PhD, EngD, MPhil and MSc by research theses (SAS)

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Open Access
3D advance mapping of soil properties
(Cranfield University, 2012-07) Veronesi, Fabio; Mayr, T.; Corstanje, Ronald
Soil is extremely important for providing food, biomass and raw materials, water and nutrient storage; supporting biodiversity and providing foundations for man-made structures. However, its health is threatened by human activities, which can greatly affect the potential of soils to fulfil their functions and, consequently, result in environmental, economic and social damage. These issues require the characterisation of the impact and spatial extent of the problems. This can be achieved through the creation of detailed and comprehensive soil maps that describe both the spatial and vertical variability of key soil properties. Detailed three-dimensional (3D) digital soil maps can be readily used and embedded into environmental models. Three-dimensional soil mapping is not a new concept. However, only with the recent development of more powerful computers has it become feasible to undertake such data processing. Common techniques to estimate soil properties in the three-dimensional space include geostatistical interpolation, or a combination of depth functions and geostatistics. However, these two methods are both partially flawed. Geostatistical interpolation and kriging in particular, estimate soil properties in unsampled locations using a weighted average of the nearby observations. In order to produce the best possible estimate, this form of interpolation minimises the variance of each weighted average, thus decreasing the standard deviation of the estimates, compared to the soil observations. This appears as a smoothing effect on the data and, as a consequence, kriging interpolation is not reliable when the dataset is not sampled with a sampling designs optimised for geostatistics. Depth function approaches, as they are generally applied in literature, implement a spline regression of the soil profile data that aims to better describe the changes of the soil properties with depth. Subsequently, the spline is resampled at determined depths and, for each of these depths, a bi-dimensional (2D) geostatistical interpolation is performed. Consequently, the 3D soil model is a combination of a series of bi-dimensional slices. This approach can effectively decrease or eliminate any smoothing issues, but the way in which the model is created, by combining several 2D horizontal slices, can potentially lead to erroneous estimations. The fact that the geostatistical interpolation is performed in 2D implies that an unsampled location is estimated only by considering values at the same depth, thus excluding the vertical variability from the mapping, and potentially undermining the accuracy of the method. For these reasons, the literature review identified a clear need for developing, a new method for accurately estimating soil properties in 3D – the target of this research, The method studied in this thesis explores the concept of soil specific depth functions, which are simple mathematical equations, chosen for their ability to describe the general profile pattern of a soil dataset. This way, fitting the depth function to a particular sample becomes a diagnostic tool. If the pattern shown in a particular soil profile is dissimilar to the average pattern described by the depth function, it means that in that region there are localised changes in the soil profiles, and these can be identified from the goodness of fit of the function. This way, areas where soil properties have a homogeneous profile pattern can be easily identified and the depth function can be changed accordingly. The application of this new mapping technique is based on the geostatistical interpolation of the depth function coefficients across the study area. Subsequently, the equation is solved for each interpolated location to create a 3D lattice of soil properties estimations. For this way of mapping, this new methodology was denoted as top-down mapping method. The methodology was assessed through three case studies, where the top-down mapping method was developed, tested, and validated. Three datasets of diverse soil properties and at different spatial extents were selected. The results were validated primarily using cross-validation and, when possible, by comparing the estimates with independently sampled datasets (independent validation). In addition, the results were compared with estimates obtained using established literature methods, such as 3D kriging interpolation and the spline approach, in order to define some basic rule of application. The results indicate that the top-down mapping method can be used in circumstances where the soil profiles present a pattern that can be described by a function with maximum three coefficients. If this condition is met, as it was with key soil properties during the research, the top-down mapping method can be used for obtaining reliable estimates at different spatial extents.
Open Access
A3 thinking approach to support lean product and process development
(Cranfield University, 2013-03) Mohd Saad, Norhairin; Al-Ashaab, Ahmed; Shehab, Essam
This research project aims to develop a novel A3 thinking approach to support knowledge driven design that aids the generation of decision making within a Lean Product and Process Development (LeanPPD) environment. This research comprises the development of a new A3 template as a technique of problem solving in product design, the adoption of a reflection practice structured in a new A3 template for knowledge capture and sharing, and the generation of the process of using the A3 thinking approach for effective implementation. Providing useful knowledge as a design reference to generate decision making at the initial stages of product development in product design helps the designers to prevent recurrence of the same problem, eliminate design mistakes and enhance design decision. In order to achieve a novel A3 thinking approach, a research methodology consisting of four phases was developed. The first phase synthesises the A3 best practice through literature and documentation reviews. The gap analysis and results from the reviews have identified several problem-solving approaches and learning cycles that have to be considered in the research. The second phase is to evaluate the approaches and their impacts and applications in product design. In order to complete this, several research methods are selected and performed (e.g. focus group and semistructured interview) within the collaborative companies. The third phase is to develop the A3 thinking approach by utilising the LAMDA learning cycle, developing a new A3 template or so-called A3LAMDA, adopting the reflection practice and generating the process of using the new A3 thinking approach. Finally, the validation of the new A3 thinking approach through industrial case studies and expert judgements have been performed. This approach has been implemented in the automotive sector and was applied to four industrial case studies and six A3LAMDA reports were collected. As a result of the findings of this research, the utilisation of the A3 thinking approach aided the generation of knowledge driven design in product design by integrating the knowledge management capabilities; knowledge creation, capture and sharing.
