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Problems with Unstable Model 1

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jharr11

jharr11

Automotive
May 3, 2011
7
Hey guys,

For the past couple of weeks I have been beating my head against a wall trying to do a static simulation study on a race car chassis part file. The error I keep getting is the "unstable model, restraints may not be adequate" one. I feel like I have tried everything to fix this but to no avail. I have checked the "use soft spring to stabilize model" box, and that didn't help. I have added over 400 bonded contact sets between all the tubes. I have tried using fixed geometry fixtures all over the place and that hasn't helped either. I really don't know what else to do to try to find where the problem is. Attached is a picture of the meshed model. ANY help would be greatly appreciated. I would be happy to provide more info if needed.

Thanks in advance,
-John
 
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Life would be so much easier if you used beam elements. Then find your critical connections and make sub models. I can't imagine how many unnecessary dof you have in this model. And you still won't get "real" stresses near the joints with such a coarse mesh.

Step back and ask what you are trying to find out.

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CSWP, BSSE

"Node news is good news."
 
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The entire model is beam elements. The mesh is not fine because I am trying to at least get the thing to run first before I even think about optimizing it.
 
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Also, submodels won't help me because I'm concerned with displacement in the model as a whole. As far as I'm concerned there are no unnecessary DOFs. I'm not interested in stresses. This structure will likely never see any stresses near it's limit.
 
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Thanks anyway for your help, but I've figured it out. Turns out I had not properly defined the contact between the small solids in the model and the beam elements. [thumbsup]
 
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I went through the model excluding features from the analysis one by one until I came upon a beam with an adjacent solid feature.
 
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