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Articles 1 - 21 of 21
Full-Text Articles in Engineering
Advanced Thomson Scattering Diagnostics For Various Applications, Zichen He
Advanced Thomson Scattering Diagnostics For Various Applications, Zichen He
Doctoral Dissertations
Controlled nuclear fusion has been pursued as an ideal form of renewable energy for decades and the study of fusion plasma is fueling an increased demand for diagnostic capability. Furthermore, with the increasing applications of plasma in industry and medicine, it has become essential to characterize plasma dynamics and properties. Laser Thomson scattering diagnostics are considered to be the most reliable plasma diagnostic approaches for measuring electron temperature and electron density, the two most important parameters of a plasma. Four advanced Thomson scattering systems are discussed in this work to respectively address four different limitations or difficulties commonly encountered in …
Investigation Of Fore-Aft Element Connectors For An Ultra-Efficient Slotted, Natural-Laminar-Flow Aircraft Wing, Corey M. Arndt
Investigation Of Fore-Aft Element Connectors For An Ultra-Efficient Slotted, Natural-Laminar-Flow Aircraft Wing, Corey M. Arndt
Doctoral Dissertations
The SNLF [slotted, natural-laminar-flow airfoil] is a revolutionary technology projected to contribute significant decreases in fuel consumption and carbon emissions. The SNLF is designed to allow favorable pressure gradients to extend further aft increasing the extent of laminar flow achievable to about 90% of the entire airfoil, thus reducing the wing profile drag and subsequently fuel consumption. The SNLF is not without its complexity as it introduces several design challenges to maintain laminar flow. The slot width must be maintained during flight to engage the favorable pressure gradients that enable these benefits. As such a crucial aspect for implementing this …
Multiscale Investigation Of Freeze Cast Process And Ion Transport For Graphene Aerogel Electrodes, Yu-Kai Weng
Multiscale Investigation Of Freeze Cast Process And Ion Transport For Graphene Aerogel Electrodes, Yu-Kai Weng
Doctoral Dissertations
Effective use of renewable energy resources has been regarded as the most promising solution to climate emergency and energy crisis. However, the fluctuating and intermittent nature of renewable resources causes stability issues in the electric grid. High-capacity electrical energy storage is essential to stabilize the electric power supply using renewable resources. Among various types of energy storage systems, organic redox flow battery (ORFB) has attracted attentions due to their high stability, flexibility, low cost, and environmental compatibility, but the performance of the ORFB still needs a significant improvement due to their low energy or current density. Specifically, even though the …
Improving Strength And Stability In Continuum Robots, Jake A Childs
Improving Strength And Stability In Continuum Robots, Jake A Childs
Doctoral Dissertations
Continuum robots, which are bio-inspired ’trunk-like’ robots, are characterized for their inherent compliance and range of motion. One of the key challenges in continuum robotics research is developing robots with sufficient strength and stability without adding additional weight or complexity to the design. The research conducted in this dissertation encompasses design and modeling strategies that address these challenges in strength and stability. This work improves three continuum robot actuation paradigms: (1) tendon-driven continuum robots (TDCR), (2) concentric tube robots (CTR), and (3) concentric push-pull robots (CPPR). The first chapter of contribution covers strategies for improving strength in TDCRs. The payload …
Repeatability And Reproducibility Analyses For Structured Light Scanning, Leah Jacobs
Repeatability And Reproducibility Analyses For Structured Light Scanning, Leah Jacobs
Masters Theses
Structured light scanning is used to create a digital twin of a manufactured part. Features can be extracted from this digital twin to determine if the part meets the designer’s intent and required tolerances. This paper describes a repeatability and reproducibility study for a selected structured light scanning system and measurement artifact.
