<p>The graphite structure in compacted graphite iron (CGI) is more coral-like and interconnected only within each eutectic cell. The irregular surface of the graphite-matrix interface has blunt edges which results in the intimate adhesion of the graphite particles to the metal matrix producing more resistance to crack initiation and more vermicular paths arrest crack propagation. Furthermore, the coral-like graphite particles, which are characterized with round edges, also do not promote crack propagation and serve as crack arrestors once cracks are initiated. This unique morphology of graphite in CGI, thereafter, pays off in a higher tensile strength and modulus of elasticity while possessing reasonable thermal conductivity.</p> <p>This work is divided into two phases. The first phase establishes a foundation of a microstructure modeling technique which will be then applied to model CGI in machining. Modeling is being done to shift the approach away from trial and error as is currently being done to a more physics based approach. As machining is conceptually a controlled fracture process, this stage comprehensively studies and models the initiation and propagation of fracture in compacted graphite iron.</p> <p>The second phase serves as an application of the previously built model to capture the more complex scenario involving machining of CGI at different cutting speeds and feeds. The finite element modeling of CGI in machining provides an as of yet unavailable procedure on which future optimization techniques can be performed. The study of chip formation, cutting insert wear, and force measurements are performed in parallel with the modeling process and are employed as means to validate the FE model. Validation of both work phases has been completed to support the model developed in this thesis that captures the critical aspects of machining CGI under different operating scenarios.</p> / Doctor of Philosophy (PhD)

<p>North American suburbs are facing decline and obsolescence. They cannot meet the needs of North America’s ageing society, future climate change, or higher energy prices. Compounded with their negative environmental impact, non-resilient is an appropriate label for North American suburbs.</p> <p>Resilient suburban communities can be realized through retrofitting to meet current and future needs. Community scale retrofitting is in the early stages of development. House-level retrofitting tools exist but must be synthesized into a useable form for homeowners.</p> <p>Homeowners arguably have the largest stake in the future of the suburbs for both financial and social reasons. Empowering them with tools to make their suburban home and community more resilient is considered to be desirable.</p> <p>This thesis empowers homeowners by developing a prototype decision support system (DSS) that will help them (or their contractors) make choices about adapting and retrofitting their home for resilience. This Microsoft Excel-based DSS addresses the following suburban needs: new housing types, reducing the environmental impacts of the home, and decreasing reliance on fossil fuels. The DSS does this through three constituent ‘modules’.</p> <p>The first module, <em>Dividing Suburban Homes</em>, demonstrates the feasibility of dividing large suburban homes into multifamily dwellings. The second module, <em>Sustainable Additions</em>, selects resilient building materials for housing additions. The last module, <em>Reducing the Home’s Environmental Impact</em>, helps homeowners choose methods for reducing the environmental impact and fossil fuel usage of their home.</p> <p>Through these three modules, this DSS addresses a considerable number of the current and anticipated issues facing the suburbs.</p> / Master of Applied Science (MASc)

<p>This research is concerned with CFD modelling of thermal energy storage tanks containing water with submerged phase change materials (PCM). Under appropriate operating conditions, the energy density of this hybrid system can be significantly increased (two to five times) relative to a system containing water only. However, due to low thermal conductivity of phase change materials, the geometry and configurations of the PCM capsules in the tank should be optimized. This research focused on the assessment of flat plate PCM modules submerged in a rectangular water tank. The encapsulation of the PCM within the slender flat plates resulted in a large PCM surface area and a reduction in the internal heat transfer resistance. The water was heated by coils placed at the bottom of the tank. The resulting natural convection currents acted to transfer heat from the hot coils to the PCM modules which were treated as isothermal at the PCM melt temperature. It is concluded that the charge rate of the system increases to 2.8 times by increasing the PCM volume percentage from 2.5% to 15%. However for PCM volume percentages of more than 15%, the area of the PCM became much more than the area of the coil (around 15 times) in a way that the charge rate of the system started to be controlled by the coil. In this stage, the charge rate of the system remained constant, and adding modules to the system only increased the heat capacity of the system. Therefore the charge rate of the system could only increase if the coil surface area was increased. The heat transfer coefficients of the PCM modules and coil tubes were higher than those evaluated by the experimental correlations for natural convection. This was due to the recirculation of the flow in the tank “pumping effect” created by the coil for PCM modules and by the PCM modules for the coil. It was also concluded that superheating of the PCM surface temperature decreases the heat transfer rate to the PCM significantly, and the charge rate of the system varies linearly with the temperature difference between the PCM modules and the coil.</p> / Master of Applied Science (MASc)

