PhD, EngD, MPhil and MSc by research theses (SIMS)

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Open Access
Multilayer TiB2/X hard coatings by sputtering deposition
(1998-10) Da Silva, Maria de Fatima Oliveira Vales; Hancock, P.; Nicholls, J. R.
Titanium diboride has been investigated as a potential candidate for aerospace structures, cutting tools, surface coatings of first-wall components and diffusion barriers in integrated circuit metallization. Titanium diboride is a very stable hard refractory compound but its brittleness is the main drawback. It was possible to lessen the TiB2 brittleness by producing TiB2/X coating designs by the multi-target RF magnetron sputtering process. X is the metal layer (Al, Ti, NiCr, Mo) in the composite system. The influence of the composition wavelength and volume fraction of ceramic has been studied over a range of sputtering conditions. The most suitable multilayer coating design (TiB2/NiCr) on steel substrate, for maximum hardness (18.81GPa) and elastic modulus (304.6GPa) was found to be with a composition wavelength of 50nm and volume fraction of ceramic of 75%. The greatest improvement of the elastic modulus measured by nanoindentation was found to be for a TiB2/Al two-layer coating design either on steel or on aluminium substrate, giving 36.2% and 40% improvement above the rule of mixtures respectively, when compared with TiB2 coatings deposited under the same sputtering conditions. Several pieces of three-point bent apparatus were designed for measuring the inplane elastic modulus of the coatings. The three-point bent test by nanoindenter shows promise as a method for measuring the in-plane elastic modulus on uncoated beams. A comparison between traditional and non-traditional methods of measuring mechanical properties of the coatings was performed in this study. The nanoindentation technique was found to be an appropriate method to measure the mechanical properties of multilayer coating designs.
Open Access
Process mapping for BPR at Torbay hospital
(2001-09) Wickes, Martin J.; Sehdev, K.
This report documents a process mapping exercise conducted at Torbay Hospital and subsequent process improvement exercise, forming the initial stage of a Business Process Re-engineering programme. The report reviews pertinent research, concluding that whilst BPR exercises continue to be a popular method of facilitating efficiency gains, few hospitals seem to report the success of their programme or methodologies. As such, every hospital starts the programme from square one. The report therefore documents the methodology employed for data collection, as well as the options for representing the data, once collected; IDEF 3 is recommended as the most appropriate means. The thesis then discusses the tactics involved in running a BPR exercise in the Endoscopy Unit of Torbay Hospital and details subsequent recommendations for improvement.
Open Access
Evaluation of the potential for struvite and calcite formation at seven sewage treatment works within the Severn Trent region
(2000-09) Wall, F.; Parsons, Simon
Scale formation on the pipes, pumps and dewatering equipment succeeding anaerobic digesters leads to reduced hydraulic capacity and increased downtime and pumping costs. The increasing use of biological nutrient removal (BNR), in particular biological phosphorus removal (BPR) leads to the production of phosphorus rich sludges. Anaerobic digestion solubilises ammonia, magnesium and orthophosphates (stored with micro-organisms) which are then available for scale formation. Scale formation in pipes means either replacement or repeated scouring, the expense and inconvenience involved with such measures demand research into the extent of the problem within the Severn Trent region. During this extensive study of seven full-scale sewage treatment works (STWs) throughout the Severn Trent region, the levels of scale forming elements within digested sludge liquors and centrate were monitored. Sampling took place on a weekly basis over a period of six weeks. A computer model was used to evaluate the struvite or calcite formation potential of the liquors and centrate. The model is affected by concentrations of the key elements phosphorus, calcium, magnesium and ammonia, in addition to pH, total dissolved solids and alkalinity. A strong correlation has been found between the models predictions and reality. Four out of the seven works were predicted to have a scale problem by the model, and by the end of the project, this was indeed the case. The type of scale forming was also correctly predicted, though the degree of scale formation was not always as predicted. Bench-scale experiments with real sludge liquors are planned to validate the precipitation potentials indicated by the model. This will allow Severn Trent to take a more proactive approach to the growing scale problem.
