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Indoor envision system for the visually impaired
Get PDFThis thesis presents a comprehensive assistive technology system, designed and implemented, to support the challenge faced by Visually Impaired (VI) individuals when they enter a new indoor environment. To design such a system, existing similar systems were first reviewed with their features and limitations. The identified limitations of the existing systems motivated the proposed work.The proposed system consists of a compact unit with a camera and accompanying sensors providing the Visually Impaired individual with a convenient and cost-effective solution, unlike the conventional method of using a white cane. The features are developed to ease visualization of the indoor environment for the Visually Impaired individuals and to make them independent of any external assistance in the visualization of the room. The proposed system was compared with similar existing systems. The evaluation was done by comparing accuracy results between the proposed system and existing systems. The proposed system was discussed with the people having visual impairments and was well appreciated. With a new overall system design and implementation, this thesis contributes to the fields of Electronic and Electrical Engineering,Digital Image Processing and Signal Processing.This thesis presents a comprehensive assistive technology system, designed and implemented, to support the challenge faced by Visually Impaired (VI) individuals when they enter a new indoor environment. To design such a system, existing similar systems were first reviewed with their features and limitations. The identified limitations of the existing systems motivated the proposed work.The proposed system consists of a compact unit with a camera and accompanying sensors providing the Visually Impaired individual with a convenient and cost-effective solution, unlike the conventional method of using a white cane. The features are developed to ease visualization of the indoor environment for the Visually Impaired individuals and to make them independent of any external assistance in the visualization of the room. The proposed system was compared with similar existing systems. The evaluation was done by comparing accuracy results between the proposed system and existing systems. The proposed system was discussed with the people having visual impairments and was well appreciated. With a new overall system design and implementation, this thesis contributes to the fields of Electronic and Electrical Engineering,Digital Image Processing and Signal Processing
A chemical approach to regenerating the performance of thermally damaged glass fibres
Get PDFGlass fibre reinforced thermosetting polymers (GRP) have been used in a wide range of applications over the past decades, such as in the production of wind turbine blades. Once these materials reach the end of their life cycle, they are often deposited in landfill sites, a disposal option that is becoming more expensive and environmentally unfriendly. The glass fibres can be recycled from the composite waste by degrading the polymer matrix at elevated temperatures, however this leads to fibres with drastically low mechanical strength. The main objective of this research project was to develop chemical treatments to regenerate the strength of such fibres, to allow their reuse in second life composite materials.In this work, glass fibres were heated in a furnace to mimic thermal recycling conditions, before chemical treatments were applied to regenerate their strength. It was discovered that a short treatment of fibres in hot and concentrated sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution significantly increased their strength, likely due to etching of fibre surface flaws. Interestingly, these treatments had a detrimental effect on the strength of virgin fibres. A kinetic investigation was carried out to determine the etching rate of glass fibres in alkaline solutions. This was achieved by accurately measuring the diameter of individual glass fibres before and after alkaline treatment using a scanning electron microscope.It was found that NaOH solution was more corrosive towards the glass fibres than KOH solution, and that increasing the concentration and temperature of the alkaline solution led to an increase in etching rate.Later in the study, glass fibres were thermally recycled from an end of life wind turbine blade. The recycling procedure involved feeding the downsized blade section into an in house fluidised bed. Fluidised bed recycling is a common thermal recycling technique where elevated temperatures and oxygen lead to degradation of the composite matrix and recovery of the fibrous components. It was found that a short treatment of the recycled fibres in concentrated NaOH solution managed to considerably regenerate their strength. An effort was made in recovering the strength of the fibres under milder alkaline conditions, though the reported strength increase was not as significant. A case study was conducted to determine the industrial feasibility of treating recycled glass fibre in alkaline solution. It was discovered that the costs of solution preparation and processing conditions can be partially offset through charging businesses for collecting their composite waste, and selling the regenerated glass fibres as chopped fibre products.Glass fibre reinforced thermosetting polymers (GRP) have been used in a wide range of applications over the past decades, such