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Browsing Cranfield Defence and Security by Supervisor "Appleby-Thomas, Gareth J."
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Item Open Access The effects of 3D printed material properties on shaped charge liner performance(Cranfield University, 2019) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.Shaped charges operate by explosively loading a (typically metallic) liner to produce a jet travelling at extremely high velocity (9-12 km/s). Such explosive loading involves highly non-linear transient phenomena. As such, a very wide range of physical processes must be considered to enable accurate characterisation of such events – with material behaviour within these (pressure / strain-rate) regimes providing insight into problems ranging from shaped charge performance itself through to formation of new material phases at high pressures. Unlike other high strain impact events, the shaped charge phenomenon results in hydrodynamic material flow of the liner which is an integral aspect of the shaped charge design. As such, the study of shaped charge liners has been the subject of numerous scientific research studies for over 50 years since its discovery. When explosively loaded, the liner is stretched extensively during their elongation to form a jet. The jet length depends on the ductility of the liner material, and this is strongly linked to the microscopic crystal structure, which depends on the original material properties and the processes used to produce the liners. There are several processes currently used for liner production. This thesis outlines the different liner production techniques, their advantages/disadvantages and explores the potential of employing additive manufacturing (3D printing) technique for shaped charge liner production. As 3D printed parts are being considered as a possible replacement for conventionally processed parts, this PhD work fits into this long-term vision; with built parts compared in density and mechanical strength to their bulk material equivalents. More so, 3D printing is shown to present some potential benefits for the production of efficient liners including high precision, cost-effectiveness and the potential to realise customized geometries. The use of fine powders may also allow alternative microstructures to be produced with potentially interesting results. This element of the study forms the first part of this thesis, aimed at investigating the mechanism elucidating the performance of 3D printed liners processed through direct metal laser sintering process (selective laser sintering) and filament deposition modelling processes (Polylactic Acid). The next part of this work provided additional insights on the additive manufactured processed employed through investigation of the dynamic behaviour of polylactic acid, employed in the filament deposition modelling process and static (optical and scanning micrographs) observation of the laser sintered liners in their as - manufactured and deformed state, in comparison with traditional machined liners. Autodyn 2D numerical hydrocode was employed to understand how temperature influences the deformation pattern (grain refinement); providing new insights on liner deformation. Finally, a novel computational technique to determine the Virtual Origin of shaped charges was developed to provide a ready route to predict more accurate SC performance.Item Open Access An investigation into the effect of the gilding jacket on 12.7 mm armour-piercing projectile penetration of armour materials(Cranfield University, 2018) Lesmana, D.; Hameed, Amer; Appleby-Thomas, Gareth J.The influence of both the bullet jacket and projectile core hardness for 12.7-mm armour piercing (AP) rounds has been investigated using a variety of different experiments with the aim of optimising projectile performance. The research was designed to elucidate the role of these two elements in the penetration process, building on work elsewhere in the literature. A combination of forwards and reverse (target impacting stationary projectile) investigations provided insight into both penetration efficiency and resultant target failure modes. The results of these experiments, backed by a pressure-gauge based impact technique, were validated via numerical modelling. It was observed that the jacket appears to serve three inter-linked functions: pre-damage of the target; cushioning of the AP core and confinement of the core. Modifying the core hardness showed that penetration efficiency was maximised when this hardness was greater than / overmatched that of the target (Armox Advance) plate. This behaviour was more pronounced when a thicker (9 rather than 5-mm thick) target plate was employed, suggesting that projectile / target interaction time was of particular importance (a potential confinement effect). However, for the 9-mm target plates where overmatch did not occur, reduced penetration / a ‘ceramic-like’ response was observed. In a similar manner, the presence of a jacket had the greatest effect for thicker plates. However, this confinement effect was complemented by pressure gauge results which suggested that the presence of the jacket enhanced energy coupling into the target (and, in corollary, that the jacket prevented premature and excessive loading of the core). In turn, numerical simulations provided further evidence that the jacket appeared to be protecting (cushioning) the core on impact. However, these also highlighted the extent of pre-damage caused by the jacket.Item Open Access On the behaviour of porcine adipose and skeletal muscle tissues under shock compression(2014-06-10) Wilgeroth, J. M.; Hazell, P. J.; Appleby-Thomas, Gareth J.The response of porcine adipose and skeletal muscle tissues to shock compression has been investigated using the plate-impact technique in conjunction with manganin foil pressure gauge diagnostics. This approach has allowed for measurement of the levels of uniaxial stress imparted to both skeletal muscle and rendered adipose tissue by the shock. In addition, the lateral stress component generated within adipose tissue during shock loading has also been investigated. The techniques employed in this study have allowed for equation-of-state relationships to be established for the investigated materials, highlighting non-hydrodynamic behaviour in each type of tissue over the range of investigated impact conditions. While the adipose tissue selected in this work has been shown to strengthen with impact stress in a manner similar to that seen to occur