An extended model for fatigue life prediction and acceleration considering load frequency effect

With consideration of the load frequency effect of constant-amplitude fatigue test, a fatigue acceleration technique is developed in this paper. Load frequency shows effects on both macroscopic mechanical properties and microscopic deformation behaviors of material. Thus it is necessary to take the load frequency effects into consideration in the fatigue life prediction models. In this paper, an extended model based on the S-N approach is proposed to consider the frequency effect. Fatigue life is predicted with a heteroscedastic method, and then the acceleration by increasing load frequency and stress amplitude is studied. The presented model is also validated by a comparison between the theoretical prediction and experimental results. It is shown that the presented model is consequential in improving the S-N curves obtained under various load frequencies. In addition, load frequency increasing can lead to effective acceleration although the retardant effect is also triggered due to the increase of deformation resistance.