Mechanical Engineering Commons^™

System Optimization And Material Development Of Solid Oxide Cells For Energy Conversion And Storage, Libin Lei

Theses and Dissertations

Solid oxide cells (SOCs) can convert chemical energy to electricity in the fuel cell mode and store electricity to chemicals in the electrolysis mode. However, there are still critical barriers, such as energy efficiency and durability, for the development and commercialization of SOCs. The objective of this dissertation is to apply system optimization and materials design to address the critical barriers for solid oxide cells in energy conversion and energy storage applications. One major focus of the dissertation is related to improve energy efficiency, enhance the cell performance and achieve multifunctionality in solid oxide electrolysis cells (SOECs). In addition, development …

Characterization Of Evaporation/Condensation During Pool Boiling And Flow Boiling, Mostafa Mobli

Theses and Dissertations

Present dissertation has investigated pool and flow boiling and their characteristics via numerical means. A code was developed to investigate and enhance heat transfer performance during different modes of phase change phenomena. Multiphase heat transfer has proven to be one of the most effective means of heat transfer in different industries, therefore, there have been numerous experimental and numerical studies on the subject of phase change phenomena in a wide range of conditions and setups; yet there are complex bubble dynamics and heat transfer characteristics that remain unresolved. To have a more detailed look at and a better understanding of …

Analysis Of Pellet-Cladding Mechanical Interaction On U3si2 Fuel With A Multi-Layer Sic Cladding Using Bison, Ray A. Freeman

Theses and Dissertations

U3Si2 is currently being considered as a possible replacement for the current light water reactor fuel, UO2. U3Si2’s high melting temperature, high uranium density, and high thermal conductivity are favorable in accident conditions, such as a loss of coolant accident. Improved accident performance is further expected when paired with a SiC/SiC cladding, since it provides relatively high strength and a high oxidation resistance.

Modeling of U3Si2 and SiC/SiC in reactor is currently very important since much of their behavior is still unknown. By implementing models that describe the properties of U3Si2 and SiC/SiC into INL’s fuel performance code BISON, performance …

Physics-Based Approaches For Structural Health Monitoring And Nondestructive Evaluation With Ultrasonic Guided Waves, Md Yeasin Bhuiyan

Theses and Dissertations

The engineering infrastructures have a growing demand for damage monitoring systems to avoid any potential risk of failure. Proper damage monitoring solutions are of a great interest to this growing demand. The structural health monitoring (SHM) and nondestructive evaluation (NDE) offer appropriate online and offline damage monitoring solutions for a variety of mechanical and civil infrastructures that includes unmanned aerial vehicles (UAV), spaceships, commercial aircraft, ground transportation, wind turbines, nuclear spent fuel storage tanks, bridges, naval ships, and submarines. The fundamentals of the ultrasonic SHM and NDE consist of multi-disciplinary fields. The dissertation addresses SHM and NDE using ultrasonic guided …

Effect Of Weak Adhesion Interface On Mechanical And Dielectric Properties Of Composite Materials, Prashant Katiyar

Theses and Dissertations

Interfaces are often the most critical part of the heterogeneous materials and their structures. Such interfaces appear a multiple length scales and significantly affect bulk properties in different material systems. Fiber reinforced composite materials are one such example of heterogeneous materials with interfaces at constituent scale (fiber-matrix interface and interphase) to laminate scale (secondary adhesive joints). Manufacturing induced defects and subsequent in-service damage at these interfaces can severely affect the durability of fiber reinforced laminated composite materials and their joints. In addition to lamination process, defects can also form during secondary joining process (e.g., adhesive bonding and repair) which can …

High Temperature Compression Creep Of U3si2, Emil Angelo Cahanap Mercado

Theses and Dissertations

As a result of the Fukushima Daiichi Nuclear Disaster in 2011, a push for increasing the safety of nuclear power plants was made through research grants funded through the United States Department of Energy via the Accident Tolerant Fuels (ATF) campaign. One of the focuses of the campaign is improving the accident tolerance of nuclear fuel during a loss of coolant accident.

