The central theme of the work undertaken in this thesis involved modelling of diffusion – numerical and microstructural – occurring during high temperature exposure of selected materials and coatings. The materials and coatings and their high temperature treatments included carburization of steel (nonsteady-state diffusion of iron carburized at 950o C after 7.1 hours), a two component Cu-Ni diffusion couple subjected to diffusion anneal at 1054oC for 300 hours, a three component Pt-Ni-Al solid alloy subjected to oxidation and diffusion anneal, Multicomponent Ni -aluminide and Pt-aluminide coatings on MAR M002 subjected to 150 hours of diffusion treatment at temperature 1273K, a Jr and Jr/Pt Low-activity aluminide / MAR M002 system at 1100oC after 100 hours, aluminise coating on low alloy steels at 650oC, Jnnovatial coatings- Ti45Al8Nb coated with Al2Au subjected to air oxidation at 750oC for 1000 hours, and Ti45Al8Nb coated with TiAlCrY subjected to air oxidation at 750oC for 500 hours. Such coatings are being increasingly used to protect materials against high temperature (600-1000oC) degradation by oxidation. The demands for using such coatings have arisen because of the need to increase the efficiency by increasing the operation temperature in many areas of technological applications such as power operation, aero engines, and energy conversion systems and in processing industries. However the one of the major obstacles to use these coatings to prevent high temperature oxidation of materials is the degradation of the coatings due to the coating/substrate interdiffusion. Jnterdiffusion of critical elements from the coating to the substrate will deplete the protective scale forming elements in the coating.

This research work investigates heat transfer through the contact line between a glass mould and plunger in a press forming process. Models are formed and compared with experimental measurements to enable clarification of the glass properties that should be used in the optimisation process and have been suggested in previous research works. Two case of heat transfer are considered in the models firstly the case of both conductive and radiative are present and then the case of radiative (reheat). The models developed during the study are based on one-dimensional heat transfer. The model is based on the period of the formation process starting from the point at which the molten glass is brought into contact with a mould until the time at which the formed glass is inverted. The models are concerned with the changes in temperature profile during this period at both the centre and the surface of the glass depending on the mode of heat transfer considered, the properties of the glass, and the properties of the tooling. The properties of the glass considered in the models include the absorption coefficient, refractive index, heat transfer coefficient, internal and external emissivity, specific heat and conductivity. In the radiation case the modelling results show the internal emissivity has a little effect on the surface temperature while the external emissivity has an effect temperature fall. Modelling of changes in glass thickness and glass absorption coefficient during the reheat stage of the process has been carried out based on white and green glass. Validation of these models has been accomplished by performing experimental work.

The work reported in this thesis details the original research undertaken by the author into the cutting mechanics of wood-working handsaw tooth geometries. The research can be separated into three distinctive sections. The first section is a review of both fundamental and recent literature regarding wood characteristics and machining processes. The second section documents the findings of a cutting process in which a variety of work-piece parameters were evaluated whilst limiting the parameters associated with tooth geometry. The third and final section documents the findings of a cutting process in which a variety of tooth geometry parameters were evaluated whilst limiting work-piece variation. Two separate experimental procedures were developed to carry out the work for sections two and three respectively: The first of these procedures utilised a CNC router machine to perform the controlled cutting action. A single “rip” tooth was attached to the tool holder. The workpiece was constrained to a tri-axis dynamometer which was used to measure the resultant tool forces in the relative X, Y and Z axes. At the same time a universal testing machine was employed to perform mechanical test procedures on a variety of wood species. A predictive cutting force model was developed using the obtained mechanical properties as categorical predictors. The second procedure utilised a shaper machine to perform the controlled cutting action. Three different saw tooth geometries were evaluated for only one variety of wood species. A tri-axis dynamometer was again used to measure the resultant tool forces. The geometric parameters of each tooth were carefully evaluated at using SEM micrographs. A predictive cutting force model using the geometric parameters as categorical predictors was developed. Chip and surface formation was carefully evaluated. For procedure one this involved observation of the chip/surfaces under an optical microscope. For procedure two this involved capturing footage of the cutting process using a high speed camera. The findings of the research show that un-bevelled teeth with orthogonal edges generally yield high cutting forces. However, these teeth are very effective at removing material along the wood grain in a “chisel like” cutting action. Bevelled teeth with sharp lateral edges generally yield low cutting forces. These teeth are well suited to severing the wood fibres perpendicular to the grain in a “knife like” cutting action.

