Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session H5: BIEP: Penetration I |
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Chair: James Walker, SWRI Room: Broadway I/II |
Tuesday, June 18, 2019 9:15AM - 9:45AM |
H5.00001: Structure-Property Relationships at the Extremes Invited Speaker: Cyril Williams The inelastic response and mechanical properties acquired from most shock compressed solids are distinctly different from those acquired from quasi-static or moderate strain rates. For instance, the residual hardness of many shock compressed metals has been found to be considerably lower than those loaded under quasi-static conditions to the same maximum stress. However, the residual hardness of shock compressed metals is much higher than those loaded quasi-statically to the same total strain. These observations suggest that the mechanisms active during inelastic deformation under shock compression and quasi-static or moderate rates may be quite different. This talk concerns the dynamic response of metals and metallic alloys at the extremes. Results derived from shock recovery experiments show that the as-received microstructure and how it evolves can strongly influence the mechanical response and consequent failure of metals and metallic alloys. The failure characteristics in 1100 aluminum changes from ductile to quasi-brittle at ~8.3 GPa perhaps due to dynamic recovery. Failure in both 5083 aluminum and AZ31B magnesium was determined to be dominated by heterogeneous nucleation, growth, and coalescence of micro-voids from large second phase intermetallic inclusions. However, isolated regions of nano-voids were observed which were attributed to homogeneous nucleation (possibly from vacancies/vacancy clusters), growth and coalescence. The failure characteristics in UFG AMX602 magnesium was distinctly different from the aforementioned materials. Failure did not initiate from large intermetallic inclusions because there were none present in AMX602 magnesium. However, numerous isolated cracks were observed around the spall plane and the fracture surface was found to be striated due to the formation of oxide layers during the powder metallurgy process. Also, time-resolved in-situ XRD shock experiments show twinning during compression and detwinning during stress release. The microstructure and residual hardness of nanocrystalline Cu-Ta alloy proves to be insensitive to shock stresses ranging up to 15 GPa. These findings warrant more research to develop a better understanding of the role of microstructure in shock compressed solids. [Preview Abstract] |
Tuesday, June 18, 2019 9:45AM - 10:00AM |
H5.00002: Reaction Initiation of Metal Spheres Upon Ballistic Impact with an ANVIL Dihia Idrici, Michael J. Soo, Sam Goroshin, Andrew J. Higgins, David L. Frost When a spherical metallic projectile impacts an anvil at high speed, fragmentation of the projectile and ignition of the fragments may occur. In the present experimental study, small metallic spheres are accelerated up to speeds of 1.2 km/s in a helium--driven gas gun and impact a steel anvil. The ignition thresholds are determined for aluminum, titanium, and zirconium projectiles using optical diagnostics. High--speed photography is utilized to observe the fragmentation process and emission spectroscopy is used to infer the temperature of the fragments. [Preview Abstract] |
Tuesday, June 18, 2019 10:00AM - 10:15AM |
H5.00003: Experimental methodology for measuring and constraining numerical simulation parameters of microwave damaged concrete under ballistic impact Gareth Tear, William Proud A methodology of investigating microwave damage on small representative samples of concrete has been developed and will be presented. An experimental method of verifying Abaqus/ComSOL simulation results has been developed in conjunction with the model itself to provide sensitive and specific results. This allows refinement of the multitude of variables in the simulation by identifying key experimental measurements. The presentation will focus on the experimental developments for time correlating material failure with material velocity. Framing cameras, PDV and X-ray radiography have been used together to constrain the material velocity and damage simultaneously. As these are directly related to simulation parameters, this technique can be used in conjunction with developments in the simulation, which are focused on automating the refinement process to improve the agreement of simulation results with these experimental results. By identifying what measurements and precision is needed, the experimental process can be optimized, and by varying the numerical parameters, the precision of the model can be refined. [Preview Abstract] |
Tuesday, June 18, 2019 10:15AM - 10:30AM |
H5.00004: A constitutive model for dry soils under a wide range of pressures Eric Herbold, Michael Homel, M.B. Rubin A constitutive model is developed for dry soils that smoothly transitions across a wide range of pressures and temperatures.~ This model handles large-deformations and is thermomechanically consistent. Ideas from critical state soil mechanics via a breakage model, which model granular media at relatively low pressure, are combined with an equation of state for shock loaded solids to investigate the compaction of initially unconsolidated brittle granular materials. The resulting constitutive equations provide a fully-coupled model containing a natural transition between granular and solid states through the Helmholtz free energy. The model is calibrated to data with a wide-range of pressures and strain rates for Ottawa sand and predictions of the model are compared with static compaction, penetration and shock-loading results.~ Based upon this calibration, the compaction model predicts Hugoniot temperatures converge with ``snow-plow" model at approximately 8 GPa. This work was performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
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