A rotating Steel shaft (as shown in Figure 4.35) used in a spur gear reducer is subjected to a constant torque together with lateral forces that tend to bend it downward in the center producing fluctuating stresses of 60 MPa bending and steady stresses of 80 MPa torsion. These values, however, do not take into account stress concentrations caused by the stepped shaft (shoulder). The fatigue stress concentrations caused by the shoulder of the shaft are K_fb = 1.53 for bending and K_ft = 1.28 for torsion. The surfaces are in machined and the Steel has a hardness of 200 Bhn and strength values of S_u = 700 MPa and S_y = 550 MPa The modified endurance limit is 239 MPa The stepped shaft has D/d =1.2, d = 30 mm, and r = 3 mm. Find: Determine the safety factor with respect to infinite fatigue life. Schematic and Given Data: