This thesis presents a comprehensive investigation into the feasibility and optimization of self-piercing riveting (SPR) for joining high-ductility die-cast aluminum alloy Nemalloy HE700 in F temper (as-cast) condition to dissimilar sheet materials, namely wrought aluminum alloy 6082-T6 and dual-phase steel DP600. The study demonstrates successful SPR joining of HE700 to these materials, with optimized process parameters and joint quality meeting automotive industry standards. Systematic experimental studies were conducted to investigate the effects of key SPR process parameters, including die geometry, ring groove depth, rivet hardness, and length, on joint quality and performance. Microstructural characterization revealed distinct patterns of grain flow and localized hardening in HE700 around the rivet and die features, providing insights into its deformation characteristics. Finite element simulations, incorporating advanced material models such as Johnson-Cook plasticity and failure for AA6082 and DP600, and Voce hardening with Gurson-Tvergaard-Needleman void damage model for HE700, were developed and extensively validated against experimental results. The simulations accurately predicted potential failure sites in HE700, aligning with experimental observations of crack initiation. Numerical parametric studies demonstrated the intricate effects of process parameters and material properties on the stress and strain distributions, material flow, and damage accumulation during SPR. The research contributes to the growing body of knowledge on advanced joining techniques for dissimilar materials, supporting vehicle lightweighting efforts. It establishes a comprehensive methodology integrating experiments, microstructural characterization, and simulations for studying and optimizing SPR processes for low ductility casting alloys, serving as a blueprint for future research and industrial implementation. The findings demonstrate the viability and potential of SPR technology for integrating high-ductility die-cast aluminum alloy HE700 into lightweight automotive body structures, paving the way for its wider industrial adoption. / Thesis / Master of Applied Science (MASc) / This research explores the potential of using a novel high-ductility aluminum alloy, Nemalloy HE700, in self-piercing riveting (SPR) - a modern joining technique for automotive manufacturing. The study aims to optimize the SPR process for joining HE700 to other commonly used automotive materials, such as aluminum alloys and high-strength steels, without compromising joint quality. By conducting practical experiments and computer simulations, the research identifies the best process parameters, such as rivet design and die shape, that result in strong, reliable joints meeting automotive industry standards. The findings demonstrate the successful use of HE700 in SPR, offering a promising solution for creating lighter, more fuel-efficient vehicles. This work contributes to the development of advanced joining technologies for sustainable transportation, making vehicles more environmentally friendly while maintaining high performance and safety standards.

Monitoring accurate temperature and pressure profiles in harsh environments is currently in high demand in aerospace gas turbine engines and nuclear reactor simulators. Having the ability to measure both quantities continuously over a region, without thermal coupling, using a sensor with a small size (envelope) is also highly desirable. Currently available MEMS (microelectromechanical systems) provide effective small scale pressure and temperature measurement devices, however, they have only been shown to be effective up to 600C and lack the ability to perform distributed measurements unless combined with fiber-optic techniques. In general, fiber-optics provide many advantages over electrical based sensors and are the ideal choice for high temperature regimes and distributed sensing. In this thesis, preliminary designs and suggested future work are presented for a sensor built within an 3.175 mm radius envelope and capable of distributed pressure and temperature sensing up to temperatures reaching 800C. Finite element analysis via ANSYS, along with analytical verification models have been used for the design evolution. Diaphragm based designs, seem to provide easy fabrication methods and good sensitivity, however, for this design to be realized at high temperature operation, a robust bonding method must be chosen to avoid unwanted deformation due to misfit strains. / Master of Science

Transparent laminates are widely used for body armor, goggles, windows and windshields. Improved understanding of their deformations under impact loading and of energy dissipation mechanisms is needed for minimizing their weight. This requires verified and robust computational algorithms and validated mathematical models of the problem. Here we have developed a mathematical model for analyzing the impact response of transparent laminates made of polymeric materials and implemented it in the finite element software LS-DYNA. Materials considered are polymethylmethacrylate (PMMA), polycarbonate (PC) and adhesives. The PMMA and the PC are modeled as elasto-thermo-visco-plastic and adhesives as viscoelastic. Their failure criteria are stated and simulated by the element deletion technique. Values of material parameters of the PMMA and the PC are taken from the literature, and those of adhesives determined from their test data. Constitutive equations are implemented as user-defined subroutines in LS-DYNA which are verified by comparing numerical and analytical solutions of several initial-boundary-value problems. Delamination at interfaces is simulated by using a bilinear traction separation law and the cohesive zone model. We present mathematical and computational models in chapter one and validate them by comparing their predictions with test findings for impacts of monolithic and laminated plates. The principal source of energy dissipation of impacted PMMA/adhesive/PC laminates is plastic deformations of the PC. In chapter two we analyze impact resistance of doubly curved monolithic PC panels and delineate the effect of curvature on the energy dissipated. It is found that the improved performance of curved panels is due to the decrease in the magnitude of stresses near the center of impact. In chapter three we propose constitutive relations for finite deformations of adhesives and find values of material parameters by considering test data for five portions of cyclic loading. Even though these values give different amounts of energy dissipated in the adhesive, their effect on the computed impact response of PMMA/adhesive/PC laminates is found to be minimal. In chapter four we conduct sensitivity analysis to identify critical parameters that significantly affect the energy dissipated. The genetic algorithm is used to optimally design a transparent laminate in chapter five. / Ph. D.

