Mechanical Engineering Commons^™

Flutter Stability Of Shrouded Turbomachinery Cascades With Nonlinear Frictional Damping, Alex Torkaman

Electronic Theses and Dissertations

Prediction of flutter in shrouded turbomachinery cascades is difficult due to i) coupling of aerodynamic drivers and structural dynamics of the cascade through shrouds, and ii) presence of nonlinear dry friction damping as a result of relative motion between adjacent shrouds. An analytical framework is developed in this dissertation to determine flutter stability of shrouded cascades with consideration of friction damping. This framework is an extension to the well-established energy method, and it includes all contributing factors affecting stability of the cascade such as aerodynamic excitation and the stabilizing effects of dry friction damping caused by nonlinear contact forces between …

A Localized Blended Rbf Collocation Method For Effective Shock Capturing, Michael Harris

Electronic Theses and Dissertations

Solving partial differential equations (PDEs) can require numerical methods, especially for non-linear problems and complex geometry. Common numerical methods used today are the finite difference method (FDM), finite element method (FEM) and the finite volume method (FVM). These methods require a mesh or grid before a solution is attempted. Developing the mesh can require expensive preprocessing time and the quality of the mesh can have major effects on the solution. In recent years, meshless methods have become a research interest due to the simplicity of using scattered data points. Many types of meshless methods exist stemming from the spectral or …

Investigation Of Oxy-Fuel Combustion Behind Reflected Shockwaves, Owen Pryor

Electronic Theses and Dissertations

Supercritical carbon dioxide has brought about new questions on the chemical kinetics of several small hydrocarbon fuels and the effects of carbon dioxide as the primary diluent on the different fuels. This report presents work on the ignition delay times and several species time-histories of methane, ethylene and syngas over a range of conditions. All experiments were conducted behind reflected shock waves using two different shock tubes. The ignition delay times were measured using a GaP photodetector to measure the emission of light. The species time-histories were measured using single laser spectroscopy. The effect of CO2 as a diluent on …

Bio-Inspired Visual Servo Control Of A Picking Mechanism In An Agricultural Ground Robot, Sinem Gozde Defterli

Electronic Theses and Dissertations

For a recently constructed disease detection agricultural ground robot, the segregation of unhealthy leaves from strawberry plants is a major task of the robot's manipulation subsystem in field operations. In this dissertation, the motion planning of a custom-designed picking mechanism in the ground robot's subsystem is studied in two sections. First, a set of analytical, suboptimal semi-analytical and numerical algorithms are studied to solve the inverse kinematics problem of the handling mechanism in firm circumstances. These premeditated approaches are built on the computation of the joint variables by an identified 3D position data of the target leaf only. The outcomes …

Investigation Of A Self-Powered Fontan Concept Using A Multiscale Computational Fluid-Structure Interaction Model, Kyle Beggs

Electronic Theses and Dissertations

Congenital Heart Disease (CHD) occurs in about 1\% (40,000) of newborn babies each year in the United States alone. About 10.9\% (960) of whom suffer from Hypoplastic Left Heart Syndrome (HLHS) - a subset of CHD where children are born with a single-ventricle (SV). A series of three surgeries are carried out to correct HLHS culminating in the Fontan procedure where venous flow returns passively to the lungs. The current configuration for the Fontan results in elevated Central Venous Pressure (CVP), inadequate ventricular preload, and elevated Pulmonary Vascular Resistance (PVR) leading to a barrage of disease. To alleviate these complications, …

Electrospray And Superlens Effect Of Microdroplets For Laser-Assisted Nanomanufacturing, Eduardo Castillo Orozco

Electronic Theses and Dissertations

Nanoparticles of various materials are known to exhibit excellent mechanical, chemical, electrical, and optical properties. However, it is difficult to deposit and transform nanoparticles into large two-dimensional and three-dimensional structures, such as thin films and discrete arrays. Electrospray technology and laser heating enable the deposition of these nanoparticles through the dual role of microdroplets as nanoparticle carriers and superlenses. The main goals of this dissertation are to delineate the electrospray modes, to achieve subwavelength focusing, and to enable a process for the deposition of nanoparticles into microlayers and discrete nanodots (a nanodot is a cluster of nanoparticles) on rigid and …