As a result of the significant growth of wind turbines in size, blade load control has become the main challenge for large wind turbines. Many advanced techniques have been investigated aiming at developing control devices to ease blade loading. Individual pitch control system, adaptive blades, trailing edge microtabs, morphing aerofoils, ailerons, trailing edge flaps, and telescopic blades are among these techniques. Most of the above advanced technologies are currently implemented in, or are under investigation to be utilised, for blade load alleviation. The present study aims at investigating the potential benefits of these advanced techniques in enhancing the energy capture capabilities rather than blade load alleviation. To achieve this goal the research is carried out in three directions: (i) development of a simulation software tool suitable for wind turbines utilising nonconventional control systems, (ii) development of a blade design optimisation tool capable of optimising the topology of blades equipped with nonconventional control systems, and (iii) carrying out design optimisation case studies with the objective of power extraction enhancement towards investigating the feasibility of advanced technologies, initially developed for load alleviation of large blades, for power extraction enhancement. Three nonconventional control systems, namely, microtab, trailing edge flap and telescopic blades are investigated. A software tool, AWTSim, is especially developed for aerodynamic simulation of wind turbines utilising blades equipped with microtabs and trailing edge flap as well as telescopic blades. As part of the aerodynamic simulation of these wind turbines, the control system must be also simulated. The simulation of the control system is carried out via solving an optimisation problem which gives the best value for the controlling parameter at each wind turbine run condition. Developing a genetic algorithm optimisation tool which is especially designed for wind turbine blades and integrating it with AWTSim, a design optimisation tool for blades equipped with nonconventional control system is constructed. The design optimisation tool, AWTSimD, is employed to carry out design case studies. The results of design case studies reveal that for constant speed rotors, optimised telescopic blades are more effective than flaps and microtabs in power enhancement. However, in comparison with flap and microtabs, telescopic blades have two disadvantages: (i) complexity in telescopic mechanism and the added weight and (ii) increased blade loading. It is also shown that flaps are more efficient than microtabs, and that the location and the size of flaps are key parameters in design. It is also shown that optimisation of the blade pretwist has a significant influence on the energy extraction enhancement. That is, to gain the maximum benefit of installing flaps and microtabs on blades, the baseline blades must be redesigned.

Heat transfer is one of the main phenomena in many industrial processes and applications such as heat exchangers and power generation. For many years, liquids such as water, oil and ethylene glycol had been used as the heat transfer fluids. These fluids have a poor inherent thermal conductivity. Thus, innovation in developing another generation of heat transfer fluids is required for better efficiency. Nanofluids represent a class of pioneering engineering heat transfer fluids. These fluids are made by dispersing metallic or non-metallic particles with nanometer size in various base fluids. With their predominant thermophysical properties, nanofluids are promising medium for heat transfer enhancement of next generation heat dissipation in many industrial applications. This research is focused on studying the enhancement of heat transfer in wall-bounded flows using nanofluids. The enhancement was investigated numerically by modelling nanofluids using CFD technique. Several configurations were tested with different flow types namely, natural convection in a square cavity, forced convection in a backward facing step and flow in micro-channels. The effect of Brownian motion on the heat transfer performance and fluid flow characteristic was investigated for natural convection flow using various nanofluids with different volume fractions for a range of Raleigh numbers. The results showed that the increase in the volume fraction deteriorates the heat transfer. On the other hand, the increase in Ra number promotes the heat transfer rate. For backward facing step, the effect of the inclination angle of the face step using nanofluid was investigated thoroughly. The increase in the facing step angle was found not preferable from a heat transfer perspective, the results showed that the Nu number decreased by up to 3% when 90o inclination angle is tested compared to 125o inclination angle and this information may be valuable for designing industrial equipment. An empirical effective viscosity model is proposed as part of the study. The model is based on available experimental, numerical and theoretical data. The sensitivity of the model has been rigorously scrutinized for different volume fractions and wide range of temperatures. The results showed that the proposed model is reliable and can be employed for various flow configurations. The proposed model has also been used to predict flow through microchannels of various cross-sectional shapes and area. The effect on friction factor for such channels as well as the heat transfer performance has been thoroughly investigated. It was found from this investigation that most of the heat transfer occurred in the U-bend microchannel took place at the downstream flow and it was higher by up to 40.5% compared to the upstream when 6% volume fraction was tested. Finally, a general purpose test rig was designed and built in the lab to conduct some experimental investigation for a double pipe heat exchanger with nanofluids as a coolant. Four different nanoparticles were purchased and are ready for synthesising the nanofluid using ultrasound bath and magnetic stirrer. The rig is ready for the run and several test runs were conducted using water as the base fluid. Unfortunately, due to certain technical extenuating circumstances, experiments using nanofluids could not be conducted within the time span of the project.

