Mechanical Engineering Commons^™

Thermal Barrier Coatings (Tbc's) For High Heat Flux Thrust Chambers, Christopher Michael Bradley

Open Access Theses & Dissertations

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the …

A Block Operator Splitting Method For Heterogeneous Multiscale Poroelasticity, Paul M. Delgado

Open Access Theses & Dissertations

Traditional models of poroelastic deformation in porous media assume relatively homogeneous material properties such that macroscopic constitutive relations lead to accurate results. Many realistic applications involve heterogeneous material properties whose oscillatory nature require multiscale methods to balance accuracy and efficiency in computation.

The current study develops a multiscale method for poroelastic deformation based on a fixed point iteration based operator splitting method and a heterogeneous multiscale method using finite volume and direct stiffness methods. To characterize the convergence

of the operator splitting method, we use a numerical root finding algorithm to determine a threshold surface in a non-dimensional parameter space …

Nanocomposite And Mechanically Alloyed Reactive Materials As Energetic Additives In Chemical Oxygen Generators, Marco Antonio Machado

Open Access Theses & Dissertations

Chemical oxygen generators are widely used for aircraft, spacecraft, submarines, and mine rescue. Oxygen-generating compositions typically include alkali metal chlorate or perchlorate that decomposes at increased temperatures, a transition-metal oxide as a decomposition catalyst, and a metal fuel that reacts with part of the produced oxygen to provide heat for a self-sustained propagation of the decomposition/combustion wave. To increase the oxygen yield per unit mass, it is of interest to minimize the amount of metal fuel, but decreasing its content leads to pulsating combustion and undesired fluctuations of the oxygen flow rate. This work explores the feasibility of replacing iron …

Development Of A Thermal Imaging Feedback Control System In Electron Beam Melting, Emmanuel Rodriguez

Open Access Theses & Dissertations

The Electron Beam Melting (EBM) process is a promising technology in the rapid manufacturing of metal components. EBM has the potential to reduce the cost of metal parts by minimizing the use of raw materials and machining time. The EBM technology has several advantages over other additive manufacturing (AM) technologies of metal, such as manufacturing speed and mechanical properties of the finished parts. For the process to be accepted in the aerospace industry as a flight-ready manufacturing technology, however, improved control and feedback must be implemented in the building process for better part quality and uniform production in manufacturing. As …

Microstructural-Based Modeling Of Electrical Percolation In Polymer Nanocomposites, Neelima Yellepeddi

Theses and Dissertations

Polymer nanocomposites (PNCs) represent a radical alternative to conventional filled polymers or polymer blends. In contrast to conventional composites, where the included phase is on the order of micrometers, PNCs are defined as those that have discrete constituents on the order of a few hundred nanometers. The value of PNCs is not solely based on tailoring mechanical properties, as in traditional composite design and manufacture, but rather on the potential for the design and optimization of multi-functional properties. There is major interest in these polymeric materials embedded with a conductive nanoscale filler. This is due to the possibility of designing …

Boiling And Evaporation On Micro/Nanoengineered Surfaces, Xianming Dai

Theses and Dissertations

Two-phase transport is widely used in energy conversion and storage, energy efficiency and thermal management. Surface roughness and interfacial wettability are two major impact factors for two-phase transport. Micro/nanostructures play important roles in varying the surface roughness and improving interfacial wettability. In this doctoral study, five types of micro/nanoengineered surfaces were developed to systematically study the impacts of interfacial wettability and flow structures on nucleate boiling and capillary evaporation. These surfaces include: 1) superhydrophilic atomic layer deposition (ALD) coatings; 2) partially hydrophobic and partially hydrophilic composite interfaces; 3) micromembrane-enhanced hybrid wicks; 4) superhydrophilic micromembrane-enhnaced hybrid wicks, and 5) functionalized carbon …

Wave Propagation In Metamaterial Using Multiscale Resonators By Creating Local Anisotropy, Raiz U. Ahmed, Sourav Banerjee

