There has been a recent revival of interest in the design of fast-acting solenoid actuators. This is due to the emergence of new control applications in the automotive industry constrained by tighter emission and noise regulations. In the context of developing a rapid computer-aided design tool for such applications, the thesis proposes several methods for computing the static and dynamic electromagnetic performance of solenoid actuators with a particular attention given to two actuator types : an axisymmetric and a rectangular solenoid actuator with a flat-faced armature. The magnetostatic performance of both actuator types is first evaluated by developing a detailed magnetic equivalent circuit in which the actuator geometry, saturation and end-effects are all taken into account. A comparison of the analytical model, based on the computation of the magnetisation characteristics and static forces for several airgap lengths, is given with finite-elements and measurements. In order to increase the computational speed of the static performance, the concept of magnetic gauge curve is presented. It is shown that this approach is in principle valid for any type of variable reluctance machine. Although the complexity of the gauge curve expression varies significantly from one device to another, it is shown that this method is an efficient way to store the magnetic data for a rapid computer aided-design or a real time application. When applied to the two previous types of solenoid actuator, it also leads to a very fast and accurate static force computation. The dynamic performance of the solid iron actuators requires the evaluation of the magnetic damping due to eddy currents. Based on a ID model of the flux and eddy current diffusion within an iron bar, an electromagnetic equivalent circuit of the axisymmetric is derived, in which the material nonlinearity, armature movement and eddy currents, a function of the previous parameters, actuator geometry and driving conditions, are modelled. A dynamic model of the partly solid iron rectangular actuator is also proposed and evaluated. In both cases a comparison of the transient current and force waveforms with 2D or 3D finite elements and measurements is given under various driving conditions.

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This thesis encompasses the analysis of TSN systems and their multi-objective design methods. TSN nodes are networked through interpolation and activation, similar to a gain-scheduling or local model/controller network. However, to achieve accuracy and ease of commissioning without requiring a large number of nodes, an algorithm has been developed first to identify optimum transition nodes within the entire operating envelope. Then the TSN approaches a nonlinear plant globally, not just locally, without requiring linearization. If desired or necessary, global optimisation provides an enhancement in the design process for TSNs. Since optimising only one aspect (a single objective) of performance while compromising others is undesirable, multi-objective designs have been developed concurrently to deliver or improve multiple aspects of performance. Following the development of a TSN, it is applied to nonlinear system modelling, and this TSN is termed a Trajectory-Scheduling Model (TSM). A TSM possesses the same properties and design features as the TSN generic framework. A nonlinear system, a coupled liquid-tank, is used to examine this modelling technique. Results verify the feasibility and effectiveness of the methods developed and validates the TSM. Further, the TSN technique is applied to nonlinear controller design, by way of a Trajectory-Scheduling Controller (TSC) network. It is illustrated through the design of a networked, easy-to-understand and easy-to-use PID control system for the coupled liquid-tank. Results show that the methods developed offer a high-performance linear control system with nonlinear capabilities to handle practical systems operating in a broad range and to cope with conflict between setpoint following at transient and disturbance rejection at steady state. This method is then applied to the PID network design problems for two nonlinear chemical processes.

