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 Z4: TM Continuum Modeling V |
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Chair: Joe Hooper, Naval Postgraduate School Room: Vashon |
Friday, July 12, 2013 11:00AM - 11:15AM |
Z4.00001: Numerical and Theoretical Analysis of Plastic Response of 5A06 Aluminum Circular Plates Subjected to Underwater Explosion Loading Peng Ren, Wei Zhang Dynamic response analysis of structures subjected to underwater explosion loading has been always an interesting field for researchers. Understanding the deformation and failure mechanism of simple structures plays an important role in an actual project under this kind of loading. In this paper, the deformation and failure characteristics of 5A06 aluminum circular plates were investigated computationally and theoretically. The computational study was based on a Johnson-cook material parameter mode which was obtained from several previous studies provides a good description of deformation and failure of 5A06 aluminum circular plates under underwater explosion loading. The deformation history of the clamped circular plate is recorded; the maximum deflection and the thickness reduction measurements of target plates at different radii were conducted. The computational approach provided insight into the relationship between the failure mechanism and the strength of impact wave, and a computing formulae for strain field of the specimen was derived based on the same volume principle and rigid-plastic assumption. The simulation and theoretical calculation results are in good agreement with the experiments results. [Preview Abstract] |
Friday, July 12, 2013 11:15AM - 11:30AM |
Z4.00002: Instability in shocked granular gases Nick Sirmas, Matei Radulescu Shocks in granular media, such as vertically oscillated beds, have been shown to develop instabilities. Similar jet formation has been observed in explosively dispersed granular media. In the current study, we investigate the origin of this instability. Both particle dynamics and continuum based simulations of the hydrodynamics of granular gases are investigated in the presence of shock compression. The shock waves are found to be unstable in the presence of dissipative collisions in the particle bed. The instability manifests itself as distinctive high density non-uniformities and convective rolls on the shock surface. The characteristic spacing of the non-uniformities is found to be well approximated by the characteristic relaxation length scale, which is controlled by both the shock strength and amount of energy dissipation in particle collisions. By studying the time evolution of the material undergoing the shock wave compression and further relaxation, we found that the gas develops the instability on the same time scales as the clustering instability in homogeneous gases. This confirms that the clustering instability is the dominant mechanism. [Preview Abstract] |
Friday, July 12, 2013 11:30AM - 11:45AM |
Z4.00003: An Exact Riemann Solver for a Granular Mixture Model with Multiple Solid Components Michael Crochet, Keith Gonthier The solution of the two-phase Riemann problem is an essential component of finite-volume numerical methods applied to hyperbolic systems of multiphase model equations. These are typically used to study deflagration-to-detonation transition in energetic materials, and predict flow field structures associated with the dynamic compaction of gas--granular solid mixtures. A widely-used two-phase model has been extended recently to include an arbitrary number of solid components, which can be used to analyze the thermomechanical behavior of metallized explosives and mixtures containing multiple solid grain sizes. Although a solution to the two-phase Riemann problem has been formulated for gamma-law equations of state, there is currently no available solution for the $N$-phase analogue in the literature. Here, an extension of the exact two-phase solution to systems containing multiple solid phases is developed, where each phase is governed by general, convex equations of state. The resulting Riemann solver can be used in the verification of existing numerical schemes, and also serve as a framework for the future construction of upwind, Godunov-based numerical methods. A general overview of the solver methodology is given, and three-phase example problems are considered. [Preview Abstract] |
Friday, July 12, 2013 11:45AM - 12:00PM |
Z4.00004: Numerical Simulation of the Detonation Propagation in Silicon Carbide Shell Igor Balagansky, Anton Terechov Last years it was experimentally shown that in condensed high explosive charges (HE) placed in silicon carbide shell with sound velocity greater than the detonation velocity in HE, there may be observed interesting phenomena. Depending on the conditions, as an increase or decrease of the detonation velocity and pressure on the detonation front can be observed. There is also the distortion of the detonation front until the formation of a concave front. For a detailed explanation of the physical nature of the phenomenon we have provided numerical simulation of detonation wave propagation in Composition B HE charge, which was placed in silicon carbide shell. Modeling was performed with Ansys Autodyn in 2D-axis symmetry posting on an Eulerian mesh. Special attention was paid to selection of the parameters values in Lee-Tarver kinetic equation for HE and choice of constants to describe behavior of the ceramics. For comparison, also we have carried out the modeling of propagation of detonation in a completely similar assembly with brass shell. The simulation results agree well with the experimental data. In particular, in silicon carbide shell distortion of the detonation front was observed. A characteristic feature of the process is the pressure waves propagating in the direction of the axis of symmetry on the back surface of the detonation front. [Preview Abstract] |
Friday, July 12, 2013 12:00PM - 12:15PM |
Z4.00005: A Comparison of the Shock Response of the Material Point Method Kevin Ruggirello, Shane Schumacher The Lagrangian Material Point Method (MPM) has been implemented into the Eulerian shock physics code CTH, at Sandia National Laboratories. Eulerian hydrodynamic methods are useful for large deformation problems, where ``mesh tangling'' typically leads to difficulties for Lagrangian methods. However, Eulerian techniques suffer from numerical diffusion due to advection, which can be problematic for many material models requiring the transport of a damage parameter or other state variables that need to remain sharp. The inclusion of the MPM in CTH allows for the accurate simulation of structural response to shock loading in a single framework. This paper presents a comparison of the shock response of the MPM to a Lagrangian, and Eulerian hydrodynamics code. All three solutions will be compared to exact analytical solutions in order to asses the accuracy of the shock response of each. [Preview Abstract] |
Friday, July 12, 2013 12:15PM - 12:30PM |
Z4.00006: The Role of Quantum Nuclear Effects in Shock-Induced Chemistry and Colored Thermostats for Their Efficient Description Evan Reed, Tingting Qi, Qian Yang A fast methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects in a self-consistent fashion. We introduce a modification of the multiscale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently, semi-classically incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. We study shock-compressed methane using the ReaxFF potential. We find that the self-consistent nature of the method results in the onset of chemistry at 40\% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. We employ new statistical and data mining methods to reveal the nature of the chemistry. [Preview Abstract] |
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