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Articles 151 - 180 of 257
Full-Text Articles in Mechanical Engineering
Manufacturing, Testing And Modeling Of Advanced Filament Wound Grid Stiffened Composite Cylinders, Ravi Chaitanya Velamarthy
Manufacturing, Testing And Modeling Of Advanced Filament Wound Grid Stiffened Composite Cylinders, Ravi Chaitanya Velamarthy
LSU Master's Theses
Advanced Grid Stiffened (AGS) structures are a kind of FRP composites that are being extensively used in many engineering fields because of their inherent advantages. Hence it is of utmost importance to understand the basic mechanism of these structures in order to develop better models and to find ways to improve their efficiency. This thesis discusses the manufacturing technology used viz. the filament winding technique to fabricate grid stiffened composite cylinders. A step by step procedure of the fabrication process of grid cylinders is explained. The confinement effectiveness of the AGS cylinders is evaluated by filling them with concrete and …
Study Of Demolding Process In Thermal Imprint Lithography Via Numerical Simulation And Experimental Approaches, Zhichao Song
Study Of Demolding Process In Thermal Imprint Lithography Via Numerical Simulation And Experimental Approaches, Zhichao Song
LSU Master's Theses
The objective of present study was to analyze the mechanical behavior of polymer resist during the demolding process, such as stress distribution and evolution; distortion and tilt of microstructures in thermal imprint lithography, a new emerging technique in mass production of micro/nanoscale patterns. One of the most challenging technical issues for thermal imprint lithography is the structural damages during demolding process. Thermal stress, adhesion force and friction force all play important roles in determination of the success of demolding and it is crucial to understand the underlying physics in order to optimize the structure and process design. In present study, …
Passive Alignment Of Micro-Fluidic Chips Using The Principle Of Elastic Averaging, Sitanshu Gurung
Passive Alignment Of Micro-Fluidic Chips Using The Principle Of Elastic Averaging, Sitanshu Gurung
LSU Master's Theses
This thesis presents a novel design for a passive alignment feature for vertically stacking chips in a micro fluidic device. Each chip is the size of a standard microscopic slide (75mm—25mm) and is a highly specialized functional unit designed and fabricated to process fluidic samples. The fluidic samples in the device flows from one chip to another using inter connecting holes 500μm-100μm in diameter. Hence an alignment of better than 100μm between chips is necessary to allow for the interconnecting holes to overlap so as to provide with a path for the fluid to flow. The feature to be used …
Studies On The Heat/Mass Transfer Characteristics And Fluid Structure In A Square Internal Cooling Channel With Dimpled Surfaces, Fuguo Zhou
LSU Master's Theses
Experimental and numerical studies of heat/mass transfer on the dimpled surfaces in square channels are performed. The naphthalene sublimation method is employed in the experimental study. First, in a two-passage rotating channel, circle dimple matrices are cast on the leading and trailing walls in both the inlet and outlet of the serpentine channel. The experiments are carried out with Reynolds number of 7,000 and 21,000, and with Rotation number of 0 and 0.2. The dimpled walls lead to heat/mass transfer enhancements over smooth surfaces both in the stationary case and in the rotating case. In the stationary case, the dimple …
Fabrication Of Perforated Polymer Membranes Using Imprinting Technology, Anish Roychowdhury
Fabrication Of Perforated Polymer Membranes Using Imprinting Technology, Anish Roychowdhury
LSU Master's Theses
The goal of the present study was to fabricate perforated membrane structures in polymers with the pore diameter ranging from 10 ìm down to the sub ìm scale. The perforated membrane structure plays an important role in many biological systems. Thus the ability to reproduce such architecture will help with the study of biological systems by mimicking biological cell membrane-like structures and open new vistas in the study of transport behavior in cell biology and the separation of biological vesicles. Such structures also have potential uses as components in polymer optics and modular micro/nanofluidic devices. Use of polymer substrates is …
Experimental Investigation Of Heat Transfer Rate In Micro-Channels, Pritish Ranjan Parida
Experimental Investigation Of Heat Transfer Rate In Micro-Channels, Pritish Ranjan Parida
LSU Master's Theses
Metal-based MHEs are of current interest due to the combination of high heat transfer performance and improved mechanical integrity. Efficient methods for fabrication and assembly of functional metal-based MHEs are essential to ensure the economic viability of such devices. The present study focuses on the results of heat transfer testing of assembled Cu- and Al- based microchannel heat exchanger (MHE) prototypes. Efficient fabrication of Cu- and Al- based high-aspect-ratio microscale structures (HARMS) have been achieved through molding replication using surface engineered, metallic mold inserts. Replicated metallic HARMS were assembled through eutectic bonding to form entirely Cu- and Al- based MHE …
