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Influence of shockwave obliquity on deformation twin formation in Ta

Description: Energetic loading subjects a material to a 'Taylor wave' (triangular wave) loading profile that experiences an evolving balance of hydrostatic (spherical) and deviatoric stresses. While much has been learned over the past five decades concerning the propensity of deformation twinning in samples shockloaded using 'square-topped' profiles as a function of peak stress, achieved most commonly via flyer plate loading, less is known concerning twinning propensity during non-I-dimensional sweeping detonation wave loading. Systematic small-scale energetically-driven shock loading experiments were conducted on Ta samples shock loaded with PEFN that was edge detonated. Deformation twinning was quantified in post-mortem samples as a function of detonation geometry and radial position. In the edge detonated loading geometry examined in this paper, the average volume fraction of deformation twins was observed to drastically increase with increasing shock obliquity. The results of this study are discussed in light of the formation mechanisms of deformation twins, previous literature studies of twinning in shocked materials, and modeling of the effects of shock obliquity on the evolution of the stress tensor during shock loading.
Date: January 1, 2009
Creator: Gray Iii, George T; Livescu, V; Cerreta, E K; Mason, T A; Maudlin, P J & Bingert, J F
Partner: UNT Libraries Government Documents Department

Analysis of cook-off using logic models

Description: Developing a predictive model for cook-off is a difficult task. Recent experiments with PBX 9501 have shown that under certain heating and confinement conditions it is possible to generate large regions of almost uniform temperature in an explosive. Such regions react violently in a coherent fashion and may have the potential to produce unusually symmetric detonation waves in certain geometries. These results were unexpected before the experiments and have generated considerable additional activity both experimentally and in model building. At this time, there is no unambiguous explanation for the observed behavior, and therefore, there is a considerable number of fledgling models in existence. These models suggest varying and possibly contradictory mechanisms to explain the thermal profiles and wave behavior data. In this paper, we present an approach to model development for cook-off of PBX 9501 based on logic models called process trees. Process trees are well-suited to the task of describing causal sequences and delineating alternative descriptions of observed phenomenology. Therefore, they provide a valuable basis for constructing physical models and integrating them.
Date: January 1, 2001
Creator: Luck, L. B.
Partner: UNT Libraries Government Documents Department

Orientation-dependent shock response of explosive crystals

Description: Some orientations of PETN crystals have anomalously high shock initiation sensitivity around 4 to 5 GPa. Results of a series of laser interferometry experiments at 4.2 GPa show that this is associated with an elastic-plastic, two-wave structure with large elastic precursors. Implications for the initiation mechanism in single crystals is discussed. Initial work on beta phase, monoclinic HMX is also described.
Date: September 1, 1995
Creator: Dick, J.J.
Partner: UNT Libraries Government Documents Department

SALUT: Containment data report

Description: The SALUT event was detonated in hole U20ak of the Nevada Test Site as indicated in Fig. 1.1. The device had a depth-of-burial of 607 m in the Scrugham Peak rhyolite of Area 20, about 15 m above the standing water level (SWL), as shown in Figures 1.2 and 1.3. Stemming of the 2.44 m diameter emplacement hole followed the plan shown in Fig. 1.4. A log of the stemming operations was maintained by Holmes & Narver. Detonation time was 08:15 PDT on June 12, 1985 and about 10 hours, 17 minutes later a sub-surface collapse progressed upwards to a depth between 200 and 270 m. No radiation arrivals were detected in the emplacement hole and the SALUT containment was considered successful.
Date: May 1, 1995
Creator: Stubbs, T. & Heinle, R.
Partner: UNT Libraries Government Documents Department

Shock initiation of 1,3,3-trinitroazetidine (TNAZ)

Description: The shock sensitivity of the pressed solid explosive 1,3,3-trinitroazetidine (TNAZ) was determined using the embedded manganin pressure gauge technique. At an initial pressure of 1.3 GPa, pressure buildup (exothermic reaction) was observed after ten {mu}s. At 2 GPa, TNAZ reacted rapidly and transitioned to detonation in approximately 13 mm. At 3.6 GPa, detonation occurred in less than 6 mm of shock propagation. Thus, pure TNAZ is more shock sensitive than HMX-based explosives but less shock sensitive than PETN-based explosives. The shocked TNAZ exhibited little reaction directly behind the shock front, followed by an extremely rapid reaction. This reaction caused both a detonation wave and a retonation wave in the partially decomposed TNAZ. An Ignition and Growth reactive model for TNAZ was developed to help understand this complex initiation phenomenon.
Date: July 19, 1995
Creator: Simpson, R.L.; Urtiew, P.A. & Tarver, C.M.
Partner: UNT Libraries Government Documents Department

