To see the other types of publications on this topic, follow the link: Mining engineering. Metallurgy.
Dissertations / Theses on the topic 'Mining engineering. Metallurgy'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Mining engineering. Metallurgy.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Soejadi, Prijoko Prajitnoadi. "Participatory ergonomics in Indonesian tin mining." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52989/.
Full textAbstract:
Thousands of employees in small and medium-sized enterprises (SMEs) in Indonesia’s tin mining industry are working in dangerous environments without an adequate safety and health protection programme. Occupational safety (OS) has become a primary focal point when it comes to preventing dangerous incidents. Such incidents can lead to serious injuries and fatalities, particularly given that mining involves dangerous and high-risk activities, for example, in onshore tin mining, working in muddy areas with heat, humidity and a risk of landslide. Studies addressing the health and safety domain in Indonesia and the mining sector have the least number of ergonomics applications. The research examined the existing OS of a state-owned tin company, namely PT Timah, in Indonesia. The company has a relatively good level of experience in practising tin mining operations, and also employs occupational safety programmes. For approximately a decade, this company has collaborated with 16 private onshore SMEs which work in more than 400 locations under the PT Timah cooperation scheme. Despite applying OS and a health programme in the main company, the same programme has not been included in the tin mining operation cooperation scheme that regulates the rights and obligations of SMEs. This thesis examines the possibilities of using a well-established ergonomics approach and adapting it so that it is more frequently accepted and embraced in Indonesia. The research is focused on the participatory ergonomics (PE) approach as applied to SMEs. Postal data reviews, interviews and observation methods were used to examine the current status of OS in the Indonesian tin mining industry. The scenario-based design (SBD) method was used to investigate the acceptability of PE, while the two-round Delphi technique was applied to reach a consensus on the practical implementations of PE solutions. There is positive acceptance of PE among workers in Indonesian tin mining companies. Regular working safety dissemination through a kinship approach and specific safety training is recommended for resolving communication, cultural and knowledge issues related to OS. In addition to this, a consensus was reached on proposed solutions regarding the implementation of PE within the Indonesian tin mining industry, such as evaluation of the remuneration and bonus system, employing the train-the-trainer programme, and the OSH reporting system.
2
Ero-Phillips, Olubayode Oladiran. "Development of bi- and multicomponent fibres for tissue engineering by electrospinning." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3587/.
Full textAbstract:
This project investigated the possibility of tailoring the crystallinity of electrospun fibres (crystallinity studies), and the electrospinning of bi- and multicomponent scaffolds of PLLA. During the crystallinity studies, the effects of various electrospinning process parameters on the crystallinity of electrospun poly(L-lactic acid) (PLLA) fibres were investigated. It was observed that the electrospun fibres had crystallinities between 23 and 46% while that for the as-received granule was 37%, suggesting that the crystallinity of electrospun fibres can be controlled by optimizing the electrospinning process. These results showed that the degree of crystallinity of the electrospun fibres decreased with increasing the polymer solution concentration. Furthermore, an optimum electrospinning voltage at which the maximum degree of crystallinity can be obtained was observed. Finally, bi-component scaffolds based on PLLA and gelatin were electrospun. Multicomponent scaffolds based on PLLA, gelatin and hydroxyapatite (HA) were electrospun followed by electrospraying of the HA phase. Blending gelatin with PLLA resulted in an approximate 50% decrease in fibre diameter. Biocompatibility studies revealed that all scaffolds permitted cell attachment with best results observed on the PLLAGel-HA scaffolds. This was attributed to the exposed HA particles on the surface of the PLLAGel-HA scaffolds which promoted better binding with integrins for osteoconductivity.
3
Yünel, Ufuk. "A new concept on sampling systems by air cannon application." Ankara : METU, 2004. http://etd.lib.metu.edu.tr/upload/12604750/index.pdf.
Full text
4
Güngör, Alper. "Occupational health and safety management tool." Ankara : METU, 2004. http://etd.lib.metu.edu.tr/upload/12604694/index.pdf.
Full textAbstract:
Thesis (Ph. D.)--Middle East Technical University, 2004.Keywords: Accident Report Form, Accident Database, Occupational Diseases and Mine Accidents, Accident Reporting System, Health and Safety Management Tool.
5
Mutlu, Yakıcı İçli Supervisor :. Güyagüler Tevfik. "A study on the application of e-commerce in Turkish mining industry." Ankara : METU, 2005. http://etd.lib.metu.edu.tr/upload/12605903/index.pdf.
Full textAbstract:
Thesis (M.S.) -- Middle East Technical University, 2005.Keywords: e-commerce, mining sector, road map for e-commerce, strategy for e-commerce, steps of e-commerce, stages of e-commerce, application of e-commerce
6
Banisi, Samad. "An investigation of the behaviour of gold in grinding circuits." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22400.
Full textAbstract:
A 7.6 cm (3") Knelson concentrator was used to estimate free gold content in samples extracted from industrial grinding and gravity circuits. Its recovery was comparable with that of amalgamation and the Mozley Laboratory Separator (MLS). It was then used for a study on gold grinding and classification behavior.Laboratory studies of monosized gold and silica showed that gold produces fewer fines upon grinding: 75% of the mass reports to the next Tyler class, as opposed to 45% for silica. Disappearance from the monosized class (840-1200 $ mu$m) follows first order kinetics for both minerals. However, the rate constant of gold was five to six times lower than that of silica, and folding predominated over actual breakage. Folding yields either spherical or cylindrical particles which flatten upon additional impacting.
Smearing of gold onto silica and embedding of silica into gold flakes were observed. It was postulated that gold smearing can lead to metallurgical losses in flotation circuits. A gravity circuit could then increase overall gold recovery.
The Knelson concentrator was used to study the behavior of gold in the Hemlo mill grinding circuit. The ratio of the selection function of ore to gold increased from 6 at 50-100 $ mu$m to 20 at 500-1000 $ mu$m. In the primary cyclones, gold's cut size was much finer than the ore, 20 vs. 57 $ mu$m.
7
Marchese, Mecklenburg Mario. "Hydrodynamic study of a downwards concurrent bubble column." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61167.
Full textAbstract:
The hydrodynamics of the downwards concurrent flotation column (CDFC) of the Jameson design has been studied. The effect of operating variables on the gas holdup in two- and three-phase mixtures was measured. To measure gas holdup, the isolating technique, conductivity and pressure techniques were employed. Gas fractions between 10 and 65% were achieved. These high holdups are a consequence of bubbles being forced downwards against their buoyancy. The high gas fraction may account for the fast flotation claimed for this cell.The conductivity technique using Maxwell's equation gave a maximum error of 6%, in both two- and three-phase systems (considering the water-solids mixture as one phase).
The drift flux model was applied to try to correlate the data. Both two- and three-phase systems showed consistent trends. The model was used to estimate bubble size. In the Richardson and Zaki equation the m factor was in the range 2.9 to 3.1. A dimensionless drift flux was defined assuming $m=3$ which fitted the data. For three-phase systems, however, the results predicted a trend in bubble size that seemed opposite to observation. (Abstract shortened by UMI.)
8
Xiao, Jie 1964. "Testing a new gold centrifugal concentrator." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20932.
Full textAbstract:
A new gold centrifugal concentrator, the Falcon SuperBowl, was tested both at plant and laboratory scales to assess its ability to recover gold from grinding circuits.The performances of a 21-in SuperBowl (SB21) at Mineral Hill and New Britannia Mines showed that it could recover gravity recoverable gold (GRG) of all sizes, especially below 25 mum at Mineral Hill Mine.
Three types (to test the effect of gangue density and size distribution) of synthetic feeds were used to characterize a laboratory 4-in SuperBowl (SB4) as a function of feed rate and fluidization water flow rate.
A 20-in Knelson Concentrator and a shaking table were further tested in this program with the samples extracted from Casa Berardi and Mineral Hill Mine, respectively. The 30-in Knelson was tested at two different conditions to assess the impact of fluidization water flow rate and explore the importance of cycle time. (Abstract shortened by UMI.)
9
Bogusz, Edwina J. "The mechanism of the depressant action of dextrin on pyrite." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23254.
Full textAbstract:
The separation of minerals by flotation depends on the effectiveness of the reagents used. The performance of depressants is paramount in rejecting the undesirable minerals while maintaining acceptable recoveries of the desired mineral. Iron-bearing minerals are the main contaminants in many ores: their removal is critical. Several different types of depressants have been used for this purpose, many of which are toxic. A shift has been made toward more environmentally friendly reagents including starch and dextrin.The purpose of this thesis was to determine the depression mechanism of dextrin on pyrite. A number of techniques were applied to give insight into the mechanism, including adsorption studies, microflotation tests, and solution and surface analyses. It was revealed that dextrin only adsorbed on mineral surfaces that contained some metal ionic sites. The degree of adsorption depended on the nature of the metal species, with lead being more reactive than iron. Dextrin was able to depress pyrite, regardless of whether dextrin adsorbed or not; however, adsorbed dextrin was more effective. It appeared as if dextrin inhibited the formation of dixanthogen on the surface, which could lead to reduced floatability of pyrite. Finally, it was observed that over time, adsorbed dextrin underwent a conformational change on the surface of the mineral. This change permitted a greater amount of xanthate to adsorb on the mineral.
10
Sedore, Laila. "MgO rejection from Birchtree ore at Inco's Manitoba division." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81566.
Full textAbstract:
Birchtree is an ultramafic ore body and prior to 2003, represented one third of the production for Inco's Thompson operation. The ultramafic host rocks are high in MgO which, when processed through the smelter, promotes problems in the roasters and converters due to the high liquidus temperature. In October 2003, production from Birchtree mine ramped up to more than half of the total feed to the mill. The mill cannot produce a suitable concentrate for the smelter with current circuit configuration and operating practices. The target for the mill was to produce a nickel concentrate with less than 3% MgO.Continuous mini flotation cells were used to explore processing options. Two campaigns were carried out. The first looked at rejecting the magnesium silicate minerals with the use of reagents from the rougher and scavenger concentrates. Reagents included sodium silicate, guar gum and two types of CMC. Results indicated that current plant practice of CMC addition to the scavenger circuit favours minimizing MgO grade in concentrate.
The second campaign focused on rejecting MgO minerals from the rougher-cleaner concentrate with the use of a dilute CMC solution. Flotation retention time, CMC dosage rate, and conditioning time, were varied. Results indicate that 0.1 g CMC per kilogram of solid in slurry produced a concentrate grading <3.0% MgO.
11
Vincent, Frédérique. "A comparison of Knelson concentrator and jig performance for gold recovery /." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21333.
Full textAbstract:
A 7.6 cm Laboratory Knelson Concentrator was used to evaluate the performance of one jig circuit (Snip Operation), four Knelson Concentrators circuits (Meston, Est Malartic, Aurbel and Hemlo) and one classification circuit (Agnico-Eagle). To determine the size-by-size unit performance of all units, total and gravity recoverable gold contents were measured in the feed, concentrate, tails, underflow and overflow. Sample dilution with silica was used as a tool to enhance LKC recovery in samples with a high sulphide content.The data generated from the Knelson and the jig was used in a model designed to simulate an actual grinding and gravity circuit, and to predict its GRG recovery. It describes gold liberation, breakage and classification behaviour, and the GRG recovery performance curve of the chosen gravity unit. The simulation of the Snip circuit reproduced the recoveries obtained at the plant, and predicted that the use of a 20" Knelson, replacing the jig, would bring the recovery from 3 3% up to 43%. (Abstract shortened by UMI.)
12
Khoshrou, Seyed Hassan. "Theoretical and experimental investigation of wall-control blasting methods." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40161.
Full textAbstract:
Overbreak and damage to rock walls is one of the most serious problems encountered in blasting operations. Several techniques have been developed to control the undesirable effects of rock blasting. These techniques are collectively known as wall-control blasting methods.The stress distribution around pressurized holes has been numerically evaluated, in order to analyze the mechanism of wall-control blasting methods. The effect of blast geometry and the role of discontinuity on this stress field has also been studied in detail. The results obtained by numerical modelling have been verified by controlled blasting experiments, and further supported by analysis of existing roadcuts on a large scale.