Open Access
Abrasive machining with MQSL.
(Cranfield University, 2011-07) Morris, Tom; Stephenson, David J.; Walton, I.; Nicholls, J. R.
Grinding and polishing of engineered components are critical aspects of the precision manufacturing of high performance, quality assured products. Elevated process temperatures, however, are a common and for the most part undesirable feature of the grinding process. High process temperatures increase the likelihood of microstructural change within the immediate subsurface layer and are detrimental to the strength and performance of the manufactured products. Increasing processing costs and tighter environmental legislation are encouraging industry to seek innovative fluid application techniques as significant savings in production can be achieved. In this context, and with sponsorship from three industrial partners, namely; Fives Cinetic, Fuchs Lubricants plc and Southside Thermal Sciences Ltd, and also from the Engineering and Physical Science Research Council (EPSRC), this research aimed to develop an understanding of Minimum Quantity Solid Lubrication (MQSL) as a method for abrasive machining, with particular reference to the control of surface temperatures. Improving the lubricity of Minimum Quantity Lubrication (MQL) fluids reduces the frictional source of process heat and controls the finish surface temperature. The application of effective solid lubricants is known as Minimum Quantity Solid Lubrication (MQSL). Molybdenum Disulphide (MoS2), Calcium Fluoride (CaF2), and hexagonal Boron Nitride (hBN) were compared against a semi-synthetic water soluble machining fluid (Fuchs EcoCool). A series of Taguchi factorial experimental trials assessed their performances through ANOVA (ANalysis Of VAriance) statistical method. The hBN produced the lowest grinding temperatures of the solid lubricants tested, although they still remained higher than those achieved using the EcoCool control. The reduction of the machining fluid enabled a Charged Coupled Device (CCD) sensor to be fitted into the grinding machine. The recorded movement in the emitted spectrum from the grinding chips was compared to experimental and modelled process temperatures. This showed that the wavelengths of the chip light correlated to the temperature of the finish grinding surface. This greatly contributed to determining the feasibility of constructing a non-destructive, non-invasive, thermally-adaptive control system for controlling grinding surface temperatures.
Open Access
Accumulation, transport and potential treatment of surface sediment on car parks with channel drains
(Cranfield University, 2015-11) Barlow, James Vincent; Harris, Jim A.; Hess, Tim M.
Urban pollutants have been identified as a significant source of environmental pollution, posing a risk to human health, the environment, and are toxic to flora and fauna. Highways are recognised as one of the key sources of pollution, from both vehicles, and surrounding infrastructure. A number of studies have investigated accumulation of sediment and the associated pollutants on highways, and the runoff generated as a result of rainfall. Car parks share many potential contributory sources of pollutants with highways, but there is a lack of studies regarding car parks, despite them being identified as a significant percentage of urban land use. A series of experiments were undertaken in order to develop an understanding of the characteristics of car park sediment. The physical and chemical characteristics of sediment were analysed at different stages throughout the drainage system. Firstly on the sediment accumulated on car park surfaces, followed by that mobilised and transported into a channel drain during simulated rainfall events. Finally, potential treatment of pollutants within sediment in a channel was quantified. The physical and chemical characteristics of car park sediment was shown to be similar during both the accumulation (build-up) and wash-off stages, suggesting that the accumulated sediment is generally mobilised and transported to the channel drain (wash-off). Furthermore, both the physical and chemical characteristics of the sediment were shown to be similar to those found on highways, thorough the build-up and wash-off phases. Finally, potential treatment of organic pollutants (PAH) by biodegradation was demonstrated, but not comprehensively proved.
Open Access
Acquisition and interpretation of dielectric data for thermoset cure monitoring
(Cranfield University, 2003-09) Kazilas, Michalis C.; Partridge, Ivana K.
The interpretation and modelling of the dielectric response of thermosetting materials during cure was the main focus of this study. The equivalence of complex permittivity and complex impedance in terms of information content was outlined in a series of case studies covering the separate effects of dipolar movements and charge migration as well as the combined effect of the two polarisation mechanisms. Equivalent electrical circuits were used in order to model the evolution of the complex impedance during cure. A numerical method that can model consecutive spectra throughout the cure was developed. The method is based on Genetic Algorithms and requires only input from the modelling of the initial spectra. Complex impedance spectra were collected during the cure of a commercial epoxy resin formulation under isothermal and dynamic heating conditions. The spectra were analysed and modelled. The modelling was successful over the whole frequency range of the measurements (1 Hz – 1 MHz). The analysis of the estimated model parameters showed that charge migration dominates the dielectric response in a wide frequency range. In addition, the modelling algorithm also distinguished between the effects of electrode polarisation and dipolar movements in the signal. A new equivalent circuit was used in order to map the frequency regions where the each one of the three phenomena that together comprise the dielectric signal can be monitored most effectively. A chemical cure kinetics model was developed for the studied system. A correlation between the maximum point of the imaginary impedance spectrum and the reaction conversion was established. A mathematical model, based on a simple linear dependence of the dielectric signal on conversion and temperature, was built. The model predictions agreed well with the experimental data. The aim of simplifying the interpretation of the dielectric signals led to the development of a new experimental technique. Temperature Modulated Dielectric Analysis employs temperature modulations superimposed on an underlying thermal profile in order to separate the influence on the signal of the temperature alone from that of the cure reaction. The early study carried out here shows that such measurements are feasible and reveals important issues for its further development.
