Protection against explosive blasts
Simple, hinged cover plate is effective against high explosive blasts. Blast energy under cover is transformed into kinetic energy of plate.
Bement, L. J.↗
SEARCH · Engineering Papers
Results for “HIGH EXPLOSIVES”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Evolution of Carbon Clusters in the Detonation Products of the Triaminotrinitrobenzene (TATB)-Based Explosive PBX 9502
Here, the detonation of carbon-rich high explosives yields solid carbon as a major constituent of the product mixture and, depending on the thermodynamic conditions behind the shock front, a variety of carbon allotropes and morphologies may form and evolve. We applied time-resolved small angle x-ray scattering (TR-SAXS) to investigate the dynamics of carbon clustering during detonation of PBX 9502, an explosive composed of triaminotrinitrobenzene (TATB) and 5 wt% fluoropolymer binder. Solid carbon formation was probed from 0.1 to 2.0 μs behind the detonation front and revealed rapid carbon cluster growth which reached a maximum after ~200 ns. The late-time carbon clusters had a radius of gyration of 3.3 nm which is consistent with 8.4 nm diameter spherical particles and matched particle sizes of recovered products. Simulations using a clustering kinetics model were found to be in good agreement with the experimental measurements of cluster growth when invoking a freeze-out temperature, and temporal shift associated with the initial precipitation of solid carbon. Product densities from reactive flow models were compared to the electron density contrast obtained from TR-SAXS and used to approximate the carbon cluster composition as a mixture of 20% highly ordered (diamond-like) and 80% disordered carbon forms, which will inform future product equation of state models for solid carbon in PBX 9502 detonation product mixtures.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Segmentation of RDX and TNT in X‐Ray Computed Tomography Reconstructions of Melt‐Cast Explosives
ABSTRACT Three‐dimensional mesoscale characterization of heterogeneous melt‐cast high explosives is challenging because of the difficulty differentiating binder from explosive crystals: two functionally different materials which are typically similar in density by design. Here, we report an algorithm which can differentiate hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) from 2,4,6‐trinitrotoluene (TNT) in x‐ray computed tomography (CT) volumes with tens of microns resolution. This method allows us to quantify RDX/TNT content, porosity, and RDX domain size. We calibrated the segmentation algorithm using simulated x‐ray CT volumes containing object models of RDX crystals within a TNT matrix. We then segmented and analyzed CT data for Composition B (Comp B), a 60/40 RDX/TNT mixture, and Cyclotol, a 75/25 RDX/TNT mixture. We examined melt‐cast samples fabricated with 100% theoretical maximum density (TMD) and 85% TMD. For the 100% TMD Comp B and Cyclotol samples, the RDX content values calculated by segmentation were 3% and 9% lower, respectively, than the values measured by high‐performance liquid chromatography on material from the same synthesis lots. This result is consistent with the expected underreporting of RDX content resulting from x‐ray CT resolution limits on RDX particles with diameters smaller than 25 µm. The 85% TMD samples were less accurately segmented with our algorithm due to the confounding presence of voids.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Simple Integral Experiment (SIX) Project: Comparison of hydrocode simulations of an imploding hemisphere with measured shock wave velocities
Report discusses use of hydrodynamic calculations to evaluate the ability of the CTH code to simulate the velocities of a copper hemispherical shell imploded by a sweeping high-explosive wave detonated at the pole, with a comparison of results to unpublished Los Alamos National Laboratory data.
