Experimental and theoretical studies of the influence of oil supply pressure on the friction torque in plain bearings have been carried out. The focus of the work has been the reduction in bearing friction that might be achieved by reducing oil supply pressure and the mechanisms by which the changes in friction occur, with potential applications to reducing bearing friction in internal combustion engines. A single bearing test rig has been used to investigate the impact of feed oil pressure on the extent of cavitation and the role of increased film cavitation on friction under light, steady loads for a bearing with a 180° groove, using an SAE 5W-30 oil. Film visualization shows that cavitation area increases when the oil feed pressure is reduced and the extent of the full width film reduces primarily as the angle of film reformation is retarded. Both load and speed increases reduce the full width film extent. At constant film viscosity, friction torque was reduced by up to 20% by increased cavitation which reduced the film area and the eccentricity ratio. The latter reduces the surface shear stress in the load-bearing region of the film and overall, the circumferential average. As load increases, the reduction in film area accounts for an increasing proportion of the friction torque reduction. The effect of load, speed, lubricant formulation and clearance on bearing friction and film pressure has been investigated. Increases in load led to increases in friction and peak film pressures with smaller percent reductions in friction torque as the supply pressure was reduced. Bearing friction torque was found to show a linear dependence on oil viscosity in the hydrodynamic regime where friction could be substantially reduced by using low viscosity oils. The effect of increased clearance was to reduce bearing friction and increase peak film pressures. The effects of reduced oil supply pressure on friction in crankshaft main bearings during cold-start warm-ups have been investigated. Friction reductions have been found to be most significant during cold running conditions at light loads. The thermal coupling between the bearing films and engine structure influences the film warm-up. Initially there is a rapid rise in film temperatures after which the warm-up is held back by the temperature of the surrounding metal. In addition to reducing bearing friction, reducing oil supply pressure also reduces the oil pumping work required; this represents an additional benefit which can be particularly significant under cold operating conditions.

The surface of diamond grinding tool manufactured by current production method exhibits stochastic nature in terms of different grit size, irregular geometry, random crystallinegraphic orientation, non-uniform spacing, and varying protrusion heights. These topography characteristics has been found having various negative effects for the abrasive performance, especially in high-precision applications, causing less controllable surface topography, inefficient chip flow, high working temperature and cutting force. The thesis covers the design and manufacture of laser generated novel abrasive pad with ordered abrasive grits from CVD polycrystalline diamond films, providing repeatable patterns and shapes for abrasive tool used in load controlled plane grinding process, which is regarded as engineered abrasive pad. Two major design parameters for engineered abrasive pad, including abrasive grit geometry and planar contact area between grits and workpiece surface, were investigated. An inverted test setup was developed to enable the evaluation for the performance of ordered abrasive pad under plane grinding operation. The analysis of material removal and surface topography was made and compared between conventional abrasive pad (randomly shaped grits) and two engineered abrasive pad (saw tooth and square frustum) to evaluate the influence of grit geometry on the grinding performance. Furthermore, a geometrical model was developed to simulate the surface roughness generated by engineered abrasive pad. Inverted tests were conducted allowing the validation of the model. Besides grit geometry, three abrasive pads (one conventional, two engineered) with different planar contact were also studied through inverted grinding test to evaluate the influence of planar contact area on grinding performance. An improvement of design for better material removal (31.5% in Chapter 7) was achieved by adjusting the planar contact area of engineered abrasive pad. It was found that laser generated abrasive pad can provide not the only superior surface finish, but also introduce less damage to the workpiece surface. More efficient chip flow and very little tool wear leading to a longer tool life was also observed. In particular, the engineered grits with symmetric shape (square frustum) exhibits superior performance over conventional grits (randomly shaped) and asymmetric grits (saw tooth). A good agreement between simulation and experimental results was found for surface roughness prediction, therefore provide good initial results for numerically studying engineered abrasives under planetary abrasive machining processes. Moreover, the evaluation of planar contact area also shows laser generated abrasives can provide significant advantages in material removal when designed with comparable planar contact area as conventional abrasive pad under specific applications, particularly when the abrasive contact geometry is designed to provide clearance in the cutting directions. Combining the findings above, a preliminary benchmark methodology was proposed for design of engineered abrasive pad, which enables the future optimization of engineered abrasive tool.