This research is concerned with analytical modelling of the effects of cracks in structural plates and panels within aerospace systems such as aeroplane fuselage, wing, and tail-plane structures, and, as such, is part of a larger body of research into damage detection methodologies in such systems. This study is based on generating a so-called reduced order analytical model of the behaviour of the plate panel, within which a crack with some arbitrary characteristics is present, and which is subjected to a force that causes it to vibrate. In practice such a scenario is potentially extremely dangerous as it can lead to failure, with obvious consequences. The equation that is obtained is in the form of the classical Duffing equation, in this case, the coefficients within the equation contain information about the geometrical and mass properties of the plate, the loading and boundary conditions, and the geometry, location, and potentially the orientation of the crack. This equation has been known for just over a century and has in the last few decades received very considerable attention from both the analytical dynamics community and also from the dynamical systems researchers, in particular the work of Ueda, Thompson, in the 1970s and 1980s, and Thomsen in the 1990s and beyond. An approximate analytical solution is obtained by means of the perturbation method of multiple scales. This powerful method was popularized in the 1970s by Ali H.Nayfeh, and discussed in his famous books, ‘Perturbation Methods’ (1974) and ‘Nonlinear Oscillations’ (1979, with D.T.Mook), and also by J.Murdock (1990), and M.P.Cartmell et al. (2003) and has been shown to be immensely useful for a wide range of nonlinear vibration problems. In this work it is shown that different boundary conditions can be admitted for the plate and that the modal natural frequencies are sensitive to the crack geometry. Bifurcatory behaviour of the cracked plate has then been examined numerically, for a range of parameters. The model has been tested against experimental work and against a Finite Element model, with good corroboration from both. In all events, this is a significant new result in the field and one that if implemented within a larger damage detection strategy, could be of considerable practical use.

Abstract The role of crack tip constraint in three dimensional fracture mechanics has been investigated under elastic-plastic conditions using finite element techniques. Out-of-plane constraint loss has been identified by comparing the mean stress of the three dimensional cracked body with a reference plane strain configuration. This has allowed the quantification of constraint loss due to thickness. This is important for fitness-for-service procedures where the use of standard thick deeply cracked samples inherently leads to conservative assessments. The proximity to plane–strain conditions was investigated, as well as the J-integral along the crack fronts of typical fracture mechanics specimens. It was shown that deep cracks (a/w=0.5) were significantly affected by out-of-plane constraint loss, while the effect was smaller for shallow cracks (a/w=0.1) when in-plane effects were dominant, where a is the crack length and w is the width of the specimen. The out-of-plane effect was confirmed experimentally with a series of fracture mechanics tests on thin and thick deeply cracked fracture mechanics samples. Computational and experimental studies showed that geometries with B/w=0.2 maintained high constraint conditions at the centre plane and exhibited a low fracture toughness, where B is the thickness of the specimen. As such they can be used to measure the plane strain fracture toughness (JIc) as long as the thickness and the ligament exceed 20J/σ0. The increased slope of the resistance JR curve and enhanced fracture toughness were correlated to the loss of out-of-plane constraint that developed in thinner samples (B/w=0.1). A procedure to incorporate the effects of out-of-plane constraint in the R6 failure assessment diagram was proposed. A procedure was developed to determine ductile crack growth of semi-elliptical surface cracks in flat plates. The procedure used the J-a resistance curve developed from standard high and low constraint geometries in conjunction with an analysis of the crack tip stress field using finite element modelling. This allowed the evolution of crack shape under ductile tearing to be modelled. The majority of the work was devoted to the study of surface breaking semi-elliptical cracks subject to bending, uniaxial tension or biaxial loading. Both the mean stress and J-integral were geometry and load dependent, and were non-uniformly distributed around the crack front. Crack growth was dependent on the level of crack tip constraint, and the original crack shape was generally not retained after ductile tearing. In bending the crack growth was suppressed in the thickness direction and the crack extended significantly sub-surface in a stable manner so that the crack adopted a boat shape. In tension the crack extended through the thickness and this was accompanied with extensive growth in the angular range 45ْ-70ْ. In biaxial loading higher constraint levels were observed, however the overall trend of crack growth was similar to uniaxial tension. Finally, the results from the finite element modelling and the crack growth procedure were verified with experimental data. Excellent agreement in the crack shape patterns was observed between the test data and the crack growth models.