Progress in measuring detonation wave profiles in PBX9501

Description: The authors have measured detonation wave profiles in PBX9501 (95 wt% HMX and 5 wt% binders) using VISAR. Planar detonations were produced by impacting the explosive with projectiles launched in a 72 mm bore gas gun. Particle velocity wave profiles were measured at the explosive/window interface using two VISARs with different fringe constants. Windows with very thin vapor deposited aluminum mirrors were used for all experiments. PMMA windows provided an undermatch, and LiF (Lithium Fluoride) windows provided an overmatch to the explosive, reacted and unreacted. While the present experiments do not have adequate time resolution to adequately resolve the ZND spike condition, they do constrain it to lie between 38.7 and 53.4 Gpa or 2.4 and 3.3 km/s. Accurate knowledge of the CJ state places the reaction zone length at 35 {+-} 12 ns ({approx} 0.3 mm). The present experiments do not show any effect of the window on the reaction zone; both window materials result in the same reaction zone length.
Date: December 31, 1998
Creator: Gustavsen, R.L.; Sheffield, S.A. & Alcon, R.R.
Partner: UNT Libraries Government Documents Department

W-76 PBX 9501 cylinder tests

Description: Five 1-inch diameter cylinder tests were fired in support of the W-76 high explosive surveillance program. Three of the tests used baseline material, and two used stockpile return material. The diagnostics were electrical pins to measure detonation velocity and a streak camera to measure wall motion. The data was analyzed for cylinder energy, Gurney energy, and detonation velocity. The results of all three measures were consistent for all five tests, to within the experimental accuracy.
Date: July 1, 1998
Creator: Hill, L.G. & Catanach, R.A.
Partner: UNT Libraries Government Documents Department

Statistical analysis of high explosive detonation data

Description: This study investigates the detonation behavior of two different high explosive compounds, PBX 9404 and PBX 9502. One reason these two high explosives were selected is because data is abundant relative to other types of high explosives. Statistical analysis of data for two different high explosives was performed. The goal of the analysis was to determine how the probability of detonation varies for different run lengths and pressures.
Date: May 10, 1998
Partner: UNT Libraries Government Documents Department

Detonation front theories: Using high-resolution DNS to define extended asymptotic scalings and models

Description: When the detonation reaction-zone length, {eta}{sub r}, is short in comparison to the dimensions of the explosive piece being burnt, the detonation can be viewed as a propagating surface (or front) separating burnt from unburnt material. If the product of the shock curvature, {kappa} and {eta}{sub r} is small (i.e., the scaled shock curvature satisfies the {vert_bar}{kappa}{eta}{sub r}{vert_bar} {much_lt} 1), then to leading order the speed of this surface, D{sub n}({kappa}) is a function only of {kappa}. It is in this limit that the original version of the asymptotic detonation front theory, called detonation shock dynamics (DSD), derives the propagation law, D{sub n}({kappa}). In this lecture, the authors compare D{sub n}({kappa})-theory with the results obtained with high-resolution direct numerical simulations (DNS), and then use the DNS results to guide the development of extended asymptotic front theories with enhanced predictive capabilities.
Date: February 1, 1998
Creator: Aslam, T.D. & Bdzil, J.B.
Partner: UNT Libraries Government Documents Department

PROTON RADIOGRAPHY EXAMINATION OF UNBURNED REGIONS IN PBX 9502 CORNER TURNING EXPERIMENTS

Description: PBX 9502 Corner Turning Experiments have been used with various diagnostics techniques to study detonation wave propagation and the boosting of the insensitive explosive. In this work, the uninitiated region of the corner turning experiment is examined using Proton Radiography. Seven transmission radiographs obtained on the same experiment are used to map out the undetonated regions on each of three different experiments. The results show regions of high-density material, a few percent larger than initial explosive density. These regions persist at nearly this density while surrounding material, which has reacted, is released as expected. Calculations using Detonation Shock Dynamics are used to examine the situations that lead to the undetonated regions.
Date: June 1, 2001
Creator: FERM, E. N.; MORRIS, C. L. & AL, ET
Partner: UNT Libraries Government Documents Department

