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

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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.
Open Access
Objective on line assessment of the performance of flux cored wires by real time computer based monitoring
(1993-04) Chawla, Kawalprit Singh; Norrish, J.
The aim of this research was to devise an innovative technique to obtain an objective assessment of the quality performance of tubular cored wires by sensing and measuring the signals available during welding. The work comprised: Identification of the parameters to assess. A study of the different monitoring techniques. Design of specific quality evaluation methods. The production of a system which allowed a quality index of welding performance to be obtained. Initially, the arc voltage, arc current, wire feed rate, arc light and arc sound signals were identified as possible sources of useful information. After a useful technique was accepted, the non-useful techniques were abandoned and a quality measuring instrument was built. The work involved development of statistical analysis techniques, Fast Fourier Transforms and mathematical modelling. A new approach to process modelling was devised which provided an objective and very flexible method of assessing, comparing and developing welding consumables. The final system was evaluated against conventional subjective assessment techniques and very good correlation was obtained.
Open Access
The coupling mechanisms in the CO2 laser welding of copper
(1994) Gouveia, H. N.; Norrish, J.
The CO2 laser is a potentially powerful tool for welding, allowing high integrity joints to be produced with minimal thermal damage and high joint completion rates. Its use in the joining of reflective, high conductivity materials, such as copper is, however, limited. The current work examined the high power CO2 laser welding of oxygen free high conductivity copper and in particular the coupling mechanisms which appear to control the consistency of the process. The role of the plasma control jet was found to have a fundamental influence on the coupling behaviour. Due to the practical problems of direct observation of the jet gas flow during welding, the process was modelled using a flow simulation package. The results of the simulation enabled a satisfactory theory for the coupling mechanism to be developed. Plasma plume formation and maintenance during the welding process appeared to be responsible for coupling and to occur by a non-conventional mechanism. The theory explains the anomalies in previous work and indicates how the process consistency may be improved.
Open Access
Technology assimilation: understanding the user - IT professional relationship
(1994-09) Hinton, C. Matthew; Cordey-Hayes, M.; Mayon-White, W.
It is argued that a substantial gulf exists between the investment made in technology and the ability of organisations to realise significant improvements in business performance. In the fields of Innovation and Technology Transfer there have been developments in the application of more process focused and human elements as a way of addressing the deficiencies of the previous generation of linear and more structured research. In this thesis the conceptual models from such research have been adapted and modified in order to apply it to the specific problem of the adoption and assimilation of information technology (IT). The conceptual models are operationalised through a set of research activities which include investigation into the congruence between technology deliverers and recipients, the technocratic nature of the IT professional role (as determined by employers), the values and perceptions of IT managers, the preoccupation of the IT research and practitioner literature, and the values and perceptions of IT users, as 'service' clients. The substantive conclusions are that the nature of the role of IT professionals is dominated by relatively project orientated and technology orientated characteristics. This, in part, inhibits the ability of organisations to develop strategy and for organisations to consider the service function of IT. This is displayed in the form of an interactive, conceptual model. The thesis also demonstrates the extent to which the distinction between the adoption of an IT technological opportunity, by an organisation, can be usefully distinguished from the problems of assimilating that opportunity into the daily routine of the organisation and therefore for business advantage.
Open Access
An investigation of hydrogen embrittlement of high strength steel due to zinc/nickel alloy electroplating
(1995-01) Carr, Martin J.; Robinson, M. J.
The work described in this thesis examines the embrittling effect of both cadmium and zinc-nickel electroplating on quenched, tempered and plated and plated and baked tensile specimens of AISI4340 steel. Measurements were taken of ultimate tensile strength, reduction in area to obtain an embrittlement index and Vickers hardness. In this way a direct comparison of the extent of embrittlement for the two alternative processes was made, while at the same time, keeping a quality control check on successive batches of specimens. An examination of the microstructure and fracture surfaces was made. The effect of baking to remove hydrogen dissolved in the electrodeposit and de-embrittle the steel was considered. Being porous to hydrogen, some types of cadmium electrodeposits allow hydrogen gas to exit the substrate during baking. Nickel, however is capable of forming a barrier to hydrogen diffusion and it was found that this could impede the ingress of hydrogen without preventing the degassing of the specimens. Permeation experiments were conducted, using a cell based on a Devanathan and Stachurski permeation cell, to compare and contrast the amount of hydrogen that entered a steel substrate during zinc-nickel alloy electroplating under various conditions. The amounts of hydrogen that permeated the diffusion membrane were then examined in the light of the results of the tensile tests. It was found that a close correlation existed between the amount of hydrogen entering the substrate and the extent of embrittlement. This correlation allowed apparently anomalous embrittlement observations to be explained in terms of the pH of the plating solution. The results suggested a modification to the currently accepted hydroxide suppression mechanism for zinc-nickel alloy deposition was possible. By way of testing predictions made under the modified deposition mechanism, Auger and XPS analyses were used to search for a nickel rich layer predicted to exist adjacent to steel substrate.