The thesis 'The dynamics of tethers and space-webs' investigates the motion of the Motorized Momentum Exchange Tether (MMET) on an inclined orbit, and while deploying and retracting symmetric payloads. The MMET system is used as a basis for examining the stability of space-webs using a triangular structure of tethers while rotating. The motion of small robots is introduced as they move on the space-web, and their motions are found to influence the behaviour of the structure. Several methods of limiting the destabilising influences of the robots are considered, and are found to stabilise the web in most circumstances. A structured method for describing the rotations of a tether system is outlined, and different rotational systems are compared. This lays the foundation for the further chapters examining MMET dynamics on an inclined orbit and while deploying and recovering the payloads. Lagrange's equations are generated for the three cases, and are solved using standard numerical integration techniques. To emphasise the practical uses of the MMET system, several missions are analysed by using the system as a re-usable launcher for micro-satellite payloads.

There is growing interest in the development of fabrication techniques to cost effectively mass-produce high-resolution (micro/nano) 3D structures in a range of materials. Biomedical applications are particularly significant. This work demonstrates a novel technique to simultaneously fabricate a sacrificial mould having the inverse shape of the desired device structure and also create the desired device structure using electroplating deposition techniques. The mould is constructed of many thin layers using a photoresist material that is dissolvable and sensitive to UV light. At the same time the device is created in the emerging mould layers using Gold electroplating deposition technique. Choosing to fabricate the mould and the 3D structures in multiple thin layers allows the use of UV light and permits the potential cost-effective realization of 3D curved surfaces, the accuracy and geometric details of which are related to the number of layers used. In this work I present a novel idea to improve the LIGA process when using many masks to deposit multi thin layer over each other. Moreover, this technique can be utilized to produce a curved surface in the vertical direction with any diameter. Practically, a 2 µm thickness of layer is applied in the proposed technique. However, a layer of 0.5 µm or less can be deposited. An example is provided to explain the novel fabrication process and to outline the resulting design and fabrication constraints. With this technique, any structure could be made and any material used. The work employs conventional techniques to produce a 3D complex shape. By using conventional techniques with multi layers to produce a 3D structure, many problems are expected to occur during the process. Those problems were mentioned by many researchers in general but have not been addressed correctly. Most researchers have covered those problems by leaving the conventional and using a new technique they invented to produce the required product. However, in my work I have addressed those problems for the first time and I offered a new and effective technique to improve the MEMS technology and make this technology cheaper. This was achieved by using a research methodology requiring a rigorous review of existing processes, as outlined above, then by proposing a concept design for an improved process. This novel proposed process was then tested and validated by a series of experiments involving the manufacture of demo-devices. The conclusion is that this new process has the potential to be developed into a commercially implementable process.

This research is concerned with parametric vibration in composite beam structures with shape memory alloy elements. As a precursor to this investigation, a flexible steel beam of rectangular uniform cross-section is considered with a lumped end mass under a parametric excitation. A single frequency harmonic excitation in the vertical direction is applied to the system. As an extension of previsouly developed model by Cartmell (1990) and Forehand and Cartmell (2001), three nonlinear equations of motion, representing the first and second bending modes and the first torsion modes, are derived by recourse to the Lagrangian formulation. The variables in the equations of motions are , and respectively. They are coupled together and various nonlinearities appear in the equations. The three equations are used to predict different parametric resonances of the form , , by application of the perturbation method of multiple scales. Expressions for the transition curves for the three resonances have been derived which show the regions of stable and unstable solutions in a detuning parameter-excitation amplitude plane. Very close agreement is obtained between theoretical and experimental results for all the three resonance conditions. Laboratory tests confirm that these instabilities are bounded in practice by nonlinear effects. To investigate the effects of shape memory alloy on the dynamical properties of a composite material beam structure, two shape memory alloy strips are centrally-bonded to a glass epoxy beam with a lumped end mass. The two SMA strips are theoretically pre-strained and heated up to their full austenitic phase, and shown to generate large recovery forces due to this phase transformation. The forces are considered as compressive forces, and a theoretical model is introduced to evaluate the influences of the forces on the natural frequencies and the bending modes of the composite beam structure. The results show that the increase of the forces decrease the natural frequencies and reduce the excursion of the first and second bending modes. The beam system is then subjected to a vertical excitation. In order to utilize the Lagrangian formulation once again, the generalised forces corresponding to the generalised coordinates , and are derived in terms of the SMA recovery force. The three equations of motion of the free lateral vibration of the beam system are then derived. Three different parametric resonances are also predicted. Further study shows that the increase of the magnitude of the recovery force results in an increase of the instability region. An experimental investigation is conducted on two composite beam structures and each with an end mass, one with two centrally-bonded shape memory alloy (SMA) strips and the other with two diagonally-bonded SMA strips. The study suggests that when the strips are activated, the central-strip configuration can increase the natural frequencies of the bending modes noticeably more than the diagonal-strip one under certain circumstances, whilst the diagonal-strip configuration can easily be seen to change the frequencies of the torsion modes than the central-strip set-up.