Discrete approximations of detonation flows with structured detonation reaction zones by discontinuous front models: A program burn algorithm based on detonation shock dynamics

Description: In the design of explosive systems the generic problem that one must consider is the propagation of a well-developed detonation wave sweeping through an explosive charge with a complex shape. At a given instant of time the lead detonation shock is a surface that occupies a region of the explosive and has a dimension that is characteristic of the explosive device, typically on the scale of meters. The detonation shock is powered by a detonation reaction zone, sitting immediately behind the shock, which is on the scale of 1 millimeter or less. Thus, the ratio of the reaction zone thickness to the device dimension is of the order of 1/1,000 or less. This scale disparity can lead to great difficulties in computing three-dimensional detonation dynamics. An attack on the dilemma for the computation of detonation systems has lead to the invention of sub-scale models for a propagating detonation front that they refer to herein as program burn models. The program burn model seeks not to resolve the fine scale of the reaction zone in the sense of a DNS simulation. The goal of a program burn simulation is to resolve the hydrodynamics in the inert product gases on a grid much coarser than that required to resolve a physical reaction zone. The authors first show that traditional program burn algorithms for detonation hydrocodes used for explosive design are inconsistent and yield incorrect shock dynamic behavior. To overcome these inconsistencies, they are developing a new class of program burn models based on detonation shock dynamic (DSD) theory. It is hoped that this new class will yield a consistent and robust algorithm which reflects the correct shock dynamic behavior.
Date: February 2, 1999
Creator: Bdzil, J.B.; Jackson, T.L. & Stewart, D.S.
Partner: UNT Libraries Government Documents Department

Reactive flow model development for PBXW-126 using modern nonlinear optimization methods

Description: The initiation and detonation behavior of PBXW-126 has been characterized and is described. PBXW-126 is a composite explosive consisting of approximately equal amounts of RDX, AP, AL, and NTO with a polyurethane binder. The three term ignition and growth of reaction model parameters (ignition + two growth terms) have been found using nonlinear optimization methods to determine the {open_quotes}best{close_quotes} set of model parameters. The ignition term treats the initiation of up to 0.5% of the RDX The first growth term in the model treats the RDX growth of reaction up to 20% reacted. The second growth term treats the subsequent growth of reaction of the remaining AP/AL/NTO. The unreacted equation of state (EOS) was determined from the wave profiles of embedded gauge tests while the JWL product EOS was determined from cylinder expansion test results. The nonlinear optimization code, NLQPEB/GLO, was used to determine the {open_quotes}best{close_quotes} set of coefficients for the three term Lee-Tarver ignition and growth of reaction model.
Date: August 1, 1995
Creator: Murphy, M.J.; Simpson, R.L. & Urtiew, P.A.
Partner: UNT Libraries Government Documents Department

Combustion of TNT products in a confined explosion

Description: The effects of turbulent combustion of detonation products gases in a confined explosion are explored via laboratory experiments and high-resolution numerical simulations. The expanded products from the detonation of a TNT charge are rich in C and CO, which act as a fuel. When these hot gases mix with air, they are oxidized to CO2--thereby releasing 2482 Cal/g in addition to the 1093 Cal/g deposited by the detonation wave. In this case, the exothermic power is controlled by the turbulent mixing rate, rather than by chemistry. A kinetic law of turbulent combustion is suggested for this process. Pressure histories from the numerical simulations were in good agreement with the experimental measurements--demonstrating that the numerical model contains the fundamental mechanism that controls the exothermic process.
Date: June 18, 1999
Creator: Ferguson, R E; Kuhl, A L & Oppenheim, A K
Partner: UNT Libraries Government Documents Department

