Mechanical Engineering Commons^™

Design And Analysis Of Robotically-Controlled Minimally Invasive Surgical Instruments, Jordan D. Tanner

Theses and Dissertations

Robot-assisted minimally invasive surgery is used to perform intricate surgical tasks through small incisions using long, slender instruments. The miniaturization of these instruments is advantageous to both surgeon and patient because smaller instruments reduce trauma to surrounding tissue, decrease patient recovery times, and can be used in confined spaces otherwise inaccessible using larger instruments. However, miniaturization of existing designs is limited by friction between moving parts, the volume occupied by the end effector, and manufacturing and assembly constraints. The objective of this work is to develop and analyze concepts that can be used in robot-assisted needlescopic surgery. The concepts are …

Application Of Variation Of Parameters To Solve Nonlinear Multimode Heat Transfer Problems, Travis J. Moore

Theses and Dissertations

The objective of this work is to apply the method of variation of parameters to various direct and inverse nonlinear, multimode heat transfer problems. An overview of the general method of variation of parameters is presented and applied to a simple example problem. The method is then used to obtain solutions to three specific extended surface heat transfer problems: 1. a radiating annular fin, 2. convective and radiative exchange between the surface of a continuously moving strip and its surroundings, and 3. convection from a fin with temperature-dependent thermal conductivity and variable cross-sectional area. The results for each of these …

Characterization Of Postural Tremor In Essential Tremor Using A Seven-Degree-Of-Freedom Model, Daniel William Geiger

Theses and Dissertations

Essential Tremor (ET), a condition characterized by postural and kinetic tremor in the upper limbs, is one of the most prevalent movement disorders. While pharmaceutical and surgical treatment options exist, they are not ideal. Assistive devices have the potential to provide relief to patients but are largely unexplored for ET. Furthermore, prior characterizations of essential tremor have focused on endpoint tremor and provide insufficient detail for designing such a device. We propose and demonstrate a novel method for characterizing essential tremor in the 7 proximal degrees of freedom (DOF) of the upper limb in various postures. In addition, we provide …

Co-Firing Biomass With Biogas In Cookstoves With A Fan, Manil Poudyal

Theses and Dissertations

Co-firing is a combustion process in which more than one type of fuel is used. In many cases, co-firing reduces fuel costs and/or reduces the environmental impact. The objective of this research was to test the hypothesis that adding biogas to be co-fired with biomass in a traditional cookstove reduces indoor air pollution and increases the combustion efficiency. The impact of co-firing on indoor air pollution is assessed by comparing the concentrations of carbon monoxide and particulate matter in the exhaust stream of a co-fired cookstove to a cookstove fueled with biomass alone. The concentrations of each of these pollutants …

Convective Heat Transfer With And Without Film Cooling In High Temperature, Fuel Rich And Lean Environments, Nathan K. Greiner

Theses and Dissertations

Modern turbine engines require high turbine inlet temperatures and pressures to maximize thermal efficiency. Increasing the turbine inlet temperature drives higher heat loads on the turbine surfaces. In addition, increasing pressure ratio increases the turbine coolant temperature such that the ability to remove heat decreases. As a result, highly effective external film cooling is required to reduce the heat transfer to turbine surfaces. Testing of film cooling on engine hardware at engine temperatures and pressures can be exceedingly difficult and expensive. Thus, modern studies of film cooling are often performed at near ambient conditions. However, these studies are missing an …

Piv Measurements Of Turbulent Flow In A Rectangular Channel Over Superhydrophobic Surfaces With Riblets, Richard Mark Perkins

Theses and Dissertations

In this thesis I investigate characteristics of turbulent flow in a channel where one of the walls has riblets, superhydrophobic microribs, or a hybrid surface with traditional riblets built on a superhydrophobic microrib surface. PIV measurements are used to find the velocity profile, the turbulent statistics, and shear stress profile in the rectangular channel with one wall having a structured test surface. Both riblets and superhydrophobic surfaces can each provide a reduction in the wall shear stress in a turbulent channel flow. Characterizing the features of the flow using particle image velocimetry (PIV) is the focus of this research. Superhydrophobicity …

