Multiaxial fatigue analysis is crucial in the design and durability assessment of structural components across many engineering areas such as automotive, aerospace, and railway. Among the methods used for the fatigue assessment, Critical Plane approaches, particularly the Fatemi-Socie criterion, are highly effective in identifying critical locations and crack propagation directions for a large variety of structural materials [1]. While this criterion has been extensively validated in the time domain for both proportional and non-proportional loading conditions, its application to multiaxial random loading, especially in the frequency domain, has remained limited. This study presents a novel and refined formulation of the Fatemi-Socie CP method, adapted for the frequency domain. This approach offers a computationally efficient solution for analyzing fatigue under complex random loadings. The frequency-domain method reinterprets the necessary parameters for calculating the Fatemi-Socie CP factor, utilizing power spectral density (PSD) functions to address the stochastic nature of real-world loading scenarios. A new algorithm for identifying critical planes is introduced by leveraging the covariance matrix, ensuring rapid screening and subsequent detailed analysis on a reduced set of candidate planes. A comparative analysis between the time and frequency domain results highlights the accuracy and reliability of the proposed approach. The findings confirm that the fatigue life predictions in both domains are closely aligned, reinforcing the robustness of the Fatemi-Socie criterion when adapted to the frequency domain.

References

[1] Fatemi, A. and Socie, D.F. (1988), A critical plane approach to multiaxial fatigue damage including out-of-phase loading. Fatigue & Fracture of Engineering Materials & Structures, 11: 149-165.

Keywords: Fatemi-Socie criterion, critical plane method, multiaxial random loading, frequency domain, fatigue analysis.