Open Access
Simply lean simulations: bridging dynamic discrete-event simulation and Lean Six-Sigma process improvement techniques
(2005-09-07) Vlachogiannis, Eugene; Tjahjono, Benny
Techniques part of the Lean manufacturing philosophy have been widely adopted as a method of improving flow, while at the same time reducing waste within most type of business processes. The financially driven approach of the Six Sigma has not always combined easily with the flow-based principles within lean manufacturing philosophy, but the combination of these two techniques has been proven in the past to be possible with the evolution of the Lean Six Sigma philosophy. That approach can actually improve value to the customer as well as reduce the variation and waste within the critical processes of an organisation in order to deliver real financial benefits to the supply chain. In the past lean practitioners have been wary to whatever had to do with the computer based simulations both due to the time that is needed to be spent in finalising the current and the future state maps and also due to the fact that lean practitioners seem to favour a more hands-on communication with the process itself, rather than a remote analysis like the simulation. Recognition of the “static” drag and drop value stream mapping software, gives an indication that lean practitioners are beginning to accept more the computer-based solutions in order to support collaboration and communication of value stream mapping. BRM3 Ltd, the sponsoring company for this project, have developed a discovery learning simulation exercise called "Simply Lean", which is designed to take its participants from a basic to a full understanding of how to apply the most complex techniques which underpin Lean Six Sigma. The purpose of the project is to investigate the extent to which a library of Lean Templates can be built in Simprocess, so that the enhancement of the learning experience as well as to demonstrate the validity of the simulation as a lean process improvement tool. The investigation in this project is covering the following tasks; Firstly, the successful build of simulation models in Simprocess for each of the two key stages of the simulation exercise. The first model will replicate the Push processing technique used by many small companies the second a Mixed Pull system. Both the models were built with more successful to be the Push model, and the Mixed Pull to be partially incomplete. Secondly, the creation of a “Template Library” consisting of drag and drop V.S.M Icons in Simprocess, in order that simulations models can mimic the accepted appearance of a value stream maps. This was done in full very successfully and in conjunction with the previously mentioned simulation models, the third and last objective was achieved which is the evaluation of the effectiveness of Simprocess within a “Simply Lean” workshop, which was proved as successful since both the models are able to be used as training tools as well as an implementation aid within lean six sigma projects.
Open Access
Integrated solutions as a new perspective for eco-efficient services - a cross-industry exploration
(2003-02) Van Der Zwan, F. M.; Bhamra, T.
Over the past forty years many methods have been developed to reduce the environmental impacts of lifestyles of the Western world. A concept that has emerged in academic and policy making circles is that of ‘eco-efficient services’. This concept is still in the process of being developed and as yet has not successfully been taken up by industry. The research project upon which this thesis reports was initiated to address these concerns. In order to contribute to the research on eco-efficient services, gaining knowledge of a different but successful business concept was considered constructive. The main focus of this research was a novel concept that has parallels with eco-efficient services — namely ‘integrated solutions’. The central research question was how knowledge of this concept could support the development of eco-efficient services or solutions. The overall aim of this research was to provide those that wish to promote the development of eco-efficient services and solutions, with an understanding of a useful business design framework and an understanding of factors that might lead to increased eco-efficiency of these offerings. To this end, two stages of research were initiated and completed. The first stage was the Pilot Study in which a more detailed understanding of the concept of integrated solutions was sought. During this stage, data was elicited from a variety of sources so as to provide a robust foundation of knowledge upon which subsequent inquiry could be initiated. On the basis of the findings from a review of substantive literatures on integrated solutions and the findings of the Pilot Study, a framework and a model were developed. The integrated solutions framework describes the features of an integrated solution and the eco-efficient solutions model shows the elements that can influence the eco-efficiency of a solution. In the second stage, both the framework and the model were validated. These findings were then analysed and incorporated in the initial framework and model, which resulted in a refined eco-efficient solutions model. This research explored how knowledge of the concept of integrated solutions can support the development of eco-efficient services and solutions in a business-to-business context. Nine distinctive features of an integrated solution were identified and described in the refined integrated solutions framework. Furthermore, nine elements that might influence the eco-efficiency of a service or solution have been identified and described in the refined eco-efficient solutions model. Environmental legislation will play an important part in operationalising the model. A number of companies that took part in the research project were interested in taking these ideas forward. The intention of this work was not to refute current trajectories of research in the eco-efficient services domain, but rather to provide an additional body of knowledge that can allow those authors in the eco-efficient sendees domain, to realise the opportunity that the eco-efficient services concept provides to significantly improve resource efficiencies.
