Numerical Modeling Of Impact Initiation Of High Explosives

We performed continuum mechanics simulations to examine the behavior of energetic materials in Ballistic Chamber Impact (BIC) experiments, using an Arbitrary Lagrangian-Eulerian code (ALE3D). Our simulations revealed that interface friction plays an important role in inducing the formation of shear bands, which result in 'hot spots' for ignition. The temperature localization during BIC impact was found to be significant in materials with high yield strength. In those materials, there are multiple locations inside shear bands can achieve temperatures exceeding the threshold temperature for reaction. In addition, we investigated the relevant parameters influencing the pressure profile of a BIC test by numerical analysis from a simple phenomenological model. To our surprise, we found that the peaks of BIC pressure profiles not only can be a result of multi-center chemical reactions, but can also arise from factors associated apparatus configuration.

Major advances, both in modeling methods and in the computing power required to make those methods viable, have led to major breakthroughs in our ability to model the performance and vulnerability of explosives and propellants. In addition, the development of proton radiography during the last decade has provided researchers with a major new experimental tool for studying explosive and shock wave physics. Problems that were once considered intractable – such as the generation of water cavities, jets, and stems by explosives and projectiles – have now been solved. Numerical Modeling of Explosives and Propellants, Third Edition provides a complete overview of this rapidly emerging field, covering basic reactive fluid dynamics as well as the latest and most complex methods and findings. It also describes and evaluates Russian contributions to the experimental explosive physics database, which only recently have become available. This book comes with downloadable resources that contain— · FORTRAN and executable computer codes that operate under Microsoft® Windows Vista operating system and the OS X operating system for Apple computers · Windows Vista and MAC compatible movies and PowerPoint presentations for each chapter · Explosive and shock wave databases generated at the Los Alamos National Laboratory and the Russian Federal Nuclear Centers Charles Mader’s three-pronged approach – through text, computer programs, and animations – imparts a thorough understanding of new computational methods and experimental measuring techniques, while also providing the tools to put these methods to effective use.

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.

This report contains a numerical algorithm for modeling the detonation and explosion of a heterogeneous mixture of high explosive and small metal particles. The simulation examines a spherical explosive design with a mixture of nitromethane as the high explosive and steel as the metal particles. The algorithm provides a computational model of the detonation and explosion by producing position, velocity, and temperature profiles for the metal particles over time. For the gas phase, the algorithm produces position, velocity, temperature, density, and pressure profiles over time. This is accomplished by taking into account the initial position and velocity profiles for the metal particles, a corresponding particle drag law, appropriate explosive energy and detonation pressure inputs, and a blast wave solution that governs the thermodynamic state of the gas phase. The behavior of the solid particles and gas phase throughout the explosion is simulated by a coupled, two-phase algorithm. The results of the model are compared against experimental data and critiqued on a theoretical level as well. Recommendations and plans for improvements to the algorithm are discussed. This model is intended to provide a sound representation of the detonation as well as insight into the behavior of a heterogeneous explosive.

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Molecular Modeling of the Sensitivities of Energetic Materials, Volume 22 introduces experimental aspects, explores the relationships between sensitivity, molecular structure and crystal structure, discusses insights from numerical simulations, and highlights applications of these approaches to the design of new materials. Providing practical guidelines for implementing predictive models and their application to the search for new compounds, this book is an authoritative guide to an exciting field of research that warrants a computer-aided approach for the investigation and design of safe and powerful explosives or propellants. Much recent effort has been put into modeling sensitivities, with most work focusing on impact sensitivity and leading to a lot of experimental data in this area. Models must therefore be developed to allow evaluation of significant properties from the structure of constitutive molecules. Highlights a range of approaches for computational simulation and the importance of combining them to accurately understand or estimate different parameters Provides an overview of experimental findings and knowledge in a quick and accessible format Presents guidelines to implement sensitivity models using open-source python-related software, thus supporting easy implementation of flexible models and allowing fast assessment of hypotheses

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.