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 Energy Research Abstracts written by and published by . This book was released on 1993 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Testing and Modeling of PBX 9591 Shock Initiation written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes an ongoing effort to develop a detonation sensitivity test for PBX-9501 that is suitable for studying pristine and damaged HE. The approach involves testing and comparing the sensitivities of HE pressed to various densities and those of pre-damaged samples with similar porosities. The ultimate objectives are to understand the response of pre-damaged HE to shock impacts and to develop practical computational models for use in system analysis codes for HE safety studies. Computer simulation with the CTH shock physics code is used to aid the experimental design and analyze the test results. In the calculations, initiation and growth or failure of detonation are modeled with the empirical HVRB model. The historical LANL SSGT and LSGT were reviewed and it was determined that a new, modified gap test be developed to satisfy the current requirements. In the new test, the donor/spacer/acceptor assembly is placed in a holder that is designed to work with fixtures for pre-damaging the acceptor sample. CTH simulations were made of the gap test with PBX-9501 samples pressed to three different densities. The calculated sensitivities were validated by test observations. The agreement between the computed and experimental critical gap thicknesses, ranging from 9 to 21 mm under various test conditions, is well within 1 mm. These results show that the numerical modeling is a valuable complement to the experimental efforts in studying and understanding shock initiation of PBX-9501.
Download or read book Modeling The Shock Initiation of PBX 9501 in ALE3D written by and published by . This book was released on 2008 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Initiation of Preshocked High Explosives PBX 9404 PBX 9502 PBX 9501 Monitored with In material Magnetic Gauging written by and published by . This book was released on 1993 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Desensitization of explosives by preshocking is being studied using the well-supported plane shock waves generated by a gas gun. Evolution of the waves in the explosive is monitored using in-material multiple magnetic gauges to measure particle velocity in the lagrangian frame, over ≈ 3[mu]s of run. PBX-9404, PBX-9502 have been studied, at pressures up to 10.5 GPa. A substantial extension of the run to detonation is observed in PBX-9404, with the run beginning approximately at the end of the preshocked region. A reactive wave is observed while the preshock persists in both PBX-9404 and PBX-9501, but evidently does not contribute to the detonation wave or shorten the run to detonation. PBX-9502 is inert at pressures accessible with the gas gun, but serves to clarify the progress of multiple shocks over the off-Hugoniot EOS surface and the shock dynamics of wave coalescence.
Download or read book SHOCK INITIATION EXPERIMENTS ON PBX 9501 EXPLOSIVE AT PRESSURES BELOW 3 GPa WITH ASSOCIATED IGNITION AND GROWTH MODELING written by and published by . This book was released on 2007 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock initiation experiments on the explosive PBX 9501 (95% HMX, 2.5% estane, and 2.5% nitroplasticizer by weight) were performed at pressures below 3 GPa to obtain in-situ pressure gauge data, run-distance-to-detonation thresholds, and Ignition and Growth modeling parameters. Propellant driven gas guns (101 mm and 155 mm) were utilized to initiate the PBX 9501 explosive with manganin piezoresistive pressure gauge packages placed between sample slices. The run-distance-to-detonation points on the Pop-plot for these experiments showed agreement with previously published data and Ignition and Growth modeling parameters were obtained with a good fit to the experimental data. This parameter set will allow accurate code predictions to be calculated for safety scenarios in the low-pressure regime (below 3 GPa) involving PBX 9501 explosive.
Download or read book Shock Waves Science and Technology Library Vol 6 written by F. Zhang and published by Springer Science & Business Media. This book was released on 2012-03-28 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, as a volume of the Shock Wave Science and Technology Reference Library, is primarily concerned with the fundamental theory of detonation physics in gaseous and condensed phase reactive media. The detonation process involves complex chemical reaction and fluid dynamics, accompanied by intricate effects of heat, light, electricity and magnetism - a contemporary research field that has found wide applications in propulsion and power, hazard prevention as well as military engineering. The seven extensive chapters contained in this volume are: - Chemical Equilibrium Detonation (S Bastea and LE Fried) - Steady One-Dimensional Detonations (A Higgins) - Detonation Instability (HD Ng and F Zhang) - Dynamic Parameters of Detonation (AA Vasiliev) - Multi-Scaled Cellular Detonation (D Desbordes and HN Presles) - Condensed Matter Detonation: Theory and Practice (C Tarver) - Theory of Detonation Shock Dynamics (JB Bdzil and DS Stewart) The chapters are thematically interrelated in a systematic descriptive approach, though, each chapter is self-contained and can be read independently from the others. It offers a timely reference of theoretical detonation physics for graduate students as well as professional scientists and engineers.
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.
