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At least 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Modeling the thermal deformation of TATB-based explosives. Part 1: Thermal expansion of “neat-pressed” polycrystalline TATB

We detail a modeling approach to simulate the anisotropic thermal expansion of polycrystalline (1,3,5-triamino-2,4,6-trinitrobenzene) TATB-based explosives that utilizes microstructural information including porosity, crystal aspect ratio, and processing-induced texture. This report, the first in a series, focuses on nonlinear thermal expansion of “neat-pressed” polycrystalline TATB specimens which do not contain any binder; additional complexities related to polymeric binder and irreversible ratcheting behavior are briefly discussed, however detailed investigation of these aspects are deferred to subsequent reports. In this work we have, for the first time, developed a mesoscale continuum model relating the thermal expansion of polycrystal TATB specimens to their microstructural characteristics. A self-consistent homogenization procedure is used to relate macroscopic thermoelastic response to the constitutive behavior of single-crystal TATB. The model includes a representation of grain aspect ratio, porosity, and crystallographic texture attributed to the consolidation process. A quantitative model is proposed to describe the evolution of preferred orientation of graphitic planes in TATB during consolidation and an algorithm constructed to develop a discrete representation of the associated orientation distribution function. Analytical and numerical solutions using this model are shown to produce textures consistent with previous measurements and characterization for isostatic and uniaxial “die-pressed” specimens. Predicted thermal strain versus temperature for textured specimens are shown to be in agreement with corresponding experimental measurements. Using the developed modeling approach, several simulations have been run to investigate the influence of microstructure on macroscopic thermal expansion behavior. Results from these simulations are used to identify qualitative trends. Implications of the identified trends are discussed in the context of thermal deformation of engineered components whose consolidation process is generally more complex than isostatic or die-pressed specimens. Finally, an envisioned application of the modeling approach to simulating thermal expansion of weapon systems and components is outlined along with necessary future work to introduce the effects of binder and ratcheting behavior. Key conclusions from this work include the following. Both porosity and grain aspect ratio have an influence on the thermal expansion of polycrystal TATB considering realistic material variability. Thepreferred orientation of the single crystal TATB [001] poles within a polycrystal gives rise to pronounced anisotropy of the macroscopic thermal expansion. The extent of this preferred orientation depends on the magnitude of deformation, and consequently, is expected to vary spatially throughout manufactured components much like porosity. The modeling approach presented here has utility toward bringing spatially variable microstructural features into macroscale system engineering modelsAbstract Not Provided

36 MATERIALS SCIENCE↗
DOE OSTI2014

Advanced explosives research and education [Slides]

LANL Advanced Homemade Explosives Course: • Joint Course offered for all DOD EOD Technicians. – First course June 2013, 12 courses to date , ~ 220 EOD technicians trained. • Focus is on the safety and recognition of HMEs, formulation/ synthesis, improvised detonators and detection. • LANL instructors numerous divisions.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2014

Investigation of the fragmentation of an explosively driven cylinder

Explosively driven fragmentation is highly complex. To better understand the field detonation, different methodologies (Lagrangian (with a failure threshold in VisIt and element erosion), ALE and embedded grid) were simulated to provide a comparison to the experimental data through the utilization of fragment distributions and gross deformation metrics. Provided with the geometrical parameters and the results from the experimental data, the computer simulations were conducted after the successful writing of each input file. Mesh refinement – a scalar multiplier applied to the mesh to refine the results – was then studied. The objective was to find a value that parallels the experimental results as the mesh can be refine indefinitely, theoretically. Various mesh resolution scales were simulated and the results graphically compared, using the damage and failure variables from a statistical Johnson Cook failure model, the number of fragments over time as well as time required for each simulation to run and number of processors utilized. The desired result is a calculated method to quantify the comparison being performed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

High Pressure DSC on LLM-105 and other High Explosives

The purpose of this study is to establish an experimental setup to fundamentally understand the thermal decomposition of energetic materials as a function of pressure and to be able to model the reaction kinetics of explosive materials. These kinetic models in-turn could be applied to the aging and compatibility of these materials.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Furball Explosive Breakout Test [Poster]