as in the production of wind turbine blades. Once these materials reach the end of their life cycle, they are often deposited in landfill sites, a disposal option that is becoming more expensive and environmentally unfriendly. The glass fibres can be recycled from the composite waste by degrading the polymer matrix at elevated temperatures, however this leads to fibres with drastically low mechanical strength. The main objective of this research project was to develop chemical treatments to regenerate the strength of such fibres, to allow their reuse in second life composite materials.In this work, glass fibres were heated in a furnace to mimic thermal recycling conditions, before chemical treatments were applied to regenerate their strength. It was discovered that a short treatment of fibres in hot and concentrated sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution significantly increased their strength, likely due to etching of fibre surface flaws. Interestingly, these treatments had a detrimental effect on the strength of virgin fibres. A kinetic investigation was carried out to determine the etching rate of glass fibres in alkaline solutions. This was achieved by accurately measuring the diameter of individual glass fibres before and after alkaline treatment using a scanning electron microscope.It was found that NaOH solution was more corrosive towards the glass fibres than KOH solution, and that increasing the concentration and temperature of the alkaline solution led to an increase in etching rate.Later in the study, glass fibres were thermally recycled from an end of life wind turbine blade. The recycling procedure involved feeding the downsized blade section into an in house fluidised bed. Fluidised bed recycling is a common thermal recycling technique where elevated temperatures and oxygen lead to degradation of the composite matrix and recovery of the fibrous components. It was found that a short treatment of the recycled fibres in concentrated NaOH solution managed to considerably regenerate their strength. An effort was made in recovering the strength of the fibres under milder alkaline conditions, though the reported strength increase was not as significant. A case study was conducted to determine the industrial feasibility of treating recycled glass fibre in alkaline solution. It was discovered that the costs of solution preparation and processing conditions can be partially offset through charging businesses for collecting their composite waste, and selling the regenerated glass fibres as chopped fibre products
Mapping totally-focused flaw signal variation introduced by interface curvature in ultrasonic array inspection
Get PDF"Engineering Doctorate in Non-Destructive Evaluation" -- title page.This thesis documents the use of the Total Focusing Method (TFM) for performing ultrasonic C-scans of components with irregular and curved surfaces. Ultrasonic inspection depends on an understanding of the link between an ultrasonic indication and flaw size. Some existing methods at Rolls-Royce use target defects of a known size and metal path through flat surfaces to create a Distance Amplitude Curve (DAC) that can be used to accurately size flaws. This study investigated a DAC equivalent for surface-adaptive TFM techniques applied through non-planar surfaces. There was business interest in development of this technique, and also in its delivery by use of general purpose robotic manipulators. Firstly, a robotic inspection process was developed, and a C-scan was conducted on an irregular titanium plate. cueART, software developed by the University of Strathclyde was adapted to create a TFM C-scan. Results were found to be comparable to an existing production inspection process. A series of curved test pieces were manufactured and target Flat-Bottomed Hole (FBH) defects were added. BRAIN, software developed by Bristol university, was adapted and used with equipment at Rolls-Royce to conduct TFM C-scans. DAC curves were generated experimentally for a test inspection, showing convex radii from 10 to 40 mm led to a drop of 2 dB, and concave 10 dB. This was repeated at various depths to produce multiple DAC curves. Modelling techniques for these experimental cases were developed, finding that a 2D finite element model, and 3D CIVA model followed a similar trend to the DAC. Modelling was used to extend results to produce a map of peak flaw signal through a curved surface. An experimental study of flat, rough surfaces showed that an Ra of 12 ฮผm led to a 6.4 dB reduction in peak TFM signal, and13.2 dB reduction in signal to noise ratio.This thesis documents the use of the Total Focusing Method (TFM) for performing ultrasonic C-scans of components with irregular and curved surfaces. Ultrasonic inspection depends on an understanding of the link between an ultrasonic indication and flaw size. Some existing methods at Rolls-Royce use target defects of a known size and metal path through flat surfaces to create a Distance Amplitude Curve (DAC) that can be used to accurately size flaws. This study investigated a DAC equivalent for surface-adaptive TFM techniques applied through non-planar surfaces. There was business interest in development of this technique, and also in its delivery by use of general purpose robotic manipulators. Firstly, a robotic inspection process was developed, and a C-scan was conducted on an irregular titanium plate. cueART, software developed by the University of Strathclyde was adapted to create a TFM C-scan. Results were found to be