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Glossary

Fatigue Notch Factor (K_f)

Experiments have shown that the effect of small notches is less than that estimated from the traditional stress concentration factor, K_t. The fatigue notch factor, K_f, can be thought of as the effective stress concentration in fatigue. It depends on the size of the stress concentration and the material. Small stress concentrations are more effective in high strength materials. This effect is dealt with using a notch sensitivity factor, q.

K_f = 1 + (K_t - 1)q

The notch sensitivity factor q is an empirically determined constant that depends on the notch radius and material strength.