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Mechanical Engineering

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  • ItemOpen Access
    A Numerical Modelling Approach to Study the Impact of Ventilation Configurations on Airborne Transmission in Indoor Environments
    (2024-03-16) Khan, Arma Mantissa; Freire-Gormaly, Marina
    The airborne transmission of COVID-19 has been a topic of significant controversy since the pandemic began. Research was needed to demonstrate the importance of airborne transmission and develop tools to recommend appropriate control measures. This study aimed to analyze the factors that impact airborne transmission, find techniques for infection risk minimization, and develop methods to compare different control measures on infection risk. Computational Fluid Dynamics (CFD) studies were conducted to analyze the impact of ventilation layout and infection source location in indoor spaces. A novel spatio-temporal risk model was further developed to quantify the risk in indoor spaces based on different control measures. Conclusions have been made that the ventilation layout and infection source locations can significantly impact the risk of airborne transmitted infection. Further research into building design and airborne transmission minimization techniques is urgently needed to prepare for airborne infectious diseases that may emerge in the future.
  • ItemOpen Access
    Design of Intermittently Operated Reverse Osmosis System and Membrane Coatings for Enhanced Fouling Mitigation
    (2024-03-16) Truong, Brandon; Freire-Gormaly, Marina
    Access to potable water is becoming an increasingly important issue, especially in communities residing in remote, off-grid locations. The use of solar powered reverse osmosis systems has been shown to be a viable solution to delivering clean drinking water. There is a need to improve the fouling resistance of the membranes to reduce costs, maintain water quality, and keep water output reliable. Membrane coatings have been shown to enhance antifouling properties, but more research is required. A lab-scale reverse osmosis (RO) system is developed to enable testing and monitoring of intermittent water treatment processes. Multiple sensors used to measure water quality and permeate flow were incorporated inline to gather data in real time. Membrane coating technology used to improve treatment performance through enhanced antifouling properties was studied. Several coating possibilities were considered for criteria such as: cost, antifouling & anti-scaling properties, and water output quality.
  • ItemOpen Access
    Low-Cost and High-Throughput Optofluidic Add-on Device for Light Sheet Imaging of Larval and Adult C. Elegans
    (2024-03-16) Rahimpouresfahani, Faraz; Tabatabaei, Nima; Rezai, Pouya
    In this research, we have made modifications to our low-cost light sheet platform, allowing us to capture high-content cross-sectional images of nematodes' nervous systems at earlier stages of development and with higher throughputs. Our platform was put to the test in imaging larval and adult pan neural worms, as well as in analyzing control and neurotoxin-exposed worms. Additionally, we utilized a new transgenic worm model for Parkinson's disease and were able to detect a fluorescence difference between larval and adult stages. The result is a vast dataset of high-content images that will be invaluable in future research.
  • ItemOpen Access
    Development, Processing and Characterization of Advanced Alumina Matrix Multi-material Nanocomposites Reinforced with Zirconia, Graphene and Carbon Nanotubes
    (2023-12-08) Duntu, Solomon Hanson; Boakye-Yiadom, Solomon
    The demand for tough materials in extreme conditions has grown due advanced technology requirements, such as high pressures (> 90GPa), elevated temperatures (> 2000°C), and radiation exposure, has grown substantially. Advanced ceramics, particularly alumina (Al2O3), with their low weight, hardness, and chemical resistance, are promising candidates. However, their inherent brittleness (low fracture toughness) has limited their applications. To address this, researchers have incorporated sub-micron and nano-scale reinforcements like zirconia (ZrO2), graphene (GN), and carbon nanotubes (CNTs) into alumina to create composite materials. However, challenges remain in achieving consistent mechanical