I have developed some turbine blade models consisting entirely of SHELL63 elements that produced modal frequencies that agreed well with legacy NASTRAN models. The models included both spin loads and gas loads, utilizing standard nonlinear prestress modal analysis methods. At v11, the same models are showing frequencies that are up to about 0.5% different than the v10 frequencies. I also ran a very refined tet model and produced frequencies very close to the v10 results, so I am confident in these. What has changed with regards to these models between v10 and v11?

As part of a code enhancement, and to be consistent with Section 3.5 of the Theory Manual, the code was changed so that spin softening effects would be automatically included in stiffness matrix.

In addition, the spin softening stiffness matrix calculations were modified to be more consistent with theoretical formulation. The ANSYS Theory Reference Section 3.5 was also modified to reflect this change.

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