It was found that the mechanism of wall-control blast can be explained by the collision and superposition of the stresses between the holes. A narrow fracture zone between the holes was produced by tensile stresses on the centreline. It is neither necessary nor realistic to assume onset of fractures at the midpoint between holes by reinforcement of the stresses from each hole.
The analysis shows that a burden can be defined as being infinite when the ratio of that to the spacing is greater than unity. For pre-split blasting (infinite burden) in an isotropic and homogeneous material the hole separation could range up to 15 borehole diameters. The decoupling ratio between the explosive charge and the borehole diameter should be smaller than 0.5. This ratio would generally be between 0.2 and 0.3 for pre-splitting (infinite burden), and between 0.3 and 0.4 in the presence of a free face.
A discontinuity parallel to the free face and located at the back of the holes causes high stress levels between the discontinuity and the boreholes, resulting is a shattered one in this region. The presence of a similar discontinuity at the front of the holes leads to considerable overbreak and development of an undamaged "hump" of rock between holes. The effect of a discontinuity oriented normal to the centreline at the midpoint between holes has minimal effect on the blast results. As the angle of the discontinuity with the free face decreases from 90$ sp circ,$ the damage zone between the holes and the discontinuity increases, and the shape of the final wall changes from a smooth face to a corrugated shape. A closed-discontinuity or an open discontinuity cemented with strong filling materials has little effect on the results of the blast. However, as the width of the discontinuity increases, the size of the damage zone also increases. An open discontinuity, 50 mm wide or more, plays a role similar to a free face.
In roadcut blast design, hole deviation is a key parameter in determining the quality of the face. However, consistent hole deviation in the same direction has minimal effect in the result of the blast. This type of deviation is usually associated with bedded rocks, with alternating bands of soft and hard rock on the face. The degree of deviation is dependent, amongst other factors, on orientation, thickness, frequency and the position of these bands.
13
Ward, Andrew. "Development of a lead-free aluminium bearing alloy using powder metallurgy manufacturing techniques." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6418/.
Full textAbstract:
This study, completed with the University of Birmingham, was sponsored by Controls and Data Services (CDS) and the Engineering and Physical Sciences Research Council (EPSRC). A range of materials and processes were evaluated with the aim of producing a lead-free, monolithic, machinable plain bearing to replace the leaded bronze gear pump bearings currently used. The primary alloys investigated in this thesis were Al-20Sn-7Si-1Cu and an Al-20Sn-7Si- 1Cu-1Mg wt% composition; with the latter achieved by the controlled addition of Al- 50Mg wt% master alloy. The project identified an aluminium-tin-silicon based alloy that could be sintered to near 100% of theoretical density in the manufacture of a ¾ scale rod form. The process and material produced should be capable of replacing the bearing alloys typically used in aerospace pump applications. The addition of magnesium, with controlled morphology and size, and the parallel use of a nitrogen sintering atmosphere, significantly improved the heat treated density of these materials. Successful sintering, typically completed at 500°C, could be significantly reduced in time by the use of pressurised nitrogen from 20 hours to 5 hours. The sintered microstructure generated was a heat treatable aluminium / copper matrix with desirable, discrete regions of silicon (typically 3 – 4 microns in size) and reticular tin.
14
Corujeira, Gallo Santiago. "Active screen plasma surface engineering of austenitic stainless steel for enhanced tribological and corrosion properties." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/275/.
Full textAbstract:
Low temperature plasma surface engineering has been a useful method for increasing the hardness and wear resistance of austenitic stainless steel without reducing the corrosion resistance of this alloy. Plasma carburising is of particular interest as it produces thicker hardened layers than plasma nitriding, and an equivalent improvement in the tribological and corrosion performance of the base material. In this project, the active screen (AS) plasma technique was used to carburise austenitic stainless steel AISI 316 and the obtained layer of carbon expanded austenite was compared with the one produced by conventional DC plasma treatments. The hardening and wear resistance produced by AS and DC plasma carburising were equivalent. With regard to corrosion, the AS treated material performed better than its DC counterpart as a consequence of the improved surface quality of the former. The mechanism of AS carburising was comparatively studied with its AS nitriding counterpart. Different experimental arrangements and two plasma diagnostic techniques were used for this purpose: optical emission spectroscopy and electrostatic probes. The evidence shows that AS nitriding relies on the deposition of iron nitrides and the active species in the plasma to produce hardening, whilst AS carburising requires the plasma activation and moderate ion bombardment.
15
Zhang, Bo 1963. "Recovering gold from high density gangues with Knelson concentrators." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20934.
Full textAbstract:
This research documents the use of a 7.6 cm laboratory Knelson Concentrator (LKC) to determine the amount of gravity recoverable gold (GRG) content in ores and evaluate the performance of gravity circuits, with an emphasis on high gangue density. Two approaches were used to minimize the effect of the high gangue density in estimating the GRG content, oversize removal and 2:1 ratio dilution with silica flour.The amount of GRG was determined in four ore samples with an established protocol, yielding values of 35% to 78% of total gold.
Results from the Angnico-Eagle La Ronde Division (AELRD), Louvicourt and East Malartic mills suggest that the typical Knelson-based gravity circuit which can recover one half to two thirds of GRG from low density gangues will only recover one third to two fifths of the GRG from high density gangues. Simulation of gold recovery at AELRD showed that the high circulating loads, 700--1100%, were a significant factor in reducing gold recovery by gravity. (Abstract shortened by UMI.)
16
Hasan, Muayad Mohammed. "Enhanced recovery of heavy oil using a catalytic process." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/53253/.
Full textAbstract:
Oil is a major source of energy around the world. With the decline of light conventional oil, more attention is being paid to heavy oil and bitumen, as a good alternative to light oil for energy supplies. Heavy crude oils have a tendency to have a higher concentration of metals and several other elements such as sulfur and nitrogen, and extraction of these heavy oils requires more effort and cost. The Toe-to-heel Air Injection catalytic upgrading process In-situ (THAI-CAPRI) is an integrated process which includes recovery and upgrading of heavy oil and bitumen using an air injection process, and horizontal injector and producer wells. Since the process works through a short distance displacement technique, the produced oil flows easily toward the horizontal producer well. This direct mobilized oil production and short distance are the major properties of this method which lead to robust operational stability and high oil recovery. This technique gives the possibility of a higher recovery percentage and lowers environmental effects compared to other technologies like steam based techniques. A catalyst plays a crucial role in the THAI-CAPRI technique to be successfully conducted. However, heavy coke can be formed as a result of the thermal cracking of heavy oil occurring in the THAI-CAPRI process, and a catalyst resistant enough to use in CAPRI needs to be developed. Therefore, there is a need to understand the pore structure to achieve a high catalyst quality, to obtain a structure that directly affects the fluid behaviour within a disordered porous material. In this study, novel experimental techniques were used to obtain greater accuracy results, for the information obtained from gas adsorption curves by using a combination of data obtained for two adsorptives, namely nitrogen and argon, both before and after mercury porosimetry. This new method allows studying the effect of pore-pore co-operative during an adsorption process, which significantly affects the accuracy of the pore size distributions, obtained for porous solids. A comparison, between the results obtained from the characterisation of a mixed silica-alumina pellet and those obtained from pure silica and alumina catalysts, were presented to study the effects of surface chemistry on the different wetting properties of adsorbates. The pore networks within pellets invaded by mercury following mercury porosimetry have been imaged by computerized X-ray tomography (CXT). It was noticed that the silica-alumina catalyst had a hierarchical internal structure, similar to that for blood vessels in the body. To validate the findings of the pore geometry characterisation obtained from the new method, several techniques, such as cryoporometry, gas sorption isotherms, and mercury intrusion experiments, were considered. Further, a novel well design consisting of two horizontal injectors and two horizontal producers was used in different well configurations, to investigate the potential for improved efficiency of the THAI process on the heavy oil recovery. A 3D dimensional simulation model, employing the CMG-STARS simulator, was applied in this simulation. Two horizontal injectors and producers were designed in this project, instead of horizontal injector and producer were used in the Greaves model (the base case model), to investigate the effect of the extra injector and producer on the performance of the THAI process. It was found that the locations of the well injections and the well productions significantly affected the oil production. For the study of the effectiveness of the catalysts in the oil upgrading process, the CAPRI technique has been simulated to investigate the effect of several parameters, such as catalyst packing porosity, the thickness of the catalyst layer and hydrogen to air ratio, on the performance of the CAPRI process. The TC3 model used by Rabiu Ado (2017), which was the same model used in the experimental study of Greaves et al. (2012), was also used in this study. The Houdry catalyst characterised by the experimental work was placed around the horizontal producer in this simulation.
17
Rai, Subash. "Role of sulphur on carbon deposition on AGR fuel cladding steel." Thesis, University of Birmingham, 2019. http://etheses.bham.ac.uk//id/eprint/8882/.
Full textAbstract:
Filamentary carbon deposition on 20Cr/25Ni/Nb austenitic stainless steel from 1000-5000 ppm C2H4 in 1%CO/ bal. CO2 at 600°C has been investigated. This filamentary carbon deposition is catalysed by metallic nickel-rich particles formed intrinsically from the alloy during the early stages of oxidation. Samples were analysed using electron microscopy techniques. A simple model has been proposed to explain the formation of nickel-rich particles within the subsurface oxide layer. Furthermore, in this project the effect of COS, H2S and CH3SH on carbon deposition were examined. Addition of sulphur species suppressed the deposition process but the effect was dependent on the concentration of C2H4 and the sulphur species. This suppressing effect of sulphur on carbon deposition was explained in term of the role played by the adsorbed sulphur in reducing the rate of the key steps of the growth process of a filament.
18
King, David Gareth. "Fibre-optic sensor development for process monitoring of epoxy resins." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8698/.
Full textAbstract:
An investigation was undertaken to examine the performance of a Fresnel reflection sensor (FRS) incorporated into a differential scanning calorimeter (DSC) to track the cross-linking of epoxy resins. The initial design used a micrometer translation stage to lower the FRS through an orifice in the DSC platinum lid and onto the pan containing the sample. During exothermic cross-linking experiments, the resin refractive index and the heat evolved were measured simultaneously, allowing for direct comparison between the data. Combining the two measurement techniques produced a powerful hyphenated analytical procedure that demonstrated the feasibility of using the FRS for in-situ cure monitoring of epoxy resin systems. During the cross-linking of specified resins, the sensor revealed optical phenomena throughout the latter stages and was shown to be sensitive to the glass transition temperature, nano-particulate movement, nano-particulate concentration and phase separation. Therefore, the introduction of the FRS to the DSC provided valuable cross-linking information. A second modification to the DSC permitted the accommodation of an optical fibre probe, which facilitated simultaneous DSC/FRS/Fourier transform infrared spectroscopy (FTIRS) analysis. Good correlation between the cross-linking kinetics of an epoxy resin system was demonstrated using the hyphenated techniques and hence alleviated the issues of cross-correlation between individual experiments.
19
Seymour, Andrew Richard Ian. "Optimisation of the fracture toughness of a novel ultra-high strength maraging steel." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8718/.
Full textAbstract:
This thesis details work that was carried out to optimise the fracture toughness and thermal stability of a new maraging steel called F1E. This steel was designed to precipitate Laves phase to improve the creep properties, and it was initially found that this was detrimental to toughness properties, and that further precipitation occurred during extended time at desired operating temperatures, embrittling the alloy. Initial work focussed on development of a heat treatment to stabilise the Laves phase, using a slow cool to the service temperature to fully precipitate the equilibrium volume fraction of Laves phase at this temperature without nucleating fresh particles, as it was believed that it was fresh particles forming during service which led to the loss of ductility after thermal exposure. This heat treatment process successfully stabilised the properties. Modifications were then made to the composition in an attempt to improve the ductility and toughness without losing strength or creep performance. Two changes were made - an increase in the nickel content, as increasing the concentration of nickel in the matrix of maraging steels has been shown to improve toughness; and a decrease in molybdenum and tungsten content to reduce the Laves phase volume fraction by 25%. These changes, along with further optimisations of the heat treatment used and refinement of the prior austenite grain size, were successful in improving the fracture toughness of F1E (or RR9922 as the modified composition is known) by a factor of 2, from 23 MPa m\(^0\)\(^.\)\(^5\) to 46.9 MPa m\(^0\)\(^.\)\(^5\).
