In: Mechanical Engineering
Calculate the fatigue stress concentration for a steel filleted shaft that is loaded axially.
Given Data:
Sut = 690 MPa
D (for larger cross-section) = 54 mm
d (for smaller cross-section) = 40 mm
r(fillet radius) = 3 mm
Ratio of max dia to min dia, D/d = 54/40 = 1.35
Ratio of radius of fillet to min dia = r/d = 3/40 = 0.075
At D/d = 1.35 and r/d = 0.075; Kt=1.90 where Kt is the theoretical stress concentration factor. Now to consider the fatigue, we have to use the notch sensitivity formula, Kf = 1 + q(Kt-1) where Kf is the fatigue stress concentration factor and q is the notch sensitivity.Here q = 0.85 (3mm radius and 0.7GPa).
Therefore, the value of Kf = 1 + q(Kt-1) = 1 + 0.85(1.90-1). Therefore, Kf =1.765