create(usingthecontextmenu)a2DdisplayoftypeComplex(EditedLoadFunction)ontheYoungsmodulusandcheck

15、thecurve:I.TS-l-i卸+1531ia+鲫FttMejtk-1FirmSwitksiPh/S31WExQLdknID1DjIiDj!|HFWOrefa-r血ni:右rJM-naUnihilPVSLbMJFUMvIiW31JNaUDDJLJLIBL&kTk*H怔alD.T.1GkLdSTEP4DefiningtwoStructural3DpropertiesforGlassandPVB,appliedtothestructuralgroupsGlass(withthedefinedmaterialGlass)andPVB(withthedefinedmaterialPVB).Inse

16、rtPropertiesNewStructuralPropertiesCreate3D-PropertyRight-clickonthePropertiesfeatureintheSpecificationTree-?1NewStructuralProperties-Create3D-PropertyPrapertyDefinitionProp亡rtyDeFinrtionTypeSelectionType:|SolidPropertyTGlassEditMaterialGlassQD:3NameGlassApplicationRegion!ParametersPropertyd(Automat

17、ic琢i|庁|b|ApplitationRegion:TypeSelectioHType:|SolidPropertyMoreParametErsIjAdvancedPsrameterEditingStatus-InformationFeaturerequiresupdateMaterial卩如邑4)ParametersPrapErtyld|AutomaticBeforethefollowingstepspleasemakesuretheMeshPartsaredefinedastypes:PROPERTY。-StrueturalGlass-StrueturalPVB-StrueturalTh

18、iscanbedonebygoingtoTools-SetMeshPartsTypeRight-clickonthemeshintheSpecificationTree,SetMeshPartType-SetasStructuralMeshPartSTEP5Inthenextstep,themodelmeshwillbeimportedfromtwoNastraninputfiles.TheyeachcontainameshonwhichwewillapplyanAMLproperty(AutomaticallyMatchedLayer),oneonthereceiverside,andone

19、onthesenderside.: FileImportAcousticMeshModelMesh.,andselectthefileAMLreceiver.bdfUseMeter,KilogramandSecondsunits,andincludethematerialsandproperties.Similarly,importAMLsender.bdf.Atthispointthemeshpartstypedefinitionwindowshouldlooklikethis:STEP6InsertingtheNewMaterialandpropertiesforthenewimporte

20、dmeshesInsertanewAcousticmaterialasfollows(usethedefaultvaluesforair): InsertalsoaNewFluidProperty.Callitalsoair,usethejustdefinedmaterialAir,andapplyittothetwoAcousticmeshparts(SenderandReceiverside).ShowMoreParametersOKApplyC日nt白STEP7Tofacilitatethecreationofthestructuralandacousticmodel,someeleme

21、ntgroupshavebeenpredefinedinxmlfiles.Toimportthesegroups,firstcreatemeshgroupsets.InsertaNewGroupSet,eitherfromthecontextualmenuorwithInsert-J-MeshGroupingTGroupSetByrightclickingtheGroupSetfeatureintheSpecificationTree,insertameshgroupnamedStructuralGroups,andinitimportthe5groupsfromthefileStructur

22、alGroups.xml.Right-clicktheGroupSet,anduseMeshGrouping-GroupSelectionDialog:SimilarlyinsertameshgroupnamedAcousticGroups,andinitimportthe4groupsfromthefileAcousticGroups.xmlRight-clickthegroupset,anduseagainMeshGrouping-GroupSelectionDialog:Step8Savetheanalysis,butwithoutclosing.SETTINGUPTHEACOUSTIC

23、CASESStep1Insertanewacousticautomaticallymatchedlayerpropertytotakeintoaccountthesemi-infiniteextentofthesenderandreceiverrooms.InsertanewAMLpropertybyright-clickingProperties,useNewAcousticProperties-AutomaticallyMatchedLayerPropertyApplyittothetwoAcousticgroupsAMLReceiverandAMLSender.SwitchtheRadi

24、ationsurfacetoUserDefined,andselecttheAMLReceivergroup.UserDefinedEditnAMLReceiverAutomaticallyMatchedLayerPropertyName|AutomaticallyMatchedLayerProperty.1ApplicationRegion2GroupsRadiationsurfaceforfar-fieldcalculationShowMoreParameters.Radiationsurface毬ApplyCancelStep2InsertaDirectVibro-AcousticRes

25、ponseAnalysisCasetocomputethestructuralresponseandacousticpressurefieldsinboththesenderandreceiveracousticdomainsforeachofthedistributedplanewaveexcitations:ToperformthiscalculationuseNoLoadfunctionSetandNoLoadVectorSe.tCreatenewsetsforalltherest.STEP3ExpandtheDirectVibro-AcousticResponseAnalysisCas

