PhD, EngD and MSc by research theses (SATM)
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Item Embargo Safe online learning for nonlinear dynamical systems using control contraction metrics(Cranfield University, 2023-03) Osborne, Matthew; Shin, Hyo-Sang; Ignatyev, Dmitry; Tsourdos, AntoniosThis thesis aims to develop an online learning framework for a military fixed-wing aircraft that can adapt a control policy to unforeseen changes in the airframe’s flight dynamics. This is an active area of research and a significant challenge for high dimensional non linear systems due to the inherent safety risks and computational challenges of solving exponential time algorithms. The research achieves this aim by providing an extensive survey of safe online learn ing approaches for nonlinear systems by assessing each technique with the aid of key performance metrics. Two critical performance metrics are the reliability and time com plexity of the approach taken. To support the survey a benchmarking study of salient techniques provides further evidence to support the findings of the literature survey to identify promising avenues of research. A generic safe learning process is defined and a convex optimisation learning pipeline is developed to handle nonlinear system identification and online controller synthesis via control contraction metrics. The developed pipeline is applied to a longitudinal simulation of an F-16 aircraft using high-fidelity wind tunnel data. The gap in knowledge around the application of control contraction metrics to aircraft designed to meet flying qualities requirements based on linear time invariant theory is bridged. A novel cascaded two loop algorithm is developed to explicitly place the eigenvalues of the inner and outer loop of a differential feedback controller. Further a parameterisa tion of a robust controller is shown to better optimise the performance relative to flying qualities specifications. Conditions for a hybrid linear sum of controllers is shown to provide a stability guarantee for a mixed controller that enables a performance trade-off of each approach. The performance of the developed controllers is demonstrated on six damaged aircraft profiles to assess the robustness and transient characteristics for each method based on a forty second flight trajectory. The variation in nonlinear damage profiles illustrates the limitations of a linear ap proximating function for three nonlinear deviations. We show that the robust quadratic regulator controller generates a smoother transient response compared to the exponential contraction controllers. The two-loop contraction metric controller improves the rise-time performance compared to a single loop but is less robust to damage variations. The out come of the research is a greater understanding of the application of contraction-based controllers and the effect of tuning parameters for a robust controller with potential for a reinforcement learning algorithm. Further a method to hybridise control policies is proposed and a loop shaping method using contraction based linear matrix inequalities developed with potential application to cascaded systems.Item Open Access Investigation of an Atmospheric Pressure Plasma device for reduction of water use in sustainable cleaning of concentrating solar power mirrors(Cranfield University, 2023-06) Gobey, Katherine; King, Peter; Sansom, ChrisConcentrating Solar Power (CSP) is a method of renewable electricity generation that uses large areas of mirrors, that reflect and focus the sun’s energy onto a receiver which is then used to heat water to power a conventional steam turbine, generating electricity. These plants are typically located in areas with consistently high levels of sunlight which are typically arid desert areas where sand and dust is deposited onto the mirrors, reducing their reflectivity and thus the plant’s output. Conventional mirror washing consumes huge quantities of water, which is costly and incurs ethical and environmental concerns in areas already experiencing water scarcity. This work investigates the use of an atmospheric pressure plasma to induce a super-hydrophilic surface on the soiled mirrors which are then able to be cleaned with significantly lower quantities of water. Characterisation of the plasma torch is conducted, and surface energy modification effects investigated with regards to water spreading, evaporation, and travel. For cleaning trials, solar type mirrors were artificially soiled with sand gathered from a CSP plant, then plasma processed before being conventionally washed with water. Mirrors that were subject to soiling were successfully washed, as determined by reflectance measurements, with up to 87.5% less water than mirrors exposed to the same artificial soiling procedure but without plasma processing prior to washing. Plasma processed samples also exhibited self-cleaning properties when subject to condensation trials, mimicking overnight dew formation. There was no observed effect in either reduction or exacerbation of subsequent resoiling of plasma processed samples. Fundamental processes behind these effects are discussed and the application and implication of the work are considered.Item Open Access Grain structure control of titanium alloys during wire + arc additive manufacturing(Cranfield University, 2023-07) Wainwright, James Christopher Julian; Willams, Stewart; Ding, JialuoPrior-β grain structure control of titanium alloys during Wire + Arc Additive Manufacturing (WAAM) is reliant on post-processing following deposition. Multiple methods are typically employed including cold working, melt pool agitation, inoculation and constitutional additions, all of which have distinct limitations. This research has demonstrated prior-β grain structure control in the as-deposited condition whilst utilising a stable deposition process. Prior-β grain structure control of Ti-6Al-4V was achieved through the reduction of the specific energy density of deposited material (SED). As SED decreased, the thermal gradient and potential for constitutional supercooling increased. A linear thermal gradient approximation was calculated via pyrometry to record the melt pool temperature. The SED was controlled via the wire feed speed and fixed energy input. It was determined that SED did not affect the peak melt pool temperature. Instead, arc shading was responsible for