On stochastic evaluation of S–N data based on fatigue strength distribution

A statistical decision method for the construction of S–N curve has been proposed. In general, fatigue test results are widely scattered even in the strictly controlled conditions. Therefore, the mean S–N curves should be determined by a statistical method. In the proposed method, S–N curves are determined based on the evaluation of fatigue strength distribution. Data sets of fatigue test were combined into one group using the concept of “Equivalent fatigue strength”. The proposed method has been applied to the fatigue test data for some materials and reasonable S–N curves were obtained. The good accuracy of the proposed S–N curves is shown by comparison with the one obtained by Probit analysis. Besides, design criteria for given failure probability can be obtained easily because the proposed method evaluates the fatigue strength distribution.