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Integration Of Process Parameter Control And Digital Image Correlation Methods In An Investigation Of The Variability Of Marine Polymer Matrix Composite Material Properties, Keith Andrew Berube

Electronic Theses and Dissertations

The very nature of continuous fiber composite materials, with their heterogeneous structure of layered and interwoven fibers bound together by a polymer resin matrix, lead to an inevitable variability in mechanical properties. This is especially true if the fabrication process is not well controlled. Unlike fabricating components with metals, where the properties of the material are known beforehand, the final properties of the composite material are determined during the process of fabricating the composite part. The research described herein was undertaken to better enable the use of polymer matrix composites in the marine construction industry by developing a knowledge base …

Towards A Fluid Solid Interaction Model Of A Dynamic Lung, Justin C. Jacobs

Electronic Theses and Dissertations

Because the pulmonary system is a site for both environmental particulate contamination, as well as drug delivery into the body, numerous research groups have focused on precisely understanding its inner-workings. Past research has demonstrated the need to realistically model the lung walls in order to accurately capture the complex airflow profile throughout all of the branches. Since this is paramount to properly replicating particulate transport in the lung, computational fluid dynamics simulations on their own are inadequate, as they cannot account for lung wall dilation. Only by coupling the fluid and solid domains can natural lung behavior can be effectively …

Testing Of A Ducted Axial Flow Tidal Turbine, Thomas A. Lokocz

Electronic Theses and Dissertations

Energy independence and a reduction on the reliance on fossil fuels is a critical area of current research and development. Utilizing the energy in the world’s oceans can help the world move towards a more sustainable energy supply. One of the most promising sources of ocean energy is tidal energy or marine hydrokinetics, the topic of this thesis. This research analyzes the performance of a ducted axial flow tidal turbine and compares the result to an unducted turbine. While the focus of this research is on experimental results obtained in tow tank tests, the turbine and duct were designed using …

Flow Field Measurements For A Cross Flow Turbine, Matthew Cameron

Electronic Theses and Dissertations

Understanding the flow pattern around hydrokinetic devices is important for the development of tidal energy technology. The objective of the research is to provide the wake characteristics from laboratory measurements, including wake structure, and flow recovery in the near and far fields of a cross-flow turbine. The data can be used to assist in optimization of an array of turbines by providing experimental results for numerical models validation and industrial developers of tidal energy. Another critical use of this data will be to provide a basis for parameterization of energy extraction in coastal ocean models in resource assessment. The experimental …

Evaporation, Precipitation Dynamics And Instability Of Acoustically Levitated Functional Droplets, Abhishek Saha

Electronic Theses and Dissertations

Evaporation of pure and binary liquid droplets is of interest in thermal sprays and spray drying of food, ceramics and pharmaceutical products. Understanding the rate of heat and mass transfer in any drying process is important not only to enhance evaporation rate or vapor-gas mixing, but also to predict and control the final morphology and microstructure of the precipitates. Acoustic levitation is an alternative method to study micron-sized droplets without wall effects, which eliminates chemical and thermal contamination with surfaces. This work uses an ultrasonic levitation technique to investigate the vaporization dynamics under radiative heating, with focus on evaporation characteristics, …

Towards Scalable Nanomanufacturing: Modeling The Interaction Of Charged Droplets From Electrospray Using Gpu, Weiwei Yang

Electronic Theses and Dissertations

Electrospray is an atomization method subject to intense study recently due to its monodispersity and the wide size range of droplets it can produce, from nanometers to hundreds of micrometers. This thesis focuses on the numerical and theoretical modeling of the interaction of charged droplets from the single and multiplexed electrospray. We studied two typical scenarios: large area film depositions using multiplexed electrospray and fine pattern printings assisted by linear electrostatic quadrupole focusing. Due to the high computation power requirement in the unsteady n-body problem, graphical processing unit (GPU) which delivers 10 Tera flops in computation power is used to …

Numerical Study On Reinforcement Mechanism Of Copper/Carbon Nanotubes Composite, Xiang Long