A promising set of being researched from the ATF is Silicon Carbide (SiC) composite cladding and Uranium Silicide (U3Si2) fuel pellets. Under high temperatures, stresses, and times the creep deformation can play an important factor in pellet to …

Combustion Behavior Of Sub-Millimeter Sized Oxygenated And N-Alkane Fuel Droplets, Mohammad Fahd Ebna Alam

Theses and Dissertations

The primary scientific explorations of this thesis work are to better understand (a) microgravity fire-suppression of untested extinguisher, (b) combustion kinetic model refinement of renewable fuel butanol (C4H9OH) isomers, and (c) directly induced cool flame dynamics of higher n-alkane fuels from an isolated small droplet combustion perspective employing computational fluid dynamics with comprehensive chemical kinetics. The chronological development of the research direction shifts from a relatively small fuel like methanol (CH3OH) to heavier straight paraffinic fuel n-decane (n-C10H22). The first installment of the thesis is directed towards answering the feasibility of thennewly considered fire suppressant xenon (Xe) for microgravity space …

Monitoring The Progress Of Damage In A Sicf-Sicm Composite Nuclear Fuel Cladding Under Internal Pressure Using Acoustic Emission, Luis H. Alva

Theses and Dissertations

The relation between the progress of damage and the acoustic emission (AE) activity of a nuclear grade Sif-SiCm composite tubing under internal pressure was studied. The nuclear grade Sif-SiCm composite tubing is manufactured by the company General Atomics (GA) and made of nuclear grade HI Nicalon type S fiber preforms following a chemical vapor infiltration (CVI) technique. Sif-SiCm composites are good candidates to replace current nuclear fuel cladding materials because of the good chemical stability and strength at high temperatures. In this work, a Sif-SiCm composite tubing was tested under internal pressure at room temperature (RT) to study the damage …

Enhance Flow Boiling In Microchannels By Regulating Two-Phase Transport Patterns, Wenming Li

Theses and Dissertations

Flow boiling in microchannels is one of the most promising cooling techniques for microelectronics. Using latent heat by vaporization can significantly improve heat dissipation of high power density electronic devices. Most of the failure of electronic devices is induced by the occurrence of critical heat flux (CHF), which defines the maximum operating conditions. However, the vigorous rapid generation of vapor through phase change leads to chaotic two-phase flows in microchannels, resulting in flowinstability in terms of severe flow, temperature and pressure drop fluctuations. Particularly, the very well-known bubble confinement exacerbates the two-phase flow instabilities and greatly deteriorates heat transfer performance …

Effect Of Material Orientation On The Impact Response Of Graded Cellular Materials, Abigail Wohlford

Theses and Dissertations

In this study, the effect of layer stacking on the energy absorption characteristics of density-graded cellular polymers subjected to high velocity impact is investigated experimentally. The focus in the present work is to characterize the constitutive response and deformation mechanisms of these Functionally Graded Foam Materials (FGFM) using full-field measurements. Uniform foam Quasi-static and dynamic testing of uniform foam specimens are completed for each nominal density used in the layered foam samples. The low strain-rate experiments are performed in order to determine the mechanical properties of foam specimens. The high-rate experiments for homogenous foam specimens were completed to further characterize …

Acousto-Ultrasonic Shm/Nde Methods Toward Field Application, Stephen Harris Howden

Theses and Dissertations

Acousto-ultrasonic nondestructive evaluation (NDE) and structural health monitoring (SHM) methods offers solutions in damage detection, material properties evaluation and more. These ultrasonic waves can propagate through solids and interact with structural features and discontinuities. In this thesis use of several acousto-ultrasonics NDE/SHM methods were explored to evaluate their sensing and detection capabilities toward damage detection field applications in nuclear and aerospace industries.

