Vibration isolation is an important requirement for many engineering systems. In particular, in the context of vibration isolation for light-weight automotive vehicles that exhibit wide variation in sprung mass, several limitations are associated with passive isolation systems. Such passive systems cannot obtain wide variations in the suspension parameters which required for reliable performance. While these technical drawbacks can be overcome by implementing active systems, these are associated with an increase in complexity, cost and potentially negative impact on reliability. In this context, composite fluid materials, which combine different components in a way that enhances an isolator’s performance, could represent a possible alternative approach with promising potential. However, the application of composite fluid materials for vibration isolations is still an underdeveloped area. The composite fluid material that is the subject of this research is referred to as Foam Filled Fluid (FFFluid). It is composed of three components, namely compressible (foam) particles, a viscous carrier fluid and a packaging material. This composite material has recently been investigated for applications in impact energy management but is not understood in anti-vibration application. Thus, the objective of this research was to understand the mechanisms, to characterise design parameters and to predict the responses of such composite material when used for vibration isolation systems. A theoretical understanding of the working principle for a FFFluid-based isolator was first achieved. Then, experimental work was conducted to assess the performance of such a device. The characterisation of the composite material was carried out via a systematic study; this study was then validated by an experimental -ivprogramme based on a Design of Experiments approach. Finally, empirical prediction models of the system were extracted by analysing the obtained data statistically. The conducted research shows that a FFFluid-based isolator possesses several advantages over commonly used existing solutions. Its main benefit is the potential capability of adjusting stiffness and damping coefficients by changing one component or more of this composite material. It was shown that increasing the volume of the composite material led to increased stiffness and damping coefficients. Besides, increasing the ratio of fluid in the mixture caused to increase the stiffness coefficient. The most important parameters that have an influence on the response of FFFluid were: the size of foam, the ratio of foam to fluid, volume of the material and fluid viscosity. Therefore, empirical models were established based on these parameters, the accuracy of these models were 85% Through the study of this novel material, the application of the FFFluid concept as a vibration isolator solution was studied. In practice, the design parameters of such a system could be adjusted through a control mechanism, to provide an adaptive solution. This could represent a suitable means to bridge the gap between passive and active suspension system in the context of vibration isolation for light-weight vehicles.

This thesis presents a modern method to evaluate spur gears based on the transient elastohydrodynamic lubrication (EHL) emulation of the full meshing cycle, evaluating elastic stresses in the gear flanks, collecting the stress history and applying stress and strain-life methods to calculate fatigue parameters and cumulative fatigue damage, i.e. predicting the fatigue life taking measured surface roughness into account. The EHL model is formulated as the coupled system of the hydrodynamic Reynolds equation and the elastic deflection equation. These are solved simultaneously including the transient effect by incorporating the squeeze film term of the Reynolds equation with a Crank-Nicolson discretization of time. The finite difference discretisation of the elastic deflection equation utilises the differential form first formulated at Cardiff to allow coupling of the equations. The Reynolds equation can be discretised either by a finite difference or by a finite element method. The coupled system is solved simultaneously either by a narrow bandwidth Gaussian elimination or a Gauss-Seidel iterative method. The elastic stresses due to the superimposed discrete values of the EHL pressure and shear stress at the EHL mesh nodes are evaluated by carrying out the necessary convolution of the stresses by a Fast Fourier Transform method. The weighting functions required have been calculated analytically. The stresses are obtained on the EHL solution mesh and are interpolated to meshes fixed in the pinion and the gear flanks. They are then sorted and stored efficiently to enable fatigue life prediction algorithms to be applied. A detailed description of the EHL and the stress evaluation models are provided as well as a brief description of some fatigue life theories and calculations. The results of the complete analysis are provided for test gears obtained from the NASA Glenn laboratory fatigue tests and the Newcastle University Design Unit micro-pitting investigation. The analyses were carried out for real operating conditions from gear testing under extreme conditions. The surface roughness profiles used were real measured profiles taken from the test gears after initial running-in. The simulations reported are therefore as realistic as can be achieved and represent the true mixed lubrication conditions occurring in heavily loaded gears. The research also shows the importance of precise alignment of the roughness profiles in these conditions.

