WS24-3. VND101, Workshop 24. Objectives. This exercise is design to introduce
vibration analysis in visualNastran Desktop. You will determine the natural ...
MSC.visualNastran Desktop FEA Exercise Workbook Pin and Bracket Assembly: Vibration Simulation in 4D
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Objectives This exercise is design to introduce vibration analysis in visualNastran Desktop. You will determine the natural frequencies of the part Learn how to display the mode shape contours for the foot support.
Exercise Overview Introduction to visualNastran Desktop 4D vibration analysis. Import/Open a model from various CAD applications. Simulation and Display Settings. Create a material. Apply restraints. Mesh the model. Solve model. Evaluate result.
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Step 1: Open Assembly / Connect Part
1) Open the associated Bracket_Pin.* file in C:\Training\vnd101_files\Workshop 24 using the CAD package you are working with. If no CAD package is available, import Bracket_pin.SAT or Bracket_Pin.x_t. If ACIS or Parasolid file is imported, skip sub-step 2, 3 and 4. Go directly to Creating Rigid Joint. 2) Connect the assembly or drawing over from Native CAD to MSC.visualNastran 4D Connecting the part over from Solidworks, MDT, Pro-e, Inventor, and SolidEdge utilize Automatic Constraint mapping which transfer mates into physical joints. 3) Once the assembly is brought in from CAD, you will notice that the bracket and the Pin is connected with a revolute joint. 4) Skip to Step 3: Constraint Navigator
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Figure 1 Open file
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Step 2: Creating a Rigid Joint
1) When bodies are imported, you have to manually create the constraint to simulate desired motion. For this assembly, we a rigid joint is need to hold the two parts together. 2) Hide the Pin and rotate the Bracket so the hole on the back face is visible shown in Figure 2. 3) Pick the Coord Icon from the toolbar and hover the mouse over the body. You will notice that vN 4D allows arc detection for easy placement in the center of the hole. Move the mouse to the hi-lighted circular edge until you find a cross-hair that allows you to place the coord in the center of the hole as shown in Figure 3.
Figure 2 Back face surface detection No Feature Detected
4) Left mouse click when the Arc is detected.
Arc Detected
Figure 3 Cross-hair Figure 4 Coord Placement VND101, Workshop 24
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Vertex Detected
Step 2: Creating a Rigid Joint 5) Turn the visibility of the pin back on and hide the bracket by right clicking on the Object List or the Body. 6) Repeat Step 3 and 4 and add another coord on one of the face of the Pin as shown in Figure 6. Pick the circular edge second to the back face. 7) Go to the Object List and expand on the two bodies so you can select the two Coords that we created. Hold down the Shift key to multi-select. See Figure 7.
Figure 5 Hiding and showing bodies
Figure 6 Coord Placement Figure 7 Selecting both Coords
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Step 2: Creating a Rigid Joint
8)
With the two Coords selected, Pick the Constraint Icon.
9)
Pick Rigid Joint when the Create Constraint Window appears.
10) Accept the Default Joint Type and Click Create 11) The rigid joint will appear as in Figure 9.
Figure 8 Selecting both Coords
Figure 9 Rigid Joint VND101, Workshop 24
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Step 3: Constraint Navigator
1) Right Click on the Pin and open the Constraint Navigator Constraint Navigator allows you to examine relationships among bodies, subassemblies, and constraints so that you can verify and modify your simulation model. 2) Navigate through constraint within the assembly by selecting Next on the toolbar and use the Move tool to see its motion shown in Figure 11. 3) Change the Revolute Joint to a Rigid Joint if it is not already so by Double Clicking on the constraint either in the Connection Window or the Object List Window. When changing a revolute joint to a rigid joint, you can either make the rigid joint measurable or optimized. In this case we will want to Optimized the rigid joint for faster simulation. 4) Click Close. Figure 10 Constraint Navigator
Figure 11 Navigating through constraints
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Step 4: Display and Simulation Setting
1) From the World menu select Display Setting or click the Display Setting button. 2) Click the Units tab. 3) Choose unit set English (pounds). Refer to Figure 12. 4) Click Close.