Fast rise-time, fiber optic pin

Description: A reliable, simple fast-rise-time diagnostic has been developed for measuring the breakout time of the detonation wave in a detonating high explosive. The intrinsic rise time of the signals generated is less than one nanosecond. The technique, called FAT (<i>F</i>iber <i>A</i>rrival <i>T</i>ime), consists of an optical fiber with one end coated with ~1500 Å Aluminum. The coated end is placed in intimate contact with the surface of the explosive. The detonation wave interacting with the Al surface causes a prompt flash of light which is recorded at the output end of the fiber. The active area of the FAT probe end is 100 µm in diameter and centered to within ±10 µm also giving excellent spatial precision. When used in this mode, FAT overcomes difficulties of electronic and past fiber optic pins. When looking at a flyer plate arrival the time response appears to be a function of the metal plate velocity.
Date: May 12, 1998
Creator: Roeske, F
Partner: UNT Libraries Government Documents Department

Nonequilibrium detonation of composite explosives

Description: The effect of nonequilibrium diffusional flow on detonation velocities in composite explosives is examined. Detonation conditions are derived for complete equilibrium, temperature and pressure equilibrium, and two forms of pressure equilibrium. Partial equilibria are associated with systems which have not had sufficient time for transport to smooth out the gradients between spatially separate regions. The nonequilibrium detonation conditions are implemented in the CHEQ equation of state code. We show that the detonation velocity decreases as the non-chemical degrees of freedom of the explosive are allowed to equilibrate. It is only when the chemical degrees of freedom are allowed to equilibrate that the detonation velocity increases.
Date: July 1, 1997
Creator: Nichols III, A.L.
Partner: UNT Libraries Government Documents Department

Slag Characterization and Removal Using Pulse Detonation for Coal Gasification.

Description: The research activities performed in this quarter (reporting period: 07/01/97- 09/30/97) are summarized as follows: The research activities concentrated on (1) Design, development, and fabrication of a 9 positions (3x3 matrix form) fixture (2) Preparation of the test parameters (3) Multi-cycle detonation wave slag removal test (4) Partial analysis of the test results and (5) Interpretation and discussion of the test results.
Date: September 25, 1997
Creator: Hugue, Z; Mei, D.; Biney, P.O.; Zhou, J. & Ali, M.R.
Partner: UNT Libraries Government Documents Department

Kinetic information from detonation front curvature

Description: The time constants for time-dependent modeling may be estimated from reaction zone lengths, which are obtained from two sources One is detonation front curvature, where the edge lag is close to being a direct measure The other is the Size Effect, where the detonation velocity decreases with decreasing radius as energy is lost to the cylinder edge A simple theory that interlocks the two effects is given A differential equation for energy flow in the front is used, the front is described by quadratic and sixth-power radius terms The quadratic curvature comes from a constant power source of energy moving sideways to the walls Near the walls, the this energy rises to the total energy of detonation and produces the sixth-power term The presence of defects acting on a short reaction zone can eliminate the quadratic part while leaving the wall portion of the cuvature A collection of TNT data shows that the reaction zone increases with both the radius and the void fraction
Date: June 15, 1998
Creator: Souers, P. C., LLNL
Partner: UNT Libraries Government Documents Department

RESPONSE OF ALUMINUM SPHERES IN SITU TO DETONATION

Description: Time sequence x-ray imaging was utilized to determine the response of aluminum spheres embedded in a detonating high-explosive cylinder. The size of these spheres ranged from 3/8-inch to 1/32-inch in diameter. These experiments directly observed the response of the spheres as a function of time after interaction with the detonation wave. As the spheres are entrained in the post-detonation flow field, they are accelerating and their velocity profile is complicated, but can be determined from the radiography. Using the aluminum spheres as tracers, radial velocities of order 1.6 mm/us and horizontal velocities of order 0.08 mm/us were measured at early times post detonation. In terms of response, these data show that the largest sphere deforms and fractures post detonation. The intermediate size spheres suffer negligible deformation, but appear to ablate post detonation. Post detonation, the smallest spheres either react, mechanically disintegrate, atomize as a liquid or some combination of these.
Date: March 26, 2010
Creator: Molitoris, J D; Garza, R G; Tringe, J W; Batteux, J D; Wong, B M; Villafana, R J et al.
Partner: UNT Libraries Government Documents Department

