Steel plates are widely used in a variety of civil engineering applications for load bearing structural components, due to their favourable strength to weight ratio. Many of these plates have openings that are commonly used for reducing weight, access for utilities or for inspection in shipping and offshore installations. However the influence of these openings to the structural component’s robustness and resilience against blast loading is relatively unknown, with limited research conducted in this subject to date. Due to the high costs associated with offshore facilities they are typically very congested. This coupled with the producing, processing, storing and transporting of hydrocarbon materials means that explosions and subsequent fires are major hazards with severe consequences. In the event of an explosion, the blast load will initially impact the secondary structure (large spanning plated sections) and then transfer through to the primary structure, highlighting their critical consideration in safety assessments. Plated structures are also known to cause confinement, which in turn will results in higher overpressures, making the consequences of an event more severe. The aim of this research was to investigate the combined influence that openings have on the overpressure and the structural response of thin ductile plates subjected to extreme dynamic transverse loads. This was achieved by conducting a set of well-defined experiments investigating the response of 1/8 scale (0.5 m square) mild steel plates with openings subjected to pulse pressure loading. Six central (scaled) openings were considered; circular (50, 75 and 100 mm) and extended circular (50 by 75, 75 by 100 and 100 by 125 mm) representative of typical offshore and shipping applications. Each plate design was assessed with two boundary conditions (restrained and non-restrained) and two nominal loading conditions. The boundary conditions adopted in this study allowed the response to be bounded, and enabled them to be practicably modelled in FEA-analyses and in the simplified analytical approaches. A pulse pressure test facility was used to generate nominal pulse pressure loads (25 and 50 psi) applied over a time (100 to 200+ ms load duration) representative of extreme explosion loading conditions offshore. All plates exhibited a mode I type failure (large inelastic deformation) highlighting the large reserve strength in such members. The work has shown that the inclusion of an opening (<5% of the exposed panel area) does not significantly degrade the structural resistance when damage is restricted to large inelastic deformation. The reduction in stiffness due to the hole is compensated by the reduced area to which the load is applied. The data generated in the laboratory tests was used to develop and validate finite element models. In general, excellent correlation was observed between the experimental failure modes and the permanent displacements, within an average difference of 12% and 15% for the restrained and non-restrained plates respectively. The finite element models also provided a useful insight into the various failure processes and transient behaviour which could not be observed experimentally. A simplified analytical model was developed to predict the response of the plates and was validated against the experimental data. The results for the permanent displacements compared favourably with the restrained plates at the two nominal pressures (6.5% at 25 psi and 7% at 50 psi), but correlated less well with the non- restrained ones (10% at 25 psi and 3% at 50 psi). Correct definition of support conditions along with a detailed description of the development of plasticity, as shown in the finite element models was fundamental in accurately predicting response of the non-restrained plates. The simplified techniques developed are cost effective compared with more sophisticated finite element methods making them suitable for preliminary engineering design studies. Ultimately this study provides evidence to suggest that small (circular or extended circular) openings positioned away from areas of high stress, could be used as a passive system to mitigate the influences of an explosion event offshore. This has many benefits in the form of reducing weight, reducing confinement (thus lowering overpressures) and reducing the loading applied to these members, and subsequently reducing the loading transferred through to the primary structure.