comparable to an existing production inspection process. A series of curved test pieces were manufactured and target Flat-Bottomed Hole (FBH) defects were added. BRAIN, software developed by Bristol university, was adapted and used with equipment at Rolls-Royce to conduct TFM C-scans. DAC curves were generated experimentally for a test inspection, showing convex radii from 10 to 40 mm led to a drop of 2 dB, and concave 10 dB. This was repeated at various depths to produce multiple DAC curves. Modelling techniques for these experimental cases were developed, finding that a 2D finite element model, and 3D CIVA model followed a similar trend to the DAC. Modelling was used to extend results to produce a map of peak flaw signal through a curved surface. An experimental study of flat, rough surfaces showed that an Ra of 12 ฮผm led to a 6.4 dB reduction in peak TFM signal, and13.2 dB reduction in signal to noise ratio
An investigation into the interaction between hippocampal cells and lymphocytes and its influence on hippocampal network activity
Get PDFWhile the brain is no longer recognized as an immune-privileged site, the role of infiltrating T cells in either homeostasis, protective or pathological conditions is still poorly understood. In the present study, I hypothesize that neuronal-lymphocyte interactions lead to altered hippocampal network activity. Therefore, I aim to investigate contact-dependent and -independent effect(s) of lymphocytes on neuronal and astrocytic activity and synaptic communication. Mouse primary hippocampal cultures were prepared on coverslips and in microfluidic devices. Standard Ca2+ imaging techniques were used to monitor cellular excitability following treatment (1 hour) with naรฏve lymphocytes, lymphocyte conditioned medium (LCM) or recombinant IL-16 (rIL-16; 300 pg mL-1 ). ELISAs confirmed IL-16 in LCM. LCM but not lymphocyte exposure significantly impaired glutamate-induced increases in neuronal intracellular calcium (n[Ca2+]i) compared to HCM control but both were without effect on KCl-induced elevations in n[Ca2+]i and ADP- and glutamate-induced astrocytic [Ca2+]i (a[Ca2+]i) responses. IL-16 levels were elevated in LCM but not during lymphocyte exposure, which indicates that IL-16 is likely to underlie the observed effects with LCM. Interestingly, data has shown a trend towards rIL-16-mediated (300 pg mL-1 ) impaired glutamate-induced n[Ca2+]i increases and was without effect on KCl-induced n[Ca2+]i increases and ADP- and glutamate-induced a[Ca2+]i responses. As mouse hippocampal neurons and astrocytes do not express CD4 the possible effects observed with LCM and IL-16 treatment were considered CD4-independent. Furthermore, my data showsfunctional glutamate-induced neuronal synaptic communication between two mouse networks cultured in microfluidic devices. However, contact-dependent lymphocyte effects on glutamate-induced n[Ca2+]i increases and synaptic communication could not be confirmed in these microfluidic devices. It was shown that lymphocytes do not induce lymphocyte-mediated hippocampal cytotoxicity. VI In conclusion, presented data shows that lymphocytes do not mediate hippocampal cytotoxicity and that their soluble mediators, likely to be IL-16, impair hippocampal Ca2+ signalling via glutamate receptor modulation.While the brain is no longer recognized as an immune-privileged site, the role of infiltrating T cells in either homeostasis, protective or pathological conditions is still poorly understood. In the present study, I hypothesize that neuronal-lymphocyte interactions lead to altered hippocampal network activity. Therefore, I aim to investigate contact-dependent and -independent effect(s) of lymphocytes on neuronal and astrocytic activity and synaptic communication. Mouse primary hippocampal cultures were prepared on coverslips and in microfluidic devices. Standard Ca2+ imaging techniques were used to monitor cellular excitability following treatment (1 hour) with naรฏve lymphocytes, lymphocyte conditioned medium (LCM) or recombinant IL-16 (rIL-16; 300 pg mL-1 ). ELISAs confirmed IL-16 in LCM. LCM but not lymphocyte exposure significantly impaired glutamate-induced increases in neuronal intracellular calcium (n[Ca2+]i) compared to HCM control but both were without effect on KCl-induced elevations in n[Ca2+]i and ADP- and glutamate-induced astrocytic [Ca2+]i (a[Ca2+]i) responses. IL-16 levels were elevated in LCM but not during lymphocyte exposure, which indicates that IL-16 is likely to underlie the observed effects with LCM. Interestingly, data has shown a trend towards rIL-16-mediated (300 pg mL-1 ) impaired glutamate-induced n[Ca2+]i increases and was without effect on KCl-induced n[Ca2+]i increases and ADP- and glutamate-induced a[Ca2+]i responses. As mouse hippocampal neurons and astrocytes do not express CD4 the possible effects observed with LCM and IL-16 treatment were considered CD4-independent. Furthermore, my data showsfunctional glutamate-induced neuronal synaptic communication between two mouse networks cultured in microfluidic devices. However, contact-dependent lymphocyte effects on glutamate-induced n[Ca2+]i increases and synaptic communication could not be confirmed in these microfluidic devices. It was shown that lymphocytes do not induce lymphocyte-mediated hippocampal cytotoxicity. VI In conclusion, presented data shows that lymphocytes do not mediate hippocampal cytotoxicity and that their soluble mediators, likely to be IL-16, impair hippocampal Ca2+ signalling via glutamate receptor modulation
