Fatigue life estimation of structures under statistically and spectrally similar variable amplitude loading

Abstract

A new fatigue life prediction framework provides an improved life prediction under statistically and spectrally similar irregular variable-amplitude loading for a notched beam model. It enables the cumulative damage rule to account for the load sequence effects by modifying the probability density function of the stress-amplitude history through (1) identification of overloads based on the rainflow-counting algorithm; (2) analytical characterization of the overload retardation effects; and (3) correction to the damage rule using overload amplitude rate characterization. The fatigue lives estimated from experimentally acquired and synthetically generated load-time histories are compared to the ones generated from simulations that qualitatively reproduce the fatigue lives in physical experiments. The notable improvement in prediction accuracy outperforms the Palmgren–Miner’s rule and power-spectrum-based life estimation. The demonstrated application to the field acceleration data substantiates its use for in-service structural health monitoring and damage prognosis. This framework does not require a priory knowledge of the applied load, and it can be applied to other engineered structures with known structural and defect properties.