A hollow circular steel shaft is subjected to a torque of 800 N-m and a bending moment of 1200 N-m. The internal diameter of the shaft is 60% of the external diameter. Determine the external diameter of the shaft according to :
- maximum principal stress theory
- maximum shear stress theory
- shear strain energy theory
Take factor of safety as 2 and the yield strength of steel as 27 kN/cm2.