i performed a frequency study to calculate the first torsional resonant frequency but i didn't find where i can read it.
it shows me only 0Hz for the first resonant frequency.
i attached below the part and my frequency study.
For an unrestrained frequency analysis you should expect that the first 6 natural frequencies will be 0 Hz representing the 6 rigid body motions (3 translations; 3 rotations) an unrestrained body can undergo. In the analysis you have in this file the study 'Properties' (found by right clicking the study name and going to 'Properties') only have the solver solving for the first 5 frequencies:
You will need to edit this value in the study 'Properties' to solve for a large number of frequencies (20+?) then run the solver again. Once you do that you can edit one of the amplitude plots and go through the resulting frequency modes to find a torsional mode:
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