the cooling of the melt pool. Electron back-scattered diffraction (EBSD) analysis demonstrated a refinement of the prior-β grain morphology and weakening of texture. Analysis of the prior-β grain boundary misorientations demonstrated that as SED reduced, the misorientations had a propensity to the Mackenzie distribution. However, distinct peaks of 51° <110>β and 60° <111>β misorientations were observed and the tilting of grains to the deposition direction. The SED hypothesis was tested using various process parameters and additional titanium alloys, Ti-6Al-2Sn-4Zr 2Mo and Ti-5Al-5Mo-5V-3Cr, which had an increased potential for constitutional supercooling. It was determined that SED was not the primary mechanism behind prior β grain refinement. Instead, dendrite twinning in the {332}β <113>β and {112}β <111>β during solidification characterised by 51° <110>β and 60° <111>β misorientations respectively, as melt pool curvature, measured by the length/depth ratio proxy, increased. The single energy source deposition was limited by the reliance of melt pool shape on the SED. Therefore, the applicability of a scanning laser and arc multi energy source (MES) system was investigated for the deposition of Ti-6Al-4V. It was demonstrated via optical microscopy that the bead width, height and melt pool length could be independently controlled from the SED. Using the MES system various melt pool length/depth ratios were deposited whilst maintaining an equivalent SED. This confirmed the melt pool shape as controlling factor of the prior-β grain structure morphology via EBSD analysis.Item Open Access Physicochemical and nanomechanical behaviour of 3d printed pegda hydrogel structures for tissue engineering applications(Cranfield University, 2023-03) Hakim Khalili, Mohammad; Impey, Susan A.; Aria, Adrianus Indrat; Goel, SauravPoly(ethylene glycol) diacrylate (PEGDA) hydrogels are well established in tissue engineering and organ-on-chip applications as scaffolds for 3D templates in aqueous environments due to their high water content, biocompatibility and low toxicity. The versatility of PEGDA hydrogels as a platform for cell encapsulation and tissue engineering is attributed to their ability to be modified in various ways, including concentration, molecular weight, and polymerisation technique. Since properties of the PEGDA host material will affect the functionality of the cells and tissues, and vice versa, a key missing feature of the currently developed screening solutions is the lack of proper understanding of the behaviour of the 3D printed PEGDA soft support structures holding living tissues in a dynamic human like tissue microenvironment. Thus, the aim of this research is to demonstrate repeatability and reliability in the measurement of physicochemical and nanomechanical properties of multilayer 3D printed UV crosslinked PEGDA hydrogels for use in organ-on-chip devices. The research offers insights into long term stability of hydrogels through studying how changes in both environmental and printing parameters can be extrapolated to other biomaterials for benefit of other tissue engineering applications. Recent advancements in the use of PEGDA hydrogels for tissue engineering are reviewed, with a focus on bulk cross-linking and 3D printing synthesis methods. Characterisation methods for 3D printed PEGDA hydrogels are also discussed. The current state of development of biomedical applications, particularly in organ on-chip devices, is highlighted. The thermal response of multilayer PEGDA hydrogels made using in-house projection lithography was compared to monolithic hydrogels created through bulk photo-cross-linking. The results indicated that the volume of multilayer PEGDA hydrogels changes in response to the temperature with dimensional change between +10% and -11.5%, and also displaying an anisotropic characteristic where the axial dimensional change was higher than the lateral dimension. The results also confirmed the swelling behaviour to be reversible between 8 and 45 °C. The nanomechanical properties of monolithic and multilayer PEGDA hydrogels fabricated through bulk cross linking and layer-by-layer projection lithography were studied. The findings showed that an increase in the number of layers results variation in axial elastic modulus between 1.69 and 0.67 MPa. Additionally, the research examines the structural heterogeneity of 3D printed hydrogels which is linked to the degree of cross-linking of the printed layers and showed variations in lateral elastic modulus between 2.8 and 11.9 kPa. The results suggest that by controlling the cross linking throughout the 3D printed structure, the surface nanomechanical properties of the hydrogels can be manipulated to direct cell attachment and adhesion in specific regions within the structure, offering potential for future improvement in the reproducibility and reliability of 3D printed hydrogels for tissue engineering and organ-on-chip applications.Item Open Access Health monitoring of cavitation erosion on airframe fuel pumps(Cranfield University, 2023-09) Verhulst, Tedja; Lawson, Craig; Judt, DavidAircraft maintenance is a critical aspect of operations that can lead to substantial financial savings if improved. The fuel pump is a vital component of the entire aircraft, ensuring fuel delivery to the engine. Cavitation is common in these pumps, leading to erosion and reducing the pump's remaining useful life. Therefore, the main objective of this work is to develop a viable health monitoring method to diagnose cavitation erosion, where few solutions exist. Initially, a literature review is conducted to identify knowledge gaps and opportunities for technology transfer related to current Health Monitoring (HM) technologies for airborne pumps. Four sensing methods, pressure, flow, current, and temperature sensing, are shortlisted based on their past applications and suitability for an aircraft fuel system installation. A hybrid health monitoring scheme consists of a Computational Fluid Dynamics (CFD) simulation, a model running on Simscape, and an experimental test rig. Live experiments are conducted to validate the simulation methods, enabling the testing of scenarios on a wide range of boundary conditions. The simulations demonstrate strong alignment with the experimental data and successfully distinguish the different levels of erosion. Three out of the four tested