Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session D2: Energetic and Reactive Materials: Metalized Explosives I |
Hide Abstracts |
Chair: Paul Anderson, ARDEC Room: Grand Ballroom AB |
Monday, July 10, 2017 2:00PM - 2:15PM |
D2.00001: Scaling of the Propulsive Capability of Aluminized Gelled Nitromethane Jason Loiseau, Andrew Higgins, David Frost, Fan Zhang It is well accepted that small mass fractions (\textless 20{\%}) of micron-scale aluminum particles added to a high explosive can react quickly and with sufficient exothermicity to improve metal-acceleration ability (AA) relative to an equal volume of only the base explosive. In order for the aluminum to increase AA, exothermicity must more than offset losses in gas-production and from heating and accelerating the solid particle in the flow. Furthermore, particles must react promptly to deliver this energy prior to loss in driving pressure with product expansion or acoustic decoupling from the driven material. For these reasons many aluminized formulations exhibit slight or no increase in AA ability. Furthermore, AA ability is typically studied using the cylinder test, which specifies a fixed, heavy copper wall. In the present study the authors have used symmetric sandwiches of flyer plates of varying thicknesses to examine how charge scaling and plate acceleration timescales influence the enhancement in AA for different mass fractions and sizes of aluminum particles. Nitromethane gelled with 4{\%} Poly(methyl methacrylate) by mass was used as the base explosive. 3M K1 microballoons were added at a mass fraction of 0.5{\%} to sensitize the mixture. Mass fraction of aluminum was varied between 10{\%} and 40{\%} and particle size was varied from 2 $\mu $m to 100 $\mu $m. For small mass fractions of alumimum, an enhancement in AA was observed for all particle sizes and flyer configurations and indicated an onset of reaction very close to the sonic plane of the detonation wave. [Preview Abstract] |
Monday, July 10, 2017 2:15PM - 2:30PM |
D2.00002: Ignition threshold of aluminized HMX-based PBXs Christopher Miller, Min Zhou We report the results of micromechanical simulations of the ignition of aluminized HMX-based PBX under loading due to impact by thin flyers. The conditions analyzed concern loading pulses on the order of 20 nanoseconds to 0.8 microseconds in duration and impact piston velocities on the order of 300-1000 ms$^{-1}$. The samples consist of a stochastically similar bimodal distribution of HMX grains, an Estane binder, and 50 $\mu$m aluminum particles. The computational model accounts for constituent elasto-vicoplasticity, viscoelasticity, bulk compressibility, fracture, interfacial debonding, fracture, internal contact, bulk and frictional heating, and heat conduction. The analysis focuses on the development of hotspots under different material settings and loading conditions. In particular, the ignition threshold in the form of the James relation and the corresponding ignition probability are calculated for the PBXs containing 0\%, 6\%, 10\%, and 18\% aluminum by volume. It is found that the addition of aluminum increases the ignition threshold, causing the materials to be less sensitive. Dissipation and heating mechanism changes responsible for this trend are delineated. [Preview Abstract] |
Monday, July 10, 2017 2:30PM - 2:45PM |
D2.00003: Multiphase blast interaction between heterogeneous explosives Robert Ripley, Sydney Ryan, Charles M. Jenkins Spherical charges loaded with micrometric metal powders feature explosively dispersed particle fields. The interaction phenomena of opposing multiphase flow fields from multiple charges depend on the charge spacing, loading configuration and particle morphology. For identical heterogeneous charges with a separation distance in the near field, the multiphase blast interaction includes particle-particle collision in the shocked air and impinging detonation products between the charges. Experiments recorded using high-speed framing cameras show the blast interaction process and resolve details of the multiphase structures. Hydrocode simulations are conducted using inelastic Lagrangian particle groups with a Direct Simulation Monte Carlo particle collision model. The numerical results distinguish the multiphase interaction layer and gas dynamic boundaries, with an emphasis on the particle laden Mach stem. The experimental results provide data for comparison to the interacting front velocities and Mach stem velocity. Modeling results for twin charges are shown to be different from a single heterogeneous blast reflection due to the stochastic and dissipative particle collisions. Remaining differences between the experimental and numerical results are discussed. The numerical results are further analyzed to assess particle fragmentation and potential for enhanced reaction in the interaction region between heterogeneous charges. DISTRIBUTION A. Approved for public release; distribution is unlimited. 96TW-2017-0079. [Preview Abstract] |
Monday, July 10, 2017 2:45PM - 3:00PM |
D2.00004: Using Underwater Explosion and Cylinder Expansion Tests to Calibrate Afterburn Models for Aluminized Explosives Rasmus Wedberg The study explores the combined use of underwater performance tests and cylinder expansion tests in order to parameterize detonation models for aluminized explosives which exhibit afterburning. The approach is suggested to be used in conjunction with thermochemical computation. A formulation containing RDX and aluminum powder is considered and several charges with varying masses are submerged and detonated. Pressure gauges are employed at horizontal distances scaling with the charge diameter, and the specific shock wave energy is shown to increase with charge mass. This is attributed to the combustion of aluminum particles after the Chapman-Jouguet plane. Cylinder expansion tests are carried out using Photon Doppler Velocimetry to register the wall expansion velocity. The tests are modeled using a multi-material arbitrary Lagrangian-Eulerian approach with the Guirguis-Miller model describing detonation with afterburning. The equation of state and afterburn rate law parameters are adjusted such that the model reproduces the results from the cylinder expansion and underwater tests. The approach seems promising, and might be valuable for aluminized explosive formulations intended to be used in a variety of confinement conditions. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700