Open Access
Acquisition and sharing of innovative manufacturing knowledge for preliminary design
(Cranfield University, 2009) Mountney, Sara; Gao, James X.; Roy, Rajkumar
This study investigates the identification, acquisition and sharing of innovative manufacturing knowledge for the preliminary design of complex mechanical components. Such components need to satisfy multiple, often conflicting design and performance requirements. Some degree of innovation may be required, involving the development of new manufacturing processes. The innovative nature of this manufacturing knowledge makes it difficult to define, codify and share, especially during preliminary design, where this can present significant risks in the design process. Current methods of knowledge sharing do not account for the immature nature of innovative manufacturing knowledge and the combined explicit and tacit elements needed to express it. A flexible interpretive research study with inductive and hypothesis testing elements was undertaken to explore this novel knowledge management problem. During the inductive phase, two data collection activities were undertaken to investigate the manufacturing knowledge required for the preliminary design of gas turbine engines. Using a data driven approach, the main findings which emerged were: the need to include an assessment of the maturity of the design process; the need to use a range of tacit and explicit knowledge to effectively share this and the need to manage knowledge across different domain boundaries. A conceptual framework of the findings was used to develop a hypothesis of knowledge requirements for preliminary design. For the hypothesis testing phase, a systematic methodology to identify, acquire and share innovative manufacturing knowledge for preliminary design was developed from the knowledge requirements. This approach allowed both explicit and tacit knowledge sharing. An evaluation of the methodology took place using three different industrial cases, each with a different component / manufacturing process. The evaluations demonstrated that using the range of knowledge types for transferring knowledge was effective for the specific cases studied and confirmed the hypothesis developed.
Open Access
An adaptive control system for off-line programming in robotic gas metal arc welding.
(Cranfield University, 1997-10) Carvalho, G. C.; McMaster, R.
The aim of this work was to develop an integration concept for using off-line programming in robotic gas metal arc welding of thin sheet steel. Off line -welding parameter optimization and on-line monitoring and adaptive control of process stability and torch-to-workpiece relative distance were used to ensure weld consistency. The concept developed included four main aspects: a) the use of a CAD system to design the workpiece; b) the use of a welding off-line programming system to design the welds, generate the welding parameters and to extract geometrical information from the CAD models to generate a robot program; c) the use of a graphical simulation system to simulate the robot movements; and d) the use of monitoring and adaptive control for ensuring that the required weld quality is delivered. The CAD system was chosen to be the basis for the development of the welding off-line programming system. The generation of optimized welding parameters was based on empirical welding models and the robot program generation was based on on-line programming experience. A PC based monitoring and control system was developed to provide on-line position and process control. The position control was carried out by pre-weld adjusting the initial position of the workpiece using a wire touch sensor and on-line adjusting the torch-to-workpiece distance by moving the workpiece based on the information provided by a through-the-arc sensor. The process control was carried out by automatically trimming the welding voltage such that the most stable process could be obtained. The stability of the process was estimated by using previously established monitoring indices. It was assumed that the off-line welding parameter optimization would provide the deposition rate necessary to produce the required weld quality. Successful welding control trials were performed showing the effectiveness of the adaptive control strategy. An off-line programming system has been developed and the programs generated have been tested by simulation. This showed that simulated positioning errors, produced by deliberate wrong path data, were successfully compensated for by the control system developed in this work.
Open Access
Addressing real-time control problems in complex environments using dynamic multi-objective evolutionary approaches
(Cranfield University, 2011-10) Butans, Jevgenijs; Tiwari, Ashutosh; Hughes, Evan J.
