Lee Davison – författare

Shock waves produce a wide variety of physical, chemical, mineralogical, and other effects in materials through which they pass. Since the beginning of civili­ zation, shock phenomena have been subjects of continuing interest, speculation, and enquiry. The interdisciplinary aspects of investigations of shock phenomena are especially noteworthy, and these investigations have been pursued by scien­ tists and engineers from a broad range of disciplines. Among the more novel and interesting investigations are those motivated by problems that arise in the Earth and planetary sciences. Such events as meteorite impacts produce the obvious cratering effects seen on the planets and their sat­ ellites. More subtle effects become apparent upon chemical and petrographic examination of the shock-compressed solid material. Shock waves are also prevalent in the larger universe, and have played a prominent role in shaping the solar system as we know it. The material in interstellar gas and dust clouds, comets, etc. , is processed by shock waves, producing important chemical effects, including formation of complex organic molecules. The process of accretion of planets involves impacts of dust particles at relative velocities ranging from a fraction of a millimeter per second to impacts of larger bodies at velocities as great as several tens of kilometers per second. The resulting shock waves cause both chemical and physical changes that are manifest in the bodies involved.

Both experimental and theoretical investigations make it clear that mesoscale materials, that is, materials at scales intermediate between atomic and bulk matter, do not always behave in ways predicted by conventional theories of shock compression. At these scales, shock waves interact with local material properties and microstructure to produce a hierarchy of dissipative structures such as inelastic deformation fields, randomly distributed lattice defects, and residual stresses. A macroscopically steady planar shock wave is neither plane nor steady at the mesoscale. The chapters in this book examine the assumptions underlying our understanding of shock phenomena and present new measurements, calculations, and theories that challenge these assumptions. They address such questions as: - What are the experimental data on mesoscale effects of shocks, and what are the implications? - Can one formulate new mesoscale theories of shock dynamics? - How would new mesoscale theories affect our understanding of shock-induced phase transitions or fracture? - What new computational models will be needed for investigating mesoscale shocks?

Developments in experimental methods are providing an increasingly detailed understanding of shock compression phenomena on the bulk, intermediate, and molecular scales. This third volume in a series of reviews of the curent state of knowledge covers several diverse areas. The first group of chapters addresses fundamental physical and chemical aspects of the response of condensed matter to shock comression: equations of state, molecular-dynamic analysis, deformation of materials, spectroscopic methods. Two further chapters focus on a particular group of materials: ceramics. Another chapter discusses shock-induced reaction of condensed-phase explosives. And a final pair of chapters considers shock phenomena at low stresses from the point of view of continuum mechanics.

Much of the current interest in shock compression of porous solids stems from the desire to bond hard, refractory powders into strong and dense solids. However, while much is known about the effects of shock compression on monolithic materials, the unusual physical and chemical processes that take place when a porous medium is shocked have been little studied thus far. This volume -- with contributions by leading researchers in condensed matter physics, physical chemistry, metallurgy, mechanics, and materials science -- begins to address that gap. The focus is on heterogeneous deformation mechanisms, nonequilibrium thermodynamics, and chemical processes. The contributions discuss such topics as modeling the complex interplay of thermal, mechanical, and chemical processes; experimental data on pore collapse and their interpretation; and synthesis of new materials through shock-induced chemical reactions. By presenting not only the most recent results, but also the open questions that remain, these essays convey the excitement of developing a scientific basis for understanding shock compression of highly porous solids. Topics covered include > Shock Compression Science in Highly Porous Solids > Shock Loading of Porous High Explosives > Continuum Mixture Modeling of Reactive Porous Media > Two-Phase Media Model of Shock Compression with Chemical reaction > Constitutive Modeling of Shock-Induced Reactions in Powder Mixtures > Discrete-element Modeling of Shock Processes in Powders

This volume concerns the fracture and fragmentation of solid materials that occurs when they are subjected to extremes of stress applied at the highest possible rates. The plan for the volume is to address experimental, theoretical, and com­ putational aspects of high-rate dynamic fracture and fragmentation, with emphasis on recent work. We begin with several chapters in which the emphasis falls on experimental methods and observations. These chapters address both macroscopic responses and the microscopic cause of these re­ sponses. This is followed by several chapters emphasizing modeling-the physical explanation and mathematical representation of the observations. Some of the models are deterministic, while others focus on the stochastic aspects of the observations. Often, the ov\!rall objective of investigation of dynamic fracture and fragmentation phenomena is provision of a means for predicting the entire course of an event that begins with a stimulus such as an impact and proceeds through a complicated deformation and fracture pro­ cess that results in disintegration of the body and formation of a rapidly expanding cloud of debris fragments. Analysis of this event usually involves development of a continuum theory and computer code that captures the experimental observations by incorporating models of the important pheno­ mena into a comprehensive description of the deformation and fracture pro­ cess. It is to this task that the work of the last few chapters is devoted.

