Transmission error is a measure of the positioning accuracy of a gear system. This has been widely documented in gearing for many years as the source of problems in noise and vibration. It is a result of errors in the contact conditions which affect the driven gear with respect to the rotation of the driver gear. This research aims to present a better understanding of the basic kinematics of worm gear systems by identifying the significant influences which determine the contact conditions. A literature review of existing theory is described which determines the major areas considered in worm gear contact analysis. Formulae are derived which quantify the effect of component parameter variation on contact. An investigation of the design, manufacture, and operating processes is recorded which identifies error sources relative to the theoretical contact condition. A computer program is developed which calculates contact characteristics such as worm and wheel component form, transmission error and contact marking pattern for a given design including any contact error sources. Computer calculations are validated by comparing direct measurements of these characteristics from several manufactured gear sets with synthesised results produced using the design information, machine settings and error sources detected during production. The behaviour of these gear sets during operation under a torque load has been investigated experimentally. Measured transmission error data from a test rig is used to develop a basic model of worm gear deformation under load. This model has been added to the computer program to improve and extend the analysis capability. The test rig has also been used to investigate the effect of initial wear on contact characteristics. The good correlation between calculated and experimental results shows that the characteristics of a worm gear set can be predicted once all elements of the design and manufacture are known. The results also validate the software as a useful design tool for academic and industrial applications. Important conclusions are drawn on design techniques, the manufacturing process, and the effects of operating under load. Further areas of investigation are identified which offer future research an opportunity to expand upon these conclusions.

An aircraft in low-level flight experiences a large increase in lift and a marked reduction in drag, compared with flight at altitude. This phenomenon is termed the 'wing-in-ground' effect. In these circumstances a region of high pressure is created beneath the aerofoil, and a pressure difference is set up between its upper and lower surfaces. A pressure difference is not permitted at the trailing edge and therefore a mechanism must exist, which allows the pressures above and below to adjust themselves to produce a continuous pressure field in the wake. It is the study of this mechanism and its role in the aerodynamics of low-level flight that forms the basis of our investigation

The automotive industry is under expanding legislative pressure to decrease vehicle weight in order to enhance fuel efficiency; and to improve crash performance as well. For this purpose, hot rolled FB590 is a high strength steel (HSS) which can be used in automotive chassis and suspension applications. A major problem affecting mainly car underbodies is the effect of corrosion, often nucleating at sites where stone chipping has damaged protective coatings. Therefore, car components are frequently exposed to aggressive environments as a consequence of aqueous salts from the street coming into contact with affected and unprotected steel. This circumstance significantly decreases both the life and the appearance of the influenced parts, and may result in compromised structural strength leading to catastrophic failure. The main aim of this research is to further the understanding of the effects of simulated operational environments. Fatigue tests were initially carried out on mild steel under tensile loading and two severity-levels of corrosion as preliminary tests. Then a comprehensive programme of fatigue tests was performed on FB590 and its welds under bending and tensile loading and covering the range of environmental conditions experienced in automotive applications. There is no available data for FB590 in terms of fatigue performance in various environments and under bending and tensile loading as well. Additional techniques such as surface profilometry, scanning electron microscopy and so on were added to support the findings. The other aim was to monitor fatigue tests using a combination of Acoustic Emission (AE) and Digital Image Correlation (DIC) to identify the damage mechanisms that occur during failure although there had been limited research in this area. The combination of AE and DIC can provide much useful information to help to distinguish the different AE signals originating from various possible failure mechanisms such as plastic deformation, delamination of corrosion products or DIC paint and crack initiation and propagation. This might be utilized for an effective and powerful approach to monitoring multiple failure mechanisms; this has significant applications in automotive chassis testing. This information can provide a very valuable tool for the purpose of assessing material for automotive designers, which can then be used to decide on appropriate safety factors to avoid over-designing products and in order to ensure reliability and robustness of new products. In addition, the steel industry can also benefit from this research, as these findings can assist in enhancing the products and diminishing the effects of these environments on structural integrity.