Figure 12 Display Settings - Units
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Step 4: Display and Simulation Setting
1) From the World menu select Simulation Settings or click on the Simulation Settings button. 2) Click on the FEA tab and select Vibration for Analysis type. 3) Specify 5 for Lowest modes in Desired modes. 4) Make sure the Desired outputs Displacement and Stress are selected. 5) Accept all other defaults as shown in Figure 13. Click Close. Figure 13 Simulation Settings - FEA
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Step 5: Specify Material 1) 2) 3) 4) 5) 6) 7) 8)
Double-click on the bracket in the simulation window. Select the Material tab. Click Edit. The Material Selector window appears. Select Aluminum 2024-T3 as shown in Figure 15. Click OK. Click the Appearance tab. Notice that the name “bracket_assy_piece-1” is already given. Leave everything else default. Click Apply and close. Repeat steps 1 thru 7 for the pin and notice that a name “pin_assy_piece-1” is also given. Choose Steel-ANSI 304 for the pin material.
Figure 14 Material Figure15 Material Selector
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Step 6: Apply Restraints
1) Rotate the assembly to get a better view of the holes. The faces of the holes will be selected for the restraint. 2) To apply restraints select Insert from the menu and choose Restraint or click the Restraint button.
Figure 16 Restraint placement
3) Select the face of one of the holes as shown in Figure 16. 4) Repeat step 2 and 3 for the next hole. Restraint symbols appear on the geometry. The model with restraints applied is displayed in Figure 17. Figure 17 Restraints
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Step 7: Meshing the Geometry
1) Double-click on the bracket in the simulation window. The Properties of body window appears. 2) Select the FEA tab and check Include in FEA. 3) Check Show mesh and enter “0.5” for the Default Mesh Size. Accept all other defaults. Refer to Figure 18. 4) Click the Mesh button to mesh the model. 5) Close the Properties window.
Figure 18 Properties of body - Mesh
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Step 7: Meshing the Geometry
6)
Now double-click the pin.
7)
Select the FEA tab in the Properties of body window that appears.
8)
Check Include in FEA.
9)
Check Show mesh and enter “0.2” for the Default Mesh Size. Accept all other defaults.
10) Click the Mesh button to mesh the model. 11) Close the Properties window. Solid elements are set by default. The simulation window now shows the bracket and pin with mesh elements. Shown in Figure 19. Figure 19 Meshed assembly
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Step 8: FEA Analysis 1) Click the Solve FEA button in the playback controls. 2) The MSC.Nastran analysis window appears to display analysis is in progress. The analysis may take a few minutes. 3) After results are completed. visualNastran Desktop will display the result in the simulation window. 4) If not already shown, results such as Mesh, Contours, Deformation and Forces can be displayed by right-clicking on the model in the simulation window. Refer to Figure 21. 5) Another way would be to click in the Properties List on FEA display and the Properties of body window appears. 6) Select the FEA Display tab and check on the respective result to display, as shown in Figure 22.
Figure 20 MSC.Nastran analysis in progress
Figure 21 Show Contours VND101, Workshop 24
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Figure 22 Display results
Step 8: FEA Results 1) Click the Display setting icon and select FEA Results. 2) 5 modes of vibration are shown. The current mode shown in the simulation window is 1. Each mode can be selected and animated in the simulation window. Refer to Figure 23.
Figure 23 FEA Results – Show different modes of vibrations
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Step 7: Results Animation
3) Select mode number 5 and click close. Notice that the Frequency of vibration is shown in the simulation window for both the pin and the bracket. In this case the resulting frequency for the pin is 0.00137 Hz and 5.84e+3 Hz for the bracket.
Frequency
4) The simulation window display the result as shown in Figure 24. 5) To animate the result click the Run button in the Playback Controls. 6) View other modes of vibration by changing the mode in the Display Settings.
Figure 24 Animate result
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Review You learned how to apply vibration analysis in visualNastran Desktop 4D. You learned how to display the contours of different mode shapes. You also learned how to animate the different mode shapes.
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