Cold gas dynamic spraying (CDGS) is a material deposition technique, in which powder particles are accelerated to speeds of between 300-1200 m/s and upon impact deform plastically and adhere. The overall aims of this research project were to understand the bonding behaviour in cold spraying of copper, aluminium and titanium, and to produce corrosion resistance barrier layer of titanium coatings using cold spraying. The mechanism of bonding in cold spraying is still a matter of some debate. In this thesis, copper has been cold sprayed onto aluminium alloy substrates, the surfaces of which had been prepared in a variety of ways. The coating - substrate bonding was assessed via a novel intermetallic growth method along with adhesive pull-off testing. The bond strength has been rationalised in terms of a modified composite strength model, with two operative bonding mechanisms, namely (i) metallurgical bonding and (ii) mechanical interlocking of substrate material into the coating. In most cases, mechanical interlocking is able to account for a large proportion of the total bond strength, with metallurgical bonding only contributing significantly when the substrate had been polished and annealed prior to spraying. In addition, grit-blasting has been shown to significantly reduce the bond strength compared to other substrate preparation methods. Aluminium has also been cold sprayed onto copper substrates, the mechanical interlocking of substrate material was not observed and the bond strength was relatively low. Titanium particles have been deposited onto three different steel substrates, namely low carbon steel, an Armco iron, and an austenitic stainless steel. Using the novel intermetallic growth method it was found that a barrier does exist at the interface of the titanium deposited onto the low carbon steel and Armco iron substrates which is not removed in either of the stages of impact or during the heat treatment process. On the other hand, in the case of titanium deposited onto the austenitic stainless steel, the barrier is removed. Cold spraying is believed to have the potential for the deposition of corrosion resistant barrier coatings. However, to be effective, a barrier coating must not have interconnected porosity. Titanium coatings were sprayed using nitrogen as an accelerant gas at two process gas temperatures of 600 and 800˚C to reduce porosity. A modified in-situ grit blasting was used to improve the coating-substrate adhesion. The mean bond strength of the titanium deposits was ~70 MPa and tensile strength was 250 MPa. Mercury intrusion porosimetry (MIP) was used to characterize the interconnected porosity over a size range of micrometers to nanometers. The MIP results showed that in cold sprayed deposits a significant proportion of the porosity was sub-micron and so could not be reliably measured by optical microscope based image analysis. A set of free standing deposits was also vacuum heat treated to further decrease porosity levels. The effect of porosity on the corrosion behaviour of titanium coatings onto carbon steels was investigated in 3.5 wt.% NaCl. The electrochemical measurements of the coatings showed significant substrate influence when the interconnected porosity of the coating was 11.3 vol.% but a decreased substrate influence with a porosity level of 5.9 vol.%. Salt spray (fog) tests confirmed these electrochemical findings and showed the formation of corrosion products following 24-h exposure. Laser surface melting (LSM) was used to seal the top ~140 μm of the coating to eliminate any interconnected porosity. The LSM titanium coatings showed no sign of corrosion after 100-h of salt spray tests, and the open circuit potential and passive current density values were similar to those of the bulk titanium.

This thesis is concerned with the realisation of manufacturing strategies. It describes the development and testing of a structured methodology which can be used to determine some of the reasons why a firm may be unable to implement its manufacturing strategy. The methodology is known as a "congruence audit". It is widely accepted that manufacturing strategies are important, but little has been written about how they should be developed and implemented. In the literature which does exist, however, a key theme is consistency, with many authors arguing that strategies can only be realised through consistency of decision making and action. Given that people are ultimately accountable for most of the decisions and actions taken in an organisation, it can be argued that consistency of decision making and action might best be achieved if; (a) there is widespread empathy with the organisation's strategic goals (goal congruence), and (b) the organisation's signalling systems - especially those concerned with goal setting, performance measurement, feedback and reward - induce decision making and action which is consistent with these goals (system congruence). This research set out to test two propositions: (a) That a process which can be used to identify areas of either goal or system incongruence (a congruence audit) can be developed. (b) That such a process can be used to identify some of the reasons why a firm may be unable to realise its manufacturing strategy. There were three main phases to the research. Phases one and two involved the development and testing of processes for identifying areas of either goal or system incongruence. Phase three involved the integration of these processes and the application of the resultant congruence audit. In total four companies participated directly in the study. Managers from a further fourteen were consulted. The key findings can be summarised under the categories of content and process. In terms of content, the data gathered during the congruence audits indicate that the level of goal congruence is highest between a firm's senior managers and those employees who work on the shop floor. Furthermore they suggest that the way in which the goal setting, performance measurement, feedback and reward systems influence employees, varies both from firm to firm and across the organisation's hierarchy. Most importantly, they imply that one of the main reasons firms are unable to realise their manufacturing strategies is that senior managers often inadvertently encourage their subordinates to pursue courses of action which are inappropriate. In terms of process, the congruence audit serves as a structured means of: - Defining what a management group believes manufacturing should be doing. Identifying what other employees think manufacturing actually is doing. Establishing whether any mismatches in perception occur. Determining whether such mismatches in perception are a function of the organisation's goal setting, performance measurement, feedback or reward systems. Provoking debate so that the issues raised can be resolved. It should be noted that as this thesis focuses on the development and testing of a process within a limited set of firms, further research is required to confirm the findings and to explore whether the congruence audit can be used more widely.

