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Etude expérimentale et numérique de la sensibilité de compositions énergétiques ˸ influence de la microstructure et rôle de l'endommagement

Abstract : Shock sensitivity of explosive formulations is linked to their microstructure. Shock waves interact with the heterogeneitiesof the microstructure which lead to localized increase of pressure and temperature called hot spots. The hot spots can potentially initiate the detonation. The objective of the PhD thesis is to study the influence of different microstructural parameters on the sensitivity to shock of energetic materials. First, the micro-computed tomography images of three RDX/Wax materials (70/30 in weight) are studied. These three materials have the same composition but different microstructures and different sensitivity to shock. The micro-computed tomography images are filtered, segmented and characterized. The characterization allows the identification and quantification of the differences between the three materials: granulometry, spatial distribution, grains shape, contact points between grains and elastic response to deformation. Then, each labeled grain is extracted and characterized with several descriptors (volume, surface, mean radius, sphericity, angularity) to create a library of grains. The results of image analysis are compared with experimental data to evaluate the effectiveness of the segmentation tool. Then, virtual microstructures are generated with the library of grains. It allows to control the characteristics of the grains implanted in the virtual material and to isolate the effects of some microstructural parameters, while respecting the particle size and spatial distribution of the real material. Dynamic numerical simulations have demonstrated the importance of the intra-granular defects and of the contact points between the grains in the localization of stresses and the formation of hotspots. The role of the contact points between the grains was already highlighted in FFT elastic quasi-static simulations. In addition to this numerical work, shock recovery experiments were developed and performed at the ISL. Damaged RDX/Wax samples were imaged with micro-computed tomography. The first visual inspections reveal numerous cracks in the grains and an important grain-wax decohesion for shock pressure largely under the detonation threshold.
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Submitted on : Friday, December 17, 2021 - 10:40:12 AM
Last modification on : Sunday, December 19, 2021 - 3:04:46 AM
Long-term archiving on: : Friday, March 18, 2022 - 6:43:13 PM

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  • HAL Id : tel-03485254, version 1

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Elodie Kaeshammer. Etude expérimentale et numérique de la sensibilité de compositions énergétiques ˸ influence de la microstructure et rôle de l'endommagement. Traitement du signal et de l'image [eess.SP]. Université Paris sciences et lettres, 2021. Français. ⟨NNT : 2021UPSLM034⟩. ⟨tel-03485254⟩

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