The circular shaft is loaded in four-point bending, which produces a constant bending moment M over the central region. The shaft is rotating so that the stresses alternate from a tension peak to a compression peak. A groove with a radius r = 10 mm is cut about the circumference of the shaft at the midspan point, and the two diameters are D = 105 mm and d = 100 mm. The shaft is made from steel which has an endurance limit of 234 MPa. Calculate the stress concentration factor for this geometry and the largest bending moment M, if the shaft is designed to never fail in fatigue. Round the stress concentration factor K that you find to the nearest tenth and use this rounded number when performing all subsequent calculations. K = M = M D kN m d ? M