20
Mohammed, Ameen Rayan Basheer. "Plastic deformation of Ti-6Al-4V at small scale : a microstructural and mechanistic study." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7901/.
Full textAbstract:
Two phase alpha/beta titanium alloys are used in a wide variety of applications such as aerospace, biomedical, gas turbine engine, sport and energy. These alloys have high specific strength and specific modulus as compared to magnesium and aluminium alloys as well as excellent corrosion resistance. The Ti-6Al-4V (α+β) alloy is the most widely used and the best known of all the Ti alloys. Although there are a number of observations in the literature reporting the mechanical responses of these two phase alloys, there exists very little understanding of the mechanisms of the individual phases and the alpha/beta interface’s role in strengthening. Additionally, it has often been reported in the literature that ‘smaller is stronger’ for different metals due to the presence of a size effect. There is no real understanding of the mechanism of the size effect in the alpha-beta titanium and HCP and its dependence on orientation. Single alpha, beta and alpha-beta colony micro-pillars have been manufactured from a polycrystalline commercial Ti-6Al-4V sample using Focused Ion Beam (FIB). Alpha/beta pillar contained two alpha lamellae separated by a thin fillet of beta phase. A nano-indenter was then used to conduct uniaxial micro-compression tests on Ti alloy single crystals, using a diamond flat tip as a compression platen. By controlling the crystal orientation along the micro-pillar using Electron Back Scattering Diffraction (EBSD) different slip systems have been selectively activated. The advantage of the micro-compression method over conventional mechanical testing techniques is the ability to localize a single crystal volume which is characterisable after deformation. This study makes a contribution to knowledge in several key areas, including an understanding of the mechanical response of different crystals at micro/submicro-scale, the effect of phase interfaces on deformation, and an understanding of the strengthening mechanism in two-phase Ti alloys, the orientation size effect in HCP metals and the CRSSs for each phase in Ti-6Al-4V. Therefore, in order to evaluate the behaviour of these alloys for future applications, it is imperative that the microstructural features and characteristics be quantified and examined on a small scale. The results showed that the beta phase in between alpha lamellae caused strengthening deformation. When the surface normal is parallel to the [0001] of the single alpha crystal, the material deforms with difficulty in the [0001] direction of the single alpha phase. The mechanical responses of the alpha, beta, and alpha/beta crystals not only depended on the size of the pillars, but also on the crystallographic orientation, the initial dislocation density and the relationship between the two phases in the case of α/β crystals. Extensive electron microscopy investigation revealed that the anisotropy in basal and prismatic slip systems can be directly correlated with the transmission of dislocations across the single crystal, the beta laths, and the accumulation of residual dislocation content near the interfaces and in the single beta phase. This information is essential in order to better model mechanical deformation in these materials. In addition, dislocation analysis indicated that the deformation of individual grains conformed to the Schmid factor (SF) analysis where slip primarily occurs on those slip systems where the resolved shear stress (SF) values are highest. The results presented in this thesis bring to light several concerns for designing with titanium alloys and identify a number of phenomena of strong scientific interest. They will allow for the development of realistic models for the mechanical behaviour and provide a comprehensive analysis that can contribute to the theoretical development of the design and enhancement of the titanium allows. Moreover, the role of crystallography in plastic deformation provides a novel insight into the nature of the orientation size effect in HCP. This work points towards the need for further investigations into the higher and lower temperature deformation behaviour of Ti-64 to fully understand the phenomena identified within this study.
21
Ariza-Zafra, Karol. "Improving performance of discharge equipment for coals with poor handling characteristics." Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/21539/.
Full textAbstract:
The accepted design techniques for bulk solids handling equipment are frequently overlooked during the installation of industrial process plants. As a result, flow unreliability is often observed in silos in the form of flow stoppages, product bulk density variations, formation of rat-holes, flushing, flooding and product segregation. In most cases when these problems are detected in silos, they are the result of a discharge pattern known as core flow, where localised flow channels promote the preferential draw of material from certain zones of the silo, with the rest of the material remaining stagnant. Coal handling is not the exception and process equipment is not always designed to cope with the often variable characteristics of the coal, which is frequently processed in a large variety of forms, with particle sizes ranging from fine dust to a top size several inches and other parameter like moisture content varying from completely dry to dripping wet. In order to solve the problems caused by core flow, the discharge behaviour of the silo needs to be modified to produce a uniform movement of all the material, to achieve a flow pattern known as mass flow. Static inserts have been proved to be an effective method of modifying the discharge patterns in silos, but their use and design procedures are not well understood or are well hidden behind patents and trade secrecy. This research project aims to produce practical guidelines for the design and positioning of static insert to improve flow in silos. The work presented in this thesis follows an experimental approach where the performance of an insert is first evaluated at bench scale in a 3 litre model silo and then validated at semi-industrial scale in a 400 litre test rig. The bench scale model allows the evaluation of numerous changes in insert morphology and positioning at relatively low costs, facilitating the development of practical rules for their design. Following this approach a design procedure for inverted cone inserts is proposed as a modification of a method developed by J. Johanson [Johanson, 1965]. A performance comparison was undertaken both at bench and semi-industrial scales with inserts designed following Johanson’s method and the modified method proposed by the author. The results showed that both inserts were capable of producing mass flow in an otherwise core flow silo, but the modified insert produced more consistent results, particularly with lower heights of powder bed. This experimental approach was also followed to develop a novel type of insert called open double cone which maximizes the area of influence of the insert inside the silo facilitating flow. For this insert, three design procedures where proposed with each of them producing inserts capable of achieving mass flow in the bench scale model. The main difference between the inserts produced by the three procedures, was the size of the insert in relation to the volume of the silo hopper. In a similar way, two procedures were also proposed for the design of double cone inserts, with the resulting inserts capable of achieving mass flow in the bench scale silo. Then, a prototype of an inverted cone designed with the modified method, a prototype of the open double cone and a prototype of a double cone were tested in the semi-industrial scale test rig. The results at both scales showed that the open double cone and the double cone inserts outperformed the inverted coned, by producing more uniform velocity profiles across the silo and also producing more consistent flow rates. Although the performance between the open double cone and the double cone was very similar, the open double cone was more consistent in producing flatter velocity profiles and also the double cone was more prone to produce slightly off centre discharges. The procedures proposed for insert design provide the tools needed to apply insert technology to industrial processes. This is demonstrated with the design of double cones which successfully eliminated rat-holing problems in conical silos from an industrial pneumatic conveying system. The bench scale methodology is also employed to try to solve flow unreliability issues experienced in an industrial coal silo. For this case, a bespoke type of insert was developed to respond to the complex geometry and mode of operation of the silo. The proposed insert produced very positive results at bench and semi-industrial scales, laying the bases for a solution for the full scale silo.
22
Chan, Park Hinn. "Design study of composite repair system for offshore riser applications." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/33455/.
Full textAbstract:
Risers in offshore operations are subjected to corrosion during their service life cycle. The use of relatively inexpensive, high strength to weight ratio fibre reinforced polymer composite (FRPC) as a load bearing pipe repair sleeve is an emerging technology that is becoming common for offshore applications. Risers experience complex loading profiles and experimental investigations often incur substantial time, complicated instrumentation and setup costs. The main aim of this research is to develop a design tool for the repair of offshore riser that suffers from external corrosion damage on its surface using FRPC material. The simplest configuration of a fixed platform riser in the form of a vertical single-wall pipe is being considered. Characterization of the stress-strain behaviour of the FRPC laminate in the composite repair system subjected to various load profiles of a common riser is performed. The means of composite repair takes into account the ease of automated installation. The final repair method considers the use of unidirectional pre-impregnated (prepreg) FRPC that is assumed to be helically wounded around the riser. Finite element models of the composite repair system were developed via ABAQUS. Global analysis of the entire length of the riser was omitted as external corrosions usually occurs in a localised manner on the surface of the riser. Instead, local analyses were conducted where boundary conditions were applied to mimic an infinitely long cylindrical structure such as the riser. The local analyses FEA models were made to capture the stress-strain behaviour of the FRPC laminate subjected to different load profiles including static loadings such as internal pressure, tensile load and bending load. The design loads were calculated based on a limit analysis known as Double-Elastic Curve method developed by Alexander (2008). Proper element selection and mesh convergence were carried out to determine the FE model that can minimize the time and CPU memory needed for the simulation without compromising the accuracy of the results. The second part of this research integrated experimental tests to validate the FE model developed using the ABAQUS general purpose code. Due to constraints on cost and supply of materials and equipment, small-scale tests were conducted. Similitude relations were used to determine the scale properties between the model and the prototype. The final results showed that the FE model can represent the real-life tests of corroded riser repaired with off-axis FRPC laminate with great accuracy of more than 85%. Hence can be a useful tool for design and parametric study of the composite repair system. Using the validated FE model, an extensive parametric study of the composite repair system with respect to varying corrosion defects was conducted. The thickness and length of the repair laminate were compared to the ASME PCC-2 standard. Optimum thickness and length of the composite laminate were determined based on the maximum allowable strains computed using the Double-Elastic Curve method. In addition, varying fibre angle orientation of the unidirectional prepreg was considered as it is one of the main factors in helical winding. Based on the results from the parametric study, a simple relation was developed to predict the required thickness of the composite repair system subjected to combined loading. This relation combined with the developed FE model can be used to provide a quick design and performance validation of a composite repair system for offshore riser, which is the main novelty aspect of this research.
23
Naylor, A. W. "The cultural and historical geographies of onshore oil exploration in the British East Midlands during the 20th century." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35862/.
Full textAbstract:
This thesis tells the hitherto neglected story of onshore oil exploration in the British East Midlands from 1908 to 1964. Drawing on a series of case studies it provides a regional historical geography, connecting science and industry to the exploratory field science of geology. During the period examined, two low key discoveries – Hardstoft, in Derbyshire (1919), and Eakring, in Nottinghamshire (1939) - altered Britain’s energy prospects, supplementing coal with liquid mineral oil. Using archival research methods and oral testimonies, the thesis reveals how a diverse assemblage of earth scientists, oilfield technologies and techniques, institutions and private companies developed a regional laboratory for oil exploration. Liquid energy fuelled heated political debates over land nationalisation and private ownership rights, the science of subsurface quantification and governance, and the role of industry in exploration. Though small when compared with global consumption and production figures, oil discovered in the British East Midlands provided a time critical supply of oil during World War Two. It also facilitated technological advances in oilfield development, contributed towards a new arm of economic geology (geophysics) and encouraged earth scientists to think of territory as a three dimensional entity, extending beneath, as well as along the land surface.
24
Ziegelmeier, Stefan. "Process analysis and material behavior of thermoplastic elastomers throughout the laser sintering processing chain." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/31532/.
