PhD, EngD, MPhil and MSc by research theses (SIMS)
Permanent URI for this collection
Browse
Browsing PhD, EngD, MPhil and MSc by research theses (SIMS) by Course name "MPhil"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Open Access Blends of epoxy resin with polycarbonate and CTBN rubber(1991-03) Jayle, L.; Partridge, Ivana K.The study described in this thesis examines how the toughenability of a difunctional epoxy resin cured with a diamine hardener is affected by the presence of a dissolved polycarbonate in the epoxy matrix, when that matrix is modified by CTBN rubber particles. The compatibility between the epoxy resin and four different polycarbonate types is investigated. Influence of polycarbonate content and of the type of polycarbonate upon the mechanical properties and morphology of polycarbonate or rubber-polycarbonate modified epoxy systems is considered. Toughenability of the epoxy matrix is found not to be improved by the presence of dissolved polycarbonate. Study of chemical interactions between polycarbonate and epoxy resin and polycarbonate and hardener shows a degradation of the polycarbonate by the epoxy resin and also by the diamine hardener. Failure of the polycarbonate to increase the toughenability of the epoxy matrix is considered to be related to this degradation. Toughness properties of polyethersulfone modified epoxy systems are also considered.Item Open Access Combined coagulation and membrane microfiltration for removal of natural organic material (nom)(1999-03) Hillis, Peter; Judd, Simon J.The removal of natural organic matter (NOM) is a key requirement of many processes in potable water treatment. Conventionally, removal of NOM and colloidal material has been achieved by coagulation with inorganic coagulants followed by either direct rapid gravity filtration alone or clarification (sedimentation or flotation) followed by at least one stage of rapid gravity filtration. An alternative to conventional processes is to combine membrane microfiltration (MF) with coagulation for NOM removal. The advantages of MF technology over traditional sand filters is the maintenance of an absolute barrier throughout the filtration process, thereby enhancing the physical separation process by presenting an absolute barrier to suspended materials. This thesis presents the results from such a system. A 9.6m2 hollow fibre hydrophilic polysulphone MF membrane system was used in combination with ferric sulphate under controlled pH conditions. The system was operated under constant flow condition and the coagulant concentration varied to assess performance. Coagulation conditions which promoted rapid aggregation of particles was found to give best performance with respect to pressure development, this coincided with a zeta potential at or near zero. Also, a pre-flocculation time of 20 seconds was found to be sufficient to allow complete removal of material associated with the coagulation process. Comparison with other workers showed similar results for the specific cake resistance despite considerable differences in both the scale and type of system used.Item Open Access Development of a joint TQM&IlT implementation model(1997-02) Georgousis, Ioannis D.; Kay, John M.This study investigates the impact of the joint TQM and JIT approach on the performance of manufacturing organisations. The final objective is the development of a Joint TQM&JIT Implementation Model, based on the results of the investigation. The Model will contain a series of activities and operations that will lead to process and product improvement, based on the principles of the joint implementation approach. Many studies and researches have been conducted in order to investigate and clarify the details and the potential benefits of each system. However, few studies looked at the operations that are necessary for a successful joint TQM and JIT approach; and even if they did it, they did not analyse the manufacturing process systematically. The present study attempts to give an answer to this problem and, moreover, to produce a systematic, analytical, and clear implementation plan. The literature review and the industrial survey showed that there is a very close link between TQM and JIT; what is missing is a detailed implementation plan. The TQM&JIT Model tries to satisfy the musts and the wants of every manufacturing organisation which wishes to be competitive and world-class in the contemporary demanding markets, using the quality of the products and the low manufacturing cost as weapons. Furthermore, the Model details the sequence of the activities that should be followed in order to get completely beneficial results. It determines the production areas that should be improved, but also determines the role of everyone within the company towards that objective. The flowchart that presents the network of the activities is very simple and very clear, and this is perhaps the major advantage of the Joint TQM&JIT Implementation Model. A series of performance measures for each step of the Model has also been developed, in order to ensure the completion of each implementation stage.Item Open Access An investigation of genetic algorithms and genetic programming(1996-06) Kolcu, Ibrahim; Vella, A. D.There are many regression techniques that try and fit known models to sets of data. For them we assume the functional form of the model and use analytic or statistical techniques to find the values of any unknown model parameters. If the target model is thought to be of sufficiently complex a form, the above techniques (i.e. analytic and statistical techniques) may fail to provide the desired results and alternative methods have to be used. This is even more important if the underlying model is itself unknown. Genetic algorithms and genetic programming are two techniques that may help in the search for