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

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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
Conceptual design of a support documentation system to assist troubleshooting in manufacturing
(2005-04) Juliao, Jorge; Greenough, Richard
This research explores the conceptual design of a Support Documentation System (SDS), to assist manufacturing maintenance personnel during troubleshooting. Manufacturing systems maintenance is a crucial element of any organisation’s operating strategy. One of its main goals is to reduce downtime, both by avoiding the occurrence of failures and by effective reaction to breakdowns. Currently, most downtime reduction studies focus on the prevention of failures. Although these studies have made a significant contribution toward downtime reduction, it is impossible to prevent all failures. As such, troubleshooting will always be necessary for maintenance personnel to provide an effective contribution to their organisation. This research proposes a Support Documentation System that will improve maintenance through documentation management. It is argued that troubleshooting time will be reduced since such a system could provide maintenance personnel with enhanced access to support documentation, particularly to failure records. Until this research, little direct empirical evidence had been collected about the feasibility of such a system, and about the performance of current systems regarding troubleshooting support. There had also been no evidence concerning maintenance personnel requirements for improved support documentation. The objectives of this research are to assess the feasibility of the SDS, to determine why current systems do not effectively support troubleshooting, and to identify key features for the development of the SDS. To fulfil the objectives of this research, exploratory investigations were conducted. Questionnaire and interview surveys of maintenance practitioners, equipment vendors, and CMMS developers were performed to determine the status of failure records management and the reasons for the failure of current systems. A case study strategy was employed within three companies to identify requirements for the development of the SDS. The findings of this research are that the development of an SDS is feasible, and that current systems do not effectively support troubleshooting. The research identifies a set of design features for the SDS. It presents the end-user requirements, a ranking of most relevant troubleshooting data to be included in the failure records, and a list of record attributes that are to be used to better identify and classify records. The latter attributes constitute the means to manage failure records in a systematic way.
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
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
A design methodology for jigless aerospace manufacture
(2005-03) Burley, Graham John; Corbett, John
Between 10% and 40% of the overall cost of an aerostructure can be directly attributed to the cost of type specific, hard-tooling. Hence, any attempt to reduce the cost of aerostructure must eventually focus on reducing the need for type specific hard-tooling. The tooling is one of the major investments made during the development phase of an aircraft programme, accounting for more than a third of the development cost of a civil aircraft and nearly a quarter of the development cost of a military aircraft. The development phase for civil aircraft typically lasts two to four years and the tooling cost represents a multi-million pound forward investment with a long pay back period. Consequently, reducing the need for type specific hard-tooling will significantly reduce development costs and the time from concept to market. This thesis describes a new design-for-assembly JAM Methodology that reduces the need to manufacture and build with type specific hard-tooling. The Methodology was developed by identifying, utilising and developing existing design methodologies, and by identifying and applying enabling technologies. The methodologies are integrated to create a design algorithm that identifies and draws on the enabling technologies to achieve minimal hard tooling assembly concepts. Included in the methodologies is an innovative systems analysis tool. This enables the comparison of alternative assembly concepts ahead of the detail design, and the prediction and control of the total assembly error at the design stage. The first part of the thesis describes the development of the JAM Methodology and explains the function and purpose of each step. The second part of the thesis demonstrates, and tests, two slightly different forms of the Methodology in the re-engineering of an existing aerospace structure, and in the designing of a new aerospace structure. Publications relating to this research thesis include eleven authored, and co-authored, refereed conference papers, one journal article, and two EPSRC final reports.
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
The development of a bacterial biosensor for the analysis of benzene in workplace air
(2004-12) Lanyon, Yvonne H.; Tothill, Ibtisam E.