26、efromtheSpecificationTree,right-clicktheBoundaryConditionSetanduseAcousticSources-DistributedPlaneWaves.withaRefinementLevelof2,aRadiusof4m,andanAcousticPressureon1Pa.Theplanewaveswillbeusedtoexcitethesystemandtocalculatethetransmissionlosscharacteristicsofthepanel.Sincethepanelisnotalignedwiththexy

27、plane,thiscoordinateplanecannotbeusedtodefinethelocationoftheplanewavesources.So,fortheHalfSpacePlaneselectPlanedefinedbyGroupandselecttheacousticgroupCouplingSender.SelecttheNegativeHalfSpaceside.厂一CreateDistrlbiitedAcousiticPlaneV/avesa図HammDistributedAcousticPlaneWareParameters-Planedefined3Group

28、匚owingSenderHalfSpace5ideQPoatrve*PJegatrveOFulOKCancelClicktheOKbuttontogenerateasetof12spatiallydistributedplanewaves.Bynowthemodelshouldlooksimilartothis:elkd上d血iflflfOUSh丫圧呻卫住刘Mil-lZl8ft：r：=L：i_,7i：q，；：口二人3、；：；：F仏LUIn-LJ.C.JlvCri.ill.fcrd-4”ErHr)；Gwpfn】SurfpESll才口曲:lWtr:-：i-st(Raspo1:MjIsca.I.淞匹

29、命&監鱼盂田0_SL画国.宣矣-醴*C加3-1：zlfirrcrtF臂密血1V|M:!1i.注11上亠UM匸|jJ：mi_衫Lai*tvJtseRdt匕电勺-1rMr:envi-tdd-理.rksF/wascr.L # Step4Wewillnowrestraintheborderoftheglasspanel.Right-clicktheRestraintSet,addanAdvancedRestraintonthe3TranslationalDOFs,anduseassupporttheStructuralGroupBC.sAdvFressixe(rod渤wines)O.4G20.3S0.

30、3W0.16O.O9L0CI.017B-0.201CmBFn?QuencyDCasePressureinodalvaluer).1507.95H2LoadCondiliont2Youcanalsodisplaythe2DimagecurvefortheAcousticPowerontheKirchhoffsurfaceRight-clicktheDirectVibro-AcousticResponseSolutionSet.1featureandselectNewFunctionDisplay.fromthecontextualmenu.TheNewFunctionDisplaydialogb

31、oxwillappearrequestingyoutoselectthedifferentdisplayimages.AlsoyoucanusetheLbuttonfromthetoolbarandselecttheSolutionSetfeature.AthirdpossibilityistousethemenuInsert-2D/3DImagesNewFunctionDisplaySelectthe2DDisplayfromthelistandclicktheFinishbutton.Anewwindow,containingX-andY-axesalongwiththeSelectDat

32、adialogboxwillnowappear.IntheSelectDatadialogbox,selectKirchhoffSurfaceRadiation:SandclicktheDisplaybuttonAseachofthedistributedplanewavesourcesareindependent,thesoundpowercanbeobtainedbysimplyaddingtheindividualcontributions.So,selectall12DataCases,andchecktheoptionSumoverdatacases.Switchthex-axisf

33、ormattoOctaves,andtheY-axistodB(RMS).Youcanusedotmarkersforthecurvebyright-clickingit,usingtheOmandinitscontextmenu,andthenchangingthesettingsintheVisualizationtab.SaveyourmodelStep9Togetthetransmissionlosscurve,weneedtodividethetotalacousticpoweronthereceiversidebythetotalpoweronthesenderside.Befor

34、ewecandothat,weneedtocombinetheindividualcases(oneforeachdistributedplanewavesource)togetthetotalpowercurves.InsertaRandomPost-processingCasewithInsert-potherAnalysisCasesRandomPost-ProcessingCase.Refertothesolutionofthepreviousresponsecase,andselecttoprocessforaCrossPowerSetwithUnitaryUncorrelatedL

35、oadCases:UpdateitssolutionusingthecontextmenuonitssolutionfeatureRandomResponseSolutionSet.X.Thiswillgofast.Right-clickthesub-solutionGlobalIndicatorSet.XandcreateaNewFunctionDisplayonit.Selectthe2DDisplayasscenario,andclicktheFinishbutton.A2DdisplaywindowwillappearwiththeSelectDatadialogboxopen.Int

36、heGeneraltab,switchthedrop-downselectortoTransmissionLoss,andselecttheentryCoupledSurface:SandclicktheDisplaybutton.YoucanseeaTLvalueof30.461911dBforthe319.996Hzoctaveband: 诉.CTJg加i：i|OT.4Gligi13阳.毋艮|PnpomriBf咛MflWFjnclonHHjRnprwA*otobdindAieriiTiLocil TheoryforPanelTransmissionLossCalculationofTran

