Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session 1E: Energetic Materials: Experiments, Modeling, and TheoryStudent Symposium
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Room: Anaheim Marriott Platinum 5-6 |
Sunday, July 10, 2022 11:15AM - 11:30AM |
1E.00001: Effects of reaction kinetics models on macro-scale sensitivity predictions for a wide class of energetic materials prarthana parepalli The sensitivity of heterogeneous energetic materials (HE) depends on their chemical (molecular) and physical (micro-) structure. For a wide range of energetic materials, the primary energetic components are organic CHNO crystals. The overall macroscopic sensitivity of HEs depends on a complex coupling of the molecular reaction chemistry and microstructural dynamics, due to the localization of energy at hotspots in the microstructure. Reactions triggered at hotspots advance into the unreacted sample, leading to shock-to-detonation (SDT) scenarios. In this work, we perform multi-scale simulations to investigate the effect of uncertainties in the chemical kinetics parameters for the decomposition of the HE material on the rate of deposition of energy at the macro-scale. Ensembles of high-resolution reactive void collapse simulations are performed by varying the global Arrhenius parameters (representing a wide class of HE materials, ranging from insensitive TATB to highly sensitive PETN) to construct meso-informed surrogate models for energy localization. Then macro-scale computations of shock-to-detonation transition are performed using the meso-informed Ignition and Growth (MES-IG) model. The performance of the HE at the macro-scale is evaluated via the critical energy required for initiation in the Walker-Wasley/James space. The predicted critical energy envelopes are compared with experimental data. The results quantify the effects of uncertainties in the chemical kinetics parameters on the macro-scale sensitivity predictions. This study will guide the development of reaction kinetics models to reliably predict macro-scale sensitivity of a wide range of CHNO materials. |
Sunday, July 10, 2022 11:30AM - 11:45AM |
1E.00002: SDT Behavior of Functionally Graded Energetic Materials (FGEM) Daniel H Olsen The behavior of energetic materials is significantly influenced by the spatial distributions of microstructure heterogeneities and voids. We propose the concept of Functionally Graded Energetic Materials (FGEM) whose microstructure features (grain size, grain volume fraction, void size, and void volume fraction) change spatially such that they may allow the behavior of the materials to be tailored. Here, we use gradients in the density of voids to alter the detonation behavior of a polymer-bonded explosive with attributes echoing those of PBX9501. Three-dimensional mesoscale simulations are carried out. Microstructures are designed to have different void densities and void density gradients. The analyses focus on the shock-to-detonation transition (SDT) behavior and the run distance. Four cases with different graded microstructures are considered. An HVRB model is used to account for the decomposition of the HMX crystals. The calculations show that the gradient of the void density significantly affects the run distance, the propagation of the shock and reaction fronts, and the rate at which the SDT transition is achieved. Overall, the findings point out that microstructure feature gradients can be viable variable for manipulating the behavior of energetic materials. |
Sunday, July 10, 2022 11:45AM - 12:00PM |
1E.00003: Melt Curves of RDX and HMX Computed by Molecular Simulation Garrett M Tow In this talk, we show how the solid–liquid coexistence curves of classical fully flexible atomistic models of α-RDX and β-HMX can be calculated using thermodynamically rigorous methodologies that identify where the free energy difference between the phases is zero. The free energy difference between each phase at a given state point was computed using the pseudosupercritical path (PSCP) method, and Gibbs–Helmholtz integration was used to evaluate the solid–liquid free energy difference as a function of temperature. This procedure was repeated for several pressures to determine points along the coexistence curve. While effective, this method is computationally expensive. To trace out the coexistence curve in a more computationally economical manner, Gibbs–Duhem integration was used starting from a coexistence point determined by the PSCP method. For α-RDX, the predicted melting temperature increases significantly more for a given increase in pressure when compared to available experimental data. |
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