Autodesk Simulation Mechanical and Multiphysics

[#1]

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.

[#2]

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.

[#3]

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.

[#4]

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.