Open innovation adoption from strategy to practice : implications from organizational ambidexterity and dynamic capabilities
Get PDFThis thesis was previously held under moratorium from 19/9/19 to 19/9/21Innovation has long been considered critical to firm success. As one major topic of innovation, open innovation attracts increasing scholarly attention by offering a practical paradigm to organize open ways of innovation. Open innovation accommodates diverse collaborative innovation processes accompanying knowledge exchange at multiple levels within and outside the organization. However, excessive attention on the knowledge exchange aspect of open innovation eclipses the opportunity to investigate organization-level strategic deployment of open innovation. -- The aim of research is set to explore 'How to adopt open innovation from strategy to practice?' Drawing on concepts of organizational ambidexterity and dynamic capabilities, strategic and structured adoption of open innovation is shown to follow the logic from strategy to practice: organizational ambidexterity as strategy, open innovation as practices and dynamic capabilities as the bridge in between. -- To investigate how the logic works, this research conceives the organization as an organism and systematically applies qualitative business research strategy.Abductive reasoning is adopted to facilitate interation between theory and data. Finding and discussion provide empirical evidences to elaborate the logic of open innovation adoption from strategy to practice: 1) strategy and practice, 2) capability and process and 3) from strategy to process through capability. -- Organizational evolution is additionally discussed. This research boasts triple-fold contributions. Theoretically, the original integration of the three concepts addresses the gap of organization-level strategic adoption of open innovation. Methodologically, the adoption of the metaphor of organism offers insightful understanding of organizational reality. Practically, the open innovation adoption framework offers a viable guidance to manage structured adoption of open innovation in the real-world context.Innovation has long been considered critical to firm success. As one major topic of innovation, open innovation attracts increasing scholarly attention by offering a practical paradigm to organize open ways of innovation. Open innovation accommodates diverse collaborative innovation processes accompanying knowledge exchange at multiple levels within and outside the organization. However, excessive attention on the knowledge exchange aspect of open innovation eclipses the opportunity to investigate organization-level strategic deployment of open innovation. -- The aim of research is set to explore 'How to adopt open innovation from strategy to practice?' Drawing on concepts of organizational ambidexterity and dynamic capabilities, strategic and structured adoption of open innovation is shown to follow the logic from strategy to practice: organizational ambidexterity as strategy, open innovation as practices and dynamic capabilities as the bridge in between. -- To investigate how the logic works, this research conceives the organization as an organism and systematically applies qualitative business research strategy.Abductive reasoning is adopted to facilitate interation between theory and data. Finding and discussion provide empirical evidences to elaborate the logic of open innovation adoption from strategy to practice: 1) strategy and practice, 2) capability and process and 3) from strategy to process through capability. -- Organizational evolution is additionally discussed. This research boasts triple-fold contributions. Theoretically, the original integration of the three concepts addresses the gap of organization-level strategic adoption of open innovation. Methodologically, the adoption of the metaphor of organism offers insightful understanding of organizational reality. Practically, the open innovation adoption framework offers a viable guidance to manage structured adoption of open innovation in the real-world context
Development and validation of a novel hybrid CFD slurry model
Get PDFErosion from slurry flows is a large problem in the mining and oil and gas industries, hence the interest from Weir group. Centrifugal slurry pumps manufactured by the Weir group are considered to be some of the world's best, however the harsh environments they operate in can erode hardened steel parts in a matter of weeks. One way to mitigate the damage caused to the parts is better design. This is achieved by simulating the flow with computational fluid dynamics (CFD), using a two phase model: one phase for the fluid, one phase for the particles.;The two phase models can, broadly speaking, be separated into two categories: Euler-Euler (EE), and Euler-Lagrange (EL). EE models the fluid and particles as two continua, is fast to run, but lacks particle impact data which is required for erosion modelling. EL models a fluid phase and a particulate phase, is more computationally expensive than the EE model, but has the benefit of having particle impacts at the wall.;A hybrid slurry model was developed combining both EE and EL models, taking advantage of each model's strengths. The hybrid model proved that a combined EE/EL solver was capable of modelling slurry flows in less time than a pure EL model, but with more particle impact data at the wall than a EE model. Issues with combining two computational models in one domain were identified and overcome, buy including