sensing methods are sensitive enough to distinguish the different levels of erosion, but each method has its advantages and limitations. Temperature sensing is not useful for health monitoring as the ambient environment strongly influences its results. Despite the success of the developed health monitoring schemes, there is a need for further research and development into more sophisticated health monitoring algorithms before the technologies can be widely implemented on aircraft.Item Open Access Cybersecurity of embedded systems a novel approach for detecting cyberattacks based on anomalous patterns of resource utilisation(Cranfield University, 2022-01) Aloseel, Abdulmohsan; Al-Rubaye, Saba; Zolotas, ArgyriosAn embedded system (ES) is a processing unit that has been embedded into a larger cyber-physical system (CPS) to steer its functions. The ES has played an essential role in modern life, where it has been used widely in sensing, controlling and computing for countless applications in different domains, such as the internet of things (IoT), smart cities, healthcare, transportation, communication, military, transportation, gas distribution, avionics and national infrastructures. Due to its widespread application in different domains and its evolution in conjunction with many key technologies, it is crucial that these systems are secured against cyberattacks as the ES has the same generic security goals – confidentiality, integrity and availability – as conventional computer systems. Although the ES is exposed to the numerous and unpredicted security threats that are experienced by conventional computer systems, it is significantly limited in its ability to manage the advanced security solutions that are implemented on conventional computer systems. The limitations in resources of the ES, due to its identity or characteristics, impose tight constraints on both its communication and computing capacity, thereby hindering the implementation of advanced security solutions. Thus, the cybersecurity of an ES is limited by constraints on its resources rather than by the absence of advanced security solutions. There is an urgent need, therefore, to develop security solutions that are compatible with the capabilities of the ES. This study tried to bridge the gap by addressing both theoretical and empirical aspects of ES cybersecurity. The study can be divided into three main blocks. The first block identifies the key factors, involved parties or entities, and creates the cybersecurity landscape for embedded systems (CSES), while considering the conflict between the requirements for cybersecurity and the computing capabilities of an ESs. Additionally, twelve factors influencing CSES have been extracted and identified based on the direction of the research. These factors have been used to shape a multiple layers feedback framework of embedded system cybersecurity (MuLFESC), with nine layers of protection. It has been developed in line with an expanded model of risk assessment metrics, which will enable cybersecurity practitioners to evaluate the security countermeasures of their systems and assist in the development of more comprehensive solutions for CSES. A novel security approach, called anomalous resource consumption detection (ARCD), was developed in the second block of this study. This involved the design of a testbed to provide a realistic hardware-software environment to analyse an example application of an ES. A Smart PiCar was run repeatedly under different operational conditions – typical conditions and under attack. The data of seven designated parameters based on seven statistical criteria was analysed to measure the range, pattern of performance and resource utilisation. The results from this statistical analysis demonstrated the potential for defining a standard pattern for the resource utilisation and performance of the embedded system due to a significant similarity with the values of the parameters at normal states. In contrast, the results from the attacked cases showed a definite and detectable impact on the consumption and performance of the resources of the ES, which presented anomalous patterns. The ARCD method can be implemented as an additional layer of protection to detect cyber-attacks in an ES, where a septenary tuple model, consisting of seven parameters, is the core of the detection mechanism. In the final block, the ARCD approach has been placed within an architectural framework, which may pave the way for software engineers to build secure operating systems in line with the capabilities of the ES. The architectural framework was developed after the efficiency of the approach was computationally validated by machine learning. This involved the design of a classifier and predictor model to find the predictive accuracy percentage in terms of separating patterns of anomalous performance and resource utilisation from the typical pattern. Based on the confusion matrix, the prediction accuracy for classifying anomalous patterns compared with default patterns revealed promising results, thus proving the effectiveness of the ARCD approach. The results confirmed very high prediction accuracies as regards distinguishing anomalous patterns from the typical patterns.Item Open Access Rotary mount design for a chromatic confocal sensor, involving additive manufacturing and an opened air bearing(Cranfield University, 2018-02) Sanz, Claude; Giusca, Claudiu; Morantz, Paul; Shore, PaulIn the field of high energy physics, the characterisation and positioning in space of a wire with a diameter of 0.1 mm is one of the steps to increase the precision of future accelerators’ pre-alignment. This reference wire is measured within a high accuracy Coordinate Measuring Machine (CMM) to reduce its positioning uncertainty. No sensor could measure the wire position within the targeted uncertainty. This thesis addresses this issue by proposing a design for the Shape Evaluating Sensor: High Accuracy & Touchless (SESHAT). The SESHAT operates a chromatic confocal sensor. The sensor is fixed to a rotor with a radial opening to allow the stretched wire to traverse it. This rotor is guided by a high precision air bearing controlled by a piezoelectric actuator. The mass limit for the stylus system of the CMM entailed the additive manufacturing of a hollow rotor. The high likelihood of particles on the wire surface involved a