Download or read book Shock Initiation Thresholds of Various Explosives written by and published by . This book was released on 2013 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shock Initiation of Bare and Covered Explosives by Projectile Impact written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock initiation thresholds of bare and covered PBX-9404 and an HMX/TATB explosive called RX-26-AF were measured. The shocks were produced by the impact of flat-nosed and round-nosed steel projectiles in the velocity range of 0.5 to 2.2 km/s. Three types of coverings were used, 2 or 6 mm of tantalum, and a composite of aluminum and plastic. An Eulerian code containing material-strength and explosive-initiation models was used to evaluate our ability to calculate the shock initiation thresholds. These code calculations agreed well with the flat-nosed experimental data, but not so well with the round-nosed data.

Download or read book The Hydrodynamic Hot Spot and Shock Initiation of Homogeneous Explosives written by Charles L. Mader and published by . This book was released on 1962 with total page 48 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 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 Initiation of Reaction in Explosives by Shocks written by T. P Liddiard (Jr) and published by . This book was released on 1965 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several solid high explosives are subjected to shocks of moderate amplitude, 10-50 kb. In general, these shocks are strong enough to cause chemical reaction, but not full detonation. Examples (photographic sequences) are shown of the acceptor response of several explosives at various entering shock pressures (stresses). The stress in the acceptor which just produces detectable reaction is determined from a plot of the break-out time of gaseous products of reaction from the acceptor as a function of the entering stress. The stress at which detonation is just produced in the acceptors is also determined. Threshold values for burning and for detonation also are obtained from graphs of the velocity of the acceptor undergoing chemical reaction as a function of the entering stress. The thresholds for burning and for detonation are compared with the 50% firing stresses obtained with the standardized gap test.

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 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various data from the literature on shock initiation were examined to ascertain the relative importance of effects of porosity, particle size, and binder composition upon explosives initiation behavior. Both pure and composite explosives were examined. It was found that the main influence of porosity is manifested through changes in Hugoniot relations. The threshold for initiation was found to be insensitive to porosity, except at very low porosities. The buildup process was found to be weakly dependent upon porosity. Particle size effects were found to depend sensitively upon the nature of the particulates. For inert particles embedded in a reactive continuum, initiation is strongly specific surface area dependent. For HMX particles embedded in inert or reactive continua, particle effects are subtle. Sparse data indicate that binder composition has a small but significant effect upon threshold velocities.

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 Shock Waves in Condensed Matter 1983 written by J.R. Asay and published by Elsevier. This book was released on 2012-12-02 with total page 673 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock Waves in Condensed Matter – 1983 covers the proceedings of the American Physical Society Topical Conference, held in Santa Fe, New Mexico on July 18-21, 1983. The book focuses on the response of matter to dynamic high pressure and temperature. The selection first elaborates on the review of theoretical calculations of phase transitions and comparisons with experimental results; theoretical and experimental studies of shock-compressed benzene and polybutene; and theory of the iron equation of state and melting curve to very high pressures. The text then ponders on nonhydrostatic effects in stress-wave induced phase transformation of calcite; Bauschinger effect model suitable for use in large computer codes; and strain rate sensitivity prediction for porous bed compaction. The manuscript takes a look at flaw nucleation and energetics of dynamic fragmentation, shock loading behavior of fused quartz, and aluminum damage simulation in high-velocity impact. Shock wave diagnostics by time-resolved infrared radiometry and non-linear Raman spectroscopy; Raman scattering temperature measurement behind a shock wave; and experiments and simulation on laser-driven shock wave evolution in aluminum targets are also discussed. The selection is a dependable reference for scientists and readers interested in the response of matter when exposed to dynamic high pressure and temperature.