Download or read book Dynamics of Detonations and Explosions written by and published by AIAA. This book was released on 1991 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Initiation of Heated PBX 9501 Explosive When Exposed to Dynamic Loading written by F. Garcia and published by . This book was released on 2005 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock initiation experiments on the heated PBX9501 explosive (95% HMX, 2.5% estane, and 2.5% nitro-plasticizer by weight) were performed at temperatures 150 C and 180 C to obtain in-situ pressure gauge data. A 101 mm diameter propellant driven gas gun was utilized to initiate the PBX9501 explosive and manganin piezo-resistive pressure gauge packages were placed between sample slices to measure time resolved local pressure histories. The run-distance-to-detonation points on the Pop-plot for these experiments showed the sensitivity of the heated material to shock loading. This work shows that heated PBX-9501 is more shock sensitive than it is at ambient conditions. Proper Ignition and Growth modeling parameters were obtained to fit the experimental data. This parameter set will allow accurate code predictions to be calculated for safety scenarios involving PBX9501 explosives at temperatures close to those at which experiments were performed.
Download or read book Detonation Wave Profile in PBX 9501 written by and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of a CJ-detonation wave in PBX 9501 with a VISAR technique have shown a classical ZND profile for the reaction zone. This is compatible with one-dimensional simulations using realistic equations of state and an Arrhenius reaction rate fit to available data from other experiments. Moreover, the reaction zone width is less than the average grain size in the PBX. In contrast to initiation, which requires hot spots, the reaction rate from the bulk shock temperature is sufficiently high for propagating a detonation wave. This raises questions with burn models used for both ignition and propagation of detonation waves.
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.
Download or read book Shock Compression of Condensed Matter 1991 written by S.C. Schmidt and published by Elsevier. This book was released on 2016-07-29 with total page 1103 pages. Available in PDF, EPUB and Kindle. Book excerpt: The papers collected together in this volume constitute a review of recent research on the response of condensed matter to dynamic high pressures and temperatures. Inlcuded are sections on equations of state, phase transitions, material properties, explosive behavior, measurement techniques, and optical and laser studies. Recent developments in this area such as studies of impact and penetration phenomenology, the development of materials, especially ceramics and molecular dynamics and Monte Carlo simulations are also covered. These latest advances, in addition to the many other results and topics covered by the authors, serve to make this volume the most authoritative source for the shock wave physics community.
Download or read book Shock Initiation Study of PBX 9404 written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Pressure-field histories during the sustained and short-duration shock initiation of PBX-9404 explosive (plastic-bonded HMX) have been determined with embedded Manganin gauges. Numerical integration of the conservation relations and an assumed equation of state are used to obtain the decomposition histories during the initiation process. In both cases, this process is effected by reaction originating near the impact face producing pressure pulses that overtake the shock front and enhance its strength, leading to an abrupt transition to detonation. Correlation of reaction rates to state variables suggest an Arrhenius rate form, modified to include a dependence on shock strength and an induction time. This rate is used in computer simulations of several other initiation experiments on PBX-9404.
Download or read book Numerical Modelling of Detonation Initiation Via Shock Interaction with Multiple Flames written by Georgios Bakalis and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Detonation in gaseous mixtures is a phenomenon of great importance for explosion safety assessment in hydrogen economy and for the development of advanced detonation-based propulsion systems. In practical applications, a detonation is generally caused by a deflagration to detonation transition (DDT) since a smaller amount of energy is required compared to a direct initiation. The key issue of DDT is finding the appropriate mechanisms to rapidly generate the detonation waves with a relatively weak ignition source. The objective of this work is to study numerically the possibility of DDT resulting from shock-multiple cylindrical flames interaction. The numerical setup aims to mimic an array of laminar flames ignited at different spark times, artificially inducing chemical activity to stimulate the coupling between the gasdynamics and the chemical energy release for the transition of deflagration-to-detonation. Using numerical simulations, a number of physical parameters are varied to determine their effect on the run-up distance as well as the time until the onset of detonation occurs, and to explore any scaling relationship among different them. The two-dimensional Navier-Stokes equations with one-step Arrhenius chemistry including the effects of viscosity, thermal conduction and molecular diffusion are used for the simulations. For comparison, simulations with Euler equations are also performed. The finite-volume operator splitting scheme used is based on the 2nd order Godunov-type, Weighted Average Flux (WAF) method with an approximate HLLC Riemann Solver. An Adaptive Mesh Refinement (AMR) technique is used to increase the resolution in areas of interest. The simulation results show that the interaction of the weak shock with the first cylindrical flame demonstrates very good agreement with the results in the literature and that a single weak shock-flame interaction was not enough to cause prompt DDT. However, a high degree of Richtmyer-Meshkov instabilities induced by repeated shock-flame interactions along with shock-boundary interactions generate turbulence that accelerates the flame brush, until eventually a hot spot ignition in the unreacted material develops into a multi-headed detonation wave. The simulation results also show that DDT is sensitive to the simulation method and that certain simulation parameters significantly affect the DDT phenomenon.