form deviation capability for the SESHAT, to reduce position measurement uncertainty. The aim of the research was to design a sensor enabling the Leitz Infinity CMM to perform non-contact form measurement on the PACMAN reference wire to permit its axis positioning with an uncertainty such that 3σ < 0.5 µm. The novelty emphasised in this thesis is focused on three main contributions. The form measurement uncertainty reduction obtained by using a chromatic confocal sensor for non-contact measurement on a wire surface is the first contribution. A mathematical model describing the behaviour of air pads over a through hole in the bearing surface composes the second contribution to knowledge. The demonstrated ability to obtain a micrometric form deviation on a rotary symmetric complex shape generated by additive manufacturing of titanium is the third contributionItem Open Access Framework for anomaly detection of flight-crew deviation from standard operating procedures: a data analytics approach.(Cranfield University, 2022-05) Igenewari, Vivian Rowoli; King, Steve; Jennions, Ian K.Deviations from Standard Operating Procedure form a significant part of aviation incidents today involving loss of lives and other related costs. Previous work tailored towards detecting procedure deviations in flight operations have primarily been rule-based. The current method being used by airlines to detect operational, component fault and crew action anomalies within flight data is a rule-based Exceedance Detection technique which is only able to flag up known flight abnormalities. Lately, Anomaly Detection methods have been introduced to find, not just known, but unknown anomalies that deviate from the expected normal flight profile. There is a need to explore flight data using anomaly detection methods to detect subtle underlying misunderstandings of the flight crew in relation to deviations from laid down procedures which do not lead to incidents, under most conditions, or are hard to detect by the state-of-the-art method. However, these detection methods are limited in the type of anomalies they can find when implemented individually on heterogeneous flight dataset thereby missing critical anomalous flight incidents. In this work, Flight Data Recorder data of a fleet from a United Kingdom airline and a structurally similar publicly available dataset from the National Aeronautics & Space Administration are used. This study proposes a framework integrating an Ensemble anomaly detection technique (combining individual anomaly detection techniques into a single method) and a Case Based Reasoning system. The findings reveal that combining existing anomaly detection methods into an Ensemble can detect a wider variety of anomalies that were not flagged by individual methods. Also, the proposed reasoning design aims to filter for procedure deviations from the pool of anomalous incidents detected by the Ensemble. Detecting these procedure deviations is not just aimed at complementing crew training, improving procedures, and understanding automation design to put in place mitigation strategies but also to aid accident investigations by informing of accident flights with procedure deviations that may have been contributing factors.Item Open Access Creating a framework for community integration of urban air mobility.(Cranfield University, 2022-03) Organ, Aaron John; Mason, Keith; Rothe, HenrikTechnological advancements in propulsion systems, alternative fuel, battery power and storage, and autonomy have led to the development of a new generation of aircraft. These enabling technologies inclusive of Small Unmanned Aircraft Systems (sUAS), Large Cargo Unmanned Aircraft (LUCA), and electric Vertical Take-off and Landing (eVTOL) or electric Conventional Take-off and Landing (eCTOL) aircraft fall under the umbrella term of Advanced Air Mobility (AAM). The current literature, in addition to regulators and the industry, is heavily focused on the aircraft and technology integration. This research contributes to a literature gap concerning ground infrastructure and community integration of AAM. The research aims to provide a framework of next steps relevant to state and city planners and policy makers. Subject matter experts from key AAM stakeholder groups were consulted through the execution of semi-structured interviews to produce a rich dataset of the issues and challenges of integrating AAM into the state and city’s transportation systems. The systematic approach of thematic analysis was used to identify top themes and sub-themes. The results identified AAM success keys, potential use cases, anticipated benefits of AAM, anticipated obstacles to AAM adoption, and stakeholder roles at the city, state, and federal level. These results have provided a framework for cities and states of what to do in the initial phases to integrate Advanced Air Mobility technologies into their existing transportations networks for a more sustainable and robust system.Item Open Access Carbon nano materials based composites for energy storage.(Cranfield University, 2022-04) He, Shojun; Ayre, DavidThe development of human industrial technology has increased the requirement for electric energy. At present, the rapid development of various smart devices has led to an increasing demand for high-performance batteries. The emergence of various wearable devices has led to a need for flexible electrodes. Aerogels and paper, as two good flexible porous materials, have attracted many scholarly studies in recent years. Combining carbon materials, which have excellent electrochemical properties, with aerogel and paper can result in flexible electrodes with good performance. This research presents a series of aerogel and carbon paper samples prepared using three different production processes. For the aerogel samples, the effects of graphene addition and manufacturing route were investigated. The study resulted in a recommended material and process to produce a porous aerogel sample with high electrochemical cycle stability. For carbon paper samples, the relationship between variables such as surfactant, paper, conductive material and the sample properties was examined. Initial work indicates that carbon paper manufacturing routes are simpler than others reported elsewhere and provide materials that have electrochemical properties with potential for use as electrodes in supercapacitors and other energy storage devices. Of course, cost and environmental protection have also been considered in this project.Item Open Access Development of a framework to estimate the software obsolescence resolution cost of custom build real-time software.