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FEM Direct Vibro-Acoustic Analysis Case TutorialObjective:The goal of this tutorial is to calculate the acoustic response of a glass/PVB plate (a laminated safety glass with a Polyvinyl butyral layer in between).The tutorial includes using the following analysis cases: Structural Modal case Direct Structural Forced Response Direct Structural Vibro-Acoustic Response Transmission LossThe model contains a Visco-elastic frequency-dependent material.Pre-Requisites:Software Configurations that are needed to run the tutorial: Licenses to set up the case in LMS Virtual.Lab: Desktop (VL-HEV.21.1 or equivalent) and Finite Element Acoustics (VL-VAM.36.2) When solving the acoustic response case, the license for product LMS Virtual.Lab FEM Vibro-Acoustics Structural Solver VL-VAM.45.2 is needed. Solving the Random Post-processing case to get the Transmission Loss curve will require the license for Random Vibro Acoustic Analysis (VL-NVP.20.3)Tutorial Data Files:StructuralGroups.xmlSAFyoung.xlsLaminatedStructure.bdfFPmesh.bdfAMLsender.bdfAMLreceiver.bdfAcousticGroups.xmlAll data files can be found on the APPS n DOCS DVD, in an archive called VAM_DirectVA-TL.For ease of use, it is best to copy all files to a local folder.STEP BY STEP Tutorial:STEP 1After starting LMS Virtual.Lab, create a new document in the Acoustic Harmonic FEMWorkbench (Start -Acoustics -Acoustic Harmonic FEM).STEP 2Select File Import from the main menu. The Import command can also be selected from the contextual menu of the Links Manager, by right clickingA file selector window appears allowing you to specify the file type and the file name. For more details, see Importing DataSelect the file type NASTRAN Bulk File (*.bdf, *.NS, *.nas, *.daO)nd browse for the file Laminatedstructure.bdf and click the Open button. A new dialog box appears requesting the selection of data that needs to be imported from the file. The data entries that are not available in the file are grayed out.Select in Split into Multiple Mesh Partuinder Mesh Creation and set the unit system to Meter, Kilogram, Second, click the OK button.JmpGiiFile Type |n5TRAU Bulk Fie (.bcf/.NS.nas/.dat)File Name| D；temp.aminated5tructure.bdfMesh Model ImportFinite Element MeshIrrrdiiii Reimport File ChangesLarrinatedStru匚tur巳- Nodes and ElementsLanrinatedStructurE - WireFrame MeshLarrinated5tructure - Acoustic Mesh %min. size15pit into Multiple Mesh PartsCr&atlonProperties and Flaterials r的QgjjlWcj 汕Irrport FE/Test Data SetsLCiMl辿幽皿5龚ILoejdlMajSBgSfilLengthMassTimeAngleTemperdtureMeterKilcgramSecondRadianCelsius degree Unit Systemj Derive Units oF Forces From Unit SystemCancelOKSTEP 3Next, the different structural materials will be defined. The two outer layers of the panel are made of Glass. To incorporate the 2% structural damping of this material, it will be modeled asa viscoelastic material with a constant complex Young modulus. The inner layer is made of PVB.Insert Materials New Materials .New Viscoelastic Material.Right-click on the Materials feature in the Specification Tree 9New Materials 3New Viscoelastic MaterialDefine the materials as follows:GLASSPVBYoung ModulusConstantPoisson RatioMassDensityYoung ModulusPoissonRatioMass DensityRealImaginary0.232500 kg_m3FrequencyDependent0.491066 kg_m37.15e+011N_m21.401e+009N_m2The PVB material at the center of the windshield has strong frequency dependent stiffness properties and is nearly incompressible. The frequency dependency can be incorporated in a viscoelastic material using an edited load function. The values can be imported from the Excel document SAFyoung.xls as follows:Check Frequency Dependent, and right-click the input field.Select New Function.-Mass DensityViscoelaEtic MaterialMl回甚IName|PV0Mate rid I ID:亚：己Cancel-Voun g Modulus:F Frequency DependentPoisEon R.atio:Q Modify Function* ConstantRemove FunctionX D.elete FunctionO Frequency dependent11066k:g_m3O ConstantRealImaginary牛 New FunctionIn the Attributes tab, enter as Name Youngs modulus PVB .In the Values tab, click the Import a file button, and browse to the excel file to select it.0 N/m2EnterDeleteSelect All InvEft SElEctionDispl=y Value as 画麻7ValuesOvEr.ieuMMerges |Recorder |AttributesVisible Sh-rkLeviel： |_ Q LZ r U D L4 /JjJ1=42 LltfLsIFreq |Hz|He N/m2| Im N/m2| Ampl |N- | PhaKr.