Engineering Science and Materials Commons^™

Solving The Partial Differential Equation Of Vibrations With Interval Parameters Using The Interval Finite Difference Method, Brenda G. Medina

Open Access Theses & Dissertations

Accuracy and efficiency are among the main factors that drive today's innovative disciplines. As technology rapidly advances, efficiency takes on new meanings but what about accuracy? How accurate is accurate? Human error, uncertainties in measurement, and rounding errors are just some causes of inaccuracy. Interval Computations is an area that allows for such issues to be taken into account; for each measurement attained (for example), an interval can be built by considering the error associated with the measurement, and such an interval can be utilized in the mathematical computations of interest.

We consider the partial differential equation (PDE) of vibrations …

Dispersive Wave Equations For Solids With Microstructure, A. Berezovski, Juri Engelbrecht, Mihhail Berezovski

Publications

The dispersive wave motion in solids with microstructure is considered in the one-dimensional setting in order to understand better the mechanism of dispersion. It is shown that the variety of dispersive wave propagation models derived by homogenization, continualisation, and generalization of continuum mechanics can be unified in the framework of dual internal variables theory.

Calibration Of Alumina-Epoxy Nanocomposites Using Piezospectroscopy For The Development Of Stress-Sensing Adhesives, Amanda L. Stevenson

Electronic Theses and Dissertations

A non-invasive method to quantify the stress distribution in polymer-based materials is presented through the piezospectroscopic calibration of alumina-epoxy nanocomposites. Three different alumina volume fraction nanocomposites were created and loaded under uniaxial compression in order to determine the relationship between applied stress and the frequency shift of the R-lines produced by alumina under excitation. Quantitative values for six piezospectroscopic coefficients were obtained which represent the stress-sensing property of the nanocomposites. The results were applied to an alumina-filled adhesive in a single lap shear configuration demonstrating the capability of the technique to monitor R-line peak positions with high spatial resolution and …

Polymer Based Microfabrication And Its Applications In Optical Mems And Biomems, Guocheng Shao

LSU Doctoral Dissertations

Due to its ease of fabrication, low cost and great variety of functionalities, polymer has become an important material in microfabrication. MEMS devices with polymer as the structure material have found applications in various fields, especially in BioMEMS and optical MEMS. In this dissertation, three polymer based microfabricated devices/components have been developed and tested. Various polymer based fabrication techniques, such as high aspect ratio SU-8 photolithography, three dimensional polydimethylsiloxane (PDMS) soft lithography, multi-layer soft lithography and PDMS double casting technique have been developed/studied and employed in the device fabrication process. The main contribution of this dissertation includes: (1) Developed two …

Effects Of Silicon Content And Cooling Rate On Mechanical Properties Of Heavy Section Ductile Cast Iron , Meghan Haycock

Dissertations, Master's Theses and Master's Reports - Open

The effects of Si and cooling rate are investigated for their effect on the mechanical properties and microstructure. Three alloys were chosen with varying C and Si contents and an attempt to keep the remainder of the elements present constant. Within each heat, three test blocks were poured. Two blocks had chills – one with a fluid flowing through it to cool it (active chill) and one without the fluid (passive) – and the third block did not have a chill. Cooling curves were gathered and analyzed. The mechanical properties of the castings were correlated to the microstructure, cooling rate …

Processing And Mechanical Properties Of Cast Aluminum Containing Scandium, Zirconium, And Ytterbium , Nicholas D. Johnson

Dissertations, Master's Theses and Master's Reports - Open

A series of aluminum alloys containing additions of scandium, zirconium, and ytterbium were cast to evaluate the effect of partial ytterbium substitution for scandium on tensile behavior. Due to the high price of scandium, a crucible-melt interaction study was performed to ensure no scandium was lost in graphite, alumina, magnesia, or zirconia crucibles after holding a liquid Al-Sc master alloy for 8 hours at 900 °C in an argon atmosphere. The alloys were subjected to an isochronal aging treatment and tested for conductivity and Vickers microhardness after each increment. For scandium-containing alloys, peak hardnesses of 520-790 MPa, and peak tensile …

High Temperature, Low Cycle Fatigue Of A Hybrid Particulate/Fiber Aluminum Metal-Matrix Composite , Justin Clark

Dissertations, Master's Theses and Master's Reports - Open

The effect of shot particles on the high temperature, low cycle fatigue of a hybrid fiber/particulate metal-matrix composite (MMC) was studied. Two hybrid composites with the general composition A356/35%SiC particle/5%Fiber (one without shot) were tested. It was found that shot particles acting as stress concentrators had little effect on the fatigue performance. It appears that fibers with a high silica content were more likely to debond from the matrix. Final failure of the composite was found to occur preferentially in the matrix. SiC particles fracture progressively during fatigue testing, leading to higher stress in the matrix, and final failure by …

