Is there any normal stress on torsional member?

[385sk117]

Homework Statement

is there any normal stress on torsional member?

Homework Equations

The Attempt at a Solution

My professor showed me a circular rod made up of rubber and she made a rectangular hole on the side of it and asked whether there is any normal stress on the torsional member by showing how the circular rod is twisted when she twist it.
I know there must be a shear stress on the torsional member but normal stress?
Anyone knows the anwer and explanation for it?

 

[PhanthomJay]

When a rod is subject to torsionally applied loading only, there is only torsional shear stress on an element parallel and perpendicular to the rod's longitudinal axis. However, when you look at an element inclined to that axis, then you do get normal (tensile and comopressive) stresses at that point, per Mohr's circle calculations.