Open Access
Safety factors and risk in fatigue substantiation of helicopter components
(2005-01) Toulas, N.; Irving, Phil E.
Helicopter dynamic components are substantiated against fatigue using the safe life methodology. The advance of usage monitoring systems suggest the extension of the safe life according to measured usage, leading to maintenance credits. The question is whether the extended life is associated with a different probability of failure due to elevation of safety factors embedded within the safe life methodology. The fatigue substantiation process was studied and its conservatisms were identified. Both S-N curve behaviour and service loading have been investigated. Three components were studied. One was a location on the lift frame, the others were a main rotor blade linkage and a rotor pitch change link. The variation in manoeuvre loads and usage during normal operation of a UK military helicopter was statistically estimated. Service loads were measured using strain gauged components and a data recording system. Usage was monitored by manual identification and recording of manoeuvres throughout the helicopter flight. It was found that usage variability is very great, with coefficients of variation in excess o f 100% for the majority of manoeuvres. It was found that usage measured in service was significantly more benign for all types of mission, than that assumed in design. Mechanical test results showed significant errors in damage accumulation and mean stress models for life prediction. Monte Carlo simulations demonstrate that calculated probability of failure is dominated by material and modelling errors; usage and manoeuvre load variability playing a minor role.
Open Access
A development methodology for industrial hypermedia task support systems
(2003-04) Tjahjono, Benny Eko; Greenough, Richard
Workers in today’s manufacturing environments have to cope with a greater variety of complex and rapidly changing tasks than ever before. To ensure consistent high quality of products and manufacturing processes, workers require constantly available source of information that serves as a task support and an aide-memoire for settings and task procedures. Hypermedia technology has been proven suitable for this purpose. However, developing industrial hypermedia task support systems (TSS) is different to developing conventional, non-industrial hypermedia applications. This research, therefore, aims to formulate the development methodology that can be used as a guidance to develop industrial hypermedia task support systems. The development methodology, incorporating formal design methods and design heuristics, has been used to develop a number of industrial hypermedia TSS. Both the hypermedia TSS and the methodology have been evaluated through a series of case studies. The thesis confirms that the success of the hypermedia task support systems is not only dependent on the usability of the system, but also on the quality of the content. Difficult and time consuming updating processes will cause poor accuracy and currency of the content, resulting in the users not being able to get the benefits from using it. The collaborative authoring environment that exists within the development methodology enables the content of the hypermedia task support system to be easily created and maintained, so as to ensure its usability. Compared to existing methodologies, the proposed methodology is more comprehensive and more suitable for developing industrial hypermedia systems. In addition to the formal approach typically found in ‘off-the-shelf methodologies, the methodology formulated in this research incorporates design heuristics that aim to improve an application’s coherence and to reduce users’ cognitive overhead, two important requirements for designing the user interface of industrial hypermedia systems.
Open Access
Evolutionary computing techniques for handling variable interaction in engineering design optimisation
(2001-11) Tiwari, Ashutosh; Roy, Rajkumar; Jared, Graham
The ever-increasing market demands to produce better products, with reduced costs and lead times, has prompted the industry to look for rigorous ways of optimising its designs. However, the lack of flexibility and adequacy of existing optimisation techniques in dealing with the challenges of engineering design optimisation, has prevented the industry from using optimisation algorithms. The aim of this research is to explore the field of evolutionary computation for developing techniques that are capable of dealing with three features of engineering design optimisation problems: multiple objectives, constraints and variable interaction. An industry survey grounds the research within the industrial context. A literature survey of EC techniques for handling multiple objectives, constraints and variable interaction highlights a lack of techniques to handle variable interaction. This research, therefore, focuses on the development of techniques for handling variable interaction in the presence of multiple objectives and constraints. It attempts to fill this gap in research by formally defining and classifying variable interaction as inseparable function interaction and variable dependence. The research then proposes two new algorithms, GRGA and GAVD, that are respectively capable of handling these types of variable interaction. Since it is difficult to find a variety of real-life cases with required complexities, this research develops two test beds (RETB and RETB-II) that have the required features (multiple objectives, constraints and variable interaction), and enable controlled testing of optimisation algorithms. The performance of GRGA and GAVD is analysed and compared to the current state-of-the-art optimisation algorithm (NSGAII) using RETB, RETB-II and other ‘popular’ test problems. Finally, a set of real-life optimisation problems from literature are analysed from the point of variable interaction. The performance of GRGA and GAVD is finally validated using three appropriately chosen problems from this set. In this way, this research proposes a fully tested and validated methodology for dealing with engineering design optimisation problems with variable interaction.
