Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session H2: Energetic Materials III |
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Chair: Bryan Henson, Los Alamos National Laboratory Room: Grand Ballroom IV-V |
Tuesday, June 28, 2011 9:15AM - 9:30AM |
H2.00001: Radiography of the pre-ignition thermal decomposition of Energetic Materials Laura Smilowitz, Bryan Henson, Jerry Romero, David Oschwald We have designed a small scale radiography experiment to image the density evolution of energetic materials during heating to ignition. The signal to noise of the system allows for sensitivity on the order of 1{\%} change in density. We have used this apparatus to study the density evolution in several different HMX and RDX based formulations and can watch phase transitions and material flow. During the final seconds leading up to the ignition event, the loss of solid density can be observed. A summary of results to date will be presented. [Preview Abstract] |
Tuesday, June 28, 2011 9:30AM - 9:45AM |
H2.00002: Improving the Model Fidelity for the Mechanical Response in a Thermal Cookoff of HMX Albert Nichols Understanding the response of energetic materials to adverse thermal environments is necessary to have confidence in the safety those systems. In the past few years we have been improving our thermal-mechanical-chemical modeling of HMX-VitonA based systems. Time to event predictions are very good, to within a degree of the experimental result. However, the chemical network/reaction rates are under constrained, and many networks can achieve the same level of accuracy. Recently, we have significantly improved the mechanical response modeling by the inclusion of porosity and surface tension in the solid species in the reaction network. We discuss the addition of the reversible sublimation/vaporization reactions to the reaction network. This reaction provides a non-reactive pathway yielding mass loss in the lower temperature region in TGA experiments. This implies that a lower decomposition rate can achieve the same overall level of mass loss, thus reducing the gas pressurization in the models of experiments like the Scaled Thermal Explosion eXperiemt. [Preview Abstract] |
Tuesday, June 28, 2011 9:45AM - 10:00AM |
H2.00003: A comparison of deflagration rates, at elevated pressures and temperatures, with thermal explosion results Elizabeth Glascoe, H. Keo Springer, Joseph W. Tringe, Jon L. Maienschein Previously, the deflagration rate and behavior of HMX-based explosives have been correlated with the violence of thermal explosion experiments. In particular, HMX materials that experience deconsolidative burning at elevated pressures (i.e. P = 200 - 600 MPa) also produce significantly more violent thermal explosions. Recently, we have measured the deflagration rates of HMX-based explosives at elevated temperatures (i.e. T = 150 -- 180C) and moderate pressures (i.e. P = 10 -- 100 MPa). These conditions more closely mimic the pressure and temperatures of an explosive shortly after ignition of a thermal explosion. We will discuss the deflagration rates of HMX based explosives at elevated temperatures and make comparisons with thermal explosion studies on the same materials. [Preview Abstract] |
Tuesday, June 28, 2011 10:00AM - 10:15AM |
H2.00004: The Role of Binder in Deflagrating HMX-based Explosives J.W. Tringe, H.W. Levie, E.A. Glascoe, D.W. Greenwood, M.R. De Haven, J.D. Molitoris, H.K. Springer Deflagration rates are known to be a strong function of temperature and pressure, but chemical reactions facilitated by the explosive's binder can also play an important role. Here we report a study of two HMX-based formulations, PBX-9501 (HMX 95{\%}, estane 2.5{\%}, bdnpa 1.25{\%}, and bdnpf 1.25{\%}) and LX-10 (HMX 95{\%}, Viton-A 5{\%}), which we use to investigate the origins of violence in thermal explosions. We employ flash x-ray radiography to directly image the rates at which reaction fronts proceed in a confined vessel. Photonic Doppler velocimetry (PDV) characterizes the vessel wall motion as a function of time. Our results show that thermal explosions of PBX-9501, with its more reactive binder, are more violent than explosions of LX-10. In LX-10, we observe quenched deflagration and limited violence. In PBX-9501, however, a higher deflagration rate is developed and sustained even after vessel rupture. Thermal explosions of initially-confined PBX-9501 therefore are more complete and significantly more violent. [Preview Abstract] |
Tuesday, June 28, 2011 10:15AM - 10:30AM |
H2.00005: Study of Thermal Sensitivity and Thermal Explosion Violence of Energetic Materials in the LLNL ODTX System Peter Hsu, Gary Hust, Chadd May, Michael Howard, Keo Springer, Jon Maienschein Some energetic materials may explode at fairly low temperatures and the violence from thermal explosion may cause a significant damage. Thus it is important to understand the response of energetic materials to thermal insults for safe handling and storage of energetic materials. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory can measure times to explosion, lowest ignition temperatures, and determine kinetic parameters of energetic materials. Samples of different configurations can be tested in the system. The ODTX testing can also generate useful data for determining thermal explosion violence of energetic materials. After the ODTX testing, each anvil cavity size was monitored to obtain the thermal explosion violence data. In this paper, we will present some recent ODTX experimental data and compare thermal explosion violence and detonation violence. [Preview Abstract] |
Tuesday, June 28, 2011 10:30AM - 10:45AM |
H2.00006: Development of the Small Scale Violence Thermal Test Susan Sorber When developing new explosive formulations, one of the most important safety goals is to characterise the formulations' scale of response to thermal insults. Established tests provide indications of violence of response from thermal stimuli through dent/fragment analysis of heater anvils and visual observations. Utilising recent advances in diagnostic technologies, a test is under development to obtain a numerical value for the violence of response to thermal stimuli on a small explosive sample. Furthermore, the test has been designed so that it can accept pressed explosive pellets. This enables the test to be conducted at the small-scale development stage and thus is anticipated to be if use in the screening of new materials. In continuation of previously published work describing the test development, twenty-seven new cook-off experiments have been conducted. Eleven explosive compositions were subjected to the same slow heat input profile. As a sample rapidly decomposed, part of the steel confinement was designed to produce a pellet whose velocity was measured using a Heterodyne Velocimeter (Het-V). Temperatures of the confinement unit were also recorded. A development aim is to interpret this data to provide useful information on the violence of decomposition. This is discussed in the paper and leads to the data from these experiments being presented in order of increasing violence of response. [Preview Abstract] |
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