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 L5: BIEP: Penetration II |
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Chair: Cyril Williams, ARL Room: Broadway I/II |
Tuesday, June 18, 2019 4:00PM - 4:15PM |
L5.00001: Size Scaling Damage Saturation in Hypervelocity Cratering Experiments in Al 2024 James Walker, Sidney Chocron, Donald Grosch Experiments were performed measuring mass liberated from an Al 2024-T351 target during impacts by an 3.0-cm-diameter aluminum sphere in the range of 4 to 5.77 km/s. The experiments were performed with a large two-stage light gas guns firing into targets mounted on a pendulum. The mass liberated from the targets, as measured by pre- and post-test weighing of the target, shows an interesting size-scale behavior when compared with historical data on Al 2024-T4 targets performed at smaller scale. Essentially, small spherical impactors (up to 1.27 cm in diameter) show a mass liberation that scales with impact speed times the square root of the diameter of the impactor. However, somewhere in the region of 1 cm diameter, the liberated mass transitions to scaling in terms of impact speed squared and there is no longer a size scale dependence on the liberated mass. This ejecta mass behavior is interpreted in the context of damage saturation. To support the analysis, computations were performed looking at damage model behavior that is required to support such a size scale transition in the region of 1 cm impactor diameter. [Preview Abstract] |
Tuesday, June 18, 2019 4:15PM - 4:30PM |
L5.00002: Rate Dependence of Penetration in Sandy Soils Stephan Bless, Mehdi Omidvar, Abdelaziz Ads, Magued Iskander In our previous APS paper on sand penetration, we reported on penetration of rods at relatively high velocity. Data were consistent with a Poncelet-type equation, and they provided good calibration for the Poncelet drag that mainly influences high velocity effects, but poor resolution of the velocity-independent term that is due to strength and friction. Now we have complemented those studies with both low impact velocity and ``static'' penetrometer data, which provide excellent resolution for the low speed penetration resistance. We find that the penetration resistance for inertial and driven rod penetration depends on depth-squared until full embedment. This is apparently due to side friction which dominates end bearing strength. However, simple depth-dependent friction force model cannot explain these results with reasonable values of friction coefficient. [Preview Abstract] |
Tuesday, June 18, 2019 4:30PM - 4:45PM |
L5.00003: Projectile penetration in granular material and high strain rate response of sand Dayakar Penumadu, Aashish Sharma Penetration depth is the most important parameter in terminal ballistics. Here only projectiles penetrating granular medium is considered. Laboratory and field tests have shown that projectile characteristics such as mass, size and nose shape, and target characteristics such as strength and density determine the depth of penetration. In order to better understand the influence of projectile nose shape and placement density, a suite of laboratory projectile penetration tests was performed at different impact velocities without altering the size and mass of the projectile. These projectiles were instrumented with G-Rec, a combination of high-performance accelerometer and autonomous data recorder. G-Rec provided a unique opportunity to record acceleration-time history of the entire flight of the projectile. These tests have revealed very high decelerations and forces at impact along with extensive particle fracture along the path of the projectile. Additionally, in order to understand the strength and particle crushing under dynamic loading, high strain rate tests were performed in Split Hopkins Pressure Bar (SHPB). These tests show that high strain rate behavior is influenced by specimen density, saturation, particle shape and compliance of the confining boundary. [Preview Abstract] |
Tuesday, June 18, 2019 4:45PM - 5:00PM |
L5.00004: Incipient Fracture of Ceramics Under Ballistic Impact Brian Schuster, Andrew Tonge, Nicholas Lorenzo We will present results of small-scale terminal ballistic experiments of pure copper rods impacting commercial grade boron carbide and silicon carbide at striking velocities ranging from 1-2.5 km/s. Incipient deformation and fracture of these materials was examined using propagation-based phase contrast imaging (PCI) at a characteristic interval of 153.4 ns in the first 1-2 microseconds after impact. At the lowest striking velocities, the penetrator undergoes dwell or interface defeat and the target response is consistent with the cone crack formation at the impact site. At higher striking velocities there is a distinct transition to massive fragmentation leading to the onset of penetration. Continuum and microstructural scale simulations of the response will be used to assist in describing the critical stress states and resulting failure modes. [Preview Abstract] |
Tuesday, June 18, 2019 5:00PM - 5:15PM |
L5.00005: Impact and Penetration in a Synthetic Cohesive Soil Mehdi Omidvar, Stephan Bless, Abdelaziz Ads, Magued Iskander Investigation of the response of geotechnical materials to impact and penetration can be aided by use of transparent soil surrogates. There are many examples of this technique for study of granular soils. We report on use of a transparent surrogate for clay, a cohesive soil. The transparent medium was a Laponite colloid. Experiments involving low velocity penetration (intended to simulate torpedo anchors) and a penetrometer were conducted. There were variations in nose shape and shank cross section. Conical noses and round shank cross sections resulted in increased penetration. For a given geometry, penetration resistance was found to be essentially constant, with no velocity dependence but significant depth dependence. Penetration resistance is mainly due to end bearing strength, as opposed to lateral friction. The penetration resistance did not sensibly depend on rate for a change in rate of almost three orders of magnitude. DIC instrumentation revealed that flow around the penetrator is mainly along the shaft from the front to the rear. [Preview Abstract] |
Tuesday, June 18, 2019 5:15PM - 5:30PM |
L5.00006: Macro-damage and deformed microstructure of depleted uranium impacted by steel projectile at different velocities Dongli Zou, Dawu Xiao, Yawen Zhao, Lifeng He, Chao Lu Macro-damage and deformed microstructure evolution of depleted uranium impacted by steel projectile at a velocity ranged from 10 m/s to 90 m/s was investigated by means of confocal laser scanning microscope, electron backscatter diffraction, transmission electron microscope and indenter technique. The experimental results show that the spherical cap craters were formed in depleted uranium target impacted by steel projectile under different impact velocities, and the crater diameter and depth increased linearly with impact velocities increasing. Microstructural observation shows that four deformed zones could be classified from crater rim to deep matrix, including twin fragmentation zone, high density deformation twin zone, low density deformation twin zone and matrix zone. Twinning was considered as a dominant plastic deformation mechanism of depleted uranium subjected to impact loadings, and the twins \textbraceleft 130\textbraceright and \textbraceleft 172\textbraceright were mainly distinguished and confirmed. Keywords: depleted uranium; high velocity impact; dynamic deformation [Preview Abstract] |
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