Different Fatigue Dynamics Under Statistically and Spectrally Similar Deterministic and Stochastic Excitations

Estimating and tracking crack growth dynamics is essential for fatigue failure prediction. A new experimental system— coupling structural and crack growth dynamics—was used to show fatigue damage accumulation is different under chaotic (i.e., deterministic) and stochastic (i.e., random) loading, even when both excitations possess the same spectral and statistical signatures. Furthermore, the conventional rain-flow counting method considerably overestimates damage in case of chaotic forcing. Important nonlinear loading characteristics, which can explain the observed discrepancies, are identified and suggested to be included as loading parameters in new macroscopic fatigue models.