The Anti-lock Braking System (ABS) is one of the most important safety features in modern vehicles. It is a device integrating complicated electronic systems, hydraulic systems and mechanical components. It is possible to produce faults in these systems due to extreme vehicle operating conditions, which may lead to the failure of the ABS. However, there has not been an effective mechanism available in current operation and service facilities, which allows the performance of the ABS to be checked on-board or at a service base. This research therefore aims to investigate and develop approaches which allow the ABS systems to be monitored in different ways. As the ABS is a highly integrated system, conventional monitoring methods cannot be applied to it directly. The primary objective of this research is to develop a condition monitoring model for a typical ABS system under different conditions and then to monitor the dynamic characteristics and performance of the ABS according to simulation and experimental results. The Rapid Control Prototype (RCP) technique is used by applying dSpace MicroAutoBoxII on the ABS controller. A full mathematical model has been developed to simulate the ABS system under different conditions and seeded fault conditions. This results in a full understanding of the characteristics of measurable variables such as wheel velocity and vehicle velocity. This work has led to the conclusion that a model-based condition monitoring approach is the method with the most potential for the monitoring of the ABS systems. To overcome inevitable measurement noise and model uncertainties, a Kalman filter (KF) has been designed and evaluated through both simulation data and experimental results. This has been found to have acceptable performance and has subsequently been incorporated into the model-based condition monitoring system. The performance of the model-based condition monitoring system has been evaluated using an ABS test system. The ABS test rig consists of the basic ABS components and also the dSpace MicroAutoBoxII components, together with NI data acquisition equipment. The ABS test rig developed in this research is highly flexible to allow experimental investigations under different fault conditions with different severities. It has demonstrated that the monitoring system can reliably detect different possible faults in the ABS such as speed sensor failure, solenoid valve sticking or stuck, hydraulic fluid leakage and pump efficiency loss. All these faults occur with high possibility according to a systematic failure mode analysis based on that of similar components. Obviously, there is still considerable work which needs to be carried out to adopt this system in industry. For example, interfaces to integrate this new system into existing vehicle electronics should be investigated. In addition, specific fault conditions from different vehicle manufacturers should be simulated to tailor the system to specific vehicles specifically.

The stringent emission laws, the depletion of petroleum reserves and the relation of fuels with politics have forced the world to find alternatives to fossil fuels. Biodiesel is one of the biofuels which is renewable and environmentally friendly and can be used in diesel engines with little or no modifications. For the last two decades, many researchers have reported extensive work on the performance and emission characteristics of engines running with biodiesel during steady state operation. However, there are numbers of knowledge gaps that have been identified which include limited information on biodiesel physio-chemical properties and their effects on combustion behaviour and performance and emission characteristics of the engine. In this study after an exhaustive literature review, the following four research areas have been identified and investigated extensively using available numerical and experimental means. The initial focus was to investigate the most important properties of biodiesel such as density, viscosity and lower heating value using experimental and numerical techniques. The effects of biodiesel blend content on the physical properties were analysed. For each property, prediction models were developed and compared with current models available in literature. New density and viscosity prediction models were developed by considering the combined effect of biodiesel content and temperature. All the empirical models have showed a fair degree of accuracy in estimating the physical properties of biodiesel in comparison to the experimental results. Finally, the effects of density and viscosity on the fuel supply system were investigated. This system includes the fuel filter, fuel pump and the engine combustion chamber in which air-fuel mixing behaviour was studied numerically. These models can be used to understand the effects of changes in the physical properties of the fuel on the fuel supply system. In addition, the fuel supply system analysis can be carried out during the design stage of fuel pump, fuel filter and injection system. The second research objective was the investigation into a CI engine’s combustion characteristics as well as performance and emissions characteristics under both the steady and transient conditions when fuelled with biodiesel blends. The effects of biodiesel content on the CI engine’s in-cylinder pressure, brake specific fuel consumption, thermal efficiency and emissions (CO2, NOx, CO, THC) were evaluated based on experimental results. It has been seen that the CI engine running with the biodiesel resulted in acceptable engine performance as well as reduction in main emissions (except NOx). Following this study, a detailed analysis on the transient performance and emission output of the CI engine has been carried out. During this analysis, the emission changing rate is investigated during speed transient and torque transition stages. Further to this, a transient emission prediction model has been developed using associated steady and transient emission data. The model has been shown to predict the transient emission reasonably accurately. The third research objective was to develop a method for on-line measurement of NOx emission. For this purpose the in-cylinder pressure generated within a CI engine has been measured experimentally along with mass air flow and these parameters have been used in the development of a NOx prediction model. This model has been validated using experimental data obtained from a NOx emission analyzer. The predicted data obtained from NOx prediction model has been compared with measured data and has shown that the deviation is within acceptable range. The final research objective was to develop a simple, reliable and low-cost novel method to reduce the NOx emission of the CI engine when using biodiesel blends. A potential solution to this problem has been found to be in the form of direct water injection which has shown to be capable to reduce NOx emission. Using a water injection technique, the performance and emission(NOx and CO) characteristics of a CI engine fuelled with biodiesel has been investigated at varying water injection flow rates. Intake manifold water injection reduces NOx emission by up to 40% over the entire operating range without compromising the performance characteristics of the CI engine