properties and minimizing trade-offs between fracture toughness (KIC) and strength. This study investigates the impact of single and combined nano-scale reinforcements (ZrO2, GN, and CNTs) on the microstructure, mechanical properties, toughening mechanisms, tribological performance, and functional attributes of monolithic alumina. The nanocomposites were fabricated by uniformly dispersing selected optimal amounts of ZrO2 (4wt% and 10wt%), GN (0.5wt%), and CNTs (2wt%) through a colloidal mixing process, followed by hot-press sintering. The results revealed a uniform distribution of additives within the alumina matrix, leading to significant matrix grain size reduction (up to 80%) in the Al2O3-10wt%ZrO2-0.5wt%GN-2wt%CNTs multi-material nanocomposite compared to pure alumina. Microhardness increased by up to 48% in the Al2O3-10wt%ZrO2-0.5wt%GN-2wt%CNTs multi-material nanocomposites due to refined grain structures and effective load transfer capabilities. Furthermore, fracture toughness (KIC) improved by up to 160%, and bending strength increased by up to 46% in Al2O3-10wt%ZrO2-0.5wt%GN-2wt%CNTs multi-material nanocomposite, due to synergistic toughening and strengthening mechanisms involving pull-outs, crack arrest, and crack bridging by GN and CNTs. This nanocomposite also exhibited up to a 93% reduction in wear rate compared to pure alumina, attributed to wear resistance mechanisms such as micro-crack bridging and intergranular fracture restriction during sliding. Further, the incorporation of GN and CNTs improved the electrical conductivity of monolithic alumina from 10-13 S/m up to 102 S/m (increase up to 15 orders of magnitude), with the Al2O3-10wt%ZrO2-2wt%CNTs nanocomposite registering the highest conductivity value. This was ascribed to the intrinsic electrical properties of carbon nanostructures, percolation effect and the refined grain structure of the nanocomposite which enhances electron mobility by forming continuous networks and pathways.
  • ItemOpen Access
    Aerosol Transmission of COVID-19 and other Airborne Diseases in office environments using Computational Fluid Dynamic Modeling and Machine Learning
    (2023-12-08) Webb, Kishon Winston; Freire-Gormaly, Marina
    The COVID-19 pandemic has shown the world how quickly airborne diseases can spread and the lasting impact they can have. Computational fluid dynamic (CFD) models and simulations and machine learning (ML) are powerful tools that allow engineers to create models to predict and advance tools to fight these airborne diseases. The research in this thesis studied the effects of heating, air conditioning and ventilation (HVAC) strategies in small office spaces. A novel methodology was developed to utilize ML, CFD and parallel computing by utilizing the user defined function (UDF) tool of ANSYS Fluent. It was shown that the resulting risk models were quick and effective at predicting high risk areas using spatial data or predicting regions of high risk over time. Future research will refine this method by creating higher fidelity ML models and investigating a wider range of input and output parameters.
  • ItemOpen Access
    Optothermal Characterization of Nanoparticle Infused Aerogels
    (2023-12-08) Nagi, Mubariz Ahmad; Cooper, Thomas; Freire-Gormaly, Marina
    Here, custom fabricated nanoparticle infused aerogels are presented as a potential material to achieve super insulating and transparent opto-thermal properties. By incorporating nanoparticle solutions within the silicon dioxide (SiO₂) aerogel during the sol-gel process, unique monolithic samples were fabricated and opto-thermally characterized. The pure silica and nanoparticle infused (Zinc Oxide, Antimony doped Tin Oxide, Zirconia Dioxide) silica aerogel samples, through UV-Vis and FTIR measurements, spectrophotometrically demonstrated a solar weighted transmittance of 86, 86, 55 and 78% with measured effective thermal conductivity values of 0.035, 0.050, 0.045, 0.045 W/(m∙K) with an error threshold of ± 0.005 W/(m∙K) using a modified guarded hot-plate technique respectively. The inclusion of nanoparticles within SiO2 aerogels results in reduced transmission (heat loss) in the mid-infrared (MIR) while maintaining high transmission in the visible wavelength region. Importantly, the results show that nanoparticle infusion can be used as a flexible method to tailor the opto-thermal properties of aerogels.
