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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Numerical Investigation of Multiple-Impinging Slot Jets in the Gas-Jet Wiping of Liquid Zinc Coatings

Tamadonfar, Parsa 09 1900 (has links)
<p>A turbulent impinging slot jet is a device which is used in various industrial applications such as glass tempering, heating of complex surfaces, cooling of turbine blades, cooling of electronic devices and in the continuous hot-dip galvanizing line, which is the focus of this study. An impinging slot jet is used to control the zinc film thickness on the sheet substrate to reach uniform product coating thickness by applying a pressure gradient and shear stress distribution on the moving substrate, after immersion in a bath of molten zinc. The impinging jet wipes the excess molten zinc from the steel strip through the combined effects of a pressure gradient and shear stress distribution on the steel strip.</p> <p>In this study, the fluid flow of three multiple-impinging slot jet configurations discharging air at high velocity on a moving substrate were investigated numerically. Computational fluid dynamics was used to determine the wall pressure results and wall shear stress distributions due to the multiple impinging slot jets, and these results were used as boundary conditions in an analytical model to estimate the final liquid zinc thickness on the substrate. The standard k - ε turbulence model with non-equilibrium wall treatments was used to capture the turbulence parameters in the flow field.</p> <p>The knowledge of using multiple-impinging slot jets in the hot-dip galvanizing line process as a wiping actuator is quite limited. There is not any systematic work available in using these devices as a wiping actuator. In this study, three models of multiple slot jets were developed numerically with the goal of estimating the coating weight on the moving sheet substrate. The conventional model of a single-impinging slot jet was used as a base case for comparing the wall pressure results, wall shear stress distributions and consequently the coating weight data on a moving substrate with different multiple-impinging slot jet configurations. Adjusting the various process parameters such as main slot jet Reynolds number (Re<sub>m</sub>), auxiliary slot jet Reynolds number (Re<sub>a</sub>), plate-to-nozzle ratio (z / d) and sheet substrate velocity (V<sub>substrate</sub>) allows the producers to control the coating weight on a moving sheet substrate.</p> <p>For this study, the numerical simulations were solved using FLUENT commercial code. A comprehensive set of numerical modeling over a wide range of process variables was performed for all configurations in order to present a broad summary of the coating weight trends in the wiping process. A full analysis of the wall pressure distributions and wall shear stress results, as well as coating weight estimation generated under different impinging slot jets have been presented in this study.</p> / Master of Applied Science (MASc)
22

Stability of Thin Pipes with an Internal Flow

Myklatun, B. 09 1900 (has links)
<p>The stability behaviour of a thin clamped-ended pipe with an internal flow is determined. Classical potential flow theory is used to determine the unsteady fluid forces and the motion of the pipe is represented by the Flugge-Kempner equation. The solution is obtained using Fourier integral theory and the method of Galerkin.</p> <p>Theoretical results are compared with experiments as well as previous work.</p> / Master of Engineering (ME)
23

Electrical Discharge Texturing of Cutting Tools

Tovey, Josh 09 1900 (has links)
<p>During metal removal operations, friction occurs at the interface between the rake face of the cutting tool and the chip. Tool rake face friction adversely influences the chip formation process and consumes about 25% of the total cutting energy. Friction in cutting can be controlled and reduced by introducing a lubricant into the tool-chip interface, however the effectiveness of this is a function of the cutting speed and uncut chip thickness, among other factors. Lubricant penetration was determined in the 1970's to be a result of capillary action through channels resulting in part from the roughness of the tool rake face and the mating chip face. Recent investigations have looked at increasing the penetration and effectiveness of lubrication by engineering the tool surface to promote and retain lubricants by introducing a texture on the tool rake face.</p> <p>This thesis details methods used for surface engineering the rake face of cutting tools focusing on the novel application of electrical discharge machining (EDM) to obtain the desired texture, with a view to facilitating lubricant penetration and retention. A significant enhancement in machining performance consequent to such tool face texturing is demonstrated. The functionality of such surfaces is discussed as well as the texturing process, application areas and limitations.</p> / Master of Applied Science (MASc)
24