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
A far- and Mid-infrared Study of HMX (octahydro-1 3 5 7-tetranitro-1 3 5 7-terazocine) Under High Pressure
We report two separate synchrotron FTIR measurements of the high explosive HMX at ambient temperature and static high pressure in the far- (100-500 wavenumbers) and mid- (500-3200 wavenumbers) infrared (IR) regions up to 30 GPa. The sample for the far-IR experiment was loaded with no pressure-transmitting medium and the sample for the mid-IR study utilized a KBr pressurizing medium. Two possible phase transitions from beta-HMX at ambient conditions were observed near 5 and 12 GPa (likely into the epsilon phase). A phase transition was observed near 25 GPa probably into the delta phase. Pressure cycling in both experiments found no irreversible damage within this pressure range.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Experimental and theoretical investigation into the high pressure deflagration products of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105)
Diamond anvil cell (DAC) laser ignition experiments and reactive ab initio molecular dynamics (AIMD) simulations were performed on the high explosive (HE) LLM-105 to investigate its high pressure (HP) deflagration chemistry. Raman and optical spectroscopy measurements reveal LLM-105 reacts into an opaque carbonaceous product at 4–25 GPa. At pressures >~ 27 GPa, the reaction product consists of an amorphous optically transparent solid and nitrogen (N 2 ) in the solid phase. While not a one-to-one comparison due to the small time and length scales, the HP AIMD simulations show that some of the product is molecular N 2 , in qualitative agreement with experiment, while above 20 GPa most of the product consists of large amorphous C x H y N z O k clusters. Clustering is enhanced with pressure and reduces with temperature. In the experiments with initial sample pressure >~ 25 GPa, the pressure within the DAC decreases with minimal change in DAC cavity area. At initial sample pressures of 43.9 GPa, when quenched to 0 K, simulations predict a product experiencing a lower pressure consistent with the experimental measurement at lower load pressures. In conclusion, the results are important for understanding the HP deflagration chemistry of LLM-105.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Dynamic Fracture Simulations of Explosively Loaded Cylinders
This report documents the modeling results of high explosive experiments investigating dynamic fracture of steel (AerMet® 100 alloy) cylinders. The experiments were conducted at Lawrence Livermore National Laboratory (LLNL) during 2007 to 2008 [10]. A principal objective of this study was to gain an understanding of dynamic material failure through the analysis of hydrodynamic computer code simulations. Two-dimensional and three-dimensional computational cylinder models were analyzed using the ALE3D multi-physics computer code.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Explosive Soot Challenge (Final Report)
This project assembled a broad ensemble of modeling and experimentation tools to study the morphological and optical properties of detonation soots in explosive fireballs. A gram-scale hemispherical high explosive was studied in a low-pressure controlled environment using in-situ experimentation with diffusely illuminated visible absorption spectroscopy, particle sizing through light scattering techniques, and post-test collections with subsequent morphological analysis. Hydrocode modeling was performed to replicate the detonation flow observations, and subsequent aerosol kinetics models provided particle size distributions and extinction coefficients from the hydrocode results. Experimentally observed soot morphologies agreed with expectation from the literature - a bimodal distribution was found, brought upon by the particles growing to a size where their inertia and fluid wakes are non-negligible. The aerosol kinetics model did not replicate the observed bimodal size distribution for lack of a coagulation kernel to represent the behavior. To recover particulate optical properties, a spectrally resolved absorption spectroscopy method termed Spectral diffuse back-illuminated extinction imaging (SBI-EI) was developed and implemented on two explosive types. Inverting the absorption spectra using a Kramers-Kronig consistent method yielded the complex index of refraction for the soots produced by the explosives. This method resulted in an unrealistic index of refraction for one of the two explosives, and this is suspected to be due to the model neglecting scattering brought upon by the large particle sizes observed. In addition to the core work, three additional studies were performed in parallel. These investigated the impact of scattering on diffuse absorption spectroscopy, studied how soots oxidate and sublimate in a well-controlled shock tube, and laid the theoretical groundwork for a new collision kernel to replicate the bimodal size distribution from the observations. Summaries of these efforts are included at the end of this report.
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
Laser-Induced Breakdown Spectroscopy (LIBS) as a Complement to Large-Scale Detonations and Means to Characterize Intermediates STL-05-14, Year 2 of 2
Presentation describes project to demonstrate that laser-induced breakdown spectroscopy (LIBS) can complement high-explosive field tests and the modeling for such tests. In the project, aluminum data collected using LIBS was compared to both explosive test chamber and field data, and studies involving LIBS of graphite and sparked air—relevant to detonation product species and explosion-shocked air—were performed, with the conclusion that LIBS produces results consistent with chamber and field results, and offers finer resolution than either chamber or field collects.
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
Review of the Effects of Polymer Binder Properties on Microstructure and Irreversible Volume Growth of Plastic Bonded Explosives Formulations
The rational design of effective polymeric binders for the formulation of plastic-bonded explosives (PBX) is challenging due to their inherent compositional complexity. The composites comprise irregularly shaped energetic material (EM) powders coated with low weight fractions of polymer via non-equilibrium processes such as slurry coating. Defects can deleteriously affect PBX stability and performance: nano- to micrometer-scale voids can act as loci for hot spots, lowering deflagration and detonation temperatures in unpredictable ways. Furthermore, some nominally desirable polymer properties are at odds with each other: e. g. good flow characteristics are desirable for coating and adhesion, but mechanical stiffness is needed to prevent deformation and cracking of PBX under mechanical stress. Good binder adhesion is critical, but the best means to predict and measure adhesion in PBX is not obvious. Experimental methods of determining binder adhesion on model surfaces may not capture polymer structural configurations relevant to deposition during coating. Molecular dynamics-based computational models have predicted key observables in PBX formulation, suggesting that they may be powerful tools for binder selection. In this review, primarily recent (~2006 and later) literature on polymeric binders for insensitive HE (IHE) is surveyed. We focus on how binder properties influence observable PBX properties as resistance to irreversible volume growth and void formation in PBX formulations mainly (but not exclusively) featuring 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as the EM (e. g. PBX 9502, LX-17 and others). Conclusions from these studies yield useful guidelines for choosing HE binder candidates, as well as for the general design of highly-filled polymer composite materials. Finally, studies describing challenges in PBX formulation with the newer and more energetically dense high explosive, LLM-105, will be discussed.
