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Prédiction de la microfissuration par champ de phase et méthode FFT pour les matériaux énergétiques comprimés

Abstract : This work presents a study in non-linear mechanics, in the classical framework of brittle fracture in heterogeneous media. We study numerically the localization and propagation of damage in a triamino-trinitrobenzene-based (TATB) material under various mechanical and thermal loadings. The polycrystalline microstructure, which in addition contains a binder and porosities, is partially characterized by electron microscopy images as well as experimental testings under mechanical and thermal solicitations, and presents in its initial state, residual stresses and, possibly, pre-existing cracks. We first develop a numerical method based on fast Fourier transforms for predicting the material's brittle response. A "phase field" is used to describe local damage within the microstructure. The proposed algorithms, validated by comparisons with data obtained in the literature, takes into account the irreversible nature of damage as well as the strong crystal anisotropy in TATB grains, in elasticity and tenacity. Secondly, we apply the developed numerical schemes to the study of TATB polycrystals. We focus first on transgranular cracking under a cooling-heating thermal cycle, after which the role of the porosity and of the binder as well as purely-mechanical loadings are investigated. These various phenomena are taken into account incrementally and identified by an inverse method using available experimental data. The results obtained in the present work show the preponderant role played by inter and transgranular cracks on the thermal behavior under thermal and mechanical loadings. Moreover our approach also quantifies the relative influence of various mechanisms : porosity, binder and grains elasticity, but also the grains mechanical anisotropy and pre-existing cracks in the material in its initial state.
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Submitted on : Monday, September 27, 2021 - 1:03:20 AM
Last modification on : Tuesday, September 28, 2021 - 3:13:24 AM

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François Rabette. Prédiction de la microfissuration par champ de phase et méthode FFT pour les matériaux énergétiques comprimés. Physique [physics]. Université Paris sciences et lettres, 2021. Français. ⟨NNT : 2021UPSLM009⟩. ⟨tel-03354946⟩

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