suitable models. Unfortunately, however, both of these techniques have themselves parameters that need to be specified and there are no clear guidelines to aid such choice. A number of other implementation issues are also open questions and in this thesis we look at a number of ways of implementing genetic algorithms and genetic programs to evaluate alternatives. Simple target models are used throughout most of this work so that the effects of changes to the method's parameters can be monitored. We look at how population size, crossover probability and mutation rate affect the speed of convergence of the genetic algorithm to an acceptable model. One of the most difficult aspects of genetic programming is the issue of the meaning of the offspring produced by crossover or mutation. Some systems arrange that any offspring that do not have meaning are removed from the population. Others ensure that no such offspring can arise. In this work we look at what might happen if we always impose a meaning on all possible offspring. In the genetic programming part of this work we look at two representations of our models. In the first we used a fixed length representation, whilst in the second we used a tree to represent each member of the population. We also look at a number of fitness functions. The commonest such functions are based upon errors between the model and the data. For our fitness functions we also use their correlation coefficient. We found that a strategy that starts by using correlation coefficient and then a fitness that combines both correlation coefficient and error worked better.Item Open Access Jig-less assembly for aerospace manufacture(2000) Snelling, Peter D.; Corbett, JohnDue 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.Item 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.Item Open Access Mechanical design aspects of a tri-axial accelerometer(2004-06) Hatt, Joseph M.; Kirby, Paul B.This work describes the development of computer models for the design of a novel three-axis silicon accelerometer with thin-film PZT piezo-electric sensing. Theoretical and finite element methods are used to predict the resonant frequencies, resonant mode shapes, and charge sensitivity of the accelerometers. The strengths of each analytical method are used to allow the identification of trends in geometrical affects, and to optimise the design with respect to specification objectives for a commercial device. The theoretical models have been developed and refined in conjunction with practical fabrication trials. This has allowed the material properties to be derived, specific to the thin-film deposition method used, and incorporated onto the models. The practical fabrication process has raised a number of unforeseen issues, and these have led to changes from the original design. These changes have been analysed with the theoretical models, and revised performance predictions produced. The practical findings are consistent with the revised predictions, and achieve close to the desired performance specification.Item Open Access A methodology to computerise QFD’s application and enhance its integrity purpose and acceptance with in the European Automotive Industry(1997-09) Kalargeros, Nick; Gao, J.Companies are increasingly looking up to QFD as a key to capture the customers voice and to encourage team members to communicate more effectively with each other. QFD is a complex and very time consuming process therefore difficult to implement. Owing to the complexity of this technique in the European Automotive Industries, its implementation generally relies upon specialists and consultants. A lack of clear understanding between the industrial participants results in a somewhat disrupted implementation. Moreover individual competitiveness and an increasing need for recognition will prevent them from putting faith in the mechanics of the technique and from reaching a team consensus. Under these circumstances the QFD implementation will not be pure. There is a great deal of QFD work which is available for all those with time to analyze and argue its particular points. But there is an increasing desire in some places i.e. the Automotive industry for practical information and applied knowledge about QFD. Moreover a lot of automotive business like the idea of implementing the technique but they don’t know how. Obviously there are places that people can learn about QFD and there are consultants who can help them implement it. The problem which arises by this approach is the lack of understanding within the business. That means consultants may not understand a company and its needs when implementing QFD but they will propose solutions. More important they have no reason to argue with any of the company’s members therefore they can easily agree for a look alike implementation of the technique. Considering the above statements the purpose of this project is to eliminate any misunderstanding of the technique, by describing the technique in a simple manner recommending its implementation to the product development process using fuzzy logic and a typical spreadsheet PC software. Finally an enhancement in the communication between the members of the product development team and the acceptance of the technique can be achieved representing the team member’s preferences in a fuzzy manner and calculating the group decision using a methodology proposed in this project. Therefore QFD will be available to industry as a user friendly tool which can be applied to vital decision making during the product development stage, ensuring that the end product is a good result, taking the technique from the papers and putting it into practice.Item Open Access Scale control in heat exchangers(1998-09) Sanchez, G. E.; Judd, Simon J.; Parsons, SimonWhenever 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.