4 Fatigue Life Prediction of Natural Rubber in Antivibratory Applications 35 Fig. 4.3 Correlation diagram obtained for the three Signals and for (a) Variant #1 (R effect not taken into account) and (b) Variant #2 (R effect taken into account) 4.6 Conclusion Contitech AVS France develops in NR-filled parts for the automotive industry. During the development process of antivibratory parts, predictive approaches are used to supplement classical experimental tests in order to validate their design. A methodology is here proposed to affine and lighten the design procedure by accounting for the effect of temperature on the fatigue behavior. At 23◦C, it is here confirmed that the material exhibits a strong lifetime reinforcement under positive loadings ratios. Furthermore, the temperature affects this phenomenon: it is lower at 90◦C and disappears at 110◦C. Beside opening numerous questions on the effect of temperature on the ability of NR to crystallize, these two results justify the need of accounting for temperature effects into predicting the fatigue life. A lifetime prediction model Rbloc has been developed and was here tested on Diabolo samples for blocs of sinus loadings. The predicted fatigue lives were within a factor two scatter band. As a next step, it would be appropriate to validate the lifetime prediction model on industrial parts, which will require to take other physical phenomena into account. Acknowledgments The authors thank the Contitech France company for supporting this work and for fruitful discussions. The authors also thank the National Center for Scientific Research (MRCT-CNRS and MI-CNRS) and Rennes Metropole for supporting this work financially. SEM images were performed at CMEBA facility (ScanMAT, University of Rennes 1), which received a financial support from the European Union (CPER-FEDER 2007–2014). References 1. Cadwell, S.M., Merrill, R.A., Sloman, C.M., Yost, F.L.: Dynamic fatigue life of rubber. Ind. Eng.Chem.Anal. Ed. 12, 19–23 (1940) 2. Trabelsi, S.: Etude statique et dynamique de la cristallisation des élastomères sous tension (2002) 3. Fielding, J.H.: Flex life and crystallisation of synthetic rubber. Ind. Eng. Chem. 35, 1259–1261 (1943) 4. Lindley, P.B.: Relation between hysteresis and the dynamic crack growth resistance of natural rubber. Int. J. Fract. 9, 449–462 (1973) 5. Treloar, L.R.G.: The Physics of Rubber Elasticity. Oxford University Press, Oxford (1975) 6. Bruening, K., Schneider, K., Roth, S.V., Heinrich, G.: Kinetics of strain-induced crystallization in natural rubber: a diffusion-controlled rate law. Polymer. 72, 52–58 (2015) 7. Albouy, P.A., Marchal, J., Rault, J.: Chain orientation in natural rubber, part I: the inverse yielding effect. Eur. Phys. J. E. 17, 247–259 (2005) 8. Candau, N., Laghmach, R., Chazeau, L., Chenal, J.-M., Gauthier, C., Biben, T., Munch, E.: Temperature dependence of strain-induced crystallization in natural rubber: on the presence of different crystallite populations. Polymer. 60, 115–124 (2015) 9. Trabelsi, S., Albouy, P.-A., Rault, J.: Stress-induced crystallization around a crack tip in natural rubber. Macromolecules. 35, 10054–10061 (2002) 10. Ruellan, B., Le Cam, J.-B., Robin, E., Jeanneau, I., Canévet, F.: Fatigue of natural rubber under different temperatures. Int. J. Fatigue. 124, 544–557 (2019)
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