For nuclear applications, passive sensing using piezoelectric sensors and acoustic emission (AE) techniques were explored on the spent fuel dry storage casks. Dry storage casks are used in the nuclear industry to transport or store spent nuclear fuel …

Fiber Optic Guided Wave Sensors For Structural Health Monitoring, Erik Frankforter

Theses and Dissertations

Risks and costs associated with aging infrastructure have been mounting, presenting a clear need for innovative damage monitoring solutions. One of the more powerful damage monitoring approaches involves using ultrasonic guided waves which propagate through a structure and carry damage-related information to permanently bonded sensors. Ultrasonic fiber-optic sensors are one of the most promising technologies for this application: they are immune to electromagnetic interference, present no ignition hazard, and transmit their data over tens of kilometers. However, before they can be widely employed, several limitations need to be overcome: poor sensitivity, unidirectional sensing, and loss of ultrasonic functionality due to …

Numerical Analysis Of Phase Change, Heat Transfer And Fluid Flow Within Miniature Heat Pipes, Mehdi Famouri

Theses and Dissertations

Heat pipes with broad applications in thermal systems have the ability to provide effective heat transport with minimal losses in over reasonable distances due to their passive nature. Their exceptional flexibility, simple fabrication, and easy control, not to mention, all without any external pumping power make them especially attractive in electronics cooling. Heat pipe development is motivated to overcome the need to presumably manage thermal dissipation in progressively compressed and higher-density microelectronic components, while preserving the components temperatures to specification.

Computation of flow and heat transfer in a heat pipe is complicated by the strong coupling among the velocity, pressure …

A Comprehensive Evaluation Of Hybrid Wetting Configurations On Dropwise Condensation, Karim Khazal Egab

Theses and Dissertations

The heat transfer during condensation on a surface depends on the pattern design of the surface, which can highly influence hydrophobic/hydrophilic wettability. In this study hybrid pattern designs were studied. The relationship between the droplet dynamic and the hybrid pattern design can alter the drainage rates, droplet departure frequencies, and the condensation heat transfer rates. Therefore, two series of hybrid patterned surfaces have been designed, developed, and tested during condensation of water vapor on horizontal copper tubes, and compared to complete dropwise and complete filmwise condensation samples. This is to investigate the design that provides the maximum improvement in the …

On The Microstructural Behavior Of Pure Magnesium Under Various Strain Rates, Peter Malchow

Theses and Dissertations

An investigation into the localized microstructural response of pure magnesium under both quasi-static and dynamic loading is presented in the form of several experimental works. The meso-scale events were examined using Digital Image Correlation techniques, which provide a methodology for mapping the in-situ full-field material strain behavior.

Firstly, an analysis of the grain boundary activity specifically under dynamic conditions at high magnification is discussed. An area of interest in the region of multiple grain boundaries and triple junctions is selected for characterizing the evolution of the strain and local rotation. This is followed by a study experimentally verifying the causes …

Multi-Axis Multi-Material Fused Filament Fabrication With Continuous Fiber Reinforcement, Wout De Backer

Theses and Dissertations

Additive Manufacturing (AM) has become a well-recognized method of manufacturing and has steadily become more accessible as it allows designers to prototype ideas, products and structures unconceivable with subtractive manufacturing techniques for both consumer grade and industrial grade applications. Commonly used thermoplastics for 3D printing have properties that may not be sufficient to comply with the application’s certification requirements, or their performance is less than desirable for aerospace and other high performance applications. Additionally, additively manufactured parts have reduced mechanical properties in the build direction of the print, and are generally weaker than their equivalent injection-molded parts. Furthermore, Computer Aided …

Experimental And Numerical Investigation Of Pressure Drop In Silicon Carbide Fuel Rod For Application In Pressurized Water Reactors, Ahmed Musafi Abir

Theses and Dissertations

Spacer grids are used in pressurized water reactors (PWRs) fuel assemblies which enhances heat transfer from fuel rods. However, there remain regions of low turbulence in between the spacer grids which contributes to lower heat transfer. To enhance turbulence in these regions surface roughness is applied on the fuel rod walls. Meyer et al [1] used empirical correlations to predict heat transfer and friction factor for artificially roughened fuel rod bundles at high performance light water reactors (LWRs). At present, several types of materials are being used for fuel rod cladding including zircaloy, uranium oxide, etc. But researchers are actively …

Nondestructive Evaluation And Health Monitoring Of Adhesively Bonded Composite Structures, William Walker Roth

Theses and Dissertations

As the growth of fiber reinforced composite materials continues in many industries, structural designers will have to look to new methods of joining components. In order to take full advantage of composite materials, such as increased stiffness, decreased weight, tailored material properties and increased fatigue life, mechanical fasteners will need to be replaced by adhesive bonding or welding, when possible. Mechanical fasteners require the drilling of holes, which damages the laminate and becomes the source of further fatigue damage. Also, an increase in laminate thickness or inclusion of other features is required for the material to withstand the bearing stress …

