8.21 (B). (a) A solid circular steel shaft is subjected to a bending moment of 10 kN m and is required to transmit a maximum power of 550 kW at 420 rev/min. Assuming the shaft to be simply supported at each end and neglecting the shaft weight, determine the ratio of the maximum principal stress to the maximum shear stress induced in the shaft material.

A solid steel shaft will not twist through more than 3 degrees in a 6-m length when subjected to a torque of 12 KN*m. The modulus of rigidity of the steel shaft is 83 GPa. Determine; a) Diarneter of the shaft. (. b) Maximum shearing stress developed in the shaft.

3. A solid circular shaft is 1.8 m and is made of steel with G = 70 GPa. When rotating at w = 70 rad/s, it transmits 28 kW of power from engine A to generator B. As the design engineer, you are asked to: (a) Determine the shaft's smallest allowable radius if the allowable shear stress is T allow = 80 MPa. (b) Determine the shaft's smallest allowable radius If the allowable angle of twist is allow = 0.1 rad (in other words, the shaft is restricted not to twist more than 0.1 rad). (c) If both conditions (a) and (b) are required simultaneously, which radius will you select as the allowable radius. (In other words which condition controls the situation)? Briefly explain your answer. (1 kW = 1000 Watts) B

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