The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, Robert L. Ash, Irfan Zardadkhan, Allan J. Zuckerwar

Mechanical & Aerospace Engineering Faculty Publications

Governing equations including the effects of pressure relaxation have been utilized to study an incompressible, steady-state viscous axial vortex with specified far-field circulation. When sound generation is attributed to a velocity gradient tensor-pressure gradient product, the modified conservation of momentum equations that result yield an exact solution for a steady, incompressible axial vortex. The vortex velocity profile has been shown to closely approximate experimental vortex measurements in air and water over a wide range of circulation-based Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and …

Fundamental Studies Of Co-Base Superalloy Biomedical Prototypes Fabricated By Electron Beam Melting: Microstructures And Microstructural Architecture, Sara M. Gaytan

Open Access Theses & Dissertations

Rapid prototyping, especially electron beam melting (EBM) technology by ARCAM have proven to provide outstanding microstructural and mechanical properties on different alloys fabricated by this technology. Being a computer designed driven technology, complex components, that are hard or even impossible to fabricate by traditional manufacturing techniques, can be fabricated by layer-by-layer EBM technology.

Microstructural and mechanical properties are compared for an EBM femoral knee component prototype with a traditionally-fabricated and body-removed femoral knee implant. Block and cylindrical shape components fabricated by EBM were also analyzed for this project. The alloy utilized for these components is Co-26Cr-6Mo-0.2C characterized by the standards …

Ballistic Projectile Metallurgical Issues And Fundamentals: Aerosol Production In Rod Penetration Erosion And Erosion Phenomena Associated With Railgun Development, Brenda Ivette Machado

Open Access Theses & Dissertations

The issue is derived from ballistic erosion as it relates to nanoparticle production and respiration of these particles as a health concern ballistic erosion and ballistic erosion as it relates to railgun performance. A common thread between these two issues is dynamic recrystallization (DRX). DRX has been demonstrated to be the dominant mechanism for solid-state flow associated with ballistic projectile/target penetration and interaction, friction-stir welding phenomena, and other high-strain rate deformation phenomena.

Aerosol particulates collected on filters from ballistic penetration and erosion events for W-Ni-Co and W-Ni-Fe kinetic energy rod projectiles penetrating steel target plates were observed to be highly …

Microstructural Architecture Developed In The Fabrication Of Solid And Open-Cellular Copper Components By Additive Manufacturing Using Electron Beam Melting, Diana Alejandra Ramirez

Open Access Theses & Dissertations

The fabrication of Cu components were first built by additive manufacturing using electron beam melting (EBM) from low-purity, atomized Cu powder containing a high density of Cu2O precipitates leading to a novel example of precipitate-dislocation architecture. These microstructures exhibit cell-like arrays (1-3µm) in the horizontal reference plane perpendicular to the build direction with columnar-like arrays extending from ~12 to >60 µm in length and corresponding spatial dimensions of 1-3 µm. These observations were observed by the use of optical metallography, and scanning and transmission electron microscopy. The hardness measurements were taken both on the atomized powder and the Cu components. …

Effect Of Process Parameter On Temperature Distribution, Microstructure, And Mechanical Properties Of Self-Reacting Friction Stir Welded Aluminum Alloy 6061-T651, Monica Adriana Torres

Open Access Theses & Dissertations

Self-reacting friction stir welding is the latest FSW tool configuration developed, it employs two shoulders--one on top and one on the bottom of the workpiece-- this tool configuration offers many advantages over conventional welding techniques. However, the current lack of information and specifications limits its understanding and application. This investigation analyzed the effect of process parameters on temperature distribution, microstructure evolution, and final mechanical properties of 6061-T651 SR-FS welds. A factorial experiment was carried out, in which three-process parameters were analyzed--rotational speed, travel speed, and tool plunge force-- three levels were analyzed for each parameter, except for a tool plunge …

Fabrication And Characterization Of Nanocrystalline Yttrium Oxide Thin Films For Electronic Device Applications, Mudavakkat Vikas Haridas

Open Access Theses & Dissertations

This thesis presents the optimization of growth conditions for fabricating nanocrystalline Yttrium Oxide (Y2O3) thin films on silicon and optical grade, high quality quartz substrates in order to study its structural, optical and electrical properties for electronic device applications.