The demand for increased automation of industrial processes generates control problems that are dynamic, multi-objective and noisy at the same time. The primary hypothesis underlying this research is that dynamic evolutionary methods could be used to address dynamic control problems where con icting control criteria are necessary. The aim of this research is to develop a framework for on-line optimisation of dynamic problems that is capable of a) representing problems in a quantitative way, b) identifying optimal solutions using multi-objective evolutionary algorithms, and c) automatically selecting an optimal solution among alternatives. A literature review identi es key problems in the area of dynamic multi-objective optimisation, discusses the on-line decision making aspect, analyses existing Multi- Objective Evolutionary Algorithms (MOEA) applications and identi es research gap. Dynamic evolutionary multi-objective search and on-line a posteriori decision maker are integrated into an evolutionary multi-objective controller that uses an internal process model to evaluate the tness of solutions. Using a benchmark multi-objective optimisation problem, the MOEA ability to track the moving optima is examined with di erent parameter values, namely, length of pre-execution, frequency of change, length of prediction interval and static mutation rate. A dynamic MOEA with restricted elitism is suggested for noisy environments.To address the on-line decision making aspect of the dynamic multi-objective optimisation, a novel method for constructing game trees for real-valued multiobjective problems is presented. A novel decision making algorithm based on game trees is proposed along with a baseline random decision maker. The proposed evolutionary multi-objective controller is systematically analysed using an inverted pendulum problem and its performance is compared to Proportional{ Integral{Derivative (PID) and nonlinear Model Predictive Control (MPC) approaches. Finally, the proposed control approach is integrated into a multi-agent framework for coordinated control of multiple entities and validated using a case study of a tra c scheduling problem.
Open Access
Adopting lean manufacturing techniques in small and medium manufacturing enterprises
(Cranfield University, 2010-10) Danielli, Shaun Pau; Nelder, G.
Small and medium sized enterprises (SMEs) form a significant part of national and regional economic prosperity. They strengthen the capacity to generate employment and wealth for national and regional benefit. The importance of SMEs to the prosperity of a society and their contribution to new job creation, coupled with the recognition that they seem to underperform highlights the need to assist this group of companies improve their performance. During the course of this research the author investigated whether SME manufacturing organisations had opportunities to improve productivity and performance, conducted a literature review of the application of cellular one piece flow and then tested a model to implement cellular one piece flow with three SME manufacturing organisations. This thesis establishes that SME manufacturing organisations do have opportunities to improve productivity and performance through cellular one piece flow.
Open Access
The adoption of low-cost low head drip irrigation in small-scale farms in Kenya
(Cranfield University, 2003-09) Kalamwa, Kulecho I.; Weatherhead, E. Keith
Population growth and development will increase the demands on water resources in Africa, and hence there is a need for agriculture to use water efficiently. Drip irrigation is widely promoted for water saving at the farm level. Moreover, it is easily adaptable to small-scale farming common in Africa. The use of low-cost drip irrigation, especially the low-cost medium head (LCMH) drip system, is growing rapidly in some Asian countries. However, the uptake of low-cost drip irrigation in general has been slow in Kenya, which has scarce water for irrigation. Using the theory of the adoption and diffusion of innovation, this research aimed to identify the factors affecting the rate of adoption and continued use of low-cost low head (LCLH) drip irrigation in Kenya. Following a review of experiences of low-cost drip irrigation from India and sub-Saharan Africa, primary information was obtained using informal interviews in a two-phase survey. A total of eighty-six respondents were interviewed in the two phases. Phase 1 examined the factors influencing the adoption of LCLH drip irrigation. The key respondents in phase 1 were irrigation farmers (drip and non-drip), government officials, irrigation industry representatives, and staff of non¬governmental organisations (NGOs). Phase 2 examined the factors affecting discontinuation of LCLH drip irrigation. In phase 2 only LCLH drip irrigation farmers and those who had discontinued using it were interviewed While the low-cost medium head drip irrigation was the dominant irrigation in India, the low-cost low head drip irrigation, gravity fed and in a kit form, was found to be the most common system on smallholder farms in Kenya. The results showed that for the rate of appropriate low-cost drip irrigation uptake to increase in Kenya, it was important to remove political and institutional inhibiting factors dominant during the implementation stages of the innovation-decision process. It was necessary for farmers to have a need to save irrigation water, reliable irrigation water resources, effective water user organisations, efficient marketing facilities, efficient technical support services, relevant cultural background, and good security for the kit. The LCLH drip irrigation kit appeared to have more maintenance problems than the alternative irrigation methods. Furthermore, government policies and extension services as well as irrigation industry efforts appeared limited. It appeared that the technology would most likely be adopted where farmers have a reliable but limited (in volume) water supply.In some situations, the LCLH drip technology, and particularly the smaller (bucket) kits, did not appear to be appropriate and should not be promoted. For other conditions, recommendations were made for helping to overcome the problems identified in the study.The Rogers innovation-decision model was shown to lack sufficient consideration of external factors. A revised model was proposed to suit the conditions of small-scale irrigation technology adoption in less developed countries.
Open Access
Advanced Bearing System for Ultra Precision Plastic Electronics Production Systems
(Cranfield University, 2014-09) Zhao, Gang; Shore, Paul; Morantz, Paul
The aims of this MSc research project are to investigate the application of aluminium for the main components of an ultra-precision spindle defined for use in R2R production systems and to produce a reel to reel rotary aluminium hydrostatic bearing system of high accuracy to meet the demand of manufacturing the flexible displays with an effective production capability for this special kind of film-based product. The original concept design was already finished to manufacture the bearing components and the objective of this project was to test the functionality of this new hydrostatic bearing system. Firstly, theoretical were performed to work out the output responses, including temperature rise, flow rate, load capacity etc., of the hydrostatic bearing system under different input design parameters, including supply pressure, fluid viscosity, the rotational speed etc. Then ANSYS software was used to build a FEA model to simulate the actual working conditions of the hydrostatic bearing system and to obtain the theoretical output parameters, especially the deflection conditions of the bearing shaft. Finally the experimental validation tests were conducted to verify the actual output responses to check correlation with the modelled results.