The purpose of this study was primarily to promote the wider deployment of the hydraulic ram pump, and secondarily to provide the technical input into a programme aimed at using hydraulic ram pump technologies for third world development. Hitherto hydraulic ram pump technologies have been restricted by poor understanding of operational parameters, poor performance prediction, and poor design of pumps and installations. In pursuit of greater understanding the work utilised a computer simulation developed by the author as part of a previous research programme. This simulation was then greatly enhanced to provide improved accuracy and functionality. The enhanced simulation was then used to provide significant insight into the operation of a hydraulic ram pump and subsequently used to identify design improvements for the hydraulic ram pump. The simulation was used to investigate operational restrictions on the hydraulic ram, and was ultimately use to develop a model of hydraulic ram pump operation. The model of operation developed by the use of the simulation was computerised and used to predict the performance of hydraulic ram pump installations. This computerised model was then used to provide the most comprehensive design charts yet created for hydraulic ram pump, and was also used in the investigation of operational limits for the device. The study represents: the development of the first detailed simulation of the hydraulic ram pump and the most significant insight to date into the detail of operation of a hydraulic ram pump. The result of the study is the provision of an accurate method of pump calibration, an accurate method of pump performance prediction, and the first comprehensive design charts to be produced for the hydraulic ram pump.

This thesis investigates the application of quantitative, optical non-contact techniques to time varying stress fields to obtain time-resolved full-field measurements of stress and strain. Available optical techniques are reviewed and a specific case developed for the use of Photoelastic stress analysis (PSA). As a result of this research two novel developments in PSA are presented, including an industrially robust coating material technology and methods for high-speed acquisition of transient stress fields. These developments extend the potential applications of PSA and simplify the procedures involved. A novel birefringent electrolytic coating is presented and calibrated to demonstrate its potential as a practical photoelastic coating. The 20 m thickness coating is characterised and shown to behave linearly with strain. The coating also shows potential for application in plastic and non-linear photoelastic measurements. Several types of anodising and sealing treatments are compared, focusing on their relative sensitivity. The strain-optical coefficient (K) is derived for four thicknesses of decorative sulphuric acid anodising allowing qualitative and quantitative data to be extracted. Two time-resolved photoelastic techniques capable of measuring high(kHz) and low(Hz) frequency transient stress fields are described and demonstrated. Both techniques are based on a concept of a `Multiple View Polariscope', where the phase steps are captured simultaneously from multiple views. The configurations include a planar multi-camera method and a single camera with a modified `Quadrant' lens. As part of a collaborative study, compressor blade geometries were generated based on an existing Rolls-Royce component. The potential of the high-speed Multiple View Polariscope is demonstrated by the application to the compressor blades, which are subjected to a dynamic impact load to simulate domestic object damage. The resulting quantitative time-resolved stress fields allowed the performance of each blade to be compared against the original component. This investigation has shown the potential for general robust optical tools for industrial quantitative applications of residual, static and dynamic stress measurement.