Learning Forum

[eperez6]

I am using ANSYS 2021 R2 and would like to run a modal analysis (rotordynamics) in Mechanical with general axisymmetric elements. I am using Workbench to link a Geometry (Spaceclaim) to a Mechanical Model and finally to a Modal analysis. With this approach I am unable to select general axisymmetric unless beta options are activated. However I can select general axisymmetric when my Mechanical Model is linked to a Static Structural analysis. Are general axisymmetric elements not supported by Mechanical modal analysis?

[Sheldon Imaoka]

Hi Ethan,

You're correct that General Axisymmetric is currently for static structural analyses only (this is noted in the Ansys documentation, under the "General Axisymmetric Overview" section of the Mechanical help).

For modal and other analyses, it may run with beta features turned on, but please exercise caution and check your results, as beta features are not fully supported or tested.

An alternative is to model the parts with a combination of beam, lumped mass, shell, or solid elements.  This can increase the DOF count depending on the model, but it's worth noting that for the general axisymmetric elements, you often need several nodal planes to accurately capture the bending response, anyway, so that results in higher DOF count for general axisymmetric models.  (The beam and lumped mass approach of modeling is the most computationally efficient.)

Regards,
Sheldon

 

[eperez6]

Hi Sheldon,

Thank you for the response. Yes I did notice that in the documentation and was interested in finding out more about the limitation. Are there any plans to fully support general axisymmetric elements in modal analysis?

[Sheldon Imaoka]

Hi Ethan,

This feature request is in the pipeline, but I don't have any specific dates or other information I can share with you, unfortunately.

Regards,
Sheldon

[eperez6]

 

Hi Sheldon,

I’ve read more of the documentation and have worked more in APDL since your last reply. It looks like general axisymmetric elements are supported for modal analysis using APDL. Is this correct?

 

[Sheldon Imaoka]

Hi Ethan,

Yes, you're right - in Mechanical APDL, the general axisymmetric elements supported modal analyses since its introduction many years ago.  It is just that this feature is not exposed in Mechanical officially (it's a beta feature in Mechanical).

Regards,
Sheldon

 

[eperez6]

Fantastic. Thank you for taking the time to respond. Mechanical APDL is my path forward.