Cranfield Defence and Security Doctoral Symposia
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The CDS Doctoral Symposia is the only UK conference to provide research students and early career researchers in defence and security with an opportunity to present their work to a sector-wide audience. Covering both technology and social sciences research, contributions include paper presentations, a 3MT (three-minute thesis) competition, digital images and posters.
In addition, there are plenary talks from thought-leaders, as well as opportunities to interact with industry, publishers and other employers of defence and security researchers.
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Browsing Cranfield Defence and Security Doctoral Symposia by Subject "'Additive Manufacturing'"
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Item Open Access 4D printing of Magnetic Shape Memory Alloys(Cranfield University, 2022-01-14T15:44:56Z) Milleret, AnastassiaMagnetic shape memory alloys (MSMA) are ferromagnetic materials exhibiting a plastic reversible transformation when subjected to a magnetic field. This transformation occurs within few milliseconds, making them good candidates for ultra-fast actuators. Previous studies have reported an increase of the shape memory effect in bamboo-like Ni-Mn-Ga structures. Thus, 3D Printing, using Laser Powder Bed Fusion (l-PBF), is a potential manufacturing approach to fabricate near-net-shape textured MSMAs structures. This study investigates the influence of l-PBF process parameters (laser power, scan speed, hatch spacing and scanning strategy) on the relative density and the microstructure of bulk and lattice specimens made from a gas atomised Ni-Mn-Ga powder doped with excess Mn. The as-built bulk samples showed a high relative density, up to 98% with a homogenous 14M structure and a ferromagnetic behaviour. The residual porosity in the bulk material is mainly due to gas voids, lack of fusion and cracking. Fabrication of lattice structures at a low laser power (70W) and scan speed (450 mm/s) resulted in a significant decrease in cracking. The effect of process parameters on the strut’s geometry was also investigated, in addition the influence of the lattice geometries on the magnetic properties. Microstructural analysis revealed a layered microstructure with a stripe-like surface relief that originated from the presence of martensitic twins within the sample. Further work will focus on developing a new design to enhance the magnetic properties.Item Open Access Additively Manufactured (3DP) thermite structures vs conventionally manufactured equivalents(Cranfield University, 2020-01-09 10:23) McGee, ChristineResearch into additive manufacturing (AM) has been steadily expanding over the past five decades. Where once only polymeric materials could be reliably printed, AM has been adapted to print with a range of materials such as biological, metallic, ceramic and even foodstuffs. The advantages of manufacturing in an additive manner include; a) a layer-by-layer approach allows the creation of architecturally complex structures, b) a reduction in weight, c) lessening of waste and d) the ability to create parts that are otherwise difficult or too costly to produce. Pyrotechnic materials, including thermite, are used in a wide range of commercial and defence applications. However, hazards present during manufacturing and storage have resulted in major accidents around the world, with subsequent loss of life and in some cases loss of public infrastructure. AM, using a dry powder printing technique means that parts can be manufactured on demand, reducing the need for storage of large volumes of fully formed products or mixes, thus increasing the safety over lifetime of a product.The performance of pyrotechnics materials is dependent on a number of properties, including chemical composition, thermodynamic properties and physical form. In combination with composition, architecture could be utilised to understand and control these properties. A bespoke printer capable of additively manufacturing pyrotechnic materials has been constructed with the aim to explore this research area. In this paper, we discuss the development of the AM technique and methodology for the burn test experiments. We conclude with the results from the burning of AM thermite structures and compare their performance with conventionally prepared equivalent thermite examples.Item Open Access Assessing the suitability of highly filled energetic composites for additive manufacture(Cranfield University, 2020-11-27 14:40) O'Donnell, MichaelThere is currently significant interest in the development of additive manufacturing (AM) techniques suitable for various energetic materials, such as explosives and propellants. One potential approach in this application space is to use extrusion-based techniques, such as Direct Ink Writing (DIW), to print highly solids filled pastes based upon uncured polymer bonded explosives (PBXs) or composite propellants. In supporting the development of these techniques, it will be important to develop an understanding of how the rheological properties of the materials affect their overall printability, which can be defined as their suitability for a particular AM approach. Such an understanding could enable rapid selection and optimisation of suitable technologies or formulations based upon measurable parameters.This paper reviews the printability of energetic materials in extrusion-based systems, and considers applicable approaches, rheological models and experimental techniques. The design, assembly and testing of custom apparatus for assessing the extrusion properties of an energetic paste are also discussed.Item Open Access Microstructure and Mechanical Properties of Inconel 718 and Inconel 625 Produced Through The Wire + Arc Additive Manufacturing Process(Cranfield University, 2022-01-12T12:26:44Z) James, WilliamIn developing the wire + arc additive manufacturing (WAAM) process for heat resistant alloys used in high-speed flight applications, structures were built from nickel-based superalloys Inconel 718 (IN718) and Inconel 625 (IN625). In this paper, wall structures were deposited in both superalloys, using a plasma transferred arc process. The microstructure was analysed optically and under SEM; both alloys were seen to be of typical dendritic structure with long columnar grains, with little variation between the alloys. The findings suggest that the structures included significant segregation of heavy metals, with potential Laves phases and δ-phases also found across the alloys, which showed significantly more segregation of Nb and Mo at the grain boundaries and inter-dendritic regions. The alloys also underwent room temperature mechanical testing, in addition to this IN625 specimens were tested after a solutionising and ageing treatment. Hardness measurements indicated that in general the WAAM process has the effect of increasing material hardness by approximately 10%, when compared to wrought alloy in a solutionised state. In IN625 the heat-treated specimens showed an increase in hardness of around 6%, when compared with its as-deposited condition. Elongation in IN625 showed much greater values. Overall, IN718 showed a greater strength with less elongation than IN625. A comparison between both alloys and their stated maximum UTS and YS values from literature revealed that WAAM built IN718 and IN625 in its as-deposited condition can achieve just over half the maximum achievable UTS, with no post-process treatment. The heat-treatment process tested in IN625 marginally reduced the gap in UTS performance by 3.5%.