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I present three seperate models with thickness of t = 0.005m, 0.01m and 0.025m respectively, all have a forced displacement of -0.01m in the x-direction, and fixed on the other end. As you can see the critical load factor (number by which you have to multiply your loads to reach buckling) increases alongside the thickness.

enter image description here

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But then suddenly at thickness t=0.035m the buckling mode drops all the way to 0.04095. Could this be right or is there most likely something else going on?

enter image description here

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  • $\begingroup$ I would double check that you haven't used t=0.0035m instead of t=0.035m $\endgroup$
    – NMech
    Jun 27 at 18:09
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    $\begingroup$ Does this answer your question? Can a thicker model have a lower critical buckling load? $\endgroup$
    – Solar Mike
    Jun 27 at 18:31
  • $\begingroup$ You can trace the problem by applying the anticipated buckling loads (CLF*F) back to those models, and check the respective stress and displacement at locations currently shown. For all models, the stresses and displacements shall be identical as they all subjected to the buckling load in proportion to their thickness. Otherwise, either the program contains bugs or the way it reports the configuration is infinite rigid (L too short is one of the possibilities). $\endgroup$
    – r13
    Jun 27 at 19:00
  • $\begingroup$ If the last plot is "fixed on one end," why are all the "surface displacement magnitudes" approximately the same, i.e. something similar to a rigid body translation? Either you have an a modelling problem when you made the structure thicker, an input error, or a program bug (and I would guess one of the first two, not the bug). $\endgroup$
    – alephzero
    Jun 27 at 20:32
  • $\begingroup$ @alephzero, I am not sure I follow, they are all fixed, all have the same inputs, the only thing I changed was the thickness. I copied and changed the thickness of the model, no other change. $\endgroup$ Jun 27 at 20:35

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