Detailed Understanding Of Flow, Heat Transfer, And Pressure Drop Behavior In A Square Channel With 45 Deg Ribs, Lumaya Ahmed

Electronic Theses and Dissertations

Internal Duct Cooling (IDC) with rib turbulators is one of the common cooling techniques applied inside the turbine airfoils. It is very important for the gas turbine industry to design and develop an optimized cooling channel that maximizes the amount of heat removed, while simultaneously minimizing the pressure drop for a target overall cooling effectiveness. Angled ribs perform superior to the transverse ribs due to additional secondary flow associated with them. However, they result in a highly non-homogenous heat transfer distribution, which is a manifestation of the complex, turbulent flow field inside the channel. It is very important to comprehend …

Brain Stethoscope: A Non-Invasive Method For Monitoring Intracranial Pressure, Md Khurshidul Azad

Electronic Theses and Dissertations

Monitoring intracranial pressure (ICP) is important for patients with increased intracranial pressure. Invasive methods of ICP monitoring include lumbar puncture manometry, which requires high precision, is costly, and can lead to complications. Non-invasive monitoring of ICP using tympanic membrane pulse (TMp) measurement can provide an alternative monitoring method that avoids such complications. In the current study, a piezo based sensor was designed, constructed and used to acquire TMp signals. The results showed that tympanic membrane waveform changed in morphology and amplitude with increased ICP, which was induced by changing subject position using a tilt table. In addition, the results suggest …

Energy Harvesting Nanocoated Piezoceramics For Low Power Systems, Quinten Humphrey

Electronic Theses and Dissertations

No abstract provided.

Numerical Study Of Interfacial Flow Using Algebraic Coupled Level Set-Volume Of Fluid (A-Clsvof) Method, Majid Haghshenas

Electronic Theses and Dissertations

Solving interfacial flows numerically has been a challenge due to the lack of sharpness and the presence of spurious currents at the interface. Two methods, Algebraic Coupled Level Set-Volume of Fluid (A-CLSVOF) method and Ghost Fluid Method (GFM) have been developed in the finite volume framework and employed in several interfacial flows such as Rayleigh-Taylor instability, rising bubble, impinging droplet and cross-flow oil plume. In the static droplet simulation, A-CLSVOF substantially reduces the spurious currents. The capillary wave relaxation shows that this method delivers results comparable to those of more rigorous methods such as Front Tracking methods for fine grids. …

Elastodynamic Model For Wind Induced Ground Motion, Mohammad Mohammadi

Electronic Theses and Dissertations

No abstract provided.

Biomechanical Characterization Of Video-Recorded Short-Distance Falls Involving Children Equipped With A Biometric Device: A Pilot Study., Bret A Hilt

Electronic Theses and Dissertations

Falls are commonly used as a false history by caregivers to conceal child abuse. Determining biomechanical compatibility is a key aspect in differentiating abuse from accident. Current forensic approaches are limited in assessing biomechanical compatibility of short-distance falls involving children due to a lack of reliable witnessed falls with known injury outcomes. The goals of this pilot study were to characterize biomechanical measures and to examine differences in biomechanical measures based on child and fall characteristics in reliable witnessed video-recorded falls involving children. The results of this study will serve as preliminary data for an on-going larger study with the …

Computational Modeling Of Transcatheter Aortic Valves, Mostafa Abbasi

Electronic Theses and Dissertations

Transcatheter aortic valve replacement (TAVR) is an established therapy alternative to surgical valve replacement in high-risk and intermediate-risk patients with severe aortic stenosis. Currently, although TAVR is an alternative and less-invasive treatment for high-risk and intermediate-risk patients, surgical aortic valves replacement (SAVR) was still considered as the gold standard for low-risk patients. TAVR could potentially be applied to lower-risk younger patients if the indications can be safely expanded to the patients and transcatheter aortic valve (TAV) long-term durability can match with that of surgical bioprostheses. In contrast to surgical aortic valves (SAVs), there have been limited clinical data on the …