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
A mathematical model of DIAJET abrasive water jet cutting
(1996-04) Claffey, E.; Allwood, R. L.
A mathematical model of ductile material cutting with an abrasive suspension jet has been developed. This is based on erosive wear of material by solid particle impact. The largest contribution is assumed to be from near-normal impacts. This 'deformation wear' causes work-hardening and subsequent brittle fracture of the material. A threshold velocity exists, below which no erosion takes place. The value of this velocity is dependent on the material ultimate tensile strength. The depth of cut achievable for a given traverse speed is dependent on the threshold velocity and the fracture strength of the material. For brittle fracture this has a value of E/10. A simulation of particle acceleration within a cutting nozzle was also undertaken by applying the Navier-Stokes equation to the boundary conditions. This revealed that the particle velocity is almost identical to the theoretical (Bernoulli's) slurry velocity for the nozzles used in this project. The model has been validated against a range of operating parameters such as pressure, abrasive, abrasive concentration, and material properties. This has confirmed the validity of the assumptions, with a good correlation. Some predictions, however, gave a better fit if only 60% of the measured abrasive discharge was used. Highly alloyed materials produced a less satisfactory fit to the model.
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.
Open Access
High strain deformation and ultimate failure of HIPS and ABS polymers
(1997) O'Connor, Bernard; Bucknall, Clive
The role of the rubber particle in the ultimate failure of High Impact Polystyrene and Acrylonitrile Butadiene Styrene was investigated by modifying the rubber content and the shear modulus of the rubber phase in the materials. The rubber content in a commercial grade HIPS and a commercial grade ABS, both with 8 wt. % rubber, was varied by blending with general purpose polystyrene and general purpose poly(styrene-aciylonitrile) respectively. The shear modulus of the rubber phase was varied through blending the materials with sulfur or irradiating the materials with gamma irradiation. Dynamical mechanical thermal analysis confirmed that the Tg of the rubber phase increased with increasing sulfur content. It was found that with decreasing rubber content or increasing rubber shear modulus, the yield, flow and breaking stresses and the elastic modulus of the composite increased, while the failure strain decreased. In a similar experiment to Sjoerdsma and Boyens (1994), the statistics of failure of the materials were investigated with respect to rubber content and rubber shear modulus. Batches of specimens numbering not less than 20 were extended under a constant applied stress until failure occurred. A custom designed creep rig was built to carry out several long term creep tests simultaneously. From these tests it was concluded that the probability of failure increased as the stress on the rubber increased and underpinning this, is a novel discussion of the high strain deformation and the mechanism controlling failure in HIPS and ABS. This conclusion was discussed in terms of rubber content and rubber shear modulus and a model was developed which describes the maximum failure strain in terms of these variables. The level of applied stress was also found to have an effect on the probability of failure. It was found that the success achieved by Sjoerdsma and Boyens (1994), in correlating failure strain data for a single grade of HIPS, could not be repeated when their model was applied to another grade of HIPS. The tw oparameter Weibull equation gave an improved correlation between the failure of HIPS and the strain on the material. Analysis of the relationship between the experimental failure strain distribution and the Weibull distribution revealed that the mean stress on the rubber phase at failure may be a better basis for achieving a Weibull distribution.
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.
Open Access
ConSERV : A methodology for the management of capital projects and concurrent engineering design using knowledge based technology.
