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Contact constraints - equilibrium not achieved

Question asked by 1-5IS351 on Apr 12, 2010
Latest reply on Apr 13, 2010 by Derek Bishop

I'm modeling a bolted assembly using both manually defined and globally defined contact sets (no penetration - with friction) as well as bolted connections (with nuts).

 

I have run this analysis many times and I keep running into the "equilibrium not achieved - do you want to save results up to this point?". I click yes - the simulation continues and I can get results that seem legit.

 

I have several questions:

 

1) What is the significance of this message (if I can still get results)?

2) What am I doing wrong to result in getting this error and how can I prevent it?

 

I have worked with many FEA programs (I even wrote one in Matlab in college) so I understand the math under the hood. I can address this error by adding BC's and eliminating contact gaps. But, these are illegitemate shortcuts that just get me a result. I should only need enough BC's to constrain my parts and no more. Plus, I want the contact gap solution "solved" rather than adding fake surface interface conditions just to get it to work.

 

I'm posting this from home (I'm at hour 13 of my analysis - fourth or fifth "equilibrium not achieved" error message) so I can't post a screenshot or file of the part. I can tomorrow if that would help. I'm more interested in general direction as it relates to the "equilibrium not achieved" error and ways to address it (other than fake constraints or removing gaps).

 

Thanks for any help!

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