a transition baffle, where the solver changed from EE to EL.;Experiments were carried out to validate the computational simulation results on a submerged jet impingement test. Particle image velocimetry was carried out to obtain data from the experiments, and images were correlated to output particle velocity data.Erosion from slurry flows is a large problem in the mining and oil and gas industries, hence the interest from Weir group. Centrifugal slurry pumps manufactured by the Weir group are considered to be some of the world's best, however the harsh environments they operate in can erode hardened steel parts in a matter of weeks. One way to mitigate the damage caused to the parts is better design. This is achieved by simulating the flow with computational fluid dynamics (CFD), using a two phase model: one phase for the fluid, one phase for the particles.;The two phase models can, broadly speaking, be separated into two categories: Euler-Euler (EE), and Euler-Lagrange (EL). EE models the fluid and particles as two continua, is fast to run, but lacks particle impact data which is required for erosion modelling. EL models a fluid phase and a particulate phase, is more computationally expensive than the EE model, but has the benefit of having particle impacts at the wall.;A hybrid slurry model was developed combining both EE and EL models, taking advantage of each model's strengths. The hybrid model proved that a combined EE/EL solver was capable of modelling slurry flows in less time than a pure EL model, but with more particle impact data at the wall than a EE model. Issues with combining two computational models in one domain were identified and overcome, buy including a transition baffle, where the solver changed from EE to EL.;Experiments were carried out to validate the computational simulation results on a submerged jet impingement test. Particle image velocimetry was carried out to obtain data from the experiments, and images were correlated to output particle velocity data
Silk : a biopolymer for engineering nanoparticles
Get PDFSilk from Bombyx mori has a robust clinical track record for load bearing applications. It was hypothesized that the biopolymer silk would also have the potential to generate nanoparticles. Therefore, the aim of this thesis was to manufacture and assess these silk nanoparticles for drug delivery. First, silk nanoparticles were produced from aqueous silk stock by nanoprecipitation. The resulting nanoparticles were then surface grafted with polyethylene glycol (PEG), yielding nano-sized particles (104 to 116 nm) with a negative zeta potential (-56 to -46 mV). PEGylated silk nanoparticles showed a reduced macrophage response, high aqueous stability but low drug loading capacity. The drug loaded PEGylated silk nanoparticles showed improved cytotoxicity, cellular uptake and intracellular dynamics in cancer cells (Chapter 2). Next, the fate of native and PEGylated silk nanoparticles during various enzyme treatments was investigated to demonstrate the elimination of nanoparticles after administration. Native and PEGylated silk nanoparticles were degraded in protease enzymes in vitro, but showed faster degradation in protease XIV (degraded after a 1-day treatment) and slower degradation in papain and ex vivo lysosomal enzymes (degraded after a 5-day treatment) (Chapter 3). Next, the NanoAssemblrTM microfluidic system was exploited to manufacture silk nanoparticles. Silk nanoparticles were generated using the commercial microfluidic chip that allowed rapid mixing of both the aqueous silk solution and the organic solvent.;This microfluidic system allowed tuning of silk nanoparticle characteristics through adjusting processing parameters such as the total flow rate, the total flow rate ratio and solvent selection (Chapter 4). Finally, computational modelling was applied to better understand the impact of silk conformation and its subsequent interaction with the model drug doxorubicin at the atomic level. Well-tempered metadynamics, an enhanced sampling method for molecular dynamics simulations was used to explore the free energy surface of an amorphous-crystalline silk model structure in water. Next, silk with optimised secondary structures were used to study the interaction of the model drug doxorubicin at both pH 4 and 7.4. Here, the N-terminus was the predominant domain responsible for drug loading and release (Chapter 5). Overall, this thesis demonstrated that silk is a versatile biopolymer to generate nanoparticles for drug delivery (Chapter 6).Silk from Bombyx mori has a robust clinical track record for load bearing applications. It was hypothesized that the biopolymer silk would also have the potential to generate nanoparticles. Therefore, the aim of this thesis was to manufacture and assess these silk nanoparticles for drug delivery. First, silk nanoparticles were produced from aqueous silk stock by nanoprecipitation. The resulting nanoparticles were then surface grafted with polyethylene glycol (PEG), yielding nano-sized particles (104 to 116 nm) with a negative zeta potential (-56 to -46 mV). PEGylated silk nanoparticles showed a reduced macrophage response, high aqueous stability but low drug loading capacity. The drug loaded PEGylated silk nanoparticles showed improved cytotoxicity, cellular uptake and intracellular dynamics in cancer cells (Chapter 2). Next, the fate of native and PEGylated silk nanoparticles during various enzyme treatments was investigated to demonstrate the elimination of nanoparticles after administration. Native