Open Access
Smart characterisation of damage in carbon fibre reinforced composites under static and fatigue loading conditions by means of electrical resistivity measurements
(1996-02) Thiagarajan, C.; Irving, Phil E.
This thesis investigates the smart damage sensing capabilities of the electrical resistivity measurement technique in carbon fibre reinforced composite materials. The static and fatigue damage mechanisms of unidirectional and cross-ply laminates are reviewed. The electrical resistivity measurement investigations of carbon fibre, epoxy resin and carbon fibre reinforced composites are described. Theoretical models related to damage and electrical conduction modelling are reviewed. The material properties, laminate fabrication, specimen design, tab design and electrode design details are presented. The experimental test set-up and test programme details are presented. The details of the formulation and algorithms of a proposed new random resistor network model and the three-dimensional unit cell assemblage model are described. The results related to the applicability and the validation of these models are presented. The influence of electrode effects on the electrical resistance are investigated. The relevant results are presented. The electrical properties of carbon fibre reinforced composites independent of specimen geometry and electrode configuration are established. The dependence of electrical resistance on the specimen geometry was investigated and the relevant results are presented. The smart damage sensing capabilities are demonstrated using computational simulation studies using the proposed new three-dimensional model. The strain sensing and damage sensing capabilities of electrical resistivity measurement technique under static and fatigue loading conditions are presented. The dependence of electrical resistance to the applied stress and fatigue life of the samples subjected to fatigue loading is presented. The smart sensing capabilities are highlighted based on the experimental and theoretical results. The static and fatigue behaviour of epoxy 914 and epoxy 920 based CFRP laminates is investigated. The failure mechanisms are established using the electrical resistance and other non-destructive test methods.
Open Access
Development of an objective evaluation framework with subjective impact
(1999-09) Taylor, J. P.; Roy, Rajkumar
Multimedia technologies are finding new and advanced uses within the modern organisation. From a strategic perspective, these organisations realise techhology contributes to enhance productivity and operational success. However, to embrace technology without recourse to those who ultimately utilise such facilities, could effectively jeopardize the up-take of new improved working practices. Sir Paul Condon: Commissioner of Police for the Metropolis has been noted within MetView (1999) for the following statements: • “Technology is playing an ever increasing role in modern policing methods and has been responsible for many of our current successes” • "Good and innovative policing, and good and innovative technology cannot be separated”. To continue this success there is a need within a modern policing organisation to develop an objective framework for evaluating multimedia technologies. This framework will give recognition to subjective user issues that are necessary to contribute towards the partnership that exists between innovative policing and innovative technology. This research presents a framework that achieves specific business requirements outlined by a technology aware department within a police organisation. Three research objectives were completed. These objectives are: - Provide a business process for evaluating multimedia technologies in a way that is repeatable and unbiased - Provide a sound foundation that accounts for the typical user of multimedia technologies - Aid towards increased user satisfaction and confidence. Conclusions detail the objective evaluation framework with subjective impact, reference to a business process and considerations for a modern policing organisation on a way forward
Open Access
Jig-less assembly for aerospace manufacture
(2000) Snelling, Peter D.; Corbett, John
Due to the high level of investment required to compete successively in the global aerospace and automotive markets, these industries are forced to form partnerships wherever possible and thereby share their resources appropriately. This in turn has brought about the requirement to provide a standardized flexible design and manufacturing capability in which interchangability and compatibility may take place. Current assembly practices and associated tooling can be traced back to the earliest days of aircraft production and have become relatively expensive and inflexible in today’s environment. The final assembly stage has been recognized to be a key area which has the potential to offer substantial returns as well as play a major role in any change management process within the organisation. Assembly tooling, jigs and fixtures, are required to support and maintain positional accuracy of components during assembly. Traditional jigs and fixtures make up for the short comings at the product design and manufacturing phases and add significantly to the final product costs and reduce flexibility in the production process. Jig-Less Assembly Concept (JAC) has been defined and researched with the aim to integrate and optimize various tools and techniques with which to reduce or eliminate the assembly tooling currently in use. The outcome of the research presents a comprehensive critique of the processes involved in and pertaining to the assembly of typical airframe assemblies. The thesis forms a platform from which to move forward towards the embodiment of the concept of jig-less assembly. Particular attention is drawn from the research to the need for appropriate organisational and management strategies as well as technical innovation in the adoption of a jig-less approach to airframe assembly. Together with BAe Airbus and Military this collaborative research seeks to define the scope of JAC by identifying and evaluating the issues and constraints, to enable the development of supportive techniques in unison with best practice engineering within a robust and sustainable manufacturing system. This commercially focused R & D required liaison and working at all levels within a variety of industrial sites using live case studies at Filton and Chester.