Deployable structures serve a large number of space missions. They are vital since spacecraft are launched by placing them inside launch vehicle payload fairings of limited volume. Traditional spacecraft design often involves large components. These components could have power, communication, or optics applications and include booms, masts, antennas, and solar arrays. Different stowing methods are used in order to reduce the overall size of a spacecraft. Some examples of stowing methods include simple articulating, more complex origami inspired folding, telescoping, and rolling or wrapping. Wrapping of a flexible component could reduce the weight by eliminating joints and other components needed to enable some of the other mechanisms. It also is one of the most effective methods at reducing the compaction volume of the stowed deployable. In this study, a generic unfurlable structure is optimized for maximum natural frequency at its fully deployed configuration and minimal strain energy in its stowed configuration. The optimized stowed structure is then deployed in simulation. The structure consists of a rectangular panel that tightly wraps around a central cylindrical hub for release in space. It is desired to minimize elastic energy in the fully wrapped panel and hinge to ensure minimum reaction load into the spacecraft as it deploys in space, since that elastic energy stored at the stowed position transforms into kinetic energy when the panel is released and induces a moment in the connected spacecraft. It is also desired to maximize the fundamental frequency of the released panel as a surrogate for the panel having sufficient stiffness. Deployment dynamic analysis of the finite element model was run to ensure satisfactory optimization formulation and results. / Master of Science / Spacecraft, or artificial satellites, do not fly from earth to space on their own. They are launched into their orbits by placing them inside launch vehicles, also known as carrier rockets. Some parts or components of spacecraft are large and cannot fit in their designated space inside launch vehicles without being stowed into smaller volumes first. Examples of large components on spacecraft include solar arrays, which provide power to the spacecraft, and antennas, which are used on satellite for communication purposes. Many methods have been developed to stow such large components. Many of these methods involve folding about joints or hinges, whether it is done in a simple manner or by more complex designs. Moreover, components that are flexible enough could be rolled or wrapped before they are placed in launch vehicles. This method reduces the mass which the launch vehicle needs to carry, since added mass of joints is eliminated. Low mass is always desirable in space applications. Furthermore, wrapping is very effective at minimizing the volume of a component. These structures store energy inside them as they are wrapped due to the stiffness of their materials. This behavior is identical to that observed in a deformed spring. When the structures are released in space, that energy is released, and thus, they deploy and try to return to their original form. This is due to inertia, where the stored strain energy turns into kinetic energy as the structure deploys. The physical analysis of these structures, which enables their design, is complex and requires computational solutions and numerical modeling. The best design for a given problem can be found through numerical optimization. Numerical optimization uses mathematical approximations and computer programming to give the values of design parameters that would result in the best design based on specified criterion and goals. In this thesis, numerical optimization was conducted for a simple unfurlable structure. The structure consists of a thin rectangular panel that wraps tightly around a central cylinder. The cylinder and panel are connected with a hinge that is a rotational spring with some stiffness. The optimization was solved to obtain the best values for the stiffness of the hinge, the thickness of the panel, which is allowed to vary along its length, and the stiffness or elasticity of the panel's material. The goals or objective of the optimization was to ensure that the deployed panel meets stiffness requirement specified for similar space components. Those requirements are set to make certain that the spacecraft can be controlled from earth even with its large component deployed. Additionally, the second goal of the optimization was to guarantee that the unfurling panel does not have very high energy stored while it's wrapped, so that it would not cause large motion the connected spacecraft in the zero gravity environments of space. A computer simulation was run with the resulting hinge stiffness and panel elasticity and thickness values with the cylinder and four panels connected to a structure representing a spacecraft. The simulation results and deployment animation were assessed to confirm that desired results were achieved.

