An invariant-based approach for high-cycle fatigue calculation

Fatigue failures of in-service components are frequently due to multiaxial loadings, therefore damage quantification in such conditions is important to many industrial applications. In this work a multiaxial criterion suitable for high-cycle fatigue assessment is formalised. It makes use of hydrostatic stress component and deviatoric stress component to estimate fatigue damage. A new formulation for the equivalent amplitude of the deviatoric component is formalised and compared with definitions proposed by Deperrois and Li and De Freitas. Damage evaluation procedure is discussed for deterministic loads and explicit analytical formulation is presented for sinusoidal loadings. Fatigue criterion is applied to experimental data taken from literature, related to several materials subjected to either in-phase or out-of-phase loads. It is showed that the new approach gives good predictions for both smooth and notched specimens. A similar comparison between experimental and theoretical results is also presented for other common criteria. It appears that the quality of the fatigue assessments obtained with the present criterion is better or, at most, similar to that of the other criteria analysed.