Total ankle replacement (TAR) implants are an effective option to restore the range of motion of the ankle joint for arthritic patients. An effective tool for analyzing these implants’ mechanical performance and longevity in-silico is finite element analysis (FEA). ABAQUS FEA was used to statically analyze the von Mises stress and contact pressure on the articulating surface of the bearing component in two newly installed fixed-bearing total ankle replacement implants (the Wright Medical INBONE II and the Exactech Vantage). This bearing component rotates on the talar component to induce primary ankle joint motion of plantarflexion and dorsiflexion. The stress response was analyzed on this bearing component since it is made of the least strong material in the implant assembly (ultra-high molecular weight polyethylene (UHMWPE). This bearing component commonly fails and is the cause for surgeon revisions. Six different FEA models for various gait percentages during stance (10%, 20%, 30%, 40%, 50%, and 60%) were created. They varied in magnitude of the compressive load and the ankle dorsiflexion/plantarflexion angle. This study captured the variation in stress magnitudes based on the portion of the stance phase. The results indicated that the stress distribution on the articulating surface increased as compressive load increased, and the largest magnitudes occurred at high dorsiflexion angles (15-30°). The von Mises stress and contact pressure tended to occur in regions where the thickness of the bearing was the least. Additionally, high contact pressures were examined in areas near the talar component's edge or at the bearing's edges. To the author’s knowledge, this is the first study available to the research community that analyzes the Vantage implant with FEA. This study lays an essential foundation for future researchers in presenting a thorough literature review of TAR and for a simple model setup to capture the stress distributions of two TAR implants. This study provides valuable information that can be beneficial to medical company designers and orthopedic surgeons in understanding the stress response of TAR patients.

An anguilliform swimming robot replicating an idealized motion is a complex marine vehicle necessitating both a theoretical and experimental analysis to completely understand its propulsion characteristics. The ideal anguilliform motion within is theorized to produce ``wakeless'' swimming (Vorus, 2011), a reactive swimming technique that produces thrust by accelerations of the added mass in the vicinity of the body. The net circulation for the unsteady motion is theorized to be eliminated. The robot was designed to replicate the desired, theoretical motion by applying control theory methods. Independent joint control was used due to hardware limitations. The fluid velocity vectors in the propulsive wake downstream of the tethered, swimming robot were measured using Particle Image Velocimetry (PIV). Simultaneously, a load cell measured the thrust (or drag) forces of the robot via a hydrodynamic tether. The measured field velocities and thrust forces were compared to the theoretical predictions for each. The desired, ideal motion was not replicated consistently during PIV testing, producing off-design scenarios. The thrust-computing method for the ideal motion was applied to the actual, recorded motion and compared to the load cell results. The theoretical field velocities were computed differently by accounting for shed vortices due to a different shape than ideal. The theoretical thrust shows trends similar to the measured thrust over time. Similarly promising comparisons are found between the theoretical and measured flow-field velocities with respect to qualitative trends and velocity magnitudes. The initial thrust coefficient prediction was deemed insufficient, and a new one was determined from an iterative process. The off-design cases shed flow structures into the downstream wake of the robot. The first is a residual disturbance of the shed boundary layer, which is to be expected for the ideal case, and dissipates within one motion cycle. The second are larger-order vortices that are being shed at two distinct times during a half-cycle. These qualitative and quantitative comparisons were used to confirm the possibility of the original hypothesis of ``wakeless'' swimming. While the ideal motion could not be tested consistently, the results of the off-design cases agree significantly with the adjusted theoretical computations. This shows that the boundary conditions derived from slender-body constraints and the assumptions of ideal flow theory are sufficient enough to predict the propulsion characteristics of an anguilliform robot undergoing this specific motion.

The focus of this thesis is to explore the automation technology used in the modern entertainment industry. Upon completion of my thesis, I will deliver a working prototype of the chosen technology and present its capabilities in a choreographed show.

This thesis presents a real-time autonomous guidance and control method for a quadrotor in a GPS-denied environment. The quadrotor autonomously seeks a destination while it avoids obstacles whose shape and position are initially unknown. We implement the obstacle avoidance and destination seeking methods using off-the-shelf sensors, including a vision-sensing camera. The vision-sensing camera detects the positions of points on the surface of obstacles. We use this obstacle position data and a potential-field method to generate velocity commands. We present a backstepping controller that uses the velocity commands to generate the quadrotor's control inputs. In indoor experiments, we demonstrate that the guidance and control methods provide the quadrotor with sufficient autonomy to fly point to point, while avoiding obstacles.