Recently planar magnetic technologies have been widely used in power electronics, due to good cooling and ease of fabrication. High frequency operation of magnetic components is a key to achieve high power density and miniaturization. However, at high frequencies, skin and proximity effect losses in the planar windings become significant, and parasitics cannot be ignored. This piece of work deals with the modeling and design of planar integrated magnetic component for power electronics applications. First, one-dimensional eddy current analysis in some simple winding strategies is discussed. Two factors are defined in order to quantify the skin and proximity effect contributions as a function of frequency. For complicated structures, 2D and 3D finite element analysis (FEA) is adopted and the accuracy of the simulation results is evaluated against exact analytical solutions. Then, a planar litz structure is presented. Some definitions and guidelines are established, which form the basis to design a planar litz conductor. It can be constructed by dividing the wide planar conductor into multiple lengthwise strands and weaving these strands in much the same manner as one would use to construct a conventional round litz wire. Each strand is subjected to the magnetic field everywhere in the winding window, thereby equalizing the flux linkage. 3D FEA is utilized to investigate the impact of the parameters on the litz performance. The experimental results verify that the planar litz structure can reduce the AC resistance of the planar windings in a specific frequency range. After that, some important issues related to the planar boost inductor design are described, including core selection, winding configuration, losses estimation, and thermal modeling. Two complete design examples targeting at volume optimization and winding parasitic capacitance minimization are provided, respectively. This work demonstrates that planar litz conductors are very promising for high frequency planar magnetic components. The optimization of a planar inductor involves a tradeoff between volumetric efficiency and low value of winding capacitance. Throughout, 2D and 3D FEA was indispensable for thermal & electromagnetic modeling. / Master of Science

In American rail operations, rails fail due to the combined effects of rail wear due to repetitive wheel contact and the growth of surface and sub-surface cracks and flaws. Rail maintenance includes frequent uncoupled wear and ultrasonic inspections that determine the amount of wear that the rail has undergone and the presence of cracks and flaws. A rail is removed from service when its wear reaches a pre-determined wear limit or a flaw is detected in its cross section. In rail research, the life of a rail is typically estimated using fracture mechanic or fatigue methods and an assumed flaw geometry. Multiple models ranging from complex elastic-plastic finite element models to simplified representations of a beam on an elastic foundation have been developed to predict the life of a rail. The majority of rail failure models do not incorporate rail wear into their analysis, and assume an unworn rail geometry. In order to account for rail wear, certain models adopt simplified rail geometries that uncouple rail wear into top-wear and side-wear. This thesis presents a rail failure model that describes the combined effects of rail wear and crack growth through the development of a functional relationship between input variables describing the geometry, loading, and material properties of a given rail and output variables describing the life characteristics of the rail. This relationship takes the form of multiple response surfaces estimating the desired output variables. Finite element models incorporating worn rail profiles and an assumed crack geometry corresponding to a detail fracture are combined to determine the state of stress and strain at the assumed flaw. Strain-life fatigue methods and fracture mechanic concepts are used to develop the output variables necessary to describe the life of the rail using the finite element model results. The goals of this research are to predict the remaining fatigue life and estimate the crack-growth rate of the rail based on the minimum number of geometry, loading, and material property independent variables. The outputs developed to describe the rail's remaining life are intended to be used for the decision making for rail removal. / Master of Science

The Habitable Worlds Telescope Starshade is an occulting disk that orbits in tandem with a telescope that occludes and diffuses the light from stars to observe the relatively dim exoplanets in orbit around them. It achieves this in part with tailored petals that diffuse light to soften the light from the star. Due to the relative sizes of the star and the planet, NASA considers the shape stability of the Starshade's petals to be a Key Technology Gap. The Starshade is developed to be a deployable composite structure that folds on itself to fit within modern rockets. Due to the nature of satellite launches, Starshade will sit in the stowed configuration for multiple years, during which the viscoelastic material properties of the materials that consist of the Starshade will deform in the structure and take an unknown time to recover fully. Thus, the need arises to understand Starshade's viscoelastic behavior through recovery after fully deploying. Starshade's Petals consists of a sandwich composite structure where multiple composite edges are joined together using a significantly less stiff adhesive that is comparably thicker than the individual Carbon Fiber Reinforced Plastic layers that consist of the composite edge. This could cause traditional modeling approaches to not fully capture the potential modes of relaxation in the structure, so a diagnostic model, referred to as the Phoenix Edge, is developed to compare different modeling techniques. After modeling techniques are validated against each other, they are applied to the NI2 Petal to predict the viscoelastic structural response through 6 months of recovery after three years of stowage in a furled configuration.

No / The pharmaceutical powder and tableting process is simulated using a combined finite-discrete element method and contact dynamics for irregular-shaped particles. The particle-scale formulation and two-stage contact detection algorithm which has been developed for the proposed method enhances the overall calculation efficiency for particle interaction characteristics. The irregular particle shapes and random sizes are represented as a pseudo-particle assembly having a scaled up geometry but based on the variations of real powder particles. Our simulations show that particle size, shapes and material properties have a significant influence on the behaviour of compaction and deformation.