Habitat Use Of Blacktip Sharks (Carcharhinus Limbatus) At Fishing Piers, Kelsey L. Spencer

Electronic Theses and Dissertations

Blacktip sharks (Carcharhinus limbatus) can be observed near fishing piers throughout the summer along the northeast coast of South Carolina. These piers attract and support a wide variety of potential prey and sharks are able to forage on fishers’ discards with minimal energetic cost. I tagged 12 blacktip sharks with acoustic transmitters, monitored piers with acoustic receivers, and conducted pier-creel surveys to determine the habitat use of blacktip sharks at fishing piers, factors that influenced residence time and presence/absence at piers, and any cyclical patterns in visits to piers. Data were analyzed with pier association indices (PAI), mixed models, and …

Fused Filament Fabrication 3d Printing Using Low-Melting Alloys., Nirupama Warrier

Electronic Theses and Dissertations

Fused Filament Fabrication (FFF) 3D printing technology has been a popular method of creating prototypes using plastics in the timeliest and most affordable manner for electronic, automotive, and biomedical applications. 3D printing of metals and alloys using FFF technology could provide low-cost alternatives and solutions to the Laser-Powder Bed Fusion Process (L-PBF) and Binder Jetting processes (BJ). In current work, low melting alloys have been used as a starting material and evaluated for FFF 3D printing using two methodologies. In the first methodology, Sn60Bi40 alloy in the form of wire was used as the feedstock for FFF extrusion and process …

Design, Analysis, And Application Of A Cellular Material/Structure Model For Metal Based Additive Manufacturing Process., Shanshan Zhang

Electronic Theses and Dissertations

Powder bed fusion additive manufacturing (PBF-AM) has been broadly utilized to fabricate lightweight cellular structures, which have promising potentials in many engineering applications such as biomedical prosthesis, aerospace, and architectural structures due to their high performance-to-weight ratios and unique property tailorabilities. To date, there is still a lack of adequate understanding of how the cellular materials are influenced by both the geometry designs and process parameters, which significantly hinders the effective design of cellular structures fabricated by PBF-AM for critical applications. This study aims to demonstrate a cellular structure design methodology that integrates geometrical design and process-material property designs. Utilizing …

Material Properties Design Using Simulations And Experiments For Powder Injection Molding Of Lead Zirconate Titanate (Pzt)., Bhushan Pramod Bandiwadekar

Electronic Theses and Dissertations

Powder injection molding (PIM) process simulations can be performed to minimize the number of injection molding experiments by estimating material properties necessary for PIM simulations. In current work, lead zirconate titanate (PZT) powder-polymer binder feedstock was compounded for 45 vol. % and 52 vol. % solids loading. PIM experiments on designed micro-pillar array geometry were performed using 52 vol. % PZT. Using PIM experiments results as basis, PIM simulations were performed on designed micro-pillar array geometries to understand the effectiveness of PIM simulations with the use of estimated feedstock properties in predicting molding behavior that have micro-features. Additionally, PIM simulations …

The Application Of Proper Orthogonal Decomposition To Numerically Modeled And Measured Ocean Surface Wave Fields Remotely Sensed By Radar, Andrew Joseph Kammerer

Electronic Theses and Dissertations

Phase-resolved ocean surface wave elevation maps provide important information for many scientific research areas (e.g., rogue waves, wave-current interactions, and wave evolution/growth) as well as for commercial and defense applications (e.g., naval and shipping operations). To produce these maps, measurements in both time and space are necessary. While conventional wave sensing techniques are limited spatially, marine radar has proven to be a complex yet promising remote sensing tool capable of providing both temporal and spatial wave measurements. The radar return from the sea surface is complex because it contains contributions from many sources only part of which provide information about …