and PEGylated silk nanoparticles were degraded in protease enzymes in vitro, but showed faster degradation in protease XIV (degraded after a 1-day treatment) and slower degradation in papain and ex vivo lysosomal enzymes (degraded after a 5-day treatment) (Chapter 3). Next, the NanoAssemblrTM microfluidic system was exploited to manufacture silk nanoparticles. Silk nanoparticles were generated using the commercial microfluidic chip that allowed rapid mixing of both the aqueous silk solution and the organic solvent.;This microfluidic system allowed tuning of silk nanoparticle characteristics through adjusting processing parameters such as the total flow rate, the total flow rate ratio and solvent selection (Chapter 4). Finally, computational modelling was applied to better understand the impact of silk conformation and its subsequent interaction with the model drug doxorubicin at the atomic level. Well-tempered metadynamics, an enhanced sampling method for molecular dynamics simulations was used to explore the free energy surface of an amorphous-crystalline silk model structure in water. Next, silk with optimised secondary structures were used to study the interaction of the model drug doxorubicin at both pH 4 and 7.4. Here, the N-terminus was the predominant domain responsible for drug loading and release (Chapter 5). Overall, this thesis demonstrated that silk is a versatile biopolymer to generate nanoparticles for drug delivery (Chapter 6)
An integrated framework for finite element modelling of ultrasonic inspections of carbon fibre reinforced polymer components
No full textOver the last decade there has been a vast increase in the use of composite materials in many engineering aspects. This increase is due to their ability to provide increased mechanical strength while also yielding weight savings in structures. Not only can composites be manufactured to create complex geometry components, their layup can be designed to provide optimum strength and stiffness.Carbon Fibre Reinforced Polymer (CFRP) composite materials pose a challenge for ultrasonic Non Destructive Evaluation (NDE) inspections due to their anisotropic material properties and often complex morphology.This Thesis develops an integrated framework to allow for accurate Finite Element Analysis (FEA) simulations of CFRP components to be constructed. The developed framework can generate the CFRP model geometry from a range of different sources. This enables the ability to construct models based on the design specification of the component, through scripting or importing of component design information, as well as creating models based on their real structure, from images taken from micrographs or X-Ray CT data.;This allows for ultrasonic NDE inspections to be simulated to develop a better understanding of inspection performance, as well as act as a tool to aid inspection design.A parametric study for the inspection of a flat CFRP component is presented to demonstrate the benefit of simulation to aid the understanding of the ultrasonic response and ability to optimise the inspection setup. Further work focuses on the simulation of inspections of tapered geometry components. This adds an additional level of complexity to the inspection and FEA simulation is shown to be an effective technique to optimise specific inspection parameters. Importantly,inspection amplitude maps are used as a tool, both to understand the limitations of an inspection configuration, and to develop new inspection approaches.Over the last decade there has been a vast increase in the use of composite materials in many engineering aspects. This increase is due to their ability to provide increased mechanical strength while also yielding weight savings in structures. Not only can composites be manufactured to create complex geometry components, their layup can be designed to provide optimum strength and stiffness.Carbon Fibre Reinforced Polymer (CFRP) composite materials pose a challenge for ultrasonic Non Destructive Evaluation (NDE) inspections due to their anisotropic material properties and often complex morphology.This Thesis develops an integrated framework to allow for accurate Finite Element Analysis (FEA) simulations of CFRP components to be constructed. The developed framework can generate the CFRP model geometry from a range of different sources. This enables the ability to construct models based on the design specification of the component, through scripting or importing of component design information, as well as creating models based on their real structure, from images taken from micrographs or X-Ray CT data.;This allows for ultrasonic NDE inspections to be simulated to develop a better understanding of inspection performance, as well as act as a tool to aid inspection design.A parametric study for the inspection of a flat CFRP component is presented to demonstrate the benefit of simulation to aid the understanding of the ultrasonic response and ability to optimise the inspection setup. Further work focuses on the simulation of inspections of tapered geometry components. This adds an additional level of complexity to the inspection and FEA simulation is shown to be an effective technique to optimise specific inspection parameters. Importantly,inspection amplitude maps are used as a tool, both to understand the limitations of an inspection configuration, and to develop new inspection approaches
Laser induced incandescence imaging for the investigation of soot formation in laminar flames