For more than 30 years the Onionskin test has been the primary way to study the surface breakout of a detonation wave. Currently the Onionskin test allows for only a small, one dimensional, slice of the explosive in question to be observed. Asymmetrical features are not observable with the Onionskin test and its one dimensional view. As a result, in 2011, preliminary designs for the Hairball and Furball were developed then tested. The Hairball used shorting pins connected to an oscilloscope to determine the arrival time at 24 discrete points. This limited number of data points, caused by the limited number of oscilloscope channels, ultimately led to the Hairball’s demise. Following this, the Furball was developed to increase the number of data points collected. Instead of shorting pins the Furball uses fiber optics imaged by a streak camera to determine the detonation wave arrival time for each point. The original design was able to capture the detonation wave’s arrival time at 205 discrete points with the ability to increase the number of data points if necessary.

42 ENGINEERING↗
DOE OSTI2015

A Bayesian inversion framework for yield and height-of-burst/depth-of-burial for near-surface explosions

A Bayesian inversion framework is presented to estimate the yield of an explosion and height-of-burst/depth-of-burial (HOB/DOB) using seismic and air pressure data. This is accomplished by first calibrating the parameters in the forward models that relate the observations to the yield and HOB/DOB and then using the calibrated model to estimate yield and HOB/DOB associated with a new set of seismic and air pressure observations. The MCMC algorithms required to perform these steps are outlined, and the results with real data are shown. Finally, an extension is proposed for a case when clustering in the seismic displacement occurs as a function of different types of rock and other factors.

58 GEOSCIENCES↗
DOE OSTI2014

Explosive Formulation Code Naming SOP

The purpose of this SOP is to provide a procedure for giving individual HME formulations code names. A code name for an individual HME formulation consists of an explosive family code, given by the classified guide, followed by a dash, -, and a number. If the formulation requires preparation such as packing or aging, these add additional groups of symbols to the X-ray specimen name.

42 ENGINEERING↗
DOE OSTI2015

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↗
DOE OSTI2017

A Study of China s Explosive Growth in the Plug-in Electric Vehicle Market

The year 2015 marks a turning point in China s plug-in electric vehicle (PEV) or new energy vehicle (NEV) industry, with an explosive growth in both productions and sales, following the gloomy period of 2009-2012. The PEV production in 2015 reached a record level of nearly 380,000 units, a 352 % increase from 2014, making China the largest PEV market in the world. For the potential implications on energy and the environment, it is worth studying the driving forces of China s PEV market and understanding its future trajectory and dynamics. The key findings of this report are listed in the following. Though controversial, the government monetary incentives have played a significant role to impel China to be the largest light PEV (191,100 units) market in the world. Chinese vehicle buyers appear more price sensitive on PEVs. Inexpensive low-cost micro electric vehicles are the most popular vehicle model in China s PEV market (38.9 % of the PEV market in 2015). In contrast, the premium or luxury vehicles are more popular in the gasoline vehicle segment. In fact, China is expected to be the largest premium car market in 2016. The PEV sales growth is primarily possible because of the young domestic private-owned auto manufacturers, which are mostly located in south China. Top-tier conventional vehicle automakers in China appear to be less proactive in the PEV market, based on market shares. This is in clear contrast to the U.S. market, where major automakers are generally the primary players in the PEV market. The PEVs produced by the domestic automakers are concentrated in the low-end market segment, while the high-end vehicle segment is dominated by the foreign brands. At present, the substantial market growth and government subsidies afford the domestic entrants to quickly gain profits in the low-end segment. The PEV consumers in China are very sensitive to the vehicle price, thus prefer the PEVs with cheaper prices after government subsidies, and care less about the driving quality and comfort. In contrast, most PEV consumers in the United States (U.S.) have higher incomes, view the PEVs as a high-status symbol, and care less about the vehicle prices, and therefore welcome the premium PEVs more in the U.S. The PEV financial subsidies by the Chinese government are divided into three stages based on the strategic directions and policies. In 2009 2012, government incentives concentrated on the public fleet vehicles, while excluding the individual consumers from the subsidies in most cities. In 2013 2015, comprehensive central/local government incentives were extended to all vehicle purchasers including the individual buyers in most cities, which was conducive to the phenomenal growth of the PEV sales. For years 2016 to 2020, monetary incentives are being phased out and will be substituted by other non-monetary incentives (such as the standards for Chinese Cooperate Average Fuel Consumption and New Energy Vehicle Credits) for the sustainable development of the PEV market. The PEV subsidy fraud has drawn attention by the central government, which prompts the government to be more prudent about monetary incentives. With the advantage of high acceptance in the PEV market and integrated EV charging infrastructure, the region with better economic development brings a more aggressive PEV roll-out plan to the municipalities who are more willing to solve the local urban pollution while keeping the automotive market in sustainable growth. On the one hand, the local automakers are offered abundant subsidies from the Chinese government to those who intend to help the Chinese automotive industry seize the industrial upgrading opportunity to transform its manufacturing sector, and they have taken most shares of the PEV market. On the other hand, facing the trade barriers, the foreign automakers have dominated the premium PEV sales in China, although their total market shares in the PEV market are much less than the domestic automakers. In diverse selectable alternative fuel vehicle technologies, China has put its focus on the PEV technologies for the technological modernization in the automotive industry; the research and development in fuel cell vehicle technologies in China is less competitive compared with other countries such as Japan and the U.S. With the demand of batteries from the PEV automakers, the Chinese EV battery industry is aggressively expanding. It has risks in excessive production capacity, and faces the challenges from the competitors from Japan and South Korea.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2017