37、smissionLossusingVibro-AcousticFEMThistopicdescribeshowtosetupamodelandthecomputationtocomputetheTransmissionLoss(e.g.forapanel)usingtheLMSVirtual.Labtools.Step1.ImportofanAcousticandStructuralmeshImport_an_acoustic_meshandastructuralmeshwiththemodaldataintheAcousticHarmonicFEMworkbench.Thereisnonee

38、dtohaveafieldpointmesh.Step2.CreateaNewAcousticPropertyDefinetheAcousticPropertiesincludingfluidpropertiesandpossibleimpedanceonthepanel.CreateanAutomatically_Matched丄ayer_(AML).propertyforthesourceroomonallfacesthatarenotcoupledtothepanelandnottouchingthejoinedwall.Thewallmustbeazerovelocityboundar

39、ycondition.AlsocreateanAutomaticallyMatchedLayer(AML)ontheanechoicroomside,whichisdefinedasaKirchhoffsurface.Step3.InserttheboundaryconditionCreateanacousticboundaryconditionbyselectingInsert-AcousticBoundaryConditionsandSourcesAcousticBoundaryConditionandSourceSetfromthemainmenu.TheBoundaryConditio

40、nSetCreationdialogboxappearsasshownintheimagebelow:BoundaryConditionSetCreation|?|XBoundaryCoriditiunSetEditionNameAcousticBoundaryConditionsandSourcesDataTypeFreqjencySpectra二|OK|匚ancelClicktheOKbuttontoclosethedialogbox.AnewAcousticBoundaryConditionsandSourcesfeatureappearsintheSpecificationTreeas

41、shownintheimagebelow:AcousticBoundaryConditionsandSourcesLodConditions # Now,similarlyaddtotheAcousticBoundaryConditionandSourcesanacousticsourceoftypeDistributed_Plane_Wavesinthesourceroom.Step4.InsertaVibro-AcousticResponseandRandomPost-ProcessingAnalysisCaseCaseInserttheModal-basedVibro-AcousticR

42、esponseAnalysisCasebyselectingInsertFEMAnalysisCasesModalBasedVibro-AcousticResponseAnalysisCasefromthemainmenu,orclicktheCreateaModalBasedVibro-AcousticResponseAnalysisuttonfromtheFEMAnalysisCasestoolbar.DefinetheMeshMappingandselectthestructuralshellsandthetwogroupsofacousticfaces(oneinthesourcero

43、omandoneinthereceiverroom).ComputetheModal-basedVibro-AcousticResponseAnalysiscase.ItwillcomputetheIncidentPowerandtheRadiatedPowerforeachsource.Similarly,insertaRandom_Post-Processing_Case,andComputeit.ItwillcomputetheTotalPowersandstoreitinasub-solutioncalledGlobalIndicatorSetas:TotalIncidentPowe,

44、rhavingPhysicalTypeasINPUT_POWERandResponseIDasCoupledSurface:S.TotalPowerradiatedbytheAcousticMesh,havingPhysicalTypeasACOUSTIC_POWERandResponseIDasKirchhoffSurfaceRadiation:.SIfyouhaveafieldpointmeshwhichisnotneededtocomputetheTransmissionLoss),itwillalsocomputetheTotalPowerontheFieldPointMeshhavi

45、ngPhysicalTypeasACOUSTIC_POWERandResponseIDasFieldPointMesh:S.TheRandomResponseSolutionSectomputesalsotheTransmissionLosswiththefollowingformula:TransmissionLossWhere,:istheIncidentPowerr:.:istheRadiatedPowerStep5:Post-ProcessingStandardresultswillbepost-processedontheanalysiscases.TheIncidentPower,

46、RadiatedPowearndTransmissionLossarestoredasExpressions,LoadFunctionsbytheGlobalIndicatorSet,andcanbedisplayedina2DFunctionDisplay.TheTransmissionLosswillbestoredwithPhysicalTypeasABSORPTIVITYandResponseIDasCoupledSurface:SManualcalculationofTransmissionLossbyusingEditedLoadFunctionStepl.InsertanEdit

47、ed丄oad_Function.ToinsertanEditedLoadFunction,selectfromthemainmenuInsert-FunctionsCreatorJbuttonavailable-EditedLoadFunctionorusetheCreateanEditedLoadFunctionintheFunctionsCreatortoolbar.Step2.ImportKirchhoffSurfaceRadiation:SfunctionfromGlobalIndicatorsoftheRandomPost-ProcessingSolutionSetoftheAcou

48、sticdocument.TakeonlytheRealPart.Step3.Again,importthefunctionAcousticPoweronFieldPointMesh:SfromGlobalIndicatorsoftheRandomPost-ProcessingSolutionSetoftheStructuraldocument.TakeonlytheRealPartandAmplitudeofthatPart.Step4.Multiplythisfunctionwith0.5.Astheactualincidentpowerishalfthepowerthroughthefi