High Volume Closed Loop Machining Simulation

Perry, Brian 09 1900 (has links)
<p>Statistical Process Control (SPC) provides tools to monitor process quality and productivity. When coupled with closed loop control theory, SPC algorithms can be utilized to compensate for various error sources in stable, high volume, discrete part manufacturing processes. These error sources include environmental effects, tool wear, measurement, and material errors.</p> <p>Closed loop machining cells must be analyzed from both Quality and Manufacturing Engineering perspectives for efficient and successful implementation. Discrete, stochastic, time event manufacturing simulation is used to analyze process organization, data flow and control system performance. SPC and Engineering Process Control (EPC) control algorithms are compared using data gathered from a high volume machining process involving steel turned components with a critical machined surface.</p> / Master of Applied Science (MASc)
25

Tribological Characterization of Surface Engineered Tooling for Metal Cutting Applications

Biksa, Andrew 08 1900 (has links)
<p>The objective of this research was to develop a bench scale apparatus (tribometer) for mimicking the friction and wear conditions on the rake face of a metal cutting tool. The motivation for this study was to save test material costs, reduce machine downtime for testing, increase the number of test replicates and effectively add a reliable testing tool to characterize metal cutting operations and coating performance. The tribometer provides useful results approximately 8 times faster than an industrial machine once all materials have been obtained.</p> <p>This study focuses primarily on isolating and studying the adhesive conditions on the seizure zone of the rake face. The setup simulates subsurface plastic flow in high temperature, near seizure conditions. This unit was constructed as a modified Brinell hardness test. A spherical tipped pin (3mm diameter) made of tooling material and treated with a coating is loaded under high stress and high temperature into a flat disk made of the workpiece material. The disk then rotates. The pin is aligned such that it is on the axis of rotation of the disk to produce near zero seizure like velocity. A high resolution reaction torque sensor measures the friction stress. The test unit is capable of simulating normal stresses of 0-4GPa and temperatures from room temperature up to 700-800°C depending on the specimens and heating patterns required.</p> <p>This study focused on coated and uncoated cemented carbide pins with 6% cobalt. The workpiece materials used were Ti6Al4V and Inconel 718. 2 cases were tested for each workpiece. First the uncoated pin was tested, followed by an AlTiN Xceed® coating from Oerlikon Balzers®. Research conducted on an industrial machine has shown positive correlations with the tribometer measurements and agrees with the findings of our colleague Dr. L.S. Shuster in Russia who uses a similar test setup. The wear of the coated samples was lower than the uncoated samples.</p> <p>The coefficient of friction (COF) was found to be the most suitable parameter for calculating tool performance. In general, the tests completed by the MMRI and Dr. Shuster (Fox-Rabinovich, Yamamoto and Aguirre, et al. 2010) showed that COF in similar rake face seizure conditions of a cutting tool is in the range of 0.2 - 0.35. The MMRI tribometer COF is calculated as follows:</p> <p><sup>μ</sup><sub>MMRI</sub>=(3*M<sub>TOT</sub>)/(2*F<sub>N</sub>*R<sub>IND</sub>)=Ʈ/σ=F<sub>F</sub>/F<sub>N</sub></p> <p>Here M<sub>TOT</sub> is the reaction torque measured, F<sub>N</sub> is the normal load applied and R<sub>IND</sub> is the outer radius of the disk print whether a spherical imprint or a flat circular scratch. Temperature was found to be the most important variable affecting friction and it was also the most difficult variable to accurately measure. The interface temperature and the temperature gradient within the workpiece/disk material are the most significant thermal variables.</p> / Master of Applied Science (MASc)
26

