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1、1FEM 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 caseDirect
2、Structural Forced ResponseDirect Structural Vibro-Acoustic ResponseTransmission 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 equiv
3、alent) 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 Rando
4、m 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 f
5、iles 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 22Select File Import from the main menu. The Import command can also be selected from the contextual menu of t
6、he 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 button.
7、 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 button.
8、 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 3as a viscoelastic material with a constant complex Young modulus. The inner layer is made of PVB.Insert
9、 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:GLASS PVBYoung ModulusConstantPoisson Ratio Mass DensityYoung ModulusPoisson RatioMass DensityReal Imaginary7.15e+0
10、11 N_m21.401e+009 N_m20.23 2500 kg_m3Frequency Dependent0.49 1066 kg_m3The 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 funct
11、ion. The values can be imported from the Excel document SAFyoung.xls as follows:Check Frequency Dependent, and right-click the input field.4Select 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 s
12、elect it.Switch the Data Format to Linear Amplitude/Phase (deg) because the file contains the values like that. Click the Import button.5Click 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 displ
13、ay of type Complex (Edited Load Function) on the Youngs modulus and check the curve:6STEP 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 Prope
14、rties Create 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
15、 Mesh Parts 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
16、 the receiver side, and one on the sender side.:7File 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: STEP 6 Inserting the New Material and properties for the new imported meshesInsert a new Acoustic material as follows (
