Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session P38: Materials in Extremes: Complex SystemsFocus
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Sponsoring Units: DCOMP GSCCM DMP Chair: Harry Radousky, Lawrence Livermore National Laboratory Room: LACC 501A |
Wednesday, March 7, 2018 2:30PM - 3:06PM |
P38.00001: Dynamics of supercritical fluids: Theory and simulations Invited Speaker: Taras Bryk Structural and dynamical properties of supercritical fluids are expected to depend smoothly on temperature and pressure. Recently it was suggested to analyze the propagating density fluctuations in supercritical fluids as a function of pressure/density, based on the idea that dynamical properties could be more sensitive to phase changes than the structural properties. Using a combination of inelastic X-ray scattering experiments and molecular dynamics (MD) simulations, it was discovered [1,2] that the onset of deviation from the hydrodynamic dispersion of sound (the so-called “positive sound dispersion” (PSD)) could be used as a boundary between liquid-like and gas-like regions existing in a fluid as reminiscent of the subcritical behavior. |
Wednesday, March 7, 2018 3:06PM - 3:18PM |
P38.00002: Computational and Experimental Study of TATB Shock Initiation at the Grain Scale Joseph Zaug, Michelle Rhodes, Paulius Grivickas, Jean-Baptisite Forien, Carol Davis, keo Springer, Laurence Fried, Trevor Willey, John Sain, Owen Mays, Mark Converse, Joseph Tringe Shock initiation of high explosives is believed to be controlled by hot spots that ignite, grow, and coalesce. We designed shockwave experiments (Nov. 2017) to directly measure the early stages of shock initiation with spatial resolution of several microns. Supporting simulations have been conducted to optimize the experimental design and help interpret the experimental data. The first stage of this work is to characterize the grain structure in TATB plastic-bonded samples that are 0.12 - 0.20 mm thick. We used computed tomography capabilities to examine the 3D particle structures. Further, we will investigate the response of these samples to shock waves at the 0.010 - 0.10 mm scale. Experiments will be conducted at LLNL’s Jupiter Laser Facility. Line-VISAR measurements of shocks will determine time dependent flow velocities with an appropriate spatiotemporal resolution to capture variations induced by the grain-scale structure of the materials. Microwave transmission/reflection measurements will be simultaneously conducted to characterize void collapse and ignition phenomena. |
Wednesday, March 7, 2018 3:18PM - 3:30PM |
P38.00003: High velocity impact-induced initiation and energy release behavior of pre-stressed aluminum reactive materials Kevin Hill, Michelle Pantoya, Valery Levitas Pre-stressing aluminum (Al) particles by annealing and quenching Al powder alters particle mechanical properties and is linked to an increase in ignition sensitivity under low velocity (0.1-4 m/s) drop weight impact tests. Pre-stressing Al particles alters their reaction mechanism by promoting decohesion and fracture of the alumina shell due to high tensile stresses in the Al core leading to much more pronounced fracture of unsupported shells. This work extends ignition studies of pre-stressed Al powder to high velocity impact ignition. Towards this end, a new laboratory scale high velocity impact system has been developed to examine ignition and combustion behaviors of pre-stressed Al pellets at velocity ranges between 150-1500 m/s. This system is capable of firing a 2 g projectile from a .410 shot gun shell into a catch chamber. The catch chamber is instrumented with pressure transducers. high speed imaging diagnostics to examine impact velocity, fragmentation, and combustion in situ, and UV/VIS spectroscopy to examine combustion timescales. Preliminary results for micron and nanoparticle Al pellets (both prestressed and untreated) with PVDF binder will be presented, along with characteristic images and spectra during impact. |
Wednesday, March 7, 2018 3:30PM - 3:42PM |
P38.00004: A SPH Implementation with Ignition and Growth and Afterburning Models for Aluminized Explosives Qing Peng, Guangyu Wang, Guirong Liu, Suvranu De Aluminized explosives have been applied in military industry since decades ago. Compared with ideal explosives such as TNT, HMX, RDX, aluminized explosives feature both fast detonation and slow metal combustion chemistry, generating a complex multi-phase reactive flow. Though aluminized explosives have been employed for a long time, the mechanism underneath the chemical process is still not thoroughly understood. In this paper, a smooth particle hydrodynamics (SPH) method incorporated ignition and growth model, and afterburning model has been proposed for the simulation of aluminized explosive. Ignition and growth model is currently the most popular model for the simulation of high explosives, which is capable of accurately reproducing arrival time of detonation front and pressure history of high explosives. It has been integrated in commercial software such as ANSYS-LS DYNA. In addition, an afterburning model has been integrated in the SPH code to simulate the combustion of aluminum particles. Simulation is compared with experiment and good agreement is observed. The proposed mathematical model can be used to study the detonation of aluminized explosives. |
Wednesday, March 7, 2018 3:42PM - 3:54PM |
P38.00005: Computations and experiments of Richtmeyer-Meshkov like instabilities in shock-driven particle-laden flow Ricardo Gonzalez, Sumanth Reddy Lingampally, Patrick Wayne, Peter Vorobieff, Gustaaf Jacobs Computations and experiments are performed of the interaction between a shock and a particle-seeded curtain. |
Wednesday, March 7, 2018 3:54PM - 4:06PM |
