Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session R6: TM Continuum Modeling I |
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Chair: Amanual Teweldebrhan, Lawrence Livermore National Laboratory Room: Cascade II |
Wednesday, July 10, 2013 3:30PM - 4:00PM |
R6.00001: Equation of State for Shock Compression of High Distension Solids Invited Speaker: Dennis Grady Shock Hugoniot data for full-density and porous compounds of boron carbide, silicon dioxide, tantalum pentoxide, uranium dioxide and playa alluvium are investigated for the purpose of equation-of-state representation of intense shock compression. Complications of multivalued Hugoniot behavior characteristic of highly distended solids are addressed through the application of enthalpy-based equations of state of the form originally proposed by Rice and Walsh in the late 1950's. Additivity of cold and thermal pressure intrinsic to the Mie-Gruneisen EOS framework is replaced by isobaric additive functions of the cold and thermal specific volume components in the enthalpy-based formulation. Additionally, experimental evidence supports acceleration of shock-induced phase transformation on the Hugoniot with increasing levels of initial distention for silicon dioxide, uranium dioxide and possibly boron carbide. Methods for addressing this experimentally observed facet of the shock compression are introduced into the EOS model. [Preview Abstract] |
Wednesday, July 10, 2013 4:00PM - 4:15PM |
R6.00002: A Dynamic Discrete Dislocation Plasticity Method for the Dimulation of Plastic Relaxation under Shock Loading Benat Gurrutxaga-Lerma, Adrian P. Sutton, Daniel E. Eakins, Daniel S. Balint, Daniele Dini This talk intends to offer some insight as to how Discrete Dislocation Plasticity (DDP) can be adapted to simulate plastic relaxation processes under weak shock loading and high strain rates. In those circumstances, dislocations are believed to be the main cause of plastic relaxation in crystalline solids. Direct simulation of dislocations as the dynamic agents of plastic relaxation in those cases remains a challenge. DDP, where dislocations are modelled as discrete discontinuities in elastic continuum media, is often unable to adequately simulate plastic relaxation because it treats dislocation motion quasi-statically, thus neglecting the time-dependent nature of the elastic fields and assuming that they instantaneously acquire the shape and magnitude predicted by elastostatics. Under shock loading, this assumption leads to several artefacts that can only be overcome with a fully time-dependent formulation of the elastic fields. In this talk one of such formulations for the creation, annihilation and arbitrary motion of straight edge dislocations will be presented. These solutions are applied in a two-dimensional model of time-dependent plastic relaxation under shock loading, and some relevant results will be presented. [Preview Abstract] |
Wednesday, July 10, 2013 4:15PM - 4:30PM |
R6.00003: Numerical simulation of multiscale damage-failure transition and shock wave propagation in metals and ceramics Yuriy Bayandin, Natalia Savelieva, Andrey Savinykh, Oleg Naimark Statistical theory of evolution of typical mesoscopic defects revealed specific type of criticality--structural-scaling transitions and allowed the development of phenomenology of damage and plastic flow in materials under intensive loading, which established characteristic multiscale collective modes of defects responsible for formation of plastic waves and damage-failure transition. Original approach based on wide range constitutive equations was developed for simulation of multiscale damage-failure transition mechanisms and shock wave propagation in metals and ceramics in range of strain rate $10^3-10^8 s^{-1}$. It was shown that mechanisms of a plastic relaxation and damage-failure transitions are linked to multiscale kinetics of mesodefects collective modes with the nature of solitary waves and blow-up dissipative structures consequently. Numerical simulation of original plate impact tests showed that the model describes shock wave loading for metals and ceramics, and allowed us to explain the effect of power law phenomena of plastic wave fronts formation, its self-similar features under reloading and unloading. Analysis of shock wave profiles in ceramics for different thicknesses of specimens in terms of self-similar variables supports the universality of shock wave fronts. [Preview Abstract] |
Wednesday, July 10, 2013 4:30PM - 5:00PM |