49、eldpointmesh.Thisisbecausetheincidentpressureisimposedastotalpressureonthewall.Step5.Now,dividethesetwofunctionsandtaketheLogofthatfunctionandfinallymultiplyitwith10.Step6.Create_a_2D_displayTovisualizethecomputedTransmissionLoss,right-clicktheEditedloadfunctionintheSpecificationTreeandselecttheNewF

50、unctionDisplay.optionfromthecontextualmenu.Select2DDisplayfromthelistandclicktheFinishbutton.FromtheSelectDatadialogboxselectTransmissionLossusingthedrop-downmenu. BEMSymmetryPlaneSetThemathematicalformulationoftheBoundaryElementmethodleadstodensematrices,withtheconsequencethatalinearincreaseinmodel

51、sizeN(numberofnodesandelements,ormoregenerally,numberofDOFs)leadstoAparabolicincrease(orderN*2)fortheBEMmatrixstoragerequirementsAcubicincrease(orderN*3)fortheBEMmatrixsolutiontimeTherefore,itisveryadvantageoustoexploitsymmetrycharacteristicsinthegeometryofthesound-radiatingstructuretothefullextend.

52、Ifyouneedtomodelonlyone-half,one-quarterorone-eighthofavibratingstructure,thisleadstoadrasticreductioninmemoryrequirementsandsolutiontimefortheproblemathand.TheSymmetryPlaneSetcommandallowsyoutodefinetheacousticalsymmetryoranti-symmetryconditionswithrespecttoplanesthatareparalleltothecoordinateaxisp

53、lanes(XY,YZorXZ).TheSymmetryPlaneorBafflewillbecorrectlyvisualised,iftheMeshisAcoustic(MeshType:Acoustic)andaMeshPreprocessingSetisinsertedintheSpecificationTree.ToinsertanewSymmetryPlaneSet,clicktheInsert/EditaSymmetryPlaneSetbuttonintheAcousticModelDefinitiortoolbarorselectInsert-SymmetryPlaneSetf

54、romthemainmenu.Anewdialogboxwillappearasshownintheimagebelow.Figure:SymmetryandAnti-SymmetryPlanedialogPlanesX,YandZTheseplanesaredefinedbytheirpositionalongtheperpendiculardirectionwithrespecttothecoordinateaxisplane;forinstance,theX-symmetryplaneX=1000mmdefinesasymmetryplaneparalleltotheYZplaneand

55、passingthroughthepoint(1000,0,0).Althoughthegeometryshouldalwaysbesymmetricalinordertoallowthedefinitionofsymmetryandanti-symmetryplanes,theactualacousticalconditionscanbesymmetrical(identical)oranti-symmetrical(opposite)withrespecttotheplanedependingonthetypeofplaneselected.Thefollowingtablesummari

56、zestheeffectofdefiningsymmetricaloranti-symmetricalconditionsforbothacousticalandstructuralboundaryconditions:ACOUSTICALSTRUCTURALSYMMETRYPLANEZeronormalvelocityYn=0：RigidsurfaceZeroout-of-planetranslationsZeroin-planerotatonsANTI-SYMMETRYPLANEZeroacousticpressurep=0:FreesurfaceZeroin-planetranslati

57、onsZeroout-of-planerotationsFigure:SymmetryandAnti-SymmetryconditionssummaryUptothreemutuallyperpendicularsymmetryoranti-symmetryplanescanbedefinedsimultaneously.Ofcourse,onlyonesymmetryoranti-symmetryplanecanbedefinedparalleltoeachcoordinateaxisplaneXY,YZorXZ.Sinceacousticalsymmetryimplieszeronorma

58、lvelocity,definingasymmetryplaneisacousticallyequivalenttothepresenceofarigid,100%reflectingfloor.Inotherwords,ifyouaremodelingasituationwherethesound-radiatingstructureislocatedonahardfloor,e.g.theconcretefloorofasemi-anechoicchamber,thepresenceofthisfloorcanberepresentedsimplybyasymmetryplane.Conv

59、ersely,sinceacousticalanti-symmetryimplieszeroacousticpressure,definingananti-symmetryplaneisacousticallyequivalenttothepresenceofpressurereleasesurface.Thiskindofsurfacecanbeusedtomodelfreesurfaceslikeawater-airinterface.E.g.,ifyouneedtomodeltheacousticradiationintowaterfromasubmarineatacertaindept

60、h,youcanmodelthepresenceoftheseasurfaceabovethesubmarinebydefiningananti-symmetryplane.Whendefiningthesekindsofplanes,theyarerepresentedbycoloredsquaresurfaces.YoucanalsochangethecolorsoftheplanesbyselectingTools-OptionsAcousticsDisplaytab.Bydefault,symmetryplanesarerepresentedbysemi-transparentbrig