  • ItemOpen Access
    Optical performance of a seasonally adaptive asymmetric compound parabolic concentrator
    (2023-12-08) Lenarduzzi Perez, Gianpaolo; Cooper, Thomas
    Stationary concentrators have the capabilities to supply power in residential and commercial applications, where typical required temperatures range between 20° and 400°. To advance the performance and possible applications of these devices, this work presents an innovative asymmetric stationary concentrator, called Seasonally Adaptive ACPC, which maximizes concentration by semi-annual solar pseudo-tracking. The concentrator is described, and its performance is analyzed using theoretical, numerical, and experimental methods. The former includes the adaptation of the source-acceptance map matching method for ACPCs and the theoretical performance of possible designs; and numerical studies used Monte Carlo ray tracing to investigate optical performance parameters. Experimental efforts involved measuring the optical performance of a practically relevant prototype (ϑin,1=0°, ϑin,2=90°, and a Cg=2×) in Toronto, Canada, using an innovative flux mapping procedure. Through this work, the Seasonally Adaptive ACPC was found to be a low-cost alternative to meet low to medium temperature heating demands at high latitudes.
  • ItemOpen Access
    Impact Loading and Rapid Volumetric Assessment of Braided Composite Structures
    (2023-12-08) Dondish, Alexander Benjamin; Melenka, Garrett
    Braided composites have become a viable alternative to traditional materials in performance-critical applications, with advantages including favourable specific strength and stiffness and highly tailorable properties. However, their inherent complexity and heterogeneity pose challenges in thoroughly assessing their load response. Micro-computed tomography (µCT) offers a method for examining materials and their internal structures through volumetric X-ray imaging. This thesis explores an automated method of rapidly characterizing the internal structures of braided composites subjected to impact testing. The developed methodology is based on algorithms that use image processing techniques to segment and analyze various features in sample volumes. The extracted features in braided composites for study are geometric profiles, voids, and impact damage. The results from the developed algorithms are supplemented with three-dimensional strain measurements by digital volume correlation (DVC).
  • ItemOpen Access
    Stress-State and Strain-Rate Dependent Multiscale Characterization of ARMOX 500T
    (2023-12-08) Mateos, Diego; Boakye-Yiadom, Solomon
    A strain-rate and stress-state dependent experimental characterization is conducted for the parameterization of a triaxiality and lode angle parameter (LAP) dependent Generalized Incremental Stress-State Dependent Damage Model (GISSMO) for ARMOX 500T (AX500) armour steel. 100+ mechanical tests have been conducted which differentiate the effects of triaxiality, LAP, and strain-rate on instability and fracture strains. Quasistatic characterization tests have been conducted at 18 different stress-states abiding by previous GISSMO literature and ASTM standards. LaVision’s Digital Image Correlation (DIC) system is employed in 2D & stereo 3D configurations to acquire high resolution full-field strain measurements. The stain-paths are quantified in the fracture regions of all specimens, from which in-situ equivalent plastic strains are derived. A novel and low-cost Tensile Hopkinson bar has been designed and constructed for dynamic characterization of ductile metals at intermediate to high strain rates (500-1500 /s). High strain rate mechanical tests coupled with high-speed 2D-DIC have been conducted to provide a strain-rate dependent GISSMO extension to the model. Two Hopkinson bars (direct compression, split-tension) have been used to provide lode angle dependent strain-rate hardening data on stress-states of axisymmetric compression and tension covering the lode angle parameter values of -1 and 1, respectively. In addition, two cylindrical inclined compression-shear specimens with varied angles have been impacted at high strain rate to quantify the effect of stress-state on the formation and evolution of Adiabatic Shear Bands (ASBs) and their consequential effect on ductility. This innovative dynamic characterization procedure is conducted to stipulate diligent test matrices and enable improved multiscale terminal ballistics simulations on novel combat vehicle development, with the purpose to increase the predictability of shear plugging. High strain rate axisymmetric compression, compression-shear and tension specimens have been investigated using a combination of optical (OM) and electron microscopy (SEM/TEM) to elucidate their microstructural evolution. Ductile fracture is observed under all stress-states, with changes from mode I to mode II crack formation from positive to negative lode angles. Under axisymmetric dynamic tension, enhanced damage tolerance in comparison to quasistatic loading is found attributed to increased dislocation pileups (work hardening) and subsequent ductile void growth responsible for enhanced plastic flow during necking. Axisymmetric dynamic compression reveals a severe loss of global ductility and strengthening not observed under quasistatic loading, with continuous work hardening until premature fracture and localized hardening in the ASB regions. Compression-shear specimens reveal higher susceptibility to ASB initiation with increasing angle of inclination (shear stress) and corresponding ductility loss due to increased strain localization along the plane of maximum shear. Lastly, ASB multisite microcrack initiation and coalescence, multi-directional cracking, secondary ASBs and bifurcation, nanosized grain refinement, nanoscale twinning, and dislocation cell networks are found within triaxial ASB regions revealing that AX500 has various energy absorbing mechanisms to delay crack propagation and fracture after the onset of ASB initiation.