Faculty Publications

Directional guiding, passing or stopping of elastic waves through engineered materials have many applications to the engineering fields. Recently, such engineered composite materials received great attention by the broader research community. In elastic waves, the longitudinal and transverse motion of material particles are coupled, which exhibits richer physics and demands greater attention than electromagnetic waves and acoustic waves in fluids. Waves in periodic media exhibit the property of Bragg scattering and create frequency band gaps in which the energy propagation is prohibited. However, in addition to the Bragg scattering, it has been found that local resonance of artificially designed resonators …

Mechanical Characterization Of Composite Repairs For Fiber-Glass Wind Turbine Blades, Tanveer Singh Chawla

Theses and Dissertations

While in service, wind turbine blades experience various modes of loading. An example is impact loading in the form of hail or bird strikes, which might lead to localized damage or formation of cracks a few plies deep on the blade surface. One of the methods to conduct repairs on wind turbine blades that are damaged while in service is hand lay-up of the repair part after grinding out the damaged portion and some of its surrounding area. The resin used for such repairs usually differs from the parent plate resin in composition and properties such as gel time, viscosity, …

Acoustic Emission Study Of Fiber Orientations On Fiber-Metal Laminates Under Monotonic Tensile Loading, Man Fung (Frank) Chow

Dissertations and Theses

No abstract provided.

The Determination Of Drag And Lift Forces Of A Rigid Beam Located Within A Turbulent Boindary Layer By Means Of Large Eddy Simulation Modeling, Santiago Helman

Dissertations and Theses

"Recent studies such as those conducted by Akaydin, Elvin and Andreopoulos in [1] have described and quantified the electrical power that can be extracted from a moving flow by the implementation of energy harvesters. In such study, a flexible cantilevered beam was fitted with a cylindrical prism at the free end and placed within a uniform flow field. Due to the vortex shedding generated by the prism (e.g. Von Karman vortices) the beam was found to oscillate about the undisturbed position. The beam in question was then outfitted with a piezoelectric material in order to translate the transient strain energy …

Image Analysis Of Air-Bubble Injection (Front And Side View) Into A Turbulent Liquid Stream, Navjot Kaur

Dissertations and Theses

"This study concerns an air bubble injection experiments in a vertical upward annular channel in which a 0.4 mm hole was created to inject the air bubbles into the turbulent stream. Water was used as a testing fluid, and the experiments were performed at atmospheric pressure and room temperature. A high-speed video camera was used to capture the dynamics of the bubble formation process. Two different experimental views were used: a front view in which flow velocity was 0.80 m/s (2.68 GPM) at Reynolds number, Re=7413 and to inject air bubbles into water stream air bubble injection rate was set …

Closed Form Solutions To The Optimality Equation Of Minimal Norm Actuation, Jorge Antonio Guerra

LSU Master's Theses

This research focused on the problem of minimal norm actuation in the context of partial natural frequency or pole assignment applied to undamped vibrating systems by state feedback control. The result of the research was the closed form solutions for the minimal norm control input and gain vectors. These closed form solutions should took open loop eigenpairs and the desired frequencies of the controlled system and outputted the optimal controller parameters. This optimization technique ensures that the system’s dynamics will be effectively controlled while keeping the controller effort minimal. The controller must then be able to shift only the desired …

Effects Of Partial Confinement And Local Heating On Healing Efficiencies Of Self-Healing Particulate Composites, Jonah Champagne

LSU Master's Theses

Shape memory polymers are smart materials that can be trained to hold a temporary shape through programming and regain their original shape upon heating. Since there discovery in the 1960s, much research has been devoted to the study of these polymers. Of particular interest in recent years is the study of self-healing shape memory polymers. In a previous study, it has been shown that in order for efficient healing to take place in self-healing shape memory polymers, confinement during healing is essential. Moreover, a two-step close-then-heal (CTH) approach to healing was suggested. It was shown that use of this CTH …

