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Hi! I am an engineering student and I am conducting a buckling analysis of a panel. All the nodes of the bottom side of the panel are fixed, I apply a forced displacement to all the nodes of the upper side of the panel and the analysis with SOL400 runs normally.

I want to create a Load/Displacement graph so I then tried to use RBE2 MPCs to apply the forced diplacement to one Node and constrain the movement of the nodes of the upper side in respect to that independent node so that I can measure the constraint forces on that node. Using RBE2 MPCs the analysis with SOL400 finishes but the results are problematic.

Is there a problem with the use of RBE2 with SOL400? Is there another way to measure the total constraint forces in order to create the Load/Displacement graph for the panel buckling?


Even if this is student post and this whole post will be deleted later, I want you to understand what you are doing. So copy paste it somewhere right away..
You most probably have all 6 degrees of freedom locked at your boundary nodes at the lower side of the panel.

On the upper side of the panel, you need to do the following for other cases;
1-) if all 6 degrees of freedom are locked at your boundary nodes at the lower side of the panel, to simulate a clamped condition at both 2 sides of your plate, you need to apply distributed forces on your upper side panel nodes (total of nodal forces will be equal to your total force - which you were applying to your RBE2 element earlier), and all upper node elements will be locked in the other 2 translational directions + 3 rotational directions (for clamped condition on 2 sides of the panel).
2-) for hinged conditions on 2 sides of the panel, you will do the exact same thing above. Only difference is you won't constrain rotational degrees of freedom.
3-) if you are trying to simulate buckling for 4 edge conditions (2 edges free 2 edges fixed, 4 edges fixed, 4 edges simply supported), you will need to see the answer for yourself by applying these conditions on square shaped panels and confirming those numbers with Bruhn buckling curves. But I'm guessing you won't need this part yet. 2 sides should be what you need for your elastic stability course.

I tried to outline in statement-3 your future cases too as it will be something you'll deal with if you become a structural/stress engineer, copy and paste this somewhere as your post will be deleted soon.

Aerospace Engineer, M.Sc. / Aircraft Stress Engineer


Thank you very much for the help!

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