Energy use in buildings accounts for a large portion of global and regional energy demand and energy-related CO2 emissions. To steer the world towards a low carbon future, the development of new and more efficient technologies is required. In hot and humid climates, the high latent heat loads results in uncomfortable and unhealthy indoor environments, accounting for 30% to 50% of standard air conditioning energy requirements. Physical adsorption of water vapour on solid desiccants is found to offer an energy efficient alternative to conventional dehumidification process using standard air conditioning systems. However, the isosteric heat of adsorption released increases the surface vapour pressure of the solid desiccants resulting in a decreased adsorption capacity. In packed beds of solid desiccants, this heat of adsorption increases the bed temperature, exit air temperature and exit air humidity ratio subsequently imposing an increased cooling load requirement and high energy requirement in the regeneration of the solid desiccants. In literature, several approaches used in removing in situ the heat of adsorption released in packed bed systems were fraught with several limitations. To this end, an integrated packed bed-oscillating heat pipe (OHP) system was proposed. The concept was for the evaporator of the OHP to remove the heat of adsorption generated by the packed bed and reject at its condenser towards an energy efficient isothermal adsorption process. To achieve this, theoretical investigations of the individual systems and the integrated systems preceded experimental testing of a rig set up in the laboratory. For the theoretical studies, the OHP was helically coiled at both ends, filled with ethanol, methanol and water working fluids respectively at 50% volume fraction and numerically investigated using the Eulerian Volume of Fluid (VOF) model in ANSYS Fluent R15.0. The packed bed on the other hand was configured as a Heggs et al (1994) Z-type flow arrangement for enhanced radial flow using the Porous Media model in ANSYS Fluent R15.0 set up with the properties of Silica Gel. ANSYS Fluent R15.0 System Coupling limitations led to the development of mathematical models for the prediction of the integrated system performance. The experimental investigations were in line with the theoretical only in this case the optimum working fluid, deionized water, was used as the main working fluid in the helically coiled OHP (HCOHP). The results showed reasonable agreement between the performance of the numerical model and experimental prototype. The HCOHPs were capable of passively removing heat from the packed bed systems. Mean bed temperature reduction between the integrated packed bed-HCOHP system and corresponding individual packed bed configurations were about 5.61°C, 9.48°C and 10.14°C respectively for the large annulus (LAPB), medium annulus (MAPB) and small annulus (SAPB) packed bed configurations. Average packed bed outlet temperature reductions of about 6.61°C, 9.19°C and 6.29°C were also achieved for the respective configurations. A validation of the theoretical model showed average temperature difference of about 5.60°C between the experimental prototype of the integrated system and results predicted using experimental packed bed temperature data and HCOHP thermal resistance. Compared to other similar systems in literature, the integrated packed bed-HCOHP system showed capacity to passively remove significant amounts of the heat of adsorption released in silica gel packed beds towards isothermal adsorption.