Comparison Of In Vivo Human Knee Joint Kinematics Using Axodes, Jacob Hipps

LSU Master's Theses

The human knee is of particular interest because of its importance in mobility. Pain and stability can be directly related to the motion, or kinematics, of the knee. Many studies have been conducted to quantify human knee kinematics, both in vitro and in vivo. One of the inherent issues with in vivo, skin mounted measurement systems is that they do not account for soft tissue artifact. Compensation for soft tissue artifact has been a difficult challenge for skin mounted tracking systems and has not yet been achieved. Therefore, bone mounted skeletal pins were chosen as the method of gathering kinematic …

Parametric Optimization Of A Single-Tracked Vehicle, Darrick Jason Berner

LSU Master's Theses

ABSTRACT The purpose of a suspension system for a vehicle is to contribute to the handling and assist in isolating the occupants from vibrations due to road irregularities. Generally, these primary functions are often at odds so the goal is to design a suspension system that finds the appropriate compromise. The focus of this thesis is to develop a two degree of freedom model and use parametric analysis to demonstrate an optimization technique by varying several geometric characteristics on a single-track vehicle. Furthermore, a dynamic vibration absorber will be added to the model to demonstrate its effect on the system. …

Synthesis Of Poly(L-Lactic Acid) Scaffolds From Dioxane/Ethanol Using Control Rate Freezing And Study Of Its Microstructural Properties, George Idicula

LSU Master's Theses

Bio-degradable poly (l-lactic acid) (PLLA) scaffolds were prepared by using thermally induced phase separation (TIPS) method. A solution of PLLA-Dioxane was formed by dissolving PLLA in dehydrated 1,4-Dioxane at three wt/vol percentages, specifically 3, 7 and 10%. This PLLA-Dioxane solution was then frozen in borosilicate glass vials (5mL) at three cooling rates (1, 10 and 40 ˚C/min) in a commercially available controlled rate freezer (CRF). The frozen solution was freeze-dried to sublimate the Dioxane. The microstructural properties of the resulting PLLA scaffolds were determined utilizing Scanning Electron Microscopy (SEM) images and uni- axial compressive testing. The relationship between the wt/vol …

Numerical Evaluation And Analysis Of The Adhesion Phenomena In Thermal Barrier Coating Systems Through Bio-Mimicking Plasma Process, Naser Imran Hossain

LSU Master's Theses

Thermal Barrier Coatings or TBCs when abbreviated are an imperative part of the thermal protection system of expensive equipment and machinery in the automobile and aeronautics industry. They provide protection to expensive alloy materials upto a temperature of 2700° C without expensive metallurgical additions. Unfortunately, the problem of coating adhesion has plagued the TBC field for years, leading to catastrophic failures in critical TBC systems. Efforts to chemically improve bond strength has not been entirely successful, so the only other efficient way to do this would be some kind of mechanical interlocking that occurs at micro/nano scales. This research work …

Electric Field Influence On The Combustion Of Fuel Droplets, Solomon Benghan

LSU Master's Theses

Improving the combustion efficiency of fuels in combustion devices has become imperative in the face of the diminishing rate of the discovery of new energy sources and an ever increasing demand for energy. While there are other ways of improving combustion efficiency, this study investigated the effect of electric field on the combustion of fuel droplets. In order to model the physics of the problem, a mass transfer evaporation model, heat transfer evaporation model and a simple burning droplet model were considered and their result compared to existing result from literature. A burning rate constant of 1.380mm2/s, 14.910mm2/s and 0.612mm2/s …

Instability Analysis And Suppression Of Instability In Low-Density Gas Jets, Sukanta Bhattacharjee

LSU Master's Theses

A numerical study is conducted to understand the global instability of very low-density jets (as encountered in thermal plasmas). The simulations have been carried out for different parameters of density ratios, S = ƒÏj /ƒÏ‡ ranging from 0.5 to 0.03, different Reynolds numbers ranging from 500 to 4000 and different momentum thickness obtained by different extension tube length ranging from 3 to 6 diameter long. The flow parameters and vortex structures has been visualized to understand the details of the evolution of the flow field. The axisymmetric shear layer rolls up in the near field of the jet forming vortex …