  • ItemOpen Access
    Fabrication of Collagen Scaffolds with Computer Designed Internal Microarchitecture for Blood Vessel Engineering Using Inverse 3D Printing
    (2023-12-08) Ogato, Joab Ongaro; Sachlos, Eleftherios
    Three-dimensional(3D) printing and bioprinting has been employed in the production of tissues analogs. These tissues can then be used as transplant alternatives or disease models research. While successful thin(<1mm) tissues are reported, thick tissues(>1mm) are still a challenge to engineer due to lack of functional microvasculature. We present a method where we repurpose a commercial 3D printer into an inverse bioprinter. Using biocompatible raw materials we printed a sacrificial mould into which a type I collagen slurry is cast and solidified. After the sacrificial mould is chemically removed, optical computed tomography reveals predefined scaffold microchannel. Immortalized human umbilical vein endothelial cells (HUVEC-hTERT) were seeded in the scaffold microchannels, incubated for 72 hours and assessed for attachment using scanning electron microscopy. Obtained results demonstrate the ability to use the inverse 3D printing method in a repurposed commercial bioprinter to produce scaffolds with predefined microvasculature for thick tissue engineering applications.
  • ItemOpen Access
    Development of Characterization of 3D-Printed Continuous Pitch Carbon Fiber Composites
    (2023-12-08) Olcun, Sinan; Kempers, Roger
    This study looks at the development of 3D printing technologies for the purpose of creating thermally conductive composites using continuous pitch carbon fiber and how various printing parameters affect thermal conductivity of samples. An initial prototype 3D printer was made with a custom dual nozzle extruder to print pitch carbon fibers, initial samples were measured with 37.1 W/mK effective thermal conductivity, this was much lower than what was expected of the samples. Imaging and µCT scanning confirmed fibers were breaking at some point in the process. A heat flow meter in a vacuum chamber was designed and fabricated to measure thermal conductivity of individual tows of carbon fibers to characterize breakage. The printing parameters affecting breakage were diagnosed and it as found that the angle between the nozzle and the printing bed had the greatest impact on breakage after a new printing system was developed using a 6-axis robot arm.
  • ItemOpen Access
    Integrated Two-Dimensional/Three-Dimensional Collagen Scaffolds with Embedded Channels
    (2023-12-08) Fakhri, Neda; Sachlos, Terry; Rezai, Pouya
    We developed a two-step method for simple integration of basement membrane (BM) in a 3D porous scaffold (i.e., interstitial matrix (IM) ) embedded with channels wherein the 2D BM analog was fabricated by casting collagen on a positive master mold and slowly air-dried at room temperature to replicate the microchannel feature on the mold. Then, collagen slurry was poured over the 2D collagen film while it is still supported by the mold and the whole assembly is freeze-dried. The contact printing method was used to enclose channels with another non-patterned integrated collagen scaffold. The channels with and without the 2D BM were tested for leakage. The results showed no leakage when 2D collagen films were included in the scaffolds, even at flow rates as high as 25 ml/min. The present ECM model can be used in modeling tissues containing large vessels where the membrane restricts the permeation of fluid.
  • ItemOpen Access
    Ultra High Temperature Thermal Insulation Materials and the Significance of Opacification in the Suppression of Radiative Transport
    (2023-12-08) Pirvaram, Anahita; Cooper, Thomas
    There is, nowadays, a large shift to high temperature operations in many applications such as industrial processes, power plants, and energy storage applications. Although some current thermal insulation materials show a good performance, they either don’t withstand high temperatures or have a high thermal conductivity at high temperatures. The aim of the present thesis is to develop a pathway to improve the performance of high temperature thermal insulation by suppression of radiative transport. For this purpose, two insulation designs have been investigated: multilayer insulation (MLI) design and volumetric extinction design. The results revealed that MLI design works best with metals. However, they will oxidize or, worse, melt at high temperatures which indicates the performance limitation of multilayer insulation design at high temperatures. On the contrary, the results showed that non-metals, as more stable materials at high temperatures, show a better performance to suppress radiation in the volumetric design.