Electronic Theses and Dissertations

Because of its high stiffness, carbon nanotubes (CNTs) are considered as one of the widely used reinforcement materials in the metal matrix composites. In this thesis, finite element (FE) models were built in Ls-Dyna3D to simulate Copper/CNTs composite deformation and fracture, and to explore CNTs reinforcement mechanisms. Several possible mechanisms were discussed. Deformation and failure of Cu/CNT composites were studied numerically using unit cell FE models, which consist of both metal matrix and CNTs. The simulation results have been verified by existing experiment data reported by Chen’s group. The matrix material was modeled as elasto-plastic ductile solids. The CNTs material …

Fire Retardant Polymer Nanocomposites: Materials Design And Thermal Degradation Modeling, Jinfeng Zhuge

Electronic Theses and Dissertations

Compared to conventional materials, polymer matrix composites (PMCs) have a number of attractive properties, including light weight, easiness of installation, potential to lower system-level cost, high overall durability, and less susceptibility to environmental deterioration. However, PMCs are vulnerable to fire such that they degrade, decompose, and sometimes yield toxic gases at high temperature. The degradation and decomposition of composites lead to loss in mass, resulting in loss in mechanical strength. This research aims to improve the structural integrity of the PMCs under fire conditions by designing and optimizing a fire retardant nanopaper coating, and to fundamentally understand the thermal response …

Numerical Simulation Of Electrolyte-Supported Planar Button Solid Oxide Fuel Cell, Amjad Aman

Electronic Theses and Dissertations

Solid Oxide Fuel Cells are fuel cells that operate at high temperatures usually in the range of 600oC to 1000oC and employ solid ceramics as the electrolyte. In Solid Oxide Fuel Cells oxygen ions (O2- ) are the ionic charge carriers. Solid Oxide Fuel Cells are known for their higher electrical efficiency of about 50-60% [1] compared to other types of fuel cells and are considered very suitable in stationary power generation applications. It is very important to study the effects of different parameters on the performance of Solid Oxide Fuel Cells and for this purpose the experimental or numerical …

A Bench Top Study Of The Optimization Of Lvad Cannula Implantation To Reduce Risk Of Cerebral Embolism, William D. Clark

Electronic Theses and Dissertations

Physical bench top experiments are performed to validate and complement ongoing computational fluid dynamics (CFD) analyses of ventricular assist device (VAD) circulation. VADs are used in patients whose hearts do not function to their maximum potential due advanced stages of heart disease and, consequently, are unable to adequately supply blood to the systemic circulation. VADs are commonly utilized as a bridge-to-transplantation, meaning that they are implanted in patients while waiting for a heart transplant. In such cases of long term utilization of VADs, it has been reported in the literatures that thrombo-embolic cerebral events occur in 14-47% of patients over …

Characterization Of Dynamic And Static Mechanical Behavior Of Polyetherimide, Nathan J. Mutter

Electronic Theses and Dissertations

Polymers are increasingly being used in engineering designs due to their favorable mechanical properties such as high specific strength, corrosive resistance, manufacturing flexibility. The understanding of the mechanical behavior of these polymers under both static and dynamic loading is critical for their optimal implementation in engineering applications. One such polymer utilized in a wide variety of applications from medical instrumentation to munitions is Polyetherimide, referred to as Ultem. This thesis characterizes both the static and dynamic mechanical behavior of Ultem 1000 through experimental methods and numerical simulations. Standard compression experiments were conducted on and MTS test frame to characterize the …

Simulation Of A Capacitive Micromachined Ultrasonic Transducer With A Parylene Membrane And Graphene Electrodes, David Sadat

Electronic Theses and Dissertations

Medical ultrasound technology accounts for over half of all imaging tests performed worldwide. In comparison to other methods, ultrasonic imaging is more portable and lower cost, and is becoming more accessible to remote regions where traditionally no medical imaging can be done. However, conventional ultrasonic imaging systems still rely on expensive PZT-based ultrasound probes that limit broader applications. In addition, the resolution of PZT based transducers is low due to the limitation in hand-fabrication methods of the piezoelectric ceramics. Capacitive Micromachined Ultrasonic Transducers (CMUTs) appears as an alternative to the piezoelectric (PZT) ceramic based transducer for ultrasound medical imaging. CMUTs …