Effect Of Rest Time On Heart Rate, Perceived Exertion, And Strength, Amir Bahador Bahmani Bahman Beiglou

LSU Master's Theses

Finding a proper work/rest schedule is considered an important factor for improved efficiency, safety, and a higher rate of productivity in the workplace. The purpose of this study was to determine the optimum rest period for lifting tasks using heart rate, perceived exertion, and physical strength. First, the maximum acceptable weight of the box to be lifted was determined for each one of 10 participants using a psychophysical approach. Then on separate days, participants were required to repetitively lift the box from knuckle height to shoulder height for 20 minutes. They were then allowed to rest 5, 10, 15, or …

Comprehensive Study Of The Dye Sensitized Solar Cell, Gregory Lewis Vick

LSU Master's Theses

A complete electrical model of the dye-sensitized solar cell has been presented. This model relates the material parameters of the cell to the cell’s performance. The full model is reduced to an Idealized form and simulated to find an idealistic power curve or current (I) – voltage (V) curve. The operating parameters of reflectivity, temperature, reverse saturation current and ideality factor are investigated. A sensitivity analysis is completed to determine what parameters have a dominating influence on the overall cell performance. It was found, for the ideal case of the dye sensitized solar cell, that the factors of absorptivity, temperature, …

Liposomal Uptake Of Silver And Gold Nanoparticles, Dipon Chanda

LSU Master's Theses

The main objective of this work is to study the liposomal uptake of silver and old nanoparticles. Liposomes were prepared in Heating Method. The phospholipids used to prepare liposomes are 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (16:0 PC); 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (16:0 PG); 1,2-distearoyl-sn-glycero-3-phosphocholine (18:0 PC); 1,2-distearoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (18:0 PG).Four different combinations of phospholipids were used to prepare liposomes. In all four combinations two types of phospholipids were used. The liposomes were incubated for 30 minute, 1 hour, 2 hour and 4 hour with silver and gold nanoparticles in streptavidin coated glass slide. All four liposomal formulations had a biotinylated lipid (1-oleoyl-2-[12-biotinyl(aminododecanoyl)]-sn-glycero-3-phosphocholine) which has a string …

A Polymer-Based Microfluidic Device With Electrolyte-Enabled Distributed Transducers (Eedt) For Distributed Load Detection, Peng Cheng

Mechanical & Aerospace Engineering Theses & Dissertations

The capability of detecting distributed static and dynamic loads is indispensable in a wide variety of applications, such as examining anatomical structures of biological tissues in tissue health analysis and minimally invasive surgery (MIS) and determining the texture of an object in robotics. This dissertation presents a comprehensive study of a polymer-based microfluidic device with electrolyte-enabled distributed transducers and demonstrates a new concept on using a single microfluidic device for distributed-load detection, which takes advantage of the low-cost microfluidic fabrication technology and the low modulus and biocompatibility of polymer. The core of the device is a single deformable polymer microstructure …

Generalizable Methods For Modeling Lumbar Spine Kinematics, Craig Joseph Simons

Electronic Theses and Dissertations

A more complete understanding of lumbar spine kinematics could improve diagnoses and treatment of low back pathologies and may advance the development of biomechanical models. Kinematics describes motion of the five lumbar vertebrae without consideration for the forces that cause the motion. Despite considerable attention from researchers and clinicians, lumbar spine kinematics are not fully understood because the anatomy is not accessible for direct observation and the complex governing biomechanics produce small magnitude, coupled intervertebral movements.