Detonation propagation in a high loss configuration

Description: This work presents an experimental study of detonation wave propagation in tubes with inner diameters (ID) comparable to the mixture cell size. Propane-oxygen mixtures were used in two test section tubes with inner diameters of 1.27 mm and 6.35 mm. For both test sections, the initial pressure of stoichiometric mixtures was varied to determine the effect on detonation propagation. For the 6.35 mm tube, the equivalence ratio {phi} (where the mixture was {phi} C{sub 3}H{sub 8} + 50{sub 2}) was also varied. Detonations were found to propagate in mixtures with cell sizes as large as five times the diameter of the tube. However, under these conditions, significant losses were observed, resulting in wave propagation velocities as slow as 40% of the CJ velocity U{sub CJ}. A review of relevant literature is presented, followed by experimental details and data. Observed velocity deficits are predicted using models that account for boundary layer growth inside detonation waves.
Date: January 1, 2009
Creator: Jackson, Scott I & Shepherd, Joseph E
Partner: UNT Libraries Government Documents Department

Diameter effect curve and detonation front curvature measurements for ANFO

Description: Diameter effect and front curvature measurements are reported for rate stick experiments on commercially available prilled ANFO (ammonium-nitrate/fuel-oil) at ambient temperature. The shots were fired in paper tubes so as to provide minimal confinement. Diameters ranged from 77 mm ({approx} failure diameter) to 205 mm, with the tube length being ten diameters in all cases. Each detonation wave shape was fit with an analytic form, from which the local normal velocity Dn, and local total curvature {kappa}, were generated as a function of radius R, then plotted parametrically to generate a Dn({kappa}) function. The observed behavior deviates substantially from that of previous explosives, for which curves for different diameters overlay well for small {kappa} but diverge for large {kappa}, and for which {kappa} increases monotonically with R. For ANFO, we find that Dn({kappa}) curves for individual sticks (1) show little or no overlap--with smaller sticks lying to the right of larger ones, (2) exhibit a large velocity deficit with little {kappa} variation, and (3) reach a peak {kappa} at an intermediate R.
Date: January 1, 2001
Creator: Catanach, R. A. (Richard A.) & Hill, L. G. (Larry G.)
Partner: UNT Libraries Government Documents Department

Insights into the shock initiation/detonation of homogeneous and heterogeneous HE

Description: 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 ...
Date: January 1, 2001
Creator: Gustavsen, R. L. (Richard L.); Hill, L. G. (Larry G.); Engelke, R. P. (Raymond P.); Alcon, R. R. (Robert R.); Davis, L. L. (Lloyd L.) & Sheffield, S. A. (Stephen A.)
Partner: UNT Libraries Government Documents Department

Proton radiography examination of unburned regions in PBX 9502 corner turning experiments

Description: PBX 9502 Corner Turning Experiments have been used with various diagnostics techniques to study detonation wave propagation and the boosting of the insensitive explosive. In this work, the uninitiated region of the corner turning experiment is examined using Proton Radiography. Seven transmission radiographs obtained on the same experiment are used to map out the undetonated regions on each of three different experiments. The results show regions of high-density material, a few percent larger than initial explosive density. These regions persist at nearly this density while surrounding material, which has reacted, is released as expected. Calculations using Detonation Shock Dynamics are used to examine the situations that lead to the undetonated regions.
Date: June 1, 2001
Creator: Ferm, E. N. (Eric N.); Morris, C. L. (Christopher L.); Quintana, J. P. (John P.); Pazuchanics, P. (Peter); Stacy, H. L. (Howard L.); Zumbro, J. D. (John D.) et al.
Partner: UNT Libraries Government Documents Department

The Piecewise Linear Reactive Flow Rate Model

Description: Conclusions are: (1) Early calibrations of the Piece Wise Linear reactive flow model have shown that it allows for very accurate agreement with data for a broad range of detonation wave strengths. (2) The ability to vary the rate at specific pressures has shown that corner turning involves competition between the strong wave that travels roughly in a straight line and growth at low pressure of a new wave that turns corners sharply. (3) The inclusion of a low pressure de-sensitization rate is essential to preserving the dead zone at large times as is observed.
Date: July 22, 2005
Creator: Vitello, P & Souers, P C
Partner: UNT Libraries Government Documents Department