Open Access
An advanced decision process for capacity expansion in manufacturing networks
(Cranfield University, 2008-04) Julka, Nirupam; Baines, Tim; Tjahjono, Benny
Manufacturing companies develop multiple production sites for various reasons from cheaper labour to access to local markets. Expansion of capacity in such a manufacturing network is a complex decision and requires consideration of multiple factors. Traditionally, industrial decision makers attempt to minimise the cost of expansion and, usually as an afterthought, consider soft factors like manpower availability and logistics connectivity. This approach has gained acceptance as the research community has focused on developing better mathematical representations of the problem rather than investigate the larger decision process. A review of the literature revealed that all existing processes for multi-site capacity expansion decision fail in this way. Therefore, this research sets out to fulfil the needs of practitioners by developing a more complete process for the capacity expansion decision in multi-site manufacturing networks. The research programme consists of five parts. In the first part an extensive literature review is conducted to identify the state-of-the-art in capacity expansion decision processes. Then, in the second part, a representative process is formed and industrially tested. This generates the specifications for an advanced decision process which addresses the shortcomings of the present body of knowledge and is developed in the third part of the research. In the fourth part the advanced decision process is applied in an industrial setting to validate its effectiveness. Finally, in the fifth part the advanced decision process is refined and illustrated. The outcome of this research is an improved decision making capability. The advanced decision process has been both validated and appreciated by industrial practitioners. Specifically the contribution to knowledge is an advanced decision process for capacity expansion in multi-site manufacturing network.
Open Access
Advanced oxidation processes for wastewater reuse - removal of micropollutants
(Cranfield University, 2013-04) James, Christopher P.; Judd, Simon J.
The removal of micropollutants (MPs) from secondary municipal wastewater by an advanced oxidation process (AOP) based on UV irradiation combined with hydrogen peroxide (UV/H2O2) has been assessed through pilot-scale experiments incorporating microfiltration (MF) and reverse osmosis (RO). Tests employed low concentrations of a range of emerging contaminants of concern, and the water quality varied by blending of waters from different sources. Under optimum H2O2 and lamp power conditions, the process achieved >99% removal of N-nitrosodimethylamine (NDMA) and endocrine disrupting compounds (EDCs) from all waters. Pesticide removal, in particular metaldehyde, atrazine and 2, 4 5-T, was dependent on water transmittance (UVT), and levels of Total Organic Carbon (TOC) and other hydroxyl radical (HO.) scavengers. Chloroform, a trihalomethane (THM), was not readily degraded (<10% removal in either stream), as was TOC removal. Further analysis of metaldehyde removal identified UVT, reaction time, and H2O2 dose to be influential parameters in determining degradation as a function of UV dose. In comparison, the impact of H2O2 dose and UVT was negligible on NDMA degradation; removal increased from 89 to >98% on increasing the UV dose from 200 to 680 mJ cm-2 from the MF permeate. Nitrite by-products were observed at elevated levels, promoted by low pH and high UV doses. An operational cost assessment revealed energy consumption to account for 65% with lamp replacement contributing 25%. A comparison of three unit process sequences, based on MF, RO, AOP and activated carbon (AC), revealed MF-RO-AOP to be the most cost effective provided management of the RO concentrate stream incurs no significant cost. Results demonstrated AOPs to satisfactorily reduce levels of the more challenging recalcitrant MPs to meet stringent water quality standards for wastewater reuse, but that practical limitations exist and the cost penalty is significant.
Open Access
Advances in Gas Metal Arc Welding and Application to Corrosion Resistant Alloy Pipes
(Cranfield University, 2010-03) da Costa Pépe, Nuno Vasco; Yapp, David
According to recent estimations, the construction of pipelines will continue to increase during the next thirty years, in particular as a result of oil and gas discoveries in remote locations. Significant advances in welding technology during the last ten years have potential to provide improvements in productivity, quality and structural integrity of pipe girth welds. In this thesis, several new processes Lincoln STT, Lincoln RapidArc, Fronius CMT, Fronius CMT-P and Kemppi FastROOT have been compared the first time to the GMAW-P to understand how these new waveforms operate for pipe welding. The process setting parameters have been analysed to understand their effect on metal transfer and arc stability control, and on bead shape characteristics. Although all waveforms present similar burn-off ratios, individual waveforms differ considerably, and especially the arc voltage waveform. This leads to considerable differences in the mechanism of metal transfer and the stability of the processes under similar experimental conditions. Understanding of these new waveforms in terms of the effect of setting parameters in the mechanism of metal transfer, process stability and melting phenomena provides a basis for assessing the potential of these processes for a range of applications, and in particular application to CRA pipe root welding Since the arc energy is the overall energy delivered from the power source at the contact tip of the torch, and part of that energy is not absorbed by the workpiece, research was performed to measure the process efficiency associated with some of these waveforms and process setting conditions. The study led to a better understanding of the potential errors in calculating process efficiency. The results obtained show that all the short-circuiting waveforms analysed (i.e. CMT, STT and FastRoot) had a similar process efficiency of 90±3%, while pulse spray waveforms (GMAW-P, CMT-P and RapidArc) are characterized by lower process efficiency, approximately 78±3%. The application of these waveforms to the welding a narrow groove pipe with a “J” groove design was investigated. These analyses were focused on the variation of bead shape characteristics and welding quality performance based on the analysis of the conditions that result in lack of penetration and top bead defects, such as lack of side wall fusion or undercutting. It was observed that RapidArc and CMT-P are able to satisfy the quality requirements, i.e. full penetration and absence of defects for the specific conditions described in this thesis. High welding speeds (up to 1m/min) were achieved with these processes, four times the typical speed 0.25m/min. Finally, the shielding gas plays an important role in terms of quality and weld bead performance. This led to an optimization of the shielding gas composition used, based on mixtures of carbon dioxide, argon and helium. Statistical modelling was undertaken to optimize the shielding gas mixtures using RapidArc and CMT-P waveforms. In parallel, a new purging shielding gas device was designed to achieve a weld root free of oxidation.
