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: Struc

2、tural Modal caseDirect Structural Forced ResponseDirect Structural Vibro-Acoustic ResponseTransmission LossThemodel 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

3、 (VL-HEV.21.1 or equivalent) and Finite Element Acoustics (VL- 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 lice

4、nse for Random Vibro Acoustic Analysis (VL-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 calledVAM_DirectVA-TL. For ease of use, it is best to copy al

5、l files to a local folder.STEP BY STEP Tutorial:STEP 1 After starting LMS Virtual.Lab, create a new document in the Acoustic Harmonic FEM Workbench (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

6、 the Links Manager, by right clicking A 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, *.dat) and browse for the file LaminatedStructure.bdf and click the Open butto

7、n. 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 Parts under Mesh Creation and set the unit system to Meter, Kilogram, Second, click the OK butto

8、n. STEP 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 as a viscoelastic material with a constant complex Young modulus. The inner layer is made of PVB.Inser

9、t Materials New Materials New Viscoelastic Material.Right-click on the Materials feature in the Specification Tree New Materials New Viscoelastic MaterialDefine the materials as follows:GLASSPVBYoung ModulusConstantPoisson RatioMass DensityYoung ModulusPoisson RatioMass DensityRealImaginary0.232500

10、kg_m3Frequency Dependent0.491066 kg_m37.15e+011 N_m21.401e+009 N_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.

11、 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.In 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

12、 it.Switch the Data Format to Linear Amplitude/Phase (deg) because the file contains the values like that. Click the Import button.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 display of

13、type Complex (Edited 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 C

14、reate 3D-PropertyRight-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 StructuralGlass StructuralPVB StructuralThis can be done by going to Tools Set Mesh P

15、arts TypeRight-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 Nastran input files. They each contain a mesh on which we will apply an AML property (Automatically Matched Layer), one on the re

16、ceiver 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 thi

17、s: STEP 6 Inserting 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 definedmaterial Air, and apply it to the two Acoustic mesh parts (Sender and Rece

18、iver 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 sets. Insert a New Group Set, either from the contextual menu or withInsert Mesh Grouping Group Set.By right clicki

19、ng 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 imp

20、ort the 4 groups from the file AcousticGroups.xmlRight-click the group set, and use againMesh 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-infi

21、nite 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 Rec

22、eiver group.Step 2Insert 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 Set and No Loa

23、d Vector Set.Create 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 Level of 2, a Radius of 4m, and an Acoustic Pressure on

24、1Pa. 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 Pla

25、ne defined by Group and select the acoustic group Coupling Sender. Select the Negative Half Space side.Click the OK button to generate 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

26、Restraint Set, add an Advanced Restraint on 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

27、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 twosurfaces: Structural

28、 Group CouplingSender and Acoustic Group Coupling Sender. Use a tolerance 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 upd

29、ate 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 r

30、ange. Add a new frequency range 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 button to add the frequency range definition.Request Vector results at Field Points and for the Acoustic Potentials. N

31、o need to solve for Structural 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 thread

32、s.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