- |Basic All CommandsLmd Function EditorSwitch the Data Format to Linear Amplitude/Phase (deg) because the file contains the values like that. Click the Import button.HieD:temp5iLFyaung.xle上，|Hll ModeData TypeO Real Complex一一一*D-ata is inPl/m2二|履己日ForrTdt; Liiea- Anplitude/Pl-ase (deg)二LFirst Irnporbsd R.ohzLast Imported Row;1囹Imported CalumnsArgument |J Ampl二 Phase=Import From DatasheetPreewRow人1PVB 5flF Young ModdusP，B 5AF YoLng ModulusVB5A= Young Moduus2X: LinearAmplfcudePhase degrees3(160 )1.C5E-07；32.6192430 4(200 2.13E-071:32.82201603 15(250 )2.13E-0733.02386756 6(=15 )L 2.E1E-07J.33.62390615 J7(dOO )Z.C9E-07；34.41114333 8(cnn )T.F-n?；.IRRIAA?9(30 )4.C6E-07136.12944414 10(皿)5.23E-0737.05280454 11(1000 )6.C0E+O7J38.30873557 WEis3 Mnf715十 OMidLl*Click the OK button of the Function Editor GUI.Click the OK button on the Material GUI.On the Edited Load Function Set, create (using the context menu) a 2D displayof typeComplex (Edited Load Function) on the Youngs modulus and check the curve:7 4fl+rKflEgfli-i-wn?.Bn4nO7 n+gr w45.102Fkt Mime-|PI忡函 TflJpiDQili Djmi 1 RFWOwfa r Muni:Set Mesh Parts TypeRight-click on the mesh in the Specification Tree, Set Mesh Part TypeSet as StructuralMesh PartSTEP 5In the next step, the model mesh will be imported from two Nastran input files. They each contain a mesh on which we will apply an AML property (Automatically Matched Layer), one on the receiver side, and one on the sender side.:File -Import Acoustic Mesh Model Mesh., and select the file AMLreceiver.bdfUse Meter, Kilogram and Seconds units, and include the materials and properties.Similarly, import AMLsender.bdf.At this point the mesh parts type definition window should look like this:r-JameTypePROPERTY 0StructuralGlassStructuralPVBStructuralAMLreceiverAcousticalAcoustic Envelope. 1AcousticalAMLsenderAcousticalType5et as Structural5et 己5 Acousticalll Show Deactivated Mesh PartsMeshJarts TypeSet as Field Point5et as SourceStatusDeactiveteCancelSTEP 6Inserting the New Material and properties for the new imported meshesInsert a new Acoustic material as follows (use the default values for air):FjjiiflMaterjaLUl 叵区Name Air-Material ID:5-Sound Velocity:RealImaginaryConstant|340m_s| Om_sO Frequency Dependent Mass Density: Constant0 Frequency DependentRealImaginary|1.225kg_m3 囹 10kg_m3囹iShow More Parameters项二Apply CancelInsert also a New Fluid Property. Call it also air, use the just defined material Air, and apply it to the two Acoustic mesh parts (Sender and Receiver side).Show More ParametersOK J Apply匚-、(:同STEP 7To facilitate the creation of the structural and acoustic model, some element groups have been predefined in xml files. To import these groups, first create mesh group sets.Insert a New Group Set, either from the contextual menu or with Insert Mesh Grouping Group Set.By right clicking the Group Set feature in the Specification Tree, insert a mesh group named Structural Groups, and in it import the 5 groups from the file StructuralGroups.xml.Right-click the Group Set, and use Mesh Grouping 3Group Selection Dialog:Similarly insert a mesh group namedAcoustic Groups,and in it import the 4 groups from the fileAcousticGroups.xmlRight-click the group set, and use again Mesh Grouping 9Group Selection Dialog:NameElementsFacesEdgesNodesVirtual ElementsVirtual NodesAML Sender3646AML Receiver3646Coupling Sender2858Coupling Fleceiver2S5SGroup SelectionStructural GroupsAcoustic GroupsStep 8Save the analysis, but without closing.SETTING UP THE ACOUSTIC CASESStep 1Insert a new acoustic automatically matched layer property to take into account the semi-infinite extent of the sender and receiver rooms. Insert a new AML property by right-clicking Properties, use New Acoustic Properties Automatically Matched LayerProperty.Apply it to the two Acoustic groups AML Receiverand AML Sender Switch the Radiation surface to User Define。and select the AML Receiver group.Automatically Matched Layer Property 匚|叵区Name Automatically Matched Layer Property. 