Full textAbstract:
Laser sintering (LS), an additive manufacturing (AM) technology, allows for the production of 3-dimensional parts by fusing together successive layers of polymer powder without the need for tooling. Its potential and applicability, however, is still constrained due to the limited repertoire of materials available and the lack of detail in understanding both the important process-material interactions and consequently the requirements for the development of new materials. Past research has mainly focused on polyamide 12 (PA12) as the standard material, hence most of the empirically grown or theoretical, often idealized, process models are based on this polymer. As a result, it was shown that there are strong interactions between the material and the process leading to an undesired deviation of part properties. Thermoplastic elastomers (TPEs) for LS have gained more and more popularity for the production of, for example flexible parts in the recent past but they are a group of polymers that is neither well studied nor understood regarding their use in LS. Therefore, this PhD investigation has focused on TPEs in order to reveal their process specifics throughout the processing chain in LS. As the properties of parts manufactured by LS are, amongst others, influenced by the packing and flow efficiencies of the powders, the bulk (static) and flow (dynamic) characteristics of the observed TPEs were examined on the powder scale as well as their effects on the process and parts. The resulting part properties were evaluated in terms of their tensile properties, surface roughness and density. In contrast to previous studies which have rarely taken into account the characteristics of the un-sintered particles, this work provided a novel approach quantifying and describing the interconnection between the powder characteristics as well as its performance and the part properties, thus providing valuable input on future material design. As mentioned before, for typical semi-crystalline thermoplastics such as PA12, different idealized process models describing the Pre-Process specifics exist, but they might not necessarily be applicable for thermoplastic elastomers with significantly different thermal characteristics. Consequently, the important interactions during processing of TPEs have been studied by high speed and high resolution thermography helping to indicate the most important material properties in combination with calorimetric analysis. The resulting understanding of crystallization and melting behaviour helped to derive a design of experiments revealing the possible range for the process management in terms of temperature control as well as energy input and the resulting part properties. Moreover, it is known that polymers used in LS change their intrinsic properties due to processing conditions that are close to the crystalline melting temperature. As a result, within this PhD investigation the ageing behaviour of TPEs was studied. Both the powder and the sintered parts were examined for chemical and physical ageing effects. The results showed that the materials observed could be used without refreshing throughout the applied ageing cycles, however, changes in the processing behaviour as well as in the parts’ mechanical properties were evident. These changes were due to the differing ageing states of the LS-powder showing an increase in the particle size affecting the bulk materials packing density. In the literature, modifications in the rheological properties due to thermal loads during LS are already known on basis of PA12. It was shown that they tend to experience an increase in molecular weight with increasing processing cycles. In this work it was found that TPEs exhibit the exact opposite trend in a slight decrease of molecular weight likely to reduce the mechanical strength of tensile specimens. By using novel process adapted methods in order to reveal vital interactions of TPE powders for LS, this thesis makes a significant contribution to an AM database. In addition, the comprehensive observation and applications of these methods over the whole processing chain helped expanding the understanding of important requirements for the development of new polymers for LS and builds a substantial basis for future work and quality assurance.
25
Lam, Wing Cheong Marc F. "Experimental and numerical investigations into the behaviour of a 7175-T7351 aluminium alloy for aerospace gearbox housing applications at elevated temperatures." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49366/.
Full textAbstract:
The 7175-T7351 aluminium alloy was studied to determine its suitability for the step-aside gearbox housing on the Rolls Royce Trent 1000 engine. The industrial motivation of this work was to reduce the weight of the gearbox housing using this lightweight material to ultimately improve the specific fuel consumption of the aircraft. This involved obtaining the mechanical properties of the aluminium alloy via a series of uniaxial mechanical tests with parameters based on the operating conditions of the gearbox housing during a typical flight cycle. Furthermore, a constitutive viscoplasticity model, with the inclusion of material ageing parameters, was developed to predict the material’s cyclic response under strain-controlled isothermal fatigue conditions at the gearbox housing’s operating temperatures. With this capability, a prediction for when the strength of the gearbox housing falls below the required design strength for safe use could be made. The room temperature hardness tests demonstrated the effect of time spent at elevated temperatures on the material’s hardness. It was found that the higher the soak temperature, the greater the initial rate of decrease in room temperature hardness and the lower the asymptotic value of hardness that was reached. For example, up to 24 hours of soaking at 200◦ C, the hardness decreased by 33%, and up to 1000 hours the hardness had decreased by 55%. For the same durations at 180◦ C, the hardness decrease was 17% and 47% respectively. Soaking at 120◦ C had an insignificant effect on the hardness of the material, indicating that the microstructure was thermally stable. Hardness testing could be used as a method to assess the strength of the gearbox housing for service monitoring during certifcation. Similar to the hardness tests, the elevated temperature tensile test results also revealed degradation in the mechanical strength of the alloy after prior soaking at elevated temperatures. The tests at 200◦ C on the as-received material decreased the yield stress by 31% and after soaking at test temperature for 20 hours prior to testing, the yield strength dropped by 52%. After a 2 hour temperature, the yield stress decreased from 220MPa to 165MPa which is alarming since the gearbox housing spends about 18 minutes at 200◦ C and 190MPa during climb. This suggests that in less than 6 flight cycles, the material’s strength will fall below the maximum operating stress of the gearbox housing and will be unsafe for continued use. Samples were soaked for up to 400 hours at 200◦ C and prepared for microstructural analysis. EBSD images showed that the grains were no significantly affected by the temperature exposure and showed no signs of coarsening. TEM and EDX analysis revealed that the majority of the particles within the grains were zinc-magnesium rich particles and were assumed to be MgZn 2 precipitates based on the TEM particle identification. The precipitate size and inter-particle spacing were found to increase with soak time. The change in monotonic yield strength was therefore attributed to the coarsening of these precipitates. The material characterisation suggested that, although the 7175-T7351 aluminium alloy initially appeared to have desirable mechanical properties, it is unsuitable for this or similar applications due to the rapid decrease in strength and thermally unstable microstructure. Furthermore, if an aluminium alloy is considered for this application, then it may be vital to account for material ageing behaviour. The unified, uniaxial viscoplasticity Chaboche model was implemented to predict the material response strain-controlled isothermal fatigue tests at 160◦ C and 200 ◦ C. A material ageing term was added to the model to account for the material ageing that decreased the yield strength with time. With this addition, two assumptions were made: 1) material ageing only affects isotropic hardening and 2) isotropic hardening can be de-coupled into material ageing (as a function of time at elevated temperature) and mechanical softening (a function of accumulated plastic strain). The tests at 160◦ C and 200◦ C showed that numerical and experimental results were in good agreement, providing accurate isothermal cyclic stress behaviour of the 7175-T7351 aluminium alloy. Furthermore, it was shown that the mechanical softening and material ageing components could be de-coupled. However, when the model was used to predict stress-controlled isothermal fatigue data and a cyclic stress relaxation tests, a number of deficiencies arose. The predicted ratcheting and ageing rate was greater than expected. The material ageing term may require an additional function to change the ageing rate depending on whether the material is elastically or plastically loaded. Norton’s creep power law could not predict term long stress relaxation behaviour but it was sufficient enough to describe to short- term viscous effects under the strain-controlled fatigue conditions. Despite these deficiencies, the model provided an initial point for a unified, viscoplasticity model for the 7175-T7351 alloy. Due to the rapid ageing of the material, the model could be used to predict if or when a material’s strength is unsuitable for safe operating use.
26
Imbaby, Mohamed. "Fabrication of 316-L stainless steel and composite micro machine components using softlithography and powder metallurgy process." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1212/.
Full textAbstract:
This thesis presents a new approach to fabricate high precision micro machine components from stainless steel and stainless steel ceramic composite materials, using Softlithography and powder metallurgy processes. Three different 316-L stainless steel powders, including 5, 10 and 16 μm in size, and two different ceramics powders, including 400 nm alumina and 320 nm titania, were tested. The PhD research process can be divided into three main stages. In the first stage, high quality SU-8 master moulds and their negative replicas soft moulds are produced using Softlithography technique. The second stage includes preparing the stainless steel slurries, filling the soft micro moulds, obtaining the green micro components, de-binding and sintering. In the third stage, the fabrication process has been developed further to produce stainless steel-ceramic composite micro components. Fabrication process in each stage was investigated in detail and the optimum properties were produced. Dispersant acrylic-based binder is adopted in this research successfully in producing damage-free green micro components. A cold isostatic pressing technique is also adopted to improve the densities and linear shrinkages of the stainless steel green and sintered micro components. A new mixing method is used to improve the homogeneity of the ceramic inclusions in the stainless steel matrix of the composite micro components. Characterization of the sintered stainless steel and composite micro components in terms of shape retention, density, linear shrinkage, internal structure, hardness and surface roughness were investigated in detail. The resultant stainless steel and composite micro components retain the same high geometric quality as the SU-8 master moulds.
27
Mitchell, Colin A. "A study of the powder processing, tribological performance and metallurgy of Aluminium-based, discontinuously reinforced metal matrix composites." Thesis, Edinburgh Napier University, 2002. http://researchrepository.napier.ac.uk/Output/3807.
Full textAbstract:
The principal objectives of the research reported in this thesis are: to determine the effect that sinter time has on the metallurgical behaviour of alumina-reinforced aluminium-606lmatrix composites; compare and assess the wear resistance of alumina and silicon carbide reinforced aluminium 6061-matrix composites, together with monolithic aluminium 6061 alloy; determine the effect that reinforcement particle size has on the wear resistance of aluminium 6061-matrix composites; identify the relative merits of two techniques for depositing copper coatings on to alumina reinforcements. Through investigation, a successful method of processing silicon carbide and alumina particulate-reinforced AA6061 composites, fabricated by cold uniaxial pressing with vacuum sintering, has been determined. The processing route is as follows: pressing at 400 MPa; vacuum sinter at 600°C for 30 minutes; solution heat treat for 30 minutes at 530°C then water quench; precipitation (ageing) heat treat for 7 hours at I 75°C, then air cool. Metallurgical examination of composites revealed that magnesium was found to collect at interface regions around alumina particulates, resulting in the depletion of magnesium from the aluminium 6061 matrix. The severe depletion of magnesium from the AA6061 matrix when alumina is used as a reinforcement was found to occur during long (greater than 30 minutes) sintering times using a sintering temperature of 600°C. It is postulated that the formation of spinel (MgA12O4) formed from the reaction of magnesium with alumina is a probable cause for the Mg migration. The composites containing alumina particulates were found to have lower hardness values than the monolithic alloy and composites containing silicon carbide, when sintering took place for longer than 30 minutes. Adding 5 wt% silicon to the AA6061 matrix in composites reinforced with alumina particulates was found to reduce the magnesium depletion for sinter times up to one hour at 600°C and give improved composite bulk hardness. During the research, a need for an improved wear testing machine was identified. Therefore a wear test rig, which allows samples of different materials (under different applied loads if required) to be tested simultaneously without interference between test pieces, was designed and commissioned. Two electroless methods for copper coating alumina particulates were also investigated. One method used formaldehyde as the reducing agent, while the other employed hydrazine-hydrate as the reducing agent. The latter method has proven to be quicker, and with improved results, compared to the traditional method using formaldehyde as the reducing agent.
28
Demers, Isabelle. "Activated silica sol as a flocculant in treatment of mine effluents." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79227.
Full textAbstract:
Lime neutralization of acidic drainage is the most common process to produce an environmentally acceptable effluent. The process involves neutralization, precipitation of metal hydroxides, flocculation, settling and storage of the sludge. The sludge is not entirely stable over the long term due to the natural pH decline in the storage area that can re-solubilize metals. The use of activated silica sol could be an alternative to flocculants in the lime neutralization process. The nature of the metal hydroxide---silica bond could make the sludge more stable on short and long term.It was observed that similar settling characteristics can be obtained with the standard flocculant and a low dosage of activated silica sol. Using activated silica sol, the settling rate is dependent on the concentration of magnesium and iron in the mine effluent.
There was an improvement in sludge stability when using a high dosage of activated silica sol. Two mechanisms have a role in the increased stability: the adsorption bond and the buffering capacity of activated silica sol. The tests suggested that a dosage of 0.1 gSiO2/gFe optimizes the settling characteristics and the sludge stability.
29
Buhagiar, Joseph. "Plasma surface engineering and characterisation of biomedical stainless steels." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/3744/.
