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<p>In this study, detailed numerical works are carried out to investigate cladding<br />and superimposed hydrostatic pressure on fracture in metals under tension by using<br />finite element software ABAQUS/Explicit. It is concluded that both cladding and<br />superimposed hydrostatic pressure delay void nucleation and void growth, which<br />results in increasing fracture strain in metals under tension.<br />The influence of cladding on delaying fracture in metals under tension is<br />numerically studied by employing Gurson-Tvergaard-Needleman (GTN) damage<br />model. It is found that cladding has a significant effect on enhancement in materials'<br />ductility due to the fact that cladding increases necking strain which in tum delays the<br />void nucleation and growth. Topological arrangement of cladding in axisymmetric<br />tensile round bars shows no noticeable effect on necking but significantly affects<br />fracture strain.<br />The influence of superimposed hydrostatic pressure is numerically<br />investigated on sheet metals under plane strain tension by using GTN damage model.<br />It is found that superimposed hydrostatic pressure has no noticeable effect on necking<br />but significantly delays fracture initiation due to the fact that superimposed<br />hydrostatic pressure delays or completely eliminates the nucleation, growth and<br />coalescence of microvoids or microcracks.</p> / Master of Applied Science (MASc)

<p>The objectives of this work are (i) to develop a numerical model for electrohydrodynamic micropumps, (ii) to investigate the effect of using a conductive agent in the working fluid to enhance the pump performance and (iii) to investigate the use of pulse voltage on EHD micropumps.</p> <p>A numerical model was developed that incorporates a charge model at the emitter electrode that is coherent to the electric field. The model results were found to be in good agreement with previous experimental results. A parametric study was performed to investigate the effect of the channel height and multi-stage spacing on the pump performance. Reducing the channel height reduced the flow rate but increased the pressure head, while increasing the multi-stage spacing improved the pump performance.</p> <p>The effect of using conductive agents in the working fluid was investigated using Ferrocene in HFE-7100. The Ferrocene was found to significantly improve the pump performance. However, at high voltages, the pressure could not be sustained for long periods of time. The effect of an applied pulse voltage on the performance of the micropumps was studied. A maximum pressure 3512 Pa was achieved at an applied pulse voltage between 500 V to 800V, pulse repetition rate of 5 Hz, and duty cycle of 60%.</p> / Master of Applied Science (MASc)

<p>Small scale Vertical Axis Wind Turbines (VAWTs) show potential for urban rooftop installations where they can capture the highly unstable, turbulent wind flow patterns which are typical in an urban environment. Being axisymmetric, they are omnidirectional turbines which respond well to changes in wind direction, unlike their horizontal axis counterparts. Wind tunnel experiments were performed on a small scale, 2.5m diameter by 3m high, 3 bladed H-Darrieus VAWT. The effects of blade preset pitch and blade mount-point offset were investigated. Local flow visualizations were observed on the inner surface of a blade near the lower strut by recording video of the behaviour of Mylar tufts during turbine operation for comparison with a 2-D Computational Fluid Dynamic (CFD) model. Experimental data is presented for a range of tip speed ratios, at a nominal wind velocity of 10m/s for both blade pitch and blade offset tests.</p> <p>The results of the blade preset pitch tests indicate performance increases with increasing toe-out pitch, to a limit, followed by a sharp decrease in performance as toe-out is continually increased. Performance decreases were experienced for all toe-in pitch presets. Identical behaviour was seen with experiments involving blade mount-point offsets which were geometrically equivalent to blade pitch presets. Results of tuft flow visualization tests indicate the regions during which the blade is experiencing reversed flow, and compare well with velocity vector data obtained from CFD simulations. The duration the inner blade surface experiences full stall is observed to decrease with the increase of toe-out preset pitch. Incipient stall is observed to be delayed as blade tip speed ratio is increased. Thrust curves are also presented and indicate a decrease in upwind pass and increased downwind pass perfonnance as toe-out is increased. As the tip speed ratio is increased, the interaction of the blade with its shed vortex from the upwind pass is diminished. This investigation shows that high solidity VAWTs are sensitive to relatively small changes in blade preset pitch and mount point offset and therefore care should be taken when designing turbine blades so as to avoid a toe-in condition that could adversely affect turbine performance.</p> / Master of Applied Science (MASc)

