Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session V7: Particulate Matter V: New Experimental Techniques |
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Chair: Mike Homel, Lawrence Livermore National Laboratory Room: Regency Ballroom F |
Thursday, July 13, 2017 3:45PM - 4:00PM |
V7.00001: Probing the dynamic response of ordered lattice materials J. Lind, B. J. Jensen, M. Barham, N. R. Barton, M. Kumar The advent of additive manufacturing has opened up the possibility of designing and creating lattice structures that were previously not possible. Their remarkable strength-to-weight scaling has garnered immense interest from the research community, but one must ask if their strength, which depends uniquely on their geometric and topological character, still holds when they are deformed dynamically? Taking advantage of the newly commissioned Dynamic Compression Sector at the Advanced Photon Source at Argonne National Laboratory, we performed a series of gas gun experiments combined with x-ray phase contrast imaging measurement on additively manufactured polymer lattice and foam structures. With on the order of micron resolution and 100s of ns temporal resolution, the local deformation characteristics of the material can be extracted by tracking the nodal displacements within the lattice material. Properties such as local ligament strain, maximum supported strain, compaction behavior and elastic wave evolution can be extracted from this measurement. We will discuss on-going comparison of the experimental results with direct numerical simulations. [Preview Abstract] |
Thursday, July 13, 2017 4:00PM - 4:15PM |
V7.00002: Impact performance of aluminium foams in a direct impact Hopkinson bar Tom Cowie, Lewis Lea, Chris Braithwaite The impact performance of aluminium foams has been studied using a direct impact Hopkinson bar. The bar system, including the striker, has been equipped with a PDV system as opposed to gauges, which allows for much more complete deformation information to be obtained. A series of interrupted tests which limit the strain in the material to a known value, in conjunction with x-ray tomography have given valuable insight into the failure mechanisms of aluminium foams and the localisation of damage within the structure. [Preview Abstract] |
Thursday, July 13, 2017 4:15PM - 4:30PM |
V7.00003: Direct measurements of dynamic granular compaction using synchrotron phase-contrast X-ray radiography Michael E. Rutherford, David J. Chapman, James G. Derrick, Jack R.W. Patten, Alexander Rack, Phil A. Bland, Gareth S. Collins, Daniel E. Eakins The true nature of dynamic granular compaction is challenging to resolve with surface-based diagnostics. Direct measurements of mesoscale shock phenomena such as grain fracture, stress-bridging and local phase transition growth are required to understand how key initial parameters (e.g. grain morphology or size) may be tuned to influence the distribution of shock states developed in a shocked powder. Bimodal, porous samples analogous to precursor chondritic meteorite (chondrite) material were shock-compressed via plate-impact. The shock compaction process was diagnosed with single-bunch (150 ps, 71 µm), transmission phase-contrast X-ray radiography at the European Synchrotron Radiation Facility. The cutting-edge radiographic method permitted spatially-resolved measurements of wave velocities and wave thickness across the powder bed in real-time. Focus is given to the direct experimental measurement and evolution of shock state distributions within the powder samples, and how these distributions were dependent on the guest particle size. [Preview Abstract] |
Thursday, July 13, 2017 4:30PM - 4:45PM |
V7.00004: Visualizing Perturbation Decay in Shocked Granular Materials Marcia Cooper, Tracy Vogler A new experiment continuously visualizing shock wave perturbation decay through an increasing thickness of granular material has been tested with a gas gun. The experiment confines powders of either tungsten carbide or cerium oxide into a wedge geometry formed by tilting the downstream observation window, plated with a reflective aluminum film, at a shallow angle from the driver plate. The driver is machined with a sinusoidal wavy pattern for incident shock wave perturbation. After projectile impact, the perturbed shock wave passes through the granular material, first emerging at the wedge toe. Image sequences collected at 5 MHz of reflectivity loss at the plated window-granular material interface capture the spatial variation in wave propagation with increasing sample thickness. Extracting the evolving wavy pattern from the images determines the temporal perturbation amplitude. The data are compared to continuum and mesoscale simulations in normalized terms of perturbation amplitude and wavelength. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Thursday, July 13, 2017 4:45PM - 5:15PM |
V7.00005: Multi-scale penetration mechanics of projectiles through granular media using neutrons and x-rays Invited Speaker: Dayakar Penumadu The objective of the research is to use advanced non-destructive radiation based imaging techniques using neutrons and x-rays to address the fundamental science and engineering associated with the penetration mechanics of projectiles. Radiation based imaging is used to describe the initial state and after projectile penetration of a sand sample (three dimensional arrangement of solid particles and associated voids with and without water phases), evolution of its microstructure with applied stress, implementing one-dimensional and triaxial compression loading using controlled laboratory experiments to develop constitutive models to represent the mechanical behavior of a granular assemblage, obtain unique experimental data associated with penetrators impacted into such medium using suitable velocities while tracking the deceleration-time history of the projectile, visualizing the path it traverses using high speed X-ray flash images, and integrate the observations in a predictive and custom developed DEM-FEM formulation for modeling the boundary value problem(s). The work aims at developing a better understanding of the basic science and mechanics associated with increased penetration into granular materials and opaque composites. [Preview Abstract] |
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