Torsional vibration

[heindegroot]

Hi guys,


I need to perform a torsional vibration analysis to determine the torsional eigenfrequencies for a long shaft (30m) with an impeller on the end.
I tried to use a frequency study, but I only get lateral results. Does anybody know which function I can use?

(torsional vibration example:

http://www.epi-eng.com/mechanical_engineering_basics/torsional_vibration_intro.htm)

Any help is greatly appreciated.


Regards,


Hein de Groot

 

[kellnerp]

If you are only getting translational results it is probably because those eigenfrequencies are lower than the torsional eigenfrequencies in a modal analysis. How many eigenfrequencies are you telling Cosmos to recover?

If you constrain the shaft not to bend, but allow it to rotate then you should see rotational modes. Of course that will not be the correct problem, but it will be a good test to prove to yourself that rotational modes do exist.

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