Nastran Tutorial Modified(1)

MUG ANALYSIS

MSC visualNastran Tutorial

Clarkson UniversityAndy Strong

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MUG ANALYSISMSC visualNastran 4D tutorial

Part One: Opposing Force Stress Analysis

1) Open visualNastran 4D (vN4D).

From the Start Menu Select: All Programs, MSC.visualNastran Desktop, MSC.visualNastran 4D.

Figure 1: MSC visualNastran 4D icons

2) Import mug model (mug.stp).

From the File menu select open and brose to the location of mug.stp. From the Specify length unit pull down menu, select in. Click Open.

Figure 2: Open window

3) Verify the model.

Right click on the mug model and choose Properties from the pull down menu. Select the Geometry tab. Verify that the model Width, Length and Height are 4.84in, 3.25in, and 4.5in respectively.

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Figure 3: Properties window

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4) Set the units.

From the World menu choose Display Settings. Open the Display Settings tab if it is not and select Units. From the Unit System pull down menu, select English(slugs).

Figure 4: Display Settings window

5) Add an FEA mesh to the model.

Right click the model and choose Properties from the pull down menu. Select the FEA tab and check the Include in FEA checkbox. Click the mesh button, wait for the mesh solver, and check the Show mesh checkbox.

Figure 5: Properties, FEA window

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Your model should look something like figure 6.

Figure 6: Model with mesh applied

This is a poor mesh representing this model, so we will change the FEA properties. In the FEA tab change Default mesh size to 0.125 and click Apply. Click Mesh and wait for the mesh solver to finish. Your model should now look like Figure 7. Obtain a printout of this. Uncheck the Show mesh checkbox and close the properties window.

Figure 7: Model with updated mesh5) Set the model material.

Right click the model and select Properties from the pull down menu and select the Materials tab. Under Material Properties click Change. From the Material pull down menu select Glass and click OK. Close the properties window.

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6) Apply forces to the model.

From the Insert menu select Force (or select the force icon ). Click on the model near the top (see figure 8) to apply a force. Rotate the model (middle mouse button or F4) and apply a second force (select Insert, Force, and click).

Figure 8: Forces applied on either side of model

Rotate (middle mouse button or F4) the model so you can see both forces:

Figure 9: Position of left and right forces

Right click on the green arrow representing the left force and choose Properties from the pull down menu. Under the Appearance tab change the Name to Left Force. Under the Structural Load tab change X, Y, and Z to 0, 100, and 0 respectively.

Figure 10: Force properties window

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Repeat this for the right force, but give it the name Right Force and use 0,-100, and 0 for the X, Y, and Z components.

7) Position the forces.

In the left multi-menu select Object Browser. Click the + box on Left Force and Right Force to expand them.

Figure 11: Location of Object Browser

Right click on the red coord under the Left Force expansion and choose Properties from the pull down menu. Under the Position tab (Pos) set X, Y, Z, Rx, Ry, and Rz to 0, -1.63, 4, 90, 0, and -180 respectively. Repeat this for the Right Force coord and set X, Y, Z, Rx, Ry, and Rz to 0, -1.63, 4, 90, 0, and 0 respectively. The forces should now be centered and directly opposing each other as in figure 12.

Figure 12: Coord properties window

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8) Run Stress Finite Element Analysis.

To run the FEA solver, click the Solve FEA button (be sure it is set to stress analysis by selecting the small carrot button to the right of the Solve FEA). This will generate a single frame FEA solution and map it in color to the model. In order to display the proper stress values, go to the World pull-down, then select Display Settings, FEA Display, and Contour Data. On the right side of the window select Stress and then change from von Mises to MAX_PRINCIPAL.

Figure 13: Location of Solve FEA button

Figure 14: FEA Stress solution

Save your analysis as MUG1.WM3. Be careful not to over-write this file in the next two sections. Obtain a printout of these results.

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Part Two: Applied Thermal Analysis

Open MUG1.WM3 and Save As MUG2.WM3.