(1997-09) Conroy, G.; Soltan, Hossein
Project management is a complex process that does not lend itself to traditional line management theories. Projects fail more times than they succeed, the measures of success and failure vary widely depending upon the management strategy and the focus of the project at the time of the assessment i.e. Cost, Time or Quality. Most of the commercially available software packages developed for the use of project managers employ dated management theories and limited reasoning ability. With over 300 variations of software tools available to the project manager selecting the most appropriate packages is becoming increasingly more difficult. Projects are managed by employing a subtle combination of elements of interdependent software tools and human expertise. Project management systems include a variety of management tools and techniques that are not equally applicable across all projects. This submission introduces ConSERV, a project management technique that uses a knowledge based risk driven approach, in which key elements of a multidisciplinary capital project are identified using the Win-prolog Flex facility. ConSERV identifies the main project elements, including the risks, sensitivities and the project success criteria. The further use of knowledge based rules provides a framework in which the decisions made by the respective users can be challenged. ConSERV advises on the project management system best suited to manage the specific needs of the engineering design and project management issues. The aims of the research described in this thesis are i) To research and analyse project management decision making processes over the life of major capital projects, undertaken in accordance with established procedures. ii) To identify, from the industrial case studies, failure mechanisms resulting from flaws in human decision making, the use of inappropriate management processes and the application of unsuitable project execution procedures. iii) To apply an established KBS development technique (KLIC) in developing the ConSERV concept and selecting the demonstrator tools. iv) To compare the effectiveness of traditional project management concepts and justify the need for a customised project management system. vi) To build two limited application demonstrators of the ConSERV concept employing advanced reasoning and knowledge based technology. The thesis argues that the complexities of managing multidisciplinary projects in a competitive technologically advanced environment demand more sophisticated methods to those presently offered. The methodology aims to minimise project failure by providing a structured risk driven procedure able to identify and customise a dynamic project management system designed specifically to meet the real needs of a project over its life cycle. Using case studies the thesis aims to contrast the effectiveness of traditional project management software, against the proposed knowledge based alternative. In support of this research work three academic papers have been published by the IJPM (International Journal of Project Management) Ref. Appendix B8 (Table 8).
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.
Open Access
The optimisation of bondcoat oxides for improved thermal barrier coating adhesion
(1998-03) Fisher, Gary Anthony; Nicholls, J. R.; Rickerby, David
Superalloys used for the critical hot sections of modem aero-gas turbines . are designed primarily to exhibit good creep and fatigue resistance, coupled with toughness and microstructural stability. However, an optimum level of these properties can only be attained with a decrease in the oxidation and corrosion resistance of the alloy. This had led to the adoption of surface coatings to protect turbine blades against the corrosive environments in which they operate. The use of Thermal Barrier Coatings (TBCs) enables the design of more efficient and powerful gas turbines whilst still providing environmental protection for the blade. A TBC is a duplex coating system, combining a ceramic topcoat with a metallic bondcoat. The ceramic layer thermally insulates the turbine blade whilst the bondcoat protects the substrate from oxidation and corrosive attack. Central to the performance of a TBC is the integrity and adherence of the alumina scale promoted by the bondcoat. The scale acts to both bond the ceramic topcoat and to act as a barrier against environmental attack. This study aimed to optimise the oxide formed by the bondcoat and so increase the life of the TBC. This was achieved by investigating the effects of bondcoat pre-treatments and by the design and development of coatings to be used specifically as bondcoats. The performance of the systems was assessed using hot oxidation isothermal and cyclic tests and the coatings were analysed using a variety of techniques, including optical microscopy, SEM, XRD and the modified scratch test. The investigation of the effects of pre-treatments revealed that the pre-oxidation of bondcoats could help promote an initial alumina scale. However, any potential benefits were overshadowed by the degradation mechanisms inherent within the coating systems. This highlighted the importance of the composition and chemistry of the bondcoat in determining the properties of the alumina scale, the relevance of which was demonstrated in the bondcoat design element of the study. Both a platinum aluminide bondcoat and a novel diffusion-type bondcoat were developed and optimised. The performances of the systems were assessed and their degradation modes analysed, resulting in a range of bondcoats which outperform those currently available, making them ideal for the design of modem Thermal Barrier Coating systems.
Open Access
An adaptive agent-based multicriteria simulation system
(1998-07-15) Neumann, Uwe; Allen, Peter M.