Optimized 3d-Printing Of Carbon Fiber-Reinforced Polyether-Ether-Ketone (Cfr-Peek) For Use In Overmolded Lattice Composite, Ryan C. Ogle
Optimized 3d-Printing Of Carbon Fiber-Reinforced Polyether-Ether-Ketone (Cfr-Peek) For Use In Overmolded Lattice Composite, Ryan C. Ogle
Masters Theses
Current orthopedic implants are overwhelmingly composed from metallic materials. These implants show superior mechanical properties, but this can additionally result in stress shielding due to a modulus mismatch between the bone tissue and implanted device. Polymeric implants reduce this stress shielding effect but have much lower mechanical properties, limiting their use. Polylactic acid (PLA) is a widely used biodegradable thermoplastic polymer, however, its use has been limited by the polymer’s mechanical properties and rapid loss of strength during degradation in vivo. Polyether-ether-ketone (PEEK) is another common biocompatible polymer , with chemical and mechanical properties which make it a popular alternative …
Path Planning For Additive Manufacturing Of Wire Arc Additive Manufacturing And Blue Light Fringe Projection Scanning, Tiffany Patricia Quigley
Path Planning For Additive Manufacturing Of Wire Arc Additive Manufacturing And Blue Light Fringe Projection Scanning, Tiffany Patricia Quigley
Masters Theses
Current methods of manufacturing large scale parts can take up to six months to generate the objective product. The objective of the wire arc additive manufacturing (WAAM) hybrid cell is to significantly reduce lead time associated with large scale parts. The WAAM process utilizes a 6 degree-of-freedom (DOF) robot manipulator in addition to a 2 DOF part positioner. 5 degrees of freedom are necessary for an effective WAAM process, leaving 3 DOF as redundant in this cell. This thesis serves to prove successful implementation of redundant kinematics on a WAAM robotic system. This is accomplished by maintaining a gravity aligned …
Image Based Processing For Weld Defect Detection, Shems-Eddine Belhout
Image Based Processing For Weld Defect Detection, Shems-Eddine Belhout
Masters Theses
There is a growing need for automation in the welding industry due to a growing shortage in skilled welders. TIG [Tungsten Inert Gas] welding, a method of welding that uses an electrode shielded by gas and is fed externally by a wire, is incredibly advantageous for its precise heat control. TIG welding is considered the standard for nuclear application which requires highly precise welds to be performed. Robotic welding can address this issue, and one major problem that occurs during welding is welding defects. Typical weld defect detection requires a highly knowledgeable welder or destructive and nondestructive evaluation. Destructive evaluation …
Aluminum-Based Material Fabrication By Friction Stir Processing: Microstructural Evolution And Mechanical Properties, Suhong Zhang
Aluminum-Based Material Fabrication By Friction Stir Processing: Microstructural Evolution And Mechanical Properties, Suhong Zhang
Doctoral Dissertations
Friction stir processing (FSP) is an energy efficient solid-state material processing technique for microstructure modification of commercial high-strength Al alloys. Many variant techniques were developed in recent years that enabled light-weight and high-strength structure fabrication. Identifying relationship among process conditions, microstructures, and mechanical properties is of critical importance to facilitate the practical implementation of these new techniques. The research in the dissertation focusses on developing two main techniques of the FSP: a) friction stir back extrusion (FSBE) of 6063 aluminum alloy for tube making and b) FSP of 7075 aluminum alloy from powder feedstock. FSBE fabricated Al 6063 alloy tubes …
Heat Pipes With Arbitrary Boundary Conditions, Katrina Sweetland
Heat Pipes With Arbitrary Boundary Conditions, Katrina Sweetland
Doctoral Dissertations
Heat pipes passively transfer heat in numerous applications. Traditionally one side of the heat pipe is coupled to a heat source (evaporator) while the opposite side is coupled to a heat sink (condenser). This configuration has working fluid stagnation points at each end of the heat pipe. Other configurations may also prove useful, such as heat pipes with multiple evaporators or multiple condensers. In such heat pipes, additional working fluid stagnation points form at locations dependent on the configuration of the thermal boundary conditions. These stagnation points divide the heat pipe into multiple cells that each have an evaporator and …
Upscaling And Development Of Linear Array Focused Laser Differential Interferometry For Simultaneous 1d Velocimetry And Spectral Profiling In High-Speed Flows, Kirk Davenport