Open Access
Review and improve the manufacturing engineering new product introduction process -AIRBUS UK
(2005-09-07) Shaw, Stephen; Vitanov, Valentin
This research has developed an organisational improvement methodology for the Manufacturing Engineering (ME) New Product Introduction (NPI) process at Airbus UK. The methodology is focused on improving the management of Concurrent Engineering (CE) and team/stakeholder effectiveness through improved involvement, communication, and coordination. In the context of Airbus UK’s ME NPI process the objectives were: to examine the current process, including the monitors and controls, deployed by the ME development team to design, implement and support NPI; to map/model the ME NPI process and hence, conduct a comparative analysis with best industrial practice; and to evaluate the pragmatic options open to ME and recommend appropriate business improvements/solutions. The research showed that effective CE teams provide the main vehicle for improving product development performance, by increasing integration through improved involvement, communication, and coordination. A literature study of ‘best practices’ identified the major causes of ‘waste’ within NPI as, poor communication and poor programme management. The research also showed that process modelling not only achieves a better understanding of the processes but also serves as a tool to contribute towards the assessment of CE teams using process based analysis. It was also found that process modelling improves process management within NPI. Process modelling and analysis is applied to the ME NPI process in order that a structured and pragmatic improvement methodology can be developed. The presentation of the CE organisational improvement methodology developed by this research provides Airbus UK with a less prescriptive approach to improving their business within the ME function and area of NPI. The application of the methodology is, unfortunately, outside the time limitations of this research. However, it is widely purported by ME NPI process stakeholders, and literature, that the most significant improvements to the current process can be realised through the improvement of ‘softer’ organisational issues.
Open Access
ERP system upgrade: an analysis of the costs, benefits and requirements
(2002-09) Shaw, C.; Greenough, Richard
This project looks at the feasibility of the high performance vehicle manufacturer, Ray Mallock Limited (RML), upgrading their current version of their Frontstep produced Enterprise Resource Planning (ERP) system from version 4 to the latest version 6. The project outlines a cost benefit analysis of the upgrade so RML can see the value of the new features of the system and weigh these up with the costs that would be incurred. The project then goes on to look at the risks that RML would face if they chose to upgrade or not to upgrade the ERP system and the timescales of the upgrade process. Finally, some suggestions are made to ensure that RML can take full advantage of their current system while being in a position to upgrade effectively in the future. After considerable analysis, this report suggests that an upgrade at this point in time for RML is not a viable option due to the high cost and high risk of the project. In addition, this project suggests that that an ERP system needs management and development on an ongoing basis to ensure that a company is in a strong position to take advantage of new versions without having to incur high risks and even higher costs. The ongoing costs of an ERP system are significant and often misjudged by many companies during the implementation phase, especially if they want to stay on the support contracts as they become tied to an upgrade path dictated by the supplier. Companies must also ensure that they are in a position to take advantage of the upgrades and do not lose skills within the business to manage a change of this nature and they have the business and IT infrastructure in place to support the upgrade.