The overall goal of this project was to develop a descriptive model of intervertebral lumbar spine kinematics that is applicable to a generalizable subject …

A Novel Resistance Exercise Machine For Use In A Lower Body Negative Pressure Box To Counteract The Effects Of Weightlessness, Christine M. Dailey

Doctoral Dissertations and Master's Theses

Physiological deconditioning is a critical problem in space, especially during long-term missions. Resistance exercise coupled with lower body negative pressure (LBNP) has been shown to be effective in counteracting some of the deconditioning related problems. This thesis describes the development of a compact and effective resistance exercise machine that works within an existing environmentally controlled LBNP Box and is designed to simulate both exercise and sitting, to prevent microgravity-induced deconditioning by simulating physiological and biomechanical features of upright exercise and daily activities. Theoretical calculations are carried out to determine whether kinematics, musculoskeletal loadings, and metabolic rate during supine exercise within …

Separation Control On High Lift Low-Pressure Turbine Airfoils Using Pulsed Vortex Generator Jets, Ralph J. Volino, Mounir B. Ibrahim

Mechanical Engineering Faculty Publications

Boundary layer separation control has been studied using vortex generator jets (VGJs) on a very high lift, low-pressure turbine airfoil. Experiments were done under low (0.6%) freestream turbulence conditions on a linear cascade in a low speed wind tunnel. Pressure surveys on the airfoil surface and downstream total pressure loss surveys were documented. Instantaneous velocity profile measurements were acquired in the suction surface boundary layer. Cases were considered at Reynolds numbers (based on the suction surface length and the nominal exit velocity from the cascade) of 25000 and 50000. Jet pulsing frequency and duty cycle were varied. In cases without …

A Study On Implementation Of Co2 Abatement Solutions For Existing Ships, Young C. Kwon

World Maritime University Dissertations

Recent high fuel prices and global economic recessions have driven shipowners to turn their attention to saving operational costs of their ships. For this reason, a variety of energy saving solutions has been developed and proposed in order to improve energy efficiency of ships. In addition, IMO have also proposed the best practices for energy saving solutions for existing ships through the SEEMP Guidelines. However, these proposed energy saving solutions (i.e. CO2 abatement solutions) do not give sufficient reliability due to the uncertainties of various parameters surrounding ships. These uncertainties may have a significant impact on effectiveness of individual energy …

Comparison Of 4d Phase-Contrast Mri Flow Measurements To Computational Fluid Dynamics Simulations Of Cerebrospinal Fluid Motion In The Cervical Spine, Theresia Yiallourou, Jan Robert Kroger, Nikolaos Stergiopulos, David Maintz, Bryn A. Martin, Alexander C. Bunck

Mechanical Engineering Faculty Research

Cerebrospinal fluid (CSF) dynamics in the cervical spinal subarachnoid space (SSS) have been thought to be important to help diagnose and assess craniospinal disorders such as Chiari I malformation (CM). In this study we obtained time-resolved three directional velocity encoded phase-contrast MRI (4D PC MRI) in three healthy volunteers and four CM patients and compared the 4D PC MRI measurements to subject-specific 3D computational fluid dynamics (CFD) simulations. The CFD simulations considered the geometry to be rigid-walled and did not include small anatomical structures such as nerve roots, denticulate ligaments and arachnoid trabeculae. Results were compared at nine axial planes …

Stress And Strain Adaptation In Load-Dependent Remodeling Of The Embryonic Left Ventricle, Christine Buffinton

Faculty Journal Articles

Altered pressure in the developing left ventricle (LV) results in altered morphology and tissue material properties. Mechanical stress and strain may play a role in the regulating process. This study showed that confocal microscopy, three-dimensional reconstruction, and finite element analysis can provide a detailed model of stress and strain in the trabeculated embryonic heart. The method was used to test the hypothesis that end-diastolic strains are normalized after altered loading of the LV during the stages of trabecular compaction and chamber formation. Stage-29 chick LVs subjected to pressure overload and underload at stage 21 were reconstructed with full trabecular morphology …

A Finite Difference Implementation Of Phase Field Theory, Nicholas W. Oren

Master's Theses

Computationally handling cracks generally results in numerically unstable results. Specifically handling the infinite stresses at the crack tip as well as the abrupt change from virgin material to failed material creates numerical instabilities. This project seeks to determine if phase field physics theory, particularly the physics based modification developed by B. N. Cassenti, can be appropriately applied to cracks. Phase field theory introduces an additional state variable, the phase of the material. The phase represents the level of failure (by cracking), and diffuses the failure along a crack by specified equations. The modification, based on a variational principle, was tested …