Basic principles of spectral multi-axial fatigue analysis

This paper presents a discussion on multi-axial fatigue criteria for random stresses which are formulated as spectral methods in the frequency-domain. Spectral solutions to the multi-axial problem can be viewed as a natural step forward from uni-axial spectral methods. The paper attempts to identify and critically analyze some underlying principles that join together different multi-axial spectral methods. General remarks on advantages and drawbacks of multi-axial spectral methods from the literature are pointed out and commented on.