Simulation Question

[Anonymous]

Hi there,

I'm new to the simulation workspace. I'm trying to do a simulation where I apply a radial static load to a rubber disc and observe the displacement. Fusion 360 has no trouble solving the simulation, but the results don't appear to be helpful. I realize I'm probably not including enough information here for anyone to diagnose the problem but I'm also not sure what is necessary, so I figured I'd just post and get the ball rolling. Here's a screenshot of the results.

Thank you,

Zack

[TheCADWhisperer]

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@Anonymous wrote:

....to a rubber disc ...

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Linear analysis or non-linear?  

Attach your *.f3d file here. 

[Anonymous]

I'm not sure whether it's linear or non-linear. Are you asking about the material? If so, it's silicone rubber. 

I figured out that the reason I saw no color in the simulation is because my deformation scale was set to Actual instead of Adjusted. However, my results are still off. With one Newton of force the simulation is showing 370,000-470,000 millimeters of displacement, which is 5 or 6 orders of magnitude larger than what I would have expected.

.f3d is attached. 

[TheCADWhisperer · Accepted solution]

Your part has free degrees of freedom to slide anywhere along the XZ plane.

Select the option to Remove Rigid Body Modes (motion).

Also, it might be more appropriate to run non-linear analysis for this material.

[Anonymous]

Okay great, that worked. Question - because the part is uniform, I would expect the displacement to be equal at any given distance from the center of the disc. However, it's clear that the outside surface of the disc (on which all points are equidistant from the center y-axis) has varying shades of blue, indicating varying displacement values. Do you know why this is? Also, why do you say a non-linear study might be more appropriate? 

I tried my hand at a non-linear study. All of the materials in the non-linear library are metals and therefore very different than the silicone rubber I'm trying to model, so I attempted to make my own material with properties similar to rubber. I'm not sure exactly what went wrong, but Fusion wasn't able to solve the study. I've attached the updated .f3d with the non-linear study, which should show the failure I'm seeing as well.

[Anonymous]

Looking at the displacement results of the static stress simulation, it seems like the force on the inner surface of the disc is being applied unevenly. It's almost like the force starts on one side of the disc and then propagates around to the other side, giving a result where one side of the disc is displaced more than the other. Any ideas here?

[TheCADWhisperer]

Remember that you are doing Finite Element analysis.

Increase the density of your mesh.

Think of the mesher as a spider spinning a web.

The spider cannot build a perfect web.  The fewer elements in the web - the results might be skewed.

Note the exact numerical difference (not simply pretty colors).  Is it significantly different?

[Anonymous]

That makes sense, I was tripped up on the visual aspect of the results but the numerical differences are not significant. Thank you!