Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Cold spray (3)
- Electrodeposition (2)
- Electrolytic (2)
- Plating powders (2)
- 2D materials (1)
-
- 3D airfoil (1)
- AEDC (1)
- Abaqus (1)
- Above Sheathing Ventilation (1)
- Academic theses (1)
- Additive Manufacturing (1)
- Airfoils (1)
- Analog Derivative (1)
- Analog Filter (1)
- Analog Sensor (1)
- Aspect ratio (1)
- Attic Condensation (1)
- Attic Ventilation (1)
- Buckling wavelength (1)
- Bulk-metallic glasses (1)
- Cable (1)
- Cascading (1)
- Computational nanomaterials (1)
- Control System (1)
- Copper (1)
- Coupled mode (1)
- Cyclotron (1)
- Defect Prediction (1)
- Defect engineering (1)
- Deflection (1)
Articles 1 - 30 of 34
Full-Text Articles in Engineering
Thermal Conductivity And Mechanical Properties Of Interlayer-Bonded Graphene Bilayers, Afnan Mostafa
Thermal Conductivity And Mechanical Properties Of Interlayer-Bonded Graphene Bilayers, Afnan Mostafa
Masters Theses
Graphene, an allotrope of carbon, has demonstrated exceptional mechanical, thermal, electronic, and optical properties. Complementary to such innate properties, structural modification through chemical functionalization or defect engineering can significantly enhance the properties and functionality of graphene and its derivatives. Hence, understanding structure-property relationships in graphene-based metamaterials has garnered much attention in recent years. In this thesis, we present molecular dynamics studies aimed at elucidating structure-property relationships that govern the thermomechanical response of interlayer-bonded graphene bilayers.
First, we present a systematic and thorough analysis of thermal transport in interlayer-bonded twisted bilayer graphene (IB-TBG). We find that the introduction of interlayer C-C …
In Situ Process Monitoring And Machine Learning Based Modeling Of Defects And Anomalies In Wire-Arc Additive Manufacturing, Eduardo Miramontes
In Situ Process Monitoring And Machine Learning Based Modeling Of Defects And Anomalies In Wire-Arc Additive Manufacturing, Eduardo Miramontes
Masters Theses
Wire Arc Additive Manufacturing (WAAM) has made great strides in recent years however, there remain numerous persistent challenges still hindering more widespread adoption. Defects in the parts produced degrade their mechanical performance. Inconsistency in the geometry of the weld beads or undesirable anomalies such as waviness, or humps can lead to loss of geometric accuracy and in extreme cases, when anomalies propagate to subsequent layers, build failure. Such defects can be mitigated by a controls framework, which would require a model that maps undesirable outcomes to information about the process that can be obtained in real time. This thesis explores …
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 …
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. …
Effects Of Pillar And Sealing Design On Thermal And Mechanical Performance Of Vacuum Insulated Glazing, Wenyuan Zhu
Effects Of Pillar And Sealing Design On Thermal And Mechanical Performance Of Vacuum Insulated Glazing, Wenyuan Zhu
Masters Theses
Vacuum insulated glazing with a low-emittance coating has a great market potential as an effective transparent insulator. The thermal insulating performance of VIG is determined by its design, including material selection and configuration of different components. Thermal conductance of the vacuum gap, as a transport bottleneck, is one of the primary factors controlling the thermal transport across VIG. In particular, since support pillars and sealings provide the main thermal transport channels across the vacuum gap, increasing the pillar and sealing thermal resistance is a key strategy for effective thermal insulation, while maintaining the vacuum space and mechanical strength of VIG. …
Design And Simulation Of A Supervisory Control System For Hybrid Manufacturing, Michael Buckley
Design And Simulation Of A Supervisory Control System For Hybrid Manufacturing, Michael Buckley
Masters Theses
The research teams of Dr. Bill Hamel, Dr. Bradley Jared and Dr. Tony Schmitz were tasked by the Office of Naval Research to create a hybrid manufacturing process for a reduced scale model of a naval ship propeller. The base structure of the propeller is created using Wire Arc Additive Manufacturing (WAAM), which is then scanned to compare created geometry to desired geometry. The propeller is then machined down to match the desired geometry. This process is iterated upon until the final product meets design tolerances. Due to the complex nature and numerous industrial machines used in the process, it …
Fabrication Of Binder-Free Electrodes Based On Graphene Oxide With Cnt For Decrease Of Resistance, Di Zhang
Fabrication Of Binder-Free Electrodes Based On Graphene Oxide With Cnt For Decrease Of Resistance, Di Zhang
Masters Theses
In electrode double layer capacitor (EDLC), electrodes usually contain binder materials to provide adhesion between electrode materials. However, binder materials usually bring unwanted resistances to the component due to their non-conductivity properties and the occupation of ion cavities. The purpose of this thesis is to demonstrate the feasibility of fabricating electrodes for EDLCs by using carbon nanotubes (CNTs) and graphene oxide (GO) without using any binding materials. At the same time, investigating the binder-free electrode’s electrochemical properties and make an assumption of its potential application in the future.