In this thesis, the development of thin films and nanostructures prepared with chemical vapour techniques are investigated for applications in photovoltaics. The deposition of both p-type and n-type oxides are investigated as a means of preparing all oxide p-n junctions. Both CVD and ALD precursors and processes have been developed. Zinc oxide nanowires are of interest as an n-type absorber layer with high surface area. In this thesis, the crystal structures of DEZn and DMZn were revisited and a new understanding of conventional zinc CVD precursors is presented. For DEZn a single structure was isolated and characterised with single crystal XRD. In the case of DMZn two temperature dependant structures were identified: namely α and β at 200K and 150K respectively. The DMZn precursor was subsequently exploited in a series of adduct-based precursors of the notation [DMZn.L] (where L = 1,2-dimethoxyethane, 1,4-dioxane and 1,4-thioxane). The crystal structures of these precursors were determined, and they were subsequently used to grow ZnO and sulphur doped ZnO across a range of CVD growth conditions. The microstructure and electronic properties of the nanowires have been characterised with electron microscopy, x-ray diffraction, Raman spectroscopy and photoluminescence. The II:VI ratio and substrate temperatures were both confirmed as playing a significant role in determining the microstructure of the nanowires. It has been demonstrated that the use of [DMZn.L] can avoid the pre-reaction between DMZn and oxygen. The studies with the thioxane adduct suggests the involvement of the ligand and hence sulphur incorporation in the nanowires. Two copper precursors were selected as the basis of p-type copper oxide film studies. The first Cu(hfac)(COD) has been used previously to deposit copper oxide by conventional CVD. In this thesis it is demonstrated for the first time that a pulsed LI-ALD approach can be exploited to deposit CuO with ozone as the co-reagent. An unexpected outcome of the research was the successful growth of electrically conductive copper metal films with a sheet resistance of 0.83Ω/□ when the precursor was thermally decomposed. The second copper precursor, namely CpCu(tBuNC) was used in atomic layer deposition to successfully deposit CuO or Cu2O with oxygen plasma and water respectively. Having identified that the β-diketonate compound yielded copper, the cyclopentadienyl based precursor was investigated as a route for the deposition of conductive copper metal films. Both thermal decomposition and a hydrogen plasma ALD process have been shown to deposit copper. With the plasma process, deposition of copper was demonstrated as low as 75˚C with a sheet resistance of only 0.55Ω/□. This thesis has demonstrated novel deposition routes for p- and n-type oxide materials which have potential future applications in thin film or nanostructured photovoltaic technology.

In this study, aluminium matrix syntactic foams reinforced with several types of ceramic micro-sphere were produced by pressure infiltration. The mechanical properties of a range of aluminium matrix syntactic foams were investigated in order to optimise the composition and structure to find the best configuration in terms of high energy absorption capability, and to validate the finite element predictions against the corresponding experimental results. Initially, the compressive behaviour of six different types of aluminium matrix syntactic foam was evaluated. It was shown that the size of the ceramic micro-spheres, the grade of the aluminium matrix and the volume fraction of the aluminium matrix all have a significant influence on the compressive strength and energy absorption capability of the material. Then, the three-point bending and shear fracture properties of aluminium syntactic foams were evaluated. These tests indicated that density plays an important role in determining the stiffness, specific energy absorption and ultimate flexural strain. Here, it was found that the specific energy absorption related to shear was lower than that corresponding to flexure. Following this, the behaviour of the syntactic foams under low velocity impact was characterised and the underlying failure mechanisms were identified to evaluate their effective mechanical performance. It was found that the aluminium syntactic foams subjected to drop-weight impact have 20–30% higher plateau values than samples subjected to the equivalent level of quasi-static compression. Subsequently, the Split Hopkinson Pressure Bar technique was used to investigate the behaviour of the material at high strain-rates, which highlighted the material sensitivity of aluminium syntactic foams under high strain-rate loading. Following this, terminal ballistic tests were conducted to determine the perforation resistance of the aluminium syntactic foams. The results showed that the syntactic foams have the ability to prevent the perforation of projectile velocities up to 120 m/s. Finally, blast tests were performed to investigate the influence of the charge mass and sample thickness on the dynamic response of the syntactic foams. The results showed that syntactic foams with a thickness of 14 mm have the capability to sustain a blast load of 4.82 Ns. Finite element models were developed to simulate the structural behaviour of aluminium syntactic foams subjected to various quasi-static and dynamic loads. Here, an elasto-plastic model with both ductile and shear failure criteria was employed to predict the material performance. The rate-dependent response of the foam was considered by a stress-ratio based model to take strain-rate effects into account. The numerical simulations were compared with their corresponding experimental results with reasonably good correlation. In general, the essential features of the aluminium syntactic foams tested under different loading regimes were captured by the FE models, including load-displacement traces, deformation and failure modes.