Open Access
Advances in optical surface figuring by reactive atom plasma (RAP)
(Cranfield University, 2012-10) Castelli, Marco; Shore, Paul; Morantz, Paul
In this thesis, the research and development of a novel rapid figuring procedure for large ultra-precise optics by Reactive Atom Plasma technology is reported. The hypothesis proved in this research is that a metre scale surface with a form accuracy of ~1 μm PV can be figure corrected to 20 – 30 nm RMS in ten hours. This reduces the processing time by a factor ten with respect to state-of-the-art techniques like Ion Beam Figuring. The need for large scale ultra-precise optics has seen enormous growth in the last decade due to large scale international research programmes. A bottleneck in production is seen in the final figure correction stage. State-of-the-art processes capable of compliance with requisites of form accuracy of one part in 108 (CNC polishing, Magneto-Rheological Finishing and Ion Beam Figuring) have failed to meet the time and cost frame targets of the new optics market. Reactive Atom Plasma (RAP) is a means of plasma chemical etching that makes use of a Radio Frequency Inductively Coupled Plasma (ICP) torch operating at atmospheric pressure. It constitutes an ideal figuring alternative, combining the advantages of a non-contact tool with very high material removal rates and nanometre level repeatability. Despite the rapid figuring potential of this process, research preceding the work presented in this manuscript had made little progress towards design and implementation of a procedure for metre-class optics. The experimental work performed in this PhD project was conducted on Helios 1200, a unique large-scale RAP figuring facility at Cranfield University. Characterisation experiments were carried out on ULE and fused silica surfaces to determine optimum process parameters. Here, the influence of power, surface distance, tool speed and surface temperature was investigated. Subsequently, raster-scanning tests were performed to build an understanding on spaced multiple passes ... [cont.].
Open Access
The aeration of clay soils in cricket
(Cranfield University, 2012-05) Parsons, Simon A.; James, Iain; Bartlett, Mark
In the game of cricket good ball-surface interactions are essential and require a hard, flat surface. To achieve this the clay loam soil comprising the pitch is compressed and compacted using a smooth wheeled roller, which when combined with the drying action of the grass plant roots, causing the clay minerals within the soil to shrink, creates a high bulk density, hard surface on which to play. High bulk density soils present difficult growing conditions for plants due to high mechanical resistance, reduced hydraulic conductivity and gas exchange capability. The hydraulic properties and gas exchange capability are linked to the connectivity and tortuosity of the pore network as well as pore size; all of which are diminished by compaction of the soil. Aeration is currently utilised as a tool to ameliorate the negative effects of compaction on the growing environment of the plant roots. Little research exists that describes the actions of aeration in clay loam soils. The current guidelines for aeration and the proof for its efficacy in cricket are based almost entirely on anecdotal evidence. A diverse methodology was used to meet the project objectives. This diversity reflects the broad nature of the expectations of the cricket groundsmen from aeration of pitches as reflected in a survey of current practise undertaken during the project. Novel experimental methods were used to examine the effect of aeration on soil atmospheres in the laboratory and under field conditions. The laboratory experiment revealed that vertically-operated solid tines did significantly increase the rate of diffusion through the soil, however in the field, this rate increase was only apparent after significant rainfall. New methods utilising time-lapse photography and automated image analysis quantified the magnitude of swelling in a range of soils in response to increasing water content over time to a high degree of accuracy. A similar method was employed to examine the shrinkage of the same soils as the water content was reduced, examining not only the magnitude but also the cracking patterns formed. These experiments aimed to examine the soils natural ability to recover from compaction over time. The soils natural ability to recover from compaction through shrink-swell and freeze-thaw was evident in the field trials. These field trials examined five diverse aeration treatments to examine the physical and biological effects they have on the soil. The field trials showed generally small and inconsistent effects on the physical properties of the soil from aeration treatments when compared to the natural processes of shrink-swell and freeze-thaw. One consistent effect from aeration was a 2% reduction in moisture content in one particular soil type. Aeration was found to have no effect on soil microbial biomass nor on soil organic matter content. In a pot experiment examining the effect of aeration in a range of soil densities the total root mass was not diminished by increasing soil density but became increasingly concentrated upwards in the profile. Aeration was found to slightly increase the root mass but only in the highest bulk density treatment (1.90 g cm-3) at depths below 75 mm. A set of guidelines were developed based on the evidence garnered from the experiments with a clearly defined decision process for choosing the most suitable equipment for the treatment aim. It is hoped that these guidelines will provide an informative reference for current and future groundsmen to ensure the optimum use of often scarce and valuable resources when choosing an aeration treatment.