The current design for a salient pole rotor consists of hundreds of laminations joined together to form a core pack, which is then pressed onto shaft. This thesis examines the possibility of using a solid cast rotor to reduce the complexity of rotor construction. To produce a solid salient pole rotor that has the capability to match the performance of the current lamination based rotor three fundamental areas which affect rotor performance were investigated. They are: • The magnetic performance of cast steel and a lower saturation Fe-Ni alloy for the magnetic shielding of pole faces. • The comparison of the performance of a solid steel rotor verses the lamination based rotor. • The use of laser cladding to produce a soft magnetic coating to prevent eddy currents from being induced into the rotor. Samples of cast steel were tested after various heat treatments were applied and their DC B-H curves were measured. The samples were examined, via optical microscopy, to determine the effect of heat treatments on their microstructure. The changes in their B-H curves and permeability were linked to the changes in microstructure by examination of the optical images. A prototype of a solid rotor was produced to determine its performance compared with the lamination based rotor. The prototype rotor was produced with a Fe-Ni alloy on the rotor pole faces. The prototype rotor was found to require an average of 72% more power in the field windings to match the performance of the lamination based rotor. This was true until the generator’s output reached 72kW when the Fe-Ni alloy on the rotor pole faces saturated, resulting in the air gap between the rotor and stator increasing from 2mm to 34.5mm. After the increase in air gap the prototype rotor required an average of 188% more power to match the lamination based rotor. The point at which the Fe-Ni alloy saturates is critical, as once saturated the power in the field windings must increase sharply to bridge the larger air gap. From this work it is clear that a cast steel with a better magnetic performance is required and that the point at which the lower saturation material on the pole shoes saturates needs to more closely match the normal operating power of the generator. Laser cladding was used to produce a coating that can be applied to the pole faces, with a sufficient thickness to allow a controllable increase in the air gap between the rotor and the stator at predetermined field strengths. The use of laser cladding in this way enables the pole face to act as a magnetic shield stopping heating in the rotor due to induced eddy currents. The use of annealing in both inert and reactive atmospheres was examined to determine their effect on the DC magnetic properties of the deposited coating. Annealing in an inert atmosphere of argon was found to improve the saturation magnetisation of the coating 30% better than annealing in a reactive hydrogen atmosphere.

The parametric studies investigated the cavitation phenomena occurring in Diesel Fuel Injection Equipment using immersed jets. The studies looked at cavitation from the incipient stage, to the fully developed stage, to leaving the fuel to cavitate for a sustained period of time. The studies were conducted with the aim of understanding the cavitation phenomena occurring inside the Fuel Injection Equipment making use of purposed built continuous flow rigs. The first part investigated the onset of cavitation taking place inside a mechanical 80 bar continuous recirculated flow rig that mimicked the flow inside the injectors spill valves as well as the flow inside the high-pressure pumps spill valves during the first stages of cavitation. High velocity jets of variable concentration were considered, from the incipient stage to the fully developed stage, focusing on the impact that changing the fuel composition has on the jets as well as on the impact it has on the geometrical parameters of the nozzle valves. The rig made use of custom made Acrylic, Brass and Aluminum-steel nozzles of Cylindrical, Hemispherical and Conical geometries respectively. The n-Octane, n-Decane, n-Dodecane, n-Tetradecane and n-Hexadecane mixtures were directed into an optically accessible receiver using single hole injector nozzles of 0.14mm and 0.25 mm hole diameters respectively. Parameters such as the fuel composition, the geometry and the material of the nozzles, as well as the operating conditions of the fuels were looked into where 25 repetitive sets of measurements were completed taking into consideration each parameter respectively. Incipient cavitation was associated with the flow outside of the nozzle and was visually observed at the top of the nozzle hole. Cavitation additionally occurred between the layers of the turbulent high immersed jet flow and the stagnant fluid inside the receiver. The onset of cavitation was obtained using the fuel Upstream Pressure to