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.
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:
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.
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.
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.
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).
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.
Download or read book Shock Wave Science and Technology Reference Library Vol 5 written by Blaine Asay and published by Springer. This book was released on 2012-05-04 with total page 618 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.
Download or read book Shock Initiation in Heterogenous Explosives written by J.W. Nunziato and published by . This book was released on 1977 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Shock Wave Science and Technology Reference Library Vol 5 written by Blaine Asay and published by Springer. This book was released on 2010-02-05 with total page 618 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.
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.
Download or read book Mechanism of and Particle Size Effects on Shock Sensitivity of Heterogeneous Pressed Explosives Preliminary Assessment of Binderless RDX in Fuze Trains written by and published by . This book was released on 1987 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock initiation of pressed heterogeneous explosives has been reviewed. The key processes of ignition and buildup and their relative importance under sustained and short duration shocks are described. Particle size effects on shock sensitivity are shown to depend on density and shock duration. M50% values from gap tests often increase as particle size decreases. Below a critical particle size M50% then decreases, as predicted from theoretical modelling. This trend was observed here for RDX. Assessment of fine RDX for fuze trains indicated its potential suitability.
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.
Download or read book Dynamics of Heterogeneous Materials written by Vitali Nesterenko and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph deals with the behavior of essentially nonlinear heterogeneous materials in processes occurring under intense dynamic loading, where microstructural effects play the main role. This book is not an introduction to the dynamic behavior of materials, and general information available in other books is not included. The material herein is presented in a form I hope will make it useful not only for researchers working in related areas, but also for graduate students. I used it successfully to teach a course on the dynamic behavior of materials at the University of California, San Diego. Another course well suited to the topic may be nonlinear wave dynamics in solids, especially the part on strongly nonlinear waves. About 100 problems presented in the book at the end of each chapter will help the reader to develop a deeper understanding of the subject. I tried to follow a few rules in writing this book: (1) To focus on strongly nonlinear phenomena where there is no small parameter with respect to the amplitude of disturbance, including solitons, shock waves, and localized shear. (2) To take into account phenomena sensitive to materials structure, where typical space scale of material parameters (particle size, cell size) are presented in the models or are variable in experimental research.
Download or read book Solid Propellant Chemistry Combustion and Motor Interior Ballistics 1999 written by Vigor Yang and published by AIAA. This book was released on 2000 with total page 1038 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Eulerian Hydrocode Analysis of Reactive Micromechanics in the Shock Initiation of Heterogeneous Energetic Material written by Paul Alan Conley and published by . This book was released on 1999 with total page 594 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings written by and published by . This book was released on 1989 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