Masters Theses
In this research a new configuration of linear array-focused laser differential interferometry (LA-FLDI) is described. This measurement expands on previous implementations of LA-FLDI through the use of an additional Wollaston prism. This additional prism expands the typical single LA-FLDI column into two columns of FLDI point pairs. The additional column of probed locations allows for increased spatial sampling of frequency spectra as well as the addition of simultaneous wall normal velocimetry measurements. The new configuration is used to measure the velocity profile and frequency content across a Mach 2 turbulent boundary layer at six wall normal locations simultaneously. Features of …
Modelling, Sensing, And Control Of Weld Beads In Gravity Aligned And Non-Gravity Aligned Orientations For Wire Arc Additive Manufacturing, Joshua J. Penney
Modelling, Sensing, And Control Of Weld Beads In Gravity Aligned And Non-Gravity Aligned Orientations For Wire Arc Additive Manufacturing, Joshua J. Penney
Doctoral Dissertations
Wire Arc Additive Manufacturing (WAAM) has recently developed into a viable manufacturing process for large, complex metal parts. The WAAM process uses a Gas Metal Arc Welding (GMAW) torch mounted to an automated motion platform to execute a predetermined path plan based on a desired CAD geometry. As the desired geometry becomes more complex, it is advantageous to utilize out-of-position welding techniques used by human welders to stabilize the weld pool during the deposition of large overhangs. To ensure part accuracy and quality, adding layers of real-time control to manage various aspects of the WAAM process is critical. First, a …
Model Based Force Estimation And Stiffness Control For Continuum Robots, Vincent A. Aloi
Model Based Force Estimation And Stiffness Control For Continuum Robots, Vincent A. Aloi
Doctoral Dissertations
Continuum Robots are bio-inspired structures that mimic the motion of snakes, elephant trunks, octopus tentacles, etc. With good design, these robots can be naturally compliant and miniaturizable, which makes Continuum Robots ideal for traversing narrow complex environments. Their flexible design, however, prevents us from using traditional methods for controlling and estimating loading on rigid link robots.
In the first thrust of this research, we provided a novel stiffness control law that alters the behavior of an end effector during contact. This controller is applicable to any continuum robot where a method for sensing or estimating tip forces and pose exists. …
Environmental Design And Optimization Of Modular Hydropower Plants, Colin Sasthav
Environmental Design And Optimization Of Modular Hydropower Plants, Colin Sasthav
Doctoral Dissertations
This research aimed to understand the pathways to cost-effective and sustainable low-head hydropower. Designing viable hydropower projects requires optimization across many economic, environmental, and social outcomes. However, existing run-of-river hydropower design models often focus on economic performance and customizing technologies for high-head diversion schemes. Standard modular hydropower is a new design approach that uses standardized rather than custom-designed technologies to achieve economies of scale. Oak Ridge National Laboratory established a conceptual outline for module classes based on functions, such as generation modules and fish passage modules, but further research was needed to identify how modules should be selected and operated …
Electrode Development Of Water Electrolyzer Cells For Low-Cost And High-Efficiency Hydrogen Production, Shule Yu
Doctoral Dissertations
A worldwide increase in energy demand and a latent crisis in the fossil fuel supply have spurred broad research in the renewable energy. Currently, most renewable energy resources (e.g., hydro, wind, solar, tide) face supply challenges as they are known to be intermittent, unstable, and locally shackled, which calls for urgent development in energy storage and conversion. Hydrogen is regarded as an ideal energy carrier with its advantages (e.g., high energy density, environmentally friendliness, and low weight). In practice, the proton exchange membrane electrolyzer cell (PEMEC) is considered to be one of the optimal hydrogen production and energy storage devices …
Trajectory Planning Of Non-Gravity Aligned (Nga) Segments In Arbitrary Directions For Large Scale Additive Manufacturing Of Metals (Lsamm), James Logan Mcneil
Trajectory Planning Of Non-Gravity Aligned (Nga) Segments In Arbitrary Directions For Large Scale Additive Manufacturing Of Metals (Lsamm), James Logan Mcneil
