Engineering Science and Materials Commons^™

Numerical Simulation Of Separating Flows Using Computational Models Based On The Vorticity Confinement Method, Lesong Wang

Doctoral Dissertations

The objective of the present research is to investigate the recent development of the vorticity confinement method. First, a new formulation of the vorticity confinement term is studied. Advantages of the new formulation over the original one include the ability to conserve the momentum, and the ability to preserve the centroid motion of some flow properties such as the vorticity magnitude. Next, new difference schemes, which are simpler and more efficient than the old schemes, are discussed. At last, two computational models based on the vorticity confinement method are investigated. One of the models is devised to simulate inviscid flows …

Directional Solidification, Microstructures And Mechanical Properties Of Cr-Cr3si Eutectic Alloys, Hongbin Bei

Doctoral Dissertations

Alloys based on intermetallics have been considered for high temperature structural applications. However, many of these alloys suffer from intrinsic brittleness and low fracture toughness at ambient temperature. Therefore, ductile-phase-toughened intermetallic composites are being investigated as a means to improve the fracture toughness. A subset of this class of materials is in-situ composites produced by directional solidification of intermetallic eutectics. In this study, the Cr-Cr₃Si eutectic system is selected as a model system to investigate composites by directional solidification, where the strong, but brittle Cr₃Si is combined with a more ductile Cr-rich solid solution.

A series …

Mechanical Properties And Corrosion Resistance Of Ni-Sic Nano Composite Coatings On 2024-T3 Aluminum, Amit Jain

Masters Theses

Coatings of nickel with and without silicon carbide nano-particles were carried out on 2024-T3 aluminum alloy by the electrochemical process. The size of the silicon carbide particles was less than 50nm. Nickel coatings were done using a nickel sulfamate bath maintained at a constant temperature of 50° ± 5° C. Tensile specimens were prepared and studied to determine the Young's modulus of bare aluminum, with nickel coatings and with composite nickel and silicon carbide coatings. Wear samples of 1 inch² (6.45cm²) were prepared and studied for wear resistance. The residual stress measurements were done by the hole …

Effect Of Loading Frequency On Intervertebral Disc Cells., Kristen Nicole Loveless

Masters Theses

Cells of the intervertebral disc have a limited capacity for matrix repair and may contribute to the onset and progression of degenerative disc changes. Disc degeneration contributes to declining nutrition, loss of viable cells, cell senescence, post-translational modification of matrix proteins, accumulation of degraded matrix molecules, and fatigue failure of the matrix. During daily activities intervertebral discs are exposed to oscillatory hydrostatic loads. It is known that dynamic loads with critical frequencies close to that of the human spine resonant frequency (4-8 Hz) have a destructive effect on disc tissue properties. Whether this destructive effect is purely mechanical due to …

Modeling Of Circulation Zone And Shear Layers In Coaxial Injectors, Clayton Andrew White

Masters Theses

Gaseous/gaseous hydrogen oxygen shear coaxial injectors were modeled to investigate grid parameters affecting solution and to determine if a steady state solution might exist if only one circulation zone was present. The General Equation Mesh Solver (GEMS), which implements the Reynolds Averaged Navier-Stokes equations with the k-ω turbulence model, was used to conduct the study. The Gambit grid generator was used to construct computational grids. Different grids were compared in a search for the optimum configuration while residual levels were monitored in search of a steady state solution.

Chemical Kinetics And Thermal Hydraulics Of Lead Bismuth Flow Loops, Kanthi Kiran Dasika

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of the thesis is to study the effect of chemical kinetics and thermal hydraulics of Lead Bismuth Eutectic (LBE) flow in the Materials Test Loop (MTL). The Materials Test Loop, also known as the Delta Loop, was built in Los Alamos National Laboratories (LANL) to obtain the experimental data for corrosion estimation and analysis. It is a well-known fact that corrosion plays an important role in the design of nuclear thermal hydraulic systems. Since the MTL is a multi-section closed system that differs in diameter from one part to another, an intensive study on the overall and regional …

The Development And Verification Of Three Matlab Analysis Applications Programmed Specifically For Engage Team Projects., Jonathan W. Huber