in polymeric materials, the skeletal muscle tissues exhibited a ow strength, or resistance to compression, that was independent of impact stress. Both the response of the adipose material and tested skeletal muscle tissues lie in contrast with the shock response of ballistic gelatin, which has previously been shown to exhibit hydrodynamic behaviour under equivalent loading conditions. Plate-impact experiments have also been used to investigate the shock response of a homogenized variant of one of the investigated muscle tissues. In the homogenized samples, the natural structure of skeletal muscle tissue, i.e. a fibrous and anisotropic composite, was heavily disrupted and the resulting material was milled into a fine paste. Rather than matching the response of the unaltered tissues, the datapoints generated from this type of experiment were seen to collapse back on to the hydrodynamic response predicted for skeletal muscle by its linear equation-of-state (Us = 1.72 + 1.88up). This suggests that the resistance to compression apparent in the data obtained for the virgin tissues was a direct result of the interaction of the shock with the quasi-organized structure of skeletal muscle. A soft-capture system has been developed in order to facilitate post-shock analysis of skeletal muscle tissue and to ascertain the effects of shock loading upon the structure of the material. The system was designed to deliver a one-dimensional, at-topped shock pulse to the sample prior to release. The overall design of the system was aided by use of the non-linear and explicit hydrocode ANSYSR AUTODYN. Following shock compression, sections of tissue were imaged using a transmission electron microscope (TEM). Both an auxetic-like response and large-scale disruption to the I-band/Z-disk regions within the tissue's structure were observed. Notably, these mechanisms have been noted to occur as a result of hydrostatic compression of skeletal muscle within the literature.Item Open Access Optimisation of small arms defeat via dynamic jacket removal(2017-06-14) Roberts, A.; Appleby-Thomas, Gareth J.The majorities of studies into penetration by small arms have neglected the contribution of the jacket to the penetration event due to its small mass compared to the rest of the bullet. Recent research has suggested that the jacket does actually play a measurable role in the penetration of a target. This project has focused on the concept of dynamic jacket removal as an approach to optimise small arms defeat. This approach was envisaged to address the gap in current knowledge with regards to the role of the bullet jacket in the penetration of a target. Here, jacket stripping techniques were employed, elucidating underling mechanisms where armour piercing (AP) rounds were fired at target materials. Forward ballistic experiments were conducted, utilising conventional ballistic testing on an indoor small arms range as well as 30 mm and 50 mm smooth bore single stage light gas guns. To compliment this work, reverse ballistic experimentation was also undertaken on a 50 mm single stage light gas gun. Impact events were interrogated via a series of diagnostics including high speed video imaging, flash X ray radiography and depth of penetration testing. Experimental results were complimentary, providing insight into two key competing effects with regards to the jacket on penetration. These were the potential for the jacket to cushion / damp the impact, as well as the physical confinement resulting from the presence of the jacket itself around the bullet core. Further, these experiments also identified a potential optimum in terms of stripping plate design. In addition, to further investigate the role of the bullet jacket, sample cores and jacket materials were loaded both together and in isolation using a split Hopkinson pressure bar, with results in particular highlighting the cushioning effect of the jacket material. Limited numerical simulations were also produced using Ansys® Autodyn. These numerical results further elucidated the experimental work – again highlighting the importance of the jacket in terms of cushioning the impact event / reducing the subsequent pre-loading of the penetrating AP core. Overall, both experimental and numerical results showed that the bullet jacket does indeed aid in penetration. In corollary, in practical terms, jacket removal has the potential to aid in armour performance – with the experiments conducted herein providing insight into dynamic jacket removal. In terms of such stripping mechanisms, it was demonstrated that a plate thickness comparable to the calibre of the bullet appeared optimal. Further, results have also shown the importance of hardness and other material properties when considering the final defeat of an incident projectile through spallation.Item Open Access Shock propagation in a complex laminate(2014-06-10) Wood, D. C.; Hazell, P. J.; Appleby-Thomas, Gareth J.The shock response of a complex laminate has been investigated using a single stage gas gun, with manganin pressure gauges employed to investigate the shock profile. The complex laminate investigated was known by the acronym TWCP and is a tape wrapped carbon fibre composite with phenolic resin matrix. Carbon fibre composites are used in the aerospace industry due to their high strength to weight ratio, so understanding of different loading conditions is needed. To investigate the shock response of the TWCP, four weave orientations were studied. The orientations investigated with respect to the shock front were 0◦ (parallel to the shock front or perpendicular to the direction of travel), 25◦, 45◦ and 90◦ (perpendicular to the shock front or parallel to the direction of travel). As well as the TWCP the shock response of the matrix material, a phenolic resin Durite SC-1008 was also investigated. For the phenolic resin matrix material a non-linear Hugoniot was found in the US-up plane with the equation of US = 2.14 + 3.79up - 1.68u2 p. Such non-linear Hugoniot behaviour has been seen in other polymeric materials, e.g. PMMA. In the pressure-volume plane deviation was seen in the higher pressure data most likely due to the materials non-linear response. For the TWCP composite, linear Hugoniots were found for all four orientations with the corresponding equations shown below. • 0◦ US = 3.69 + 0.59up • 25◦ US = 3.45 + 0.73up • 45◦ US = 3.44 + 1.12up • 90◦ US = 3.96 + 0.46up The four Hugoniots are comparable in nature and it is possible to assign a single Hugoniot with the equation US = 3.56 + 0.84up through the majority of data