P38.00006: First-principles study of porosity in amorphous silica and alpha quartz Jonathan Muliang, Ching Fong, Daniel Orlikowski, Lin Yang We have investigated the SiO2 systems, amorphous silica and alpha quartz, to understand the energy dependence on increasing porosity from closed cell to open cell foam from first-principles. A series of first-principles, density functional theory (DFT), calculations on these systems were examined with increasing porosity from 0 to nearly 50%. The formation energy per surface area of the void was calculated as a function of radius. The results from this study can be potentially useful to inform larger scale, continuum hydrocode models and provide initial internal energy and pressure for the first-principles Hugoniot as a porous SiO2 foam is compressed. The Pade model for a liquid-drop, which spans the limits from drop to planar surface as a function of radius, was used to fit our DFT results. The extrapolation of the model suggests a gradual approach to the planar surface limit, beyond the radius of 300 Å for both ordered and disordered systems, indicating a universal behavior in the SiO2 systems. |
Wednesday, March 7, 2018 4:06PM - 4:18PM |
P38.00007: High strain-rate loading of nanofoams Eduardo Bringa, Carlos Ruestes, Emmanuel Millan, Emiliano Aparicio Nanoscale metallic foams display mechanical properties which make them attractive for a variety of technological applications. We report simulated high strain-rate loading for a model polycrystalline nanoporous gold structure with around 10 nm mean filament diameter and 15 nm average grain size, comparable to foams produced by dealloying. |
Wednesday, March 7, 2018 4:18PM - 4:30PM |
P38.00008: Perturbation Decay Experiments on Granular Materials Tracy Vogler, Marcia Cooper Sakharov and co-workers proposed an experiment 1965 in which a sinusoidal perturbation to a planar wave evolves as it travels through a sample. More recently, Liu et al. used gas guns rather than explosives to drive the shock wave, resulting in better defined input conditions. Previous work involved study of solids such as aluminum and liquids such as water and mercury. Here, the approach is applied to granular materials in a wedge geometry so that a broad range of sample thicknesses is sampled in one experiment. This experimental approach is attractive since it probes phenomena in a different manner than planar shock experiments, and the length scales involved can be varied by changing the perturbation wavelength and amplitude. A novel optical diagnostic approach is developed to provide increased data return. In addition, continuum and grain-scale simulations are used to understand the main material parameters affecting the observed behavior. |
Wednesday, March 7, 2018 4:30PM - 4:42PM |
P38.00009: Rate Effects in the Compaction of Brittle Granular Materials Michael Homel, Eric Herbold Under quasistatic loading, brittle granular materials compact through a process of comminution, whereby a reduction in particle size facilitates more efficient packing allowing for a reduction in porosity with a minimal increase in the elastic strain energy in the material. Under dynamic loading, comminution is limited by finite crack propagation velocity and inertial resistance to granular flow. We investigate this phenomena using new methods for mesoscale simulation and in-situ x-ray imaging of granular compaction. Implications on continuum constitutive model development are discussed. |
Wednesday, March 7, 2018 4:42PM - 4:54PM |
P38.00010: Time resolved shock induced phase transitions in powdered SiO2 Ryan Crum, Dorothy Miller, Eric Herbold, Jonathan Lind, Ryan Hurley, Michael Homel, Minta Akin Geophysical materials such as silicates are ubiquitous within the Earth, including Earth’s deep interior. These materials are studied under high pressure and temperature environments to best match the conditions they are under in the planetary interior. To restrict complicating factors, these efforts primarily probe the bulk single crystal/polycrystalline form of the geophysical material via velocimetry or, less frequently, by surface X-ray analyses. Confounding variables due to the heterogeneity of real geophysical materials makes these studies less representative or informative on their true response. To better understand dynamics of geophysical granular materials, 54% TMD SiO2 was shock compressed using a two-stage gas gun and probed by both in-situ X-rays for diffraction analyses and velocimetry diagnostics. These results are compared to fully dense SiO2 to provide the role of porosity upon phase transitions and implications that may have in predictive modeling capabilities. |
Wednesday, March 7, 2018 4:54PM - 5:06PM |
P38.00011: An experimental and theoretical approach to study the link between Triboemission and Tribocharging Alessandra CIniero, Daniele Dini, Tom Reddyhoff This work describes recent research into the causes of triboemission in sliding contacts and its links to tribocharging. The term triboemission refers to emission of electrons, ions and photons generated when surfaces are rubbed together. The term tribocharging, on the other hand, refers to the transfer of charge between rubbing components. Triboemission and tribocharging may be important in the formation of boundary lubricant films and in the degradation of lubricants. |
Wednesday, March 7, 2018 5:06PM - 5:18PM |
P38.00012: Dual hierarchical particle jetting in divergently shocked particle rings Kun Xue We study experimentally the formation of a dual hierarchical jet structure in dry dense particle rings subjected to the radially divergent shock loadings. The internal perturbations initiated from the internal surface of particle ring grow quadratically in time and evolve into dozens of jets with rounded cusps regularly separated by fine radially aligned filaments. A large number of small external jets emerge from the external jet shortly after the acceleration of the external surface reduces to zero, and exhibit a “spike-bubble” combined structure. After an initial fast growth the overall pattern maintains a novel proportionate growth until the interaction between the internal and external instabilities. As the internal jets approach the external surface, the radial progress of the internal jets is progressively retarded, leading to a total inversion of the jetting pattern, in which it is the ligaments rather than the jet cusps that penetrate the external surface. Although the growth of the internal and external jets both resemble the turbulent mixing of Rayleigh-Taylor instability, the marked differences in the shape of pattern suggest distinct mechanisms underlying the onsets of respective jetting pattern. |
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