Laser Spark Ignition Of Counter-Flow Diffusion Flames: Effects Of Diluents And Diffusive-Thermal Properties, Fidelio Sime Segura

Electronic Theses and Dissertations

A pulsed Nd:YAG laser is used to study laser spark ignition of methane counter-flow diffusion flames with the use of helium and argon as diluents to achieve a wide range of variations in transport properties. The global strain rate and Damkohler number on successful ignition were investigated for the effects of Lewis number and transport properties, which are dependent on the diluent type and dilution level. A high-speed camera is used to record the ignition events and a software is used for pre-ignition flow field and mixing calculations. It is found that the role of effective Lewis number on the …

Process Optimization Towards The Development Of An Automated Cnc Monitoring System For A Simultaneous Turning And Boring Operation, Manuel Hernandez

Electronic Theses and Dissertations

Manufacturing operations generate revenue by adding value to material through machine work and the cost associated with part production hinders the maximum profit available. In order to remain competitive, companies invest in research to maximize profit and reduce waste of manufacturing operations. This results in cheaper products for the customer without sacrificing quality. The purpose of this research was to identify machine settings of an Okuma LC 40 Turning Center and optimize the cost of machining in terms of tool cost and energy consumption while maintaining part quality at a productive cycle time. Studying the relationship between energy consumption, tool …

Feature-Based Neuro-Symbolic Networks For Global Diagnostics, Tracy Lynn Schantz

Electronic Theses and Dissertations

Engineered system diagnostics have been researched over the years with many successful results. From transportation systems to office technologies, many have been equipped with self-diagnostic capabilities and are called Smart Machines. In spite of these advances, current diagnostic systems are driven by direct sensory information without much concern for patterns of the system behavior or features associated with them. For large-scale systems with complex dynamics, global as well as local diagnostics become of great importance, where sensory information is used as input for the local diagnostics, and patterns of behavior or features are utilized for global diagnostics.

The main objective …

Micro Channel Cooler Performance Improvement By Insonation, Peter Webb Higgins

Electronic Theses and Dissertations

The motivation for this work is the need to remove waste heat from laser diodes and high speed transistors in processes which are exponentially increasing past 1 kW/cm2 as anticipated by Moore's Law. The hypothesis guiding the work is that ultrasonic insonation of micro coolers employed to dissipate these heat loads can improve heat removal. It is thought that the mechanism promoting the benefit is enhancement of the ability of the coolant to remove latent heat in two-phase operation by managing entrained bubble size near the cooler's exit so as to forestall flow reduction or blockage caused by large bubbles, …

A Comparative Study Of Segmented Tungsten Rod Penetration Into A Thick Steel Target Plate, Michael Bryant Presnell

Electronic Theses and Dissertations

This thesis presents results from computational simulations of tungsten alloy segmented rod projectiles (SRP) penetrating an RHA semi-infinite target plate at high velocities. Penetration experimental data show improved penetration efficiency by the segmented projectiles when compared to monolithic (single solid rod) projectiles. For SRP with an aspect ratio (L/D) = 1/8, a loss in penetration efficiency was seen upon successive segment impacts. A numerical simulation impacting tungsten heavy alloy against RHA 4340 steel was performed using the Lagrangian finite element code EPIC 2006. The impact configuration that was modeled consisted of eight successive collinear impacts of discs measured 2mm in …

Computationally Efficient Finite Element Models Of The Lumbar Spine For The Evaluation Of Spine Mechanics And Device Performance, Sean D. Smith

Electronic Theses and Dissertations

Finite Element models of the lumbar spine are commonly used for the study of spine mechanics and device performance, but have limited usefulness in some applications such as clinical and design phase assessments due to long analysis times. In this study a computationally efficient L4-L5 FSU model and a L1-Sacrum multi-segment model were developed and validated. The FSU is a functional spine unit consisting of two adjacent vertebral bodies, in this case L4 and L5. The multi-segment model consists of all lumbar vertebrae and the sacrum. The models are able to accurately predict spine kinematics with significantly reduced analysis times, …