points. The largest deviation from this “average” response was obtained from the 90◦ orientation due to the high elastic sound speed of this weave angle. Convergence was also seen between the Hugoniots in the US-up plane towards the higher up values (approximately 1 mm μs−1). In the pressure-up plane there was very little difference between all of the experimental data, meaning that for the stress in this material, orientation makes no difference.Item Open Access The shock response of biomaterials(Cranfield University, 2018) Fitzmaurice, B.; Appleby-Thomas, Gareth J.; Painter, JonathanThe shock response of microorganisms is of particular interest to many different areas of research including, but not limited to: asteroid and meteoritic impacts and origins of life; food sterilisation; and deep-sea organisms. The primary interest behind the investigation presented in this thesis is the origins of life and how, if life began elsewhere in the universe, it could survive transfer from one planetary body to the next. This ties in with the theory of panspermia and suggests that life on Earth, or its building blocks, may have originated elsewhere in the universe and was transferred here via an asteroid or meteor. Aside from the many other caveats that travel through space would present to an organism, such as extreme temperatures and ionising radiation, to survive a meteoritic impact onto a planetary body would be to survive extreme shock pressures as well. The purpose of this investigation, therefore, was to examine a number of organisms under quasi-one-dimensional shock loading conditions in order to assess the organisms’ response to shock pressure. The microorganisms chosen were Escherichia coli NCTC 10538 and Saccharomyces cerevisiae ATCC 18824, two model organisms, a prokaryote and a eukaryote, respectively, whose biochemistry is well characterised. The shock loading experiments were carried out in a 50 mm bore single stage gas gun using the plateimpact technique. The bio-samples were contained within a capsule system that allowed them to be safely contained and retrieved after the shock so that their growth rates could be assessed. E. coli was subjected to shock pressures ranging from 0.55 to 10 GPa under various different shock conditions, yielding growth rates of 6% to 0.09%, respectively. S. cerevisiae was shock loaded to from 0.49 to 2.33 GPa with resulting growth rates ranging from 1.8% to zero growth. Additionally, to probe further into how life forms of varying complexity might respond to these shock pressures, the multicellular organism, Artemia salina, was shock loaded under the same conditions, but only up to a maximum pressure of 1.5 GPa. It was noted that Artemia cysts showed hatching rates of up to 18% at this pressure, but this was not always without residual damage to the shell and the embryo within. Since pressure gauges could not be attached to the target capsule due to the complexity of the set-up, validated numerical models had to be employed to interrogate the pressures occurring within the sample. This also gave an indication as to the type of loading occurring within the sample. It was also desired to measure temperatures occurring during shock loading and to explore methods to better control this so that samples could be shocked to a particular pressure, while still controlling temperature. This was achieved using a novel type of flyer plate called Surfi-Sculpt® while validated numerical models were again used to estimate peak temperatures inside the capsule containing the biological sample. From the findings of a variety of shock experiments carried out throughout this project, a number of mechanisms were proposed to explain some of the results seen, providing insight into how microorganisms in particular might survive high shock pressures.Item Open Access Smurf : A reliable method for contextualising social media artefacts(2020-02) David, Anne; Morris, S; Appleby-Thomas, Gareth J.This research aims to evaluate whether artefacts other than the content of user com munication on social media can be used to attribute actions or relationships to a user. Social Media has enhanced the way users communicate on the Internet; providing the means for users to share content in real-time, and to establish connections and social relationships with like-minded individuals. However, as with all technology, social media can be leveraged for disagreeable and/or unlawful activities such as cyber bullying, trolling, grooming, or luring. There are reported cases where evidence from social media was used to secure convictions; for example, the tragic cases of Ashleigh Hall in 2009 and Kayleigh Haywood in 2015. The social media evidence e.g. the messages sent to the victim to arrange a meet up was used to link the suspect to the victim, and attribute actions to the suspect; in addition to other physical evidence presented as part of the case. Investigations with elements of social media is growing within digital forensics. This reinforces the need for a technique that can be used to make inferences about user actions and relationships, especially during a live triage investigation where the information needs to be obtained as quickly as possible. This research evaluates the use of live triage in the investigation of social media interactions, in order to determine the reliability of such a technique as a means of contextualising user activity, and attributing relationships or actions to a user. This research also evaluates the reliability of artefacts other than the actual content exchanged on social media; in the event that the content of communication is not immediately accessible/available to the investigator. To achieve this, it was important to break down the events that occur before, during and after user activity on social media; followed by the determination of what constitutes communication content in the context of this research. This research makes the following contributions: establishes a method for the cat egorisation of social media artefacts based on perceived user activity; communication content was characterised, thus highlighting evidential data of interest from user social media activity; the criteria for assessing the reliability of social media artefacts in a live triage investigation was proposed; a novel framework for social media investigation was developed with a Proof of Concept (PoC) to test its viability. The PoC demonstrates that it is possible to attribute actions or relationships to a user, using artefacts other than the actual content exchanged on social media.