… in a thin-walled circular cross-section#

The shear stress due to torsion in a circular cross section:
\[\tau(r) = \frac{M_tr}{2 \pi R^2 t} = \frac{M_tr}{I_p}\]
This is treated in chapter 6.2.1 of the book Engineering Mechanics Volume 2 (Hartsuijker and Welleman, 2007).
Exercises#
Exercises 6.5 - 6.8 and 6.15 of the book Engineering Mechanics Volume 2 (Hartsuijker and Welleman, 2007). Answers are available on this website.