Fatigue notch sensitivity (q)

The degree to which a material's fatigue strength is sensitive to a notch (stress concentrator).

\begin{align} \label{eq:15001a} q = \frac{K_f - 1}{K_t - 1} \end{align}

where —

\( K_f \)	= fatigue stress concentration factor
\( K_t \)	= theoretical (static) stress concentration factor

q ranges between 0 (i.e., no effect on fatigue strength when \( K_f \) = 1) to 1 (i.e., full sensitivity when \( K_f \) = \( K_t \)).

See Campbell[1], p. 257 (also Juvinall[1], p. 254).