Fatigue Life Prediction of Natural Rubber in Antivibratory Applications

Natural Rubber (NR) is the most commonly used elastomer in the automotive industry, thanks to its outstanding fatigue resistance. Typically, NR exhibits a lifetime reinforcement under non-relaxing loadings (Cadwell SM, Merrill RA, Sloman CM, Yost FL, Ind Eng Chem Anal Ed 12:19–23, 1940). Antivibratory parts are generally made of carbon black–filled NR. Experimental tests are generally carried out in order to check their resistance to fatigue loading, which requires a lot of resources (human presence, time, and money). This is the reason why in the last two decades, predictive approaches were developed to supplement the experimental tests and lighten the development procedure. However, all the physical phenomena, especially the effect of temperature on the fatigue life (B. Ruellan, J.-B. Le Cam, E. Robin, I. Jeanneau and F. Canevet, “Fatigue of natural rubber under different temperatures,” Interational Journal of Fatigue, vol. 124, pp. 544–557, 2019), are not well taken into account, which explains why the mass of the rubber part and the material formulation remain not optimized. Therefore, it is here proposed to improve the prediction methodology by accounting for the effect of temperature in the fatigue behavior of NR, especially for loadings where a fatigue reinforcement due to strain-induced crystallization is observed. A lifetime prediction model has been developed and results of fatigue life predictions are proposed in the case of variable amplitude loadings. Results are found satisfactory, which enables Contitech AVS France better designing rubber parts by more accurately predicting their fatigue life and perfecting their design.