The presence of toxic volatile organic compounds (VOCs) such as benzene in workplace air has accounted for the death of many occupationally exposed workers over the last century. The conventional gas chromatographic method of monitoring benzene is known to be costly, complex and in most cases, laboratory-based. Therefore a need exists for the development of low-cost, easy to use, portable devices that can be used on-site for the rapid evaluation of airborne benzene. In this thesis, the development of an amperometric bacterial biosensor based on Pseudomonas putida ML2 for the detection of airborne benzene is described. Benzene can be used by the bacteria as a sole carbon source, and its aerobic degradation can be measured using a dissolved oxygen electrode. In this work, P. putida ML2 cells were immobilised between two cellulose acetate membranes and fixed onto a Clark dissolved oxygen electrode. Biosensor responses were investigated in batch and kinetic (Flow Injection Analysis) mode, and also using screen-printed electrodes. In each case, the response characteristics, sensitivity, reproducibility and lifetime of the sensor were investigated, as well as construction techniques and operational parameters. The applicability of the biosensor for the analysis of air samples containing benzene was investigated. Air samples were collected from an exposure room of controlled concentration using charcoal adsorption tubes, and benzene extracted with solvent desorption using dimethylformamide (DMF). DMF proved to be compatible for use with the biosensor, causing minimal interference with the sensor response and causing no toxic effects on the bacterial cells. The biosensor displayed a linear detection range between 0.025 - 0.15 mM benzene based on standard solutions containing a maximum of 2% DMF, with a response time of 6 minutes. This linear detection range allowed the analysis of air containing between 3-16 ppm benzene, based on a 60-minute sampling period. The inter-assay reproducibility of the sensor response to standard benzene calibration curves under such conditions gave a 3% variation coefficient based on 5 separate assays (n = 17) using the same bacterial membrane. The FIA system was easily transported to an in situ location for the air sample analyses, and a correlation was obtained between the biosensor and gas chromatography (GC) results for the exposure room air samples investigated. Moreover, the biosensor displayed no interference to other benzene related compounds in the BTEX (benzene, toluene, ethylbenzene, xylene) range. Overall, this thesis has described the development of an alternative method for the monitoring of benzene in workplace air, using a bacterial biosensor based on Flow Injection Analysis. Advantages over the conventional GC methods including ease of operation, cost-effective production and portability demonstrate that the P. putida ML2 biosensor has potential applications as an alternative means for the rapid analysis of workplace air containing benzene.
Open Access
The development of machine algorithms for the Cranfield underwater laser stripe imaging system
(2003-04) MacAdam Sproat, G. O.; Tetlow, S.
When using conventional illumination in the underwater environment, the greatest problem faced has always been that of back-scatter. This reduces visual quality both to the naked eye and through the use of underwater cameras. This project continues research into a hybrid underwater laser viewing system, combining a laser scanning technique with conventional underwater viewing system technology. The use of carefully positioned lighting can greatly reduce the problem of back-scattered light, improving image definition and contrast. With the use of a laser light source this can be improved even further within a more flexible system. Utilising two scanning devices a narrow stripe of light can be formed which is scanned over a target area. Small successive regions of any object lying within that area can then be illuminated, isolated and extracted using image processing to compile a complete image of the object. For the purposes of surf zone and shallow water mines counter measures, the system requires reliable machine algorithm based image processing techniques, to compile a constructed image of target objects within highly turbid regions. Projected stripes take on various characteristics dependent on the geometry and aspect of the object which they fall upon and the conditions experienced. High levels of turbidity leading to significant noise, creates considerable difficulties in the isolation of the stripe region and the extraction of meaningful visual information. The success of any technique would rely upon the overcoming of these difficulties, allowing the system to offer the operator the most useful visual information permissible in the final compilation of the image. Through various image processing techniques these factors have been tackled and their effects on the final image, greatly reduced. The result is the creation of highly stable and effective processing techniques allowing improved object definition and recognition, in levels of high turbidity.
Open Access
Dimensioning of an automotive final assembly shop using a system of key performance indicators
(2006-01) Gruneisl, Markus; Kay, John M.
All worldwide operating automobile manufacturers are on the constant search for the optimum between desirable flexibility on that one hand and required cost productivity on the other hand. In particular, the planning of a new final assembly shop of a car manufacturer is a big challenge since a huge number of influencing factors must be taken into consideration, so that in the end a best-practice final assembly shop with the desired attributes is created. To minimise the risk of bad planning, the length of time for the planning process should be shortened and at the same time the planning exactness should be improved with the help of new tools. This research project demonstrates that in the early stages of the planning process key performance indicators could be a proper instrument to achieve the the desired effects. Even if key performance indicators have been used in many areas of industry over several decades, this is the first research project which deals in this degree of accuracy with the dependencies between the different key performance indicators during the factory planning process for a new final assembly shop of a car manufacturer. Following the basic idea of 'System Thinking', numerous key performance indicators were linked to each other in an adaptable system of key performance indicators. During this research project, the developed model was successfully evaluated with four locations of the research partner BMW Group. Since the results are all between ± 20%, which is a sufficient exactness for this planning stage, there is great confidence that this general system of key performance indicators could also be important to other automobile manufacturers. The findings of this research project should serve as a basis for other researchers in this field to enhance the scarce theories about the dependencies. Besides, the software 'Powersim' and the chosen approach of 'System Thinking' doubtless can be transferred to other industrial areas with similar challenges.
