An elastic/viscoplastic pore collapse model of double-layered hollow sphere for hot-spot ignition in shocked explosives

An elastic/viscoplastic pore collapse model of double-layered hollow sphere, in which the effect of the binder in Plastic Bonded Explosives (PBX) was taken into account, was developed as a hot-spot ignition model in shocked explosives. The space and time distributions of the velocity, strain, temperature and chemical reaction rate in shock compression of the explosive hollow sphere were theoretically calculated. A new expression of reaction rate equation was obtained for the hot-spot ignition. The three-term reaction rate model, consisting of the new hot-spot ignition term, the slow burning term at low-pressure from Kim and the high-pressure reaction term from ZHANG Zhen-Yu, was implemented into the two-dimensional, hydrodynamic finite-element code DYNA2D and used to simulate the one-dimensional shock initiation process of PBX-9501 explosive. The numerical results show that the model can successfully explain the influence of strength and content of the binder in PBX on the shock initiation, and that of particle size and porosity as well.