Tubular shaft undergoes torsion

[Ry122]

For a system where a tubular shaft undergoes torsion, the maximum shearing stress in the steel shaft must not exceed 70MPa. The outside diameter of the tubular shaft is 50mm and the inside is 25mm
How do i determine the maximum torque that can be applied to the shaft?

 

[edziura]

The max shear stress occurs on the cross-section at the outer wall. The general torque equation is

\tau = \frac{Tc}{J}

where \tau in this case is the max shear stress, T is the max torque, and c is the outside radius.

J is the polar moment of inertia: J = \frac{\pi}{2} (co⁴ - ci⁴).

co =outside radius
ci = inside radius