本帖最后由 superxjw 于 2013-5-16 20:37 编辑
帮助文档就在本版置顶的地方，你去下载了看一下吧，学这些东西，肯定是要习惯看帮助文档的。。。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 Polyvinyl butyral layer in between). The tutorial includes using the following analysis cases:
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 file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Acoustics file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Acoustic Harmonic FEM). STEP 2Select File file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif 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. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63446.gif 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. Insert file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Materials file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif New Materials file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif New Viscoelastic Material... [Right-click on the Materials feature in the Specification Tree file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif New Materials file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif New Viscoelastic Material] Define the materials as follows: | | | | | | | GLASS | PVB | Young ModulusConstant | 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 |
file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63448.png 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. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63449.png 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. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63450.png Switch the Data Format to Linear Amplitude/Phase (deg) because the file contains the values like that. Click the Import button. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63451.gif 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: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63453.gif 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 file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Properties file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif New Structural Properties file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Create 3D-Property [Right-click on the Properties feature in the Specification Treefile:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif New Structural Properties file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Create 3D-Property] file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63454.png file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63455.png file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63456.png 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 file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Set Mesh Parts Type [Right-click on the mesh in the Specification Tree, Set Mesh Part Type file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Set as Structural Mesh Part]
STEP 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 file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Import Acoustic Mesh file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Model Mesh..., and select the file AMLreceiver.bdf Use Meter, Kilogram and Seconds units, and include the materials and properties. Similarly, import AMLsender.bdf. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63457.png file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63458.gif At this point the mesh parts type definition window should look like this: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63459.gif STEP 6 Inserting the New Material and properties for the new imported meshes Insert a new Acoustic material as follows (use the default values for air): file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63460.gif 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 Receiver side). file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63461.png 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 file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Mesh Grouping file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif 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. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63462.png Right-click the Group Set, and use Mesh Grouping file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Group Selection Dialog…: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63463.gif Similarly insert a mesh group named Acoustic Groups, and in it import the 4 groups from the file AcousticGroups.xml Right-click the group set, and use again Mesh Grouping file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Group Selection Dialog…: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63464.gif 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-infinite extent of the sender and receiver rooms. Insert a new AML property by right-clicking Properties, use New Acoustic Properties file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Automatically Matched Layer Property.... file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63465.png Apply it to the two Acoustic groups AML Receiver and AML Sender. Switch the Radiation surface to User Defined, and select the AML Receiver group. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63466.gif 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: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63467.png To perform this calculation use No Load function Set and No Load Vector Set. Create new sets for all the rest. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63468.gif STEP 3Expand the Direct Vibro-Acoustic Response Analysis Case from the Specification Tree, right-click the Boundary Condition Set and use Acoustic Sources file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Distributed Plane Waves... with a Refinement Level of 2, a Radius of 4m, and an Acoustic Pressure on 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 Plane defined by Group and select the acoustic group Coupling Sender. Select the Negative Half Space side. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63469.gif Click the OK button to generate a set of 12 spatially distributed plane waves. By now the model should look similar to this: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63470.png Step 4We will now restrain the border of the glass panel. Right-click the Restraint Set, add an Advanced Restraint on the 3 Translational DOFs, and use as support the Structural Group BCs. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63471.gif 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 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 CouplingSender and Acoustic Group Coupling Sender. Use a tolerance of 10mm and select as Coupling Type One side. Click the Apply button. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/65044.png Do the same for the Receiver Side in the end you should have two Coupling surfaces: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/65045.gif Step 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 Step definition 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. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63474.png Request Vector results at Field Points and for the Acoustic Potentials. No 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 threads. Leave the Output Sets empty, meaning that results will be computed wherever possible. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63475.gif 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 results Once the computation is finished, right-click the Direct Vibro-Acoustic Response Solution Set.1 feature and select Generate Image from the contextual menu. [or select the solution feature and click the file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/26000.gif 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 508Hz, 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). file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63476.gif file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63477.gif You can also display the 2D image curve for the Acoustic Power on the Kirchhoff surface Right-click the Direct Vibro-Acoustic Response Solution Set.1feature and select New Function 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 file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/50556.gif button from the toolbar and select the Solution Set feature. A third possibility is to use the menu Insert file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif 2D/3D Images file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif New Function Display] Select the 2D Display from the list and click the Finish button. A new window, containing X- and Y-axes along with the Select Data dialog box will now appear. In the Select Data dialog box, select Kirchhoff Surface Radiation: S and click the Display button As 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. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63478.gif 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. file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/63480.gif Save your model Step 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 file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Other Analysis Cases file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/25979.gif Random Post-Processing Case... Refer to the solution of the previous response case, and select to process for a Cross Power Set with Unitary Uncorrelated Load Cases: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/65296.png 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 Display on it. Select the 2D Display as 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: file:///D:/Program%20Files/LMS/LMS%20Virtual.Lab%20OLH%2011-SL2/OnLineHelp/English/online/aco-tut/65298.gif | 
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