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A Simplistic Approach To The Shock Initiation Of Detonation In Heterogeneous Explosives
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Book Synopsis A Simplistic Approach to the Shock Initiation of Detonation in Heterogeneous Explosives by : Philip M. Howe
Download or read book A Simplistic Approach to the Shock Initiation of Detonation in Heterogeneous Explosives written by Philip M. Howe and published by . This book was released on 1972 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model of the shock initiation of heterogeneous explosives is presented. The model is based upon a 'hotspot' ignition mechanism. Choice of the energy density as the independent variable in the problem permits separation of Hugoniot effects from the buildup process, and leads to a critical condition for initiation which is independent of the loading density. The model is found to be consistent with data from the literature on porous tetryl. (Author).
Book Synopsis On the Characterization and Mechanisms of Shock Initiation in Heterogeneous Explosives by :
Download or read book On the Characterization and Mechanisms of Shock Initiation in Heterogeneous Explosives written by and published by . This book was released on 2002 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a new methodology for fitting the x-t shock initiation trajectories of heterogeneous explosives. The technique is motivated by extended detonation shock dynamics (DSD) theory, which suggests a class of simple phase plane generating functions. We choose one theoretically derived equation as an example, and show that it can fit PBX 9501 and 9502 gas gun data in detail. The fitted function comprises the DSD calibration in the initiation regime, and determines the ordinate values of the Pop plot and inert Hugoniot curves. We describe how the underlying extended DSD assumptions are equivalent to those of certain other initiation models. Finally, we examine a scaling law that assumes all PBX's follow the same x-t trajectory when normalized by their respective c-j reaction zone thicknesses [delta]. This assumption allows [delta] to be estimated from the fit, yielding values similar to other estimates.
Book Synopsis Three Dimensional Modeling of Shock Initiation of Heterogeneous Explosives by :
Download or read book Three Dimensional Modeling of Shock Initiation of Heterogeneous Explosives written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Shock Wave Science and Technology Reference Library, Vol. 5 by : Blaine Asay
Download or read book Shock Wave Science and Technology Reference Library, Vol. 5 written by Blaine Asay and published by Springer Science & Business Media. This book was released on 2009-12-16 with total page 630 pages. Available in PDF, EPUB and Kindle. Book excerpt: Los Alamos National Laboratory is an incredible place. It was conceived and born amidst the most desperate of circumstances. It attracted some of the most brilliant minds, the most innovative entrepreneurs, and the most c- ative tinkerers of that generation. Out of that milieu emerged physics and engineering that beforehand was either unimagined, or thought to be f- tasy. One of the ?elds essentially invented during those years was the science of precision high explosives. Before 1942, explosives were used in munitions and commercial pursuits that demanded proper chemistry and con?nement for the necessary e?ect, but little else. The needs and requirements of the Manhattan project were of a much more precise and speci?c nature. Spatial and temporal speci?cations were reduced from centimeters and milliseconds to micrometers and nanoseconds. New theory and computational tools were required along with a raft of new experimental techniques and novel ways of interpreting the results. Over the next 40 years, the emphasis was on higher energy in smaller packages, more precise initiation schemes, better and safer formulations, and greater accuracy in forecasting performance. Researchers from many institutions began working in the emerging and expanding ?eld. In the midst of all of the work and progress in precision initiation and scienti?c study, in the early 1960s, papers began to appear detailing the ?rst quantitative studies of the transition from de?agration to detonation (DDT), ?rst in cast, then in pressed explosives, and ?nally in propellants.
Book Synopsis Shock Wave Science and Technology Reference Library, Vol.4 by : F. Zhang
Download or read book Shock Wave Science and Technology Reference Library, Vol.4 written by F. Zhang and published by Springer Science & Business Media. This book was released on 2009-06-12 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fourth of several volumes on solids in this series, the six extensive chapters here are more specifically concerned with detonation and shock compression waves in reactive heterogeneous media, including mixtures of solid, liquid and gas phases.
