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Phase field modelling of fracture of elastic and elasto-viscoplastic solid materials

Abstract : The Phase-Field Method (PFM), which has been designed for interfacial problems, provides an attractive framework for the modelling of fracture. The present work aims at developing some constitutive models within the framework of the PFM to model fracture in homogeneous and polycrystalline materials. For this purpose, two different situations have been examined. For the first situation, which is typical of brittle fracture, the development of damage is driven by the accumulation of elastic strain energy. The second situation is the one where damage is controlled by the development of plastic strains, which is quite common for ductile or fatigue fracture.The phase-field model for brittle fracture uses a scalar damage variable to represent the progressive degradation of mechanical resistance. The spatial gradient of the damage variable, which is treated as an additional external state variable, serves regularization purposes and allows considering the surface energy associated with cracks. The deviatoric/spherical decomposition of elastic strain energy is used to consider closure effects. Some material parameters have been introduced to control the impact of deviatoric and spherical contributions on the development of damage. Also, the proposed strategy is adapted to any class of material symmetry. Numerical implementation is undertaken via the finite element method, where nodal degrees of freedom are the displacement and the damage variable. For illustration purpose, the numerical simulations are carried out under both static and dynamic loading conditions.An extension of the above model to plasticity-driven fracture in polycrystalline materials is also proposed. The framework of crystal plasticity has been used for the construction of constitutive relations. To consider the role of plastic strains on the development of damage, the proposed strategy uses the coupling between damage and hardening. The consequence is that the driving force for damage contains some contributions from isotropic and kinematic hardening variables. According to the numerical results, the important features of ductile and fatigue fracture are correctly reproduced.
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https://pastel.archives-ouvertes.fr/tel-03026401
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Submitted on : Thursday, November 26, 2020 - 4:31:12 PM
Last modification on : Friday, November 27, 2020 - 3:24:26 AM

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  • HAL Id : tel-03026401, version 1

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Hela Gmati. Phase field modelling of fracture of elastic and elasto-viscoplastic solid materials. Mechanics of materials [physics.class-ph]. HESAM Université, 2020. English. ⟨NNT : 2020HESAE010⟩. ⟨tel-03026401⟩

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