Scheduling problems can be found in almost any field of application in the real world. These problems may not only have different characteristics but they also imply more or less complex requirements. One specific class within this domain is the cyclic job-shop problem. It occurs in various areas reaching from industrial production planning down to the systems architecture of computers. With manufacturers in particular, one can find increasing demand for effective solution methods in order to tackle these scheduling problems efficiently. This thesis will deal with the Cyclic Job-Shop Problem with Blocking and Transportation. It arises in modern manufacturing companies, where the products move automatically between the different workstations, for instance. The problem itself is not new to the research community, but hardly any work has been done in solving it. Within this thesis we will try to close this gap and present some first approaches, discussing the structure of the problem and how it can be solved. As a result, we will provide three different solution methods, including an integer programming formulation, which is solved with a commercial solver, a branch and bound algorithm and a tabu search heuristic. All algorithms are tested on a range of data sets and compared with each other. Additionally, we have worked on a polynomial solvable subproblem, which has gained more interest in the literature. As a result, a new polynomial algorithm, that outperforms the existing ones in theory as well as in empirical tests (except for some special cases) is presented. This thesis concludes with a discussion about ideas of how to improve the presented methods and some other extensions to the investigated problem.

Cold gas dynamic spraying (CGDS) is a recent development in the field of thermal spraying in which a powder feedstock can be deposited onto a substrate to form a coating without it being heated significantly. The aim of the present study was to investigate the potential for manufacturing electrical circuits for automobile applications by depositing copper tracks on non-metallic substrates. Powders were sprayed using He gas at room temperature and elevated temperatures onto a number of different polymers, ceramic and metal substrates to understand the factors controlling deposit formation and the development of adequate adhesion between track and substrate. The use of tin as an interlayer to improve adhesion was a novel development in this study. The deposits were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), profilometry, microhardness, tensile testing, adhesion testing and resistivity measurements. Investigations were also performed to study thermal stability since as sprayed deposits are in non-equilibrium state. Copper could be deposited on aluminium for a wide range of deposition parameters. Sprayed copper had nanometre size grains and demonstrated high hardness and tensile strength. Annealing resulted in recrystallization and grain growth and decrease in hardness and tensile strength. Copper could be deposited on polymers like nylon (PA66), glass reinforced nylon (PA6T) and poly (butylene terepthalate) (PBT). Copper could be deposited on a wide range of polymers when a layer of tin was deposited as a bond coat. The use of tin bond coat improved the overall adhesion of tin + copper tracks. Intermetallic compound formation was observed in tin - copper tracks after annealing at 343 K and 443 K. The formation of the intermetallic compound did not increase the resistance of tin - copper couples as the resistance of the couples after annealing were found to be below that of the as - sprayed couples where the intermetallic compound formation had not taken place. This effect is a result of the recovery/recrystallization taking place in copper which reduces the resistance.

