| Propagation of weak shock waves (;In order to model the shock initiation process for these aggregate, reactive materials, a reliable simulation of shock propagation prior to initiation is essential. In preliminary results presented here, a finite-difference numerical scheme for two-phase flow (solid, gas) is used to model the behavior of weakly shocked granular material. The two-phase conservation equations are solved in addition to the equations of state for the solid and gas phases. The solid phase compressibility is modeled by a Mie-Gruneisen state equation. Quasi-static compaction data for the solid/gas mixture are used to couple the compressibility of the individual grains with the bulk compaction behavior of the granular bed. Predicted values for unreacted shock velocity, density and pressure are compared with experimental results for the three classes of a high-energy crystalline substance. The comparisons include a variety of shock impact conditions ranging from 20 to 100 MPa.;The capabilities of the model are then expanded to include: dynamic pore collapse at grain boundaries, hot spot initiation and release of chemical energy, and more exact constitutive relations for interphase transport of mass, momentum, and energy. A key feature of the work is coupling the bulk compressive shock energy with the resulting thermal energy of the localized hot spots (initiation sites). To model hot spot formation, a viscoplastic pore collapse model is introduced. Limited experimental data for shock velocity and particle velocity are available to verify various aspects of the model. |
