Engineering & Analysis Methods > Miscellaneous Analysis & Methods

Stiffness not changed for Buckling Constraint

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JanPio:
Hi,
I try to implement buckling constraint of 1 into my analysis.
My settings:

* Failure analyses: only stiffness requirements
* ABD components: all D_ij (also tested with all A_ij and all D_ij, same problem)
* one buckling load case from ANSYS
* panels in the region where buckling occurs first are "one stack unstiffened" starting at 2mm thickness, Max bound is sufficiently high
* all elements are in a common display set that is selected for the constraint
* FEA loads extraction: peak element filtered (if this makes a difference for FEA constraints)Working:

* Mode shape displayed in FEM Viewer
* correct Eigenvalue displayed in FEM Viewer
* max translation of 1 displayed in FEM Viewer
* iterations run without error
* buckling contraints, lambda_actual, lambda_req and the factor are shown in the iteration report
* the thickness is increased once from 2 to 3 mmHowever, the factor does not seem to be correctly translated into required stiffnesses of the panel (see table below).
Not working:

* the thickness is not further increased
* all component factors for stiffness are =1 (see table below)
* all margins of safety are (slightly) positive (probably because the required stiffness matches the actual stiffness in the table)
* there is no Mode Detection Parameter higher than the order of E-31, which seems very low to me      
lambda limitlambda actualFactor10.002128684469.7737189D11D11,req CurrentD11,req NextFactor181121.4823181121.4823181121.48231
Do you know why the obviously high "Factor" does not lead to further panel thickening?
Thanks,
Jan

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