In this study, the mechanical properties and fracture behaviour of a range of core materials have been investigated in order to elucidate the impact properties of sandwich structures. Initially, the compression properties of the core have been evaluated at quasi-static and impact rates of strain. It has been shown that the plastic collapse strength of the cores is highly rate-sensitive, increasing by up to one hundred percent in passing from quasi-static to dynamic rates of loading. Subsequently, the SENB (Mode I) and shear (Mode II) fracture properties of the polymer foams were evaluated. Mode I tests have shown that the crosslinked PVC foams and the PET foams fail in a brittle manner, however, the linear PVC foams fail in a ductile mode. Here, it has been shown that the Mode II shear toughnesses of the crosslinked PVC foams were up to thirty-five times greater than their corresponding Mode I values. Following this, a series of indentation tests were conducted on polymer-foam sandwich structures and their response was characterised using a Meyer indentation law of the form P = Can. It has been shown that the value of the exponent parameter, n, does not vary significantly with the properties of the core or the skin, typically being close to unity for all tests. The contact stiffness, C, was found to depend on the plastic collapse strength of the foam, the indentor radius and the properties of the skin. It has been shown that a plot of contact stiffness against plastic collapse strength, containing all of the quasi-static and dynamic data, appears to yield a unique curve. Subsequently, the perforation resistances of a range of foam-based sandwich structures were investigated. The influence of the plastic collapse stress of the foam in determining the failure thresholds of the front and rear composite skins has been established. Here, a simple model has been used to successfully predict failure of the top surface composite skin in the sandwich structures. In addition, the force associated with perforating the lightweight core has been shown to be strongly dependent on the shear strength of the polymer foam. The perforation response of sandwich structures based on fully-recyclable materials has also been investigated. The design of the SRPP skin has a significant effect on the energy-absorbing characteristics of the sandwich structure, with the performance of systems based on multiple layer skins greatly exceeding that associated with a monolithic skin. It has been shown that when normalised by the areal density of the panels, those sandwich structures with multiple layer skins out-perform systems with monolithic skins as well as conventional GFRP/aluminium honeycomb sandwich structures.

The work reported in this thesis has investigated the impact of ship superstructure geometry on helicopter operations to the flight decks of naval warships. Ship-Helicopter operating limits for military frigates and destroyers are often restricted in difficult weather conditions because of excessive pilot workload caused by the unsteady ship airwake. Experiments have been conducted in a water tunnel using a specially designed Airwake Dynamometer (AirDyn) to characterise the steady and unsteady aerodynamic loading of a helicopter immersed in the airwake of a generic ship that has been called the Shortened Research Frigate (SRF). The AirDyn is a 1:54 model-scale helicopter, mounted on a six-component force block; it has a simplified spinning main rotor and fuselage based on a Merlin AW-101. The AirDyn has been shown to be an effective tool for characterising the steady and unsteady aerodynamic loading of a helicopter model in a ship’s airwake and the aerodynamic loads measured by the AirDyn were found to correlate with at-sea and simulation flying experience for a range of Wind-Over-Deck (WOD) conditions and ship geometry configurations. The airwakes of the SRF without the presence of a helicopter model have also been investigated using unsteady Computational Fluid Dynamics (CFD). A Detached-Eddy Simulation (DES) approach was used for the turbulence modelling as it has been shown to be capable of capturing the bluff-body type flow features typical of ship airwakes. Analysis of the CFD data revealed the underlying aerodynamic causes of the observed loading characteristics of the AirDyn. A range of ship geometry modifications were made to the SRF to determine the feasibility of mitigating the adverse effects of the airwake by modifying existing ships or by improving the designs of future ships. A range of modifications to the windward hangar side-face of the SRF were tested using the AirDyn and were found to reduce the severity of unsteady loads by up to 55% for oblique WOD angles (Green 30°-45°) at important locations through the flight path of a standard Royal Navy deck-landing manoeuvre. Unsteady CFD analysis showed that the modifications controlled the flow separation from the top edge of the windward hangar side-face in such a way as to reduce the height and the angle of the separated flow and thus the severity of the unsteady flow structures being drawn into the main rotor of the AirDyn. The unsteady CFD data computed for the baseline and modified SRF ship geometries was also integrated into the University of Liverpool’s motion-base flight simulator and piloted flight simulation trials were conducted to determine the impact of the ship modifications on pilot workload. The results of the simulation flight trials confirmed the usefulness of the AirDyn as a tool for predicting pilot experience and showed that it is feasible to modify ship superstructures to the extent that tangible reductions in pilot workload are achieved.