Get PDFThis work has been aimed at applying laser induced incandescence imaging for the measurement of soot concentration within a variety of novel flame sources and setups. Laser induced incandescence (LII) is an optical technique used in laser diagnostics to measure soot volume fraction and estimate particle size in-situ. Using imaging to measure LII allows for a range of combustion environments to be investigated and soot volume fractions to be measured. An experimental methodology had to be setup to measure the LII signal using a Nd:YAG laser, ICCD camera and flat flame burner and calibrated along with another optical technique known as extinction. This allowed for the soot volume fraction to be calibrated and measured and this gives the standard case for calibrating other measurements in different flames.From burner setup it is possible to change the boundary temperature of the flame. It was thought that by changing this temperature it would be possible to change the soot concentration within the flame. However, using LII imaging it was shown that despite this change in temperature the soot volume fraction remains the same, this was also eventually found to be the case when modelling these types of flames. This gives confidence in different experimental setups between groups can be used for comparison.;The burner being characterised by a standard setup allows for comparison when using a different excitation source, a long-pulsed fibre laser. Using a long pulse fibre laser has benefits and it is shown in this work that it is possible to get a comparable result with LII centre line height above burner (HAB) profiles matching. Modelling also allows for comparisons and understanding on how the laser temporal and spatial profile can affect the LII signal.The rise of the interest in sustainable energy generation has led to the increase of using alternative fuel sources such as biofuels. Using the method developed it was possible to record soot volume fraction images within a wick diffusion flame which used a selection of biofuels and show improvement on previously published temporal profiles produced in these flames. The sooting propensity of each fuel was able to be characterised more accurately using spatially resolved profiles over temporally measured profile.This work has been aimed at applying laser induced incandescence imaging for the measurement of soot concentration within a variety of novel flame sources and setups. Laser induced incandescence (LII) is an optical technique used in laser diagnostics to measure soot volume fraction and estimate particle size in-situ. Using imaging to measure LII allows for a range of combustion environments to be investigated and soot volume fractions to be measured. An experimental methodology had to be setup to measure the LII signal using a Nd:YAG laser, ICCD camera and flat flame burner and calibrated along with another optical technique known as extinction. This allowed for the soot volume fraction to be calibrated and measured and this gives the standard case for calibrating other measurements in different flames.From burner setup it is possible to change the boundary temperature of the flame. It was thought that by changing this temperature it would be possible to change the soot concentration within the flame. However, using LII imaging it was shown that despite this change in temperature the soot volume fraction remains the same, this was also eventually found to be the case when modelling these types of flames. This gives confidence in different experimental setups between groups can be used for comparison.;The burner being characterised by a standard setup allows for comparison when using a different excitation source, a long-pulsed fibre laser. Using a long pulse fibre laser has benefits and it is shown in this work that it is possible to get a comparable result with LII centre line height above burner (HAB) profiles matching. Modelling also allows for comparisons and understanding on how the laser temporal and spatial profile can affect the LII signal.The rise of the interest in sustainable energy generation has led to the increase of using alternative fuel sources such as biofuels. Using the method developed it was possible to record soot volume fraction images within a wick diffusion flame which used a selection of biofuels and show improvement on previously published temporal profiles produced in these flames. The sooting propensity of each fuel was able to be characterised more accurately using spatially resolved profiles over temporally measured profile
Theory and numerical modelling of dynamic ice-structure interaction for ice-induced vibrations
Get PDFThis PhD work is done as a trilogy. In the first stage, a dynamic single degree-of-freedom ice-structure interaction model is developed based on a novel physical mechanism combination between self-excited vibration and forced vibration. Van der Pol equation, together with ice stress-strain rate curve and ice-velocity failure length are coupled to model the internal fluctuating nature of ice force in conjunction with the relative velocity caused by the structure as an external effect.;Three basic modes of response were reproduced, such as intermittent crushing, frequency lock-in and continuous crushing. The results are in good match with experimental data at different ice velocities and different structural stiffnesses. Ice force frequency lock-in phenomenon during ice-induced vibrations (IIV) is also observed.;In the second stage, analysis on physical mechanism of ice-structure interaction is