(Cranfield University, 2022-01) Rajagopal, Sanathanan; Erkoyuncu, John Ahmet; Roy, RajkumarSoftware plays an important role in the defence sector. Almost every project in defence has got software with various degrees of complexity and dependencies. Software obsolescence is one of the key cost drivers which has historically been assessed as part of the maintenance cost due to the lack of data/information and due to the fact that there are no tools, techniques, or framework to help with the software obsolescence management. Therefor it is key for the industry and Defence sector to address software obsolescence and to find an approachable way to counter the effect of software obsolescence. The aim of this research is to develop a software obsolescence cost analysis framework to predict the software obsolescence resolution cost of custom build real time software at early stages of the product life cycle. For the accomplishment of the aim, an extensive literature review on software obsolescence and its related themes was undertaken, a systematic case study with online survey corroborated the findings and revealed the current practices in the UK Defence sector. Further collaboration with 35 experts from industries led to undertaking a cognitive case study to enable the iterative development of Software Obsolescence Cost Analysis Framework. This was demonstrated by applying the framework to five case studies as part of expert validation. The novelty of this research is that it tries to solve an issue with significant real- world impact for which very little work exists with lots of real-world inputs from SME and real case studies. Cognitive case study with software experts is unique and has never attempted before to solve this issue. The research comes up with a novel way to quantify the costs for the very first time with strong input from primary data sources. The key limitation of the research is in the unavailability of any historic technical data.Item Open Access Developing a framework of leadership behaviours to facilitate the effective use of lean six sigma in manufacturing: the case of Jordan.(Cranfield University, 2022-03) Alnadi, Mohammad; McLaughlin, Patrick; Fan, Ip-ShingThis study aims to explore the leadership behaviours that facilitate the effective use of Lean Six Sigma, whereby organisations and leaders can realise the required behaviours to use the Lean Six Sigma successfully. Leadership is identified as one of the vital factors for the successful implementation of Lean Six Sigma. Thus, this research studies leadership from a behavioural lens. It would be helpful for organisations to get the expected benefits of Lean Six Sigma. An interpretive research philosophy is adopted; reality is constructed through social interaction in which people construct shared meanings and reality. A grounded theory methodology was used to collect and analyse the qualitative data. From that, identifying the required leadership behaviours was based and grounded on the themes that emerged from the data analysis. Twenty-seven interviews were conducted and, through analysing these interviews, thirty-six aspects of leadership behaviours emerged. The researcher made a constant comparison to let the aspects emerge during data analysis. These aspects were given to the participants in the focus group workshop to group them into core categories (themes). Then, ideal position descriptions for each theme were developed to describe what each theme looked like in the most effective and established organisations. The researcher adopted and relied on three sources to identify the possible leadership behaviours to develop the proposed framework. These sources are a focus group workshop, interviews analysis, and the literature. The framework is a series of leadership behaviours that target specific themes. The framework was validated through experts’ judgment from industry. The experts’ feedback was this framework is comprehensive and covers all topics. They believe that adopting these behaviours can lead to achieving the desired goal, which enhances operations efficiency. This research has contributed to facilitating the effective use of Lean Six Sigma by identifying the leadership behaviours required for the successful use of the Lean Six Sigma. Furthermore, it is novel in explaining how the leadership behaviours can support Lean Six Sigma; the themes’ descriptions explain how influence the use of Lean Six Sigma.Item Open Access A framework for enhancing knowledge sharing through social media in higher education institutions in the KSA.(Cranfield University, 2021-08) Alshalaan, Mohamed Nasser R.; Salonitis, Konstantinos; Patsavellas, JohnSocial media tools have changed the way individuals and academics impart, share content, inter-face, and team up. These days, social media is turning into an important stage for encouraging knowledge sharing and correspondence. The current research focuses on a framework for enhancing of the use of social media for knowledge sharing in higher education institutes (HEIs) in the Kingdom of Saudi Arabia (KSA) by using knowledge-sharing models and theories. The proposed framework was validated in the KSA academic sector. This research used semi-structured interviews with 31 participants from various departments in HEIs. The quantitative data were analysed using descriptive and inferential statistics. The qualitative data were analysed using a thematic analysis approach. The research identifies the factors influencing knowledge sharing through social media based on three aspects: individual, organisational, and technological dimensions. The contribution of this research includes a new framework derived from previous models and theories to investigate the potential factors that influence the use of social media for knowledge sharing. The interpretive structural models were applied based on the factors from the literature review and the findings from interviews. The findings lead to the development of a framework for the development of the knowledge- sharing process through social media in KSA HEIs. The proposed framework was validated using experts’ feedback. An interpretive structural model (ISM) as presented for a better understanding of the relationships among the critical factors. The ISM model contributed to the development framework of knowledge-sharing factors through social media. The proposed framework has the ability to identify potential factors and improve the knowledge-sharing process through social media. This research will help educational institutions to know how to support the use of social media tools for knowledge-sharing purposes by focusing on critical factors.Item Open Access Caught in the act: The structural pathway of liquid metals to vitrification monitored in situ by synchrotron X-ray diffraction.