Woven fabrics have found enormous application in our daily life and in industry because of their flexibility, strength and permeability. The aim of this work was to create a general model for through thickness air permeability and thermal conductivity for different types of textile fabrics because of their applications in industries and everyday life. An analytical model to predict through thickness air permeability was developed. The objective was to create a model which will take into consideration the two primary mechanisms of air flow in fabrics: through the gaps between yarns and through the yarns. Through thickness air permeability was measured according to British Standard BS EN ISO 9237: 1995. Several fabrics were tested including plain weave, twill weave and satin weave fabrics. The analytical model is a combination Kulichenko and Van Langenhove's analytical model which predicts the permeability through gaps between yams with Gebart's model to predict permeability within yams. Analytical predictions were compared to the experimental data. Computational modelling of through thickness air permeability using Computational Fluid Dynamics CFD software is presented in this thesis. The Polymer Composites Research Group in the University of Nottingham has created a textile schema, named TexGen. The prerequisites of this software were to be able to model various types of textile structures. A CFD model using CFX 11.0 was developed to be able to predict fabric permeability. In addition, an analytical model was developed for fabrics deformed by shear, compaction and tension. Experimental work for through thickness air permeability of sheared fabric was used to verify predicted results. An analytical model for thermal conductivity of fabrics was developed including the influence of moisture content on thermal conductivity. Two existing approaches for single-layer fabrics are described and compared: rule of mixtures and thermal resistance approach. A me6iod for thermal conductivity prediction for multiple layer fabrics is presented. The results are compared to the experimental data and analysed. Some predicted results were in excellent and good agreement with experimental data whereas other predicted results were in poor agreement with experimental data as they were dramatically affected by the assumptions made in the analytical model.

Assembly systems today are exposed to market trends that have become increasingly more dynamic and unpredictable, requiring product changes and adjustments which emphasise de need for more flexible systems. The requirement for increased responsiveness has led to the development of new modular concepts which provide the bases for achieving higher system adaptability through increased component/module interchangeability and reusability. The modularization of physical and control infrastructure does, however, only address one aspect of the issue and there is still a lack of appropriate tools and methods to support the rapid configuration and reconfiguration of such systems for changing sets of requirements. This work proposes a new distributed methodology for the configuration and reconfiguration of Modular Assembly Systems (MAS) through the use of agent technology. The new methodology defines a comprehensive model for the structured description of the MAS requirements, equipment modules and the configuration results. This thesis proposes a new agent architecture for the self-configuration of equipment modules into systems based on a given set of requirements, as the core of the self-configuration methodology. This architecture introduces the overall behaviour of the methodology through the definition of agent types, roles and overall interactions. Furthermore this work describes the development of the specific models and methods for the local behaviour of each agent. These enable the actual decision making method for the agents to achieve configuration solutions. This work also reports on a new methodology for the early performance simulation of MAS characteristics that can be used in conjunction with the configuration methodology.

Manufacturing systems face now more than ever the effects of an uncertain environment, which is triggered by constantly changing customer needs. Numerous approaches have been proposed to provide manufacturing systems with the capability to satisfactorily perform under situations of uncertainty, particularly by improving their level of responsiveness. Manufacturing flexibility is a dimension of responsiveness which aims at reacting to unpredictable events with little penalty on performance. Nonetheless, there is a strong perception that the achievement of manufacturing flexibility exclusively depends on the availability of highly automated equipment. This is a misleading belief considering that manufacturing systems are a collection of interacting components sharing a common objective and therefore there must be alternative system’s aspects, other than automation, contributing to the achievement of manufacturing flexibility. This study expands on existing knowledge by exploring the concept of manufacturing flexibility through the investigation of the dimension of uniformity. The analysis of this dimension has provided a valuable perspective from which to improve understanding of flexibility in manufacturing and identify alternative ways to achieve it. By combining the analytical capabilities of discrete event simulation, statistical design of experiments and optimisation, it has been possible to identify specific factors, optimal system configurations and response trade-offs that, within the context of semi-automated cellular manufacturing systems, constitute a significant contribution in the attainment of manufacturing flexibility.

Cutting and packing problems are increasingly prevalent in industry. A well utilised freight vehicle will save a business money when delivering goods, as well as reducing the environmental impact, when compared to sending out two lesser-utilised freight vehicles. A cutting machine that generates less wasted material will have a similar effect. Industry reliance on automating these processes and improving productivity is increasing year-on-year. This thesis presents a number of methods for generating high quality solutions for these cutting and packing challenges. It does so in a number of ways. A fast, efficient framework for heuristically generating solutions to large problems is presented, and a method of incrementally improving these solutions over time is implemented and shown to produce even higher packing utilisations. The results from these findings provide the best known results for 28 out of 35 problems from the literature. This framework is analysed and its effectiveness shown over a number of datasets, along with a discussion of its theoretical suitability for higher-dimensional packing problems. A way of automatically generating new heuristics for this framework that can be problem specific, and therefore highly tuned to a given dataset, is then demonstrated and shown to perform well when compared to the expert-designed packing heuristics. Finally some mathematical models which can guarantee the optimality of packings for small datasets are given, and the (in)effectiveness of these techniques discussed. The models are then strengthened and a novel model presented which can handle much larger problems under certain conditions. The thesis finishes with a discussion about the applicability of the different approaches taken to the real-world problems that motivate them.