Open Access
The effect of ultrasonic sludge pre-treatment on anaerobic digestion
(1998-09-11) Scott, Joanna Ruth; Quarmby, Joanne
As sewage sludge dumping at sea is banned from 31st December 1998, water companies are having to find alternative outlets for large volumes of sludge. This project looks at a method of improving the conventional sludge treatment process of anaerobic sludge digestion, by pre-treating sludge with ultrasound. Ultrasound produces cavitation, which breaks up sludge solids, making it easier for bacteria to utilise them. In theory, this leads to a greater reduction in volatile solids and an increase in the volume of methane produced. Sludge was thickened in a drum thickener and passed through a Nearfield Acoustical Processor (NAP-3606-HP-TC) ultrasound generator. Two different intensities were used, 5 amps and 16 amps. Sludge was then placed into the respective holding tanks of three 100 litre (1) capacity pilot scale digesters. Sludge treated at 5 amps was supplied to the first digester, sludge treated at 16 amps was supplied to the second digester, and the third digester received unsonicated sludge. Batch digestion tests, soluble chemical oxygen demand (sCOD) tests and capillary suction time (CST) tests were also carried out. No major differences in gas production or volatile solids reduction were found between the three pilot scale digesters, possibly because the effects of sonication were negated during the sludge storage stage, due to shearing by the mixing device. However, the batch tests, soluble COD tests and CST tests carried out all showed that sonication had a marked effect. The CST tests showed that sonication made sludge harder to dewater, before and after subsequent digestion. Future work should include a more detailed investigation into the effects of sonication on sludge dewaterability. This is because a pre-treatment process that produces a sludge that cannot be dewatered may not be economically viable, despite any advantages of the pre-treatment process.
Open Access
The development of a sustainability tool
(2005-09) Sasaki, S; Dewberry, Emma
This study examines the potential for ICI Paints, a paint and coating manufacturer, to move their products towards greater sustainability. A brief review of the tools and techniques currently in use to encourage sustainable outputs is given. A new tool is proposed and developed that combines the principles from The Natural Step (TNS) and the streamlined life-cycle analysis concept. Using a matrix to contain TNS’s four system conditions, which measure sustainability in four scientific principles, against five lifecycle stages, a ‘snapshot’ of the sustainability profile of paint can be efficiently determined. Study methods included semi-structured interviews with ICI Paints employees representing different stages of the paint life-cycle. Significantly, despite being a leader in paint innovation and a Dow Jones Sustainability member, ICI Paints had performed very little life-cycle work in the past few decades. The development ofthe snapshot tool was made up ofthree areas: setting the context by understanding ICI Paints sustainability needs; meeting the sustainability needs through the development ofthe snapshot tool; finding where and how the snapshot tool could be useful to ICI Paints. By extracting common themes from interviews and secondary data, the main finding which over-arched all three objectives was the tool’s potential in communicating sustainable messages to generalist and specialist audiences. Other themes included the usefulness of the tool in sustainability focused risk management strategies. Future work includes reviewing and testing the snapshot tool in workshops.
Open Access
Modified bismuth titanate piezoelectric ceramics
(2003-12) Sanson, Alessandra; Whatmore, Roger W.
Bismuth compounds are considered the most suitable alternatives to lead-based systems for ferroelectric and piezoelectric applications. Nevertheless little has been done to systematically study the relationships that link the two main classes of ferroelectric bismuth compounds: perovskite and bismuth layer compounds (Aurivillius compounds). The knowledge of these relationships could be a key to improve the performances of the bismuth compounds and could help to better tailor their properties for specific applications. The objective of this project was twofold: 1. To understand the structural and electrical relationships between perovskite and Aurivillius compounds within the Na^Bi^TiO^-Bi^Ti^O^-BaTiCb (NBT-BIT-BT) system; 2. To explore the possibility of obtaining a new perovskite of formula Bi2MgTiOô. A study of 83 different compositions allowed us to sketch the possible phase diagram of the NBT-BIT-BT system. XRD structural characterisation highlighted the importance of low angle analysis in the study of layered compounds. The presence of monophasic regions in the phase diagram stressed the flexibility of this class of compounds that are able to withstand high percentage of vacancies before collapsing. It was shown that, after taking into account some electronic considerations, a simple geometrical model can be use as “rule of thumb” to predict the stability of Aurivillius compounds. New unreported compounds were found in the system and a mechanism for the formation of the Aurivillius compounds is proposed. The dielectric and piezoelectric properties were linked to the fundamental layered structure of the Aurivillius phases showing that all these properties depend on the number of perovskite blocks present. The higher the number of perovskite blocks, higher the values of resistivity and relative permittivity.
