Question

A shaft is subjected to pure torsion. The state of stress at any point on the surface of the shaft, relative to the axis of the shaft, consists of

• A. pure normal stress
• B. pure shear stress
• C. equal normal and shear stresses
• D. zero stress

Hint:

While the stress state relative to the shaft axis is pure shear, if you rotate the element by $45^\circ$, the stress state becomes pure normal stress (tensile and compressive stresses of magnitude equal to $\tau$).
This explains why brittle materials fail at $45^\circ$ under torsion.

Answer 1

The Correct Option is B