The thesis presents research carried out in the field of design for microassembly (DFµA), a field that has hereto been characterised by the absence of well defined methodologies intended to facilitate transfer of prototypes from the research lab to production on industrial scale. A DFμA methodology has been developed, serving the purpose of integrating product and micro assembly process development. It aims in particular at increasing the efficiency of the microproduct development process, decreasing the development time and the product and process cost, and enhancing the product quality. Chapter 1 presents the motivations, objectives, and structure of the thesis. The work carried out is inspired by the need to overcome barriers currently existing between the making of single research products and production on an industrial level. The main objective is to contribute to the creating of a novel DFμA that supports product design and process selection, thereby facilitating the efficient assembly of complex three-dimensional miniaturised devices. This is complemented by a range of secondary targets that deal with the development and verification of supporting methods and models related to DFμA. The summary of a comprehensive literature review is given in chapter 2. The survey provides results of studies closely related to the work reported in this thesis and relates that work to a larger ongoing dialogue about the topic of assembly and design in the microworld. Chapter 3 outlines the research approach adopted here for the developing of a DFμA methodology. It carefully analyses the way in which the knowledge gaps identified can be addressed and how the stated objectives can best be achieved. The key contributions made to the developing of a DFμA methodology are presented in chapters 4,5, and 6. The micro assembly process capability model is described first, in Chapter 4. It constitutes the first attempt made at introducing a general framework for capturing of microassembly characteristics. The model developed enables selection and characterisation of microassembly processes. A framework to characterise the model's application to microjoining, -feeding, and -handling is as well suggested. Chapter 5 concerns the actual DFμA methodology. The methodology's layout and structure are introduced in detail. Moreover, the main functions and key phases of the methodology are explained. Special attention is paid to the integration of the microassembly process capability model and to the development of further elements used within the methodology, such as support in product design. Provided in Chapter 6 is a comprehensive analysis of conventional DFA guidelines, intended to explain how the microspecific guidelines have been formulated. The chapter also describes how these are implemented within the overall DFμA methodology. The procedure of validating and illustrating the methodology, which includes applying it to practical test cases, takes place in Chapter 7. The thesis is concluded in Chapter 8, wherein evidence of the originality of the knowledge contribution achieved through the work presented is highlighted. Opportunities for further research work building on the

Reliability engineering techniques have been used in the manufacturing environment for many years. However the reliability analysis of repairable systems is not so widely practised in the steel manufacturing environment. Many different analysis methods have been proposed for the modelling of repairable systems, most of these have had limited application in the manufacturing environment. The current reliability analysis techniques are predominantly used by engineers to construct a “snapshot” in time of a manufacturing system’s reliability status. There are no readily identifiable applications of reliability modelling techniques being applied to repairable systems over a long time period within the manufacturing environment The aim of this work is to construct a method which can analyse and monitor the reliability status of multiple repairable systems within the steel plant over an extended operating period. The developed analysis method is predominantly automated and is facilitated by applying standard reliability analysis techniques to all of the repairable systems failure data sets under review. This Thesis illuminates the methodology used to fulfil the remit of this research by the following sequential steps: Developing a new methodology for the application of reliability analysis techniques to repairable systems within a steel manufacturing facility Utilised an innovative step of combining three reliability analysis methods as complimentary activities Constructed an automated reliability analysis model which fulfils the project remit. In addition the model is capable of the long term monitoring of repairable system reliability The new reliability analysis method has been delivered to Tata Steel and is installed in the Port Talbot Technology Group with a direct link to the Hot Strip Mill (HSM) monitoring database. This reliability analysis method has been tested with four years operational data from the Hot Strip Mill manufacturing area and the analysis has shown that changes and trends in all systems reliability status can be easily identified.