Masters Theses

This thesis outlines the development of three analysis applications for use in the freshmen Engineering Fundamentals Program (engage) at the University of Tennessee. Engage teaches freshmen engineering mechanics concepts through a set of integrated components including Lecture, Analysis and Skills, Problem Session, Physical Homework, and Team Projects. Presently, the students have limited access to any software analysis tools to aid the design process. The students have little experience writing the types of complex programs needed to analyze a particular project. Even more, they do not have the time. The applications provide a means for the students to perform an accurate …

A Study On The Prediction Of Viscosity With The Use Of Numerical Simulation Software, Brian Robinson

Masters Theses

A study was undertaken to numerically simulate the flow of highly viscous fluid. Simulating a highly viscous flow within a parallel plate plastometer will hopefully begin to bridge the gaps in the current knowledge of these viscous models. The modeling of this flow was performed using the canned code FiDAP from Fluent Inc. The results are compared with the analytical results calculated by NASA Marshall researchers.

Study Of Geometric Effects On Local Corrosion Rates For Lbe Loop, Chao Wu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Corrosion is an extremely important issue in nuclear cooling system applications. Many scientific and engineering efforts have been contributed to the research of finding an ideal material, which has resistance to corrosive Lead Bismuth Eutectic (LBE). A Delta Loop was designed and constructed in Los Alamos National Lab (LANL) to obtain the experimental data. This loop is a multi-section closed system that differs in diameter from one part to another. As a result, an intensive study on the geometry effect is hence necessary and valuable. In this thesis, this problem was simulated by commercial software STAR-CD. Results provide a good …

Utilization Of Municipal Solid Waste Rejects In The Production Of A Recycled Plastic Waste Composite Material, Mohamed Kamal Abou Khatwa

Archived Theses and Dissertations

The solid waste disposal problem has grown significantly in the last decades imposing a lot of pressure on disposal and treatment acts. In the past, incineration and landfilling were the common methods for disposing of products of municipal solid waste. With the increasing volumes of waste generation and the legislative restrictions of these treatment methods, reuse of bulk waste is foreseen as the best alternative to disposal. Due to the current widespread use of plastic products in daily life, post consumer plastics now contribute significantly to municipal solid waste generation rates with a contradicting low participation in waste minimization practices. …

A Study Of The Electron Beam Scattering Under Various Gaseous Environment, Jing He

Masters Theses

There are three objectives in this work: to experimentally measure the profiles of electron beams scattered by interaction with a gas, to measure total scattering cross-sections for gases and to apply the cross-section data in a suitable Monte Carlo simulation to predict beam scattering profiles for comparison with experiment.
The experimentally measured profiles cover a wide range of intensity variation. There are two evidenced regions: an inner region and an outer skirt corresponding to inelastic (small angle) and elastic scattering respectively are appeared. These profiles use the planar p-n junction gives us an overall look at the electron beam spreading, …

Fuzzy System Identification Based Upon A Novel Approach To Nonlinear Optimization, Raymond Scott Starsman

Electrical & Computer Engineering Theses & Dissertations

Fuzzy systems are often used to model the behavior of nonlinear dynamical systems in process control industries because the model is linguistic in nature, uses a natural-language rule set, and because they can be included in control laws that meet the design goals. However, because the rigorous study of fuzzy logic is relatively recent, there is a shortage of well-defined and understood mechanisms for the design of a fuzzy system. One of the greatest challenges in fuzzy modeling is to determine a suitable structure, parameters, and rules that minimize an appropriately chosen error between the fuzzy system, a mathematical model, …

Experimental And Computational Failure Analysis Of Graphite/Bismaleimide Laminated Composite And Carbon Foam In Sandwich Construction, Troy C. Welker

Theses and Dissertations

Sandwich beams consisting of a carbon foam core and graphite/bismaleimide face sheets were constructed and tested. Nine specimens were fabricated using three distinct cross-ply symmetric face sheet layups with a constant core thickness. Four-point bend testing controlled by a constant rate of midspan vertical displacement was used to load the specimens to failure. Displacements and strains from the experiment were compared to analytical sandwich beam theory and displacements and failure loads were compared to a layerwise finite element solution. A phenomenological failure criterion was developed that compares favorably with experimental failure data. The finite element solution gives failure within an …

Stress Analysis Of Silicon Carbide Microeletromechanical Systems Using Raman Spectroscopy, Stanley J. Ness