  • ItemOpen Access
    Surface Roughness and Trip Effects for a Circular Cylinder at Subcritical Reynolds Numbers
    (2023-08-04) Rajavarothayam, Vidushan; Hanson, Ronald; Lavoie, Philippe
    Aerodynamic drag is the major source of resistance experienced by athletes in activities such as road cycling. Over bluff bodies, which is how an athlete is typically modelled, passive flow control methods such as surface roughness and boundary layer tripwires appeared to be particularly relevant in transitioning the local boundary layer at the surfaces to turbulence, resulting in a lower drag at smaller Reynolds numbers. In the experimental study, a cylindrical model equipped with textiles and tripwires that had 2D and zigzag geometries were connected to a custom force balance to understand the effects of these surface modifications on the drag. The primary objective of the present work is to explore the effects of drag reduction when fabrics with multiple number of seams and tripwires are attached on a cylinder at different angles from the stagnation point. Utilizing these flow control methods can provide potential time gains for a cyclist.
  • ItemOpen Access
    Settling Velocity of Straight and Curved Rods at Low Reynolds Numbers in a Quiescent Fluid
    (2023-08-04) Daramsing, Daniel Vedant; Hanson, Ronald; Gordon, Mark
    The present thesis is aimed towards understanding the effects of microfibre geometry on the settling velocity. Microfibres have been mathematically modelled as simple straight rods in the past to estimate their settling velocity; however, samples collected demonstrate complex geometries. One common geometric parameter of realistic microfibres is curvature, and the effect of this parameter on the settling velocity is the focus of the present thesis. A new drop tank and particle tracking system were designed to measure the settling velocity of curved rods at low Reynolds numbers typical of microfibres found in atmospheric samples. An experimental model was developed to relate the Reynolds number at terminal velocity and drag coefficient for both straight and curved rods. Non-ideal effects can significantly affect the estimation of travel of microfibres in comparison to other existing models, which emphasizes the importance of improved models that are tuned to predict the settling velocity of microfibres.
  • ItemOpen Access
    Design and Evaluation of an Active Yaw and Turbulence Generation System to Produce Unsteady Flow in Automotive Wind Tunnels
    (2023-08-04) Cacho, Germiel Angel; Hanson, Ronald
    This thesis summarizes the research, development, and testing of a novel unsteady yaw and turbulence generation system (TGS) for automotive wind tunnels that replicates on-road conditions using three combined subsystems. The focus of this thesis is primarily on one of the TGS subsystems, the unsteady yaw generation subsystem, which was made up of an airfoil-flap cascade. Tests were conducted in a 1/10th scale, 3/4 open-jet, wind tunnel and velocity data were obtained using two-component hotwire anemometry measurements that were spatially averaged. Yaw performance under different operating conditions, such as flap oscillation frequency and amplitude, was evaluated in terms of the phase-averaged flow behavior, the shape of the yaw angle distribution, and spectral distribution of velocity fluctuations. It is shown that the active yaw subsystem can generate bespoke yaw angle distributions. For example, the generated flows can mirror a variety of on-road flow conditions including the effect of traffic and vehicle wakes at highway speeds. The active system can also input a range of low frequency scales into the flow that are typical of those observed on-road. Preliminary tests indicate that the active yaw subsystem can operate in parallel with gust and turbulence subsystems to enhance flow spectrum designed to model on-road flows, however, future research is required to further optimize the TGS performance.
  • ItemOpen Access
    Active Turbulence Generation in a 3/4 Open-Jet Wind Tunnel
    (2023-08-04) Marques, Joshua Zachary; Hanson, Ronald
    The focus of this thesis is on the replication of on-road turbulent flow conditions within a 1/10th scale model of a 3/4 open-jet closed-loop return wind tunnel. This type of wind tunnel is commonly used in the automotive industry for testing aerodynamic performance of vehicles. Often, these types of wind tunnels are used to produce a clean laminar flow and testing results are limited to these idealized conditions. A novel system is designed to produce a wide range of turbulence scales in the scale model automotive wind tunnel using activated grid elements. It is shown that the turbulence produced by the novel turbulence generation system can generate turbulent flows having Taylor Reynolds numbers between 70 and 890, and turbulence intensities between 3.3 % and 33.1 %, depending on proximity to the grid.
