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Barr A.D.,University of Sheffield | Clarke S.D.,University of Sheffield | Petkovski M.,University of Sheffield | Tyas A.,University of Sheffield | And 2 more authors.
Geomechanics from Micro to Macro - Proceedings of the TC105 ISSMGE International Symposium on Geomechanics from Micro to Macro, IS-Cambridge 2014 | Year: 2015

This paper investigates the effect of strain rate on the behaviour of dry and partially-saturated sand at very high stresses, seeking to clarify the existence of a strain-rate dependence and how this is affected by changes in moisture content. Quasi-static one-dimensional compression tests on a fine quartz sand have been carried out to axial stresses of 800MPa using the mac 2T multi-axial test rig at The University of Sheffield, alongside dynamic tests to 400MPa using a split Hopkinson pressure bar. Specimens were prepared at moisture contents of 0.0%, 2.5% and 5.0%, and were laterally confined using a steel loading box or steel ring to ensure one-dimensional test conditions. Lateral stresses were recorded to allow the three-dimensional stress state of the specimens to be analysed. The results show that knowledge of both the axial and radial stresses is important for understanding the response of sand at higher strain rates, where an increase in stiffness is observed axially when compared to the quasi-static results. © 2015 Taylor & Francis Group. Source

Pinto R.,Cranfield University | Carr D.,Cranfield University | Helliker M.,Porton Group | Girvan L.,University of Otago | Gridley N.,NP Aerospace
Textile Research Journal | Year: 2012

Personal armor, including body armor, is protective clothing designed to either absorb or deflect attacks that would usually be fatal to an individual. These attacks include, but are not limited to, slashing, bludgeoning, stabbing and ballistic threats. In the UK, body armor is worn by police officers for their shift; however, military personnel (particularly when based overseas) may wear body armor continuously for much longer time periods. Thus, the effect of wear due to use on the performance of body armor is of interest. Testing of body armor after actual use is problematic for several reasons including, but not limited to, (i) access to such items and (ii) a lack of knowledge of exactly what the body armor has been exposed to. Thus the use of laboratory testing to understand degradation of body armor is of interest to many agencies. Additionally, laboratory testing allows for the effect of variables to be investigated independently of each other, as well as in combination. The effect of inter-layer wear between apparel items and/or among layers of fabric within apparel does not appear to be systematically explored in the literature. In this paper, the effect of wear on (i) the tensile strength and (ii) the fragment protective performance of fabrics packs containing a para-aramid woven fabric typical of those used to manufacture body armor was investigated. © The Author(s) 2011. Source

Titterton D.H.,UK Defence Science and Technology Laboratory | Carpenter S.R.,Porton Group
Imaging Science Journal | Year: 2010

Optical techniques have been developed to provide a relatively simple but effective homing heads for guided weapons over the last five decades. The original approaches tended to use single detectors operating around "two microns" in the infrared. Improvements in detector technology have enabled significant enhancements to the performance of such seekers. Development of focal-plane array technology provided an opportunity to design and develop imaging seeker technology. This type of seeker technology appears to be resilient to conventional optical countermeasure techniques. This paper describes the development of an imaging infrared seeker to investigate potential infrared countermeasure techniques to defeat mechanisms. © 2010 Maney Publishing. Source

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