AnsweredAssumed Answered

Beam elements corrupt behaviour

Question asked by George Bon on Sep 25, 2013
Latest reply on Sep 25, 2013 by Jared Conway

Hi all,

 

I am doing some static stress analysis on ducts involving shell and beam elements.

 

Overall I can manage to get good results using workarounds, but there is one time consuming issue that I would like to solve:

 

After modifying the model slightly as part of my design iterations (e.g. some member sizes, load, etc, ) and re-running the analysis, the model will solve but in some parts of the model the beam elements will become much stiffer (it seems) to the point where there is no deformation in them. Typically if I am analyzing a square duct, one side will behave fine and the other will not (see example below).

 

The only way I found to keep working on the model is to create a new study and copy all the simulation features (bodies, joint group, connections, fixtures, external loads, and even mesh using the drag and drop method). Solving this new study without any modification works fine and gives correct results.

 

Therefore there seems to be a corruption of the simulation file (which happens all the time, I have to follow this 'new study/copy paste' process dozens of time for each analysis, which is causing the analysis to take 10 times the time it should).

 

At some point I thought this was caused by using mirror features in the model but removing them does not make a difference.

 

Example:

model.png

The main load on that duct is a downward pressure applied on the underside to represent dust filling.

 

Here are shots of the problematic results:

The left side behaves OK and deforms as expected:

2.png

The right side seems to have stiffened and hardly moves, and stresses on the ride side are 10 to 50 times lower than the left side:

3.png

Creating a new study and copying all simulation features solves the issue:

4.png

 

Please note I do not use the symmetry even though I could for other reasons.

 

Any ideas appreciated!

 

Thanks

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