# 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).