Simulation Of Heat/Mass Transfer Of A Three-Layer Impingement/Effusion Cooling System, Brandon Smith

Electronic Theses and Dissertations

Cooling techniques for high density electrical components and electronic devices have been studied heavily in recent years. The advancements in the electrical/electronic industry have required methods of high heat flux removal. Many of the current electrical components and electronic devices produce a range of heat fluxes from 20 W/cm2 – 100 W/cm2 . While parallel flow cooling systems have been used in the past, jet impingement is now more desirable for its potential to have a heat transfer coefficient 3-5 times greater than that of parallel flow at the same flow rate. Problems do arise when the jet impingement is …

Optimization Of Ocean Thermal Energy Conversion Power Plants, Steven Emanoel Rizea

Electronic Theses and Dissertations

A proprietary Ocean Thermal Energy Conversion (OTEC) modeling tool, the Makai OTEC Thermodynamic and Economic Model (MOTEM), is leveraged to evaluate the accuracy of finite-time thermodynamic OTEC optimization methods. MOTEM is a full OTEC system simulator capable of evaluating the effects of variation in heat exchanger operating temperatures and seawater flow rates. The evaluation is based on a comparison of the net power output of an OTEC plant with a fixed configuration. Select optimization methods from the literature are shown to produce between 93% and 99% of the maximum possible amount of power, depending on the selection of heat exchanger …

Aerodynamic Characteristics Of A Gas Turbine Exhaust Diffuser With An Accompanying Exhaust Collection System, Bryan Bernier

Electronic Theses and Dissertations

The effects of an industrial gas turbine’s Exhaust Collector Box (ECB) geometry on static pressure recovery and total pressure loss were investigated in this study experimentally and computationally. This study aims to further understand how exit boundary conditions affect the performance of a diffuser system as well as the accuracy of industry standard computational models. A design of experiments approach was taken using a Box-Behnken design method for investigating three geometric parameters of the ECB. In this investigation, the exhaust diffuser remained constant through each test, with only the ECB being varied. A system performance analysis was conducted for each …

Coupled Usage Of Discrete Hole And Transpired Film For Better Cooling Performance, Michael Torrance

Electronic Theses and Dissertations

Electricity has become so ingrained in everyday life that the current generation has no knowledge of life without it. The majority of power generation in the United States is the result of turbines of some form. With such widespread utilization of these complex rotating machines, any increase in efficiency translates into improvements in the current cost of energy. These improvements manifest themselves as reductions in greenhouse emissions or possible savings to the consumer. The most important temperature regarding turbine performance is the temperature of the hot gas entering the turbine, denoted turbine inlet temperature. Increasing the turbine inlet temperature allows …

Re, Os, Al And Mg Boron Rich Ceramic Compounds For Structural Application, Zhilin Xie

Electronic Theses and Dissertations

Hard and ultra-incompressible materials are of great interest due to their important applications in industry. A common route to design hard materials is combining transition metals with light and small covalent elements. Light elements such as carbon, oxygen, nitrogen and boron have been considered as good candidates. This study includes the synthesis of ReB2, OsB2 and another higher boride AlMgB14. Most of the techniques used for ReB2 synthesis reported 1:2.5 Re to B ratio because of the loss of the B during high temperature synthesis. However, as a result of B excess, the amorphous boron, located along the grain boundaries …

The Effect Of Magnetic Bearing On The Vibration And Friction Of A Wind Turbine, Mark Ryan Vorwaller

Electronic Theses and Dissertations

Demands for sustainable energy have resulted in increased interest in wind turbines. Thus, despite widespread economic difficulties, global installed wind power increased by over 20% in 2011 alone. Recently, magnetic bearing technology has been proposed to improve wind turbine performance by mitigating vibration and reducing frictional losses. While magnetic bearing has been shown to reduce friction in other applications, little data has been presented to establish its effect on vibration and friction in wind turbines. Accordingly, this study provides a functional method for experimentally evaluating the effect of a magnetic bearing on the vibration and efficiency characteristics of a wind …