Piezoelectric Bistable Buckled Beam Energy Harvester., Brian Edward Allgeier

Electronic Theses and Dissertations

A novel energy harvesting device design is presented to be created via microfabrication techniques. Such devices have countless applications for powering low-current electrical devices, especially wireless sensors or transmitters. This micro-electromechanical system (MEMS) design utilizes the piezoelectric response of a bistable buckled beam to gather electrical energy via ambient vibrations. While many traditional piezoelectric energy harvesters (PEH) consist of simple cantilever beam geometries, this nonlinear design utilizes inertial effects of torsional lever arms to actuate a central buckled beam to snap between its two stable states; such an abrupt strain on the piezoelectric beam potentially produces a significantly increased electrical …

Biomechanical Testing Of An Exercise For Strengthening The Proximal Femur., Alyssa Osbourne

Electronic Theses and Dissertations

Based on the principles of cutting edge bone remodeling research, a unique therapeutic exercise device was designed specifically to improve bone quality at the most critical location of the proximal femur prone to fracture: the superior-lateral femoral neck where the fracture first initiates during a fall. The exercise/device is intended to work by inducing enough strain in the bone to stimulate the body’s natural bone remodeling mechanisms to increase bone density in the proximal femur and consequently prevent a fracture from arising if a fall to the side does occur.

In order to test the proposed exercise, experiments simulating the …

Investigation Of Lattice Structures And Analysis Of Strut Geometry., Zachary D Denzik

Electronic Theses and Dissertations

This study involves the evaluation of lattice specimens fabricated using additive manufacturing as well as investigation of the influence of unit cell connection geometry. Lattice topologies of face-centered cells and body-centered cells were modeled, investigated using finite element analysis (FEA) for each specimen, manufactured using direct metal laser sintering (DMLS) with maraging steel powder, and mechanically tested. The strut diameter of each topology was altered to yield four different mass reductions from a solid cube, ranging from 55%-90% mass reduction. Three iterations of 1000mm³ lattice specimens were investigated. The first iteration consisted 0.5mm plates on the top and bottom …

The Development Of A Vacuum Forming System For Kydex® And Other Thermoplastic Sheet, Andrew G. Smith

Electronic Theses and Dissertations

Vacuum forming is a popular, cost effective method amongst large and small scale applications. The method is used to mold a material to the surface of a mold/pattern in order to create a negative copy for reproduction or an object in positive form. The prototype vacuum forming system developed and documented herein is of a membrane-seal type that consists of three (3) principle parts: radial platen, Hinged Frame and Platen Support Assembly, and a PVC surge tank. Each part is described in detail through design, manufacturing, and testing processes. The design supports functional versatility, small scale molding, and uses readily …

Development And Evaluation Of A Biocompatible Electroactive Sensor For Continuous Blood Pressure Measurement., Scott D. Cambron

Electronic Theses and Dissertations

Piezo-active composites have been implemented for sensing and transduction for decades. The 0-3 ceramic/polymer composite is one of the most common composite types used for sensing applications, owing to their tailorable properties of the two-phase composition, consisting of a three-dimensionally connected polymer/rubber matrix (inactive phase) with a dispersion of isolated piezo-ceramic particles (active phase). This thesis describes a method to develop novel biocompatible perivascular band comprised of a two-phase piezo-active composite to be fabricated using simple manufacturing processes. Biomaterials such as tissue scaffolds comprised of silk fibroin (SF) and chitosan (CS), and biocompatible soft rubbers will be implemented as the …

A Performance And Visualization Study On Inlet Geometries Of A Cross-Flow Fan., Yoel Tanquero

Electronic Theses and Dissertations

A study was conducted to characterize the flow-field in the suction region of different inlet geometries of a cross-flow fan. The characterization was accomplished by correlating the static performance curves measured for each fan-inlet configuration to the streamline plot obtained using a particle tracking velocimetry (PTV) measurement system at three constant flow rates (25, 40, and 55 CFM). The PTV measurement system used was developed by the author and uses helium bubbles as tracers, an LED light sheet, a slow motion camera, and a Matlab program. Four inlet geometry design variables were defined and independently studied to evaluate the effect …

Computational Study Of The Effect Of Interparticle Contact In Conductive Properties Of Random Particulate Systems, Dongfang Zhao

