Impact pressures generated by spherical particle hypervelocity impact on Yorkshire Sandstone

Hypervelocity impact tests were carried out at 4.8 km/s using the Open University's All Axis Light Gas Gun (AALGG) in the Planetary and Space Sciences Research Institute (PSSRI)'s Hypervelocity Impact Laboratory. A first estimate of the peak loading pressures was made using preliminary hydrocode simulations, supported by calculations. Following a review of existing published quartz and sandstone data, our previously published plate impact data were combined with high pressure quartz data to produce a synthetic Hugoniot. This will form the basis of future hydrocode modelling, as a linear Us-Up relationship does not adequately represent the behaviour of sandstone over the pressure range of interest, as indicated by experimental data on Coconino sandstone. This work is a precursor to investigating the biological effects of shock on microorganisms in sandstone targets. This paper also contains the first presentation of results of ultra high speed imaging of hypervelocity impact at the Open University. © 2007 American Institute of Physics

Elevated temperature measurements during a hypervelocity impact process

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Hugoniot properties of dry Yorkshire sandstone up to 8 GPa

A series of plate impact experiments has been performed to assess the dynamic behaviour of dry Yorkshire sandstone up to 8 GPa. Standard manganin gauges were inserted between samples in order to determine the principal Hugoniot curve. A VISAR system was used to measure the free surface velocity of the target. This work is in part of a research programme to understand the survivability of microbial life under impact and the creation of new habitats for microbial life as a function of shock processing of sandstone

Residual temperature measurements of light flash under hypervelocity impact

Experimental and theoretical results for light flash temperatures are presented for impacts on soda-lime glass by iron projectiles. The experiments were performed with a 2 MV Van de Graaff, where iron dust particles (0.14-0.63 mu m in diameter) impacted soda-lime glass at a velocity range of 5-20 kill s(-1). Theoretical calculations were based on the assumption of the Mie-Gruneisen equation of state (EoS) with different values for the Gruneisen coefficient and hydrodynamic behaviour (no strength effects were considered). Within the scatter of experimental data, results suggest a constant value for the average light flash temperature of approximately 2600 K independent of iron dust impact velocity. Although theoretical calculations are limited by the use of the Mie-Gruneisen EoS up to the point of incipient vaporisation of the target material, relatively good agreement with experiments is observed. This agreement suggests that the observed constant temperature may be due to material phase change from incipient to complete vaporisation over the range of velocities considere

Velocity thresholds for impact plasma production

Experiments have been performed on the dust accelerator facilities at the University of Kent at Canterbury (UK) and the Max-Planck-Institut fur Kemphysik(Germany) in which the production of plasma from impacts of micron and sub-micron particles at velocities from 1 to 90 km s(-1) has been measured. Various projectile and target materials have been investigated. Time-of-flight mass spectrometry of the positive ions in the plasma allows their atomic species to be identified. By accumulating large amounts of data over a range of impact velocities it has been possible to identify the threshold velocities required to produce ions of different species, whether present in the system as the nominal projectile and target materials or as contaminants. The results obtained have been compared with theoretical predictions based on the principles of molecular dynamics and with the results of hydrocode simulations

Impact pressures generated by spherical particle hypervelocity impact on yorkshire sandstone

Hypervelocity impact tests were carried out at 4.8 km/s using the Open University's All Axis Light Gas Gun (AALGG) in the Planetary and Space Sciences Research Institute (PSSRI)'s Hypervelocity Impact Laboratory. A first estimate of the peak loading pressures was made using preliminary hydrocode simulations, supported by calculations. Following a review of existing published quartz and sandstone data, our previously published plate impact data were combined with high pressure quartz data to produce a synthetic Hugoniot. This will form the basis of future hydrocode modelling, as a linear Us-Up relationship does not adequately represent the behaviour of sandstone over the pressure range of interest, as indicated by experimental data on Coconino sandstone. This work is a precursor to investigating the biological effects of shock on microorganisms in sandstone targets. This paper also contains the first presentation of results of ultra high speed imaging of hypervelocity impact at the Open University. © 2007 American Institute of Physics

Hydrocode modelling of hypervelocity impact on brittle materials: depth of penetration and conchoidal diameter

The Johnson-Holmquist brittle material model has been implemented into the AUTODYN hydrocode and used for Lagrangian simulations of hypervelocity impact of spherical projectiles onto soda-lime glass targets. A second glass model (based on a shock equation of state and the Mohr-Coulomb strength model) has also been used. Hydrocode simulations using these two models were compared with experimental results. At 5 km s(-1), the Mohr-Coulomb model under-predicted the depth of penetration, whilst adjustment of the Johnson-Holmquist model bulking parameter was required to match the experimental data to the simulation results. Neither model reproduced the conchoidal diameter; a key measured parameter in the analysis of retrieved solar arrays, so two failure models were used to investigate the tensile failure regime. A principal tensile failure stress model, with crack softening, when used with failure stresses between 100 and 150 MPa and varying bulking parameters, reproduced the conchoidal diameter morphology. Empirically-determined, power-law damage equation predictions for the range 5-15 km s(-1) were compared with simulations using both models since no experimental data was available. The power law velocity dependence of the depth of penetration simulations was found to be significantly lower than the 0.67 predicted by the empirically-determined damage equations