Theses and Dissertations

During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Government and industry are looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to analyze poly-silicon MEMS devices made with the Multi-User MEMS Process (MUMPS trade name). Micro-Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. …

Reduction Of Thermal Residual Strains In Adhesively Bonded Composite Repairs, Heather R. Crooks

Theses and Dissertations

Many military and commercial aircraft are being called upon to fly well beyond their original intended service lives. This has forced the United States Air Force (USAF) to increasingly rely on structural repairs to address fatigue induced damage and to extend aircraft useful life. The focus of this research is the use of a high-strength composite patch technique to repair a fatigue crack on an aluminum aircraft structure. This study investigates the thermal residual strains that occur as a direct result of the coefficient of thermal expansion (CTE) mismatch between the repair patch and the underlying cracked metallic structure to …

The Effect Of A Hard Coating On The Damping And Fatigue Life Of Titanium, Frank T. Ivancic

Theses and Dissertations

This project compares the damping and fatigue life of bare titanium plates to those coated with magnesium aluminate spinel (mag spinel). Two different coating thicknesses were tested: .005" per side and .010" per side (total thicknesses of .010" and .020"). Dynamic ping tests were conducted on all specimens to determine their resonance frequencies. Laser vibrometry was used to determine the mode at each resonance frequency. Damping ratios were determined through the use of sine sweeps. A vibration mode was selected at which to fatigue the specimens, and the stress pattern was analyzed utilizing the Stress Pattern Analysis by Thermal Emissions …

Characterization Of Syntactic Foams And Their Sandwich Composites: Modeling And Experimental Approaches, Nikhil Gupta

LSU Doctoral Dissertations

Hollow particle filled polymers known as syntactic foams are lightweight and highly damage tolerant. Syntactic foams are used as core materials in sandwich composites. The use of such materials in aeronautical and space structures make it necessary to understand their characteristics for various environmental and loading conditions. The first part of the present work takes modeling and finite element analysis approach to understand and predict the deformation behavior of syntactic foams. Contact analysis is performed on single particle models by the finite element analysis approach. In the second part extensive experiments are carried out to characterize syntactic foams for hygrothermal …

Freeway Accident Analysis Using Second Order Statistics, Khasim Khasimul Shaik

LSU Master's Theses

This research focuses on the use of historical freeway traffic data for comparison of the precursory traffic conditions to that accident occurrence by using 15-minute traffic speed contour maps. The second order statistics measures, namely angular second moment (ASM), contrast and entropy were used as the traffic performance measures in order to compare the two situations. The data used is from I-4 freeway traffic condition database, stored in a SQL server and 1999 year accident database for the same I-4 freeway. The study section is located in Orlando, Florida. The approach shows an approach to understand the performance of the …

Progressive Fatigue Effects On Manual Lifting Factors, Anthony D'Wayne Banks

LSU Doctoral Dissertations

Much evidence suggests that the cause of lower back pain (LBP) and injury is frequently related to the posture of lifting, the load, muscle fatigue, and other factors. The purpose of this study was to evaluate the effect of progressive fatigue on factors that have previously been associated with increased risk of LBP in various occupational settings, during a repetitive lifting task where freestyle lifting technique was utilized. A laboratory experiment was conducted to evaluate several fatigue analysis, electromyography amplitude, kinematic, and kinetic parameters of repetitive freestyle lifting during a 2-hour lifting period. Each of ten (10) young adult male …

Block-Level Discrete Cosine Transform Coefficients For Autonomic Face Recognition, Willie L. Scott, Ii

LSU Doctoral Dissertations

This dissertation presents a novel method of autonomic face recognition based on the recently proposed biologically plausible network of networks (NoN) model of information processing. The NoN model is based on locally parallel and globally coordinated transformations. In the NoN architecture, the neurons or computational units form distributed networks, which themselves link to form larger networks. In the general case, an n-level hierarchy of nested distributed networks is constructed. This models the structures in the cerebral cortex described by Mountcastle and the architecture based on that proposed for information processing by Sutton. In the implementation proposed in the dissertation, the …

Rotary Kiln Incineration Of Hazardous Wastes: Pilot-Scale Studies At Louisiana State University, John Sutherland Earle