Delete the two blue cords (red in Object Browser) by clicking on them and press Delete (Answer Yes when asked if you want to erase the FEA results). The two green force arrows should delete with them automatically.

The thermal analysis is more processor intensive (in its current state) so we will use a larger mesh on the model. Right click on the model; choose Properties from the pull down menu. Under the FEA tab, change Default Mesh Size to 0.25, press apply and then Mesh. Close the Properties window.

1) Add the Thermal Toolbar

From the World menu choose Display Settings. Expand the Preferences + box and select Toolbars. Check the Thermal check box (if it’s unchecked) and press apply and close. The thermal toolbar should appear in the upper window.

Figure 15: Thermal Toolbar

2) Add a Prescribed Temperature.

Double click on the Prescribed Temperature button and click on the inner surfaces of the mug (inside edge, bottom, and fillet between them).

*note: Double-clicking a constraint puts the constraint selection into "sticky mode" for continuous selection of multiple surfaces. Press escape to turn sticky mode off.

Figure 16: Mug with temperature applied to inside surfaces

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In the Object Browser, right click on each of the prescribed temperature constraints and select Properties. Select the Temperature tab and change the Prescribed Temperature to 200ºF for each constraint.

Figure 17: Object Browser

3) Add a Convective Heat Flux.

Double click on the Convective Heat Flux button and click on the outer surfaces of the mug (outside shell, bottom, handle and fillets between them). Press escape to exit sticky mode.

Figure 18: Mug with temperature and convection constraints applied

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4) Run the Thermal FEA Solver

Click the small carrot button next to the Solve FEA button and select Thermal from the pull down menu.

Figure 19: Changing analysis type

Click the Solve Thermal FEA button . This will generate a single Thermal FEA frame solution and map it in color to the model.

Figure 20: FEA Thermal Solution

Here we can see that this mug filled with a liquid at 200ºF will be about 100ºF on the outside of the mug and about 85ºF on its handle.

Save your analysis as MUG2.WM3. Be careful not to over-right this file in the next two sections. Obtain a printout of these results.

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Part Three: Applied Thermal Stress Analysis

Open MUG2.WM3 and Save As MUG3.WM3.

Part Two gave us an example of the heat flow through the mug when a temperature is applied to the inside of the mug and convection into air occurs on the outside of the mug. In the next part, we will apply a temperature to the entire mug and look at the internal stress.

1) Adjust applied temperatures

Press Control-F to delete the current FEA results. In the Object Browser select all of

the temperature constants ( , ) and delete them.

2) Set up temperature stress analysis

Highlight the mug by clicking on it. In the lower left corner of vN4D, there is a properties checkbox listing. Scroll through this menu, find Heat, and check its checkbox. When you do this, the Properties window for the mug should automatically pop up with the Heat tab selected.

Figure 21: Heat Properties

Under Temperature-Induced Stress check the Use the body temperature in a stress analysis checkbox. Enter a value of 200 degrees for current temperature, and 77 degrees for Stress-free temperature. Close the properties window.

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3) Run stress FEA analysis

Select the small carrot button next to the Solve Thermal FEA button, and select Stress.

Click the Solve FEA button to begin the FEA solution. This will generate a single frame FEA Stress solution and map it in color to the model.

Figure 22: Thermal Stress FEA results

Save your analysis as MUG3.WM3. Be careful not to over-right this file in the next section. Obtain a print out of these results.

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Part Four: Dynamic Stress Analysis

Open MUG3.WM3 and Save As MUG4.WM3.

In the last sections we did single frame analysis of stress due to force and temperature applied to the mug. In this section we will simulate a three foot fall of the mug onto a flat surface. vN4D will animate the mugs decent and we will find the frame at precisely the moment the mug hits the surface (within 1/10000s). We will run the stress FEA solver to determine the stress in the mug from hitting this surface.

