Mechanics of Materials-Part 45 (Torsion-Examples on shaft replacement) | BME301

In engineering applications shafts are used to transmit power. While transmitting power they are subjected to torque or twisting moment. These torque may induce excessive shear stresses and deformations in the shafts leading to failure. Hence shafts have to be designed carefully to transmit power by keeping these stresses and deformations within safe limits.
Strength of a shaft is a measure of the torque or power transmitted by a shaft. For a given material it is directly proportional to the polar modulus of the cross section of the shaft. Torsional stiffness is the torque transmitted by a shaft per unit angular twist. For a given material and length of the shaft it is proportional to the polar moment of inertia.
In this class I have explained the percentage saving obtained when a solid shaft is replaced by a hollow shaft for the same torsional strength and torsional rigidity.