LSU Doctoral Dissertations

Studies of incineration of surrogates for hazardous wastes are conducted in the pilot-scale rotary kiln incinerator (RKI) at Louisiana State University (LSU) in Baton Rouge, Louisiana. The purpose of the research is to investigate methods of treating and destroying hazardous wastes in a cost-effective and environmentally sound way. The objective is to provide process data that will contribute to increased knowledge for RKI design and operation. The LSU facility is a College of Engineering Combustion Laboratory that is unique in its large size as a university laboratory. It is equipped with individual instruments for analysis of O₂, CO, …

High Strain Rate Properties Of Polymer Matrix Composites, Amol Jadhav

LSU Master's Theses

The vast differences in strength, ultimate strain and modulus during high strain rate (HSR) deformation of materials have been a very long-standing subject of engineering interest. This thesis deals with characterization of mechanical properties of two composite materials, balanced angle-ply graphite epoxy laminates (fibrous composite) and syntactic foams (particulate composite). The focus of this study is to compare the mechanical properties of these composite materials at high strain rates and quasi-static conditions and to find out the effects of failure modes on HSR mechanical properties of these materials. Split Hopkinson Pressure Bar (SHPB) apparatus is used for the HSR testing …

Synthesis, Structure And Properties Of Nanolayered Dlc/Dlc Films, Pankaj Gupta

LSU Master's Theses

Diamondlike carbon (DLC) films have been explored extensively in the past due to their highly attractive properties. However, the high level of internal stress developed during growth prevents deposition of thick films. Synthesis of DLC/DLC multilayers (DDM) presents a venue to overcome this drawback. In the present study, DLC films and DDM were deposited on Si substrate using dc plasma of CH₄ and Ar gas mixture. FTIR was used to analyze the structure of the DLC films. Mechanical properties of the films were characterized by microhardness testing and nanoindentation. The tribological properties were studied by conducting pin-on-disc experiments in …

Tensile Strength And Bonding Characteristics Of Self-Compacting Concrete, Cristian Druta

LSU Master's Theses

Self-compacting concrete, also referred to as self-consolidating concrete, is able to flow and consolidate under its own weight and is deaerated almost completely while flowing in the formwork. It is cohesive enough to fill the spaces of almost any size and shape without segregation or bleeding. This makes SCC particularly useful wherever placing is difficult, such as in heavily-reinforced concrete members or in complicated workforms. The objectives of this research were to compare the Splitting Tensile Strength and Compressive Strength values of self-compacting and normal concrete specimens and to examine the bonding between the coarse aggregate and the cement paste …

Developing A Methodology To Detect Partial Failures For Dynamic Systems, Anwar A. Al-Jowder

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this research is to develop a decision support system that can assist in detecting partial failures in dynamic systems such as Fire Control System Tracking Radar (TR) onboard Naval Ships. Partial failures do not necessarily shut down the system immediately but cause degradation of operational performance. Previous work has shown that experts in the field of failure detection, test point insertion and Built-In-Test Equipment (BITE) can provide useful input in detecting partial failures. Partial failures affect operational system performance and support costs, which can be significant. Often, however, partial failure detection consists of the estimations and opinions …

Finite-Horizon Operations Planning For A Lean Supply Chain System, Ahmad Diponegoro

LSU Doctoral Dissertations

This dissertation studies an operational policy for a lean supply chain system consisting of a manufacturer, multiple suppliers and multiple buyers. The manufacturer procures raw materials from the suppliers and converts them into finished products, which are then shipped in batches to the buyers at certain intervals of times. Three distinct but inseparable problems are addressed: single supplier and single buyer with fixed delivery size (FD), multiple suppliers and multiple buyers with individual delivery schedule (MD), and time dependent delivery quantity with trend demand (TD). The mathematical formulations of these supply systems are categorized as mixed-integer, nonlinear programming problems (MINLAP) …

Optimization And Automation Of A Thermal Oyster Shucking Process, Daniel Edgar Martin

LSU Doctoral Dissertations

Louisiana Gulf Coast oysters (Crassostrea virginica) were subjected to thermal shucking treatments to effect adductor muscle release from both left and right valves. The oysters were instrumented with thermocouples to monitor and record process temperatures in the oysters and on the shell. Following treatment, the oysters were evaluated for relaxation and release of the adductor muscle, meat quality and texture, and for the effect of the treatments on the storage life of the oysters as measured by total microbial plate counts. The treatments of many oysters resulted in a complete release of the adductor muscle from the shell while maintaining …