P–S–N Curve Fitting Method Based on Sample Aggregation Principle

Fatigue life tests play a central role in the design of mechanical systems, as the structural reliability estimation depends heavily on the fatigue strength of material, which need to be determined by experiments. The classical statistical analysis, however, can lead to results of limited usefulness when the number of specimens on test is small. Instead, this approach can potentially give more accurate estimates by applying the overall sample at each stress level. For the case of lognormal distribution, equivalent conversion of fatigue life is presented first. Then, P–S–N curve parameters are obtained based on sample aggregation principle. Furthermore, simulation test and experimental test are conducted to validate the proposed method, respectively, demonstrating that this method can sensibly outperform conventional ones. Finally, determination of minimum number of specimens in fatigue testing is presented, which can obtain P–S–N curves with a certain accuracy.