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Languages : en
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The basic processes in the shock initiation of heterogeneous explosives have been investigated theoretically using a model of a cube of nitromethane containing 91 cubic air holes. The interaction of a shock wave with the density discontinuities, the resulting hot spot formation and interaction, and the buildup to propagating detonation were computed using three-dimensional numerical Eulerian hydrodynamics with Arrhenius chemical reaction and accurate equations of state. The basic process in the desensitization of a heterogeneous explosive by preshocking with a shock pressure too low to cause propagating detonation was numerically modeled.
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Languages : en
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Book Description
The basic processes in the shock initiation of heterogeneous explosives have been investigated theoretically using a model of a cube of nitromethane containing 91 cubic air holes. The interaction of a shock wave with the density discontinuities, the resulting hot spot formation and interaction, and the buildup to propagating detonation were computed using three-dimensional numerical Eulerian hydrodynamics with Arrhenius chemical reaction and accurate equations of state. The basic process in the desensitization of a heterogeneous explosive by preshocking with a shock pressure too low to cause propagating detonation was numerically modeled.
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Languages : en
Pages : 13
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A recent SMIS (Specific Munitions Impact Scenario) experimental series performed at Los Alamos National Laboratory has provided 3-dimensional shock initiation behavior of the HMX-based heterogeneous high explosive, PBX 9501. A series of finite element impact calculations have been performed in the ALE3D [1] hydrodynamic code and compared to the SMIS results to validate and study code predictions. These SMIS tests used a powder gun to shoot scaled NATO standard fragments into a cylinder of PBX 9501, which has a PMMA case and a steel impact cover. This SMIS real-world shot scenario creates a unique test-bed because (1) SMIS tests facilitate the investigation of 3D Shock to Detonation Transition (SDT) within the context of a considerable suite of diagnostics, and (2) many of the fragments arrive at the impact plate off-center and at an angle of impact. A particular goal of these model validation experiments is to demonstrate the predictive capability of the ALE3D implementation of the Tarver-Lee Ignition and Growth reactive flow model [2] within a fully 3-dimensional regime of SDT. The 3-dimensional Arbitrary Lagrange Eulerian (ALE) hydrodynamic model in ALE3D applies the Ignition and Growth (I & G) reactive flow model with PBX 9501 parameters derived from historical 1-dimensional experimental data. The model includes the off-center and angle of impact variations seen in the experiments. Qualitatively, the ALE3D I & G calculations reproduce observed 'Go/No-Go' 3D Shock to Detonation Transition (SDT) reaction in the explosive, as well as the case expansion recorded by a high-speed optical camera. Quantitatively, the calculations show good agreement with the shock time of arrival at internal and external diagnostic pins. This exercise demonstrates the utility of the Ignition and Growth model applied for the response of heterogeneous high explosives in the SDT regime.
Author: Charles L. Mader
Publisher: CRC Press
ISBN: 9780849331497
Category : Technology & Engineering
Languages : en
Pages : 456
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Book Description
Charles Mader, a leading scientist who conducted theoretical research at Los Alamos National Laboratory for more than 30 years, sets a new standard with this reference on numerical modeling of explosives and propellants. This book updates and expands the information presented in the author's landmark work, Numerical Modeling of Detonations, published in 1979 and still in use today. Numerical Modeling of Explosives and Propellants incorporates the considerable changes the personal computer has brought to numerical modeling since the first book was published, and includes new three-dimensional modeling techniques and new information on propellant performance and vulnerability. Both an introduction to the physics and chemistry of explosives and propellants and a guide to numerical modeling of detonation and reactive fluid dynamics, Numerical Modeling of Explosives and Propellants offers scientists and engineers a complete picture of the current state of explosive and propellant technology and numerical modeling. The book is richly illustrated with figures that support the concepts, and filled with tables for quick access to precise data. The accompanying CD-ROM contains computer codes that are the national standard by which modeling is evaluated. Dynamic material properties data files and animation files are also included. There is no other book available today that offers this vital information.
Author:
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Category :
Languages : en
Pages : 13
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Book Description
The SMIS (Specific Munitions Impact Scenario) experimental series performed at Los Alamos National Laboratory has determined the 3-dimensional shock initiation behavior of the HMX-based heterogeneous high explosive, PBX 9501. A series of finite element impact calculations have been performed in the ALE3D [1] hydrodynamic code and compared to the SMIS results to validate the code predictions. The SMIS tests use a powder gun to shoot scaled NATO standard fragments at a cylinder of PBX 9501, which has a PMMA case and a steel impact cover. The SMIS real-world shot scenario creates a unique test-bed because many of the fragments arrive at the impact plate off-center and at an angle of impact. The goal of this model validation experiments is to demonstrate the predictive capability of the Tarver-Lee Ignition and Growth (I & G) reactive flow model [2] in this fully 3-dimensional regime of Shock to Detonation Transition (SDT). The 3-dimensional Arbitrary Lagrange Eulerian hydrodynamic model in ALE3D applies the Ignition and Growth (I & G) reactive flow model with PBX 9501 parameters derived from historical 1-dimensional experimental data. The model includes the off-center and angle of impact variations seen in the experiments. Qualitatively, the ALE3D I & G calculations accurately reproduce the 'Go/No-Go' threshold of the Shock to Detonation Transition (SDT) reaction in the explosive, as well as the case expansion recorded by a high-speed optical camera. Quantitatively, the calculations show good agreement with the shock time of arrival at internal and external diagnostic pins. This exercise demonstrates the utility of the Ignition and Growth model applied in a predictive fashion for the response of heterogeneous high explosives in the SDT regime.
