Browsing by Author "Goff, Michael J."

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    The bactericidal effect of shock waves
    (Institute of Physics, 2014-05-07) Leighs, J. A.; Appleby-Thomas, Gareth J.; Wood, David C.; Goff, Michael J.; Hameed, Amer; Hazell, P. J.
    There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to shock and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of shocked samples are presented alongside control sets to highlight key differences between cells in each case.
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    Gas gun ramp loading of Kel-F 81 targets using a ceramic graded areal density flyer system
    (Elsevier, 2015-03-06) Goff, Michael J.; Hazell, Paul J.; Appleby-Thomas, Gareth J.; Wood, David C.; Stennett, Christopher
    Kel-F 81 (PCTFE/Polychlorotrifluoroethylene) polymer targets were subjected to ramp loadings generated by a ceramic flyer accelerated into the targets by a gas gun in the plate impact configuration. This approach used a ceramic graded areal density flyer in conjunction with a ceramic buffer plate to induce a ramp loading in the target. The flyer was comprised of a rapid prototyped alumina ceramic. The loading was observed with embedded electromagnetic particle velocity gauges (PV gauges) with the results compared with ANSYS Autodyn™ hydrocode simulations. Experimental results show that ramp loadings of varying duration and magnitude were induced into the target. These loadings can be described as shockless compressions leading to shocked states within the material. In addition, numerical simulations provided further insight into the loading approach – with good agreement found with experimental data, opening the potential to design more complex loading systems in future.
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    Uncertainty analysis of data collected using embedded magnetic particle velocity gauges
    (AIP Publishing, 2023-09-26) Finnegan, Simon; Appleby-Thomas, Gareth J.; Hazael, Rachael; Ferguson, J. W.; Goff, Michael J.
    The uncertainties in particle velocity and position-time data collected using embedded magnetic gauges are presented. Data were also collected on the resistance change of gauge elements under shock loading and the effect of the element width, as opposed to length, on the observed rise times, as two factors that can affect the data quality and uncertainty analysis. A new method of fitting to the shock tracker data is also proposed. The data were collected using gas gun experiments on Comp-B and PCTFE targets. For a well characterized setup, the uncertainty in the particle velocity data can be reduced to such a level that noise and other ‘random’ variations in the data can be more significant. This highlights the importance of reducing these factors and collecting high quality data but also investigating additional sources of error, such as the resistance change of the elements under shock loading, in order to determine the true uncertainty.