Commercially Y2O3 has proven to be difficult to fabricate at high quality due to its high temperature growth requirements and the need to alter established fabrication methods for electronic devices. A high temperature requirement for high quality poses a problem for research and analysis. This calls upon for an optimization of the growth conditions to facilitate fabrication of thin films for …

The Effect Of Cr, Si And B On The Oxidation Behavior On Three Nb-Based Alloys, David Alvarez

Open Access Theses & Dissertations

Nb-based alloys are of particular interest to replace the current Ni-based superalloys for high-temperature structural applications. One important limitation to improve the efficiency of gas-turbine engines is the temperature limit of current materials being used. By allowing the temperature to increase, the efficiency will increase. Nb-based alloys have high melting points and adequate mechanical properties but the oxidation resistance is still inadequate.

This research focuses on the oxidation behavior of three Nb-based alloys to study the effect of Cr and Si variation and look at the effect of Boron. Boron can form a glassy borosilicate which is viscous at high …

An Euler Solver For Nonlinear Water Waves Using A Modified Staggered Grid And Gaussian Quadrature Approach, Qi Fan

LSU Master's Theses

A structured, finite-volume Euler solver for non-hydrostatic, free surface flows is developed to simulate coastal nonlinear dispersive water waves. A semi-implicit projection method which splits the pressure term into hydrostatic and non-hydrostatic parts is employed. A vertically shifted, staggered grid is designed to accommodate a new Gaussian discharge calculator and to facilitate the enforcement of a non-hydrostatic free-surface boundary condition. The Gaussian discharge calculator on the shifted grid increases the dispersion accuracy compared to traditional approaches that calculate discharges on a regular staggered grid. Numerical results are presented to demonstrate the improvements of these methods.

Solving Evolution Equations For Triad Interaction Of Shallow Water Waves, Qian Zhang

LSU Master's Theses

This study focuses on solving the evolution equations for triad interaction in shallow water waves. First, the evolution equations based on Boussinesq-type equations with Pad¨¦ approximant of the exact linear phase velocity using multi-scale perturbation analysis are derived. Next, methods of solving the complex equation directly, splitting the complex function into amplitude and phase functions, and splitting complex function into real and imaginary parts are implemented to solve the evolution equations. Then the fourth-order Runge-Kutta (RK4) numerical scheme is employed to solve the evolution equations, and corresponding numerical results of three wave interaction are presented demonstrating the sensitivity of the …

Comparison Of Different Integral Histogram Based Tracking Algorithms, Sriharsha Atluri

LSU Master's Theses

Object tracking is an important subject in computer vision with a wide range of applications – security and surveillance, motion-based recognition, driver assistance systems, and human-computer interaction. The proliferation of high-powered computers, the availability of high quality and inexpensive video cameras, and the increasing need for automated video analysis have generated a great deal of interest in object tracking algorithms. Tracking is usually performed in the context of high-level applications that require the location and/or shape of the object in every frame. Research is being conducted in the development of object tracking algorithms over decades and a number of approaches …

The Transient Wave Effect And Real Losses Correlation-Frequency, Temporal, And Spatial Analysis, Dina Sa Knight

LSU Master's Theses

Water distribution systems are prone to transients since pumps need to be started and stopped, pumps may have sudden flow changes, human blunders can occur, equipment may fail, or other unavoidable natural events may ensue. Surge modeling techniques are available to calculate variations in pressure, under extreme or normal operating conditions, serving as a tool to predict extreme events in order to design a suitable system and, or, to aid in the implementation of proper measures to mitigate transients. However, modeling an entire water network system may not be cost effective and may require extensive research and time especially in …

Performance Of Control Room Operators In Alarm Management, Dileep Buddaraju

LSU Master's Theses

Pipelines transport millions of barrels of petroleum products every day. These systems have significant safety concerns. The BP oil spill in the Gulf of Mexico, while concerned with oil and gas extraction rather than distribution, shares many of the same safety and reliability issues as distribution systems, and demonstrates the significant potential for major disasters in the pipeline industry. In this work, a research study is being conducted to further understanding of the role of operators in the management of alarm systems and to measure the performance of operators in handling abnormal situations like pressure loss, liquid inflow/outflow variation and …

Effects Of Thermo-Mechanical Loading From In-Situ Studies Of Eb-Pvd Thermal Barrier Coatings, Melan N. Jansz

Electronic Theses and Dissertations

The thermo-mechanical effects on the strain evolution within an EB-PVD thermal barrier coating (TBC) is presented in this work using in-situ characterization. Synchrotron X-ray diffraction at sector 1-ID at the Argonne National Laboratory provided both qualitative and quantitative in-situ data on the strain evolution under a thermal cycle with mechanical loading. The results show that at a critical combination of temperature and load, the stress in the thermally grown oxide (TGO) layer in the TBC reaches a tensile region. These significant findings enhance existing literature showing purely compressive strains within the TGO where mechanical loads have been neglected. The results …