Fatigue life assessment models under random loadings: state-of-the-art and future perspectives

The fatigue life of vibrating structures subjected to uniaxial or multiaxial random stresses can be estimated by spectral methods, which are models that exploit a frequency-domain description of the random stress by a Power Spectral Density (PSD) function. Spectral methods provide analytical expressions that allow the fatigue life to be estimated directly from PSD parameters. Over the years, several models have been proposed for uniaxial/multiaxial random stresses, being either Gaussian or non-Gaussian, stationary or non-stationary (with switching behaviour). This paper attempts to summarise the main achievements in the field, with special focus on the results obtained by the present authors. The TB method for Gaussian and non-Gaussian loading, the “Projection-by-Projection” multiaxial criterion, the model for switching loadings are some, but not all, topics addressed. The role of material fatigue properties in experimental testing is also discussed. General recommendations on the use of frequency-domain models are finally provided.