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3. Analysis in I-DEAS
In this section you will prepare the model in a way that it can then be solved by the software.
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Switch to the task
Boundary Conditions. In this task, you will set up the forces acting on the wheel.
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Figure 1.37
Click image to enlarge, or click here to open
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Click on the first icon in the Palette,
Linear Statics, so as to set up the problem as linear, as opposed to time-dependent (non-linear statics) or the like.
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Figure 1.38
Click image to enlarge, or click here to open
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In the upcoming dialog, accept all defaults by hitting OK.
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Figure 1.39
Click image to enlarge, or click here to open
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You will now apply a pressure on the surface that interfaces with the tire at the bottom of the wheel, so as to simulate the force of the street acting on the tire and further acting on the wheel. With your mouse, move over the region of the model that shows the surface in question. You may need to zoom and tumble, until you are able to unambiguously highlight the surface, which you have previously separated in StudioTools. Select the surface by clicking on it with your left mouse button, as shown in Figure 4. Note: If you accidentally select the wrong surface, you can unselect it by moving your mouse cursor into the black background region and clicking on your left mouse button.
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Figure 1.40
Click image to enlarge, or click here to open
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To apply pressure, click on the icon that features a bold
P, as shown in Figure 1.41.
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Figure 1.41
Click image to enlarge, or click here to open
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In the upcoming dialog, change the selection from
Intensity (Force/Area) to Total Force. This simplifies the problem conceptually, as we have a rough idea of how much force is acting upon the entire wheel, as opposed to a unit area. Next, if not already selected, choose N (newton) from the Amplitude list of units. Finally, enter the magnitude of the force; in this tutorial, we will apply a force of 3000 Newtons. This roughly corresponds to 300 kg for one wheel. We will argue that our motorcycle wheels experience a total of 600kg, including the rider, which is a reasonable and realistic assumption. (see Table 1.1)
Hit OK to apply the pressure.
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Figure 1.42
Click image to enlarge, or click here to open
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Table 1 features a comparison of weights for different automobiles and motorcycles. The assumption that a single wheel of a motorcycle will experience a weight of 300kg is reasonable as it appears to be at least twice the average weight. It is always better to overestimate the weight, so as to refrain from performing an analysis in the border region between actual and slightly more than expected.
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| Type of vehicle |
Weight with Rider (kg) |
| Automobile |
| Compact |
960 |
| Medium Sized |
1,415 |
| High Powered |
1,570 |
| Sportscar |
1,515 |
| High-Speed Sportscar |
1,500 |
| Motorcycle |
| Low Powered |
215 |
| Medium Powered |
272 |
| High Powered |
300 |
| Superbike |
265 |
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Table 1.1
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Blue arrows denote the applied pressure. The arrows must be pointing towards the center of the wheel. If they do not, you should either re-evaluate the model, or merely apply the negative pressure. In any case, you may wish to consult with the instructor, if the arrows are not pointing in the right direction.
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Figure 1.43
Click image to enlarge, or click here to open
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Next, you will apply a displacement restraint to the hub of the wheel. To this end, select the cylindrical hub of the wheel. You may again wish to zoom and tumble until you are able to unambiguously select the surface in question.
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Figure 1.44
Click image to enlarge, or click here to open
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To apply the displacement restraint, select the icon that features a triangle, as shown in Figure
1.45.
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Figure 1.45
Click image to enlarge, or click here to open
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In the upcoming dialog, you will notice that all values are set to 0 (zero), and their type is constant. You will not need to make any changes. These settings will pin down the hub of the wheel, so that regardless of the force acting on the other parts of the wheel, the hub never moves. On a motorcycle, this is principally true, if we're only considering the wheel itself. The wheel is attached to an axle, which in turn may move (displace), but the hub itself does not move relative to the axle, unless the wheel detaches during the ride, in which case this analysis won't matter anymore anyway.
Hit OK to accept the default values.
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Figure 1.46
Click image to enlarge, or click here to open
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Arrows of different color and direction denote the displcement restraint.
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Figure 1.47
Click image to enlarge, or click here to open
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You will now switch to the
Meshing task, in which the model is broken down into much smaller entities, which are then used to calculate displacement, stress, etc. of the entire model.
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Figure 1.48
Click image to enlarge, or click here to open
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Typically, we would first define a mesh size, which is the size of the elements into which the wheel breaks down to. However, I-DEAS will figure out a reasonable default size. We thus proceed to generating the mesh. Select the arrow next to the third icon, as shown in Figure
1.49.
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Figure 1.49
Click image to enlarge, or click here to open
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In the expanded list of icons, select
Solid Mesh
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Figure 1.50
Click image to enlarge, or click here to open
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Again you will select the entire model by moving the mouse cursor into the visualization frame, and clicking the right mouse button. In the upcoming list of options, select
All done.
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Figure 1.51
Click image to enlarge, or click here to open
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I-DEAS will now start the meshing process. Once it is finished, a list of options appear, asking you whether ot not to accept the mesh. Hit
Yes.
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Figure 1.52
Click image to enlarge, or click here to open
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You have now meshed the wheel. Make sure that the entire wheel is meshed, and not just a section of it, e.g. the hub.
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Figure 1.53
Click image to enlarge, or click here to open
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Next, you will define a material for this wheel. Click on the icon that features 3 symbols from the periodic table of elements, as shown in Figure
1.54.
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Figure 1.54
Click image to enlarge, or click here to open
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You will notice that only one material is available, named GENERIC_ISOTROPIC_STEEL. While you may wish to build your wheel from different materials, we will use steel to simplify the analysis. Regardless of the material used, the properties of stress and displacement hold true regardless of material insofar that weak spots in the structure do not change. Hence, we will be able to extract this information from the analysis regardless of material.
Feel free to experiment with creating new materials.
Select the material from the list, and hit
OK.
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Figure 1.55
Click image to enlarge, or click here to open
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You will now switch to the
Model Solution task, so as to set up solutions of interest.
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Figure 1.56
Click image to enlarge, or click here to open
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Click on the first icon, Linear, so as to define a linear solution, as shown in Figure
1.57.
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Figure 1.57
Click image to enlarge, or click here to open
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Next, you will create a solution set. Click on the second icon, as shown in Figure
1.58.
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Figure 1.58
Click image to enlarge, or click here to open
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In the upcoming dialog, click on the button
Create.
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Figure 1.59
Click image to enlarge, or click here to open
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In the next upcoming dialog, click on the blue-colored icon, as shown in Figure
1.60.
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Figure 1.60
Click image to enlarge, or click here to open
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In the following dialog, make sure that
LOAD SET 1 is selected in the list of Load Sets, and click OK on all three dialogs.
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Figure 1.61
Click image to enlarge, or click here to open
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You will now initiate the solution process. Click on the arrow next to the icon featuring a green arrow pointing to the right, as shown in Figure
1.62.
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Figure 1.62
Click image to enlarge, or click here to open
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In the expanded list of icons, select
Solve to start the solution computation.
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Figure 1.63
Click image to enlarge, or click here to open
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I-DEAS will now switch applications. In the upcoming dialog hit
Dismiss.
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| Figure 1.64 |
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If there are no errors in the model, I-DEAS will now start computing. A graph like the one in Figure
1.65 show the progress.
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Figure 1.65
Click image to enlarge, or click here to open
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Once the solution has been generated, I-DEAS will switch back to the previous application. In the upcoming dialog hit
Dismiss.
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| Figure 1.66 |
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