The slurry of binder-free electrodes was fabricated by ultrasonicating water suspended CNTs …
Investigating Localized Performance And Mass Transport Phenomena In Polymer Electrolyte Water Electrolyzers, Frida Helena Roenning
Investigating Localized Performance And Mass Transport Phenomena In Polymer Electrolyte Water Electrolyzers, Frida Helena Roenning
Masters Theses
In the face of increasing demand for renewable energy sources to replace fossil fuels, current technologies face the issue of steady energy supply from source to power distribution. As most current renewable energy methods either rely on intermittent natural sources or are geographically bound, they require an energy storage medium. Polymer Electrolyte Water Electrolyzers are a theoretically ideal solution to this demand, but they require some performance improvements in practice to be economically viable. This study analyses the current distribution in such electrolyzers in the aim of gaining insight to improve their performance. The current distribution diagnostic can capture local …
Topology Network Optimization Of Facility Planning And Design Problems, Ravi Ratan Raj Monga
Topology Network Optimization Of Facility Planning And Design Problems, Ravi Ratan Raj Monga
Masters Theses
The research attempts to provide a graphical theory-based approach to solve the facility layout problem. Which has generally been approached using Quadratic Assignment Problem (QAP) in the past, an algebraic method. It is a very complex problem and is part of the NP-Hard optimization class, because of the nonlinear quadratic objective function and (0,1) binary variables. The research is divided into three phases which together provide an optimal facility layout, block plan solution consisting of MHS (material handling solution) projected onto the block plan. In phase one, we solve for the position of departments in a facility based on flow …
Electroplating Of Copper On Tungsten Powder, Richard Berdos
Electroplating Of Copper On Tungsten Powder, Richard Berdos
Masters Theses
Strengthening, resistant and shielding properties, to name a few, can be achieved by implementing a surface material coating onto an engineering component. Various elements of these compounded parts can augment the functionality of the part, such as, increased life time and more interactive surfaces. Tungsten has proven to be a challenge to plate with other metals, but if done correctly, the results can allow for the cold spray of tungsten. Cold spraying tungsten particles alone provides a challenge because the powder is too hard and instead of adhering, it erodes the surface it is attempting to plate. Coating tungsten in …
A Numerical Flutter Predictor For 3d Airfoils Using The Onera Dynamic Stall Model, Pieter Boersma
A Numerical Flutter Predictor For 3d Airfoils Using The Onera Dynamic Stall Model, Pieter Boersma
Masters Theses
To be able to harness more power from the wind, wind turbine blades are getting longer. As they get longer, they get more flexible. This creates issues that have until recently not been of concern. Long flexible wind turbine blades can lose their stability to flow induced instabilities such as coupled-mode flutter. This type of flutter occurs when increasing wind speed causes a coupling of a bending and a torsional mode, which create limit cycle oscillations that can lead to blade failure. To be able to make the design of larger blades possible, it is important to be able to …
Streamwise Flow-Induced Oscillations Of Bluff Bodies - The Influence Of Symmetry Breaking, Tyler Gurian
Streamwise Flow-Induced Oscillations Of Bluff Bodies - The Influence Of Symmetry Breaking, Tyler Gurian
Masters Theses
The influence of symmetry breaking on the flow induced oscillations of bluff bodies in the steamwise direction is studied. First, a series of experiments is conducted on a one-degree-of-freedom circular cylinder allowed to exhibit pure translational motion in the streamwise direction over a range of reduced velocities, 1.4 < U* < 4.4, corresponding to a Reynolds number range of 970 < Re < 3370. Two distinct regions of displacements were observed in reduced velocity ranges of 1.6 < U* < 2.5 and 2.75 < U* < 3.85. Measured force coefficients in the drag and lift direction were examined, along with the wake visualization, through the range of reduced velocities, to infer the resulting wake modes. A new Alternating Symmetric (AS) mode was found. This transition from symmetric to AS shedding occurred near the end of the first region of response. Similar tests were run with a square prism in the parameter space of 2.4 < U* < 5.8 and 757 < Re < 1900 over angles of incidence of 0° ≤ α ≤ 45°. A distinct region of lock-in is observed for α = 0°, 2.5°, 5°, 7.5° over 3.2 < U* < 5.4 for α = 0°, and decreasing with increasing α. The wake structures were found to be roughly symmetric for α = 0°, but transitioned towards asymmetry …
Non-Equispaced Fast Fourier Transforms In Turbulence Simulation, Aditya M. Kulkarni
Non-Equispaced Fast Fourier Transforms In Turbulence Simulation, Aditya M. Kulkarni
Masters Theses
Fourier pseudo-spectral method on equispaced grid is one of the approaches in turbulence simulation, to compute derivative of discrete data, using fast Fourier Transform (FFT) and gives low dispersion and dissipation errors. In many turbulent flows the dynamically important scales of motion are concentrated in certain regions which requires a coarser grid for higher accuracy. A coarser grid in other regions minimizes the memory requirement. This requires the use of Non-equispaced Fast Fourier Transform (NFFT) to compute the Fourier transform, by solving a system of linear equations.