Author: J. E. Reaugh
Publisher:
ISBN:
Category :
Languages : en
Pages : 27
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Book Description
The fundamental picture that shock initiation in heterogeneous explosives is caused by the linking of hot spots formed at inhomogeneities was put forward by several researchers in the 1950's and 1960's, and more recently. Our work uses the computer hardware and software developed in the Advanced Simulation and Computing (ASC) program of the U.S. Department of Energy to explicitly include heterogeneities at the scale of the explosive grains and to calculate the consequences of realistic although approximate models of explosive behavior. Our simulations are performed with ALE-3D, a three-dimensional, elastic-plastic-hydrodynamic Arbitrary Lagrange-Euler finite-difference program, which includes chemical kinetics and heat transfer, and which is under development at this laboratory. We developed the parameter values for a reactive-flow model to describe the non-ideal detonation behavior of an HMX-based explosive from the results of grain-scale simulations. In doing so, we reduced the number of free parameters that are inferred from comparison with experiment to a single one - the characteristic defect dimension. We also performed simulations of the run to detonation in small volumes of explosive. These simulations illustrate the development of the reaction zone and the acceleration of the shock front as the flame fronts start from hot spots, grow, and interact behind the shock front. In this way, our grain-scale simulations can also connect to continuum experiments directly.
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Languages : en
Pages :
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Book Description
The basic processes in the shock initiation of heterogeneous explosives have been investigated theoretically using a model of a cube of nitromethane containing 91 cubic air holes. The interaction of a shock wave with a single air hole and a matrix of air holes in PETN, HMX, and TATB has been numerically modeled. The interaction of a shock wave with the density discontinuities, the resulting hot-spot formation and interaction, and the buildup to propagating detonation were computed using three-dimensional numerical Eulerian hydrodynamics with Arrhenius chemical reaction and accurate equations of state according to the hydrodynamic hot-spot model. The basic processes in the desensitization of a heterogeneous explosive by preshocking with a shock pressure too low to cause propagating detonation was numerically modeled. The basic differences between shock sensitive explosives such as PETN or HMX and shock insensitive explosives such as TATB or NQ may be described using the hydrodynamic hot-spot model.
Author: Charles L. Mader
Publisher:
ISBN:
Category : Explosives
Languages : en
Pages : 9
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Book Description
Author:
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Category : Detonation
Languages : en
Pages : 892
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Book Description
Papers presented in this publication cover special problems in the field of energetic materials, particularly detonation phenomena in solids and liquids. General subject areas include shock-to-detonation transition, time resolved chemistry, initiation modeling, deflagration-to-detonation transition, equation of state and equation of state and performance, composites and emulsions, and composites and emulsions/underwater explosives, reaction zone, detonation wave propagation, hot spots, detonation products, chemistry and compositions, and special initiation.
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Category :
Languages : en
Pages : 9
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Book Description
Part of the difficulty in developing physically based models of shock initiation which have genuine predictive capability is that insufficient constraints are often imposed: models are most often applied to very limited data sets which encompass very narrow parameter ranges. Therefore, it seems to be of considerable value to examine the rather large existing shock initiation database to identify trends, similarities, and differences, which predictive models must describe, if they are to be of genuinely utility. In this paper, existing open-literature data for shock initiation of detonation of heterogeneous explosives in one-dimensional geometries have been examined. The intent was to identify -- and where possible, isolate -- physically measurable and controllable parameter effects. Plastic bonded explosives with a variety of different binders and binder concentrations were examined. Data for different pressed explosive particulate materials and particle size distributions were reviewed. Effects of porosity were examined in both binderless and particle-matrix compositions. Effects of inert and reactive binders, and inert and reactive particle fills were examined. In several instances, the calculated data used by the original authors in their analysis was recalculated to correct for discrepancies and errors in the original analysis.
Author: Charles L. Mader
Publisher: CRC Press
ISBN: 142005239X
Category : Technology & Engineering
Languages : en
Pages : 539
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Book Description
Major advances, both in modeling methods and in the computing power required to make those methods viable, have led to major breakthroughs in our ability to model the performance and vulnerability of explosives and propellants. In addition, the development of proton radiography during the last decade has provided researchers with a major new experimental tool for studying explosive and shock wave physics. Problems that were once considered intractable – such as the generation of water cavities, jets, and stems by explosives and projectiles – have now been solved. Numerical Modeling of Explosives and Propellants, Third Edition provides a complete overview of this rapidly emerging field, covering basic reactive fluid dynamics as well as the latest and most complex methods and findings. It also describes and evaluates Russian contributions to the experimental explosive physics database, which only recently have become available. This book comes with downloadable resources that contain— · FORTRAN and executable computer codes that operate under Microsoft® Windows Vista operating system and the OS X operating system for Apple computers · Windows Vista and MAC compatible movies and PowerPoint presentations for each chapter · Explosive and shock wave databases generated at the Los Alamos National Laboratory and the Russian Federal Nuclear Centers Charles Mader’s three-pronged approach – through text, computer programs, and animations – imparts a thorough understanding of new computational methods and experimental measuring techniques, while also providing the tools to put these methods to effective use.
