The Reliability Calculation of Components Under Any Cyclic Fatigue Loading Spectrum

The fatigue failure of metal components is due to cyclic fatigue loading. The typical cyclic fatigue loading spectrums described in the literature includes only a few simple cyclic loadings such as a constant amplitude of cyclic fatigue loading with a given cycle number, several constant amplitudes of cyclic fatigue loadings with given cycle numbers, and a distributed stress amplitude of a cyclic stress with a given cycle number or an infinite life. The systematic description of cyclic fatigue loading spectrums is necessary and wasn’t presented in the literature. This paper will present a systematic description of all possible types of cyclic fatigue loading spectrums, which includes 6 different cyclic fatigue loading spectrum models. The P-S-N curve fatigue theory is widely accepted not only for describing the fatigue test data, but also for estimating the reliability of components under cyclic fatigue loading spectrum. However, the reliability calculation of a component under several distributed stress levels with corresponding given cyclic numbers has not been solved according to the literature review. This paper presents a new approach to estimate the reliability of components under such cyclic fatigue loading spectrum. With the contribution of this paper, the P-S-N curve fatigue theory now becomes a complete fatigue reliability theory and can be used to estimate the reliability of components under any type of cyclic fatigue loading spectrum.