To achieve similar accuracy, the NFFT needs to return more Fourier coefficients than …
Electroless Deposition & Electroplating Of Nickel On Chromium-Nickel Carbide Powder, Jeffrey Rigali
Electroless Deposition & Electroplating Of Nickel On Chromium-Nickel Carbide Powder, Jeffrey Rigali
Masters Theses
Engineered components can gain desirable properties when coated with surface materials. Wear-resistant coatings can improve the performance of contacting surfaces and allow for an extended life of the parts. Hard chromium has been the plating material of choice for certain wear and corrosion- resistant coatings because of its desirable combination of chemical resistance, adhesion, and mechanical properties. However, hexavalent chromium, a component of the process for applying hard chromium coatings, has been recognized by the EPA as having hazardous health and environmental impacts. Existing and planned environmental regulations restricts the use of process chemicals containing hexavalent chromium ions. This substantiates …
Improving The Efficiency Of Wind Farm Turbines Using External Airfoils, Shujaut Bader
Improving The Efficiency Of Wind Farm Turbines Using External Airfoils, Shujaut Bader
Masters Theses
Wind turbine efficiency typically focuses on the shape, orientation, or stiffness of the turbine blades. In this thesis, the focus is instead on using static fixed airfoils in proximity to the wind turbine to control the airflow coming out of the turbine. These control devices have three beneficial effects. (1) They gather air from “higher up” where the air is moving faster on average (and therefore has more kinetic energy in it). (2) They throw the used (and slowed down air) downwards. This means that any turbines in the wind farm behind the lead turbines do not get “stale” air. …
Incorporating Seasonal Wind Resource And Electricity Price Data Into Wind Farm Micrositing, Timothy A. Pfeiffer
Incorporating Seasonal Wind Resource And Electricity Price Data Into Wind Farm Micrositing, Timothy A. Pfeiffer
Masters Theses
Currently, most micrositing techniques aim to maximize annual energy production (AEP) or minimize cost of energy (COE) with no direct regard to revenue. This research study developed a method that utilizes the seasonal electricity price and wind data to microsite wind farms in terms of profitability. To accomplish this, six candidate wind farms with differing layouts and spacing were selected at a given location. They were then simulated using a wake modeling software to produce expected power outputs at different wind speeds, wind directions, and turbulence intensities. By interpolating the power output tables with wind data, a power time-series was …
Tracking Of Human Joints Using Twist And Exponential Map, Xiaodong Yang
Tracking Of Human Joints Using Twist And Exponential Map, Xiaodong Yang
Masters Theses
Motion tracking system in the home-based environment exhibits attractive advantages for stroke patients. Current methods suffer from incapability of accurately tracking movements with high degree of freedoms. Besides hardly meeting the predefined position during inertial sensor mounting also affects system's performance.
To tackle these challenges, a motion tracking system using twist and exponential map technology is developed in this paper. Firstly, a kinematic model for trunk and upper extremity is designed. Based on this model, twist and exponential map method which updates frames in their initial coordinates instead of transforming coordinates from one frame to another presents high efficiency and …
Dynamic Monitoring And Life Prediction Of Internal Strain-Gage Balances, David Leon Yoder
Dynamic Monitoring And Life Prediction Of Internal Strain-Gage Balances, David Leon Yoder
Masters Theses
Wind tunnel test customers continue to push the limits by producing air vehicle designs that produce high aerodynamic loads at the desired test conditions. These loads are a combination of steady aerodynamic, unsteady aerodynamic, and inertial forces. A methodology to monitor the health of a wind tunnel strain-gage balance has been developed. The objective of this methodology is to define the stress limits of the balance and monitor these limits so the balance can be safely tested without failure of the balance. A balance failure could result in costly damage to the wind tunnel model, support system, and the wind …
Numerical Simulation Of High Velocity Impact Of A Single Polymer Particle During Cold Spray Deposition, Sagar P. Shah
Numerical Simulation Of High Velocity Impact Of A Single Polymer Particle During Cold Spray Deposition, Sagar P. Shah
Masters Theses
Abstract
The cold spray process is an additive manufacturing technology primarily suited for ductile metals, and mainly utilized in coating surfaces, manufacturing of freeform parts and repair of damaged components. The process involves acceleration of solid micro-particles in a supersonic gas flow and coating build-up by bonding upon high velocity impact onto a substrate. Coating deposition relies on the kinetic energy of the particles. The main objective of this study was to investigate the mechanics of polymer cold spray process and deformation behavior of polymers to improve technological implementation of the process.