Downstream Pressure ratio. At the point of onset, the results showed that the Upstream Pressure to Downstream Pressure ratio decreased with the increase of n-Octane percentage in the mixture when considering the Cylindrical and the Hemispherical nozzles. When considering the Conical nozzle on the other hand, the critical Upstream Pressure to Downstream Pressure ratio increased with the increase of n-Octane concentration. The results also showed that the jet length and width increased when varying the diameter of the nozzle hole from 0.14 mm to 0.25 mm. Furthermore, the total Saturated Vapour Pressure increased with the increase in n-Octane concentration, where the increase in the propensity of the flowing fuel through the Cylindrical and Hemispherical nozzles, to cavitate was noted. On the other hand, the propensity of the Conical nozzles to cavitate decreased with the increase in Saturated Vapour Pressure. The second part of the study investigated the sustained hydrodynamic cavitation taking place inside a mechanical 1650 bar continuous recirculated flow rig, mimicking the flow inside the injectors spill valves and high-pressure pumps spill valves at a later stage of cavitation as the fuel was left to cavitate for a longer period of time, leading to the degradation of the fuel due to changes in the fuel’s chemical composition taking place during cavitation. A needleless 0.213 mm single hole diameter Cylindrical nozzle was considered, as the Commercial Diesel fuel, the biofuel Rape Methyl Ester and the Gas to Liquids paraffin blend were left consecutively to cavitate for a period of 30 hours. The volume flow rate was obtained as 1.129 Liter per minutes considering a Discharge Coefficient of 0.8. The results showed that by passing a 405nm laser over the 30 hours period through the cavitated fuel mixtures, a decrease with time of the transmission signal of the laser beam penetrating all tested fuels respectively was noticed. The laser beams experienced a decrease in strength due to the changes in the chemical composition of the fuel as high pressures and high temperatures took place inside the receiver. The effect of heating the fuels overnight inside a modified Water Bath tea urn at 60 degrees Celsius was looked into in order to separate the impact of temperature to the impact of cavitation alone. The effect of subjecting to fuel to cavitation and heating was greater than the effect of subjecting the fuel to heating alone. The Gas to Liquids fuel was visually transparent compared to the commercial Diesel fuel and had the highest laser transmission signal. Of all three fuels, the Commercial Aged Diesel fuel had the lowest laser transmission signal as the impurities inside the fuel changed the chemical composition of the fuel due to sustained hydrodynamic cavitation.

Margins in defect assessment procedures such as BS 7910 and R6/4 have been examined for cleavage and ductile tearing from complex and re-characterised defects. A range of crack profiles with re-entrant sectors developed from two co-planar surface breaking defects by fatigue has been examined experimentally and numerically. Both studies show enhanced crack driving forces in the re-entrant sector combined with a loss of crack tip constraint. Cleavage failures from complex and re-characterised defects demonstrated that the re-characterisation procedure is not conservative when cleavage occurs at small fractions of the limit load. Failures close to the limit load benefit from constraint loss which counteract the amplified crack driving forces in re-entrant sectors and cause re-characterised defects to be more detrimental than the original complex defects. Benefit may be taken from statistical size effects, which are strongly dependent on the crack geometry. Experimental fatigue and ductile tearing studies show similar development of complex cracks towards the re-characterised shape and re-characterisation procedures, such as those given in BS 7910 and R6/4, are conservative for fatigue and ductile tearing. A procedure has been developed to quantify enhanced temperature margins due to constraint loss by comparing the self similar stress fields at a critical local fracture stress (the Ritchie-Knott-Rice approach) and through the Weibull stress. Agreement with the experimental data has been demonstrated and the temperature dependence of the material parameters has been discussed. Following Li (1997) and Karstensen (1996), a toughness mapping technique was discussed that allows mode I toughness to be translated into mixed-mode I+II toughness for stress controlled fracture. In support of the arguments, toughness of Mode I and mixed-mode I+II configurations was measured on a mild steel. The experimental data clearly show increased cleavage toughness for unconstrained mode I and mixed-mode fields and the correlation with the predictions from the numerical models was demonstrated.