The utilisation of composite materials is increasing across many industries, spurred by the need for weight reduction and improved mechanical properties. This has led to an increase in their machining requirements. Although composites are laid in near-net shape, machining processes such as drilling and edge trimming are required to give the composites parts their final geometry and functionality. Machining of composites is challenging due to their low machinability and high cost. Numerical modelling presents a valuable tool for cost reduction and better understanding of the machining processes. Most modelling of machining is carried out using the Finite Element Method, which requires significant time in generating the mesh. Meshfree methods present an attractive choice for machining simulations due to their capabilities in modelling large deformations without the need to construct a mesh. This work aims at developing an efficient meshfree model to simulate orthogonal cutting of unidirectional composites. The Element-Free Galerkin (EFG), which is a prominent meshfree method, is used to construct the model using MATLAB. Steady-state and dynamic models are developed and validated against experimental evidence. The models include several novel features in constitutive relations, composites failure and contact modelling. The main outputs of the simulations are cutting forces and chip formation. Good agreement with experiments is achieved in predicting cutting force. However, thrust force is significantly under-estimated, which is noticed in most of the relevant literature. Three phases of orthogonal cutting experiments are carried out to gain better understanding of the cutting process and generate model validation data. Statistical significance of fibre orientation angle, depth of cut, rake angle and cutting speed on cutting forces and surface integrity is established. Furthermore, the effect of fibre volume fraction on cutting forces is investigated. This work showed that the EFG is a viable numerical method to simulate orthogonal cutting. The simple and automated preprocessing and high quality of approximation are the most advantageous features of the developed model.

Classical techniques for mitigating vibration in rotating structures are divided into three main categories viz. careful design and manufacture, correct installation and effective control strategies. The balancing sleeves analysed in this thesis were developed as a ‘semi active’ method of vibration control to improve the state of balance of dynamically unstable coupling shafts. However, the addition of the balancing sleeves affects the natural dynamics of the shaft, and requires a detailed understanding of their characteristics and the impact on the overall shaft dynamics in order to be useful in practice. As a first approximation, the sleeves are initially modelled as part of a full coupling shaft using the Extended Hamilton’s Principle. The simulation studies show that the flexibility of the sleeves have little impact upon the dynamics of the system and can therefore be neglected. However, when compared to results from the use of computational finite element methods with different sleeve lengths, discrepancies are identified. Experimental validation using a purpose built high speed test facility is used to show that the difference is due to the lack of appropriate modelling of sleeve flexibility characteristics. A full system model using finite element methods is therefore devised. More widely, a study of the impact of sleeve lengths shows that the classical definition of a ‘shaft mode’ does not encompass sufficient fidelity to discriminate between modes that are initially considered as being shaft dominated and those that are considered as sleeve dominated mode shapes, and the sharp transition that occurs between the two. It is notable that the transition between the two dominant modal contributors occurs at sleeve lengths that impart a natural frequency that is close to that corresponding to the shaft. It is concluded that the mechanism of passive control via use of the sleeves is a combination of softening due to the added mass of the sleeves and coherence of the individual modes of the shaft and sleeves. In this way, it is shown that the sleeves act in a manner similar to a tuned mass-damper. By appropriate design therefore, use of balancing sleeves offer the opportunity to increase the critical speed margin in practical applications and reduce unwanted lateral vibrations.

