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Abstract : The formation of hot spots is an essential step in the process of initiating explosive crystals by shock or impact. Consequently, any attempt to understand the initiation of explosive crystals must first establish how the energy of the shock or impact is localized to form hot spots. More generally, it appears that energy localization occurs in all crystalline solids, both inert and energetic, when they are subjected to shock or impact induced plastic deformation. This paper is in part a review of our current research to understand the process of energy localization on a microscopic level by examining the energy dissipated by moving dislocations. Dislocation generation and motion are the fundamental mechanism of plastic deformation. The energy dissipated in the phonon field generated by moving dislocations is determined and shown to be both localized and intense. Energy dissipation rates are calculated for mild shocks and impacts. For high level shocks it is shown that direct pumping of the interna1 energy levels of the molecules near the dislocation core is possible which can produce rapid molecular dissociation. The generation of shear bands is modelled. These shear bands are formed by the accumulation of many dislocations in small regions of intense shear in the crystal and are taken to be the macroscopic sites of the hot spots.





Autor: C. Coffey

Fuente: https://hal.archives-ouvertes.fr/



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