adhesion↗
A New Multiphase Equation of State for Composition B
We describe the construction of a complete equation of state for the high explosive Composition B in its unreacted (inert) form, as well as chemical equilibrium calculations of its detonation products. The multiphase reactant EOS is of SESAME type, and was calibrated to ambient thermal and mechanical data, the shock initiation experiments of Dattelbaum, et al., and the melt line of trinitrotoluene (TNT).
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
Steady Laminar Flame for 1-Step Thermal Decomposition Model of PBX 9501
We have recently developed a new 1-step thermal decomposition model of PBX 9501 high explosive. In this report, we examine the behavior of the model in 1-D steady laminar flame calculations. In particular, the dependencies of the steady laminar flame velocity on initial pressure, thermal conductivies and parameters of the thermal decomposition model are investigated. The results of our numerical calculations are compared to available experimental data.
42 ENGINEERING↗
Shock-to-detonation transition simulations
Shock-to-detonation transition (SDT) experiments with embedded velocity gauges provide data that can be used for both calibration and validation of high explosive (HE) burn models. Typically, a series of experiments is performed for each HE in which the initial shock pressure is varied. Here we describe a methodology for automating a series of SDT simulations and comparing numerical tracer particle velocities with the experimental gauge data. Illustrative examples are shown for PBX 9502 using the HE models implemented in the xRage ASC code at LANL.
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
Notes on Davis EOS: Historical Perspective, Derivations & Physical Considerations
Davis reactant and product semi-empirical EOS have been introduced in a series of publications by W. C. Davis. These EOS are convenient to use in conjunction with reactive burn models to parameterize the thermodynamic response of quiescent high explosives (HE) and the mixture of HE decomposition products. There is a history of development of these EOS with different formulae and functional forms found in different papers. The goal of the present notes is to track that history, clarify the physical motivation behind various modifications to Davis EOS over time, and collect all the relevant formulae in one place.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Estimating physics models and quantifying their uncertainty using optimization with a Bayesian objective function
This paper reports a verification study for a method that fits functions to sets of data from several experiments simultaneously. The method finds a maximum a posteriori probability (MAP) estimate of a function subject to constraints (e. g., convexity in the study), uncertainty about the estimate, and a quantitative characterization of how data from each experiment constrains that uncertainty. While the present work focuses on a model of the Equation Of State (EOS) of gasses produced by detonating a high explosive, the method can be applied to a wide range of physics processes with either parametric or semi-parametric models. As a verification exercise, a reference EOS is used and artificial experimental data sets are created using numerical integration of ordinary differential equations and pseudo-random noise. The method yields an estimate of the EOS that is close to the reference, and identifies how each experiment most constrains the result.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
JWL in a Nutshell
The Jones-Wilkins-Lee (JWL) equation of state is an analytical equation of state (EOS) used in the modeling of detonation products of high explosives. The JWL parameters for typical explosives are found in a series of reports by Brigitta Dobratz. The JWL parameters are usually derived from thermochemical codes or experimental cylinder tests using an elaborate and arcane procedure. It is often said that the JWL parameters need to be “self-consistent”, “thermodynamically consistent”, or “consistent with the conservation laws of mass, momentum, and energy.” The purpose of this document is to explain and illuminate what that means. Each parameter in the JWL equation of state is connected to the other parameters. An ideal simulation would produce detonation products at the Chapman-Jouguet state. I begin by describing the form of this equation of state.
Engineering(42)↗
In-Situ Silver Acetylide Silver Nitrate Explosive Deposition Measurements Using X-Ray Fluorescence.
The Light Initiated High Explosive facility utilized a spray deposited coating of silver acetylide - silver nitrate explosive to impart a mechanical shock into targets of interest. A diagnostic was required to measure the explosive deposition in - situ. An X - ray fluorescence spectrometer was deployed at the facility. A measurement methodology was developed to measure the explosive quantity with sufficient accuracy. Through the use of a tin reference material under the silver based explosive, a field calibration relationship has been developed with a standard deviation of 3.2 % . The effect of the inserted tin material into the experiment configuration has been explored.
Covert, Timothy Todd↗
Instrumentation for measuring flow properties in an explosively driven shock tube
Flow and radiative properties of air in high explosive shock tube
Borucki, W. J.↗