Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session H1: DSIC: Shock-to-detonation Transition |
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Chair: Ryan Wixom, SNL Room: Grand Ballroom I |
Tuesday, June 18, 2019 9:15AM - 9:30AM |
H1.00001: Carbon condensation subsequent to ultrafast compression of cryogenic liquid CO Michael Armstrong, Rebecca Lindsey, Nir Goldman, Michael Nielsen, Elissaios Stavrou, Joseph Zaug, Sorin Bastea Self-propagating shocks (detonations) in most organic negative oxygen balance explosives produce "soot" in the form of nanocarbon polymorphs. The formation of carbon condensates is of fundamental importance to detonation chemistry, and this process may occur on sub-ns time scales. To investigate carbon condensation in a chemically reacting environment, we present results of ultrafast shock experiments in cryogenic liquid CO in a modified, commercial cryostat. Ultrafast (100s ps to 1 ns) duration experiments have the capability to resolve very fast condensation processes, have high throughput, and can be more directly compared to simulations. Using sub-ns shock compression, we observe shocked states consistent with long time scale gas gun experiments, and evidence of the formation of carbon condensates over a \textasciitilde 50 ps time scale at shock pressures above around 16 GPa. These results compare well to DFT force-matched molecular mechanics simulations, which predict carbon nanoparticle formation in the 10s nm range, consistent with nanocarbon agglomerates recovered from the experiment and in situ optical transmission measurements. [Preview Abstract] |
Tuesday, June 18, 2019 9:30AM - 9:45AM |
H1.00002: Shock initiation of Cyclotol (75/25) at both ambient temperature and 70 \textordmasculine C Malcolm Burns, Justin Jones, Andrew Houlton, Brian Bartram Six shock initiation experiments have been carried out to study the shock sensitivity and develop the unreacted Hugoniot for the Cyclotol composition 75{\%}wt RDX, 25{\%}wt TNT. The experiments were carried out both at ambient temperature, and elevated to 70 \textdegree C, close to the TNT melt temperature of 80 \textdegree C. Two sets experiments were fired at pressures of 4.1, 6.4 and 7.7 GPa. The experiments were performed using the single and two-stage gas guns at the Los Alamos National Laboratory. Embedded gauges were used to capture eleven Lagrangian positions producing particle velocity profiles and a measurement of the run-to-detonation coordinates. Comparison has been made to the previously studied (80{\%}wt RDX, 20{\%}wt TNT) composition and analysis shows that the decrease in RDX content has resulted in a significant increase in shock sensitivity. This could be due to the 0.7 {\%} reduction in pressing density of the explosive studied in this work, resulting in an increase of void fraction from 1.7{\%} to 2.0{\%}. The increase in initial temperature, from ambient, has yielded a small increase in shock sensitivity, however this is small in comparison to the change in sensitivity due to the composition change. Wave profiles will be presented, along with a discussion of the unreacted Hugoniot and relative sensitivities presented in the Pop plot. [Preview Abstract] |
Tuesday, June 18, 2019 9:45AM - 10:00AM |
H1.00003: Predicting the effects of thermally-induced density gradients on the hydrodynamic behavior of PBX 9502 John Yeager, Lee Perry, Amanda Duque, Xia Ma, Genevieve Watt High explosive charges are nominally uniform density but can develop density gradients if they are asymmetrically heated. Here, we investigate the effects of these thermally-induced density gradients on the shock-to-detonation transition and resulting detonation wave shape in the explosive PBX 9502. Our newly developed approach combines results from COMSOL Multiphysics software with the reactive burn model within the SURF hydrodynamic simulation code. We first used COMSOL to model charges of PBX 9502 with several thermal boundary conditions of varying asymmetry, generating maps of the final temperature, density and deformation. This resulted in spatially varying density as well as differences in the density gradients when different boundary conditions were applied. The data were then binned into domains of average density, partitioned by constant density contours. Appropriate temperature- and density-dependent PBX 9502 SURF burn model constants were assigned to each region and deployed within the hydrocode to predict the shock-to-detonation transition behavior and wave shape in the part. The simulations revealed that detonation propagation and wave shape could both be controlled by choosing a desired density gradient. [Preview Abstract] |
Tuesday, June 18, 2019 10:00AM - 10:15AM |
H1.00004: Commonalities in the Shock-to-Detonation-Transition Acceleration Profiles for PBX 9502 Scott Jackson The detonation reaction rate constitutes a key element of reactive models for high explosive prediction, yet there is uncertainty as to the best analytical representation of this relationship due to experimental measurement limitations in reacting high explosive flows. This work analyzes the velocity versus time profiles of a high explosive, PBX 9502, undergoing shock to detonation transition. A common acceleration profile is seen across multiple experiments with different initial shock loading conditions. The trend exhibits features consistent with both Arrhenius reaction rate forms at lower velocities and pressure-dependent burn rate forms at higher velocities approaching detonation. The overall trend is most qualitatively consistent with a stretched exponential form and appears to to exhibit some dependence on the initial shock strength condition. [Preview Abstract] |
Tuesday, June 18, 2019 10:15AM - 10:30AM |
H1.00005: A Volumetric Approach to Shock Initiation of Triaminotrinitrobenzene (TATB) Mike Bowden A volumetric shock initiation criterion, based on the concept of a critical shock volume as a function of shock pressure, has been shown to describe historic data on shock initiation of PBX9404 by thick, planar flyers, rods, and round-nosed projectiles, along with recent data on shock initiation of hexanitrostilbene (HNS) and pentaerythritol tetranitrate (PETN) by thin, curved flyers, which criterion based upon a shock duration cannot describe as completely. This criterion has been applied to historic data on shock initiation by flyer plates of triaminotrinitrobenzene (TATB), specifically PBX 9502, LX-17 and ultrafine TATB. The volumetric shock initiation criterion is shown to fit the data well, and highlights differences in sensitivity between the three materials. A comparison is made between the volumetric shock sensitivity of sensitive materials, such as PETN, less sensitive materials, such as HMX, and insensitive materials, such as TATB, where the required shocked volume for initiation spans almost six orders of magnitude. [Preview Abstract] |
Tuesday, June 18, 2019 10:30AM - 10:45AM |
H1.00006: Experimental characterization of the shock to detonation transition in TX1 HMX-TATB based explosive using embedded electromagnetic particle velocity gauges Arnaud Sollier, Philippe Hebert, Roland Letremy, Vincent Mineau, Xavier Boissy, Eric Pionneau, Michel Doucet, Eric Bouton We have completed a series of 1-D single shock and double shock initiation experiments on TX1 (45 wt \% HMX, 52 wt \% TATB, 3 wt \% binder). These experiments were performed on the 60 mm bore powder gun located at CEA Le Ripault. Samples were prepared with eleven embedded electromagnetic particle velocity gauges to measure the evolution of the wave leading up to a detonation. Additionally, three shock tracker gauges were used to track the position of the shock front with time and determine the point where detonation was achieved. Particle velocity wave profiles are characterized by a small amount of growth in the shock front and a growing following wave behind the shock front, which is common to all HMX based explosives. Run distances and times to detonation as a function of initial pressure are consistent with published data on EDC-37, which is the less sensitive HMX based explosive due to its very low void content. All these results demonstrate that the reactivity of TX1 is mainly driven by HMX, despite a higher content of TATB. [Preview Abstract] |
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