A Method To Develop Neck Injury Criteria To Aid Design And Test Of Escape Systems Incorporating Helmet Mounted Displays, Jeffrey C. Parr

Theses and Dissertations

HMDs are becoming common human-machine interface equipment in manned military flight, but introducing this equipment into the overall aircraft escape system poses new and significant system design, development, and test concerns. Although HMDs add capabilities, which improve operator performance, the increased capability is often accompanied by increased head supported mass. The increased mass can amplify the risk of pilot neck injury during ejection when compared to lighter legacy helmets. Currently no adequate USAF neck injury criteria exist to effectively guide the requirements, design, and test of escape systems for pilots with HMDs. This research effort presents a novel method to …

Compliant Joints Suitable For Use As Surrogate Folds, Isaac L. Delimont

Theses and Dissertations

Origami-inspired design is an emerging field capable of producing compact and efficient designs. The object of a surrogate fold is to provide a fold-like motion in a non-paper material without undergoing yielding. Compliant mechanisms provide a means to achieve these objectives as large deflections are achieved. The purpose of this thesis is to present a summary of existing compliant joints suitable for use as surrogate folds. In doing so, motions are characterized which no existing compliant joint provides. A series of compliant joints is proposed which provides many of these motions. The possibility of patterning compliant joints to form an …

Thermal Analysis Of High Pressure Micro Plasma Discharge, Mostafa Mobli

Theses and Dissertations

High pressure micro plasma discharge has been at the center of interest in recent years, because of their vast applications, ease of access and cost efficiency. This attributes to atmospheric discharges that are generated in ambient conditions and therefore can be readily applicable to everyday use. The absence of vacuum makes these high pressure discharges to be inexpensive to operate. Despite the ease of operation, the high pressure is a source of enhanced gas heating as the gas temperature cannot be controlled by diffusion alone. Gas heating is therefore an important factor when it comes to the simulation of high …

Oxygen Flux And Dielectric Response Study Of Mixed Ionic-Electronic Conducting (Miec) Heterogeneous Functional Materials, Fazle Rabbi

Theses and Dissertations

Dense mixed ionic-electronic conducting (MIEC) membranes consisting of ionic conductive perovskite-type and/or fluorite-type oxides and high electronic conductive spinel type oxides, at elevated temperature can play a useful role in a number of energy conversion related systems including the solid oxide fuel cell (SOFC), oxygen separation and permeation membranes, partial oxidization membrane reactors for natural gas processing, high temperature electrolysis cells, and others. This study will investigate the impact of different heterogeneous characteristics of dual phase ionic and electronic conductive oxygen separation membranes on their transport mechanisms, in an attempt to develop a foundation for the rational design of such …

Investigation Of Thermal Performance Of Nanoparticle Enhanced Ionic Liquids (Neils) For Solar Collector Applications, Titan Chandra Paul

Theses and Dissertations

Concentrated Solar Power (CSP) is a prominent alternative energy technology, where mirrors or lenses are used to concentrate sunlight from a large area and stored in a collector filled with heat transfer fluid (HTF). The energy from this HTF is used to produce steam for power generation. CSP system requires high heat storage capacity and thermally stable HTF to reduce its operating cost. Having suitable thermophysical properties, ionic liquids (ILs) is considered as a potential HTF for the CSP applications; however thermophysical properties of ILs can be further enhanced by dispersing small volume percentages of nanoparticles. This liquid is called …

Dielectric Properties Of Composite Materials During Damage Accumulation And Fracture, Md. Rassel Raihan

Theses and Dissertations

Fiber reinforced polymer matrix composite materials have many unique properties and their high performance makes them available to use in many advanced technologies i.e. aerospace, microelectronics, and energy storage. There is a correlation that exists between the long term behavior of those materials under combined mechanical, thermal, and electrical fields, and the functional properties and characteristics of the composite materials that requires a fundamental understanding of the material state changes caused by deformation and damage accumulation. This will ultimately lead, for example, to the design and synthesis of optimal multifunctional material systems. Composite materials are heterogeneous and the complex morphology …

