Strength of Materials

6.4 TORSIONAL STIFFNESS AND RIGIDITY

In Equation (6.12) for torque, T, f_s may be substituted from Equation (6.4) and rewritten as

 

 

where I_p = π D⁴/32 is the polar moment of inertia of a circular cross section.

Thus, combining Equations (6.8) and (6.14) we have

 

 

Thus, the torque required for unit twist, i.e., T (θ) is called the torsional stiffness.

From the above relation,

The quantity is known as torsional rigidity and is represented ...