Fatigue life estimation under multiaxial random loading by means of the equivalent Lemaitre stress and multiaxial S–N curve methods

• A novel frequency domain formula of stress invariant is developed.
• Effect of hydrostatic stress on fatigue life is investigated.
• A multiaxial S–N curve is introduced.
• Both the material fatigue S–N curves for axial and torsion are used.
• The proposed method is proved to have a general good accuracy.

In this paper, the frequency domain formula of equivalent Lemaitre stress taking into account the hydrostatic stress effect is first introduced, and the corresponding method for estimating fatigue life under multiaxial random loading is developed based on multiaxial S–N curve. The proposed method is systematically validated with the random bending-torsion fatigue tests and numerical simulations. It has been shown that the hydrostatic stress has a significant influence on multiaxial fatigue life; the results predicted by the proposed method agree well with the experiment, and are more accurate than those obtained for the equivalent von Mises stress method.