Electronic Theses and Dissertations

The effective conductivity of random particulate material system is computationally investigated using the Monte Carlo scheme and finite element method. A cubic system consisting of randomly-dispersed, equal-sized, deformable ellipsoids are modeled in this study. The steady-state conduction analysis along with a finite element analysis are performed to evaluate the electrical or thermal conductivity for the mechanical contact system. To represent more realistic material system, interfacial friction and gap conductance (or contact resistance) are included among the contacting particles. The Monte Carlo simulations are implemented to give a quantitative relationship between the effective conductivity and the inclusion volume fraction. Several parametric …

Variable Oxidation & Defects In Ti-6al-4v Material In Electron Beam Melting Additive Manufacturing, Edward Patton Clark

Electronic Theses and Dissertations

Powder-based metal in additive manufacturing (AM) is advantageous for rapid prototyping of parts and components, with the benefit of reusing powder to reduce production costs. A common driver in the aerospace industry is free-form complex geometries which can be created using CAD software to optimize specifications with strength-to-weight ratios in components. Weight optimization of aircraft components using additive manufacturing reduces material, which significantly reduces production cost in comparison to cast and wrought metallic products. Large biomedical and aerospace industries heavily invest in feedstock metal powders that have low density under structural stresses and high temperatures, resulting in superior resistance to …

Computational Fluid Dynamics Proof Of Concept And Analysis Of A Self-Powered Fontan Circulation, Marcus Ni

Electronic Theses and Dissertations

The Fontan circulation is a result of the last (third stage) surgical procedure to correct a single ventricle congenital cardiac disorder in children. Although the Fontan circulation has been successfully established in surgeries over the years, it is flawed and can lead in certain cases to pre-mature death. The main cause of this failure is due to increased pulmonary vascular resistance due to loss pulse pressure and blood flow. In healthy circulations, the heart pumps directly to the lungs, where as "Single Ventricle" patients must use a single sided heart to supply blood to the rest of the body before …

Ellipsometric Measurements Of Alternative Fuels, Leigh Nash

Electronic Theses and Dissertations

Alternative jet fuels will be important in the future to ensure cleaner burning, reliable, and reasonably priced air transportation. One important property that must meet certification standards is the fuel's thermal stability, or its ability to withstand heating before breaking down. Jet fuels are used as engine coolants, and thermally unstable fuels can form deposits in the fuel delivery systems, leading to a loss of fuel flow. In the past, the thermal stability of a fuel was rated using a color standard method. The color of the deposit left on a metal tube that had been heated and exposed to …

Chaotification As A Means Of Broadband Vibration Energy Harvesting With Piezoelectric Materials, Daniel Geiyer

Electronic Theses and Dissertations

Computing advances and component miniaturization in circuits coupled with stagnating battery technology have fueled growth in the development of high efficiency energy harvesters. Vibration-to-electricity energy harvesting techniques have been investigated extensively for use in sensors embedded in structures or in hard-to-reach locations like turbomachinery, surgical implants, and GPS animal trackers. Piezoelectric materials are commonly used in harvesters as they possess the ability to convert strain energy directly into electrical energy and can work concurrently as actuators for damping applications. The prototypical harvesting system places two piezoelectric patches on both sides of the location of maximum strain on a cantilever beam. …

Spatial And Temporal Compressive Sensing For Vibration-Based Monitoring: Fundamental Studies With Beam Vibrations, Vaahini Ganesan

Electronic Theses and Dissertations

Vibration data from mechanical systems carry important information that is useful for characterization and diagnosis. Standard approaches rely on continually streaming data at a fixed sampling frequency. For applications involving continuous monitoring, such as Structural Health Monitoring (SHM), such approaches result in high data volume and require powering sensors for prolonged duration. Furthermore, adequate spatial resolution, typically involves instrumenting structures with a large array of sensors. This research shows that applying Compressive Sensing (CS) can significantly reduce both the volume of data and number of sensors in vibration monitoring applications. Random sampling and the inherent sparsity of vibration signals in …