Open Access
Scale control in heat exchangers
(1998-09) Sanchez, G. E.; Judd, Simon J.; Parsons, Simon
Whenever natural water is used in a heat-exchanger, scale deposits tend to build up on heat transfer surfaces. This results mainly from the chemistry associated with the hardness and alkalinity of natural water. To ameliorate the problems created by scale deposition, a wide range of methods and processes are available. This thesis investigates the efficiency of one of these methods, magnetic treatment. Two pilots plants were used to measure the effect of a magnetic field created by a commercial non-intrusive clamp-on device on scale formation. The first pilot plant consisted of four domestic boilers, two treated and two controls, filled and operated four times daily with mains water dosed to specific hardness and alkalinity levels. This rig operated in single-pass mode, with the water contained in the boilers being flushed out after each heating cycle. The second rig was based on two loops, treated and control, filled with deionised water to which reagents were added to control hardness and alkalinity levels. Each loop consisted of a 75 litre tank feeding a scaling cell via a centrifugal pump. The scaling cells included a copper element, exposed on one side to a regulated flow of heating water (set temperature) and on the other side to the flow of scaling water. The boiler rig results showed no significant influence of magnetic treatment on the scaling of the boilers’ heating elements. On the recirculating rig, no significant effect of the magnetic devices on the amount of scale formed was observed. However, magnetic treatment appeared to have reduced by 50 % the thickness of the hard scale layer on the copper elements. The reproducibility of the experiments was significantly improved by precoating the copper element with a scale layer to overcome discrepancies introduced by the induction process.
Open Access
Low mass platinum aluminide bondcoat for thermal barrier coating
(2001) Saint-Ramond, Bertrand; Nicholls, J. R.
During the last 30 years, Thermal Barrier Coating systems (TBCs) have been extensively used to protect the hottest part of aero-engines. They can extend significantly the lifetime of high pressure turbine blades and combustor walls by decreasing the superalloy substrate temperature by up to several hundreds o f degree C. TBCs are duplex systems consisting of a thermal insulative ceramic toplayer and an intermediate metallic bondcoat layer, whose function is to protect the substrate against corrosion and oxidation and to promote the ceramic adherence by forming an alumina scale at the interface with the ceramic. The lifetime of the TBCs is however limited by chemical, mechanical and thermal stresses in the coatings due to bondcoat oxidation and the mismatch of thermal expansion coefficient (CTE) between the ceramic, the bondcoat and the substrate. The bondcoat consideration is therefore of a substantial importance for the TBCs lifetime extension, and the present work has been focused on the development of a novel and innovative intermetallic overlay bondcoat, having a much thinner thickness than conventional bondcoats, acting as a diffusion barrier for substrate harmful elements, and promoting the formation of a pure, slow-growing and adherent alumina scale. The low-mass bondcoat system has been based on a 3-15 microns thick PtAh intermetallic layer, with the ternary addition of a reactive element (Hafnium, Zirconium, or Yttrium). Aluminium and Platinum are deposited sequentially by the sputtering process (Physical Vapor Deposition). The bondcoat is thus a multi-layer coating, and the layers react one with another exothermically by diffusion after a subsequent heat treatment at a relatively low temperature. The temperature of reaction between the layers and the stability of the obtained intermetallics has been studied by using Differential Thermal Analysis. Different platinum aluminides have been developed as bondcoats and the number of layer has been varied (up to 350 layers) in order to study the influence on the coating structure. Finally, the most successful systems have been cyclically tested to be compared to industrial bondcoats systems. These experimentations have led to the development of a highly controllable bondcoat deposition and formation process. Different morphologies and compositions can be accurately obtained by varying the individual layer thickness and Al/Pt thickness ratio within the coatings. A reactive element, which consists of either zirconium, yttrium or hafnium has been introduced into the aluminium layer by sputtering co-deposition and it has been therefore demonstrated the possibility of improving the efficiency of the low-mass bondcoat by adding such an element evenly through the coating. Whatever the composition or its structure, the low-mass bondcoat is adherent to the substrate and does not interact with the substrate during the deposition and the formation process. The bondcoat is thermally stable for a significant time of aging at 700°C, 900°C and 1100°C, but do not withstand cyclic oxidation testing better than industrial bondcoats. Nevertheless, to really assessed the potential of the low mass bondcoat, a cyclic oxidation test has to be performed after ceramic topcoat deposition, which would modify the local stress gradients on the thermally grown oxide, during cooling.
