This paper deals with a thermoviscoelastic model and its analysis. The mechanical formulation is based on the generalization to large strain of the Poynting-Thomson rheological model. The heat transfers are governed by the classical heat equation and the Fourier law. We briefly expose the finite element formulation, which takes into account the quasi-incompressibility constraint for the mechanical approach. The influence of several parameters is examined.
IntroductionNowadays, elastomers are frequently employed in many sectors such as automobile and aeronautics industries. In their uses, these materials can undergo strong mechanical and thermal loadings. Moreover their mechanical properties highly depend on the temperature and thus the prediction of the behaviour and the assessment of the fatigue strength require a local analysis based on a formulation of thermomechanical models.The behavior of an elastomer can be very different according to:• the temperature, • the degree of crosslinking, • the incorporated particles (carbon black or silicium filled rubbers) • . . . So we can distinguish several approaches in the literature in accordance with the considered phenomenon:• hyperelasticity modeling the static behaviour of the material, • continuum damage mechanics approaching the softening behaviour under deformation, currently call Mullins' effect [28], • nonlinear viscoelasticity for the simulation of the relaxation phenomenon and the eventual dissipation, • thermomechanical coupling to take temperature sensitivity of mechanical characteristics into account and to describe the temperature changes due to the mechanical dissipation.More precisely, for hyperelasticity several stress strain relationships are proposed which are based on the expression of strain energy density in the isotropic, incompressible materials or very nearly so (almost incompressible). Among these behaviour laws, statistical models were carried out with entropic consideration of the molecular chains configurations [38,39], an other way consists in a phenomenological approach deduced from isotropy and incompressibility. These last ones must be adjusted according to experiment [12,26,31,32].Rubber materials, especially carbon black-filled, present a softening effect experimentally observed [13]. This loss of stiffness can be micro-mechanically described by a local separation of the carbon and rubber.* Corresponding