Recent developments in frequency domain multi-axial fatigue analysis

The purpose of this paper is to discuss the recent developments in multi-axial spectral methods, used for estimating fatigue damage of multi-axial random loadings from Power Spectral Density (PSD) data. The difference between time domain and frequency domain approaches in multi-axial fatigue is first addressed, the main advantages of frequency domain approach being pointed out. The paper then critically reviews some categories of multi-axial spectral methods: approaches based on uniaxial equivalent stress (strength criteria, equivalent von Mises stress, multi-axial rainflow counting), critical plane criteria (Matake, Carpinteri-Spagnoli, criterion based on resolved shear stress on critical plane), stress invariants based criteria (Crossland, Sines, Projection-by-Projection). The maximum variance method and the Minimum Circumscribed Circle/Ellipse formulations defined in the frequency domain are also discussed. The paper critically analyses also non-proportional multi-axial loadings and the role of material fatigue parameters (e.g. S/N curves for bending/torsion) in relation to specific methods. The paper concludes with general comments on advantages and possible limitations in the use of multi-axial spectral methods, with special focus on the assumption of stationarity and Gaussianity in modelling multi-axial random loadings. (C) 2016 Elsevier Ltd. All rights reserved.