(Cranfield University, 2021-09) Stiehler, Martin E.; Georgarakis, Konstantinos; Jolly, Mark R.When a metallic melt is undercooled fast enough below its liquidus temperature, crystallisation can be avoided and a metallic glass, i.e. a metallic solid with amorphous structure, be formed. This kind of solidification is called vitrification. The prerequisites for this phenomenon are still not clear. An extensive review of the available relevant literature was carried out. To reveal the structural changes taking place at the atomic scale during undercooling and vitrification, data obtained by ultrafast synchrotron X-ray diffraction during aerodynamic-levitation experiments of different metallic-glass forming liquids was analysed. The complete pathway from temperatures well above the liquidus temperature during undercooling and vitrification down to temperatures well below the glass-transition temperature Tg was studied. During undercooling, a non-linear evolution of structural metrics in real as well as in reciprocal space takes place. Especially the height of the first maximum in the structure factor can be described by a structural analogue to the Curie-Weiss law. This behaviour was also found in published data re-analysed here. Indications of universal behaviour among the investigated alloys below a certain temperature as well as for a liquid-liquid crossover in Ti₄₀Cu₃₄Pd₁₄Zr₁₀Sn₂ were found. Small differences in the temperature dependence of the structural behaviour among the different alloys are possibly related to their different glass-forming abilities. To facilitate the analysis of the real-space structure the novel concept of the anti-shell was introduced. Temperature affects different length scales differently. Below Tg the structural behaviour is dominated by the Debye-Waller factor as well as by normal thermal-expansion behaviour. Above Tg an apparent negative thermal expansion of the first nearest-neighbour distance can be attributed to the influence of the structure-forming processes. In addition to short- and medium-range order, a third structural range for distances beyond the third nearest-neighbour is proposed. A disordering of the atomic structure of metallic glasses by the introduction of further alloying elements, facilitated by emergent effects among the components, could be demonstrated. The importance of the influence of global electronic interactions on structure formation was shown as well as their limitation to distances beyond the third nearest-neighbour.Item Open Access Structural dynamics and crack propagation behaviour under uniform and non-uniform temperature conditions.(Cranfield University, 2022-02) Kamei, Khangamlung; Khan, Muhammad Ali; Starr, AndrewThe robustness and stability of machinery depend on structural integrity. This stability is, however, compromised by aging, wear and tear, overloads, and environmental factors. A study of vibration and fatigue crack growth for structural health monitoring is one of the core research areas in recent times. The research is yet to input sufficient explanations about the dynamic behaviour of the structure under distributed temperature. The structural dynamics can be influenced by material microstructure, temperature distribution, and duration of exposure to the thermal environment. The applied temperature can cause significant variations in the modal response. The existing studies are limited concerning temperature change and compel extensive investigation in a crack and uncracked condition. In this research, the structural dynamics and fatigue crack propagation behaviour when subjected to thermal and mechanical loads have been studied. It investigates the modal parameters of uncracked and various cracked specimens under uniform and non-uniform temperature conditions. An analytical model considering the effective length of the beam is developed to analyse the modal response of the beam. Then, the model is modified to enumerate the modal behaviour of the beam in the presence of crack. The model is validated by experimental and numerical approaches. The experimental evaluation is conducted by considering three heating rates to attain the required temperatures. In the first case, ramping at 2°C/min is assumed as a slow heating rate. While ramping at 5°C/min and 8°C/min are assumed as moderate and rapid heating rates respectively. The heating rates are considered to compare the structural response changes. A small variation on modal parameters is noticed for different heating rates and when the applied uniform temperatures are changed to non-uniform temperatures, especially at elevated temperatures. This signifies heating at different rates has a slight effect while measuring the dynamic response of any mechanical system. The results showed that changes in modal parameters of the beam are associated with the change in temperatures and heating rate. Furthermore, this research substantiates the fatigue crack propagation behaviour of pre-seeded cracks. The propagated crack depths are measured based on pixels contains in the crack. It is found that propagated crack depends on applied temperatures and associated mass. The appearance of double crack fronts and multiple cracks are observed. The multiple crack appearance seems due to the selection of pre-seeded crack shapes. Hence, the real crack and pre- seeded crack are distinct and need careful consideration in crack propagation evaluation.Item Open Access Bead shape control using multi-energy source (mes) for wire-based directed energy deposition (ded) process.