Open Access
Product complexity assessment for a Proactive-DFA implementation (Simplicity + Simplicity = Complexity)
(2004-10) Rodriguez-Toro, Carlos A.; Jared, Graham
This thesis presents product complexity as a criterion for the optimisation of product design in the light of an Assembly-Oriented Design and Design for Assembly implementation. It takes a holistic approach to the evaluation of the product architecture by presenting a set of indicators that help examine the product structure at two different levels: Assembly and Component complexity. Assembly complexity assessment is further sub-divided into Structural and Sequence complexity. The latter is a well-known and thoroughly studied area in assembly sequence evaluation, whereas the former gives a novel and original approach to drawing attention to those areas in the product configuration that will consume more resources (i.e. time and tooling required). Component complexity, on the other hand, is sub-divided into manufacturing and process handling/manipulation complexity. The first area has been addressed by the manufacturing analysis section of most Design for Assembly and Manufacturing methodologies, but it has been traditionally addressed as a manual and chart-based evaluation. This is a rigid approach that leaves little room for expansion and has no connection with the product structure. The metrics presented in this work embody a new approach that takes into account the component-to-component interactions and allows the analysis of component shape by extracting its geometry characteristics and comparing them with particular traits of the manufacturing processes available to the designer. Additionally, the metrics presented in this work can be used to make an assessment of the product complexity at a particular point (static complexity) in the development cycle. They can also be registered over a period of time to provide an estimate of the possible consequences of the decisions made during a part of the development cycle (dynamic complexity). By using the methods developed, designers could reduce production costs and increase the reliability of their products.
Open Access
Improvements in the materials supply chain for a motor sport supplier using quality management techniques.
(2000-09-08) Robinson, Frances Margaret; Rogerson, J. H.; Nixon, J. H.
Ray Mallock Ltd is a medium sized business operating in one of the fastest developing, expensive, international industries, motor sport. A tremendous amount is spent every year on research and developing cars to go faster because the company’s reputation stands upon their cars winning. Motor sport is primarily located in the south of England with many small specialist suppliers developing around the various teams. The suppliers to the motor sport industry are often under considerable pressure to respond instantaneously to the needs of each team. With such a wide range of skills and types of suppliers the supply chain becomes very complex and awkward for a company the size of RML to manage as it requires a lot of resources. Therefore the overall project aim was to look at the approach RML took toward their supply chain and resolve the major problems that were encountered by the Materials Department. The Materials Department consists of Purchasing, Inspection and Stores. These departments are closely linked and incorporate quality. A number of quality tools were used to gather data and information regarding the department including interviews, , ) internal literature review, observation, flow process mapping, gap analysis and data [ collection. This highlighted a common problem to medium sized companies, informality. i Procedures were not in place so improvements were limited, a wealth of experience lay with employees regarding suppliers but this needed to be gathered and methods for ; \ selecting, appraising and measuring performance formulated. Communication externally needed improvement, with the high variability and randomness of orders placed with suppliers they needed to be made more aware of how projects are progressing to help them plan. There is extra emphasis placed upon critical components for car builds which is the reason why a supplier development scheme was adapted for use by RML. The project concludes that proper procedures, supplier appraisal and selection schemes, performance measurement and future supplier development, if used properly and wholeheartedly the tools ought to aid the department. The Materials Department can improve after the initial implementation by developing the tools and make real steps towards making better informed decisions about suppliers, managing supplier relationships, continuous improvements and contributing to the bottom line of RML.