Open Access
Ecotechnology as interdisciplinary method: ecological engineering of water quality
(2000-03) Browne, Brigid; Seaton, R. A. F.
The principle objective of the work is to explore an ecotechnological, interdisciplinary approach to studying ‘natural’, in ecologically engineered terms, systems. This requires the investigation of two sub-objectives. The first of which is to develop an assessment method for investigating the bi-directionality between water quality (biochemical) and ecological change as a socially directed biophysical or ‘natural’ technology. Supporting this first sub-objective is a second one which offers an innovative approach, in the form of developing a new classificatoiy framework or ‘ecotaxonomy’, which uses the concepts of hierarchy and emergence in describing the biological components (bios) of such ‘natural’ systems. Central also to the research is a case-study which relates to an issue of perception in the way that treatment processes at a water treatment works are generally regarded as separate from the treatment processes of water in ‘natural’ watercourses and the aquatic ecologies endogenous to them. Wastewater-fed aquaculture systems are a principle example of an ecological engineered treatment system or socially directed biophysical technology, which bridges this perceptual divide. Such an aquaculture system is used to test the new taxonomic framework. As a result of the development of a conceptual model and the hybrid classification exercise several interesting observations are made. Firstly the way in which the ecotaxonomy as a hybridization of traditional biological and ecological classification enables the systems biochemistry to be mapped to its ecology. Secondly the utility of ‘inter’ taxonomic systems generally as mapping functions to facilitate knowledge transfer and interdisciplinary research. Thirdly the creation of a classification systems which allows, by merit of it’s structure, for the phenomenon of emergence. Other interesting side issues are raised such as the role of ‘objective’ as opposed to ‘natural’ biological classification systems and further implications on the effect of changing biological taxonomic structure are discussed, with particular reference to principle ecological theories such as the diversity-stability hypothesis and the nature of biological variety and functional diversity in natural systems generally. If social needs, such as water treatment, are to ‘harness’ natural biological systems then these properties of ecotechnology need to be further developed.
Open Access
An electrochemical investigation of erosion corrosion of duplex stainless steel in sea water containing sand particles
(2001) Hussain, Essam A. M.; Robinson, M. J.
Passive metals, like stainless steels, are usually protected from corrosion by a thin oxide film on the surface. If the film is stable it will reform spontaneously when it becomes damaged. Erosion-corrosion of passive metals proceeds by the repeated removal and repair of the oxide film. Erosion corrosion behaviour studies were carried out on UNS 31803 grade of duplex stainless steel in seawater using a water jet impingement apparatus. Electrochemical polarisation scans and optical film thickness measurements were utilised to measure the rate of repair of the passive film while varying the fluid flow velocity in seawater with and without the addition of sand particles. The value of the passive current density revealed the severity of the attack, as the fluid velocity was changed on the surface of the material. This demonstrated the pitting of the ferrite phase at 380 mV and breakdown of the austenitic phase at 880 mV. With the presence of sand particles, the passive current density was significantly enhanced and increased up to 7.5 jiA/cm2 for 3 grams and the value stayed constant as the sand concentration increased to 4 grams. Both the current and potential versus time measurements supported the polarisation results. In general, the passive film produced an interface colour of the first or second order. Modelling of the erosion-corrosion behaviour under particle impingement was characterised by developing a relationship between passive film colour thickness, sand particle energy from the water jet impingement system and the electrochemical scans. It was possible to show that the mean charge passed for a single particle impact of 0.01 impact was 6 x.10*12 coulombs and the corresponding absolute current was 6x 10'12 Ampere. Overall, the conclusion drawn from this work was that the UNS31803 duplex stainless steel would exhibit a good resistance to erosion corrosion if used in ship power plants and offshore piping giving a depth of attack between 0.07 and 0.08 mm/year.
Open Access
Electrochemical sensors development for toxic heavy metals
(2005-03) Md Noh, Mohd Fairulnizal; Tothill, Ibtisam E.
