t= 10 -Op- (а) (b)

1. A steel shaft is to be manufactured either as a solid circular bar or as a circular tube (Fig. 3-12). The shaft is required to transmit a torque of 1200 Nm without exceeding an allowable shear stress of 40 MPa nor an allowable rate of twist of 0.75%m. (The shear modulus of elasticity of the steel is 78 GPa.) a) Determine the required diameter d0 of the solid shaft. b) Determine the required outer diameter d2 of the hollow shaft if the thickness t of the shaft is specified as one-tenth of the outer diameter. c) Determine the ratio of diameters (that is, the ratio d2/d0) and the ratio of the weights of the hollow and solid shafts.