DSDS 24
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In 2024 we celebrate the 10th anniversary of the Cranfield Defence and Security Doctoral Symposia!
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Item Open Access Numerical modelling of hydrogen leakages in confined spaces for domestic applications(Cranfield University Defence and Security, 2024-11-13) Thawani, BonnyItem Open Access Ontology-driven knowledge graphs for personnel management within the UK Ministry of Defence: a conceptual overview(Cranfield University Defence and Security, 2024-11-13) Shufflebotham, A. Jack; Camelia, Fanny; Ferris,TimOntology-driven knowledge graphs visualise complex relationships between entities such as people and concepts. This conceptual paper explores the potential for using ontology-driven knowledge graphs to enhance personnel management within the Ministry of Defence (MOD). It reviews existing literature on ontologies, structured frameworks to store domain knowledge based on relationships between data, and knowledge graphs and outlines the concept of an ontology-driven knowledge graph for a skill management system. The paper argues that this approach can provide a unified, standardised method for managing personnel skills, improving decision-making, and enhancing operational efficiency. A further benefit identified is the potential for the system to be expanded to exchange information with other systems, such as the NATO Defence Planning Process (NDPP), allowing external data to improve the quality of inferences made by the system.Item Open Access Environmental concerns when utilizing detonation as the clearance method for dumped munitions(Cranfield University Defence and Security, 2024-11-13) Sharma, Bhumika; Webb, Sally; Temple, Tracey; Coulon, FredericCommon methods for clearing dumped munitions include low-order and high-order detonations. Low-order detonations produce subsonic explosions, typically leaving behind large explosive fragments, while high-order detonations involve supersonic explosions, usually destroying the entire munition. However, both methods may result in incomplete combustion and the release of explosive materials into the aquatic environment. Additional environmental impacts include noise pollution, shock waves, metal toxicity, and the spread of bomb fragments. To therefore estimate the detonation hazards further experiments were conducted under controlled conditions using six 1000L Intermediate bulk container tanks. Explosive charges were detonated at both low-order and high-order detonations. On average, the low-order detonations (Tanks A & B) left 8.76 ppm of explosive residues, while high-order detonations (Tanks C & D) left significantly less residue, averaging 1.18 ppm. These values were based on a starting explosive concentration of 115 ppm before detonation. The findings confirmed that low-order detonations leave more explosive residue, leading to a higher risk of toxicity. High-order detonations, though resulting in less explosive residue, release fragments at high velocity, posing a serious environmental threat and increasing the risk of accidental explosions.Item Open Access High-rate, fracture testing methods(Cranfield University Defence and Security, 2024-11-13) Sargeant, Ben; Davies, Catrin M.; Hooper, Paul; Cox, MikeIt is generally easier to break alloys at high speeds; in other words, fracture toughness reduces as strain rate increases. Understanding of these dynamic properties, by experimentation, reduces excessive conservatism in structural design, allowing for safe life extension of existing components and more efficient new constructions. This work investigates procedures to determine fracture toughness at elevated loading rates. Specific testing, used examples of different properties from Zinc, Aluminium and SA508-III pressure vessel steel, highlighting challenges in standard methods. Two methods of ‘rapid’ toughness testing have been contrasted – pendulum (Charpy) and servohydraulic (Very High Speed [VHS] Instron) test rigs. Charpy pendulums have a set energy input, hence a non-constant speed. Servohydraulic machinery adds energy to the system, maintaining speed. Both methods utilised sub-sized (10mm square bending specimens) specimens are recommended for high speed, minimising inertial effects and align with load capacities of high-rate instrumentation. Elevated speeds also make crack growth more difficult to monitor, compared to well understood static methods. Normalisation crack length monitoring (as recommended in standards) and a linear growth assumption from peak load have been utilised in this testing. Both methods produce similar crack length histories. Normalisation method anticipated the same crack growth initiation as peak load and showed a non-linear crack growth that aligns well with fracture surface features. However, the normalisation method is open to personal interpretation to fit data to a standard model. Results showed both testing methods to be dynamically invalid for brittle materials (Zinc and SA508-III steel at low temperature). Dynamic invalidity occurred as fracture occurred before (less than 93µs) kinetic energy effects are minimised - a requirement from standards for valid high-rate testing. Ductile materials (Aluminium and SA508-III steel at high temperature) were dynamically valid. Peak loads in Charpy data were clipped by relatively low sample rate. Peak loads in VHS testing were emphasised by high levels of ringing caused by impact shockwave resonating through the test rig. This let Charpy and VHS data to present different responses. Aluminium testing (low stiffness) loaded slow enough and damped ringing enough to produce comparable toughness data. Steel (higher stiffness) experienced these effects so much that data was incomparable. Improved system by higher sample rate Charpy instrumentation and higher mass and rigidity in the VHS test rig would reduce ringing (signal noise) and allow for better identification of accurate material response. The discrepancies between testing machines overwhelmed the effect of fixed energy input or speed controlled procedures.Item Open Access Two-photon dual-comb LiDAR for non-cooperative targets(Cranfield University Defence and Security, 2024-11-13) Nelmes, Alexander J. M.; Wright, Holly; Reid, Derryck