Promotional Effect Of Molten Carbonates On Proton Conductivity And Oxygen Reduction Reaction – An Experimental And Computational Study, Xiaolei Xiong

Theses and Dissertations

Recent research of Solid oxide fuel cells (SOFCs) is aimed to lower the operating temperature to an intermediate temperature (IT) range of 500 to 700^oC, while maintaining a proper performance. This Ph.D. research project investigates the promotional effects of alkaline carbonate eutectics on the proton conductivity of proton conducting electrolytes and cathodic ORR reactivity in SOFCs by both experimental and computational methods. The ionic conductivity of the MC-BZY composite above 500^oC increases with the higher loading of MC. The sample exhibited nearly a factor of two higher conductivity in H₂-containing atmosphere than in air. …

Non-Destructive Evaluation Of Composites: Predictive Ultrasonic Guided-Waves Modeling, Non-Destructive Material Characterization, And The Application To Aerospace Structures, Darun Barazanchy

Theses and Dissertations

To predict guided wave dispersion curves, it is common to use different solution approaches depending on the material type (isotropic or anisotropic) of the medium in which the wave propagates. The two different solution methods are defined in different domains, frequency-phase velocity domain for isotropic materials and wavenumber-phase velocity domain for anisotropic materials. This may lead to difficulties and unsatisfying results when predicting the dispersion curves for hybrid laminates which contain both isotropic and anisotropic materials. Therefore, a unified formulation defined in the wavenumber-phase velocity domain to accomodate both isotropic and anisotropic materials, as well as hybrid combinations, is desired. …

Enhanced Dropwise Condensation Via Wettability Contrast Mechanism, Mohammad Alwazzan

Theses and Dissertations

Condensation heat transfer performance can be improved by many methods including the most common used method, which is by increasing the droplet removal rate of the condensing surface. Commonly, this approached can be achieved by promoting a dropwise condensation mode in which super/hydrophobic coatings can be applied on the entire condenser surface to reduce the surface wettability degree. In this dissertation, two main approaches were adapted to enhance the condensation heat transfer performance of the condensing surface via wettability contrast mechanism. Three approaches of investigation were performed to better understand such dropwise condensation promoter methods.

In the first part, alternative …

Study Of Friction Extrusion And Consolidation, Xiao Li

Theses and Dissertations

Friction extrusion and consolidation was invented by The Welding Institute (Cambridge, UK) in the early 1990’s. It is related to simple extrusion processes with the primary difference being that the extrusion die rotates about the extrusion axis and the die is required to impart substantial deformation to the initially, finely divided charge (like metal waste or chips) in order to consolidate it prior to extrusion. It can produce high quality wire and fully consolidated bulk material from low-cost precursors like metal chips or powders. The advantages lie in that it is a direct method to recycle metal chips or scraps …

Numerical Modeling Of Heat Transfer And Material Flow During Friction Extrusion Process, Hongsheng Zhang

Theses and Dissertations

Friction extrusion process is a novel manufacturing process that converts low-cost metal precursors (e.g. powders and machining chips) into high-value wires with potential applications in 3D printing of metallic products. However, there is little existing scientific literature involving friction extrusion process until recently. The present work is to study the heat transfer and material flow phenomena during the friction extrusion process on aluminum alloy 6061 through numerical models validated by experimental measurements.

The first part is a study of a simplified process in which flow of a transparent Newtonian fluid in a cylindrical chamber caused by frictional contact with a …

Physics Based Modeling Of Guided Waves For Detection And Characterization Of Structural Damage In Nde And Shm, Banibrata Poddar

Theses and Dissertations

Guided waves based damage detection techniques are popular for their ease of generation and detection along with their ability to travel long distances. Accurate and efficient modeling is a key for successful implementation of guided waves for NDE/SHM. However, efficient prediction of scattering from various damage is challenging due to the complex nature of these guided waves.