Ultrasonics Transduction In Metallic And Composite Structures For Structural Health Monitoring Using Extensional And Shear Horizontal Piezoelectric Wafer Active Sensors, Ayman Kamal Abdelrahman

Theses and Dissertations

Structural health monitoring (SHM) is crucial for monitoring structures performance, detecting the initiation of flaws and damages, and predicting structural life span. The dissertation emphasizes on developing analytical and numerical models for ultrasonics transduction between piezoelectric wafer active sensors (PWAS), and metallic and composite structures.

The first objective of this research is studying the power and energy transduction between PWAS and structure for the aim of optimizing guided waves mode tuning and PWAS electromechanical (E/M) impedance for power-efficient SHM systems. Analytical models for power and energy were developed based on exact Lamb wave solution with application on multimodal Lamb wave …

Structural Health Monitoring Using Linear And Nonlinear Ultrasonic Guided Waves, Yanfeng Shen

Theses and Dissertations

The dissertation addresses Structural Health Monitoring (SHM) using linear and nonlinear ultrasonic guided waves, with an emphasis on the development of analytical and numerical models of guided wave propagation and interaction with linear and nonlinear structural damage.

An analytical model was developed based on the exact Lamb wave solution for the simulation of Lamb wave propagation and interaction with damage. The damage effects were inserted into the model using complex valued wave damage interaction coefficients (WDICs). The analytical procedure was coded as a framework into a MATLAB Graphical User Interface (GUI), and the software WaveFormRevealer (WFR) was developed as a …

Plant-Biomimetic Hydrogel Actuators: Creating Movement In Hydrogels Through The Study Of Plants, Christen Rhodes

Theses and Dissertations

Plants are sessile organisms that have developed methods of movement to respond to environmental stimuli. Some of the approaches feature the unequal expansion of cells and controlling deformation direction through fibers under swelling and drying. Hydrogels are three dimensional polymer networks that have the capacity for large volume changes due their affinity for water and can be tough and/or stimuli-responsive. In this paper, three preliminary plant-biomimetic hydrogel actuator designs are discussed and tested from wet to dry. The first actuator design, termed a 1%-0.1% bilayer, features two layers of different swelling and drying rates due to differences in cross-linking density. …

Performance And Durability Of Electrodes With Platinum Catalysts In Polymer Electrolyte Cells Prepared By Ultrasonic Spray Deposition, William A. Rigdon

Theses and Dissertations

Catalysts in the electrodes of polymer electrolyte cells serve a critical function in reactions which can be used to either generate electrical energy from chemical fuels or convert electrical energy into chemicals. For low temperature electrochemical fuel cells, platinum is often utilized for its exceptional catalytic activities towards hydrogen oxidation and oxygen reduction reactions of the anode and cathode, respectively. However, the limited supply of platinum and high demand result in prohibitive costs plaguing commercialization of this technology. Therefore, minimal amounts of the catalyst should be used to achieve the maximum output to reduce expenses. Electrochemical behavior is governed by …

Conflict Management And Model Consistency In Multi-User Cad, Ammon Ikaika Hepworth

Theses and Dissertations

The NSF Center for e-Design, Brigham Young University (BYU) site has re-architected Computer Aided Design (CAD) tools, enabling multiple users to concurrently create, modify and view the same CAD part or assembly. This technology allows engineers, designers and manufacturing personnel to simultaneously contribute to the design of a part or assembly in real time,enabling parallel work environments within the CAD system. Multi-user systems are only as robust and efficient as their methods for managing conflicts and preserving model consistency. Conflicts occur in multi-user CAD when multiple users interoperate with the same or dependent geometry. Some conflicts can lead to model …