Shock waves produce a wide variety of physical, chemical, mineralogical, and other effects in materials through which they pass. Since the beginning of civili­ zation, shock phenomena have been subjects of continuing interest, speculation, and enquiry. The interdisciplinary aspects of investigations of shock phenomena are especially noteworthy, and these investigations have been pursued by scien­ tists and engineers from a broad range of disciplines. Among the more novel and interesting investigations are those motivated by problems that arise in the Earth and planetary sciences. Such events as meteorite impacts produce the obvious cratering effects seen on the planets and their sat­ ellites. More subtle effects become apparent upon chemical and petrographic examination of the shock-compressed solid material. Shock waves are also prevalent in the larger universe, and have played a prominent role in shaping the solar system as we know it. The material in interstellar gas and dust clouds, comets, etc. , is processed by shock waves, producing important chemical effects, including formation of complex organic molecules. The process of accretion of planets involves impacts of dust particles at relative velocities ranging from a fraction of a millimeter per second to impacts of larger bodies at velocities as great as several tens of kilometers per second. The resulting shock waves cause both chemical and physical changes that are manifest in the bodies involved.

Both experimental and theoretical investigations make it clear that mesoscale materials, that is, materials at scales intermediate between atomic and bulk matter, do not always behave in ways predicted by conventional theories of shock compression. At these scales, shock waves interact with local material properties and microstructure to produce a hierarchy of dissipative structures such as inelastic deformation fields, randomly distributed lattice defects, and residual stresses. A macroscopically steady planar shock wave is neither plane nor steady at the mesoscale. The chapters in this book examine the assumptions underlying our understanding of shock phenomena and present new measurements, calculations, and theories that challenge these assumptions. They address such questions as: - What are the experimental data on mesoscale effects of shocks, and what are the implications? - Can one formulate new mesoscale theories of shock dynamics? - How would new mesoscale theories affect our understanding of shock-induced phase transitions or fracture? - What new computational models will be needed for investigating mesoscale shocks?

Developments in experimental methods are providing an increasingly detailed understanding of shock compression phenomena on the bulk, intermediate, and molecular scales. This third volume in a series of reviews of the curent state of knowledge covers several diverse areas. The first group of chapters addresses fundamental physical and chemical aspects of the response of condensed matter to shock comression: equations of state, molecular-dynamic analysis, deformation of materials, spectroscopic methods. Two further chapters focus on a particular group of materials: ceramics. Another chapter discusses shock-induced reaction of condensed-phase explosives. And a final pair of chapters considers shock phenomena at low stresses from the point of view of continuum mechanics.

This volume concerns the fracture and fragmentation of solid materials that occurs when they are subjected to extremes of stress applied at the highest possible rates. The plan for the volume is to address experimental, theoretical, and com­ putational aspects of high-rate dynamic fracture and fragmentation, with emphasis on recent work. We begin with several chapters in which the emphasis falls on experimental methods and observations. These chapters address both macroscopic responses and the microscopic cause of these re­ sponses. This is followed by several chapters emphasizing modeling-the physical explanation and mathematical representation of the observations. Some of the models are deterministic, while others focus on the stochastic aspects of the observations. Often, the ov\!rall objective of investigation of dynamic fracture and fragmentation phenomena is provision of a means for predicting the entire course of an event that begins with a stimulus such as an impact and proceeds through a complicated deformation and fracture pro­ cess that results in disintegration of the body and formation of a rapidly expanding cloud of debris fragments. Analysis of this event usually involves development of a continuum theory and computer code that captures the experimental observations by incorporating models of the important pheno­ mena into a comprehensive description of the deformation and fracture pro­ cess. It is to this task that the work of the last few chapters is devoted.

Shock waves produce a wide variety of physical, chemical, mineralogical, and other effects in materials through which they pass. Since the beginning of civili­ zation, shock phenomena have been subjects of continuing interest, speculation, and enquiry. The interdisciplinary aspects of investigations of shock phenomena are especially noteworthy, and these investigations have been pursued by scien­ tists and engineers from a broad range of disciplines. Among the more novel and interesting investigations are those motivated by problems that arise in the Earth and planetary sciences. Such events as meteorite impacts produce the obvious cratering effects seen on the planets and their sat­ ellites. More subtle effects become apparent upon chemical and petrographic examination of the shock-compressed solid material. Shock waves are also prevalent in the larger universe, and have played a prominent role in shaping the solar system as we know it. The material in interstellar gas and dust clouds, comets, etc. , is processed by shock waves, producing important chemical effects, including formation of complex organic molecules. The process of accretion of planets involves impacts of dust particles at relative velocities ranging from a fraction of a millimeter per second to impacts of larger bodies at velocities as great as several tens of kilometers per second. The resulting shock waves cause both chemical and physical changes that are manifest in the bodies involved.