Deformation And Phase Transformation Processes In Polycrystalline Niti And Nitihf High Temperature Shape Memory Alloys, Othmane Benafan

Electronic Theses and Dissertations

The unique ability of shape memory alloys (SMAs) to remember and recover their original shape after large deformation offers vast potential for their integration in advanced engineering applications. SMAs can generate recoverable shape changes of several percent strain even when opposed by large stresses owing to reversible deformation mechanisms such as twinning and stress-induced martensite. For the most part, these alloys have been largely used in the biomedical industry but with limited application in other fields. This limitation arises from the complexities of prevailing microstructural mechanisms that lead to dimensional instabilities during repeated thermomechanical cycling. Most of these mechanisms are …

Virtual Motion Camouflage Based Nonlinear Constrained Optimal Trajectory Design Method, Gareth Basset

Electronic Theses and Dissertations

Nonlinear constrained optimal trajectory control is an important and fundamental area of research that continues to advance in numerous fields. Many attempts have been made to present new methods that can solve for optimal trajectories more efficiently or to improve the overall performance of existing techniques. This research presents a recently developed bio-inspired method called the Virtual Motion Camouflage (VMC) method that offers a means of quickly finding, within a defined but varying search space, the optimal trajectory that is equal or close to the optimal solution. The research starts with the polynomial-based VMC method, which works within a search …

Numerical Simulation Of Conventional Fuels And Biofuels Dispersion And Vaporization Process In Co-Flow And Cross-Flow Premixers, Xin Gu

Electronic Theses and Dissertations

In order to follow increasingly strict regulation of pollutant emissions, a new concept of Lean Premixed pre-vaporized (LPP) combustion has been proposed for turbines. In LPP combustion, controlled atomization, dispersion and vaporization of different types of liquid fuel in the premixer are the key factors required to stabilize the combustion process and improve the efficiency. A numerical study is conducted for the fundamental understanding of the liquid fuel dispersion and vaporization process in pre-mixers using both cross-flow and co-flow injection methods. First, the vaporization model is validated by comparing the numerical data to existing experiments of single droplet vaporization under …

Experimental Study And Modeling Of Mechanical Micro-Machining Of Particle Reinforced Heterogeneous Materials, Jian Liu

Electronic Theses and Dissertations

This study focuses on developing explicit analytical and numerical process models for mechanical micro-machining of heterogeneous materials. These models are used to select suitable process parameters for preparing and micro-machining of these advanced materials. The material system studied in this research is Magnesium Metal Matrix Composites (Mg-MMCs) reinforced with nano-sized and micro-sized silicon carbide (SiC) particles. This research is motivated by increasing demands of miniaturized components with high mechanical performance in various industries. Mg-MMCs become one of the best candidates due to its light weight, high strength, and high creep/wear resistance. However, the improved strength and abrasive nature of the …

Implementation And Performance Comparisons For The Crisfield And Stiff Arc Length Methods In Fea, Thomas W. Silvers

Electronic Theses and Dissertations

In Nonlinear Finite Element Analysis (FEA) applied to structures, displacements at which the tangent stiffness matrix KT becomes singular are called critical points, and correspond to instabilities such as buckling or elastoplastic softening (e.g., necking). Prior to the introduction of Arc Length Methods (ALMs), critical points posed severe computational challenges, which was unfortunate since behavior at instabilities is of great interest as a precursor to structural failure. The original ALM was shown to be capable in some circumstances of continued computation at critical points, but limited success and unattractive features of the formulation were noted and addressed in extensive subsequent …

Development And Validation Of Probabilistic Fatigue Models Containing Out-Life Suspensions, Noel S. Murray

Electronic Theses and Dissertations

Author's abstract: In the area of reliability engineering it is necessary to be confident that a component or system of components will not fail under use for safety and cost reasons. One major mechanism of failure to a mechanical component is fatigue. This is the repetitious motion of loading and unloading of the material, typically below the ultimate tensile strength of the material, which ultimately leads to a catastrophic failure. To ensure this does not happen, engineers design components based on tests to determine the life of these components. These tests are typically conducted on a bench type tester in …