This dissertation presents as physics based efficient and accurate modeling techniques to predict ultrasonic wave propagation and their interaction with various damage. Detection and characterization of damage in structures can typically be divided into two categories, active and passive. This research is aimed …

Modeling Radionuclide Diffusion Using Moose A Multiscale, Multiphysics Platform, Jonathon Gardner

Theses and Dissertations

Very durable ceramic waste forms have been proposed which offer longterm stability by binding certain radionuclides in their specific crystalline network. Moreover, multiple such ceramic phases can be tailored to contain specific radionuclides generated in the fuel cycle. Many such candidate ceramic forms are in the early stages of development with limited data. Modeling and simulation including modeling of diffusion can inform and provide direction to ongoing fabrication and experimental efforts. Material properties important in modeling can be obtained through laboratory measurement where available and atomistic simulation. Since diffusion occurs over multiple scales and follows multiple pathways, multiscale modeling is …

Techno Economical Analysis Of Solid Oxide Iron-Air Redox Battery For Power Generation And Energy Storage, Farzana Yasmeen

Theses and Dissertations

The largest source of greenhouse gas emissions in the United States is from burning fossil fuels for electricity, heat, and transportation. Due to increasing environmental constraints associated with greenhouse gas emissions and uncertainty in the supply of fossil fuels, power systems of the future will become more reliable on renewable power source. To overcome the intermittency issue of renewable power, a promising cost effective electricity-storage systems is vital. The U.S. Department of Energy (DOE) has established detailed cost targets for energy storage system. One of the targets is capital cost which should be under $150/kWh for new technology. Another target …

Nano Oil Additives And Their Effect On Uh-60 Auxiliary Power Unit Performance, James Patrick Folk

Theses and Dissertations

This study is designed to research the tribological properties of nano oils developed by NanoPro MT and to determine their effects on fuel consumption in an UH-60 Blackhawk Auxiliary Power Unit (APU). For this work, two different nano oils were tested and compared against the performance of conventional oil. The first nano oil mixture contains proprietary nanodiamond particles and the second nano oil contains a mix of zinc sulfide, boron nitride, and graphene particles. Aeroshell 560 was used as the conventional oil and was blended with the nano particles to create both nano oils. This oil meets the military specifications …

Numerical Studies Of Arterial Tissue Failure, Xiaochang Leng

Theses and Dissertations

Arterial tissue failure leads to a number of potentially life-threatening clinical conditions, such as atherosclerotic plaque rupture and aortic dissection which develop unpredictably and rapidly in vivo. Thus, a full understanding of the two conditions will provide a solid basis for medical advances in the intervention and prevention of the occurrence of this life-threatening event. The present work aims to develop a cohesive zone model (CZM) approach for analysis and simulation of arterial tissue failure, such as plaque and fibrous cap delamination and tearing, and to validate simulation predictions with experimental results.

To characterize the hysteresis phenomenon of diseased aortic …

Estimation Of Basic And Mission Benefit Of Condition-Based Maintenance Deployment In Hums Equipped Ah-64 Aircraft Using Nlp And Regression Analysis, Tanzina Zaman

Theses and Dissertations

Condition-based maintenance (CBM) is a maintenance practice that involves regular monitoring of the mechanical condition of components of interest, processing of information collected, and then decision-making to ensure both maximizing the time interval between repairs and minimizing the number of unscheduled failures. CBM also offers early detection of failure which can prevent major breakdowns and repairs. Vibration monitoring is one of the effective techniques for condition monitoring. Health and Usage Monitoring System (HUMS) is a powerful tool for aviation industry which monitors health status and trending data. Vibration Monitoring Unit (VMU) and Modernized Signal Processing Unit (MSPU) are two forms …

Anisotropic Electrical Response Of Carbon Fiber Reinforced Composite Materials, Mohammad Faisal Haider

Theses and Dissertations

Composites materials are often subjected to multi-physical conditions in different applications where, in addition to mechanical loads, they also need to sustain other types of loads such as electrical currents. The multi-physical behavior of composites needs to be understood and analyzed to facilitate new multi-functional material design. An essential first step towards this goal is to understand how multi-physics properties depend on local details (e.g. micro-structure). Composite materials have heterogeneous electrical properties (carbon/epoxy) at the local level that can be different at the global level. To conduct the multi-physics study, the electrical signal is employed to the composite sample for …