Download or read book Temperature dependent Shock Initiation of LX 17 Explosive written by and published by . This book was released on 1995 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: LX-17 samples, heated to temperatures up to 250 C, were impacted by 3 to 10-mm-wide, 50.8-mm-long strips of 0.13-mm-thick Kapton polyimide film at velocities up to 7.7 km/s. The Kapton strips were laminated onto a thin aluminum bridge foil and were launched to the desired velocity by discharging a capacitor bank through the foil, causing the foil to explode. The LX-17 samples were confined in a steel holder and heated in an oven to the desired temperature. After the capacitor bank was charged, the LX-17 sample in its steel holder was remotely drawn out of the oven on rails and positioned over the bridge-foil/Kapton-strip laminate. When the sample was in position, the bank was discharged, launching the Kapton strip against the LX-17 surface. The shock initiation threshold was measured for 3, 7, and 10-mm-wide strips at room temperature, 200 C and 250 C. The authors found a significant reduction in the velocity threshold and in the critical area for initiation when the samples were heated. The authors compare the results with the earlier data of Bloom, who measured the initiation threshold of LX-17 over the density range 1.8--1.91 g/cm3 at room temperature and -54 C. LX-17 has a large coefficient of thermal expansion, as reported by Urtiew, et al., which reduces its density significantly t elevated temperatures. They find that the change of shock initiation threshold with temperature is consistent with the change in sample density, using the relation between threshold and density reported by Bloom.

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 Shock Initiation and Detonation Properties of Homogeneous Explosives written by and published by . This book was released on 1974 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Criteria for Shock Initiation of High Explosives written by Bruce P. Kirk and published by . This book was released on 1971 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book New Technique for Determining the Shock Initiation Sensitivity of Explosives written by and published by . This book was released on 1977 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A new technique for determining the shock initiation sensitivity of explosives is described. It involves a flyer plate impinging upon the test explosive to induce initiation of detonation. An electrically exploded foil propels the flyer plate, which is a thin disk of polyimide (Kapton) 1 mm in dia; the charging voltage applied to the capacitor discharge fireset is used to preselect the desired velocity of the flyer plate. Its impact on the explosive introduces a rectangular pressure plus, P, whose amplitude depends on the velocity of the flyer at impact and the shock properties of the flyer and the explosive. The duration of the pulse, tau, depends upon flyer thickness. The test objective is to establish the critical pressure at a given duration which results in a 50 percent probability of detonating the explosive. The data, presented in a log P-log tau plot, generate a demarcation line between detonation and nondetonation regions. In the experiments the impact pressure was in the range of 1 to 10 GPa and the duration from 0.039 to 0.070 .mu.s. Pentaery-thritol tetranitrate (PETN) and three forms of hexanitrostilbene (HNS) were evaluated. For both materials and variation of the threshold stimulus with initial compaction density was measured. Since a single flyer thickness was used in all but one of the experiments, the data for each explosive give only a single value (P, tau) on the demarcation line which separates detonation from nondetonation. Additional tests with other flyer thicknesses are needed to define this line over a broad range of tau. This new technique employs conventional laboratory equipment and a simple, inexpensive test device. The initiation stimulus may be expressed in a clearly defined form which is directly applicable to safety or performance computations.

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 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 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 A Frictional Work Predictive Method for the Initiation of Solid High Explosives from Low pressure Impacts written by and published by . This book was released on 1993 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of these tests was to provide information that would aid in the prediction of HE response in accident situations where the initiating stimulus was less than that required for direct shock initiation. Before these tests were run, a prediction of threshold impact velocity was made (70m/s) using a rough average of previously reported threshold factional work from skid tests (1 cal/cm2) and the experimental value for coefficient of friction of 0.5(") measured in the same tests for PBX-9404. The actual testing proved the threshold impact velocity to be much less, and the pretest prediction was not only wrong, it was not conservative. This work presents a methodology for more accurately predicting the reaction threshold for HE involved in an accident such as an airplane crash or a severe land transportation accident. The main focus of this work is on LX-10-1 (94.5% 5.5% Viton A binder, density 1.86g/cm3). Additional work was done on LX-17 (92.5% TATB, 7.5% KelF binder, density 1.90g/cm3), a very insensitive explosive. The explicit two-dimensional finite element code, DYNA2D, was used to model the tests and predict the HE response. The finite element mesh of the projectile and target were generated using MAZE. The post-processing of the DYNA2D analysis was done with ORION.