presented based on feedback mechanism and energy mechanism, respectively. Internal effect and external effect from ice and structure were both explained in the feedback branch. Based on reproduced results, energy exchanges at different configurations are computed from the energy conservation using the first law of thermodynamics. A conclusion on the predominant type of vibration when the ice velocity increases during the interaction process is forced, self-excited and forced in each three modes of responses.;Ice force variations also shows that there is more impulse energy during the lock-in range. Moreover, IIV demonstrates an analogy of friction-induced self-excited vibration. The similarity between stress-strain curve and Stribeck curve shows that static and kinetic friction force variations are attributed to ice force characteristic, and can be used to explain the lower effective pressure magnitude during continuous crushing than the peak pressure during intermittent crushing.;In the third stage, a two-dimensional non-simultaneous ice failure model is developed.The concept of multiple ice failure zones is proposed to fulfil non-simultaneous crushing characteristics. The size of ice failure zone is assumed to become smaller with increasing ice velocity, which increases the occurrence of non-simultaneous ice failures. Similarly, the decreasing size of ice failure zone as velocity increases is explained as the reason of different ice failure modes shifting from large-area ductile bending to small-area brittle crushing.;In addition, an analysis of the ice indentation experiments indicates that the mean and minimum effective pressure have an approximately linear relationship with ice velocity, which testified the assumption on variations of ice failure zone in the model. The simulation results from a series of 134 demonstration cases show that the model is capable of predicting results at different ice velocities, structural widths and ice thicknesses.;To sum up, this Van der Pol based model is more powerful than the others in kind by far because of its accurate results, wide applicability and novel physical mechanism behind. Thus, the numerical models produced as part of this research can be helpful in ice failure analysis and in the design of ice-resistant structures.This PhD work is done as a trilogy. In the first stage, a dynamic single degree-of-freedom ice-structure interaction model is developed based on a novel physical mechanism combination between self-excited vibration and forced vibration. Van der Pol equation, together with ice stress-strain rate curve and ice-velocity failure length are coupled to model the internal fluctuating nature of ice force in conjunction with the relative velocity caused by the structure as an external effect.;Three basic modes of response were reproduced, such as intermittent crushing, frequency lock-in and continuous crushing. The results are in good match with experimental data at different ice velocities and different structural stiffnesses. Ice force frequency lock-in phenomenon during ice-induced vibrations (IIV) is also observed.;In the second stage, analysis on physical mechanism of ice-structure interaction is presented based on feedback mechanism and energy mechanism, respectively. Internal effect and external effect from ice and structure were both explained in the feedback branch. Based on reproduced results, energy exchanges at different configurations are computed from the energy conservation using the first law of thermodynamics. A conclusion on the predominant type of vibration when the ice velocity increases during the interaction process is forced, self-excited and forced in each three modes of responses.;Ice force variations also shows that there is more impulse energy during the lock-in range. Moreover, IIV demonstrates an analogy of friction-induced self-excited vibration. The similarity between stress-strain curve and Stribeck curve shows that static and kinetic friction force variations are attributed to ice force characteristic, and can be used to explain the lower effective pressure magnitude during continuous crushing than the peak pressure during intermittent crushing.;In the third stage, a two-dimensional non-simultaneous ice failure model is developed.The concept of multiple ice failure zones is proposed to fulfil non-simultaneous crushing characteristics. The size of ice failure zone is assumed to become smaller with increasing ice velocity, which increases the occurrence of non-simultaneous ice failures. Similarly, the decreasing size of ice failure zone as velocity increases is explained as the reason of different ice failure modes shifting from large-area ductile bending to small-area brittle crushing.;In addition, an analysis of the ice indentation experiments indicates that the mean and minimum effective pressure have an approximately linear relationship with ice velocity, which testified the assumption on variations of ice failure zone in the model. The simulation results from a series of 134 demonstration cases show that the model is capable of predicting results at different ice velocities, structural widths and ice thicknesses.;To sum up, this Van der Pol based model is more powerful than the others in kind by far because of its accurate results, wide applicability and novel physical mechanism behind. Thus, the numerical models produced as part of this research can be helpful in ice failure analysis and in the design of ice-resistant structures
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