THE NOTCH EFFECT OF GEOMETRIC STRESS RAISERS IN FATIGUE

The effect of a notch on the fatigue strength of a component varies co nsiderably with the notch geometry. An analytical method is suggested to assess the notch geometry effect on the fatigue strength reduction factor, K-f. It is shown that a proper analysis of the notch effect mu st consider the stress distribution around the notch as well as the st ress state in the neighborhood of the notch. The elastic stress distri bution around the notch is determined by employing either the Finite E lement Method or some universal relationships available in the literat ure. The biaxial state of stress is accounted for using von Mises equi valent stress which were averaged up to the cupic point position. The average von Mises equivalent stress is used to obtain the fatigue stre ngth reduction factor. A material parameter K-f/K'(t)), is introduced. A number of notch geometries in four different types of steels were a nalyzed. The K-t values of these notches ranged from 1.9 to 3.5. It is found that the method could be satisfactorily used when the material parameter dependence on the notch geometry is small. It is also found that the method performs satisfactorily for low K-t values where the n otch stress field can be considered elastic.