(Cranfield University, 2021-11) Chen, Guangyu; Ding, Jialuo; Williams, Stewart W.Independent control of layer width and height is essential to achieve a simultaneous high build rate with precision net shape and thermal control independent from deposition shape in the wire-based directed energy deposition (w-DED) process. Bead shape control using a multi-energy source (MES) method was studied to achieve independent control of layer width height of a bead for the w-DED process. This study was carried out in three stages: First, a plasma transfer arc (PTA) energy density measurement was conducted. A split anode calorimeter (SAC) was applied for the measurement of PTA energy density. A laser beam with a well-defined energy profile was used to calibrate the calorimeter without the complications of arc instability. An optimised centred grounded SAC device was introduced to reduce arc distortion. More symmetric arc profiles were obtained. The dynamic thermal characterisation of a scanning laser (SL) was then studied using both experimental and numerical approaches. SL experiments were conducted with different oscillation frequencies and laser beam sizes. An innovative solution dependent convection boundary (SDCB) method was introduced to reduce the element amount of the finite element (FE) model. Results show that the quasi-steady state SL can be applied as an equivalent stationary energy source. Finally, an SL-PTA MES system was introduced to study the MES bead shape control, a PTA was employed in the front to create an initial melt pool and melt the feedstock wire, and an SL was used behind the PTA to reshape the melt pool and precisely control the bead width. A bead shape control strategy was proposed by using the wire feeding rate to control the layer height and the scanning width to control the layer width. The experiment results verified that the SL-PTA MES has independent control of layer width and height.Item Open Access Development of NI3AL corrosion resistant coatings for SS347 heat storage components in presence of molten nitrate salt.(Cranfield University, 2020-07) Yasir, Sarah; Aria, Adrianus Indrat; Endrino, José L.Climate change is an inevitable global issue with long term consequences for the sustainable development. It is a crucial time to review this climate issue with ensured determination. There is a need and demand for alternative sources to generate power rather than the conventional burning of fuels due to impact on environment. Renewable energy sources are those natural reserves that are refilled continually, including wind, solar, biomass and geothermal. A number of technologies have been developed to use solar energy for power generation. Among them, an important feature of concentrated solar power plants is the potential to incorporate thermal storage. Thermal energy storage allows generation beyond sunset and in times of cloud cover. Several possibilities for heat transfer fluid and thermal energy storage have been identified. From a wide range of materials, molten nitrate salt is selected because of adequate heat storage and transfer capability. Different approaches to prolong life by suppressing corrosion have been suggested in the literature, coating is a promising option because coatings are believed to provide shield to suppress corrosion. Among different coatings, nickel aluminide has been claimed to possess high-temperature mechanical strength and it has a remarkable oxidation resistance performance as substrate component. Moreover, nickel aluminide has low solubility in the molten nitrate salt. Ni₃Al coatings are much preferred to be used as corrosion resistant coatings as they possess strength at high temperature, oxidation protection and creep properties. Among different deposition techniques, plasma spray has been identified as most applicable because it is versatile, adaptable, cost effective. It also has high deposition rate, deposition efficiency and less environmental impact, more importantly it is easy to scale up. Corrosion behaviour of stainless steel 347 (SS347) and Ni₃Al coated SS347 was investigated in molten nitrate salt (60wt% NaNO₃ + 40wt% KNO₃) immersion at 565oC for 500 hours intervals up to 3000 hours. A growth of stratified oxide layers was observed on SS347 sample surface comprising of NaFeO₂ , Fe₂ O₃ and Fe₃O₄ . The Ni₃Al coated SS347 samples were observed to undergo rapid oxidation within first 500 hours. Apparent Mass change for bare SS347 was 4 mg/cm²/yr, equivalent to oxide growth rate of ~ 5 µm/yr. Mass change for Ni₃Al coated SS347 was 29.8 mg/cm²/yr, equivalent to oxide growth rate of ~ 44.6 μm/yr for first 500 hours and 0.5 mg/cm²/yr, equivalent to oxide growth rate of ~ 0.7 μm/yr for 500 to 3000 hours. The results presented in this study suggest that Ni3Al coating supresses the formation of oxide layers on the surface of stainless- steel substrates and can be used to suppress corrosion in presence of molten nitrate salts. The fact, that Ni₃Al coated SS347 gives mass change of one order of magnitude lower than the bare SS347, it means that these coatings can be used to prolong the lifetime of bare SS347 in molten nitrate salt at 565oC, which is of relevance to thermal energy storage applications. The Engineering Doctorate portfolio is structured as an innovation report and five submissions. A personal profile and a report on international industrial placement are also included in the portfolio.Item Open Access Knowledge-driven business model canvas for business development of SMEs in the food sector in the gulf cooperation council.(Cranfield University, 2021-02) Alharbi, Bandar Fahad Mohammad; Al-Ashaab, Ahmed; Fan, Ip-ShingSmall and mid-size enterprises (SMEs) are the core engine of most economies around the world. Empowering SMEs with the right tools, especially those utilised to formulate business models, would help them thrive more successfully. This study aims to provide such business development support tools to the food sectors SMEs of the GCC. This research focuses on the SMEs in the Gulf Cooperation Council (GCC) processed food sector. First, an extensive literature review was conducted on business development and business development tools, the business models. It was found that the Business Model Canvas is the most advanced tool in the market, yet the model is not fully exploited in terms of business development and growth. A field study involving 36 companies within the GCC region's food industry was conducted. The findings indicated three main problems faced by SME’s: product-market-fit, business planning