The laser heated pedestal growth technique has been successfully employed to grow pure and doped sapphire crystal fibres for characterisation as suitable sensor materials. Source materials used were polycrystalline and crystalline sapphire rods while fibres with typical diameters in the range 80 - 170 mm were grown. Pure sapphire fibres, both a- and c-axis, were found to grow easily with no complications such as melt instability. C-axis fibre growth was readily initiated while a-axis fibres required an appropriate a-axis oriented seed crystal. Dip-coating has been used to prepare suitably coated sapphire source rods for growth into doped fibres. Doped fibres grown included Cr3+:, Er3+:, Er3+:Yb3+: and Yb3+:Er3+:Al2O3. Er3+:Yb3+:Al2O3 fibres have been prepared with approximately equal concentration of both dopants while a 10:1 Yb3+ to Er3+ concentration ratio was used for preparing Yb3+:Er3+:Al2O3 fibres. Ruby fibres were also found to grow easily although brownish-green deposits have been observed on some of these fibres. Large transmission losses have been found in fibres with these deposits. Acid cleaning was not effective in removing these deposits, suggesting that they have diffused beneath the surface of the fibres. This was attributed to the condensation of chromium oxide on the fibre surface during growth. Growth of rare earth-doped fibres was initially problematic due to the constant breaking-off of the crystallising fibres from the melt. This was thought to be due to the flexibility of the small diameter source fibres used as well as the high concentration levels of doping. Replacing these small fibres with larger source rods thus permitted RE-doped fibres with relatively good optical quality to be grown. Fibres were grown with typical growth rates of 0.5 - 1 mm/min.

Cold Plasma Discharges offer wide decontamination scenarios relevant to environmental, food and drink or clean room applications. The option to operate the discharge system in atmospheric or sub-atmospheric condition provides an opportunity to investigate a lowcost and simple system design. UV to NIR (200nm to 700nm) can be emitted by pulsed cold plasma discharge systems that operate at atmospheric pressure. Different wavelengths emitted from the discharge depend on the pressure and the type of gas mix used in the systems. The scope of the work involved in this research was to design and develop a prototype cold plasma system for air at atmospheric pressure. The prototype was used for air decontamination by passing seeded and unseeded air between the electrodes gap. Modelling of the discharge and pulse forming network circuit systems was carried out in MultiSim to investigate the circuit characteristic. The components values ie: capacitors, stray inductors and resistors in the model system are interchangeable which enabled simulation of individual component effects on the output pulse shape and magnitude. The optimum component properties from the modelling were used as a guide to designing the system. The main discharge system contained a pair of Chang Uniform Field Electrodes which were manufactured in-house, and provided a discharge area of 1.0cm x 60.0 cm. The discharge volume is varied depending on the gap between of the anode and cathode. Preionisation was achieved via trigger wire, built within the discharge system. This promotes the ionisation of the gas in between the electrodes in enhancing uniform discharge characteristics. Different types of electrodes were made from aluminium with the discharge size 300mm x 200mm, laser marked and unmarked surface were also used in the system in order to obtain wider discharge surface and reduce manufacturing costs.

The context of this thesis surrounds the development and study of the effectiveness of three mechanical-to-electrical energy converter concepts that are based upon oscillatory systems with a view of discovering techniques to enhance their normal functioning throughputs. The field of energy harvesting has experienced significant growth over recent years with the increased popularity of portable electronic devices and wireless sensors. However, with demand, so too rises the need for increased operating lifetimes not only for extended use for some personal devices, but also to reduce the frequency of periodic battery replacements for remote sensors that may be deployed in potentially hazardous environments. In light of this need, the proceeding chapters will discuss the development of three conceptual energy harvesters. The first is based upon a simple Euler strut that is intended to harvest known steady-state periodic vibrations applied axially to the beam. The assumption here is that the periodic vibrations would arise from ambient conditions, whether naturally occurring or as a form of waste energy from man-made structures. This concept has built into it the facility to apply a static axial pre-load with which, it will be shown, can be used to passively enhance the energy throughput of the device. However, it will also be shown that the periodic concept has an inherent sensitivity to excitation frequencies, where even minor shifts can result in significantly reduce outputs. To this end, the second harvester was proposed to relieve this limitation by instead harvesting stochastic inputs. With this in mind, the new concept is again based upon a simple and realisable Euler strut but with the stochastic input applied laterally to the supporting structure. By retaining the facility to apply both static and dynamic axial loads, it will be shown that the cumulative effects of the deterministic and stochastic input can be manipulated to actively enhance the throughput of this system also. However, given the active nature of this form of control that will consume work during its implementation, an approach for ensuring that the net energy will be reduced by this additional work will be discussed. In this way, a conservative estimate of the harvestable energy may be made. The final energy harvester to be discussed is based upon a planar pendulum that can integrate mechanical accelerations out of the full three degrees of freedom realisable by planar constructs. This begins with the development of a suitable approach to applying rotational excitations to the device, followed by the development of a set of loading terms used to represent the resistive torque that would be exerted upon the system by a suitable power take-off device. This is followed by a comprehensive parameter study of the proposed concept with a mindset towards optimising the operational performance of the device.