Full textAbstract:
Low temperature plasma surface alloying with nitrogen (nitriding), carbon (carburising) and both (carbonitriding) has been successfully employed in hardening medical grade ASTM F138, ASTM F1586 and ASTM F2581 as well as engineering grade AISI 316 by the formation of a modified layer better known as S-phase or expanded austenite. In this study, systematic plasma treatments and characterisation were performed on medical grade stainless steel in order to establish the optimised treatment conditions, especially temperature, which can maximise the hardened case depth without any detriment in corrosion resistance. The surface of a biomaterial must not adversely affect its biological environment and return the material surface must not be adversely affected by the surrounding host tissue and fluids. Experimental results have shown that this duality of concern can be addressed by creating S-phase. It has been shown that low-temperature nitriding (430°C), carburising (500°C) and carbonitriding (430°C) improved the localised corrosion, corrosion-wear and fretting-wear resistance of these medical grade stainless. Also biocompatibility studies have proved that these hardened surfaces were biocompatible under the realms of the tests conducted in this study therefore the use of hardened medical grade austenitic stainless steel might be suitable in implant applications.
30
Aboulkhair, Nesma T. "Additive manufacture of an aluminium alloy : processing, microstructure, and mechanical properties." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/31152/.
Full textAbstract:
Additive manufacturing of aluminium alloys using selective laser melting (SLM) is of research interest nowadays because of its potential benefits in industry sectors such as aerospace and automotive. However, in order to demonstrate the credibility of aluminium SLM for industrial needs, a comprehensive understanding of the interrelation between the process parameters, produced microstructure, and mechanical behaviour is still needed. This thesis aims at contributing to developing this comprehensive understanding through studying the various aspects of the process, with investigation of the powder raw material to the near fully dense samples, focussing on the alloy AlSi10Mg. The primary building blocks in the SLM process are the single tracks. Their formation is affected by the physical properties of the material that control the laser-material interactions. Keyhole mode melting was found to be dominant when processing AlSi10Mg, producing conical-shaped melt pools. Porosity was not evident in single tracks and individual layers. Satellites and balling defects, however, were observed on top of the tracks and layers at higher scan speeds, which contribute to porosity formation with layer progression. The combination of process parameters controls the amount of porosity formed, with the scan speed controlling the type of pore; metallurgical or keyhole pore. A pre-melt scan strategy significantly reduced porosity and successfully produced 99.8% dense samples. Furthermore, the pre-melt scan strategy was seen to effectively reduce the number of pores developed when using powder that does not fully comply with the process standards. The gas flow rate within the process chamber controlled laser spatter and condensate removal during processing, which in its turn affected the degree of porosity in the samples. The SLM process resulted in an AlSi10Mg alloy with a characteristically fine microstructure, with fine equiaxed grains at the melt pool core and coarser elongated grains at the boundary. The material showed a strong texture, owing to directional solidification. Cellular dendritic Al with inter-dendritic Si was observed. The material was subjected to a T6 heat treatment that transformed the microstructure into spheroids of Si in the Al matrix. This study investigated, for the first time, the local mechanical properties within the SLM material using nanoindentation. This showed a uniform nano-hardness profile that was attributed to the fine microstructure and good dispersion of the alloying elements. Spatial variation within the material was recorded after the T6 heat treatment due to phase transformation. This study is also the first to report on the compressive behaviour of solid SLM material, which is important for developing prediction and simulation models. The heat treatment softened the material and provided it with an increased ductility under indentation, tensile, and compressive types of loading. In addition, the material showed good fatigue performance, which was further improved by heat treatment and machining to obtain a smoother surface roughness. This investigation has, therefore, developed an understanding of the various aspects of the SLM process yielding near fully dense parts and defined the microstructure-mechanical property interrelation promoting the process for Al alloys in a number of industrial sectors.
31
Afilaka, Daniel T. "Avoiding the sintering of coal fired shallow fluidized beds." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33534/.
Full textAbstract:
Fluidised bed combustion (FBC) has been identified as one of the best technologies available for lump coal combustion. A major drawback during prolonged operation of FBC systems particularly bubbling fluidised bed (BFB) systems is sintering and agglomerate formation of bed material that affects performance efficiency and reliability in industrial applications as exemplified at Associated British Sugar (AB Sugar). The mechanisms responsible for sintering and agglomerate formation in this type of system need to be understood, to promote continual use of this technology for efficient coal utilisation. The first set of investigations focused on agglomeration properties of bed material (Garside 14/25 sand) used in Industrial FBC at AB Sugar. Bed material was calcinated between 800 and 1200°C in a high temperature furnace in the absence and presence of coal (three types of bituminous coals) or coal ash. Results showed sintering and agglomerate formation of bed material can occur in the absence of coal or coal ash at a calcination temperature near 1200°C. Addition of coal or coal ash further promotes sintering and agglomerate formation at 1000°C. Combustion stages appears to influence surface morphology, chemistry and mechanisms of agglomerated bed material based on similarities observed in the agglomerated bed material formed from calcination of Garside 14/25 sand bed material mixed with coal, and those formed in industrial scale FBC during combustion of lump coal. The second set of investigations used two different lump bituminous coals classified as washed (undergone washing process to remove mud/shale stone) or unwashed (still containing the mud/shale) from the same mine (Blyth, typically referred to as Blyth coals) as those used in the AB Sugar industrial FBC. Combustion of washed and unwashed Blyth lump coals (9 to 19 mm particle size) was investigated in a 30 kW pilot scale bubbling fluidised bed combustor (PSBFBC) during normal combustion and crash stop combustion runs. This simulated conditions in the AB Sugar Industrial FBC system with a thermal rating of approximately 30 MW, which uses larger coal particle size of 12 to 25 mm. Results reveal unwashed Blyth lump coal in the PSBFBC and industrial FBC causes some sintering and agglomerate formation of the bed material over short operation periods of 52 and 240 hours respectively, which was not observed in the washed Blyth coal system over a similar operating period. Observed sintering and agglomeration formation in unwashed Blyth coal is mainly attributed to accumulation of mud/shale stones in the bed, which would have been mostly removed by the washing process. The crash stop combustion run, done to simulate the fan trip scenario in the industrial FBC system, promoted sintering and agglomerate formation in the PSBFBC, possibly due to the 30 to 50°C temperature rise in the bed when fluidised air was stopped. Continuous deposition and increasing concentration of mud/shale stones in the bed affects the localised temperature as well as the fluidising properties and quality, eventually promoting sintering and agglomerate formation. PSBFBC bed height, bed material particle size and measured pressure drop also increase with increasing operating time and mud/shale stones deposition in the bed. Deposition of coal ash to the surface of the bed material (sand) in the PSBFBC was analysed by the use of SEM-EDX and XRF. The deposition of ash to the surface of PSBFBC bed material sand increases as the operation times increases, as identified by increasing concentration of Al, K and Ca on fluidised bed sand particle surfaces in their stable oxide forms of Al2O3, K2O and CaO respectively.
32
Wardle, Peter. "The selective heating of pyrite in coal using microwave energy." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12017/.
Full textAbstract:
The objective of this research project was to investigate the effect of microwave treatment on the conversion of pyrite in coal in order to enhance its magnetic properties and to aid subsequent desulphurisation by magnetic separation. Key areas of this investigation include:- a review of the fundamental theoretical aspects of heating in an applied microwave field, a detailed literature survey of the potential applications of microwave heating to aid coal desulphurisation, a study of the transformation mechanisms of pyrite by microwave and conventional heating methods, a comprehensive review of the influence of heterogeneity on the dielectric properties of coals and the effect of high power microwave heating on the decomposition of pyrite in a high sulphur coal. A detailed survey of the literature has shown that although a significant amount of work has been reported on the microwave heating of coal, little information is available which examines the mechanism through which different coals heat in an applied microwave field. A study is therefore presented in this thesis which quantifies, for the first time, the structural ordering of carbon in a range of coals of various ranks and the relationship with their dielectric properties. The results show a clear relationship between the structural ordering of carbon in coal and dielectric loss factor. Essentially, as the structural ordering increases, the level of free charge (per unit volume) increases together with electron mobility which results in an increase in dielectric loss factor. The transformation of pyrite to form the more magnetic pyrrhotite and other related decomposition products by conventional radiant heating has been the focus of much research. However, little attention has been given to the effect of microwave heating on the mechanisms of pyrite transformation in inert and oxygen-containing atmospheres. The study presented in this thesis investigates the effect of temperature, particle size and heat treatment time to establish how these affect the transformation process and the subsequent nature of the final product. This study showed that exposure of pyrite to both conventional and microwave heating methods enhanced its magnetic properties as a result phase alterations at the particle surface. Conventionally heated pyrite samples showed the highest magnetic susceptibility increases, speculated to be due difficulties surrounding the temperature control and measurement of the microwave heated samples. From a review of the literature in this field of research and by SEM observations made for each sample test in this work a general pyrite transformation model as a result of microwave exposure is proposed. The effect of microwave radiation on the conversion of in-situ coal derived pyrite was also investigated. The study presented here extends previous work by others by assessing quantitatively the influence of higher applied microwave power levels on the conversion of pyrite in coal. Samples of run-of-mine high pyritic sulphur content (~12%wt) Kentucky coal were microwave pre-treated at varying exposure times using 8kW and 15kW of microwave power operating at a frequency of 2.45GHz. This work included initial material characterisation which consisted of TGA, optical microscopy and dielectric property measurement, followed by SEM/EDAX characterisation of both microwave treated and untreated sample specimens. This is the first time that microwave treated coal, embedded in a carnauba wax mounting medium, has been observed by this method with focus on the thermal alterations of the pyrite phase. It was demonstrated that with sufficient power and residence time, the conversion of pyrite to the more magnetic pyrrhotite is achievable using microwave irradiation. The amount of pyrrhotite formed as a result of microwave exposure varies with microwave residence time and forward power level. Comparisons of change in the iron sulphide species in the coal was made between microwave treated and untreated material. Using a multimode microwave cavity it was found that significant amounts of pyrrhotite were formed in 20s when using 15kW of microwave power. Treatment at lower power levels in this type of cavity was found to be less effective. The overall effect of treatment on the coal proximate character was minimal.
33
Azri, Mohammad Hazwan. "Accessing the extent of kerogen/bitumen interactions on source rock maturation and hydrocarbon generation." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13519/.
Full textAbstract:
In order to ascertain whether kerogen and the heavy oil or bitumen generated during the initial stages of source rock maturation then go on to produce similar gas yields compared to the natural situation when they are present in source rocks, a study has been conducted on an immature type II Kimmeridge Clay Formation (KCF) source rock (Dorset, United Kingdom) with different total organic carbon contents (14, 25 and 30 % TOC), and all having an initial vitrinite reflectance (VR) of approx. 0.4 % Ro. Anhydrous and hydrous pyrolysis experiments were conducted on the whole immature source rock, the isolated partially matured bitumen-extracted source rock and the isolated bitumen (bitumen generated and extracted from the initial source rock) and mixtures of the isolated partially matured source rock and bitumen using two types of Hastalloy vessels (22 and 25 ml) at 320-420 °C for 7-48 h over a pressure range of 115-900 bar. Hydrocarbon gas yields and the increase in VR were greater from the whole rock experiments compared to the experiments on the isolated partially matured source rock and isolated bitumen (no mineral matter present), as well as the experiments on mixtures of the isolated partially matured isolated source rock and bitumen combined. The effect of particle size were also found to be of significance as higher gas yields were obtained from recombined mixture experiments using powdered samples (14 % TOC source rocks) compared to using rock chips (30 % TOC source rocks). Hydrocarbon gas yields, pyrobitumen yields, and VR values were found to decrease as pressure increases towards 500 and 900 bar compared to 180 bar at 350 °C where the effects of pressure retardation were found to be much more significant from the partially matured source rock maturation and bitumen in isolation than from the whole source rock. At 420 °C, gas generation, bitumen plus oil and coke yields were not affected by pressure, but VR decreases going from 310 bar to 500 and 900 bar. The results obtained demonstrate that the interplay of inherent mineral matter, reactant phase, source rock/kerogen, bitumen and pressure are key factors in determining the extent of hydrocarbon generation and source rock maturation in geological basins.
34
Kobusheshe, Joseph. "Microwave enhanced processing of ores." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11393/.