1) Set up Environment

Push Control-F to delete the current FEA data. Right click on the mug and choose Properties. Select the Position (Pos) tab and change Rx, Ry, and Rz to 135, 0, and 0 respectively. This orients the mug so the upper lip strikes the surface when the mug falls. Under the Heat tab, uncheck Use the body temperature in a stress analysis. Close the Properties window.

Figure 23: Mug properties Position tab

Select the Box creation tool and move the curser to the right of the mug. Create a small box as in figure 24. This is a triple click tool. The first click designates the first corner of the box, the second click designates the opposite corner of a rectangle, and third click designates the height of the box.

Right click the mug and choose Properties. Under the Materials tab, set Mass to 0.024 slugs and Coeff. Restitution to 0.3.

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Figure 24: Mug and box

Right click on the box and choose Properties. Under the Position tab set X, Y, and Z to 0, 0, and -36 respectively. Also under this tab, check the Fixed checkbox. Under the Appearance tab, change the color of the box to one of your choice. Under the Box tab, set Width (X), Length(Y), and Height (Z) to 20, 20, and 0.5 respectively. This will turn your box into a flat surface in the proper location below the mug. Under the Materials tab set Coeff. Restitution to 0.3.

Press the ‘v’ key to zoom all objects. Your environment should now look like the one in figure 25.

Figure 25: Simulation Environment Figure 26: Collide selection

Click and drag in the vN4D window and completely surround both the box and the mug to select them both. Right click on one of the objects (with them both currently selected) and choose Collide from the pull down menu (Figure 26). This will tell vN4D to simulate a collision between the two objects.

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2) Run a Dynamic Simulation

Press the Run button and vN4D will calculate the decent of the mug and its collision with the flat surface. Let it run for a few hundred frames and then push the Stop

button.

Figure 27: Simulation Controls

Now that the simulation has run we can step through all the frames to see the mugs location at each frame. We can also run an FEA solution on any frame we like to see the internal stressed in the mug at that frame. Use the frame drag bar (in-between the Step Frame and Run buttons) and the Step Frame buttons to get to frame where the mug first

touches the flat surface. Use the Rotate button and the Zoom Box button to get an orientation as shown in Figure 28.

Figure 28: Mug striking surface.

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Note that each time you press the step frame button; the mug jumps a large distance. This is because our frame rate is set to 0.02, and we only get data calculated for these frames. Since first strike of the mug occurs during a very small amount of time, we will need to adjust the frame rate to something smaller and rerun the simulation.

Select Simulation Settings from the World menu. Under Simulation Settings, choose Integration and set Time to 0.0001 sec. Close the window.

Figure 29: Simulation Settings

vN4D will automatically delete the motion history and reset the mug to its starting location. Press ‘v’ to zoom all, and press Run to run the simulation with the new frame rate. The simulation will take much longer to run this time. Let the simulation run until 1 second (10,000 frames) has passed in simulation time and press stop. Use the frame slider and get to the frame where the mug just touches the flat surface, then use the frame step buttons to back up until you see a gap between the mug and the flat surface (about frame 4006). We will begin FEA stress analyses on this frame.

Figure 30: Mug just before it hits

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3) Run FEA Stress Analysis

Run a Stress FEA analysis on the current frame by pressing the Solve FEA button. This will generate a stress solution pertaining to the current frame. Since the mug has not yet hit the surface, it should appear completely blue in color, indicating there is zero stress.

Figure 31: Mug stress before collision

Press the Step Forward button to step forward a frame. Press the Solve FEA button again to calculation a FEA solution for this new frame.

Repeat this until the FEA solution gives some non-zero results. Continue stepping forward past this point a few frames. Now go back to the frame showing the large stress, which is the point of contact, and get a printout. If there is no frame showing large stress values similar to those below, you have missed the exact time when contact occurs. In this case go back and solve the analysis with a Time smaller than 0.0001 sec. Try 0.00005 next. Save your analysis as MUG4.WM3.

Figure 32: FEA Stress Results

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