Virtual.lab声固耦合的隔声量仿真分析教程

FEM Direct Vibro-Acoustic Analysis Case Tutorial Objective: The goal of this tutorial is to calculate the acoustic response of a glass/PVB plate (a laminated safety glass with a Polyvinylbutyral layer in between). The tutorial includes using the following analysis cases: l Structural Modal case l Direct Structural Forced Response l Direct Structural Vibro-Acoustic Response l Transmission Loss The model contains a Visco-elastic frequency-dependent material. Pre-Requisites: Software Configurations that are needed to run the tutorial: l 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)" l When solving the acoustic response case, the license for product "LMS Virtual.Lab FEM Vibro-Acoustics Structural Solver VL-VAM.45.2" is needed. l 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.xml SAFyoung.xls LaminatedStructure.bdf FPmesh.bdf AMLsender.bdf AMLreceiver.bdf AcousticGroups.xml [All 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 1 After starting LMS Virtual.Lab, create a new document in the Acoustic Harmonic FEM Workbench (Start Acoustics Acoustic Harmonic FEM). STEP 2 Select File Import from the main menu. [The Import command can also be selected from the contextual menu of 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 Data] Select the file type NASTRAN Bulk File (*.bdf, *.NS, *.nas, *.dat) and 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 Parts under Mesh Creation and set the unit system to Meter, Kilogram, Second, click the OK button. STEP 3 Next, 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. Insert Materials New Materials New Viscoelastic Material... [Right-click on the Materials feature in the Specification Tree New Materials New Viscoelastic Material] Define the materials as follows:               GLASS PVB Young Modulus Constant Poisson Ratio Mass Density Young Modulus Poisson Ratio Mass Density Real Imaginary 0.23 2500 kg_m3 Frequency Dependent 0.49 1066 kg_m3 7.15e+011 N_m2 1.401e+009 N_m2               The 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. In the Attributes tab, enter as Name Young’s modulus PVB. In the Values tab, click the Import a file button, and browse to the excel file to select 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 type Complex (Edited Load Function) on the Young’s modulus and check the curve: STEP 4 Defining 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 [Right-click on the Properties feature in the Specification Tree New Structural Properties Create 3D-Property] Before the following steps please make sure the Mesh Parts are defined as types: PROPERTY0 – Structural Glass – Structural PVB – Structural This can be done by going to Tools Set Mesh Parts Type [Right-click on the mesh in the Specification Tree, Set Mesh Part Type Set as Structural Mesh Part] STEP 5 In 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.: