A steel shaft of circular cross section is subjected to a twisting moment T. The controlli...

A steel shaft of circular cross section is subjected to a twisting moment T. The controlling factor in the design of the shaft is the angle of twist per unit length (Ψ/L; see Eq. 1.5). The maximum allowable twist is 0.005 rad/m, and the maximum shear stress is τmax = 30 MPa. Determine the diameter at which the maximum allowable twist, and not the maximum shear stress, is the controlling factor. For steel, G = 77 GPa.

 (1.5)