<p>To investigate the effects of mechanical loading on the rat and mouse forelimb, male Sprague Dawley rats and male C57/BL-6 mice forelimbs were cyclically loaded in axial compression. Two studies were performed, one to examine woven bone formation in both the rat and mouse forelimb, and one to examine lamellar bone formation in the rat forelimb. Both types of bone formation were induced through an acute loading event.</p> <p>Repeatable levels of fatigue damage were induced in both the rat and mouse ulna, yielding a consistent woven bone response. Rats formed more woven bone than mice. Woven bone formed by the rats was evenly distributed along the medial cortex versus woven bone formed by the mice was more abundant towards the posterior side of the medial surface.</p> <p>150 cycles of rest inserted loading to a peak load of 30 N was found to induce lamellar bone formation with the greatest apposition rate. Apposition rate was more strongly influenced by peak loading rather than number of loading cycles. At the 30 N loading level, 300 loading cycles induced woven bone formation in two of the five animals.</p> <p>Finite element models were created to examine the mechanical environment of both the rat and mouse ulna during compressive forelimb loading. Stress distribution in the rat ulna was found to be distributed along the medial surface of the rat ulna. Stress distribution was biased to the posterior side of the medial surface on the mouse ulna. These stress distributions supported the bone formation observed. Maximal stress occurred in both the rat and mouse ulna at the same location failure occurred during monotonic and fatigue to failure tests conducted on both rat and mouse ulnas.</p> / Master of Applied Science (MASc)

<p>Making large RP parts is always a challenge for common commercial RP machines or other CNC machining process. Either it is not possible to fabricate the large RP models, or can only be done at high cost.</p> <p>This thesis investigates a new method to make large RP parts in a very rapid and cost-effective way, and the part size could be theoretically unlimited. A software program for slicing 3D CAD models is developed in the Autodesk Inventor VBA environment to generate DXF files, and a common 3-axis CNC router is employed for cutting the sliced layers from sheet material by importing the DXF files from the slicing software tool. The sheet material sliced layers are laminated together to form the RP models with staircases on the laminated body surface, then epoxy resin filler is applied to cover the staircases. The surface finishing process such as sanding and coating makes the RP model closely match the original designed part shape.</p> <p>By directly slicing a 3D CAD model in Inventor with the slicing software tool, the cutting profiles are obtained and saved in the DXF file format. The errors usually caused by slicing STL files with most conventional RP machines are eliminated and hence the geometry data is more accurate for making sliced layers. The slicing process becomes quite simple with the help of the slicing software tool, and it only takes a few minutes to get the DXF files for CNC router cutting.</p> <p>Three different slicing and CNC router cutting methods are discussed in this thesis. For different shapes of 3D CAD models, an appropriate slicing method can be applied to reach the optimal results of RP model making.</p> <p>The uniform slicing method is an effective way to slice large parts and generate sliced layers with the same thickness; the adaptive slicing method is a supplement for uniform slicing and makes thinner layers to save time for post-finishing such as staircase filling and surface grinding; and the adaptive slope cutting method is developed for choosing different sloped cutters for CNC router to cut sliced layers with standard grooving router bits.</p> <p>The experiment is performed to make RP models of a sailboat keel pattern with the different slicing methods. Measurement is done for the fabricated RP models for comparing the surface deviations between the original designed 3D CAD models and the fabricated RP parts. The deviation plot made by software Geomagic shows that the RP model closely matches the original 3D CAD model, the surface deviation is mostly within lmm between the RP model and CAD model in the research experiment. The fabrication cost for RP model is also analyzed based on the experiment models in this research.<br />iv</p> / Master of Applied Science (MASc)

<p>Thermal stratification in solar energy storage tanks plays an important role in enhancing the performance of solar domestic hot water (SDHW) system. The mixing that occurs when hot fluid from the solar collector enters the top of the tank is detrimental to the stratification. Mathematical models that are used for system analysis must thus be able to capture the effects of this inlet jet mixing in order to accurately predict system performance. This thesis presents a Computational Fluid Dynamics (CFD) study of the heat transfer and fluid flow in the thermal storage tank (TST) of a solar domestic hot water system employing a vertical inlet jet geometry. The focus of the thesis is on the studying the effects of inlet jet mixing on the thermal stratification in the tarue Predictions of transient temperature profiles were assessed by comparing to experimental data from the literature. CFD was then used to study how the predicted mixing in the TST was affected by parameters such as the inlet velocity and temperature, pipe diameter and the selected turbulence model. From this study of the mixing, a one dimensional empirical model was developed to predict the temperature distribution inside the TST. The model was found to provide improved predictions of the transient axial temperature distribution in comparison to the plug-flow model which is commonly used in the broader system analysis codes.</p> / Master of Applied Science (MASc)