Full textAbstract:
Recent research developments have suggested that microwave assisted comminution could provide a step change in ore processing. This is based on the fact that microwave-absorbent phases within a multi-mineral ore can be selectively heated by microwave energy hence inducing internal stresses that create fracture. A detailed review of existing literature revealed that little or no information is available which relates and examines the influence of hydrated minerals on microwave assisted fracture despite the fact that most important ores are associated with phyllosilicates, the vast majority of which are hydrated. A study was carried out on two Kimberlite diamond ores containing various types of hydrated minerals but devoid of any semiconducting minerals which are known to be good microwave heaters. The results confirmed that dehydration of minerals containing interlayer adsorbed water induces significant micro and macro fractures after microwave treatment. The significance of microwave induced fracture on beneficiation was investigated by conducting liberation and flotation tests on two porphyry copper ores. It was demonstrated that microwave pre-treatment improves beneficiation at sizes suitable for flotation and that higher improvements in degree of liberation are attained in coarser particle sizes between 212 and 425 µm. Flotation tests demonstrated a potential for real economic benefits in terms of value proposition. An increase of 8-10% in copper sulphides recovery from coarse sized particles (-400+200 µm) and an overall increase in grade/recovery of between 1-2% was obtained. The results also showed that microwave pre-treatment enhances selective mineral recovery as the grade-recovery of iron sulphides decreased in all but one microwave treated samples. The major drawback to further developments towards industrial scale application was found to be the lack of an effective continuous processing microwave applicator. Any future applicator designs must be able to ensure localised hot spots and confinement of all the microwave energy.
35
Avila, Claudio. "Predicting self-oxidation of coals and coal/biomass blends using thermal and optical methods." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12710/.
Full textAbstract:
Self-oxidation and spontaneous combustion of coals is a problem of global concern. There are social, economic and environmental costs associated with this phenomenon and major incidents can, in extreme cases, lead to human casualties. More often however, damage is made to commercial facilities, the calorific value of the fuel is reduced and substantial release of noxious gases, particulate matter and CO2 may contribute to local and international pollution levels. This problem is not only restricted to coals, it also affects other carbonaceous materials such as biomass and potentially coal-biomass blends. A considerable amount of literature has been published, and whilst the causes are relatively well understood, the existing methods for predicting spontaneous combustion are not reliable enough for scientists or the coal industry. This research focuses on understanding the oxidation characteristics of coal, biomass and coal-biomass blends at low temperatures, with the aim of defining a set of experimental test procedures to identify coal and biomass propensity to spontaneously combust. Based on a comprehensive literature survey, two main research areas were identified as feasible sources of information to detect prone coals: microscopy and thermal analysis. Considering these, an extensive experimental program was carried out using 42 coals (including at least three well known samples prone to spontaneous combustion), 10 different biomass types, and a number of coal-biomass blends, including diverse particle and sample sizes, at different stages of the oxidation process. Initially, pulverized coal samples (size <106µm) were subjected to thermogravimetric and calorimetric tests (small sample size), and differential thermal analysis (large sample size) using a large scale reactor. From these tests, the link between the weight loss/gain of the samples and the reactivity at low temperature was confirmed, developing successfully two thermogravimetric tests to identify high risk samples. Afterwards, textural features of thermally altered coal samples (light reflectance and particle morphology) were studied by means of combined petrographic and image analysis techniques. Results showed that particle reflectance and textural changes depend on oxidation temperature, which are linked to the spontaneous combustion potential. Based on these results, two tests were proposed by comparing light reflectance before and after a slow oxidation, quantifying the formation of morphotypes associated with highly reactive samples. A similar approach was used to study biomass and coal-biomass blends, focusing on the quantification of intrinsic reactivity and particle morphology by TGA and optical microscopy. For raw and char biomass particles, results showed a significant correlation between the optical and reactivity properties. Additionally, several new morphotypes were identified from biomass char samples. These characteristics were associated with the thermal behaviour of large samples, although these results did not suggest any distinctive indicator to identify samples prone to self-heat, concluding that the low temperature oxidation of biomass is a completely different phenomenon to that experienced by coals. In the case of coal-biomass blends, the most relevant finding was a synergetic effect observed for the ignition temperature, which was always lower than the ignition temperature of the individual components. This finding has not been described in literature before, and further work is necessary in order to investigate this interaction in greater depth. Finally, a set of standardised procedures to assess the reactive properties of these materials has also been proposed.
36
Brown, Robert Alexander. "The combustion of titanium powder in air and iron oxide." Thesis, University of Nottingham, 2000. http://eprints.nottingham.ac.uk/28106/.
Full textAbstract:
The quest for ever stronger and tougher steels has lead to an interest in the 'Acicular Ferrite' microstructure, its chaotic and disordered morphology imparting a high degree of toughness to the steel. To date, only complex and expensive materials and manufacturing processes have formed acicular ferrite within bulk cast steel. As such, the thrust of this research is to produce a cheap steel addition, an iron - titanium oxide metal-ceramic composite, that will facilitate the formation of acicular ferrite in conventionally manufactured bulk cast steels. The Self-propagating High-temperature Synthesis (SHS) process has been utilised to manufacture the iron - titanium oxide material from compacts pressed from Fe203 + Ti powders. The fundamental reactions that occur as titanium powder and Fe203 + Ti powder compacts are heated in air and argon atmospheres have been investigated. The process’s involved are reported and have been modelled mathematically. A computer simulation of the reaction process has been developed and tested against experimental evidence. The effect of various compact parameters, the starting compact stoichiometry and other processing variables have been examined with respect to the composition of the products and their morphology.
37
Jia, Yudan. "Numerical modelling of shaft lining stability." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/11924/.
Full textAbstract:
This research project focuses on the application of numerical modelling methods to rock mechanics problems, combining theoretical, experimental and numerical modelling work. Specifically, practical finite difference modelling approach for analysing shaft lining stability through the Marl and Potash strata at Boulby mine UK has been developed using the commercially available software FLAC2D/FLAC3D (ITASCA 2008). A soft rock Marl occurs close to the bottom of the two deep shafts at the mine. Both shafts concrete linings through this stratum have suffered considerable pressure, which has caused gradual failure of the shaft lining. So far, both shaft linings through the Marl stratum have been restored twice after sunk in 1970s and a further third relining is now required and being planned. The in situ observations, the rock engineers's experience, and the available in situ measurements at the mine have been significantly helpful in the validation of the numerical modelling. Many factors at the mine site have, however, made this numerical modelling research challenging, including complicated lining structures, complex lining failure conditions and the scarcity of laboratory test data for the weakest rock material - the Marl, which easily weathers on exposure. Based on a comprehensive literature review, a database of materials properties relevant to this research has been produced. The methodology of obtaining appropriate rock mass input material properties to use in numerical modelling based on laboratory test data has been studied. In three-dimensional models in this research, two modelling methods have been developed to simulate each stage in the shaft linings: the continuous model for all shaft linings and independent models for each shaft lining. The numerical modelling results imply that: Firstly, in the independent three-dimensional models, the modelling results were difficult to understand due to the complexity of the structures representing the shaft relining systems and difficulty in defining appropriate properties for the interface elements. Therefore, the continuous three-dimensional model that gives the analysable modelling results is recommended by the author for this research. By this method, the effect of the historic changes in the stress field on each shaft lining's stability can be investigated from initial shaft construction to subsequent relining phases. Secondly, the weak rock Marl should not be the only reason for the shaft linings' failure through this stratum. The roadway approximately 10 m beneath the Marl stratum was also a key factor for the stability of the shaft linings. The weak Marl cannot carry the stress redistribution around the shaft caused by the roadway excavation, which was an uneven loading acting on the circular shaft linings. This uneven loading introduced high shear and tensile stresses which threatened the stability of the circular concrete structures. Thirdly, the interface materials between high strength concrete blocks in shaft relinings improved the flexibility of the lining systems successfully, but decreased the strength of the whole lining systems as weak "joints". In addition, the single ring concrete blocks (the first and third relinings) are a more effective lining than the double rings (the second relining), and the third relining would perform better than the previous ones. As a recommendation for the further simulation, it is worth attempting to simulate the longer term deformation and stress conditions of the shaft concrete lining systems using the Creep model built in FLAC2D/FLAC3D codes. Additionally, deeper research work combined with in situ investigation can be done to decrease the uncertainty of the input material properties to make the numerical models as close to the real engineering situation as possible.
38
Silvester, Stephen. "The integration of CFD and VR methods to assist auxiliary ventilation practice." Thesis, University of Nottingham, 2002. http://eprints.nottingham.ac.uk/10003/.
Full textAbstract:
The current trend towards the adoption of retreat longwall mining methods and the associated rapid development of the access drivages has exacerbated the environmental conditions experienced within these workings. The combined use of roof bolt and continuous miner systems has improved the face advance rate within rapid development drivages. In order to maintain adequate dust and gas control it is essential that the auxiliary ventilation and monitoring systems are correctly installed and maintained. The causes of many potential environmental hazards experienced within auxiliary ventilated rapid development drivages, are often attributed to a failure by the workforce and supervisory officials to maintain the correct installation, maintenance and operational standards of the ventilation and mining systems. The potential ventilation hazards encountered may include: the failure to deliver the required fresh air quantity and velocity to rapidly dilute and disperse methane gas liberated in the vicinity of the cutting face, or the failure to maintain sufficient exhaust air quantity in the vicinity of the cut to adequately capture dust produced on cutting and loading of the extracted mineral. Results of recent research studies have demonstrated that validated Computational Fluid Dynamics (CFD) simulation models can adequately replicate examples of good and bad ventilation. CFD models may be constructed and solved to examine the relative ventilation benefits produced by alternative mining and auxiliary ventilation configurations. These models enable the practitioner to predict and visualise the velocity, pressure and contaminant fields within an auxiliary ventilated drivage. This research project has developed a prototype educational aid, which animates and visualises these airflow and pollutant dispersion patterns within a Virtual Reality (VR) model. By introducing a pollutant such as methane into the CFD models, the VR simulation highlights regions of potential methane concentration build-up to the trainee. The application also allows the user to select/investigate the environmental consequences of enacting a number of remedial actions.
39
Marshall, Christopher John. "Palaeogeographic development and economic potential of the coal-bearing palaeocene Todalen Member, Spitsbergen." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13794/.
Full textAbstract:
Palaeocene high-latitude coals from the Todalen Mbr. Central Tertiary Basin, Svalbard present an opportunity to understand the processes which controlled Arctic peat formation. Coals from this region have produced sub-economic quantities of bitumen during the 1920’s. Previous palaeogeographic models show significant variation between studies favouring deltaic and tidal wetland conditions. In addition, coal geochemistry studies have been limited to characterisation with little integration with palaeogeographic studies. This study utilises a large database of drill-logs to create cross sections and coal isopach maps to examine the spatial relation between seam thickness and palaeotopography. Palaeotopography is defined by mapping a ‘valley indicator’; the Grønfjorden bed, a fluvial conglomerate representing the first Palaeocene sedimentation. In addition, organic petrology organic and inorganic geochemistry were applied to samples from two mine sections and two boreholes to examine how coal quality and oil potential changed both within and between seams. The cross sections and isopach maps reveal that landscape had a significant but diminishing control upon peat accumulation. Thickest peats consistently formed at the break-in slope whilst topographic lows acted as areas of preferential channel formation and conduits for clastic sedimentation. Evolution of the landscape control had a significant control upon groundwater supply. As landscape control decreased the coals moved from isolated, raised bogs (Svea Seam) to laterally expansive minerotrophic fens (Svarteper and Askeladden Seams). Evidence of increasing marine influence and higher groundwater input was also observed from the Svea Seams to the Askeladden seam. In the Svea Nord and Longyear seam, supply of lithophile elements (Al, Ti, Na, K) is shown to be controlled by dust supply controlled by orbital cyclicity. By the Svarteper/Askeladden period lithophile element concentrations are controlled by clastic supply. Ca, Mg and Fe appear to be derived from groundwater. Sulfur concentration primarily reflects the supply of marine sulfur. Upper Todalen coals (Longyear, Svarteper and Askeladden) have significantly more oil potential than the Svea Seams with estimated retorting yields of 170-190kg/ton vs. 50kg/ton respectively. The Longyear seam exhibits relatively high HI values (ca. 300-400 mg/g TOC) consistent with a mixed Type II/III kerogen source. Greatest oil potential is shown to be favoured by formation within a fen environment, with high bacterial degradation (>100μg/g TOC hopanes), marine influence (>0.5wt% sulfur, Fe/S <0.9) and the unique temperate high lattitude Palaeocene climate of Svalbard, leading to preservation of hydrogen rich organic matter via organo-sulfur bond formation.