The ability to control and manipulate the state of polarization of a laser beam is becoming an increasingly desirable feature in a number of industrial laser micro-processing applications. Being able to control polarization would enable the improvement of the efficiency and quality of processes such as the drilling of holes for fuel-injection nozzles, the processing of silicon wafers or the machining of medical stent devices. This thesis presents novel, liquid-crystal-based optical setups for controlling the polarization of ultrafast laser beams, and demonstrates how such optical setups can be used to improve laser micro-processing efficiency and quality. Two experimental strategies were followed: the first used dynamic control of the polarization direction of a linearly polarized beam; the second generated beams with complex polarization structures. Novel optical analysis methods were used to map the polarization structures in the focal region of these laser micro-processing setups, using Laser Induced Periodic Surface Structures (LIPSS) produced on stainless steel sample surfaces at low laser fluence (around 1.5J/cm²), close to the ablation threshold of steel (i.e. 0.16J/cm²). This helped to characterize and calibrate the optical setups used in this thesis. The first experimental method used a fast-response, analogue, liquid-crystal polarization rotation device to dynamically control the direction of linear polarization of a laser beam during micro-processing. Thanks to its flexibility, the polarization rotator could be set-up in various synchronized configurations, for example keeping the polarization direction constantly perpendicular to the beam scanning motion. Drilling and cutting tests were performed on thin (~0.4mm thick) stainless steel sheets using a 775nm femtosecond laser at 24J/cm². The experimental results showed a consistent improvement in the micro-processing quality when the polarization direction was synchronized with the beam scanning motion. The sidewall surface roughness and edge quality of the machined structures were improved significantly, with the dimensions of ripples and distortions divided by a factor of two. The overall processing efficiency was also increased compared to that produced by linear or circular polarizations. The second experimental method used a digital, Liquid-Crystal On Silicon (LCOS) Spatial Light Modulator (SLM) to generate polarization structures with a cylindrical geometry, or Cylindrical Vector Beams (CVBs). A Jones matrix analysis was used to model the optical setup and predict the ability to produce CVBs in this way. The setup was implemented in a 775nm femtosecond laser micro-processing bench and the resulting polarization analyzed with a polarizing filter, demonstrating a polarization purity better than 84%. The amplitude and polarization properties in the focal region of the setup were studied using LIPSS produced on the surface of stainless steel samples at low fluence (1.5J/cm²), to check that the expected state of polarization had been achieved. An analytical model of the experimental setup was developed to explain the experimental results. The model predictions were in agreement with the experimental results and clarified how the polarization and phase structures affect the focal properties of the produced laser beams. Various types of CVBs were used with a high laser beam fluence (24J/cm²) for micro-machining 0.2-0.4mm thick stainless steel plates. A comparative analysis of micro-machining with radially, azimuthally, circularly and linearly polarized beams was carried out. It was shown that a radially polarized beam was more efficient at drilling and cutting high-aspect-ratio features when the plate thickness was above 0.2mm. The gain in processing speed was better than 5% compared with a circularly polarized beam and better than 10% compared with an azimuthally polarized beam, under the chosen processing parameters. However the processing speed was similar for all these polarization states (radial, azimuthal and circular) when machining 0.2mm thick plates. It was also shown that a radially polarized beam improved the processing quality, reducing the distortions affecting the edge quality of the machined structures.

