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Static Simulation. Export to IGES and import as a solid?

Question asked by Paul Richards on Mar 8, 2017
Latest reply on Mar 9, 2017 by Paul Richards

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Hi All,

I've modelled a frame using weldments and I'm running a static study on it.

It's been a royal pain which is unusual and it doesn't like meshing properly either.

Is it good practice to export to an iges file then re-import and combine the individual items as a one piece solid and run the analysis?

I tried it on another very simple part and loaded it and allocated it identical material and the results were alarmingly different!

Here's a screenshot of the stress results from the original part file - you can that the results are not symmetrical even though it is constrained and loaded symmetrically.

Any comments would be greatly appreciated

Regards

Paul.

Ryan Dark Mar 8, 2017 1:20 PM

Correct Answer

Hi Paul,

As Alessandro Tornincasa said, the results are asymmetric because the mesh is asymmetric. If you are going to use solid elements to study your model then you may need to have a smaller element size than this. There should be a minimum of 2 high quality elements across all your thicknesses in the model. You would need even more elements than that for accurate and symmetric results. The number of elements required can quickly become large and unmanageable. If the model and loading are truly symmetric then you would want to use a half model with symmetry fixtures and dial the element size down so you can get under the 2 element across thickness minimum.

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Alessandro Tornincasa Mar 8, 2017 12:12 PM

You're using solid elements, why aren't you using beam elements ?

Meshing weldments with solid mesh is harder than with beams or shells.

If you want to have more success with solid mesh you should use curvature based mesher.

Results are not symmetrical because mesh is not.

Try using very fine uniform mesh, and you will see that results will be more symmetrical.

I personally wouldn't do that, I would rather:

- study half model

- put symmetry restraints

- use the option "display symmetric results" when post processing.

Alex

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Ryan Dark Mar 8, 2017 1:20 PM

Hi Paul,

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Paul Richards @ Ryan Dark on Mar 9, 2017 3:24 AM

Hi Both,

Many thanks for your responses.

Ryan, what you said is what I usually do but I was just trying to save some time!!!

I normally split the weldments with a mid surface then remove them after splitting. The two (inner/outer) tubes then get bonded and this gives the two elements on the ends of the tubes.

Guess I just have to do it the long way to get the results I need!!!

Regards

Paul.

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Alessandro Tornincasa Mar 8, 2017 12:12 PM
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You're using solid elements, why aren't you using beam elements ?
Meshing weldments with solid mesh is harder than with beams or shells.
If you want to have more success with solid mesh you should use curvature based mesher.

Results are not symmetrical because mesh is not.
Try using very fine uniform mesh, and you will see that results will be more symmetrical.
I personally wouldn't do that, I would rather:
- study half model
- put symmetry restraints
- use the option "display symmetric results" when post processing.

Alex
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Ryan Dark Mar 8, 2017 1:20 PM
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Correct Answer
Hi Paul,
As Alessandro Tornincasa said, the results are asymmetric because the mesh is asymmetric. If you are going to use solid elements to study your model then you may need to have a smaller element size than this. There should be a minimum of 2 high quality elements across all your thicknesses in the model. You would need even more elements than that for accurate and symmetric results. The number of elements required can quickly become large and unmanageable. If the model and loading are truly symmetric then you would want to use a half model with symmetry fixtures and dial the element size down so you can get under the 2 element across thickness minimum.
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- Paul Richards @ Ryan Dark on Mar 9, 2017 3:24 AM
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  Correct Answer
  Hi Both,
  Many thanks for your responses.
  
  Ryan, what you said is what I usually do but I was just trying to save some time!!!
  I normally split the weldments with a mid surface then remove them after splitting. The two (inner/outer) tubes then get bonded and this gives the two elements on the ends of the tubes.
  Guess I just have to do it the long way to get the results I need!!!
  
  Regards
  
  Paul.
  Like • Show 1 Like1
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Static Simulation. Export to IGES and import as a solid?

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