The non-invasive liquid-crystal and schlieren methods have been applied to the study of convective heat transfer in rib-roughened channels. The importance of investigating heat transfer from rib-roughened surfaces and of using non-invasive tools to gain information on thermal fields for similar complex geometries is stressed in Chapter 1. Chapter 2 is devoted to a description of main important published papers related to this project. Firstly, studies concerning heat transfer from rib-roughened surfaces in forced and free convection are listed and discussed in detail. Moreover, a literature survey on optical methods in heat transfer is presented, with special attention to the methods (liquid-crystal thermography and schlieren) applied in this study. Experiments performed by using liquid-crystal thermography are presented and discussed in Chapter 3. Three configuration geometries have been investigated: a smooth channel (having flat plates) and two different ribbed channels. The investigated heat transfer mechanism was forced convection. These experiments were performed at City University, London. Chapter 4 is devoted to experiments performed by using the schlieren optical technique. Again, the experimental study included a preliminary activity on smooth channels, followed by tests performed for rib-roughened channels. The heat transfer mechanism was natural convection. These experiments, which constitute the main body of the project, were conducted at the Dipartimento di Termoenergetica e Condizionamento Ambientale, Universita di Genova, Italy. Finally, most important conclusions are drawn in Chapter 5. Details of relationships between the recorded optical data and the thermal field (or heat transfer coefficients) are reported in Appendix Al and A2 for the liquid-crystal thermography and the schlieren method, respectively.

Compressor plant frequently operates under unsteady conditions. This is due to pressure fluctuations, variable flow demand, or unsteady inlet conditions, as well as shaft speed variation. Also, following demand, compressor plants often work intermittently with frequent starts and stops. This may cause premature wear, decrease of compressor performance and even failure, which might cost millions of pounds to industry in downtime. However, there is still a lack of published data which describes intermittent plant behaviour, or predicts the effects of unsteady operation upon compressor plant performance. Thus, there appears to be a need to develop a mathematical model to calculate compressor plant performance during intermittent operating conditions and to verify this model with experimental data. Accordingly, this thesis describes an experimental and analytical study of screw compressor plant operating under unsteady conditions. For this purpose a one-dimensional model of the processes within a compressor was used, based on the differential equations of conservation of mass and energy, extended to include other plant components, such as storage tanks, control valves and connecting pipes. The model can simulate processes in both oil-free and oil-injected compressor plants during transient operation, including the effects of sudden changes in pressure, speed and valve area. Performance predictions obtained from the model gave good agreement with test results. This model can, therefore, be used to predict a variety of events, which may occur in everyday compressor plant operation.

Abrasive micro-waterjet processing is a non-conventional machining method that can be used to manufacture complex shapes in difficult-to-cut materials. The constant development of new materials with enhanced properties has sparked the interest in alternative machining technologies. Among these non-conventional machining methods, Abrasive Waterjet Machining is regarded as a flexible technology with potential to cope with a wide range of materials and applications. The use of a soft tool (i.e. the jet) is very advantageous because it makes it possible to perform different operations without modifying the equipment. However, this advantage poses a significant challenge: the erosion power of the jet is controlled through a set of operating parameters, and it is therefore necessary to have a deep understanding of the relation between such parameters and the effect of the jet on the surface. The process itself is subject to strong random variations, and this makes it even more complex to develop a detailed understanding of the optimum strategies to control the jet. The main objective of this thesis is to develop mathematical frameworks that account for the stochastic nature of the process, and that have the capability to predict detailed statistical information of the eroded surfaces for different operating parameters. This is addressed with two modelling approaches: a finite element model where the system is regarded as a set of multiple particles hitting a workpiece at very high speed, and a geometrical model built on the idea of considering the abrasive waterjet as a generic energy beam and exploiting the geometrical properties of the system. In the Finite Element approach, a modelling framework with the capability of predicting the average shape of abrasive waterjet machined footprints and the variability along the trench has been developed for the first time. This is achieved by combining finite element analysis and Monte Carlo methods, and the model is validated at different feed speeds and tilt angles. The random nature of the system is included by considering the input parameters (i.e. size, relative orientation, or position within the jet of the abrasive particles) as random variables with associated probability distributions. The geometrical approach is a method to predict the variability of the jet footprint for different jet feed speeds. Since the objective is to incorporate the stochastic nature of the system in the model, a stochastic partial differential equation is used to describe the machined surface as the jet is moved over it. This framework is greatly advantageous because it can be used to make fast predictions of the variability of the trench profiles (to within < 8%), and it can therefore be implemented into CAD/CAM packages. The modelling work, focused on the understanding of how the operating parameters changes the effect of the jet on the surface, is accompanied by an experimental study to uncover how the material properties of the workpiece will affect the erosion process. This is carried out by machining trenches on model materials (i.e. materials with the same chemical composition, but different grain size), and performing and in-depth analysis of the material response, which shows how the machining process has a strong impact on the microstructure of the target material. The work developed in this thesis contributes to the understanding of the erosion process during abrasive waterjet machining and how stochastic methods can be used to enhance the current capabilities of this technology.