Doctoral Dissertations
Traditionally, slicing and path planning are done along the gravity-aligned direction of a part, causing more complex geometrical shapes to have unsupported overhangs. Wire Arc Additive Manufacturing (WAAM) has typically handled overhangs with a robotic part positioner; but, to extend the current capabilities of LSAMM, a new framework for slicing and building parts out of gravity alignment has been developed. The proposed framework focuses on segmenting more complex geometrical parts into gravity-aligned (GA), non-gravity aligned (NGA), and transition zones to support tool-path generation. GA and NGA segments can be planned with traditional slicing techniques, but the NGA tool-paths must be …
Sensor Comparison For Low-Cost Dynamic Force Measurement In Milling, Zachary Mason
Sensor Comparison For Low-Cost Dynamic Force Measurement In Milling, Zachary Mason
Masters Theses
Machine cutting forces are commonly measured using piezoelectric dynamometers. Such dynamometers can be prohibitively expensive and may still require extensive post processing. Previous work used a low-cost single degree of freedom constrained motion dynamometer (CMD) in conjunction with a knife edge sensor to determine the cutting forces through inverse force filtering. In that approach, the measured displacement of the CMD was transformed into the frequency domain by the fast Fourier transform (FFT) and convolved with the inverted receptance frequency response function (FRF) to yield force in the frequency domain. The force was then converted to the time domain using the …
Redundant Kinematics Solution For A Combined 6dof Robotic Manipulator And 2dof Part Positioner In A Waam Application, Ethan C. Vals
Redundant Kinematics Solution For A Combined 6dof Robotic Manipulator And 2dof Part Positioner In A Waam Application, Ethan C. Vals
Masters Theses
A typical wire arc additive manufacturing (WAAM) robot cell consists of a 6 DOF robot manipulator and a 2 DOF part positioner. Since the WAAM process requires a minimum of 5 DOFs, there are three redundant DOFs in the system that can be utilized to improve the robot manipulator positioning during part printing. In this thesis, the redundant kinematics of a manipulator and part positioner robot system are solved and then implemented on an actual robot system. The inverse kinematics of the manipulator and part positioner are solved as a kinematic chain using the pseudo-inverse Jacobian method. The two DOFs …
Eastman Guide Rail Project, Camryn J. Hurley, Jace Lyon, Isaiah Wallace, Cole Thomas, Erin Bennett
Eastman Guide Rail Project, Camryn J. Hurley, Jace Lyon, Isaiah Wallace, Cole Thomas, Erin Bennett
Chancellor’s Honors Program Projects
No abstract provided.
A Numerical Optimization Study Of A Novel Electrospray Emitter Design, Joshua H. Howell
A Numerical Optimization Study Of A Novel Electrospray Emitter Design, Joshua H. Howell
Masters Theses
The low thrust and high specific impulse of electric propulsion has been brought to the forefront for CubeSat and small spacecraft applications. Electrospray thrusters, which operate via electrostatic principles, have seen much research, development, and application in recent years. The small sizes of the spacecraft that utilize electrospray thrusters has focused development into the miniaturization of this technology to the micro-scale. Miniaturization introduces design challenges that must be addressed, including power supply mass and footprint requirements. This consequence requires investigation into the effects of design choices on the thruster onset voltage, defined as the voltage at which ion emission begins. …
Design, Fabrication, And Validation Of A Three-Zone Cell For Absorption Spectroscopy, Derek W. Burkhart
Design, Fabrication, And Validation Of A Three-Zone Cell For Absorption Spectroscopy, Derek W. Burkhart
Masters Theses
Spectroscopic databases such as HITRAN and HITEMP are required to characterize the spectral parameters of chemical species to ensure accurate calculations of gas concentrations and temperatures from laser absorption spectroscopy. These databases are populated by performing spectroscopic experiments at controlled conditions. Databases lack spectral parameters for combustion species such as CO, CO2, and H2O at temperatures combustion temperatures in the mid-IR wavelength range due to difficulties in creating an experimental absorption cell capable of surviving combustion temperatures. A high temperature absorption cell was previously used at the University of Tennessee Space Institute (UTSI) for high temperature spectroscopic experiments with combustion …