Discussion Groups

Simulation Mechanical and Multiphysics

Reply
Active Member
blaeiouk
Posts: 8
Registered: ‎08-05-2010

Trouble with Buckling Analysis

278 Views, 3 Replies
10-01-2012 01:37 PM

I have created a simple 3D beam model and have solved it for static stresses/deflections.  No errors, results seem to be as expected.  When I then go to create a 2nd scenario to determine the Critical Buckling Load for the model, I get an error during Model Check.  The error says "0x6B: Invalid element number 1 in part 2: unexpected 2-node degenerate configuration."

 

What does this error mean?  What do I need to do to DS#2 to get it to run?  See attached .ach.

Please use plain text.
Active Member
blaeiouk
Posts: 8
Registered: ‎08-05-2010

Re: Trouble with Buckling Analysis

10-02-2012 03:47 PM in reply to: blaeiouk

Customer support just responded to a support ticket I logged for this topic.  I'm posting their response here to close out this issue.

 

"Thank you for contacting Autodesk support.  The error message you are receiving is caused by a defect related to defining beam orientation.  Unfortunately the beam orientation does not correctly copy over and causes the error.  The simplest way to resolve the issue to recreate/redefine a new beam orientation."

 

It worked.  Hope to see it fixed in the future.  I can foresee situations where this might be very tedious and time consuming.

Please use plain text.
Valued Mentor
Posts: 461
Registered: ‎08-30-2012

Re: Trouble with Buckling Analysis

10-03-2012 01:05 PM in reply to: blaeiouk

Hi blaeiouk,

 

Did you notice that the displacements in design scenario 1 are not symmetric? (see attached image) As far as I can tell, everything should be symmetric, but you would know your model better than I do.

 

If it is a discrepancy, it may be caused by the constraints or lack of constraints on your model. There is no constraint that prevents the model from rotating around the Z axis through your top I-beam. When I fixed that rotation, the displacement was about 2/3 of the previous maximum.

 

Looks like this blog has some good articles for those learning about FEA: http://puny211111.blogspot.com/2012/04/analysis-guidelines-for-beginners.html. I do not know who the author of the site is. Too bad he is not getting "full recognition" for his postings.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Please use plain text.
Active Member
blaeiouk
Posts: 8
Registered: ‎08-05-2010

Re: Trouble with Buckling Analysis

10-03-2012 01:40 PM in reply to: AstroJohnPE

Thanks John.  The asymmetry of the model is correct.  The constraints, as you point out, are not.  This is a bit of a test case that I'm using to creep up on the full problem model.  Constraining rotation of that beam is necessary and realistic.  Thanks.

Please use plain text.