Fatigue lifetime of welded joints under random loading: rainflow cycle vs. cycle sequence method

The evaluation of fatigue lifetime is a complex problem due to the loading cycle sequence effect influencing the fatigue damage process. In the literature two different approaches are usually adopted to solve the fatigue crack growth under time varying loading: the rainflow cycle (RFC) and the cycle sequence (CSQ) model. In this paper the performance of the recently proposed stochastic version of these methods is compared and applied to the evaluation of the fatigue lifetime of the welded cruciform tested in the literature. Non-Gaussianity and bandwidth effect are correctly captured by both methods but only the CSQ model enables us to examine the influence of the load sequence effect on the fatigue lifetime. Numerical results show that the retardation effect can be neglected for Gaussian and non-Gaussian loading as the bandwidth increases. Finally, this work shows the greater performance and flexibility of the CSQ model compared to the RFC model.