System Identification Of An Unmanned Tailsitter Aircraft, Nathan W. Edwards

Theses and Dissertations

The motivation for this research is the need to improve performance of the autonomous flight of a tailsitter UAV. Tailsitter aircraft combine the hovering and vertical take-off and landing capability of a rotorcraft with the long endurance flight capability of a fixed-wing aircraft. The particular aircraft used in this research is the V-Bat, a tailsitter UAV with a conventional wing and the propeller and control surfaces located within a ducted-fan tail assembly. This research focuses on identifying the models and parameters of the V-Bat in hover and level flight as a basis for the design of the control systems for …

Refinement And Characterization Of Synthetic Vocal Fold Models, Shelby Charisse Ward

Theses and Dissertations

Understanding vocal fold mechanics is an integral part of voice research and synthetic vocal fold models are an essential tool in characterizing vocal fold mechanics. These models contain multiple layers with varying stiffness, much like human vocal folds. The purpose of this thesis is to improve the current models and modeling techniques, as well as investigate the impact of asymmetry on model vibration. A new design for an MRI-based model is detailed. This model has a more realistic geometry than the simplified models and mimics some of the vibratory characteristics observed in human vocal folds. The MRI-based model was used …

Analysis And Compression Of Large Cfd Data Sets Using Proper Orthogonal Decomposition, Trevor Jon Blanc

Theses and Dissertations

Efficient analysis and storage of data is an integral but often challenging task when working with computation fluid dynamics mainly due to the amount of data it can output. Methods centered around the proper orthogonal decomposition were used to analyze, compress, and model various simulation cases. Two different high-fidelity, time-accurate turbomachinery simulations were investigated to show various applications of the analysis techniques. The first turbomachinery example was used to illustrate the extraction of turbulent coherent structures such as traversing shocks, vortex shedding, and wake variation from deswirler and rotor blade passages. Using only the most dominant modes, flow fields were …

Development Of A Complex Synthetic Larynx Model And Characterization Of The Supraglottal Jet, Jayrin Ella Seegmiller

Theses and Dissertations

Voice is an important tool for communication. Consequently, voice disorders tend to severely diminish quality of life. Voice research seeks to understand the physics that govern voice production to improve treatment of voice disorders. This thesis develops a method for creating complex synthetic laryngeal models and obtaining flow data within these complex models. The method uses Computed Tomography (CT) scan data to create silicone models of the larynx. Index of refraction matching allows flow field data to be collected within a synthetic complex larynx, which had previously been impossible. A short proof-of-concept of the method is set forth. Details on …

Automated Landing Site Determination For Unmanned Rotocraft Surveillance Applications, Justin Keith Mackay

Theses and Dissertations

Unmanned air vehicles have been increasing in their autonomous capabilities. This research furthers these capabilities by focusing on the automation of landing site determination for rotorcraft in urban environments. Automated landing saves energy and allows the aircraft to choose areas that are safe for people and the aircraft. Two methods are used to gather information about the terrain of potential landing sites. One method is 3D reconstruction from multiple camera images. The other method uses a range sensor to reconstruct the terrain. Both of these methods create an inertial terrain map of the environment in the form of a point …

Elastic Energy Absorption Via Compliant Corrugations, Sean S. Tolman

Theses and Dissertations

Elastic absorption of kinetic energy and distribution of impact forces are required in many applications. This may be achieved through the use of compliant corrugations. An innovative padding concept is investigated for such applications. Also, recent attention given to the potential for using origami in engineering applications may provide new corrugation configurations that are advantageous for energy absorption and force distribution. This work explores three areas related to these concepts.First, the parameters of a compliant, corrugated padding concept are investigated using Finite Element Analyses (FEA) and physical testing. The shape of the corrugation cross section is explored as well as …

A Computational Hybrid Method For Self-Intersection Free Offsetting Of Cad Geometry, Garrett Clark Bodily