40
Hastings, Philip John. "The behaviour of short fatigue cracks in a beta-processed titanium alloy." Thesis, University of Nottingham, 1989. http://eprints.nottingham.ac.uk/28458/.
Full textAbstract:
An investigation has been made into the behaviour of short fatigue cracks in the β-processed titanium alloy, Ti6Ss. The effect on the material of a number of different variables was studied, particularly microstructure, as well as stress level, specimen design and specimen size. Initiation of cracks was found to occur at similar microstructural features in smooth specimens, regardless of a-platelet morphology. Cracks initiated from slip bands across small bundles of α-platelets, despite the presence of longer, more intense slip bands across α-colonies. α-platelet morphology was found to have a significant effect on short crack propagation rates when crack length was of the order of, or less than, the α-colony size - the more aligned the α-platelets, the greater the short crack propagation rates at equivalent ΔKs. Increasing the prior β-grain size (and hence the a-colony size) led to higher short crack propagation rates at equivalent ΔKs. Specimen design appeared to have an effect on short crack growth rates a uniaxial tension specimen design gave slightly higher growth rates than a four point bend specimen design. Variation in specimen size had no effect on short crack growth rates for the same microstructural condition, but a larger specimen size was found to reduce the scatter in specimen lives observed in smaller specimens. Short crack growth rates were apparently insensitive to stress level when compared at the same nominal ΔK values. Crack shape was found to vary considerably at crack depths below approximately 0.75mm. At crack depths greater than this value, cracks took an approximately semi-circular form. In keeping with many recent studies of short crack behaviour, short cracks were found to grow faster than long cracks at the same nominal ΔKs and at ΔKs below the long crack threshold value, ΔKth· A case study was carried out to determine the behaviour of short cracks in a cheese forged from an ingot slice of IMI685. Crack growth behaviour was found to be the same as that of Ti65s, but initiation behaviour was affected by the presence of pores in the IMI68S, leading to a significant reduction in fatigue life.
41
Bolingbroke, Richard Kendall. "The growth of short fatigue cracks in titanium and aluminium alloys." Thesis, University of Nottingham, 1988. http://eprints.nottingham.ac.uk/28452/.
Full textAbstract:
An investigation has been made of the growth of An investigation has been made of the growth of short fatigue cracks in aluminium and titanium alloys, with special emphasis on the effects of microstructure. For the commercial aluminum alloys examined (7010 and 2014A) a degradation in short fatigue crack resistance accompanied an increase in the degree of ageing, as is commonly reported for long, through thickness cracks. The short cracks however, were seen to propagate at substantially faster rates than conventional, long cracks at the same apparent applied ΔK and R - ratio. The similar, faceted fracture produced for both types of crack suggests that the same propagation mechanism was operative, despite the differences in growth rate. Discontinuous growth was observed for microstructurally short cracks, associated with the crack tip being held up over large numbers of cycles at grain boundaries both at the surface and in the interior of the specimen. The discontinuous nature of propagation and the anomalously fast growth continued until the maximum plastic zone size ahead of the crack tip approximated to the grain size of the material. At greater crack depths propagation rates, at equivalent ΔKs, for long, through thickness cracks and short cracks showed reasonable agreement, small discrepancies being explained in terms of the variation in closure contribution for the two types of crack. Similar propagation characteristics were observed for the two titanium alloys studied (IMI 318 and IMI 550) with substantially faster propagation for microstructurally short cracks than for long cracks at equivalent ΔKs. In contrast to long crack behaviour however, an increase in grain size resulted in a deterioration in short crack propagation resistance. The microstructure which was found to be the most resistant to the growth of short cracks consisted of fine primary α and transformed β grains with the volume fraction of each type of α approximately equal. The grain boundaries between the two distinct α-morphologies were seen to be particularly effective in reducing the propagation rate. In contrast, a coarse, aligned, Widmanstätten α-morphology exhibited the worst resistance to short crack growth. Even though colony and prior β grain boundaries were useful in retarding crack growth, propagation across packets of Widmanstätten laths was very rapid. Crack shape effects were considered to be important. A study was made to assess the variation in crack shape and the effect on crack propagation, particularly in non-equiaxed microstructures. Cracks with depths approximating to the grain size were seen to vary significantly in shape, though they all eventually took a semi-elliptical form, with half surface length/ depth (a/c) ratios between 1.0 and 0.8, at greater crack depths. It is suggested that a better correlating parameter for short crack growth is crack area rather than surface crack length which is commonly used at present. In this way, the effects of crack shape can be accommodated.
42
Pereira, Igor S. M. "Microwave processing of oil contaminated drill cuttings." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/28515/.
Full textAbstract:
Easily accessible oil reserves are currently decreasing, leading to an increase in more complex offshore deep-sea drilling programs, which require increasingly greater depths to be drilled. Such wells are commonly drilled using oil based muds, which leads to the production of drilled rock fragments, drill cuttings, which are contaminated with the base oil present in the mud. It is a legal requirement to reduce oil content to below 1 wt% in order to dispose of these drill cuttings in the North Sea and microwave processing is suggested as a feasible method of achieving the desired oil removal. However, there are currently gaps in our understanding of the mechanisms behind, and variables affecting, the microwave treatment of oil contaminated drill cuttings. The work described in this thesis seeks to address some of these gaps in knowledge. There were three main objectives for this thesis: (1) quantification, for the first time in the literature, of the main mechanisms driving oil and water removal during microwave processing of oil contaminated drill cuttings, (2) determination of key variables affecting performance during pilot scale continuous processing of oil contaminated drill cuttings and, for the first time, (3) treatment of drill cuttings with microwaves continuously at 896 MHz. Bench scale experiments carried out in a single mode applicator were used to quantify the mechanisms involved in oil and water removal from drill cuttings. It was found that both vaporisation and entrainment mechanisms play a role in oil and water removal. Vaporisation was the main mechanism of water and oil removal, and typically accounted for >80-90% of the water and oil removed. For oil removal, vaporisation of the oil phase accounted for 70-100% of the overall removal. The absolute amount of water entrained and vaporised was found to increase with increasing energy input and power density. However, as a percentage of the overall amount removed, entrainment was found to increase with increasing energy input. This was mainly due to higher heating rates at higher energy inputs, leading to pressurised, high velocity steam, which increased liquid carry-over (entrainment). Both the drill cuttings sample composition and applicator type were found to have an effect on the extent of entrainment/vaporisation. Samples consisting of a higher overall liquid content, tended to have a greater amount of surface liquid content. This led to a greater potential of carry over when steam generated internally left the sample. Increasing the power again led an increase in entrainment in this case. Different applicators were found to impact the electric field strength and power density within the water phase of the sample. Oil removal in multimode applicators progressed mainly through vaporisation (steam distillation) until the water content was sufficiently low to generate steam at a velocity high enough to entrain liquid droplets. When treatment was changed to single mode operation, entrainment occurred at an earlier stage, probably due to higher electric field strengths and power densities. It was also noted that the vaporisation mechanism of oil was more efficient at higher field strengths and powers, which could again be attributed to superheating and higher velocity steam, which enabled better mixing and heat transfer. Experiments were also run to determine the main variables affecting the performance of continuous processing of cuttings. Overall continuous processing showed a substantial improvement in the energy required, 150 kWh/t vs. >250 kWh/t, to reduce the oil content of a drill cuttings sample to 1 wt%. It was found that the initial water and oil content of the sample, as well as the sample particle size distribution, had the greatest effect on the efficiency of continuous processing. The effect of initial water and oil content on residual oil content was investigated methodically for the first time for continuous microwave processing of oil contaminated drill cuttings. An increase in initial oil content was found to have a significant impact on the energy input required to treat the sample to 1 wt% oil content. As the oil content increased, the energy input required increased exponentially, mainly as a result of the change in the physical structure of the sample. An increase in the water content led to an increase in energy input without any additional benefit to oil removal. However, as the water content was increased it was noticed that the theoretical energy input required to heat the entire sample approached the actual value measured for the energy input. This occurs as a result of the increasingly greater bulk dielectric properties of the sample as a result of higher levels of water content, which in turn leads to a higher efficiency in the conversion of microwave energy to heat in the sample. The effect of particle size on oil content distribution and removal was investigated. Oil content was found to be substantially higher in particles of size <1.0 mm, with removal also being significantly higher in this particle size range. However, as the majority of the samples tested, >80%, consisted of particles >1.0 mm, this improved removal is diluted by the performance of the coarser particles. The improved removal in finer particles is likely to be due to larger surface area, reduced path length within the particles and potentially higher electric field strength. Finally, samples processed continuously using a continuous microwave setup at 896 MHz showed improvements over both continuous microwave treatment at 2.45 GHz and bench scale setups. Increasing the f10wrate of the system at 896 MHz was also found to improve oil removal efficiency, which can be explained by the higher power requirements that would be required to maintain the energy inputs observed at the lower flowrate. Increasing the power leads to improved heating rates and thus increased removal rates through entrainment and vaporisation.
43
Whitaker, Iain Robert. "The structure and properties of autogenous laser beam welds in aluminium alloys." Thesis, University of Nottingham, 1994. http://eprints.nottingham.ac.uk/28427/.
Full textAbstract:
Autogenous laser beam welds were made in sheets of the aluminium alloys 8090, 8009 and 6061. The Al-Li based alloy 8090 was subjected to both continuous wave CO2 and pulsed Nd:YAG thermal cycles with average powers of 1.5-3.8 kW and 0.8- 0.9 kW respectively. The two techniques were compared for their influence on the 8090 solidified weld pool shape, the fusion zone microstructure and microhardness, the HAZ and the susceptibility of the fusion zone to post-weld heat treatment. It was found that CO2 keyhole welding is preferable to Nd:YAG welding, under the welding conditions investigated, as essential elements such as Li and Mg were lost by evaporation during Nd:YAG processing. Microscopy of the 8090 CO2 weld fusion zone revealed that the solidification mode was sensitive both to the temperature gradient and growth rate during solidification, with a transformation from cellular to equiaxed dendritic growth occurring from the weld pool edge to the weld centre. The secondary dendrite arm spacing was found to be 2-5µm and the metastable phase δ (Al3Li) was present after welding with a very fine homogeneous distribution of -5nm diameter spheres. Porosity was identified as a major welding defect and was attributed to two distinct formation mechanisms. Firstly, the release of hydrogen gas during welding caused spherical gas bubbles throughout the weld pool. Secondly, the delicate balance of forces within the keyhole resulted in larger irregular shaped pores at the weld centre-line towards the weld root. This second type of pore was virtually absent in full penetration welds. The influence of heating rate to the solution treatment temperature on 8090 CO2 weld metal was assessed and the weld metal grain size was found to be most uniformly small after a heating rate of 1 K/min. A TEM investigation confirmed that the grain boundary pinning dispersoid β(Al3Zr) was responsible for inhibiting grain growth. However, the microhardness and notch-tensile strength of the CO2 weld metal did not depend on the weld metal grain size. Instead, it was suggested that the residual cast structure was responsible for determining the mode of failure and fracture strength. Microstructural studies of CO2 laser welds in RSIPM 8009 and wrought 6061 confirmed the cooling rate of 102-103 K/s predicted for CO2 welds in 8090. However, the 8009 CO2 weld metal did not solidify by epitaxial growth from the fusion boundary, which was the case for CO2 welds in 8090 and 6061. Instead, solidification in 8009 weld pools occurred via many isolated events on primary intermetallic particles. The intermetallic particles had the stoichiometry Al4.5(Fe,V,Si) with the AI.mFe tetragonal lattice parameters. It was qualitatively shown that the 8009 weld microhardness had an inverse relationship with the volume fraction of intermetallic particles. Chemical analysis of the 6061 weld metal confirmed that even when aluminium is alloyed with volatile elements such as Mg it is mostly retained within the weld pool during CO2 keyhole laser welding. It was found that a much higher power was required to obtain a deep penetration weld in 6061 than in either of the other alloys.
