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Author Topic: Stiffness not changed for Buckling Constraint  (Read 5731 times)


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Stiffness not changed for Buckling Constraint
« on: October 01, 2018, 07:51:06 AM »
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)
  • 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 mm
However, 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 actualFactor

D11D11,req CurrentD11,req NextFactor

Do you know why the obviously high "Factor" does not lead to further panel thickening?
« Last Edit: October 01, 2018, 09:12:58 AM by JanPio »