A unified probabilistic fatigue life prediction model for natural rubber components considering strain ratio effect

The fatigue life of natural rubber (NR) components under a constant-amplitude load is dispersed. The dispersion can be reflected by establishing a probabilistic fatigue life prediction model (also called the P-S-N curve). However, the effect of strain ratio on fatigue life is typically ignored in conventional P-S-N curves. Aiming at improving the prediction accuracy of conventional models, a unified P-S-N curve for NR components is proposed in the present study, in which the strain ratio effect is considered in the calculations. Using the dumbbell-shaped rubber specimen fatigue test data, a polynomial function is proposed to describe the correlation between the equivalent strain amplitude, strain amplitude, and strain ratio. Then a calculation model of equivalent strain amplitude is established. Furthermore, a unified P-S-N curve for NR is established with equivalent strain amplitude as the damage parameter. By comparing the measured and predicted fatigue life of NR under different reliabilities, the accuracy of the established unified P-S-N curve is verified.