Concrete mixes incorporating ground granulated blast furnace slag (GGBS) has not gained popularity in fast track construction. It is believed to be due to its slower strength development at early age cured under standard curing temperature. The benefits that are obtained when using GGBS in concrete such as economic, sustainability and durability are discussed. Two grades of mortars/concretes i.e. C45 and C75 containing GGBS at levels of 0, 20, 35, 50 and 70% have been investigated to give guidance for their use in fast track construction. The effect of curing temperature on the strength development of mortars/concretes containing different levels of GGBS at early and later age have been investigated by testing strength of the mortars/concretes. The mortars were cured at 10, 20, 30, 40 and 500C and adiabatically cured conditions; while the concrete specimens were cured at 20 and 500C, as well under adiabatic curing conditions. The mortars/concretes were tested at age of 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256 and 365 days. There were also five mixes for lightweight concrete and three mixes for self compacting concrete that cast and cured under different temperatures of 20, 30, 40 and 500C, as well as under adiabatic curing conditions. This aims to evaluate the strength development of this kinds of concrete cured at different curing temperatures. The cubes were tested at the age of 0.125, 0.25, 0.5, 1, 2, 4, 7, 14 and 28-days. The heat outputs using of equivalent mortar mixes are measured using isothermal calorimeter. This is used to assess the temperature sensitivity of the strength development of GGBS concrete. It is also used to investigate the contribution of GGBS on the heat output produced in the hydration of binder. The accuracy of the existing maturity methods, which were developed based on concrete with Portland cement only, is evaluated to predict the strength of GGBS concrete investigated in this study. A new method, which is called Modified Nurse-Saul (MNS) method, is recently developed to predict strength development of concrete in this study. This method is used to predict the strength development of both Portland cement and GGBS concretes, as well as to predict the heat output development of equivalent mixes mortar. Finite element modelling was used to predict the temperature rise in concrete. Both the predicted heat output obtained from adiabatic test and isothermal calorimeter were used as heat sources. The predicted temperature is used to predict the strength development of concrete.

Medical devices are used to recreate damaged or diseased joints and also to restore pain reduced mobility to patients. Devices such as hip and knee implants are fixed to the host bone by use of acrylic bone cement or by a press-fit interference technique. The surface of the press fit implants may be roughened, but non-porous, which allows new bone to form on the surface, or they may be porous to encourage bone growth into the structure. Traditionally implants are produced by machining, casting or forging, before applying any coatings that are required. More recently Additive Manufacturing (AM) techniques such as Electron Beam Manufacturing (EBM) and Selective Laser Melting (SLM) have attracted interest as they may be able to create the whole device in one operation. This thesis describes the research carried out to produce “Vaulted Structure (VS)” as a method for creating specific porosity with increased strength in porous medical devices. Unit cell structures (Wire frames) are inherently weak because of the struts. It was proposed that VSs, constructed of platelets, would have a higher specific strength and therefore extend the range of available properties while still maintaining a structure that resembles cancellous bone, a structure preferred by surgeons. The creation of a VS begins with a computer model of the object to be created. This is then surrounded by an axis aligned bounding box, a box that has edges parallel to the x, y and z directions and just encloses the object. The bounding box is then voxelised, so it consists of many smaller cubic boxes, these boxes being the size of the required structure. The VS is then constructed by creating holed platelets on some of the surfaces of the smaller boxes, with these platelets being randomly deformed if required. The structure within the bounding box is then trimmed to the boundary of the required structure, this being accomplished using a rapid technique developed during this project. To allow manufacture of the components, the structure is sliced to create a suitable format for the SLM. By using SLM in combination with these new novel structures, a wide range of possible properties and morphologies can be generated, these being controlled by the cell size, hole size, thickness of the platelet and the level of randomisation. ii A range of structures with different morphologies were produced and mechanically tested in compression. It was found that a percentage randomisation of more than 60% and a cell aspect ratio of 1:1:2, produced isotropic mechanical behaviour, while other structures produced very different behaviour. It was also observed that the failure mode in compression could be controlled by the degree of randomisation and this is discussed in the thesis. A property that is important in the medical device industry is the look of the component as this affects up take by surgeons. The preferred structures are ones that look like cancellous bone and the new structures created here match both the look and mechanical properties of this material, but with the added advantage that it is possible, by modifying the control variables, to match the structure to cancellous bone from different aged patients. The research presented in this thesis considers the inter-relationship between the process parameters, architecture, properties of the structures and why these inter relationships occur. The research presented here extends knowledge of how to create these novel material/structure combinations, how to tailor them to a given purpose and by predicting behaviour in software produce the most suitable properties for a given medical device without extensive testing.

