In solid shaft, stress at the centre is

Explanation:

Distribution of shear stresses in circular Shafts subjected to torsion is given by,

where, T = twisting moment, r = Radius of the shaft and J = polar moment of inertia

This states that the shearing stress varies directly as the distance ‘r' from the axis of the shaft.

The maximum shear stress occurs on the outer surface of the shaft where r = R.

For the solid shaft, at the centre, the stress is zero.

Stress is never zero in the hollow shaft although it is minimum at the inner surface of the shaft.