1User DefinedRadiationStep 2Application R.egion2 GroupsRadiation surfaceShow More Parameters .Insert a Direct Vibro-Acoustic Response Analysis Case to compute the structural response and acoustic pressure fields in both the sender and receiver acoustic domains for each of the distributed plane wave excitations:To perform this calculation use No Load function Setand No Load Vector SetCreate new sets for all the rest.STEP 3Expand the Direct Vibro-Acoustic Response Analysis Case from the Specification Tree, right-click the Boundary Condition Set and use Acoustic Sources -Distributed Plane Waves. with a Refinement Levelof 2, a Radius of 4m, and an Acoustic Pressureon iPa. The plane waves will be used to excite the system and to calculate the transmission loss characteristics of the panel.Since the panel is not aligned with the xy plane, this coordinate plane cannot be used to define the location of the plane wave sources. So, for the Half Space Plane select Plane defined by Group and select the acoustic group Coupling Sender.Create DisitribLited Asuslic Plane V/dves P? X加ma I Distributed Acouzic Plans，Plane defined by Group | Couping SenderHalf Space Side -O Postivc # Negative O RjISelect the Negative Half Spaceside.Click the OK button to generate a set of 12 spatially distributed plane waves.By now the model should look similar to this:Minnie50 lLitori：r4 c OjxMltinsScxm psGwpl 叫 SurFpwSelle-AiMusi- vesd -repnxengleiiIMS1.； I h J lbStep 4We will now restrain the border of the glass panel.Right-click the Restraint Set, add an Advanced Restrainton the 3 Translational DOFs, and use as support the Structural Group BCsAdvanced Rjestraint匚恒队Name Advanced Restraint. 1Support GroupsBCsAxis Selection兴|G|0ba| Axi5三- Restrain Translation 1 Restrain Translation 2-Restrain Translation 3 Restrain Rotation 1 Restrain Flotation 2I I Restrain Flotation 3QK Applv Canc&lStep 5Coupling surface definition will be used to couple the upper and lower surfaces of the panel to the envelope surface of the acoustic cavity. When setting the Coupling Surface, the coupling between the structure and the fluid is on both sides.To correctly define the two-sided coupling in a transmission loss calculation, two coupling surfaces need to be created. From the Coupling Surface Set.1 feature, double-click the Coupling Surface Set.1, and add the two surfaces: Structural Group CouplingSendeand Acoustic Group Coupling SenderUse a tolerance of 10mm and select as Coupling Type One side. Click the Apply button.T Edited Load Function SellCreate Coupling Surface(Coupling Surfac.l* One Side O Both Sides| Co up ling SenderAcoustic Groups/Mesh PartsName Coupihg SurfatelStructural Groups/Mesh PartsTolerance10 mmCoupling lypeCcuplincSenderCoupling SenderCoupling Surface.!Structural GroupsJ拭 PVBI CouplificReCeiVer L w /L Acoustic GroupsI-AML SenderiI-* AML ReceEverl| -5G-Acoustic Mesh Preprocessing Set!I rCouplingSender1 Coupling Receiver , 口1，亡t /ihr d-AoduN匚 Rewpcnsw Arialysis Os旦 曰 Acoustic Boundary Conditions and SourcesI3 W引 in in l W.Coupling Surtax SellDo the same for the Receiver Sidein the end you should have two Coupling surfaces:Coupling Surface- Set DefinitionMumberJSurfdce NameToleranceCoufilimTyfieAddCoupling Surface. 10.01One SideR Remove2Coupling Surface.20.01One 5id 已Edit.CloseStep 6Double-click on the Direct Vibro-Acoustic Response solution to update the analysis parameters. In the current tutorial, the response at the center frequencies of the third octave bands between 160Hz and 2000Hz will be analyzed. In the Result Specifications tab, select User Defined values for the Argument Axis Definition and remove the standard analysis frequency range. Add a new frequency range definition and select a Logarithmic Stepdefinition with a starting frequency of 160Hz, an ending frequency of 2000Hz and a step of 1.122462048. Click the OK button to add the frequency range definition.mm Use InterpolationInterpolation Type: |Linearlrterpalation 亍|InterpolationSweep DefinitionStep: |5HzRequest Vector results at Field Points and for the Acoustic Potentials. No need to solve forStructural Displacements for now.Adjust the Solving Parameters. If your system is set up for parallel processing (see the Advanced Acoustic Installation manual), try one of the Parallelism types. Use the Direct solver.Adjust also the Job and Resources, e.g. to use multiple threads.Leave the Output Sets empty, meaning that results will be computed wherever possible.Step 7Update the Direct Vibro-Acoustic Response Solution to compute the acoustic pressure fields and structural deformations. This will take a while, as there are 23 frequencies and 12 load conditions. Save your model.Step 8Displaying the resultsOnce the computation is finished, right-click the DirectVibro-Acoustic Response Solution Set.1 feature and select Generate Image from the contextual menu.or select the solution feature and click the #Generate Image toolbar button.The Image Generation dialog box will appear, select the Pressure.Double-click the image feature in the Specification Tree, and in the Occurrences tab select the for example the first Load Condition(meaning the loading by the first distributed plane wave source) and set the frequency at 5 0 8Hz, click the OK button. For better visualization you can hide the Nodes and Elements feature, and the Boundary Conditions feature (with its plane wave sources).