In manufacturing industry, although automation techniques have been employed widely, many tasks still require the flexibility and intelligence of human operators, especially in the product assembly process. Insufficient industrial ergonomics in the assembly process will cause the health problems and quality and productivity losses, ultimately increase costs of the final product. The purpose of this thesis is to integrate ergonomic considerations into the manual assembly process modelling and simulation in order to provide product/process design changes before their physical prototyping. In this research, a state-of-the-art commercial software tool - DELMIA - is adopted for the ergonomics simulation and analysis. Associated with its capabilities for the ergonomics solution, a series of human related issues in the manual assembly process is simulated and studied in order to demonstrate the benefits of a virtual assembly approach to the product deign, workplace deign, time and energy saving. Due to the poor repeatability and reproducibility of digital human postures in DELMIA manipulation, a posture prediction method is developed aiming at a practical and precise ergonomics analysis. A 10-degrees-of-freedom, 4-control-points digital human model concerned with assembly features and human diversity is established. The multi-objective optimisation method is applied to assembly posture prediction in which optimisation objectives (i.e. joint discomfort and metabolic energy expenditure) and constraints corresponding to manual assembly tasks are proposed and formulated. Following the verification of the posture prediction method, a series of posture strategies under different assembly conditions are investigated towards more comfortable and energy-efficient assembly postures. Thus far, the consideration on assembly operators in assembly sequencing is insufficient though it plays a key role in the integrative product and process design. In this research, the use of new ergonomic constraints into assembly sequencing optimisation is proposed. Feasible assembly sequences are generated and evaluated based on the product geometry, assembly workstation layout, operator characteristics and working posture. A new Liverpool Assembly Sequence Planning System (LASP) is developed to achieve the integration by applying two evaluation criteria, i.e. visibility criterion, accessibility criterion or both. With LASP, possible design faults with respect to restricted visibility and obstructed accessibility is obtainable during the early design stage. Meanwhile, the optimum sequences are provided to operators automatically for ease of manual assembly, facilitating higher assembly quality and efficiency.

In this thesis the effect of uniform and profiled (non-uniform) steady flows on a scale-model tidal stream turbine (0.5m diameter) are experimentally investigated using the University of Liverpool high-speed recirculating water-channel. The power and thrust coefficients of the turbine with numbers of blades between two and six and various blade-pitch-angles are measured in uniform flow with low levels of turbulence at velocities ranging from 0.45m/s to 1.34m/s. With a three-bladed turbine at optimum blade-pitch-angle the power and thrust coefficients are compared in three different flow conditions of uniform flow with low turbulence intensity (2%), uniform flow with high turbulence intensity (5%) and non-uniform flow with high turbulence intensity (5%). Using an Acoustic Doppler Velocimeter (ADV) measurements of three-dimensional velocities are taken, initially, around the three-bladed turbine with optimum blade-pitch-angle. The velocities at five different heights and up to 7D downstream are probed where the upstream velocity is uniform with low turbulence levels and mean upstream velocity of 0.9m/s. Further ADV measurements are taken downstream of the three-bladed turbine through a horizontal centre-plane at lower velocities of 0.45m/s and 0.68m/s to probe the effect of Reynolds number on the turbine's wake. In addition wake measurements are taken downstream of the two-bladed turbine with optimum and non-optimum blade-pitch-angles to study the effect of differing tip-speed-ratios, thrust and power coefficients. Also the wake of the turbine support structure without blades is investigated. In a flow with high turbulence and mean velocity of 0.9m/s the wake of the three-bladed turbine is studied through a centre-plane equal to the turbine hub height. Further in a profiled flow, representative of a 1/5th velocity power law and upstream integral average velocity of 0.82m/s (over the turbine's swept area), characterisation of the flow downstream of the three-bladed turbine with optimum blade-pitch-angle is taken at five depths up to 5D downstream. These velocities are then compared in detail to those in uniform flow. Finally the ADV technique is used extensively throughout this thesis and, indeed, in most studies concerned with tidal turbine wakes. As issues regarding certain aspects of the ADV came to light during this study, the robustness of this technique is investigated by using two different ADV probe orientations and a comparison to 1D Laser Doppler Velocimetry is made.