  • ItemOpen Access
    Optical performance of solar power towers with conical secondary concentrators
    (2023-08-04) Ni, Perry; Cooper, Thomas
    Solar power towers are a type of concentrating solar power system that enable temperatures of over 1500° C, allowing high efficiency electrical conversion and the creation of solar fuels which can replace CO2 emitting resources such as oil. Efficient operation of solar towers is achieved through solar concentration in the form of heliostats and conical secondary concentrators. A multi-focus field is proposed allowing for a single tower to have three separate cavity receivers each with its own accompanying polar field of heliostats. Multi-focus fields proved to have comparable power and efficiency levels to single tower north facing fields and were more resilient to slope error. Conical secondary concentrators are a viable alternative to compound parabolic concentrators and have more variability in both concentration ratio as well as acceptance angle. A design map is presented to allow for cones to match either the optical efficiency or concentration ratio of CPCs.
  • ItemOpen Access
    Molecular Investigations on the Behaviours of Surface-Active Materials
    (2023-03-28) Jalali, Komeil; Jian, Cuiying
    This thesis applied molecular dynamics techniques, a powerful method based on factual observations at nanoscales, to effectively understand macroscopic and microscopic behaviors of surface-active materials in biphasic systems. First, few works have been focused on revealing the effect of naturally occurring organic materials such as naphthenic acids on the behaviors of polyaromatic compounds (known as asphaltenes that are interfacially active) during oil production. To bridge this gap, a series of MD simulations were performed to investigate the effects of molecular structures. It was revealed that naphthenic acids, depending on the solvent type, can either hinder or enhance nano-aggregation among asphaltene molecules. Furthermore, they can affect the orientations of polyaromatic molecules at the oil/water interface. The second direction of this thesis investigated biphasic systems in daily life, i.e., wastewater containing soap. The results obtained shed light on fundamental understandings and utilizations of surface-active materials during industrial applications and in our daily life.
  • ItemOpen Access
    Type Synthesis and Performance Optimization of Parallel Manipulators
    (2023-03-28) Zou, Qi; Zhang, Dan
    Parallel robots have been widely employed in industrial applications. There are still some challenging topics in the fundamental research, e.g., the primary problem mobility analysis has not been solved for about 150 years. A universal mobility equation for all kinds of parallel architectures has not been found. Another issue lies on the performance measurements for parallel manipulators. There are plenty of kinematic and dynamic performance indices. However, the various ranges and scales of these indicators make the optimal design considering multiple indices complicated. It is essential to search for a unified approach to normalize performance indicators. More dynamic performance measurement indicators should be raised to explore the dynamic features and complete the theory for parallel mechanisms. In this research, an improved mobility equation is designed to reveal the degrees of freedom for a special class of parallel robots. A novel methodology called the kinematic joint matrix is proposed. It possesses the mapping relations with parallel manipulators. A series of 2-6 degrees of freedom parallel architectures is denoted by the kinematic joint matrix. The theory of screw is employed to check the feasibility from several kinds of parallel structures. A special block diagram is introduced to distinguish various kinematic joint matrices. Since this family of parallel robots contains various motion characteristics, four parallel robots with distinct features are selected. Based on the kinematic models, three categories of singularities are explored. The operational and reachable workspaces of the pure-translational parallel robots are searched and the parametric analyses are reported. The linkage’s impacts for the reachable workspace of the mixed-motion parallel architectures are investigated. The novel performance level index is designed to unify the positive performance index and demonstrated the performance rank for any pose (position and orientation). The dexterity index is utilized as an example to verify the characteristics of the level index. The distributions and parametric analyses of two novel mass-related performances are studied. The dimension synthesis of a selected planar parallel robot is presented based on the non-dominated genetic algorithm II. The experiment results testify the correctness of the mobility and kinematic mathematical models of this mechanism.