A critical plane fatigue model applied to out-of-phase bending and torsion load conditions

This paper presents an easy to handle but efficient fatigue life prediction method based on a plasticity analysis carried out at the scale of the grains, i.e. the mesoscopic scale. The different steps of the model are described in the case of in-phase as well as out-of-phase bending-torsion load conditions. One striking feature of this method is that the definition of the critical material plane and the estimation of the number of cycles to initiation are made by means of analytical expressions that are functions of the loading parameters such as amplitudes, means and phase angles. The identification of the model parameters is readily carried out by means of one SN curve and two fatigue limits. This model is able to reflect the influence of the phase shift on damage accumulation with the introduction of no adjustable parameters. Furthermore, the comparison between the predictions and in-phase and out-of-phase fatigue data found in the literature leads to very good correlation.