Learning Forum

[supreeth.k]

I'm working on a radial magnetic bearing model for modal analysis in ANSYS Workbench. I need to introduce negative axial stiffness into the bearing's behavior. What is the recommended approach to achieve this—either directly through the built-in connection settings or by using custom APDL commands (such as with COMBIN14 or MATRIX27)? Any insights or best practices would be appreciated.
Thanks!

[dlooman]

COMBIN14 would be the simplest way for a modal.  A nonlinear negative stiffness is possible with the transducer element, TRANS126, since electrostatic attraction increases as the gap closes.

[supreeth.k]

Thanks for the suggestion! Could you guide me on how to properly implement COMBIN14 for negative axial stiffness in my modal analysis? Specifically:

1. How do I extract nodes from a face selection where the bearing is located?

2. How should I assign a negative axial stiffness to the COMBIN14 element?

3. At what stage should I apply this APDL code to ensure it correctly affects the modal analysis?

Any detailed steps or example APDL commands would be really helpful. Thanks in advance!

[dlooman]

Like you would create any spring in the gui.  Use the Direct with a negative stiffness element.

[supreeth.k]

Thank you for your help