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Active Contributor
drpalo
Posts: 48
Registered: ‎03-14-2011

CAD geometry & beam elements

270 Views, 6 Replies
03-30-2011 09:01 AM

After spending a day attaching beam elements to CAD geometry, I'm told I need to make changes to the model in Inventor. I make my changes, go to add-ins & mesh it to update the geometry in Algor. Now all my beam elements are gone. Are beam elements similar to nodel forces where changing the geometry means losing everything? If so, is there a way to permanently attach beam elements to CAD geometry while allowing model changes?

 

Thanks.

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Employee
S.LI
Posts: 398
Registered: ‎05-06-2010

Re: CAD geometry & beam elements

03-30-2011 10:30 AM in reply to: drpalo
I think this is hard, if beam elements are added on nodes that only exist in FEA model. In CAD model, you only have edge, surface etc. Everytime, when you switch from CAD to FEA, you will be asked to remesh your model. The previous nodes will be removed and have new nodes/meshes created. ... Maybe other people have good idea to do this.
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Active Contributor
drpalo
Posts: 48
Registered: ‎03-14-2011

Re: CAD geometry & beam elements

03-30-2011 11:25 AM in reply to: S.LI

It looks like if you place a construction vertices at each end of a beam element, it stays when the mesh is updated/changed. Is this a safe practice?

 

Thanks.

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Employee
S.LI
Posts: 398
Registered: ‎05-06-2010

Re: CAD geometry & beam elements

03-30-2011 11:57 AM in reply to: drpalo

Personally, I don't think this is a safe way.

But it might work for some cases.

 

 

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INACTIVE_AstroJohn
Posts: 492
Registered: ‎03-25-2010

Re: CAD geometry & beam elements

03-30-2011 02:48 PM in reply to: drpalo

Dr.,

 

Assuming the beam elements were drawn on a different part number, one not corresponding to any CAD part, then the beams should have remained after reimporting the CAD model. If not, please answer these:

  • what analysis type?
  • were any constraints added to the model? If so, what type?
  • was any type of surface or edge contact created between parts?

The construction vertices at the ends of the beam elements should guarantee that a node is generated on the CAD parts at each beam. That is one of the intended functions of the construction vertices.

 

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
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Active Contributor
drpalo
Posts: 48
Registered: ‎03-14-2011

Re: CAD geometry & beam elements

03-31-2011 05:17 AM in reply to: INACTIVE_AstroJohn

Yes, beam elements are a different part number than the CAD part. Static stress analysis with linear material model. Was also planning to run MES though. It is a single part with fixed constraints, no contacts. Are you saying the beam elements should automatically create construction vertices when attached to a CAD part? Or was manually adding the construction vertices the correct thing to do?

 

Thanks.

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Distinguished Contributor
bjorn_fallqvist
Posts: 316
Registered: ‎03-24-2010

Re: CAD geometry & beam elements

03-31-2011 08:07 AM in reply to: drpalo

I would suggest the following approach

 

1. Create the beam elements as you want them. (Rotate, move, copy lines etc.)

2. Select the nodes of the lines (select -> subentities -> vertices)

3. Right-click and choose "create construction vertices".

 

The vertices created away from the CAD model doesn't matter, they will just lie there without influencing the mesh. I have used this method for e.g. creating large number of bolts without having to make sure that the lines snap to nodes after rotating them.

 

Of course, you have to re-mesh after doing it.

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