Engineers have been designing machines with long, flexible shafts and dealing with consequential vibration problems, caused by shaft imbalance since the beginning of the industrial revolution in the mid 1800’s. Modern machines still employ balancing techniques based on the Influence Coefficient or Modal Balancing methodologies, that were introduced in the 1930’s and 1950’s, respectively. The research presented in this thesis explores fundamental deficiencies of current trim balancing techniques and investigates novel methods of flexible attachment to provide a component of lateral compliance. Further, a new balancing methodology is established which utilizes trim balance induced bending moments to reduce shaft deflection by the application of compensating balancing sleeves. This methodology aims to create encastre simulation by closely matching the said balancing moments to the fixing moments of an equivalent, encastre mounted shaft. It is therefore significantly different to traditional methods which aim to counter-balance points of residual eccentricity by applying trim balance correction, usually at pre-set points, along a shaft. Potential benefits of this methodology are initially determined by analysis of a high-speed, simply supported, plain flexible shaft, with uniform eccentricity which shows that near elimination of the 1st lateral critical speed, (LCS) is possible, thereby allowing safe operation with much reduced LCS margins. Further study of concentrated, residual imbalances provides several new insights into the behaviour of the balancing sleeve concept: 1) a series of concentrated imbalances can be regarded simply as an equivalent level of uniform eccentricity, and balance sleeve compensation is equally applicable to a generalised unbalanced distribution consisting of any number of ii concentrated imbalances, 2) compensation depends on the sum of the applied balancing sleeve moments and can therefore be achieved using a single balancing sleeve (thereby simulating a single encastre shaft), 3) compensation of the 2nd critical speed, and to a lesser extent higher orders, is possible by use of two balancing sleeves, positioned at shaft ends, 4) the concept facilitates on-site commissioning of trim balance which requires a means of adjustment at only one end of the shaft, thereby reducing commissioning time, 5) the Reaction Ratio, RR (simply supported/ encastre) is independent of residual eccentricity, so that the implied benefits resulting from the ratio (possible reductions in the equivalent level of eccentricity) are additional to any balancing procedures undertaken prior to encastre simulation. The analysis shows that equivalent reductions of the order of 1/25th are possible. Experimental measurements from a scaled model of a typical drive coupling employed on an industrial gas turbine package, loaded asymmetrically with a concentrated point of imbalance, support this analysis and confirms the operating mechanism of balancing sleeve compensation and also it’s potential to vastly reduce shaft deflections/ reaction loads.

Solenoid valves play a vital role in many machines and systems. If one of these devices breaks down the whole system can be affected. Because of this importance of valves, it is desirable to observe these parts to detect faults, both when they are occurring and before they can cause serious damage. Among several possible methods of observation (monitoring actuation time, electrical current, fluidic parameters and others) the observation of mechanical vibrations is a well known method of observing mechanical systems which is commonly used for observation of rotating machinery, but which includes several challenges for diagnosis of solenoid valves. This thesis investigates the possibilities and advantages of vibration analysis of fault detection for solenoid valves. New algorithms are developed to automatically segment the overall non- stationary raw data to smaller sections with a higher degree of stationarity. These new segments are interpretable in a mechanical sense and they separate different sources of vibration. Furthermore a new method to detect regions of interest in a spectrum for classification without "a priori knowledge" about the process has been developed. The experiments presented in this thesis give the evidence that these new methods of pre¬processing and feature extraction enable reliable classification results for transient signals as they occur in the vibration of a switching valve.

The growth of the photovoltaic market indicates that in the near future PV electricity generation may rise to a significant power source. As the proportion of electric power generated from PV systems becomes significant, the effect of these sources on transmission and distribution networks must be considered. This research work has investigated suitable representations of the PV resource and the output power of dispersed PV systems to study the effects of large-scale deployment of PV systems on the grid operation. The representation of solar radiation is very important since this dictates the output power of PV systems. In this work, the simple and reliable Markov Transition Matrix (MTM) method was selected to generate synthetic horizontal solar radiation data. A single MTM was developed to generate half-hour horizontal solar radiation data for different locations in the UK. Large-scale inclusion of PV systems in the UK electricity supply is expected to take the form of a large number of small, geographically dispersed building integrated PV systems. The study also developed a detailed PV cluster model to represent these dispersed PV systems. The variation of PV output power may impact the demand and generation balance on the network requiring additional reserve generation to ensure the system security. In this work, the variation of PV output power and the impact on the reserve requirement was analysed for different penetration levels. This is also the first study to analyse the correlation of solar radiation for different locations in the UK in regard to the impact on reserve requirements. Using data from three locations and according to the National Grid Company (NGC) requirements, it was found that PV capacities of 3750 MW could be added to the present network without additional reserve requirements. The additional reserve required is not on the basis of "MW of reserve per MW of PV capacity". Rather it is based on the aggregation of load demand and of PV output from all regions. The reduction in the reserve requirement by forecasting the weather profile of the day was also illustrated. In this case, a PV capacity of 22,500 MW, which can generate a little over 5% of the UK electricity demand, can be added with minimal increase in system cost. Therefore, the variation of PV output power is unlikely to be a threat to the system security.