Open Access
Aircraft crash survivability from viscous injury in vertical impacts
(Cranfield University, 2009-04) Barth, Thomas H.; Irving, Phil E.
This research investigated viscous injury from vertical impact loading to determine if it is critical to survivability of aircraft accidents. A unique database was built from autopsy reports and accident investigations combining injury data with the vehicle impact data. Computer models were created and used to assess injury potential. Common design limits and actual crash data from full scale research experiments were used as inputs. The results were analyzed according to published injury thresholds and compared with real accident autopsies to determine the validity of the hypothesis. Heart and Aortic Injury (HAI) has been considered a critical survivability factor through out the history of mechanized transportation. The mechanisms of HAI in the aircraft environment were never well characterized. Automotive research identified important HAI injury mechanisms related to the forward and lateral impact vectors. This research investigated the vertical impact vector. A model was developed to evaluate the biomechanical response of a simplified visco-elastic system, and incorporated into a system model which included the occupant and aircraft seat. This approach was similar to the development of spine injury criteria and provided the advantage of a macro level evaluation of the injury thresholds and assessment of the criticality in survivable accidents. Evaluations of real accidents sustaining HAI characterized a range of impact severity and approximate boundaries for survivability with HAI and internal organ injury. Viscous injury potential from vertical impact was found to be less critical than potential spine injury. Detailed analysis of HAI documented in autopsy reports and the corresponding accident investigations found that HAI was associated with cockpit environmental factors rather than inertial displacement mechanisms. Vertical displacement of the heart due to inertial loads is not a critical factor in survivable accidents given current aircraft technology. Inertial loading to the heart and aorta is a contributory factor for viscous injuries in aircraft accidents.
Open Access
Aluminium-based Coatings for Cadmium Replacement
(Cranfield University, 2008-06) Cardilli , Emanuele; Robinson, M. J.
Cadmium electroplating is widely used in the aerospace industry for the corrosion protection of high strength steels. Cadmium is also used as compatible coating to reduce the galvanic corrosion generated in the assembly of components manufactured with different materials. However, environmental and safety concerns over the high toxicity of cadmium has led to the investigation of suitable replacements. Aluminium coatings are promising coatings for the replacement of electroplated cadmium. Previous studies have shown that the use of SermeTel 984, a commercial aluminium sprayed coating, is beneficial in eliminating the hydrogen direct embrittlement without increasing the risk of re-embrittlement. However, the coating has shown to be prone to passivation in the mild corrosive environment. The addition of active zinc and magnesium particles are thought to avoid the passivation of the aluminium. A range of modified SermeTel 984 coatings, containing 0.5%, 3%, 10% and 50% of zinc, and SermeTel 984 modified with the addition of 30% and 50% of Mg/Al alloy particles in weight have been evaluated as possible alternatives. Chromium free SermeTel 984 and a SermeTel 984 modified with aluminium alloy 7075 particles together with IVD aluminium coatings have also been included in the project. The sacrificial protection of the new coatings has been evaluated together with the associated risk of hydrogen re-embrittlement and compared with the electroplated cadmium. Zinc modified SermeTel 984, containing 1% of zinc and 5% of zinc electroplated aluminium, IVD aluminium and electroplated Zn-Ni coatings have been studied as alternative coatings to cadmium as compatible coatings. Slow strain rate testing has been performed to study the effect of hydrogen on the re- embrittlement of steel substrate as a result of the corrosion of the aluminium-based coatings in 3.5% NaCl. Linear polarisation testing in 3.5% NaCl has been used to evaluate the self-corrosion rates of the coatings; galvanic coupling measurements have been used in the case of steel substrate to evaluate the sacrificial properties or, in the case of bronze/aluminium assembly, to evaluate the compatibility properties of the coatings. Polarisation behaviour tests have been used to study the anodic or cathodic control of the corrosion mechanisms. Total corrosion, calculated as the addition of self-corrosion and galvanic corrosion, has been calculated to evaluate the duration of the coating in service compared to electroplated cadmium.
Open Access
An amperometric enzyme electrode for the detection of L-lactate
(Cranfield University, 1997-06) Selkirk, Jane Yvonne; Turner, Anthony P. F.; Saini, S.
