MecMovies 4.0 : M6.22: Maximum Torque Applied to Coaxial Shaft

Diagram shows a shaft A B with aluminum segment marked 1 of length 400 millimeters inside which is a brass shaft marked 2. Both the shafts are centered on the central axis x. A torque T is applied at B.

$\frac{τ_{1} L_{1}}{c_{1} G_{1}} = \frac{τ_{2} L_{2}}{c_{2} G_{2}}$

We will pick one of the shafts and assume that its shear stress is equal to its allowable stress. Using the relationship above, we will compute the corresponding shear stress in the other shaft.

If its shear stress is less than its allowable shear stress,
we have guessed correctly and we can proceed to solve the problem.

If its shear stress is greater than its allowable shear stress,
we have guessed incorrectly and we must revise our stress calculations before we proceed.