No description available.

Turbine blades are critical to the performance of an aircraft engine and their life is central to the integrity of the engine. These blades, when manufactured, inevitably exhibit some deviations in shape from the desired design specifications as a result of manufacturing variability. An approach to characterizing these deviations may be made by analysing the blade measurements for any changes from the datum design values. The measurement data, is however, always affected by measurement errors that cloud these effects. In the present study, a methodology is proposed that employs the probabilistic data analysis techniques of Principal Component Analysis (PCA) and Fast Fourier Transform (FFT) analysis for de-noising the measurement data to capture the underlying effects of manufacturing variability as manufacturing drift with time and blade to blade manufacturing error. An approach using dimensionality reduction in the case of PCA and sub-selecting Fourier coeffcients in the case of FFT is proposed that uses prior knowledge on the measurement error. A Free-Form Deformation (FFD) based methodology is then presented for characterizing the 3-dimensional (3-d) geometric variability in blade shapes from the limited number of available measurements. This is followed by the application of a linear elasticity based approach for generating and morphing 3-d volume meshes in FEA ready form. A finite element analysis (FEA) of the resulting probable blade shapes indicates that the presence of manufacturing variability reduces their mean life by about 1.7% relative to the nominal design with a maximum relative reduction in life of around 3.7%. The probabilistic estimates of manufacturing perturbations are employed for robust design studies with the objectives of maximizing the mean and nominal lives and minimizing the blade life variability. A comparison of the robustoptimal solution with an optimal deterministic design is also performed. The designs explored by the multiobjective optimization process are analysed to understand the effects of geometric changes in turbine blades on the nominal values of life and the variations in blade life.

No description available.