Book Synopsis Trends in Shock Initiation of Heterogeneous Explosives by :
Download or read book Trends in Shock Initiation of Heterogeneous Explosives written by and published by . This book was released on 1998 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Insights Into the Shock Initiation by :
Download or read book Insights Into the Shock Initiation written by and published by . This book was released on 2001 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has long been known that there are fundamental differences between homogeneous and heterogeneous high explosives. The shock initiation behavior of these materials was first described in the literature by Campbell et al, in 1961. Chaiken was also involved in describing this process for liquid nitromethane. Since then, there have been a number of studies which have added considerable incite into the shock initiation/detonation behavior of these materials. We only give a few references here (Refs. 4 - 11) and these should be considered representative; e.g. they do not represent an exhaustive list of references available. Many of these studies were done on homogeneous explosives, most often nitromethane (NM) and include particle velocity gauge measurements, optical temperature measurements, VISAR measurements, as well as streak camera measurements of interfaces. In some cases NM was heterogenized by gelling and adding silica particles. Homogeneous materials are typically liquids or single crystals in which there are a minimal number of physical imperfections (e.g. bubbles or voids) that can cause perturbations in the input shock and the flow behind it. Homogeneous materials viewed with macroscopic probes characteristic of detonation physics experiments appear uniform. Heterogeneous explosives are generally all other types; these are usually pressed, cast, machined, or extruded into the shapes or parts desired. These materials contain imperfections of a variety of types that cause fluid-mechanical irregularities (called hot spots) when a shock or detonation wave passes over them. Such hot spots cause associated space/time fluctuations in the thermodynamic fields (e.g., the pressure or temperature fields) in the material. These thermodynamic variations affect the local chemical-heat-release rate - they produce an average heat-release rate that is a combination of chemistry and mechanics. Hot spots could be the result of voids, shock interactions, jetting, shock impedance mismatches, etc. Shock initiation of homogeneous explosives is due to a thermal explosion that occurs in the material shocked the longest. This reaction produces a reactive wave that grows behind the front and eventually overtakes the front. The reactive wave may grow into what is called a superdetonation before it overtakes the initial shock and settles down to a steady detonation. The shock initiation process in heterogeneous explosives differs a great deal because the hot spots cause early chemical reaction as soon as the shock passing over a region creates them. This causes reactive growth both in and behind the shock front. This leads to a relatively smooth growth of the initiating shock to a detonation, in contrast to the abrupt changes that occur in the homogeneous case. These differences are apparent in both the in-situ reaction wave profiles and the acceleration of the shock front.
Book Synopsis Shock Initiation of Heterogeneous Explosives by : J. E. Reaugh
Download or read book Shock Initiation of Heterogeneous Explosives written by J. E. Reaugh and published by . This book was released on 2004 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Toward Detonation Theory by : Anatoly N. Dremin
Download or read book Toward Detonation Theory written by Anatoly N. Dremin and published by Springer Science & Business Media. This book was released on 1999-06-04 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is known that the Chapman-Jouguet theory of detonation is based on the assumption of an instantaneous and complete transformation of explosives into detonation products in the wave front. Therefore, one should not expect from the theory any interpretations of the detonation limits, such as shock initiation of det onation and kinetic instability and propagation (failure diameter). The Zeldovich-Von Neuman-Doring (ZND) theory of detonation appeared, in fact, as a response to the need for a theory capable of interpreting such limits, and the ZND detonation theory gave qualitative interpretations to the detonation limits. These interpretations were based essentially on the theoretical notion that the mechanism of explosives transformation at detonation is a combustion of a layer of finite thickness of shock-compressed explosive behind the wave shock front with the velocity of the front. However, some experimental findings turned out to be inconsistent with the the ory. A very small change of homogeneous (liquid) explosives detonation velocity with explosive charge diameter near the rather sizable failure diameter is one of the findings. The elucidation of the nature of this finding has led to the discovery of a new phenomenon. This phenomenon has come to be known as the breakdown (BD) of the explosive self-ignition behind the front of shock waves under the effect of rarefaction waves.