In recent years, triply periodic minimal surfaces (TPMS) have drawn much attention in research mainly due to their smooth, highly symmetrical surfaces, non-self-intersecting features, and mathematically controllable topologies. TPMS can have pre-defined physical and mechanical properties. The advancement of additive manufacturing technology enables us to fabricate these intricate geometric structures which was not possible by traditional manufacturing methods. In this study, the vat photopolymerization technique was used to manufacture Primitive, Gyroid, and Diamond structures. Samples were cured under ultraviolet (UV) rays after printing. Uniaxial compression experiments were conducted to assess the compressive modulus and strength of these lightweight structures. The compressive behavior of TPMS structures was also predicted using finite element analysis (FEA). Dynamic mechanical analysis (DMA) was used to compare the behavior of these structures at different temperatures. UV-cured samples exhibited improved thermo-mechanical characteristics. The primitive structure had the highest compressive strength among other structures. FEA also revealed the stress concentration areas for each sandwich structure. The DMA findings indicate that TPMS sandwich structures demonstrate significantly reduced storage modulus compared to solid structures. A numerical investigation was performed to understand the heat exchanger application of TPMS structures. The velocity profile, temperature, and pressure distributions were observed for the Primitive heat exchanger. The results of this investigation provide valuable information regarding the enhanced structural and thermal characteristics of these structures manufactured using vat photopolymerization.

Direct drive Permanent Magnet Linear Generators (PMLGs) are used in energy converters for energy harvesting from marine waves. Greater reliability and simplicity can be achieved for Wave Energy Converters (WECs), by using direct drive machines linked to the power take-off device, in comparison with WECs using rotational generators combined with hydraulic or mechanical interfaces to convert linear to rotational torque. However, owing to the relatively low velocities of marine waves and the desire for significant energy harvesting by each individual unit, direct drive PMLGs share large permanent magnet volumes and hence, high magnetic forces. Such forces can generate vibrations and reduce the lifetime of the bearings significantly, which is leading to an increase in maintenance costs of WECs. Additionally, a power electronics converter is required to integrate the generator‘s electrical output to meet the requirements for connection to the national grid. This thesis is concerned mainly with the fundamental investigation into the use PMLGs for direct drive WECs. Attention is focused on developing several new designs based on tubular long stator windings topologies and optimisation for flat PMLGs. The designs are simulated as air- and iron-cored machines by means of Finite Element Analysis (FEA). Furthermore, a new power electronics control system is proposed to convert the electrical output of the long stator generators. Various wave energy-harvesting technologies have been reviewed and it has been found that permanent magnet linear machines demonstrate great potential for integration in WECs. The main reason is the strong exaltation flux provided by the high number of permanent magnets. Such flux, combined with design simplicity, can deliver high induced voltage as well as structural integrity. In the thesis, a flat single and double structured iron-cored PMLG is studied and optimised. Several magnetic force mitigation techniques are investigated and an optimisation is conducted. The optimisation is concerned mainly with increasing electrical output power and reducing the magnetic forces in the generators. As a result, an optimal design introducing the idea of separated magnetic cores has been proposed. The FEA simulations reveal that magnetic separation in the yoke can increase significantly the energy-harvesting capability of PMLGs. Furthermore, the concept of the design of long stator windings for tubular PMLGs is studied. Two long stator generators having different magnetisation topologies and similar sizes to existing machine are modelled and compared to the existing machine. The similar-sized existing and proposed PMLGs are simulated by FEA. In this way, settings such as different boundary conditions, symmetry boundaries and material properties are used to gain confidence in the simulated results of the proposed machines. Moreover, the simulated results for the existing PMLG are verified against previously performed numerical simulations and practical tests delivered and published as part of other research. The outcome for the proposed PMLGs reveals several advantages for the long stator design, such as lower cogging forces and higher energy harvesting and a lower price of the raw structural materials. Additionally, the thesis proposes and simulates a new design for an air-cored PMLG. To boost the output power, the proposed design is based on a long stator topology adopting two sets of permanent magnet rings sandwiching copper windings in a tubular structure. The design is compared with a current machine in FEA and the results show significant reduction in radial forces and an increase in energy harvesting. Finally, a novel power electronics control system, bypassing inactive coils is suggested and simulated as part of the grid integration system for the long stator PMLGs. The new system achieves a reduction in the thermal losses in the power electronics switches in comparison with existing systems. The power electronics system and the generator have been simulated in Matlab coupled externally with FEA (JMAG Designer).