Long-Life Notch Strength Reduction Due to Local Biaxial State of Stress

An explanation for the observed difference between the values of the long-life, fatigue-notch strength-reduction factor (K_f) and the elastic stress concentration factor based on the influence of biaxial-notch root stresses is presented for a limited class of problems for which the local stresses are elastic. Results of three-dimensional linear elasticity solutions for notch stresses are reviewed and then used in conjunction with a biaxial fatigue criterion suitable for elastic straining to predict values of K_f for a variety of notched components for which values have been experimentally determined. Comparison of actual and predicted values of K_f indicates a close correspondence suggesting that the influence of local biaxial stresses on the life to crack initiation of notched components is responsible for the reduced notch severity observed in many of the experimental investigations of long-life (fatigue) notch sensitivity.