ABAQUS eigenvalue buckling analysis returning unexpected results

[pfsm01]

Good afternoon,

I am trying to perform a simple eigenvalue buckling analysis using ABAQUS. The setup is the classic rectangular plate subjected to uniformly distributed compression loads on two opposite edges. All edges are simply supported. The plate model uses shell elements and so I applied the loads in a linear perturbation step (buckle) as shell edge loads. The analysis returns eigenvalues, but when I multiply the eigenvalues by the applied edge load (I am assuming that the shell edge loads are input as force per unit length, and so I would have to divide by the plate thickness to obtain the actual stress), the resulting stresses do not match what one would expect from the plate buckling stress from plate theory. In fact, the values are not even close. Am I missing a step in the buckling analysis? What could be wrong?

Thank you and any help is much appreciated.

 

[SWComposites]

Could be a bunch of things:
- wrong boundary conditions
- wrong loads - you might have entered nodal forces (lbs), not element edge loads (lb/in)
- wrong material properties
- wrong coordinate system
- plate buckling equations are often given in load/width, not stress

Suggest you post the details of the plate you are analyzing: dimensions, thickness, material, etc, and your hand calculated bucking stress and FEM result. Also post a plot of the first mode shape.