Thermal response of hyperelastic materials under cyclic loading conditions: specificities and consequences for fatigue
Résumé
The present paper deals with the specificities of the thermal response of rubber-like materials under mechanical cyclic loading at constant ambient temperature. For this purpose, the framework of thermo-hyper-elasticity is used to predict the heat sources produced or absorbed by the material during stretching due to the entropic coupling. The heat diffusion equation is then used to deduce the temperature variations under non-adiabatic conditions. The influence of several parameters is studied: signal shape, minimum and maximum stretch levels and multiaxiality of the mechanical state. Results show that, in the steady-state regime, the mean value between the maximum and minimum temperature variations over a mechanical cycle is different from zero. This is due to the fact that the heat source depends on both the stretch rate and the stretch level. This result leads to an important consequence for fatigue. Indeed, the stabilized mean value between the maximum and minimum temperature variations during fatigue tests does not reflect only fatigue damage, since the entropic coupling leads also to a value different from zero. This is a major difference with materials exhibiting only an isentropic coupling, for instance metallic materials.
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