The control of cutting tools within a large-scale manufacturing environment has been studied and a routing through a 'linked' tool control system designed and implemented. Previous contributions in the field of cutting tool control have focused upon a number of specialist areas, and these can be divided into three broad categories:- (a) At the point of application upon individual machine tools. (b) The tool planning element within Process Planning systems. (c) Tool material supply systems. However, in terms of viewing the problem of tool control from a Manufacturing Systems perspective, i.e. the study of the 'whole' system, then this particular subject area has been neglected. A claim to originality is made with respect to the contents of this thesis which consider the interactive nature of the essential control disciplines inherent in (a), (b) and (c) and these are then linked together within a single tool control system framework. Applying this linked systems approach to one tooling family (indexable inserts) within a factory embracing jobbing, batch and flow line production systems resulted in the achievement of a package of economic benefits which included significant reductions in related inventory levels, expenditure, labour content, and through Improvements in the utilisation and output of selected machine tools.

An extensive literature on parameter identification and design of multi-input multi-output control systems exists. Despite this and the presence of a wide ranging software in these areas of control engineering, there is an absence of analytical work and algorithms which are able to treat continuous linear and non-linear as well as discrete systems within the same mathematical framework. Furthermore, virtually all currently available identification and design algorithms require large processing power/working storage and, consequently are suitable only to users with access to mainframe computers. This thesis is concerned with the development of a number of novel mathematical theories for parameter identification and design of linear and non-linear systems. These theories and their associated results are used to develop numerical algorithms suitable for implementation on low-cost personal computers with memory sizes of around 256 kbytes. The programs described in the thesis have been written by using IBM—4331 Fortran and can be run with little modification on IBM—PC Although there are constraints on accuracy, the analytical results and the associated software developed in this thesis would be of use to practising control engineers in the preliminary analysis/ design of physical systems. The thesis is divided into two parts : Part I ( Chapters 1—5 ) considers the problems of parameter identification of continuous linear time - invariant as well as non-linear and time-varying and discrete systems. Part II (Chapters 6 and 7) considers the problems of designing digital servo systems. The main contributions of this thesis are: 1. Development of a new algorithm for the identification of the parameters of multi-input multi-output known order linear systems. This method is based on the integration of the completely controllable dynamical equation (Chapter 2). 2. Formulation of a novel method to identify the system order and the unknown parameters of multiple-input multiple-output linear time-invariant continuous systems. This method is based on the special structure of the system matrix and multiple integration of the dynamical equation C x(t)=Ax(t) + Bji(t) and ^(t)=C x(t) ) (Chapter 3). In Chapter 4, these results are extended to time-varying and non-linear systems. 3. Identification of system parameters and order for linear discrete single-input single-output systems using the rank difference between two matrices constructed from the input- output measurement (Chapter 5) . The procedure used to identify unknown parameters is based on a special output data vector y (K ; N) which is a linear combination of the input -output data The originality of the results presented in Chapters 2 — 5 lies in the fact that linear and non-linear as well as continuous and discrete systems may be identified by using a single mathematical framework. The main advantage of this is that a self-contained system package can be developed. Various parts of such a system software have been described in the thesis. 4. A microprocessor-based output deadbeat controller for digital servo systems with finite settling time is presented. The controller configuration introduced in this chapter can also be applied to implement the widely used digital lead-lag compensators and PID controllers (Chapter 6). 5. Anew method of designing digital systems using the parameter optimization method via non-linear programming and the finite-settling time criterion (Chapter 7).

