Originally Posted by

**Zac C**
and if you actually understood the practical application of theory you would realize that T/theta = kt = JG/L. You are going down a rabbit hole of non-value added analysis.

you need to stop worrying about semantics and start thinking about how to logically setup an engineering problem. Calculating, measuring, or modeling some kind of a metric is meaningless without some kind of idea of how that result is useful. and once you have that understanding the problem (usually) becomes straight-forward.

Here's a partial list of questions you need to answer for yourself:

Why do I need a calculation of torsional stiffness?

How stiff is stiff enough?

How can I setup an FEA simulation that is both meaningful to real world operating conditions and can be easily verified in the lab?

Is my system linear? and if it is linear what does that mean for the loads I apply to the system?