Book Synopsis Initiation and Detonation of Heterogeneous High Explosives by : Pier K. Tang
Download or read book Initiation and Detonation of Heterogeneous High Explosives written by Pier K. Tang and published by . This book was released on 1988 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Calculation of Shock-induced Initiation of Detonations. [PBX 9501]. by :
Download or read book Numerical Calculation of Shock-induced Initiation of Detonations. [PBX 9501]. written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of some numerical calculations of the impact of steel cylinders and spheres on the plastic-bonded high explosive PBX 9501 are described. The calculations were carried out by a reactive, multicomponent, two-dimensional, Eulerian hydrodynamic computer code, 2DE. The 2DE computer code is a finite difference code that uses the donor-acceptor-cell method to compute mixed cell fluxes. The mechanism of shock initiation to detonation in heterogeneous explosives is best described as local decomposition at hot spots that are formed by shock interactions with density discontinuities. The liberated energy strengthens the shock so that as it interacts with additional inhomogeneities, hotter hot spots are formed, and more of the explosive is decomposed. The shock wave grows stronger until a detonation begins. This mechanism of initiation has been described numerically by the Forest Fire burn model, which gives the rate of explosive decomposition as a function of local pressure. The parameters in the Forest Fire burn model have been developed from experiments where the induced shock approximates a plane wave and are applied, in this case, to a situation where the induced shock is a divergent wave with curvature that depends on the size and shape of the projectile. The calculated results have been compared with results from experiments involving instrumented mock and live high explosives, with projectiles of varying sizes, shapes, and velocities. We find that there is good agreement between the calculated and experimental data.
Download or read book Detonation written by David J. Edwards and published by . This book was released on 1978 with total page 824 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Detonation written by Wildon Fickett and published by Courier Corporation. This book was released on 2000-01-01 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: This advanced and specialized introduction to the hydrodynamics of detonation offers a theoretical and observational overview. It explores the "simple theory" and experimental tests of the theory; flow in a reactive medium; steady detonation; the nonsteady solution; and the structure of the detonation front. Many simple cases are worked out for illustration. 1979 edition.
Book Synopsis Global Kinetics for the Shock-induced Decomposition of Heterogeneous Explosives by :
Download or read book Global Kinetics for the Shock-induced Decomposition of Heterogeneous Explosives written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Methods were developed to determine empirical rate laws for the shock-induced decomposition of condensed explosives. Pressure-field histories are measured with embedded gauges in plane-wave shock-initiation experiments. A Lagrangian analysis is used to integrate the fluid-dynamic conservation relations, giving the histories of density and energy fields in the reactive flow. A reactant-product equation of state is assumed and a global reaction progress variable and the associated reaction rate are calculated. Correlations of the rate to other state variables provide empirical rate laws, which prove successful in the numerical modeling of numerous initiation and detonation phenomena. Heterogeneous explosive rate laws combining three factors - shock-strength, depletion, and heating - are consistent with many shock-initiation observations and the favored nucleation and growth concept of shock-induced decomposition. The strong correlation to a simple Arrhenius heating factor is remarkable, because the temperature is an average, equilibrium quantity calculated from the equation of state, yet the formation of local high-temperature regions, or hotspots, is the dominant reaction mechanism in heterogeneous explosives. Possible physical implication of the Arrhenius correlation, and other choices for the three rate factors are discussed.
Book Synopsis Initiation and Detonation of Heterogeneous High Explosives a Unified Model by : P.K. Tang
Download or read book Initiation and Detonation of Heterogeneous High Explosives a Unified Model written by P.K. Tang and published by . This book was released on 1977 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Critical Energy for Shock Initiation of Heterogeneous Explosives by : F. E. Walker
Download or read book Critical Energy for Shock Initiation of Heterogeneous Explosives written by F. E. Walker and published by . This book was released on 1968 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Detonation of Condensed Explosives by : Roger Cheret
Download or read book Detonation of Condensed Explosives written by Roger Cheret and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work marks a stage in the evolution of a scientific and technical field which has been developed by the Commissariat a l'Energie Atomique (CEA) over several decades. Many members of the staff of the CEA have won re nown in this field, and their work has brought it to the high degree of excel lence for which it is internationally recognized today. These scientists had to consider every aspect of the field, as it concerned: modeling, which has recourse to fluid thermodynamics, molecular phys ics, and chemistry; numerical evaluation, which relies on mathematical analysis and data processing; and experiments in the firing area, which require specific stress generators and instrumentation. Whilst this book is a testament to the activity and success of staff of the CEA, it also reviews a number ofthe advances made in the discipline. How ever, it is not intended to be an exhaustive account of those advances; it is assumed that the reader can, if desired, consult the standard monographs, and more recent, more specialized works (notably W.C. Davis and W. Fickett, and C.L. Mader). The history of the discipline is interesting in itself, and also as an illustra tion of the causes which lead to progress in a coherent body of scientific work. I should like to make some comments on this progress, of which there is a fascinating summary in the introduction, and which will figure largely throughout the work.
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