A finite element model was created to simulate …
Jet Flow Validation Of Positron Emission Particle Tracking Utilizing High Speed Video, Seth Thomas Langford
Jet Flow Validation Of Positron Emission Particle Tracking Utilizing High Speed Video, Seth Thomas Langford
Masters Theses
Positron Emission Particle Tracking (PEPT) generates 4D Lagrangian particle trajectories and is used to evaluate flow in granular media and complex geometries where optical interrogation methods are not possible. A Multi-Particle PEPT (Multi-PEPT) approach was developed by the University of Tennessee Thermal Fluids Group capable of finding and tracking many particles simultaneously to extend the utility of the PEPT method. This thesis compares 4,014 trajectories generated using the Multi-PEPT method with 3,055 trajectories generated from High Speed Video (HSV) data. All trajectories are acquired in an acrylic test section with water flow using resin beads. The flow geometry includes a …
Evaluation Of Fuel Flow Measurement Uncertainty In A Turbine Engine Test Cell, Paul Andrew Wright
Evaluation Of Fuel Flow Measurement Uncertainty In A Turbine Engine Test Cell, Paul Andrew Wright
Masters Theses
The evaluation of measurement uncertainty is an essential part of measurement and data analysis. Measurement uncertainty is itself a measure of the “goodness” of the measured data and helps the analyst to make decisions based on the data. In the turbine engine testing world, accurate measurement of fuel flow is critical. Specific fuel consumption is a combination of thrust and fuel flow and is used to calculate the allowable payload and range of an aircraft as well as the cruising speed. Naturally, test customers (engine manufacturers, aircraft designers, and operators) are very sensitive to the accuracy of fuel flow measurement. …
Buckling Of Particle-Laden Interfaces, Theo Dias Kassuga
Buckling Of Particle-Laden Interfaces, Theo Dias Kassuga
Masters Theses
We study the buckling of an oil-water interface populated by micron-sized latex particles using a Langmuir trough. We extend pre-existing results to the micron-range with different capillary length and compare the experimental data to the existing theoretical framework. An unexpected trend for the dominant wavelength of buckling is observed, suggesting that there is a transition between regimes in the micron-range. A mechanism for the new regime is proposed. Cascading is reported, as well as novel kinds of transition between wavelengths within the same particle raft. Lastly, the effect of compression on the macroscopic arrangement of particles is investigated, as well …
Neutron Imaging Of Lithium Inside A High-Temperature Heat Pipe, Eric Henry Kirchoff
Neutron Imaging Of Lithium Inside A High-Temperature Heat Pipe, Eric Henry Kirchoff
Masters Theses
Neutron imaging of a high-temperature Mo-Li [molybdenum-lithium] heat pipe has been performed to assess Li flow visualization. The high neutron attenuation cross section of Li allows for imaging inside the heat pipe shell structure, which has a lower value of neutron attenuation, making neutron radiography an ideal choice for characterizing Li movement.