Theses and Dissertations

Surface offsetting is a valuable tool used in Computer Aided Design (CAD). An offset surface is a collection of points that are at a constant distance from another surface. An offset surface is created in CAD by selecting a surface and then specifying the distance that the surface is to be offset. If a surface is selected and a distance of D is specified, then the resulting offset surface should always be distance D from the original surface. The surface offset tool can be used for many applications. Modeling of composites or other layered manufacturing processes rely heavily on offset …

Articulated Spine For A Robot To Assist Children With Autism, Brandon M. Norton

Theses and Dissertations

Autism spectrum disorder (ASD) affects about 1.5 million individuals in the US alone. The consequences of ASD affect families, caregivers, and social structures. This thesis adds to a growing group of people performing research on mitigating the effects of autism through robotics. Children with ASD tend to interact with robots more easily than with other humans. The goal of robotic therapy is not to help children interact with robots, but to generalize the behavior to humans. An articulated spine is a key to human emotional expression through shaping, weight shifting, and flow. Despite this importance, this feature is all but …

Minimization Of The Effects Of Secondary Reactions On Turbine Film Cooling In A Fuel Rich Environment, Andrew T. Shewhart

Theses and Dissertations

The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow and augmented heat transfer to the blade arises. This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream …

A Study Of Slipper And Rail Wear Interaction At Low Speed, Greg V. Cavallaro

Theses and Dissertations

The wear research presented in the work consists of results gathered from adapting a FEM based on a Holloman High Speed Test Track (HHSTT) mission executed in January 2008. The FEM consists of a VascoMax slipper sliding on a stationary AISI-1080 steel rail. The slipper is slid along the rail at speeds of 20 m/s and 40 m/s with complementary vertical velocities of -0.079 m/s and -0.059 m/s, respectively. The surface roughness caused by features such as asperities and valleys of the materials, is simulated in this model by five asperities, 1 micron to 5 microns on the rail and …

Characterization And Optimization Of Thermal Protective Fabrics Designed To Protect Against Splash Hazards, Jeremy Osguthorpe

Theses and Dissertations

Thermal textiles used in Personal Protective Equipment (PPE) are used to protect individuals from the hazards of thermal energy. An analytical model of the diffusion of thermal energy within the fabric was developed to simulate the transfer of thermal energy due to a hot liquid splash. Based on the model results, it was determined that that the use of an orthotropic material in which the thermal conductivities in the radial and axial directions are different can be used to decrease the amount of heat transferred through the fabric and thereby increase amount of protection in PPE. An orthotropic material particularly …

Microstructural Factors Of Strain Delocalization In Model Metallic Glass Matrix Composites, Thomas James Hardin

Theses and Dissertations

Metallic glass matrix composites have enormous potential stemming from the interplay between crystalline and amorphous phases. This work models such a composite using shear transformation zone dynamics (a modified kinetic Monte Carlo method) for the amorphous phase, and a local Taylor dislocation model for the crystalline phase. An N-factorial experiment using the model is presented examining the effects of crystalline volume fraction, microstructure length scale, and yield stress of the crystalline phase. Each replicate is analyzed for maximum stress, maximum strain, strain energy dissipation, strain localization, and strain partitioning between phases. Regression analysis is used to identify statistically-significant trends in …

Validation Of A Modified Version Of Overflow 2.2 For Use With Turbomachinery Under Clean And Total Pressure Distorted Conditions And A Study Of Blade Loading In Distortion, Matthew L. Marshall

Theses and Dissertations

Inlet distortion is an important consideration in fan performance. Distortion can be generated through flight conditions and airframe-engine interfaces. The focus of this paper is a series of high-fidelity, time-accurate Computational Fluid Dynamics (CFD) simulations of a multistage fan, investigating distortion transfer, distortion generation, and the underlying flow physics under different operating conditions. The simulations are full annulus and include 3 stages and the inlet guide vane (IGV). The code used to carry out these simulations is a modified version of Overflow2.2 that was developed as part of the Computational Research and Engineering Acquisition Tools and Environment (CREATE) program. The …