A bar with a circular cross-sectional area is made of SAE 1045 carbon steel having a yield stress of sY = 1000 MPa. The bar is subjected to a torque T=3.75 kNm and a bending moment M=7 kNm. Using a factor of safety FS=2 with respect to yielding, determine the required diameter of the bar according to:
(a) the maximum-distortion-energy criterion (Von Mises)
(b) the maximum-shearing-stress criterion (Tresca)