Verification of a stress gradient theory for the fatigue life predicition of components in case of pure push-pull and pure torsion conditions

A relevant number of theories has been proposed in the last 50 years for calculation of the fatigue limits of components containing notches or more general geometrical discontinuities. Beyond the most classical ones, some methods correlate the life to the relative stress gradient, allowing to overcome the limits of the factors Kt and Kf not definable for generally complex shaped components. On this direction, a recent and very promising formulation has been proposed [11,12] to predict the local S/N curve on the base of a Finite Elements Analysis of the stress gradient and on an empirical formulation of the support factor nx.Aim of the present study is to validate the present theory in the case of shafts in pure torsion and in push-pull, comparing the predicted values with experimental data obtained in two different test campaigns.