Explosive Infrasonic Events: Sensor Comparison Experiment (SCE)

SCE (sensor comparison experiment) 1 through 4 consists of a series of four controlled above-ground explosions designed to provide new data for overpressure propagation. Infrasound data were collected by LLNL iPhones and other sensors. Origin times, locations HOB, and yields are not being released at this time and are therefore not included in this report. This preliminary report will be updated as access to additional data changes, or instrument responses are determined.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Future Research Needed to Study the Response of an Explosive Assembly to Mechanical Insults

HE ignition caused by shear localization is the principal concern for safety analyses of postulated mechanical insults to explosive assemblies. Although prompt detonation from shock is certainly a concern, insults that lead to prompt detonation are associated with high velocity, and correspondingly rare. For high-density HMX assemblies, an impact speed (by a steel object) of 400 m/s is needed to develop a detonation in a run distance less than 30 mm. To achieve a steady plane shock, which results in the shortest run distance to detonation for a given peak pressure, the impactor diameter must exceed 60 mm, and thickness approach 20 mm. Thinner plates and/or smaller diameter ones require even higher impact velocity. Ignitions from shear localization, however, have been observed from impacts less than 50 m/s in Steven tests, less than 30 m/s from spigot impact tests, and less than 10 m/s from various drop tests. This lower velocity range is much frequent in postulated mechanical insults. Preliminary computer simulations and analyses of a variety of such tests have suggested that although each is accompanied by shear localization, there are differing detailed mechanisms at work that cause the ignitions. We identify those mechanisms that may be at work in a variety of such tests, and suggest how models of shear ignition, such as HERMES, may be revised and calibrated to conform to experiment. We suggest combining additional experiments with computer simulations and model development to begin confirm or uncover mechanisms that may be at work in a specific postulated event.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Magpie: Reliable High Explosive Equation of State

Work on Magpie in the Theoretical Division has produced an important fundamental capability to LANL. Magpie now has the ability to predictively generate High Explosive (HE) equations of state (EOS). The code’s software design allows for quick and easy implementation of new EOS models. This will allow for advances in EOS modeling of not just molecular fluids, but the EOS of almost any substance. Magpie leverages powerful techniques of equilibrium statistical thermodynamics to build EOSs from microscopic level knowledge of atomic and molecular properties.

74 ATOMIC AND MOLECULAR PHYSICS↗