Adding analytic geometric stiffness for TACSShellElement #354
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sean-engelstad
approved these changes
Jan 30, 2025
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Code is looking good! Eigenvalues and buckling modes match for unstiffened panels with old complex-step buckling solution and the new exact G matrix buckling solution.
Testing panel buckling verification cases from my ml_buckling smdogroup repo
Case 1 - 3 x 1 aluminum unstiffened plate under axial loading,
mode 1- new (TACS eigval = 3.8507, CPT closed-form eigval = 4.000)
mode 1- complex-step (TACS eigval = 3.851)
mode 2 - new (TACS eigval = 4.2018)
mode 2 - complex-step (TACS eigval = 4.202 )
Case 2 - Unstiffened Metal Panel under Shear Load
The closed-form solution is not exact here, so I decided to compare modes and eigenvalues against previous complex-step case.
mode 1 - new (TACS eigval = 4.4387)
mode 1- complex-step (TACS eigval = 4.4387)
mode 3 - new (TACS eigval = 5.4138 )
mode 3 - complex-step (TACS eigval = 5.4138)
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Adding geometric stiffness implementation for
TACSShellElement.Implementation currently works, tested on both tri and quad elements.
Should significantly improve accuracy of buckling derivatives in real and complex mode (no more finite differencing over a finite difference).
Closes #246, Closes #294