The rotating solid steel shaft is simply supported by bearings at points B and C and is driven by a gear (not shown) which meshes with the spur gear at D, which has a 150-mm pitch diameter. The force F from the drive gear acts at a pressure angle of 20°. The shaft transmits a torque to point A of TA = 340 N · m. The shaft is machined from steel with Sy = 420 MPa and Sut = 560 MPa. Using a factor of safety of 2.5, determine the minimum allowable diameter of the 250-mm section of the shaft based on

(a) A static yield analysis using the distortion energy theory

(b) A fatigue-failure analysis.

Assume sharp fillet radii at the bearing shoulders for estimating stress-concentration factors.

TA 250 mm 100 mm 20