| SelectionsOccurrencesImge EditionData Cabt：Load Condition #2 of 12Load Condition #3 口F 12Load Condition #4 oF 12Load Condition #5 of 12Load C onditian #6 of 12Load Condition oF 12Load Condition #6 of 12Load Condition #9 of 12Load Condition rflQ of 12Load Condition #11 of 12Frequency I160H2 179.594Hz 201,587Hz 226.273Hz 253.982Hz 285,085Hz 319.996Hz 359.183Hz H03.169Hz|4乾占里He*工！p70164Hz639,986Hz7 IB. 359Hz |806.329HzVieuOKCanc&lYou can also display the 2D image curve for the Acoustic Power on the Kirchhoff surfaceRight-click the Direct Vibro-Acoustic Response Solution Set.1 feature and select NewFunction Display. from the contextual menu. The New Function Display dialog box will appear requesting you to select the different display images.Also you can use the button from the toolbar and select the Solution Set feature. A third possibility is to use the menu Insert 92D/3D Images 9New Function DisplaySelect the 2D Display from the list and click the Finish button.A new window, containing X- and Y-axes along with theSelect Data dialog box will now appear. In the Select Data dialog box, selectKirchhoff Surface Radiation: Snd click the Display buttonAs each of the distributed plane wave sources are independent, the sound power can be obtained by simply adding the individual contributions. So, select all 12 Data Cases , and check the option Sum over data cases.Switch the x-axis format to Octaves, and the Y-axis to dB(RMS). You can use dot markers for the curve by right-clicking it, using the Options. command in its context menu, and then changing the settings in the Visualization tab.Save your modelStep 9To get the transmission loss curve, we need to divide the total acoustic power on the receiver side by the total power on the sender side. Before we can do that, we need to combine the individual cases (one for each distributed plane wave source) to get the total power curves.Insert a Random Post-processing Case with Insert Other Analysis Cases Random Post-Processing Case.Refer to the solution of the previous response case, and select to process for aCross Power Set with Unitary Uncorrelated Load Cases:Update its solution using the context menu on its solution feature Random Response Solution Set.X. This will go fast.Right-click the sub-solution Global Indicator Set.X and create a New Function Displayon it. Select the 2D Displayas scenario, and click the Finish button.A 2D display window will appear with the Select Data dialog box open. In the General tab, switch the drop-down selector to Transmission Loss and select the entry Coupled Surface:S and click the Display button.You can see a TL value of 30.461911 dB for the 319.996 Hz octave band:Data TypeFrequency SpectraTheory for Panel Transmission LossCalculation of Transmission Loss using Vibro-Acoustic FEMThis topic describes how to set up a model and the computation to compute the Transmission Loss (e.g. for a panel) using the LMS Virtual.Lab tools.Stepl. Import of an Acoustic and Structural meshImport an acoustic mesh and a structural mesh with the modal data in the Acoustic Harmonic FEM workbench. There is no need to have a field point meshStep2. Create a New Acoustic PropertyDefine the Acoustic Properties including fluid propertiesand possible impedanceon the panel. Create an Automatically Matched Layer (AML) property for the source room on all faces that are not coupled to the panel and not touching the joined wall. The wall must be a zero velocity boundary condition. Also create an Automatically Matched Layer (AML) on the anechoic room side, which is defined as a Kirchhoff surface.Step3. Insert the boundary conditionCreate an acoustic boundary condition by selecting Insert Acoustic Boundary Conditions and Sources Acoustic Boundary Condition and Source Set. from the main menu.The Boundary Condition Set Creation dialog box appears as shown in the image below:Boujjjary ConditioQ Set CreatioiiBoundary Condition Set Edition| Acousti
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