|Shaft diameter dk: Local diameter at the
critical area (grooved section).
The ratio σe/Rp0.2=Cf·Ce/Cm
where Cf represent the influence factors
listed in eq(3.1), Ce
is the ratio of the endurance limit with the ultimate tensile
strength as listed in Table 3.1 and Cm 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.