This thesis introduces a new methodology for robust form parameter design of complex hull form geometry via constraint programming, automatic differentiation, interval arithmetic, and truncated hierarchical B- splines. To date, there has been no clearly stated methodology for assuring consistency of general (equality and inequality) constraints across an entire geometric form parameter ship hull design space. In contrast, the method to be given here can be used to produce guaranteed narrowing of the design space, such that infeasible portions are eliminated. Furthermore, we can guarantee that any set of form parameters generated by our method will be self consistent. It is for this reason that we use the title feasible form parameter design. In form parameter design, a design space is represented by a tuple of design parameters which are extended in each design space dimension. In this representation, a single feasible design is a consistent set of real valued parameters, one for every component of the design space tuple. Using the methodology to be given here, we pick out designs which consist of consistent parameters, narrowed to any desired precision up to that of the machine, even for equality constraints. Furthermore, the method is developed to enable the generation of complex hull forms using an extension of the basic rules idea to allow for automated generation of rules networks, plus the use of the truncated hierarchical B-splines, a wavelet-adaptive extension of standard B-splines and hierarchical B-splines. The adaptive resolution methods are employed in order to allow an automated program the freedom to generate complex B-spline representations of the geometry in a robust manner across multiple levels of detail. Thus two complementary objectives are pursued: ensuring feasible starting sets of form parameters, and enabling the generation of complex hull form geometry.

Abstract An experimental method was developed that demonstrated the size effects in forming thin sheet metals, and a finite element model was developed to predict the effects demonstrated by the experiment. A universal testing machine (UTM) was used to form aluminum and copper of varying thicknesses (less than 1mm) into a hemispherical dome. A stereolithography additive manufacturing technology was used to fabricate the punch and die from a UV curing resin. There was agreement between the experimental and numerical models. The results showed that geometric size effects were significant for both materials, and these effects increased as the thickness of the sheets decreased. The demonstration presents an inexpensive method of testing small-scale size effects in forming processes, which can be altered easily to produce different shapes and clearances.

The transportation of oil and gas and their products through the pipelines is a safe and economically efficient way, when compared with other methods of transportation, such as tankers, railroad, trucks, etc. Although pipelines are usually well-designed, during construction and later in service, pipelines are subjected to a variety of risks. Eventually, some sections may experience corrosion which can affect the integrity of pipeline, which poses a risk in high-pressure operations. Specifically, in pipelines with long history of operation, the size and location of the corrosion defects need to be determined so that pressure levels can be kept at safe levels, or alternatively, a decision to repair or replace the pipe section can be made. To make this decision, there are several assessment techniques available to engineers, such as ASME B31G, MB31G, DNV-RP, software code called RSTRENG. These assessment techniques help engineers predict the remaining strength of the wall in a pipe section with a corrosion defect. The corrosion assessment codes in the United States, Canada and Europe are based on ASME-B31G criterion for the evaluation of corrosion defects, established based on full-scale burst experiments on pipes containing longitudinal machined grooves, initially conducted in 1960s. Because actual corrosion defects have more complex geometries than machined grooves, an in-depth study to validate the effectiveness of these techniques is necessary. This study is motivated by this need. The current study was conducted in several stages, starting with the deformation behavior of pipe steels. In Phase 1, true-stress-true plastic strain data from the literature for X42 and X60 steel specimens were used to evaluate how well four commonly used constitutive equations, namely, those developed by Hollomon, Swift, Ludwik and Voce, fit the experimental data. Results showed that all equations provided acceptable fits. For simplicity, the Hollomon equation was selected to be used in the rest of the study. In Phase 2, a preliminary finite element modeling (FEM) study was conducted to compare two failure criteria, stress-based or strain-based, performed better. By using data from the literature for X42 and X60 pipe steels, experimental burst pressure data were compared with predicted burst pressure data, estimated based on the two failure criteria. Based on this preliminary analysis, the stress-based criterion was chosen for further FEM studies. In Phase 3, failure data from real corrosion pits in X52 pipe steels with detailed profiles were used to develop a FEM scheme, which included a simplified representation of the defect. Comparison of actual and predicted burst pressures indicated a good fit, with a coefficient of determination (R2) level of 0.959. In Phase 4, burst pressure levels were estimated for real corrosion pits for the experiments from the same study as in Phase 3, but only with corrosion pit depths and length and without corrosion widths. Widths were estimated from the data used in Phase 3, by using an empirical equation as a function of pit length. There was significant error between experimental and predicted burst pressure. Errors in Phases 3 and 4 were compared statistically. Results showed that there is a statistically significant difference in the error when the width of the corrosion pit is unknown. This finding is significant because none of the assessment techniques in the literature takes width into consideration. Subsequently, a parametric study was performed on three defect geometries from the same study in Phase 3. The pit depths and lengths were held constant but widths were changed systematically. In all cases, the effect of the pit width on burst pressure was confirmed. In Phase 5, the three assessment techniques, ASME B31G, MB31-G and DNV-RP were evaluated by using experimental test results for X52 pipe. Synthetic data for deeper pits were developed by FEM and used along with experimental data in this phase. Two types of the error were distinguished to classify defects. Type I errors (α) and Type II errors (β) were defined using Level 0 evaluation method. Results showed that although ASME B31G is the most conservative technique, it is more reliable for short defects than MB31G and DNV-RP. The least conservative technique was DNV-RP but it yielded β error, i.e., the method predicted a safe operating pressure and pipe section would fail. Therefore, DNV-RP is not recommended for assessment of steel pipes, specifically for X52 pipes.