Numerical Modeling of Insensitive High-explosives Initiation


Book Description

The initiation of propagating, diverging detonation is usually accomplished by small conventional initiators. As the explosive to be initiated becomes more shock insensitive, the initators must have larger diameters to be effective. Very shock-insensitive explosives have required initiators larger than 2.5 cm. We have numerically examined the process of initiation of propagating detonation as a function of the shock sensitivity of the explosive using the two-dimensional Lagrangian reactive hydrodynamic code 2DL and the Forest Fire rate to describe the shock initiation process of heterogeneous explosives. The initiation of propagating detonation in shock-insenstive explosives containing triamino trinitrobenzene results in large regions of partially decomposed explosive even when initiated by large initiators. The process has been observed experimentally and reproduced numerically.




Numerical Calculation of Shock-induced Initiation of Detonations. [PBX 9501].


Book Description

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.




Detonation Phenomena of Condensed Explosives


Book Description

This book presents fundamental theory of shock and detonation waves as well as selected studies in detonation research in Japan, contributed by selected experts in safety research on explosives, development of industrial explosives, and application of explosives. It also reports detonation research in Japan featuring industrial explosives that include ammonium nitrate-based explosives and liquid explosives. Intended as a monographic-style book, it consistently uses technical terms and symbols and creates organic links between various detonation phenomena in application of explosives, fundamental theory of detonation waves, measurement methods, and individual studies. Among other features, the book presents a historical perspective of shock wave and detonation research in Japan, pedagogical materials for young researchers in detonation physics, and an introduction to works in Japan, including equations of state, which are worthy of attention but about which very little is known internationally. Further, the concise pedagogical chapters also characterize this book as a primer of detonation of condensed explosives and help readers start their own research.







Numerical Modeling of Shock-sensitivity Experiments


Book Description

The Forest Fire rate model of shock initiation of heterogeneous explosives has been used to study several experiments commonly performed to measure the sensitivity of explosives to shock and to study initiation by explosive-formed jets. The minimum priming charge test, the gap test, the shotgun test, sympathetic detonation, and jet initiation have been modeled numerically using the Forest Fire rate in the reactive hydrodynamic codes SIN and 2DE.










Assessment of Safety and Risk with a Microscopic Model of Detonation


Book Description

This unique book is a store of less well-known explosion anddetonation phenomena, including also data and experiences related tosafety risks. It highlights the shortcomings of the currentengineering codes based on a classical plane wave model of thephenomenon, and why these tools must fail. For the first time all the explosion phenomena are described in termsof proper assemblages of hot spots, which emit pressure waves andassociated near field terms in flow. Not all of the approaches arenew. Some even date back to the 19th century or earlier.. What is newis the application of these approaches to explosion phenomena. Inorder to make these tools easily available to the current detonationphysicist, basic acoustics is therefore also addressed. Whereas the current plane wave, homogeneous flow detonation physicsis an excellent engineering tool for numerical predictions undergiven conditions, the multi-hot-spot-model is an additional tool foranalyzing phenomena that cannot be explained by classicalcalculations. The real benefit comes from being able to understand,without any artificial assumptions, the whole phenomenology ofdetonations and explosions. By specifying pressure generatingmechanisms, one is able to see that the current treatment of thedetonics of energetic materials is only a very special - but powerful- case of explosion events and hazards. It becomes clear thatphysical explosions must be taken into account in any safetyconsiderations. In these terms it is easy to understand why evenliquid carbon dioxide and inert silo materials can explode. A unique collection of unexpected events, which might surprise evenspecialists, has resulted from the evaluation of the model. Thereforethis book is valuable for each explosion and safety scientist for theunderstanding and forecasting of unwanted events. The text mainlyaddresses the next generation of explosion and detonation scientists,with the goal of promoting the science of detonation on a newphysical basis. For this reason gaps in current knowledge are alsoaddressed. The science of explosions is not fully mature, but isstill in its beginning - and the tools necessary for furthering theunderstanding of these phenomena have been with us for centuries.




Shock Wave Science and Technology Reference Library, Vol. 5


Book Description

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.