Both experimental and theoretical investigations make it clear that mesoscale materials, that is, materials at scales intermediate between atomic and bulk matter, do not always behave in ways predicted by conventional theories of shock compression. At these scales, shock waves interact with local material properties and microstructure to produce a hierarchy of dissipative structures such as inelastic deformation fields, randomly distributed lattice defects, and residual stresses. A macroscopically steady planar shock wave is neither plane nor steady at the mesoscale. The chapters in this book examine the assumptions underlying our understanding of shock phenomena and present new measurements, calculations, and theories that challenge these assumptions. They address such questions as: - What are the experimental data on mesoscale effects of shocks, and what are the implications? - Can one formulate new mesoscale theories of shock dynamics? - How would new mesoscale theories affect our understanding of shock-induced phase transitions or fracture? - What new computational models will be needed for investigating mesoscale shocks?

Research in the field of shock physics and ballistic impact has always been intimately tied to progress in development of facilities for accelerating projectiles to high velocity and instrumentation for recording impact phenomena. The chapters of this book, written by leading US and European experts, cover a broad range of topics and address researchers concerned with questions of material behaviour under impulsive loading and the equations of state of matter, as well as the design of suitable instrumentation such as gas guns and high-speed diagnostics. Applications include high-speed impact dynamics, the inner composition of planets, syntheses of new materials and materials processing. Among the more technologically oriented applications treated is the testing of the flight characteristics of aeroballistic models and the assessment of impacts in the aerospace industry.

My intent in writing this book is to present an introduction to the thermo- chanical theory required to conduct research and pursue applications of shock physics in solid materials. Emphasis is on the range of moderate compression that can be produced by high-velocity impact or detonation of chemical exp- sives and in which elastoplastic responses are observed and simple equations of state are applicable. In the interest of simplicity, the presentation is restricted to plane waves producing uniaxial deformation. Although applications often - volve complex multidimensional deformation fields it is necessary to begin with the simpler case. This is also the most important case because it is the usual setting of experimental research. The presentation is also restricted to theories of material response that are simple enough to permit illustrative problems to be solved with minimal recourse to numerical analysis. The discussions are set in the context of established continuum-mechanical principles. I have endeavored to define the quantities encountered with some care and to provide equations in several convenient forms and in a way that lends itself to easy reference. Thermodynamic analysis plays an important role in continuum mechanics, and I have included a presentation of aspects of this subject that are particularly relevant to shock physics. The notation adopted is that conventional in expositions of modern continuum mechanics, insofar as possible, and variables are explained as they are encountered. Those experienced in shock physics may find some of the notation unconventional.

My intent in writing this book is to present an introduction to the thermo- chanical theory required to conduct research and pursue applications of shock physics in solid materials. Emphasis is on the range of moderate compression that can be produced by high-velocity impact or detonation of chemical exp- sives and in which elastoplastic responses are observed and simple equations of state are applicable. In the interest of simplicity, the presentation is restricted to plane waves producing uniaxial deformation. Although applications often - volve complex multidimensional deformation fields it is necessary to begin with the simpler case. This is also the most important case because it is the usual setting of experimental research. The presentation is also restricted to theories of material response that are simple enough to permit illustrative problems to be solved with minimal recourse to numerical analysis. The discussions are set in the context of established continuum-mechanical principles. I have endeavored to define the quantities encountered with some care and to provide equations in several convenient forms and in a way that lends itself to easy reference. Thermodynamic analysis plays an important role in continuum mechanics, and I have included a presentation of aspects of this subject that are particularly relevant to shock physics. The notation adopted is that conventional in expositions of modern continuum mechanics, insofar as possible, and variables are explained as they are encountered. Those experienced in shock physics may find some of the notation unconventional.

Research in the field of shock physics and ballistic impact has always been intimately tied to progress in development of facilities for accelerating projectiles to high velocity and instrumentation for recording impact phenomena. The chapters of this book, written by leading US and European experts, cover a broad range of topics and address researchers concerned with questions of material behaviour under impulsive loading and the equations of state of matter, as well as the design of suitable instrumentation such as gas guns and high-speed diagnostics. Applications include high-speed impact dynamics, the inner composition of planets, syntheses of new materials and materials processing. Among the more technologically oriented applications treated is the testing of the flight characteristics of aeroballistic models and the assessment of impacts in the aerospace industry.