This research study aims to manufacture and characterise the properties of sandwich structures based on natural fibre composites. Bamboo tubes and flax-based composite (reinforced polypropylene and polylactide) were selected as the main materials to be investigated. Initial testing was focused on investigating the sensitivity of the tensile properties of the composites from various processing conditions and understanding the energy-absorbing characteristics of the individual bamboo tubes. Following this, bamboo honeycomb, bamboo-reinforced foam, corrugated flax-based composites, square and triangular interlocking flax-based composites and corrugated paperboard with flax-based composite skins were manufactured. The flax-based honeycomb and corrugated structures were manufactured using compression moulding techniques and subsequently bonded to skins based on the same material using an epoxy resin. These structures were tested in compression at quasi-static and dynamic rates of strain in order to determine their mechanical strength and specific energy absorption characteristics. It has been shown that the energy-absorbing capacity of the bamboo tubes tends to increase with decreasing inner diameter to the thickness (D/t) ratio. In addition, a chamfered profile was employed to successfully trigger the tubes to fail in a progressive manner. Bamboo tubing has been observed to offer excellent energy absorption characteristics and has potential for use inenergy-absorbing engineering applications. Tests on the flax-based composite structures have shown that the wall thickness and the number of unit cells have an effect on the strength and energy-absorbing capability of the core. The flax reinforcedpolypropylene (flax/PP) composite structures failed in buckling and fibre fracture, whereasthe flax reinforced polylactide (flax/PLA) systemfailed in buckling with delamination. Of the structures investigated here, the flax/PP cores offer superior mechanical properties to their flax/PLA counterparts. Further investigations on the effect of bonding flax/PP and flax/PLA skins to a corrugated paperboard have show that there is no significant difference in the properties between those two flax-based materials. Finally, the compression response of the square and triangular honeycomb structures has been modelled using finite element (FE) techniques. The FE model succesfully predicted the strength, energy-absorbing characteristics, buckling behaviour and failure modes observed in these natural fibre based core materials.

Recent years have witnessed the expansion of the wind power industry, spawned from international legislation that commits countries to increasing their share of renewable energy, compared to their gross energy consumption. However, increased exploitation of wind power poses challenges for power network operation. The variability and uncertainty of wind power may lead to network capacity constraints, system stability issues and potential wind power curtailment in the near future. Energy storage is considered to be one of the most viable options to support the integration of increased wind power to the power network. This project is concerned with developing a hybrid wind turbine with intrinsic compressed air energy storage provision, so that the power output of a wind turbine can be controlled, thus providing flexibility. The proposed hybrid wind turbine makes use of compressed air energy storage on a turbine level. An efficient power split device in the form of a planetary gear box is designed to couple a horizontal axis wind turbine with a scroll air expander/compressor machine, i.e. a single device that can swap its operation, and a permanent magnet synchronous generator/motor. The hybrid wind turbine can operate in conventional standalone fashion. In addition, power can be added and taken away to/from the system through the expansion and compression mode. The hybrid wind turbine also offers standalone energy storage provision, so that power can be extracted from the grid and returned at later times. The whole system mathematical model is derived and successfully validated by means of a small scale experimental test rig. Equipped with feedback control, the hybrid wind turbine can smooth the generated power output under varying wind speeds. Following this, efficiency analysis is carried out in this thesis and a feasibility study on a 1MW hybrid wind turbine is conducted. The results obtained from the project demonstrate that the proposed hybrid wind turbine system is feasible and that it can help improve the wind turbine efficiency in addition to smoothing the power output. Therefore, it can be a valuable asset for wind power integration into the power network.

As key mechanical components, bearings and gearboxes are employed in most machines. To maintain efficient and safe operations in modern industries, their condition monitoring has received massive attention in recent years. This thesis focuses on the improvement of signal processing approaches to enhance the performance of vibration based monitoring techniques taking into account various data mechanisms and their associated periodic, impulsive, modulating, nonlinear coupling characteristics along with noise contamination. Through in-depth modelling, extensive simulations and experimental verifications upon different and combined faults that often occur in the bearings and gears of representative industrial gearbox systems, the thesis has made following main conclusions in acquiring accurate diagnostic information based on improved signal processing techniques: 1) Among a wide range of advanced approaches investigated, such as adaptive line enhancer (ALE), wavelet transforms, time synchronous averaging (TSA), Kurtogram analysis, and bispectrum representations, the modulation signal bispectrum based sideband estimator (MSB-SE) is regarded as the most powerful tool to enhance the periodic fault signatures as it has the unique property of simultaneous demodulation and noise reduction along with ease of implementation. 2) The proposed MSB-SE based robust detector can achieve optimal band selection and envelope spectrum analysis simultaneously and show more reliable results for bearing fault detection and diagnosis, compared with the popular Kurtogram analysis which highlights too much on localised impulses. 3) The proposed residual sideband analysis yields accurate and consistent diagnostic results of planetary gearboxes across wide operating conditions. This is because that the residual sidebands are much less influenced by inherent gear errors and can be enhanced by MSB analysis. 4) Combined faults in bearings and gears can be detected and separated by MSB analysis. To make the results more reliable, multiple slices of MSB-SE can be averaged to minimise redundant interferences and improve the diagnostic performance.