The gravity assisted, cylindrical heat pipe was heated to 903oC [degree] using a wire resistance Mo heater operating under vacuum. This Mo-Li heat pipe is 35 cm long with a square internal geometry 2.2 cm per side, utilizing small corner radii as the wicking structure for …
Water Transport In Polymer Electrolyte Fuel Cells: An Exploration Of Net Water Drag In Real Time, Susan Katherine Reid
Water Transport In Polymer Electrolyte Fuel Cells: An Exploration Of Net Water Drag In Real Time, Susan Katherine Reid
Masters Theses
Polymer electrolyte fuel cells (PEFCs) are a promising alternative energy source. One challenge preventing widespread use of this technology is water management. A balance must be reached between providing sufficient water for membrane ionic conductivity while maintaining low enough water content to mitigate the reduction of available reaction sites in the cathode catalyst layer due to liquid water build up. Much exploration of this area of fuel cell research has been conducted, but the details of water transport in an operating fuel cell are not yet fully understood. The motivation of this work was to elucidate mass transport phenomena occurring …
Heat Transfer Analysis Via Rate Based Sensors, Jake Erik Plewa
Heat Transfer Analysis Via Rate Based Sensors, Jake Erik Plewa
Masters Theses
This work presents an integrated rate-based sensor and method for resolving the surface heat flux of a fundamental inverse heat conduction problem without numerical regularization or differentiation in a semi-infinite geometry that additionally accounts for thermocouple delay due to its intrinsic time constant. The sensor uses well-designed analog filters to directly regularize raw voltage data to eliminate the need for numerical regularization methods. The sensor can also be used in a series of well-designed voltage-rate interfaces that directly measure the voltages from in-depth thermocouples, which are used in conjunction with the thermocouple calibration curve to provide higher-time derivatives of the …
A Method For Performance Analysis Of A Ramjet Engine In A Free-Jet Test Facility And Analysis Of Performance Uncertainty Contributors, Kevin Raymond Holst
A Method For Performance Analysis Of A Ramjet Engine In A Free-Jet Test Facility And Analysis Of Performance Uncertainty Contributors, Kevin Raymond Holst
Masters Theses
Ramjet and scramjet engines are being developed to provide a more fuel efficient means of propulsion at high Mach numbers. Part of the development of these engines involves test and evaluation of an engine in ground facilities as well as in flight. Ground facilities, like Arnold Engineering Development Center (AEDC) and those at engine manufacturers like General Electric (GE) and Pratt & Whitney (PW), have decades of experience testing traditional turbine engines and much less experience testing full scale ramjet engines.
Testing a supersonic engine model in a free-jet mode presents a host of challenges not experienced during traditional direct …
Test Size And Volume Effects On Fatigue Behavior Of Bulk Metallic Glasses (Bmgs), Qingming Feng
Test Size And Volume Effects On Fatigue Behavior Of Bulk Metallic Glasses (Bmgs), Qingming Feng
Masters Theses
As a potential structural material, performance of bulk metallic glasses (BMGs) under cyclic loading is critical in applications. Among the mechanical properties of metallic glasses, the fatigue behavior received less attention and is not well understood. BMGs exhibit significant size effects on the mechanical behavior under monotonic loading, such as compression, tension, and bending. At the same time, different test-volume could lead to a distinct difference in the mechanical behavior of BMGs.
The fatigue behavior of the Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 [atomic percent (at. %)] BMG alloy (Vitreloy 105) with different sizes has been …
Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke
Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke
Masters Theses
In low-pressure steam turbines, water droplet formation on the surfaces of stationary stator blades can lead to erosion on downstream turbine blades and other equipment. One property that affects the size of the droplets that are formed is the adhesive forces between the water and the surface of the stator blade. The adhesive forces hold the droplets to the surface where they may combine, forming increasingly larger droplets. Eventually, the aerodynamic forces will tear the droplets off the surface, carrying them downstream.
To study the effect of stator surface properties on the droplet size distribution, four cascades of stator blades …
Residential Attic Ventilation In A Hot And Humid Climate: Effects Of Increased Ventilation On Thermal Performance And Moisture Control, Stanley Arthur Atherton
Residential Attic Ventilation In A Hot And Humid Climate: Effects Of Increased Ventilation On Thermal Performance And Moisture Control, Stanley Arthur Atherton
Masters Theses
The reality of the effect of natural ventilation in a residential attic cavity has been the topic of many debates and scholarly reports since the 1930’s. The purpose of ventilating an attic cavity is to prevent collection of condensate on the structural surfaces, and to create a thermal buffer between the conditioned space and the ambient air. The current standards are not specific to climate zone, despite the fact that each climate zone may require ventilation for very different reasons.
To address the issue of ventilation effects in a hot and humid climate, a Natural Exposure Testing facility was constructed …
Thermocouple Temperature Measurements For Twin Jet Thermal Mixing, Spero Michael Peters
Thermocouple Temperature Measurements For Twin Jet Thermal Mixing, Spero Michael Peters
Masters Theses
Thermocouples are commonly used devices for temperature measurement. This study concerns the implementation of thermocouples to collect thermal mixing data in an environment in which two parallel water jets are mixing. The measurements are taken with the purpose of modeling the jet mixing region so that Computational Fluid Dynamics (CFD) models can be validated against the test data. This thesis covers the design, construction, implementation and evaluation of a thermocouple system for immersion in a water environment to measure the thermal mixing of twin jets.
The measurement system being used is a thermocouple rake whose design and fabrication is covered. …