The main tasks of this thesis were to evaluate a number of amperometric enzyme electrode chemistries for the selective and sensitive detection of L-lactate, and apply mass fabrication technologies to reproducibly manufacture sensors in a controllable manner. The sensors studied were based on the use of lactate oxidase with a range of modified-carbon electrodes. Noble metals, hexacyanoferrate (111) or Prussian Blue were used to modify carbon electrodes for the electro-catalytic determination of hydrogen peroxide, the product of the reaction of lactate oxidase with L-lactate. Tetrathiafulvalene was employed as an artificial mediator between the enzyme and the electrode. Polypyrrole was tested as a means of immobilising lactate oxidase and to achieve direct charge transfer to the underlying carbon electrode. The characteristics of the sensor responses to hydrogen peroxide, L-lactate and ascorbate were compared, in relation to the electrochemical electrode area. From this investigation, it was confirmed that screen-printed electrodes were more reproducible to manufacture than hand-fabricated electrodes. For screen-printed rhodinised-carbon electrodes, an operating potential of +400 mV (SCE) was selected. Interference from ascorbic acid and sensitivity to hydrogen peroxide were deten-nined to be 26 gA. mM-' CM-2 and 27 gA. mM-'. CM-2, respectively. Screen-printed carbon electrodes modified with platinum, rhodium or palladium were selected for further investigation. Rhodium on carbon performed the best in ten-ns of sensitivity and selectivity at low potentials, and different formations of rhodium-carbon complexes were studied. Although rhodium electroplated onto carbon screen-printed electrodes was examined, printing inks made from a preformed powder of rhodium on carbon-graphite proved to be the preferred route of electrode fabrication. Screen printing, ink-jet printing and Cavro solution deposition were employed to fabricate the amperometric enzyme electrodes. These sensors were composed of rhodinised carbon and lactate oxidase in a water-based electrode ink with a protective outer membrane layer. Each stage, from ink preparation to membrane composition, was developed empirically. The sensitivity, stability and reproducibility of the working electrode was improved by altering it to a homogeneous ink, consisting of carbon graphite powder, rhodinised carbon powder (5% Rh by weight), hydroxyethyl cellulose (2% w/v) and lactate oxidase in the weight ratio of 2: 8: 18: 1. A layer of cellulose acetate (2% w/v in a 1: 1 solution of acetone to cyclohexanone) and an outer coating of a polyurethane called Pellethane (I% to 4% w/v in dimethyl formarnide and tetrahydrofuran) improved the selectivity, sensitivity and detection range of the sensor, allowing it to operate in physiological solutions with reduced passivation from protein adsorption. The sensor design was revised to allow its passage through a catheter and operation within a blood vessel; it was manufactured on flexible material using screen printing and Cavro solution deposition techniques. These miniature sensors, with a working surface of 0.5 x 15 mm, were capable of linearly measuring lactate up to 3 mM in buffer solutions with an average sensitivity of 44.8 nA. mM-1 L- actate. To test the sensor operation in physiological solutions, a flow injection system was employed. A planar three-electrode card used in this system was manufactured using screen printing and Cavro solution deposition techniques. L-lactate concentrations up to 6.4 mM were sensitively and, after minor correction, accurately determined in undiluted plasma and whole blood samples. This thesis has therefore made progress toward mass fabricating an amperometric enzyme electrode device suitable for the deten-nination of L-lactate concentrations in vitro.
Open Access
Anaerobic Digestion Foaming Causes
(Cranfield University, 2008-10) Ganidi, Nafsika; Tyrrel, Sean; Cartmell, Elise
Anaerobic digestion foaming has been encountered in several sewage treatment plants in the UK. Foaming has raised major concerns for the water utilities due to significant impacts on process efficiency and operational costs. Several foaming causes have been suggested over the past few years by researchers. However, the supporting experimental information is limited and in some cases site specific. The present report aimed to provide a better understanding of the anaerobic digestion foaming problem and to identify the underlying mechanisms of foaming. Field and laboratory investigation identified organic loading as a cause of foaming. Bench scale batch digestion studies in sludge showed that the critical organic loading for foaming was at 2.5 kg VS.m -3 while the 5 kg VS.m -3 resulted in persistent foaming. Moreover, full scale foaming digesters exhibited higher foaming potential in digested sludge under aeration in the laboratory than the full scale non- foaming digesters indicating that the concentration of surface active agents was higher. Further investigation of the effect of the surface active compounds, BSA and n-valeric acid on foaming showed that both compounds induced persistent foaming at all the examined concentrations. Filamentous bacteria contribution to foam initiation and stabilization was considered insignificant, apart from one occasion (FI:5), due to the abundance of filaments in foaming sludge (FI≤3) and their partitioning in foam (FI≤3). Part of the current work also assessed the cost implications of a foaming incident at the full scale. The antifoam cost was found to be of major concern for the water utilities costing between £1.30 and £13.00 per 1000 m 3 of digester volume per day. However, there was no information on biogas and energy loss whereas the information provided on cleaning, maintenance costs and manpower working hours was poor. Thus, the overall cost of a foaming incident at the full scale could not be estimated at this stage.