Buckling with Inertia Relief

[Senophoe]

I know this question has been asked a few times. I'm sure I checked almost every answer avaiable around. But I'm still having trouble using SOL 105 buckling with inertial relief.

Here's the .nas/.dat Nastran file: https://drive.google.com/file/d/1RrH_hMMeLpE3qEWH_Ea3nuVQBoBBindj/view?usp=drivesdk

Here's the error I'm having in the buckling set, from the f06 file:



I have INREL set to -1 in the Bulk Data:


I also have SUPORT1 defined in the Bulk Data:


And finally I'm running a STATIC SUBCASE with SUPORT1 and then calling it via STATSUB in another SUBCASE for buckling.



What am I doing wrong?

Photos of the setup.

The model is a LAMINATE composite tube with two RBE3, each with a load in the center node. I put the SUPORT1 constraint in a random node restricting 123456 dofs, just for test.

 

[sdm919]

Just a guess: Does your SUPORT1 node have the ability to take moments? The 456 on the support card basically require that point to have that ability.

Does your model have solid elements? Is the SUPORT1 node attached to only solid elements? That might be the problem. Solid elements cannot take concentrated moments., and you cannot support a rigid body about a point that cannot take moments.

I believe the SUPORT card allows you to apply rigid body restraints at different nodes, for example: restrain DOF=123 at one node, DOF=23 at another, and DOF=3 at a third (not all one a line). Then those 6 translational restraints serve to provide rigid body support in all 6 DOFs.

 

[Senophoe]

Just a guess: Does your SUPORT1 node have the ability to take moments? The 456 on the support card basically require that point to have that ability.

I uploaded the .nas/.dat file below. The model is a hollow cylinder. The skin is meshed with LAMINATE elements. I suppose those are capable of taking moments.

I put the SUPORT1 in one node in the skin. I did that just for testing.

Here's the .nas/.dat file with the model and complete analysis setup. Would you kindly help me out figuring out my mistake?

250703_INREL_18.nas

drive.google.com

Does your model have solid elements? Is the SUPORT1 node attached to only solid elements? That might be the problem. Solid elements cannot take concentrated moments., and you cannot support a rigid body about a point that cannot take moments.

I didn't use solid elements. The SUPORT1 node is a single nodal point in the cylinder skin. The structure is a hollow cylinder meshed with LAMINATE elements.

I believe the SUPORT card allows you to apply rigid body restraints at different nodes, for example: restrain DOF=123 at one node, DOF=23 at another, and DOF=3 at a third (not all one a line). Then those 6 translational restraints serve to provide rigid body support in all 6 DOFs.

I'll read Nastran documentation on how to do that using SUPORT1 card tomorrow. It's late night here now.
I suppose I'm allowed to have a single SUPORT1 entry in the Case Control section, which refers to a single SUPORT1 in the Bulk Data section. So I'm guessing I can simply modify my Constraint used as SUPORT1 to have different constraints at three different nodes.