and finance. Hereafter, Lean start-up was applied in a case study on a frozen yogurt producer from the region. The findings from the case study showed that the lean start-up approach minimises the product-market-fit problem and, hence, provides a more explicit structure for business planning and finance. Furthermore, the case study findings were presented to six industry practitioners to evaluate the lean start-up method. Based on their evaluation; the model was modified to incorporate market regulations as an additional block. A set of measurement (KPI’s) was added to the model to develop a revised model named the Knowledge-Driven Business Model Canvas (KD-BMC). Finally, the KD-BMC was validated through a case study on two companies in the food industry in Saudi Arabia and further evaluation was gained from six experts in the field. Results of validation were discussed and concluded in the final chapter of this research.Item Open Access Aeroelastic analysis on a multi-element composite wing in ground effect using fluid-structure interaction.(Cranfield University, 2021-08) Bang, Chris Sungkyun; Temple, Chris; Konozsy, Laszlo Z.The present research focuses on an advanced coupling of computational fluid dynamics (CFD) and structural analysis (FEA) on the aeroelastic behaviour of a multi-element inverted composite wing with the novelty of including the ground effect. Due to the elastic properties of composite materials, Formula One (F1) car’s front wing may become flexible under fluid loading, modifying the flow field and eventually affecting overall aerodynamics. This research investigates the influence of elastic behaviour of the wing in ground proximity on the aerodynamic and structural performance by setting up an accurate the Fluid-Structure Interaction (FSI) modelling framework. A steady-state two-way coupling method is exploited to run the FSI simulations using ANSYS, which enables simultaneous calculation by coupling CFD with FEA. A grid sensitivity study and turbulence model study are preferentially performed to enhance confidence of the numerical approach. The FSI study encompasses everything from basic examination and measurement of the interaction phenomena using a single and double element inverted wing to the creation of a multi-objective wing design optimisation procedure. The computational results obtained from FSI simulations are assessed and compared with the experimentation with respect to surface pressure distribution, aerodynamic associated forces, and wake profiles. Concerning structure layups, ply orientation and core materials, the effect of various composite structure configurations on the wing performance is extensively studied. An efficient and unique decomposition-based optimisation framework utilising the response surface model is provided based on the aero-structural coupled analysis in order to enhance the wing design process' accuracy and efficiency while tackling aeroelastic phenomena.Item Open Access Development of a CFRTP manufacturing method to improve low velocity impact resistance of aerospace structures.(Cranfield University, 2020-08) Delporte, Yoan; Ghasemnejad, Hessam; Webb, PhilA continuous carbon fiber reinforced Polymer was manufactured using a Fused Deposition Modelling method. Current Fused Deposition Modelling machine are not able to manufacture Carbon Fiber Reinforced Thermoplastic Polymer composite therefore modification and novel designs needed to be made and integrated to the Fused Deposition Modelling machine to achieve a final product. To investigate the benefits of our composite a comparison with available composites on the market composed of similar materials needed to be performed. We investigated the different aspect of the requirements needed to manufacture test samples. We focused on manufacturing method able to integrate continuous Carbon Fiber simultaneously to a thermoplastic. In the slicing software a custom g code sequence has been developed to forward the continuous Carbon Fiber through the Bowden tube to the hotend. This procedure allowed the hotend to move freely between the layup of the printed part. Also C code library has been developed to analyse the geometry of the part to recognise the amount of Carbon Fiber, which needs to be pushed through the Bowden tube connected to the hotend. We investigated the mechanical properties as well as the process parameters of the individual materials used to manufacture our Carbon Fiber Reinforced Thermoplastic Polymer samples. In addition Carbon Fiber Reinforced Thermoplastic low velocity impact samples have been produced to investigate the potential of our composite in comparison to available products on the marker like Short Carbon Fiber Polyamide filaments. The low velocity performances of the Continuous Carbon Fiber Thermoplastic Polymer samples have been promising compared to conventional Short Carbon Fiber Polyamide samples. The advantages of using an Fused Deposition Modelling machine to manufacture composites is the ease to choose between numerous fiber orientations, which a significantly important feature for impact applications. In addition a potential case study for aerospace structure applications of our Carbon Fiber Reinforced Thermoplastic Polymer will be investigated and discussed. The novelty behind this is research is in the coding sequence allowing the fiber cutting system to trigger a the a specific moment in order to integrate the necessary amount of fiber according to the distance of the hotend travelled on the heat bed. Another novelty is in the unique servo actuated fiber cutting system using a specific cutting mechanism. The contribution to the knowledge is the study of the behaviour of a thermoplastic composite under low velocity impact. To investigate the effect of process parameters on a thermoplastic composite. To develop a novel cutting system and code control. Vibration cancellation method for even and continuous integration of continuous carbon fiber cutting method for precise carbon fiber cutting and integration to thermoplastic via Bowden extrusion system. Coding for the motherboard firmware as well as G code for the slicer have been optimised in order to produce quality samples. The effect of hardware on process parameters have been investigated though tensile tests. Low velocity impact performance of continuous carbon fiber polyamide has been also investigated and tested.