Heavy metals are toxic environmental pollutants and the development and application of decentralised monitoring equipment for their real time monitoring is gaining rapid popularity. Research within this thesis presents the work undertaken to develop single-use sensors for on-site detection of toxic heavy metals in various environmental matrices. The fabricated three-electrode configuration system (graphite carbon/gold-working electrode, carbon-counter electrode and silver/silver chloride - reference electrode) was coupled with square-wave anodic stripping voltammetry (SWASV), constant current stripping chronopotentiometry (CCSCP) or linear sweep voltammetry (LSV) in order to provide a mean of a relatively inexpensive on-site detector for trace levels of lead (II), copper (II), cadmium (II) and arsenic (III). Detections and determinations of these metals were carried out on bare mercury film screen-printed carbon electrode (SPCE), mercury film SPCEs modified with cysteine and bare screen-printed gold electrode (SPGE) using the optimised procedures developed during this investigation. Modifications of mercury film SPCEs with cysteine provided means of increasing the sensitivity of stripping response obtained at the mercury film SPCE. Detection limits of 0.4, 0.7 and 3 jug V1 were estimated for lead (II), cadmium (II) and copper (II) measurements, respectively for 120 s deposition times. For the bare SPGE, which provides mercury-free sensor, detection limits of 2 and 5.8 jig I' 1 were obtained for lead (II) detection using SWASV at 240 s and 120 s deposition times. Cadmium (II) was found to interfere with lead (II) measurement with SPGE. Arsenic (III) was also detected with SPGE and detection limit of 0.7 pg I' 1 was obtained. Other metals such as lead (II), copper (II) and mercury (II) were tested for interference study with As (III) measurements. With the optimised working conditions, the results obtained indicate that the screen-printed electrochemical sensors are sensitive and reproducible for the CCSCP, SWASV and LSV determination of lead (II), copper (II), cadmium (II) and arsenic (III) in the microgram per litre - milligram per litre range. The reproducibility of the measurements, which also contributed to the interest in developing the electrochemical sensing devices for metal ions, was below 15 % for the mercury film SPCE, cysteine modified SPCE, and SPGE. Surface analysis was conducted using Scanning electron microscopy (SEM) in order to study the electrode surface characterisation. The application of the various electrodes to real samples was demonstrated and proved successful for both waste water and soil extracted samples including in situ measurements at a contaminated site in Spain and Germany.
Open Access
Enhanced surface finishing of bearing raceways
(2000-10) Knight, Peter; Corbett, John
Bearing surfaces are highly engineered and high precision parts in regard to surface finish, waviness, form and dimensional size. Surface finishing techniques will not only affect the surface finish and texture but the mechanical properties of the surface and subsurface including surface stress state and hardness as well as chemical properties. The bearing surface is a functional surface influencing fatigue, wear, and friction, noise and lubrication regime. Bearings are low cost, high volume commodity products, which adds additional constraints to any manufacturing process of low cost, fast cycle time and automation. This thesis documents the development route for a superfinishing technique for bearing raceways. Initially work was performed on electrochemical machining (ECM) of raceways, but this was found to improve the surface finish too slowly and gave poor waviness as a result of non-conductive MnS inclusions becoming exposed on the bearing surface during ECM. Abrasive honing stones or superfinishing tapes were then combined with the ECM, a process called electrofinishing to remove these MnS peaks. A beneficial interaction between the ECM and the abrasive resulted in reduced loading of the abrasive and therefore more aggressive cutting and for longer. Using a fine grit (3- 4 pm) CBN vitreous bonded honing stone the surface finish of a ground ring (0.3 pm Ra) or a turned surface (1.2 pm Ra) could be improved to <0.02 pm Ra in around 6 seconds. These new surfaces showed low Rtm and Aq (slope), but also acceptable or very good levels of waviness. The material removal is dominated by the ECM process while the rate of surface finishing is controlled by the abrasive process. The process of electrofinishing gives the possibility of fast, high and controlled material removal capability combined with fine surface finishing, which presently must be achieved by throughfeed honing or two stage honing. The main difficulty to overcome is achieving a stable consistent honing needed for a production process. These difficulties arise from the incompatibility of the ECM electrolyte and honing fluid (usually an oil). Improvements were made by using a water soluble synthetic metalworking fluid mixed with the NaN03 electrolyte. Further improvements are possible by better choice of honing stone, better application of stones, while for superfinishing tapes, the use of tape feed and oscillation will give further improvements.
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
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
Information behaviour in the customer-focused small manufacturing company
(2000) Martin, Valerie Ann; Sackett, P. J.
This thesis explores the nature and management of information in customer focused small manufacturing companies. Small manufacturing companies (SMCs) face increasingly changing and wider customer demands. They are often power cultures, with informal information and communication flows. Informal information is no longer enough in the face of growing complexity. Formal information is often about co-ordinating processes, for example, BS EN ISO quality standards, or simply recording customer information instead of relying on memory. Academic approaches to the management of information are traditionally based in case studies of large companies and are driven by sophisticated electronic information systems. An alternative approach to identify and analyse information is adopted for small manufacturing companies, for a richer exploration of both informal and formal information. The process of data collection is explained in depth, and the findings illustrated in a conceptual model. The nature of information is discussed, showing that there are two dimensions - activities and interpretations. The findings show that information is highly systemic, and requires a qualitative, flexible approach to identifying and understanding it. The final outcomes show that informal information maintains flexibility, but there is an increasing need to support this with formal information, for traceability. The management of an information culture is crucial to this, manifested in the behaviour of people. Most significantly, it shows that there is a contention between the prevailing power culture and the uncertain and complex customer demands, and these factors sometimes prevent the effective management of information behaviour. The research explores a previously overlooked aspect of small companies - the apparent chaos and informality they operate in every day, and the vital contribution that this may play in their survival in the growing knowledge economy.
