Virtuallab声固耦合的隔声量仿真分析教程.docx

1、Virtuallab声固耦合的隔声量仿真分析教程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:Structur

2、al Modal caseDirect Structural Forced ResponseDirect Structural Vibro-Acoustic ResponseTransmission LossThe model contains a Visco-elastic frequency-dependent materialPre-Requisites:Software Configurations that are needed to run the tutorial:Licenses to set up the case in LMS Virtual.Lab:uDesktop (V

3、L-HEV.21.1 or equivalent)1 and Finite Element Acoustics (VL-When solving the acoustic response case, the license for product ULMS Virtual.Lab FEM Vibro-Acoustics Structural Solver VL-VAM.45.2” is neededSolving the Random Post-processing case to get the Tansmission Loss curve will require the license

4、 for nRandom Vibro Acoustic Analysis (VL-nTutorial 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 al

5、l 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 comma nd can also be selected from the con textual menu

6、of the Links Man ager, by right clickingA file selector window appears allowing you to specify the file type and the file nameFor more details, see Select the file type NASTRAN Bulk File (匸bdf, *NS# .nasf dat) and browse for the file Laminatedstructure bdf and click the Open butt on. A new dialog bo

7、x 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 Patsun der Mesh Creation and set the unit system to Meter, Kilogram, Second, click the OK buttOn.STEP 3Next, the d

8、 iff ere nt structural materials will be defined The two outer layers of the panel are made of Glass To in corporate the 2% structural dampi ng of this material, it will be modeled as a viscoelastic material with a constant complex You ng modulus The inner layer is made of PVB.Insert -Materials -New

9、 Materials -New Viscoelastic Material.Right-click on the Materials feature in the Specification Tree -New Materials -New Viscoelastic MaterialDefine the materials as follows:GLASSPVBYoung ModulusConsta ntPoisson RatioMassDensityYoung ModulusPoiss onRatioMass DensityRealImagi nary0232500kg_m3Frequenc

10、yDependent0491066 kg_m3715e+011N_m2:L401e+009N_m2The PVB material at the center of the windshield has strong frequency dependent stiffness properties and is n early in compressible The frequency depe ndency can be in corporated in a viscoelastic material using an edited load function. The values can

11、 be imported from the Excel document SAFyoung.xls as follows:Check Frequency Dependent, and right-click the input fieldSelect New FunctionIn the Attributes tab, enter as Name Young s modulus pvbIn the Values tab, click the Import a file button, and browse to the excel file to select it.Switch the Da

12、ta Format to Linear AmpHtude/Phase (deg) because the file contains the values like that. Click the Import butt on.Click the OK button of the Function Editor GULClick the OK button on the Material GULOn the Edited Load Function Set, create (usi ng the con text menu) a 2D display & type Comp/ex (Edite

13、d Load Function) on the Youngs modulus and check the curve:STEP 4Defining two Structural 3D properties for Glass and PVB, applied to the structural groups Glass (with the defined material Glass) and PVB (with the defined material PVB).Insert -Properties -New Structural Properties -Create 3D-Property

14、Right-click on the Properties feature in the Specification Tree- New Structural Properties -Create 3D-PropertyBefore the following steps please make sure the Mesh Parts are defined as types:PROPERTY0 一 StructuralGlass 一 StructuralPVB 一 StructuralThis can be done by going to Tools -Set Mesh Parts Typ

15、eRight-click on the mesh in the Specification Tree, Set Mesh Part Type -Set as Structural Mesh PartSTEP 5In the next step, the model mesh will be imported from two Nastra n in put files They each contain a mesh on which we will apply an AML property (Automatically Matched Layer), one on the receiver

16、 side, and one on the sender side.:File -Import Acoustic Mesh -Model Mesh., and select the file AMLreceiver .bdfUse Meter, Kilogram and Seconds un its, and in elude the materials and properties Similarly, import AMLsender bdf At this point the mesh parts type definition window should look like this:

17、STEP 6Inserting the New Material and properties for the new imported meshesInsert a new Acoustic material as follows (use the default values for air):Insert 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 Receive

18、r side).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 setsInsert a New Group Set, either from the contextual menu or with Insert -Mesh Grouping -Group Set.By right clicking

19、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 -Group Selection Dialog.:Similarly insert a mesh group named Acoustic Groups, and in it impo

20、rt the 4 groups from the file AcousticGroups xmlRight-click the group set, and use again Mesh Grouping -Group Selection Dialog.:Step 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-inf

21、inite extent of the sender and receiver rooms Insert a new AML property by right-clicking Properties, use New Acoustic Properties -Automatically Matched Layer Property.Apply it to the two Acoustic groups AML Receiver and AML Sender. Switch the Radiation surface to User Defined, and select the aml Re

22、ceiver groupStep 2Insert a Direct VibroAcoustic 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 Set and No Load

23、Vector Set.Create new sets for all the rest.STEP 3Expand the Direct VibroAcoustic Response Analysis Case from the Specification Tree, right-click the Boundary Condition Set and use Acoustic Sources -Distributed Plane Waves. with a Refinement Leveled 2, a Radius & 4m, and an Acoustic Pressure on lPa.

24、 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 def

25、ined by Groups nd select the acoustic group coupling sender Select the Negative Half Space side.Click the OK butt on to gen erate a set of 12 spatially distributed plane waves By now the model should look similar to this:Step 4We will now restrain the border of the glass panel.Right-click the Restra

26、int Set, add an Advanced Restraint qv the 3 Translational DOFs, and use as support the Structural Group BCs.Step 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 couplin

27、g 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

28、CouplingSender and Acoustic Group Coupling Sender. Use a toleranee of 10mm and select as Coupling Type One side. Click the Apply button.Do the same for the Receiver Side in the end you should have two Coupling surfaces:Step 6Double-click on the Direct Vibro-Acoustic Response solution to update the a

29、nalysis 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 for the Argument Axis Defin ition and remove the stan da rd an alysis freque ncy range Add a n

30、ew frequencyange definition and select a Logarithmic Step definition with a starting frequency of 160Hz, an ending frequency of 2000Hz and a step of 1 8. Click the OK butt on to add the frequencyange defi nition.Request lector results at Field Points and for the Acoustic Potentials. No need to solve

31、 for Structural Displacements for nowAdjust the Solving Parameters If your system is set up for parallel processing (see the Advaneed Acoustic Installation manual), try one of the Parallelism types Use the Direct solver.Adjust also the Job and Resources, e.g. to use multiple threadsLeave 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