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J. Borg, A. Lloyd, J. Cogar, “Comparison of Average Radial Expansion Velocity from Impacted Liquid Filled Cylinders, Inter J. of Impact Eng., 34 (6), June 2007, 1020-1035. Abstract Comparison of average radial expansion velocity from impacted liquid filled cylinders In this paper, the average radial expansion velocity of an impacted fluid filled cylindrical target is investigated. Theoretical and numerical predictions of the radial expansion velocity are compared to the experimentally measured radial expansion velocity. The primary objective of this work is to assess the ability of these theoretical and numerical techniques to predict the radial expansion velocity. A secondary objective of this work is to quantify the effect of changes in dimensional scale on the radial expansion velocity and to construct a simple physics based model which incorporates these scaling effects. Two-dimensional numerical hydrocode simulations accurately predict the measured ejection velocity for tests with low projectile–target misalignment. However, three-dimensional numerical calculations, which account for this misalignment, accurately predict all experimental tests. A theoretical formulation, based on a simple conservation of energy principle, yields a zero-dimensional model which accurately predicts the two-dimensional hydrocode simulations. Thus for experimental simulations which have low projectile–target misalignment, the simple theoretical model developed here accurately predicts the average radial expansion velocity. A dimensional analysis of this theoretical formulation yields a scaling relationship which accurately predicts the effect of dimensional scale between two different experimental test series.   J. Borg, A. Lloyd, J. Cogar, D. Chapman, W. Proud, “Computational Simulations of the Dynamic Compaction of Porous Media”, Inter. J. of Impact Eng., 33, 2006 109-118. Abstract Computational simulations of the dynamic compaction of porous media The goal of this study was to apply and compare different computational compaction models to the dynamic compaction of porous silicon dioxide (SiO2) powder. Three initial specific volumes were investigated in this study, V00=1.3, 4 and 10 cm3/g, where the solid material specific volume is V0=0.4545 cm3/g. Two hydrodynamic codes, KO and CTH, were used to simulate the experimental results. Two compaction models, P– and P–λ were implemented within CTH in conjunction with the Mie–Grüneisen (MG) equation of state. The snowplow (SP) compaction model was implemented within KO. In addition, the MG equation of state based on the experimentally measured Hugoniot was implemented within CTH and was compared to the data as well. One-dimensional flyer plate experiments were conducted with impact velocities ranging from 0.25 to 1.0 km/s, which corresponded to a shock incident pressure range of 0.77–2.25 GPa. The computational simulations were compared to the temporal lateral stress signatures measured with manganin gauges, placed before and after the silica powder. It was found that the MG equation of state (EOS) most accurately reproduce all of the experimental data whereas none of the compaction models accurately reproduced all of the experimental data. However, of the compaction models investigated that the P– model tended to outperform the other considered. J. Borg, S. Bartyczak, N. Swanson, J. Cogar, ”Impact and Dispersion of Liquid Systems at Atmospheric Pressure,” ASME J. Fluids Eng. Vol. 128, No. 6 pp 1295-1307, 2006. Abstract Impact and Dispersion of Liquid Filled Cylinders The computational and experimental results of impact loading a thin wall liquid filled cylindrical target within a vacuum chamber are presented. The impact velocity ranges from 2.2 to 4.2 km/s. Both experimental and computational results are presented. It will be shown that impact dynamics and the early time fluid expansion are well modeled and understood. This includes the mass distribution and resulting expansion velocity. However, the late time dynamics, which includes the liquid breakup and droplet formation process of impacted liquid filled cylinders, is not well understood. J. Borg, D. Chapman, W. G. Proud, and J. Cogar, “Dynamic Compaction Modelling of Porous Silica Powder”, J. Applied Physics, vol 98, 2005. Abstract Dynamic compaction of porous silica powder The dynamic compaction characteristics of a porous silicon dioxide (SiO2) powder are reported. The initial specific volumes of the samples were either V00=1.30, 4.0, or 10.0 cm3/g whereas the silicon dioxide has a matrix specific volume of V0=0.455 cm3/g. The impact velocity ranges from 0.25 to 1.0 km/s and the shock incident pressure on the silica ranges from 0.77 to 2.25 GPa. The shock velocity–particle velocity exhibited a linear relationship within this range. Although these tests represent the low end of dynamic compaction, the dynamic tests compare favorably to extrapolated data available in the open literature. Theoretical pressure–particle velocity and shock velocity–particle velocity curves were generated using a P- compaction curve. The P- compaction curve accurately represented the pressure–particle velocity and shock velocity–particle velocity Hugoniot curves for the low specific volume powder, specifically V00=1.30 cm3/g. However, the P- compaction curve did not accurately represent the pressure–particle velocity or the shock velocity–particle velocity Hugoniot curves for the high specific volume powder, specifically V00=4.0 or 10.0 cm3/g. For the high specific volume powders the wave dynamics appears to be more complicated than is predicted by a single linear wave over the impact velocity and specific volume range investigated.
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