It is argued that traditional models of urban development are characterised by an aggregate mechanistic description of statistical units. Furthermore, important aspects of transportation are not included in these models, but urban development can be regarded as a combined process of land use change, transportation system and lifestyles. New 4 developments in evolutionary theory provide a new paradigm for a microsimulation approach on the level of individuals, which accounts for diversity, learning and change in the population o f the modelled system. In this thesis a framework for agent-based simulations will be presented for which this new evolutionary theory provides the theoretical background. The essence of the approach builds on the mutual interdependencies between all system elements, in this case inhabitants and their environment. This principle is extended to change in the interactions of the system over time, leading to an adaptive system that mutually specifies all its elements over time. On this framework an adaptive agent-based model for the use in urban simulations is built. The agents are equipped with a set of intrinsic needs, the satisfaction of which is expressed through a set of corresponding budgets. The budget state is fed into a Fuzzy Logic rule base for decision making. As opposed to many existing approaches to microsimulation, the agents are designed to change their behavioural rules during run time according to experience. Different adaptation strategies are tested and compete with each other. The results of the model vindicate the conceptual framework. The essence of the underlying theory - mutual specification based on satisficing as opposed to optimisation - leads to a cognitive approach to the simulation of socio-natural systems. Microsimulation based on adaptive agents can help integrate many aspects of urban models, which are conventionally treated by separate models and can help clarify the implications of change for the inhabitants o f an urban system.
Open Access
An investigation into product structure management using product data management systems
(1998-09) Ollerton, Patrick; Gao, James X.
With the increased use of Computer aided Design (CAD), Computer aided Manufacturing (CAM) and Computer aided Engineering (CAE), many engineering and manufacturing companies are experiencing problems with managing their product related data or information. Product Data Management (PDM) systems are tools that catalogue and manage all types of product data / information. PDM systems also offer Product Structure / Bill of Material management functions that are used for defining and analysing product configurations. In order to maximise the benefit of PDM systems, methods of creating generic Product Structure / BoM’s need to be developed and evaluated. The possibility and effects of extending Product Structure / BoM access to departments other then design is investigated in the research. Combined with these factors is the need for transfer of data from PDM systems to manufacturing software such as Computer aided Process Planning (CAPP) and Manufacturing Resource Planning (MRP). The research also contains an investigation into the potential effects of emerging technologies such as Enterprise Resource Planning (ERP), object - oriented database management systems (OODMS) and the internet. Finally, the project includes two industrial case studies focusing on Matra BAE Dynamics Ltd and Rolls - Royce Aerospace and a market research survey.
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
Optimisation and effects of coagulant type, pH and ozonation on clarification for automatic coagulation control
(1998-09-11) Marshall, N. I.; Parsons, Simon
Four phases of studies were carried out at Burham Water Supply Works in Kent. Firstly jar testing was used to compare and evaluate the performance of five coagulants. The coagulants tested were Polyaluminium Chlorides (PAC) from two suppliers, Aluminium Sulphate (Alum), Polyaluminium Silicate Sulphate (Pass 100) and Alba 18. Jar tests were carried out with coagulant alone and with non-ionic (LT20), weakly cationic (LT22s), and anionic (LT25) polymers. Secondly tests were also carried out at ambient and lower pH’s, at various pre-ozone concentrations. Jar tests indicated PAC with LT20 polymer at a pre-ozone dose of 1.5 mg/1 at pH 7.4 produced the highest water quality. Alum with LT20 was next, giving good and consistent settled water qualities. Pass 100 was circumspect and dependent upon the jar test procedure, but at optimum doses gave water qualities comparable to that of PAC. Alba 18 consistently produced poor settled water qualities. For the third phase, PAC supplied by Industrial Alum Limited (INDA) and Water Treatment Solutions (WTS), Pass 100 and Alum were selected and tested on the clarifier. Alum and PAC (WTS) were tested at pH 7.5, pH 7.3 and ambient pH at pre-ozone concentrations 0.5, 1.0, 1.5 and 2.0 mg/1 with various coagulant and polymer combinations. Pass 100 and PAC (INDA) were tested as describes but at a pre-ozone concentration of 1.5 mg/1. At optimum doses PAC (INDA) was found to perform best at a pre-ozone concentration of 1.5 mg/1 at pH 7.5. PAC (WTS) was next, with similar results. Alum produced good and consistent water qualities. Pass 100 was affected by polymer addition and was out-performed by PAC and Alum coagulants. The parameters taken into account were settled turbidity, residual aluminium, and removal of TOC, chlorophyll, phaeophytin, iron, manganese, and colour. If PAC with acid dosing can be shown to work full scale annually it would be economic to do so and to dose acid to achieve a pH of 7.5 when required. Phase four involved the evaluation of an automatic coagulant control system that would automatically optimise the coagulant, acid and polyelectrolyte doses added to the water. This was evaluated using jar tests with PAC and Alum coagulants. The AC250 system indicated the potential to improve the quality of treated water whilst minimising the coagulant dose. In this case PAC would provide further coagulant savings, with consequent sludge savings.
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
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
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.