Microfluidic Reference Electrode for Use in BioFET Sensor Systems

SafariMohsenabad, Salman 11 1900 (has links)
<p>Biosensors, used in medical diagnostics, increasingly use genomic information (DNA) to rapidly and accurately determine the species present in the sample. Since, the DNA inherently has a negative charge, electrical methods provide a direct technique to sense it. This transduction has been achieved by using a biological Field-Effect-Transistor (BioFET) structure, where hybridization of a single stranded DNA (indicative of the biological species) with a complementary strand from the sample solution causes a change in the transistor characteristics that could be read out electrically. The accuracy of sensing using the BioFET is critically dependent on imposition of a highly stable potential which is performed using a reference electrode.</p> <p>Design and fabrication of a miniaturized silver/silver chloride (Ag/AgCI) reference electrode is introduced in this thesis for use in BioFET. The electrode consists of Ag/AgCl wire which is embedded into a PDMS microchannel enclosed by a microcontact printed nanoporous polycarbonate membrane. The microchannel is filled with KCI solution as the internal solution.</p> <p>By modifying the electrodeposition method, nanosheet AgCI structure was grown rather than the conventional globular morphology. The bare Ag/AgCl potential drift with the former morphology was found to be</p> <p>In conclusion, a modified electrodeposition method and free-diffusion liquid junction micro fluidic reference electrode is proposed to improve the stability and extend the lifetime of a reference electrode with very low potential drift.</p> / Master of Applied Science (MASc)
27

Laser Interferometric Investigation of Microlayer Evaporation for Various Levels of Subcooling and Heat Flux

Voutsinos, Cosmos M. 03 1900 (has links)
<p>An experimental study of the growth and evaporation of the microlayer, underlying a bubble during nucleate boiling heat transfer to dichloromethane, is presented. The influence of heat flux (8000 Btu/hr ft² - 20,000 Btu/hr ft²) and subcooling (0ºF - 13.5ºF) upon the rates of growth and evaporation, have been studied using laser interferometry and high speed photography through the glass heater surface on which bubbles were nucleated. The results presented indicate that the microlayer thickness is of the order of 5 μm. The analysis of these results confirms that the microlayer evaporation phenomenon is a significant heat transfer mechanism representing approximately 25% of the total nucleate boiling heat transfer rate for the conditions investigated. As subcooling is increased from saturation, the contribution of the microlayer evaporation to the total heat transfer rate varies in accordance with two interacting processes in the region investigated. This variation appears as an initial decrease followed by an increase.</p> / Master of Engineering (ME)
28

Effect of Ageing Heat Treatment on the Hardness and Tensile Properties of Aluminum A356.2 Casting Alloy

Liu, George Y. 27 November 2009 (has links)
<p>The aluminium A356.2 casting alloy is one of most popular alloys for shaped casting of automotive components because of its high strength to weight ratio and the ability to heat treat to attain fairly high toughness. Besides Al, the alloy has Si and Mg as the principal alloying additions to aid in the precipitation of the Mg<sub>2</sub>Si phase in the primary Al matrix to strengthen the alloy during heat treatment. Presently, the T6 heat treatment temper is most used on cast components from these alloys. Commercially, in the T6 temper, the component is solution heat treated at around 540<sup>◦</sup>C for about 10 to 12 hours immediately followed by quenching in water maintained at 80<sup>◦</sup>C. The component is then left to natural age at room temperature for about 8 to 10 hours followed by artificial ageing at around 155<sup>◦</sup>C for about 6 to 10 hours. This T6 temper treatment process has been followed for many years and adopted from the 6xxx series Al wrought alloy where the strengthening precipitate is Mg<sub>2</sub>Si as well. No significant research has been carried out to evaluate to optimize the T6 heat treatment in A356.2 casting alloys, specifically, the natural ageing phenomenon adopted from the 6xxx series alloy where the Si to Mg ratio is between 1 and 3, has not been optimized in A356.2 alloy, wherein, the ratio Si to Mg is between 4 and 6. Hence, the mechanism of redistribution of Mg and Si atoms during the natural and artificial ageing process would have to be studied for the A356.2 alloy and the process optimized to attain favourable mechanical properties.</p> <p>In this study, the mechanism of Mg and Si atoms redistribution during the process of natural ageing has been proposed. Additionally, the effect of natural ageing combined with the artificial ageing process on the mechanical properties of the cast component has been quantified. The results of this study propose that the extent of natural ageing in A356.2 alloy depends on the desired combination of strength and elongation in the cast component. A high strength (~230 MPa) and low elongation (~2%) could be achieved if the natural ageing process at room temperature is limited to less than one hour after solution heat treatment and quenching in water at 80°C, and low strength (~195 MPa) and high elongation (~8%) could be achieved for natural ageing of about 6 hours at room temperature prior to the artificial ageing treatment. The recommendations are valid for solutionizing the components at 540<sup>◦</sup>C for 12 hours, followed by quenching in water at 80<sup>◦</sup>C and an artificial ageing at 155<sup>◦</sup>C for various times.</p> / Master of Applied Science (MASc)
29