R6.00004: Jetting Instability Mechanisms of Particles from Explosive Dispersal Invited Speaker: Robert Ripley The formation of post-detonation ``particle'' jets is widely observed in many problems associated with explosive dispersal of granular materials and liquids. Jets have been shown to form very early, however the mechanism controlling the number of jetting instabilities remains unresolved despite a number of active theories. Recent experiments involving cylindrical charges with a range of central explosive masses for dispersal of dry solid particles and pure liquid are used to formulate macroscopic numerical models for jet formation and growth. The number of jets is strongly related to the dominant perturbation during the shock interaction timescale that controls the initial fracturing of the particle bed and liquid bulk. Perturbations may originate at the interfaces between explosive, shock-dispersed media, and outer edge of the charge due to Richtmyer-Meshkov instabilities. The inner boundary controls the number of major structures, while the outer boundary may introduce additional overlapping structures and microjets that are overtaken by the major structures. In practice, each interface may feature a thin casing material that breaks up, thereby influencing or possibly dominating the instabilities. Hydrocode simulation is used to examine the role of each interface in conjunction with casing effects on the perturbation leading to jet initiation. The subsequent formation of coherent jet structures requires dense multiphase flow of particles and droplets that interact though inelastic collision, agglomeration, and turbulent interaction. Macroscopic multiphase flow simulation shows clustering of particles and merging of smaller instabilities with major jet structures. The methods are further applicable to particles premixed with explosive, which are known to form jets with only an external interface. Late-time dispersal is controlled by particle drag and evaporation of droplets. Numerical results for clustering and jetting evolution are compared with experiments. The work is extended to include interaction of particle and droplet jets with surrounding obstacles and associated combustion phenomena. [Preview Abstract] |
Wednesday, July 10, 2013 5:00PM - 5:15PM |
R6.00005: Kinetic of phase transformation nucleated from grain boundaries Jean-Bernard Maillet, Bertrand Rouet-Leduc, Christophe Denoual A model for phase transitions initiated at nucleation sites on grain boundaries is proposed and tested against numerical simulations: a mean field approach allows to explicitely consider the granular structure, yielding accurate predictions for a wide span of nucleation processes. The transition between heterogeneous (i.e. controled by the microstructure) and homogeneous behavior is predicted, which depends on the nucleation rate and the velocity of phase transformation. [Preview Abstract] |
Wednesday, July 10, 2013 5:15PM - 5:30PM |
R6.00006: An Empirically Based Shaped Charge Jet Break-Up Model Ernest Baker, James Pham, Tan Vuong This paper discusses an empirically based shaped charge jet break-up model based around Walsh's breakup theory and provides significant experimental confirmation over a broad range of velocity gradients. The parameters which affect jet length and breakup times are fairly well known, but there is some controversy over the exact nature of the dependencies. Walsh theorized that the dependence of jet length would take a particular form, based on his determination of a dimensionless parameter for the problem and numerical experiments in which initial perturbation strengths were varied. Walsh did not present comparisons with experimental results. Chou has presented a variety of different jet break-up models with some data comparisons. Mostert [3] has suggested that breakup time is proportional to $\left( {\frac{\Delta m}{\Delta v}} \right)^{1/3}$. It is shown here that the parameter $\left( {\frac{\Delta m}{\Delta v}} \right)^{1/3}$or $\left( {\frac{dm}{dv}} \right)^{1/3}$, closely related to Walsh's dimensionless parameter, whose values were obtained from either experiments or simulations correlates quite well with jet breakup times for a very wide variety of shaped charge devices. The values of $\Delta m$ and $\Delta v$ are respectively the jet mass and the velocity difference of the portion of jet in question. For a typical shaped charge $\frac{\Delta m}{\Delta v}$ is essentially invariant with respect to time. In this paper, we present the mathematical basis for an empirically based break-up model with a similar basis to Walsh and Mostert, as well as supporting empirical data for a broad range of shaped charge geometries. [Preview Abstract] |
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