Carbon emissions from road transport make up 20% of the total greenhouse gas emissions in the UK. Therefore, reducing carbon emissions from road transport is significant in reaching carbon reduction targets. In urban areas where signal controlled intersections are common, carbon emissions from vehicular traffic can be aggravated by aggressive driving and interruptions induced by traffic control. Considerable variations in speed and acceleration profiles could be observed between high carbon and low carbon driving. In view of the immediate effects that changing driving behaviour could have on carbon emissions without extra cost, this study had investigated the variations in carbon emissions at signalised intersection, which includes the scale of impacts of changing driving behaviour and flow interruption on carbon emissions. Characteristics which lead to high CO2 emissions could then be modified by addressing the behavioural change and control strategies. High frequency real world driving data was collected using the TRG highly instrumented vehicle. The vehicle was equipped with a number of on-board systems, i.e., on-board emission measurement system, velocity box, on-board diagnostic unit, Dashdyno and video recorder. Aggressive and economical driving styles observed for two drivers during initial tests showed distinct differences in terms of speed profiles and fuel consumption. These initial tests were used to examine the nature and scale of potential impacts on fuel consumption and to design main field tests. Natural driving observed from twenty nine drivers from the main field tests also showed significantly different levels of carbon emissions at signalised intersections, which were caused by variations in both driving behaviour and traffic control. In terms of driving behaviour, changing the worst driving to the best driving during interrupted driving was found to reduce CO2 emissions significantly. The carbon reductions were collectively contributed by 1) applying soft acceleration and keeping acceleration below 0.6m/s2 during the acceleration mode and 2) reducing leaving speed at intersections, 3) practising smooth deceleration and stable speed during the deceleration mode and 4) applying the idle-stop system. Carbon emission rates of different vehicles may vary from one to another. However, it was found that the amount of carbon savings demonstrated in this study could be possibly achieved by other internal combustion vehicles of the same class, and by hybrid electric vehicles to a lesser extent. In this study, changing driving behaviour is recommended as a cost effective way to achieve carbon reduction.

Low-frequency Earth-horizontal translational and rotational oscillations can cause motion sickness in transport. Previous studies have found that motion sickness depends on the frequency, magnitude, direction and duration of the motion, however, knowledge of the mechanisms of motion sickness is far from complete. The concept of sensory conflict – that motion sickness arises because of a conflict between sensed and expected sensory information is central to theories of motion sickness, but little is known about how the physical characteristics of motion influence sensed and expected sensory signals. The aim of this research was to advance understanding of the effect on motion sickness of factors which may influence sensed and expected vestibular signals during exposure to low-frequency translational and/or rotational oscillation. The first experiment investigated whether motion sickness depends on the phase between combined lateral acceleration and roll oscillation at 0.2 Hz. The roll oscillation had one of four phases relative to the lateral acceleration: 0° delay, 14.5° delay, 29° delay, and 29° advance. Sickness decreased as the delay in the roll motion increased; less sickness occurred with a phase advance than a phase delay, suggesting that motion sickness cannot be predicted from the acceleration in the plane of the seat. The second experiment investigated how motion sickness varies between four 60-minute exposures of 0.1 Hz combined lateral and roll oscillation which involved different combinations of a high and low magnitude motion: LLLL, HHHH, LHHL and HLHL. The high magnitude motion produced greater sickness than the low magnitude motion. For the two variable motion conditions, there was no significant difference in accumulated illness ratings when the motion sickness dose values were the same. In the third experiment, 0.2 Hz roll and pitch oscillation were studied at three displacements: ±1.83° ±3.66° or ±7.32°. A trend for motion sickness to increase with increasing displacement was observed; similar sickness was caused by roll and pitch oscillation at each magnitude. In the fourth experiment, subject head displacement was measured during 0.2 Hz fore-and-aft oscillation with and without a backrest at three magnitudes: 0.22, 0.44, and 0.89 ms-2 r.m.s. Illness increased systematically with increasing magnitude of oscillation with a backrest, but less systematically without a backrest, suggesting an interaction between the effect of motion magnitude and the influence of a backrest. There were no significant differences in illness with or without a backrest at any of the magnitudes studied. Between subjects, there was little evidence to suggest that greater fore-and-aft and pitch displacement of the head was associated with an increase in motion sickness. Combined findings from the third and fourth experiments suggest that 0.2 Hz fore-and-aft oscillation causes greater sickness than 0.2 Hz pitch oscillation at each of the three magnitudes studied (assuming that pitch motion can be represented by the gravitational component, gSinθ). A motion sickness model is proposed showing how the factors investigated in this thesis affect the sensed and expected semi-circular canal signals which are assumed to be involved in the causation of motion sickness. The model predicts how sensed and expected signals vary according to the phase between motions, the magnitude, direction and duration of motion, the type of motion and the postural support given to subjects. Explanations of how the model predicts motion sickness based on the findings of this study and previous studies are discussed.