Showing papers by "Tariq D. Aslam published in 2018"

Shock temperature dependent rate law for plastic bonded explosives

Abstract: A reactive flow model for the tri-amino-tri-nitro-benzene (TATB) based plastic bonded explosive PBX 9502 (95% TATB, 5% polymeric binder Kel-F 800) is presented. This newly devised model is based primarily on the shock temperature of the material, along with local pressure, and accurately models a broader range of detonation and initiation scenarios. Specifically, sensitivity changes to the initial explosive temperature are accounted for naturally and with a single set of parameters. The equation of state forms for the reactants and products, as well as the thermodynamic closure of pressure and temperature equilibration, are carried over from the Wescott-Stewart-Davis (WSD) model [Wescott et al., J. Appl. Phys. 98, 053514 (2005) and “Modeling detonation diffraction and dead zones in PBX-9502,” in Proceedings of the Thirteenth International Detonation Symposium (2006)]. This newly devised model, with Arrhenius state dependence on the shock temperature, based on the WSD equation of states, is denoted by AWSD. Modifying an existing implementation of the WSD model to the AWSD model in a hydrocode is a rather straightforward procedure.

Temperature of shocked plastic bonded explosive PBX 9502 measured with spontaneous Stokes/anti-Stokes Raman

Abstract: Raman spectra and velocimetry of shocked PBX 9502 (plastic bonded explosive composed of 95% triaminotrinitrobenzene (TATB) and 5% 3M Company Kel F-800 polymer binder) are reported with the Stokes/anti-Stokes ratio used to determine temperature after the shock reflects from a lithium fluoride window. Final pressures up to 14.5 GPa were tested, but the pressure induced absorption of TATB caused the Raman signal to decrease exponentially with pressure. The reflected shock temperature could be determined to 7 GPa, with an average increase of 14.9 K/GPa. Suggestions to adapt the technique to permit thermometry at higher temperatures are discussed, as are comparisons to a recently proposed equation of state for PBX 9502.

Gas gun experiments and numerical simulations on the HMX based explosive PBX 9501 in the overdriven regime

Abstract: A set of experiments was designed to measure the Hugoniot for the overdriven products equation of state (EOS) of PBX 9501 to extend data from which current EOS models draw. A series of shots was conducted by M-9 using the two-stage gas-guns at LANL. The experiments were modeled in FLAG, a Langrangian multiphysics code, using a one-dimensional setup which employed the WSD reactive burn model. A comparison of the modeled results to the experimental data reveals that the model is a good fit to the data in the lower pressure region. However, in the upper pressure region, the WSD results do not represent the data as well as in the lower regions. This is an indication that the model could be modified to more accurately reproduce data in all regions.

Dynamic Compaction of Nickel Powder Examined by X-Ray Phase-Contrast Imaging

Abstract: Understanding the shock response of porous, granular materials is important for many scientific applications. In this work, a propagation-based x-ray phase contrast imaging technique was used to examine the shock compaction response of Ni powder (particle size: 30 and 45 µm), encapsulated in PMMA cylinders, in situ and in real time. The propagating shock wave in the PMMA cylinder and the deformation of the Ni powder column were recorded, but the compaction wave in the Ni powder could not be observed due to insufficient penetration of x-ray photons through the sample. The overall shape of the deformed Ni column downstream of the PMMA shock looked qualitatively similar for both particle sizes: it deformed inward and then outward similar to a converging-diverging nozzle, followed by a ‘mushroom’-like structure at the impact face. A preliminary analysis of our data using shock-polar method provided insight into the observed shock and flow deflection angles at the PMMA/Ni interface, and permitted evaluation of the Ni powder EOS used in this work.

Shock, release and reshock of PBX 9502: experiments and modeling

Abstract: We examine shock, release and reshock into the tri-amino-tri-nitro-benzene (TATB) based explosive PBX 9502 (95% TATB, 5% Kel-F 800) from both an experimental and modeling point of view. The experiments are performed on the 2-stage light gas gun at Los Alamos National Laboratory and are composed of a multi-layered impactor impinging on PBX 9502 backed by a polymethylmethacrylate window. The objective is to initially shock the PBX 9502 in the 7 GPa range (too weak to start significant reaction), then allow a rarefaction fan to release the material to a lower pressure/temperature state. Following this release, a strong second shock will recompress the PBX. If the rarefaction fan releases the PBX to a very low pressure, the ensuing second shock can increase the entropy and temperature substantially more than in previous double-shock experiments without an intermediate release. Predictions from a variety of reactive burn models (AWSD, CREST, Augmented Ignition and Growth, SURF) demonstrate significantly different behaviors and thus the experiments are an excellent validation test of the models, and may suggest improvements for subsequent modeling efforts.

Analysis of steady compaction waves in polyurea aerogel

Abstract: Submitted for the SHOCK17 Meeting of The American Physical Society Analysis of steady compaction waves in polyurea aerogel MATTHEW A. PRICE, TARIQ D. ASLAM, JAMES J. QUIRK, Los Alamos National Laboratory — Steady compaction waves in an inert porous material are investigated using a p − α model. In a steady traveling wave reference frame, the one-dimensional Euler equations are reduced to a set of ordinary differential equations. A Mie-Grüneisen equation of state (EOS) is used with parameters calibrated for polyurea aerogel (PUA). Analytic solutions for non-equilibrium compaction are developed which compliment numerical models and are able to predict the complete wave structure, including the compaction wave speed, zone length, and final compacted solid volume fraction. The dynamic compaction of PUA is studied for a range of piston velocities. Three regions of behavior are identified: supersonic, subsonic-complete, and subsonic-partial compaction. Below a critical piston velocity, a subsonic compaction wave is produced without a leading shock. At even lower piston velocities, there is partial compaction and a greater dependence on the dynamic compaction relation. Some features and limitations of the current model are discussed. Matthew A. Price Los Alamos National Laboratory Date submitted: 16 Feb 2017 Electronic form version 1.4