Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session D4: EM.3 Energetic Materials: Safety |
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Chair: Geoff Brown, Los Alamos National Laboratory Room: Vashon |
Monday, July 8, 2013 1:45PM - 2:00PM |
D4.00001: ABSTRACT WITHDRAWN |
Monday, July 8, 2013 2:00PM - 2:15PM |
D4.00002: Bullet Impact Safety Study of PBX-9502 Louis Ferranti A new small arms capability for performing bullet impact testing into energetic materials has recently been activated at Lawrence Livermore National Laboratory located in the High Explosives Applications Facility (HEAF). The initial capability includes 0.223, 0.30, and 0.50 testing calibers with the flexibility to add other barrels in the near future. An initial test series has been performed using the 0.50 caliber barrel shooting bullets into targets using the TATB based explosive PBX-9502 and shows an expected non-violent reaction. Future experiments to evaluate the safety of new explosive formulations to bullet impact are planned. A highlight of the new capability along with discussion of the initial experiments to date will be presented including future areas of research. [Preview Abstract] |
Monday, July 8, 2013 2:15PM - 2:30PM |
D4.00003: Size-effect of explosive sensitivity under low velocity impact Danzhu Ma, Pengwan Chen, Qiang Zhou Low velocity impact may ignite the solid high explosives and cause undesired explosion incidents. The safety of high explosives under low velocity impact is one of the most important problems in handling, manufacture, storage, and transportation procedures. More and more evaluation tests have been developed for low velocity impact scenarios, including, but not limited to the drop hammer impact test, the Susan test, the Spigot test, and the Steven test, with a charge mass varying from tens of milligrams to several kilograms. The effects of specimen size on explosive sensitivity were found in our drop hammer impact test and Steven tests, including the threshold velocity/height and reaction violence. To further analyze the size effects on explosive sensitivity under low velocity impacts, we collected the impact sensitivity data of several PBX explosives in the drop hammer test, the Steven test, the Susan test and the Spigot test. The effective volume of explosive charge and the threshold specific mechanical energy were introduced to investigate the size-effect on the explosive ignition thresholds. The effective volumes of explosive charge in Steven test and Spigot test were obtained by numerical simulation, due to the localization of the impact. The threshold specific mechanical energy is closely related to the effective volume of explosive charge. The results show that, with the increase of effective volume, the specific mechanical energy needed for explosive ignition decreases and trends to reach a constant value. The mechanisms of size effects on explosive sensitivity are also discussed. [Preview Abstract] |
Monday, July 8, 2013 2:30PM - 2:45PM |
D4.00004: Microscopic modeling of ignition and burning for well-arranged energetic crystals in response to drop-weight impact Yanqing Wu, Fenglei Huang It has long been recognized that during impact of energetic crystalline solids, some form of energy localization must focus the impact energy into hot spots. However, it was insufficient to obtain just the energy required to cause ignition of an individual hot spot. Hot-spots ignition as well as the subsequent burning together determines the possible occurrence of explosion. A micromechanics theoretical approach was developed, to model hot-spots formation and growth to burning for a single layer of impacted energetic particles. To provide supporting evidence for theoretical analyses, numerical simulations were performed to investigate the thermo-mechanical interactions among the well-arranged energetic crystals. Once hot- spots ignition occurs, the macrokinetics of chemical reactions can be determined by hot-spots density, combustion wave velocity and geometric factor. Considering the micro-particle plasticity, frictional heating, melting, fracture, and chemical reaction at particle level, effects of loading parameters and sample characteristics on ignition and burning were discussed. The resulting reaction may or may not develop into a violent event, may be sustained or be extinguished, which can be predicted by the present model. Visual information obtained by high-speed photography and measured pressure-time data using our self-established experimental device are used to validate the calculated results. [Preview Abstract] |
Monday, July 8, 2013 2:45PM - 3:00PM |
D4.00005: Thermal and mechanical responses of PBX 9501 under contact excitation under various driving intensities J. Mares, J. Miller, D. Moore, L. Groven, J. Rhoads, S. Son The thermal and mechanical responses of a explosive (PBX 9501) and two non-energetic mock materials (900-21 and PBS 9501) under high-frequency mechanical excitation are presented with various driving intensities. Direct contact ultrasound transducers were used to excite samples through a frequency range of 50 kHz to 40 MHz. The mechanical response of each sample was approximated from a contact receiving transducer and trends were confirmed via laser Doppler vibrometry. The steady-state thermal response of the samples was measured at discrete excitation frequencies via infrared thermography. A maximum temperature rise of approximately 15 K was observed in PBX 9501, and the mock materials exhibited similar thermal characteristics. Temperature gradients were calculated to estimate the total heat generated within the samples due to the mechanical excitation. The active heating mechanisms were found to be highly dependent on the frequency of excitation. Possible mechanisms of heating at frequencies below 1 MHz are likely related to bulk motion. Above this frequency, the active heating mechanisms are likely related to particle-scale processes. The observed phenomena may prove useful in the aid of current trace vapor detection methods for explosives. [Preview Abstract] |
Monday, July 8, 2013 3:00PM - 3:15PM |
D4.00006: The ODTX System for the Study of Thermal Sensitivity and Thermal Explosion Violence of Energetic Materials Peter Hsu, Gary Hust, John Reynolds, Keo Springer, Larry Fried, Jon Maienschein Incidents caused by fire and combat operations in battlefields can expose energetic materials to unexpected heat that may cause thermal explosion, structural damage and casualty. Some explosives may thermally explode at fairly low temperatures (\textless 100 C) 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. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory can measure times to explosion, threshold thermal explosion temperature, and determine kinetic parameters of energetic materials. Samples of different configurations (pressed part, powder, paste, and liquid) can be tested in the system. The ODTX testing can also provide useful data for assessing the thermal explosion violence of energetic materials. In this paper, we will present some recent ODTX experimental data and compare thermal explosion violence of different energetic materials. [Preview Abstract] |
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