Comportement à la rupture et caractérisation mécanique des caoutchoucs cristallisants sous contrainte

Abstract : The following Ph D dissertation first objective is to develop a tractable anisotropic constitutive equation for strain induced-crystallizing rubber. This equation is developed at a microscopic level and then intergrated in a macroscopic framework in a finite element code. Finally the influence of strain induced crystallization on crack propagation is assessed using an associated energy release rate. The underlying goal of this study is to address the problem of tyres' endurance. After introducing the difficulties linked to tyres' endurance, basic notions on the mechanical framework at play are introduced in the first part. Part II deals with energy release rate calculations using domain's derivation methods. We then propose a formal extension of this kind of method to viscoplastic behaviour. A first case is treated where dissipative processes and failure mechanisms are uncoupled. This extension is then tested and validated on cases of elastoplastic computations. Another method to calculate the energy release rate in the coupled case is constructed using an adjoint state. This is then tested with a simple viscoelastic problem. The purpose of part III is to construct a constitutive equation for strain induced crystallizing rubber in a micro-sphere framework, so that it is possible to chararacterize stress strain relation, anisotropy of the local response and effects of crystallization at the crack tip. The approach is based on state-of-the-art experimental observations, with emphasis on the constitutive aspects of cyclic behaviour. The constitutive law is then compared with many experimental measurements, for a large panel of loading characteristics. It is shown that experimental data are well reproduced, especially these where cyclic loading and anisotropy evolution are at play. Finally, part IV deals with impact of crystallization on rubber failure, using the methods introduced in the two previous parts. The predicted failure profile and crystallized zone are quite similar to data retrieved from experiments. Moreover, the proposed extension of the energy release rate has been applied to a pure shear test sample where crystallization is happening. The evolution of energy release rate with loading is then compared to the evolution of crack propagation speed in fatigue.
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Submitted on : Sunday, April 13, 2014 - 7:27:36 PM
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  • HAL Id : pastel-00978212, version 1

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Joachim Guilie. Comportement à la rupture et caractérisation mécanique des caoutchoucs cristallisants sous contrainte. Mécanique des solides [physics.class-ph]. Ecole Polytechnique X, 2014. Français. ⟨pastel-00978212⟩

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