Modelling Phase Change Material Thermal Storage Systems

Bailey, Joanne M. January 2010 (has links)
<p>In order to increase the overall efficiency of energy use in a community, excess thermal energy from inefficient processes can be stored and used for heating applications. A one-dimensional analytical conduction model is therefore developed for sizing of phase change material thermal energy storage systems. The model addresses rectangular channels of phase change material separated by flow channels for the addition and removal of thermal energy. The analytical model assumes a planar melt front and linear temperature profiles throughout the thermal storage cell. Heat flux and interface temperatures are calculated at various melt fractions based on a quasi-steady electrical analogue analysis of the instant in question. Compensation is made for the sensible energy change between melt fractions by adding this energy at the calculated heat flux. A two dimensional, conduction only computational fluid dynamics model is used to compare the response of the analytical model to changes in the input parameters and shows good agreement. A test apparatus and a three dimensional computational fluid dynamics model are also created and melt-time results compared to analytical model predictions. These comparisons also show good agreement. Finally, a thermal storage system is sized for a specific application, H<sub>2</sub>Green Energy Corporation's Distributed Storage System, with sizing based on the heat load requirements of McMaster Innovation Park during the winter months. Technical feasibility of this system is shown with analysis also included on economic feasibility. It is determined that the analytical model is sufficient for initial assessment of phase change material thermal energy storage systems where detailed geometry is unavailable. Recommendations are made for further validation of the model and the development of a phase change material properties database. Suggestions are also presented on additional sources of revenue for the H<sub>2</sub>Green Distributed Storage System that will increase its economic feasibility.</p> / Master of Applied Science (MASc)
30

Controlled Diffusion Solidification for Tilt Pouring casting process

Birsan, Gabriel 17 August 2009 (has links)
<p>Increased efforts have been undertaken to develop advanced casting (near-net shaped) processes and materials to attain high-integrity cast components with improved mechanical properties and performances. Semi-Solid Metal (SSM) process is one such process route where in typical binary eutectic alloys with suitable alloying additions could be cast from a two phase (solid and liquid) state into a near net shaped component. The SSM technology has been feverishly developed globally via two fundamental processing routes, namely, thixocasting and rheocasting. The use of the former process has been diminishing in recent years due to economic disadvantages inherent to the process and the development of rheocasting route has been dominant. In this process the new SSM processing route in Controlled Diffusion Solidification (CDS) has been validated by carrying out shaped casting in a tilt-pour casting process. Additionally, the project has shown for the first time that it is viable to shape cast Al wrought alloys which have been traditionally impossible to do so. In CDS technology two precursor alloys with specific chemical composition and melt temperatures are mixed in a controlled manner and subsequently cast into a shaped component. The process yields components with a non-dendritic morphology of the primary phase during solidification in the resultant microstructure. Further, CDS circumvents the problems of hot tearing during casting which has been the primary deterrent in casting Al wrought alloys into shaped castings. The project has shown that CDS technology can be used for commercial casting of sound components with Al wrought alloys by using three alloys, namely, 2024, 6082, 7075 Al alloys. The objectives of the project were achieved by designing, manufacturing and validating a tilt-pour casting equipment along with a standard metal mould to shape cast test bars for tensile and fatigue properties assessment. Alloy compositions, melt temperatures and several process conditions were optimized by laboratory experiments and industrial tilt-pour casting trials. The project was successful in establishing a viable method to shape cast Al wrought alloys, specifically the three example alloys considered and it has been shown that the shaped casting of these alloys were visually sound with good casting integrity, heat treatable and showed reasonable tensile properties. Further, a viable scrap recycling methodology for shape casting AI wrought alloys by CDS has been formulated and validated in this project with 2024 Al alloy.</p> / Master of Applied Science (MASc)

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