Total knee replacement is effective at reducing pain resulting from end stage knee osteoarthritis but patient clinical outcome remains poor. This study develops methodologies for the assessment and classification of knee function to further the understanding of the mechanical effects of osteoarthritis, identify targets for treatment and objectively evaluate patient functional recovery. This study additionally develops methodologies to investigate how internal knee structures function during dynamic in-vivo activities using novel approaches to MRI. The uncertainties in the assessment of patients’ knee function were first investigated. Stair gait analysis was investigated to complement traditional level gait analysis. Measurements with the force plate interacting with step one displayed lowest inter-subject variability and were carried forwards to patient assessments. The level and stair gait of three age groups of healthy volunteers was investigated to select a healthy control group. A trend of peak sagittal moments at the hip, knee and ankle all decreasing with aging and frontal plane joint moments at the hip and ankle increase with aging was found. Age related changes were non-linear becoming more prominent towards old age. Young and middle aged healthy volunteers were combined to form a larger, homogenous cohort for patient comparisons. Inter-subject variability is neither helped nor hindered by the inclusion stair gait analysis when compared to level gait ensuring no adverse affects in distinguishing functional changes from naturally occurring individual variation. Patient completion of stair gait was unfortunately very poor however and the practicalities of stair gait in the patient population were found to be preventative. The accuracy of using principal component analysis over traditional parameterisation to classify osteoarthritic or healthy knee function was found to improve classification accuracy when using the Cardiff Dempster Shafer Theory Classifier. Knee measures were found to have poor classification accuracy with hip and ankle adaptations best discriminating healthy and patient gait. The adaptations to lower limb biomechanics observed in older healthy adults appear to become magnified with osteoarthritis. The classification methodology developed throughout the study resulted in an in and out of sample classification accuracy of 97.9% in determining osteoarthritic or healthy knee function. The hip, knee, ankle and ground reaction force biomechanical data of 12 patients before total knee replacement and one year post surgery were assessed using principal component analysis and the Cardiff Demspter Shafer Classifier. 42% of patients experience no functional benefit and 25% of patients recovered lower limb function characteristic of young and middle aged healthy volunteers. Classification of total knee replacement outcome was found to correlate with clinical outcome measures but implant type, BMI, weight loss and presence of comorbidities were poor indicators of patient outcome. Patient age and pre surgery function were found to correlate to the function observed post surgery, indicating that the earlier timing of intervention (and visualisation of this using the classification methodology) may improve functional and clinical outcome of patients with end stage knee arthritis. Novel, high resolution MR imaging and analysis techniques to quantify 3D, patient specific, invivo menisco-tibial kinematics and meniscus shape change were created. Repeatability was high with largest errors due to MRI image quality. Posterior translations of both menisci were found with increasing knee flexion angle and large meniscus translations, as much as 3.4mm in the anterior-posterior direction and 4mm in the medial-lateral direction were observed with changing transverse plane knee joint rotations. Load bearing introduced substantial additional posterior motion of both menisci, up to 4.6mm (medial meniscus) and 5.2mm (lateral meniscus) in the flexed knee. Large variability was observed between subjects suggesting patient specific response to load bearing is an important consideration in the treatment and rehabilitation of soft tissue injuries and prevention of early onset arthritis. Flexion of the knee was found to introduce compression in the menisci while loading contributed greatest posterior translation of both menisci. The posterior horns of both menisci were also found to rotate towards the centre of the tibial plateau during flexion and maintaining this during treatment of soft tissue injuries may aid the prevention of secondary pathologies.