Shaft diameter d_{k}: Local diameter at the
critical area (grooved section). Endurance strength
σ_{e}:
The ratio σ_{e}/R_{p0.2}=C_{f}·C_{e}/C_{m}
where C_{f} represent the influence factors
listed in eq(3.1), C_{e}
is the ratio of the endurance limit with the ultimate tensile
strength as listed in Table 3.1 and C_{m} is the ratio of
the elastic limit and the ultimate tensile strength.
Stress concentration factors: For high
strength steel grades and brittle materials the notch
sensitivity in not far from unity so Kt=Kf. For ductile
materials the lower value of the fatigue stress concentration
factor Kf can be applied. It is always save to use the
geometrical stress concentration factor Kt which based on
(numerical) calculation. Examples of how to limit the stress
concentration factor see fig 3.7 and 3.8. |