DETERMINATION OF THE FATIGUE LIMIT IN THE CASE OF AN ASYMMETRICAL STRESS CYCLE,

The paper discusses the complications involved in predicting fatique life on the basis of tests or observations to establish S-N relationships. The various formulas proposed in the literature for calculating the fatigue limit under symmetric and asymmetric cyclic loading are reviewed and compared with experimental data. A convenient method is proposed for constructing a simplified maximum stress diagram and a general expression is given for the fatigue limit. A comparison between experimental data and the results given by this formula shows a divergence of 1.5-6 percent. In using thses formulas, it is sufficient to know the tensile strength of the material and the fatigue limit in the case of a symmetric stress cycle, i. e. figures which may be found in the reference literature.