Stress Concentration for Dynamic Conditions

For dynamic loading conditions, the impact of discontinuities is not as pronounced on fatigue (dynamic) as on yield strength (static). This means that we need a different stress concentration factor, $K_f$, called the fatigue stress-concentration factor.

• For normal stress:

$$K_f=\frac{{\sigma }_{\text{max}}}{{\sigma }_0}$$

• For shear stress:

$$K_{fs}=\frac{{\tau }_{\text{max}}}{{\tau }_0}$$

The relationship between $K_t$ for static loading and $K_f$ for dynamic loading is defined by notch sensitivity, $q$.