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
Interior frontal crash protection for passenger cars at high delta-v - possibilities and limitations
(2005-03-19) Mellander, Hugo; Irving, Phil E.
The purpose of this study was to analyse the possibilities to design an effective interior restraint system for the driver of a passenger car subjected to fully distributed frontal crashes in the speed range of 56 to 80 km/h (35 to 50 mph). In order to limit the research area the issue of structural integrity of the occupant compartment will not been addressed in this study. In other words it has been assumed that the frontal crush zone is large enough to absorb the kinetic energy and that the occupant compartment is not heavily deformed. A computer model of a driver restraint system including an airbag, a seat belt, knee padding, seat and a steering wheel with column has been developed with a 50%-ile crash test dummy as the driver. The computer model results have been validated by means of mechanical sled tests. A decelerating sled has been used for all the mechanical testing. The sled has been equipped with a mock-up of the frontal section of the occupant compartment of a passenger car including the steering wheel, steering column, seat and the driver restraint system consisting of an airbag, a knee restraint and a three-point seat belt. The crash pulse at §9 56 km/h, used in simulation and experimentation, has been selected to be representative for a mid size car from the nineties. To assess a realistic crash pulse for a high velocity fully distributed frontal crash with a mid size car from that period a crash test was performed at 80 km/h. A number of input parameters describing the restraint system have been selected for a two level variation analysis using design of experiment technique (fractional factorial design at two levels). The restraint configurations defined in the matrix have been run through the computer model at #G 56 and 80 km/h impact velocities. The variables with the greatest effect on the dummy response have been identified. Some of the restraint system configurations have also been tested on the mechanical sled. The results show that, for a given crash pulse, it is possible to design an interior restraint system with a low risk of injury at 80 km/h impact given that no significant intrusions into the occupant compartment occur. The importance of tuning the characteristics of the restraint systems to the condition at hands i.e. the crash severity to achieve improvements in driver protection is also demonstrated.
Open Access
Investigation of helicopter loading spectra variations on fatigue crack growth in titanium and aluminium alloys
(1999-04) Buller, Richard Gregory; Irving, Phil E.
An investigation has been made into the effect of omitting small, vibratory load cycles from a helicopter load spectrum on the fatigue crack growth rates of high strength titanium (Ti-lOV 2Fe 3A1) and aluminium (7010 T73651) alloys. The investigation is made in the light of new requirements for the damage tolerance design of transport helicopter structures that have normally been designed to safe life criteria. The work aims to improve the damage tolerance design of helicopter structures by understanding the contribution of the vibratory load cycles to fatigue crack growth damage. The experimental work consisted of two parts that considered fatigue crack growth under simple overload type loading and complex fatigue load sequences using compact tension specimens. Simple overload and underload tests were run under near-threshold, plane strain crack growth rates typical of those experienced in helicopter components. These were supplemented by crack closure measurements made using a strain gauge adhered close to the crack tip. Fatigue crack growth rate retardation was observed after an overload and this was reduced if a tensile underload was subsequently applied. The experimental evidence suggested that observed crack growth transient behaviour could be explained by a residual stress field mechanism ahead of the crack tip with closure only serving in a secondary role to modify the applied external loading. A fatigue load sequence was developed for a helicopter rotorhead component and included representations of manoeuvre loads superimposed with the high mean stress, vibratory load cycles. A technique of progressively omitting small load cycles of increasing range from this sequence was used to determine the effect of these cycles on the fatigue crack growth. It was found that the these cycles of 16% range caused up to 80% of the total crack length damage and that the observed crack growth rate of the cycles was three times greater than that predicted by a conservative fatigue crack growth model. These are significant observations because vibratory cycles are usually considered to be non-damaging under a safe life design to which most current transport helicopters have been certified to. It was proposed that the accelerated growth rate of these cycles was caused by frequent underloads in the rotorhead loading sequence. A residual stress field model was invoked to explain this behaviour. The results are used to provide guidance for damage tolerant design of helicopter structures.
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.