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Model Not Stable

Question asked by Marc Lauzon on Aug 22, 2013
Latest reply on Sep 3, 2013 by Marc Lauzon

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Good evening,

I have a problem with a simulation I'm trying to do. The model isn't stable and I don't know why. The structure is 11.5m x 1.23m and the force applied is in N/m. No rotation is blocked. Y translations are blocked on each of the four extremities of the structure, X translations are blocked on the extremities of one side of the structure and Z translations are blocked for one extremity.

I have done a similar simulation with a different structure, and Solidwork was able to compute it no problem. Any clue?

Thank you

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11.5m x 1.23m structure.pdf148.0 KB

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Jared Conway Aug 22, 2013 6:20 PM

Use soft springs or extra fixes restraints to figure out where you're missing contact or connectors.

We recommend in out training to start small. Add one part at a time with a gravity load till you have the whole structure. If you run into an issue, you'll know where it happened.

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Robin Boudreault Aug 30, 2013 3:59 PM

I had lots of cases where it was just a bug related to the mesher. It happened only with quadratic element and was ok with draft elements.

Try solid elements instead of beam element to do a quick test. You can also look at it by changing the force by an imposed displacement. Doing so, parts won't go at an infinite position and throw an error message. Soft spring can help in some case too.

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Marc Lauzon @ Robin Boudreault on Sep 3, 2013 10:48 AM

Found it! The transversals at each ends were at fault. I removed them and remodeled them using a different sketch and it works. No need for soft springs either. I still don't know why that happened thou, since all the other transversals worked, but not those two...

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Jared Conway Aug 22, 2013 6:20 PM
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Use soft springs or extra fixes restraints to figure out where you're missing contact or connectors.

We recommend in out training to start small. Add one part at a time with a gravity load till you have the whole structure. If you run into an issue, you'll know where it happened.
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Robin Boudreault Aug 30, 2013 3:59 PM
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Correct Answer
I had lots of cases where it was just a bug related to the mesher. It happened only with quadratic element and was ok with draft elements.

Try solid elements instead of beam element to do a quick test. You can also look at it by changing the force by an imposed displacement. Doing so, parts won't go at an infinite position and throw an error message. Soft spring can help in some case too.
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- Marc Lauzon @ Robin Boudreault on Sep 3, 2013 10:48 AM
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  Correct Answer
  Found it! The transversals at each ends were at fault. I removed them and remodeled them using a different sketch and it works. No need for soft springs either. I still don't know why that happened thou, since all the other transversals worked, but not those two...
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Model Not Stable

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