44
Howes, Michael. "The design and control of mine refrigeration systems." Thesis, University of Nottingham, 1992. http://eprints.nottingham.ac.uk/29325/.
Full textAbstract:
The research is directed towards modelling the chiller set, the heat rejection and the load subsystems of a complete mine refrigeration system and simulating the performance in order that the design can be optimised and the most cost effective control system determined. The refrigeration load profile for a mechanised mine is complex and primarily a function of surface climatic variations, the strongly cyclic sources of heat resulting from the operation of diesel powered mining equipment and the associated differences in thermal environmental acceptance criteria. Modelling of the central element of the system, the compressor, is based on empirical relationships which use the actual cooling duty and input power rather than general compressor curves using theoretical flow and head coefficients. This has a more general application and is not restricted to a single compressor type. The steady state modelling of five refrigeration systems has included two types of compressor, four types of evaporator, three types of condenser, two types of cooling tower and five types of mine cooling appliances. The research has extended modelling of refrigeration systems by incorporating fully the heat rejection and load subsystems and has demonstrated that relatively complex mine refrigeration systems can be modelled and the simulation results related to actual measurements with an acceptable accuracy. This has been further improved by testing the system elements and adjusting the theoretical performance analysis where necessary. These adjustments concern either the more difficult to assess factors such as evaporating and condensing heat transfer coefficients or factors influenced by unusual operating conditions. The research has shown that, despite the complexity of the load profile and the refrigeration system, modelling and simulation can be used effectively to optimise both the design and the control system.
45
Moll, A. T. J. "A study of optimisation methods applied to methane recovery and mine ventilation systems." Thesis, University of Nottingham, 1993. http://eprints.nottingham.ac.uk/29386/.
Full textAbstract:
The current trends towards increased coal production from seams at greater depth has led to increased demands being placed on the methane drainage and mine ventilation systems. This study has been directed towards the development of computer models to simulate and analyse the gas flows in methane drainage ranges and the airflow and pressure distribution in mine ventilation networks. The first part of this thesis describes the conventional techniques of methane drainage currently employed and the mathematical approach used to model gas flow in the methane drainage range. It also discusses how, when combined with measured underground data, predicted results can be used to assess the performance of the range. Subsequent analysis techniques will suggest measures that can be undertaken to optimise this performance and assess the effect of selective network reconfiguration. The second part of the thesis includes a discussion of the increasing application of booster fans in U.K. underground coal mines and a critical analysis of the mathematical methods used to model airflow and pressure distribution in mine ventilation networks. One particular method was adopted in a simulation model used to analyse networks with booster fans and specified face airflows. Both simulation models developed have been used to analyse representative underground methane drainage ranges and mine ventilation networks. The thesis concludes that the accuracy of the methane drainage models can only be guaranteed when developed in conjunction with suitable measured data. The mine ventilation model requires user guidance through the solution and analysis procedure. Results are presented in a simple graphical manner and this approach, rather than the 'black box' non interactive approach, is to be favoured in the analysis of mine ventilation networks.
46
Schofield, Damian. "Surface mine design using intelligent computer techniques." Thesis, University of Nottingham, 1992. http://eprints.nottingham.ac.uk/13113/.
Full textAbstract:
Surface mine planning involves the results of algorithmic numerical calculations being used by engineers to make informed decisions relating to the design. The Department of Mining Engineering at the Unversity of Nottingham has in the past been involved in developing modular algorithmic packages. The emphasis of the computer research has now altered. Smaller specialised systems are now being developed to cover individual aspects of the design process. Artificial intelligence techniques are being introduced into the mining environment to solve the planning problems often associated with the large amounts of uncertain information needed by the engineer. This thesis is concerned with the development of MINDER, a decision support system capable of assisting the mine planner in the complex task of optimum surface mining equipment selection. An expert system shell has been used to create a series of individual application modules, each containing a multi-level knowledge base structure. An information handling system has been developed which is capable of storing consultation information and transfering it between knowledge bases and between application modules. Once an effective method of information handling had been achieved the flow of control between the system knowledge bases was rapid and followed complex inferencing routes. Most of the commercially available packages mathematically model a deposit, calculate volumes and simulate operations. One of the aims of the MINDER system was to integrate with other software, for example MINDER is capable of reading volumetric and material information from Surpac mine planning software. Geological data and manufacturer’s equipment specifications are stored in DbaseIV databases. The expert system is capable of writing macros based on the consultation and performing complex relation operations involved in the elimination and ranking of equipment. In a similar manner macros are written to control the simulation package GPSS which used to simulate operations using the selected equipment. A range of ‘in-house’ Pascal software is used for numerical calculations and matrix manipulation, an example of this is the fuzzy logic software used to handle uncertain information. Another aspect of the project is an investigation into the use of machine learning techniques in the field of equipment selection. Knowledge induction software has been used to induce new rules and check those produced in the MINDER system. Various experiments have been carried out using neural network software to produce equipment selection models. Training data taken from the mining industry was used on both these systems and the results were tested against MINDER consultation results.
47
Fair, G. H. "The effect of shot peening on fatigue and fretting-fatigue of aluminium alloys." Thesis, University of Nottingham, 1988. http://eprints.nottingham.ac.uk/12723/.
Full textAbstract:
Plain-fatigue and fretting-fatigue tests have been carried out on the two peak-aged, high-strength aluminium alloys, 7010 and 8090, in the unpeened and shot peened conditions. Shot peening produced a highly deformed surface containing many deep dimples and folds from which fatigue cracks rapidly initiated. Although initiation was early, propagation through the peened surface layers was retarded by the residual compressive stresses introduced by the peening treatment; this retardation being greatest at a depth corresponding to that of the peak residual compressive stress. Shot peening improved the plain-fatigue properties of the 7010 alloy at high applied stresses and this improvement decreased as the applied stress was reduced. A reversed trend was observed in the 8090 alloy with shot peening being beneficial to the fatigue properties at low applied stresses and detrimental at high applied stresses. The poor resistance of the 7010 alloy to fretting-fatigue was eliminated by shot peening and this was again attributed to the residual compressive stress induced by the peening treatment. Since the 8090 alloy in the unpeened condition is relatively insensitive to the effects of fretting, shot peening resulted in only a minor improvement in the fretting-fatigue behaviour of this alloy.
48
Moloney, Kenneth W. "An analysis of airflow patterns in auxiliary ventilated drivages." Thesis, University of Nottingham, 1997. http://eprints.nottingham.ac.uk/12364/.
Full textAbstract:
In recent years the drivage advance rates achieved within the UK coal industry have increased. In the 1980's average drivage rates were 35m per week compared to the 100/150m per week possible today. These extended rates of advance have resulted in an increase in the potential methane, dust and heat generation within the vicinity of the drivage face. In order to effectively disperse this additional pollutant load a controlled increase in air quantity is required. Although advance rates have changed, current auxiliary ventilation practice has not. UK mining law requires that the fresh air must be delivered to within 5m of the face. This has lead to the wide spread adoption of the use of overlap auxiliary systems within mechanised drivages, since a pure forcing system set at this distance from the face would lead to excessive airborne dust. UK mining law does not at present consider on-board mounted exhaust scrubber fans to constitute an effective overlap fan within mechanised drivages. Consequently an additional overlap exhaust fan is required to be installed within such drivages. In an attempt to determine whether working conditions could be safely and economically improved within mechanised rapid development drivages utilising an on-board mounted exhaust fan, a series of preliminary full scale gallery trials were conducted. A summary of the principal findings of these trials is presented together with an outline of a series of representative CFD simulations. This thesis examines the accuracy of CFD simulations for auxiliary ventilated headings. This is achieved by utilising Laser Doppler Anenometry (LDA) in a scale model representative of an underground heading and a detailed underground measurement programme conducted in production headings. These measured airflow values are then compared with representative CFD simulations and conclusions
49
Dixon, Darron William. "A statistical analysis of monitored data for methane prediction." Thesis, University of Nottingham, 1992. http://eprints.nottingham.ac.uk/12977/.
Full textAbstract:
This research describes an investigation into the application of a statistical method for the prediction of methane concentration in longwall coal districts. An important and necessary part of the research was the acquiring of representative mine environmental and coal production data and a number of shortcomings were identified in this area. The monitored data was used to build univariate time series models of general air body methane concentration, air velocity, barometric pressure, coal production and methane drainage variables of varying timescales according to the Box-Jenkins method of time series analysis. The univariate models were used to identify causal relationships between methane concentration and its explanatory variables. Coal production was found to be the dominant variable in the determination of the quantity of methane emitted and where appropriate, multivariate time series models were built in which expressions for methane concentration in terms of coal production were obtained. Forecasts of methane concentration values were generated from both univariate and multivariate models and a comparison was made of their forecasting capabilities. Finally, suggestions were made as to the potential use of time series models for application to mining process control.
50
Al-Harahsheh, Mohammad. "A fundamental investigation into the microwave assisted leaching of sulphide minerals." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/11075/.
Full textAbstract:
Microwave assisted leaching has been investigated in an attempt to improve both the yield of extracted metal and reduce processing time. This is especially pertinent in view of the increased demands for metal and more environmentally friendly processes. This work reports a fundamental study on the influence of microwave energy on the dissolution of sulphide minerals. Chalcopyrite and sphalerite were chosen as model materials due to their economic importance and the diversity of their heating behaviour in a microwave field (chalcopyrite being an excellent microwave heater and sphalerite being an extremely poor microwave receptor). Chalcopyrite leaching has been carried out in ferric sulphate and ferric chloride under both microwave and conventional conditions. Conventionally, it was found that chalcopyrite dissolution in ferric sulphate seems to be limited by surface reaction control. More importantly, it has been shown that specific fracture planes on chalcopyrite particle surfaces experience selective leaching, which was revealed by SEM and ToF-SIMS surface analysis. The preferential attack on particular planes is speculated to be linked to different chemistry of some cleavage planes within the chalcopyrite crystal. In the ferric chloride system, however, it was found that cupric chloride, a reaction product of chalcopyrite with ferric sulphate, may play an important role in the dissolution process. Leaching of both chalcopyrite and sphalerite in ferric sulphate under microwave conditions has shown enhanced recoveries of metal values compared to that produced conventionally. It has been demonstrated that the enhanced copper recovery from chalcopyrite during microwave treatment is as a result of the selective heating of the mineral particles over the solution which was found to be highly lossy. In addition, it is suggested that high loss leaching solutions will develop a superheated layer close to the periphery of the reaction vessel (due to the small penetration depth) which creates localised heating compared to the bulk solution temperature. The enhanced recovery of zinc from sphalerite seems to occur as a result of only the presence of the superheated layer. If leaching takes place within this layer, an apparent rate increase will be noted with respect to the measured bulk temperature. The hypotheses of selective heating (for chalcopyrite) and the effect of penetration depth (for chalcopyrite and sphalerite) were supported by the negligible difference between the activation energy values under microwave and conventional conditions for both chalcopyrite and sphalerite. Furthermore, the measurements of dielectric properties of the leaching solutions have shown that such solutions are highly lossy and characterised by a penetration depth of an order of about 3 mm. Finally, numerical electromagnetic simulations showed that chalcopyrite particles could be heated selectively when micro-waved within highly lossy leaching solutions due to their high conductivity. It is concluded that the dielectric properties of both the solid and liquid phases, the dimensions of the reactor and the position of solid particles within the reactor determine the leaching outcome. More importantly, it is likely that the enhanced recoveries observed are not likely to be as a result of a so called "non-thermal microwave effect" but rather as a result of thermal effects.