Film Cooling From A Row Of Holes Supplemented With Anti Vortex Holes, Alok Dhungel
Film Cooling From A Row Of Holes Supplemented With Anti Vortex Holes, Alok Dhungel
LSU Master's Theses
Film cooling is a technique employed to protect the external surface of gas turbine blades from the hot mainstream gas by ejecting the internal coolant air through discrete holes or slots at several locations on the blade exterior surface. Passing the coolant through conventional cylindrical holes causes a pair of vortices to form which lifts off the coolant jet instead of letting it adhere to the surface. The present study aims at investigating the enhanced cooling performance caused by addition of anti-vortex holes to the main cylindrical film cooling holes. Both heat transfer coefficient and film cooling effectiveness are determined …
Transcendental Eigenvalue Problems Associated With Vibration, Buckling And Control, Jayaram Subramanian
Transcendental Eigenvalue Problems Associated With Vibration, Buckling And Control, Jayaram Subramanian
LSU Master's Theses
The static and dynamic analysis of structures requires us to obtain solutions of their espective governing differential equations subject to appropriate boundary conditions. The dynamic analysis of non-uniform continuous structures is of primary interest, as most traditional methods take the help of discrete models to analyze them. Well established discrete model methods lead to an algebraic eigenvalue problem, the characteristic equation associated with which is a polynomial. The spectral characteristics of a continuous system nevertheless are represented by transcendental functions and cannot be approximated by polynomials efficiently. Hence finite dimensional discrete models are not capable of predicting the response of …
On The Stress Analysis Of Bimetallic Packing Rings, Eric Richard Lewis
On The Stress Analysis Of Bimetallic Packing Rings, Eric Richard Lewis
LSU Master's Theses
The purpose of this research is to try and understand hypercompressor packing ring failures better with a view of ultimately reducing or even eliminating their occurrences. In order to gain further understanding of packing ring failures, we seek to obtain an appreciation of the stresses they experience during operation. First we consider a conventional simulation of an axisymmetric packing ring and cup subjected to the typical pressure loading conditions experienced by these components when installed in a hypercompressor cylinder. The key locations of interest are along the bimaterial interface, and in particular at the ends of the interface. These ends …
Reactive Multilayer Foils And Their Applications In Joining, Xiaotun Qiu
Reactive Multilayer Foils And Their Applications In Joining, Xiaotun Qiu
LSU Master's Theses
In this study, Ni/Al multilayer foils were fabricated by a cold rolling method. A two-stage reaction process was observed in the reaction-ignition experiment. The phase formation process in the cold rolled foils was studied. The first reaction stage with a slow reaction velocity was the lateral growth of Al3Ni phase at isolated nucleation sites and the subsequent coalescence into a continuous layer. The second reaction stage with a fast reaction velocity was the growth of the Al3Ni layers in the direction normal to the Ni/Al interface until all Al was consumed. Afterwards, Al3Ni reacted with the remaining Ni to form …
Measuring Skeletal Kinematics With Accelerometers On The Skin Surface, Kevin Curtis Ayer
Measuring Skeletal Kinematics With Accelerometers On The Skin Surface, Kevin Curtis Ayer
LSU Master's Theses
The most common motion analysis method uses cameras to track the position of markers on bodily surfaces over time. Although each species has a common skeletal frame to reference recorded motions, the soft tissue covering each is not rigid. Markers, therefore, experience motion relative to the bone and do not accurately portray underlying bone activity. This limits clinical use of motion studies and the understanding of joint motion. Use of MEMS accelerometers for removing soft tissue artifact, motion relative to the bone, from surface measurements and determining the position of the underlying bone was investigated. An animal limb was modeled …
Heat Transfer And Flow Characteristics Inside A Gas Turbine Combustor, Yap-Sheng Goh
Heat Transfer And Flow Characteristics Inside A Gas Turbine Combustor, Yap-Sheng Goh
LSU Master's Theses
Heat transfer and flow characteristics inside a typical can-annulus gas turbine combustor are investigated. This is the first study in a public domain to focus on the convective heat loads to combustor liner due to swirling flow generated by swirler nozzles. The objectives of this study are to physically design an experimental combustor test model, to perform local accurate heat transfer and flow measurements, and to better understand the fundamental thermo-fluid dynamic effects inside a combustor equipped with a swirler nozzle provided by Solar Turbines Inc. The local temperature and heat transfer distribution were determined to locate the heat transfer …
Performance Modeling Of Explosively Actuated Devices, Adam M. Braud
Performance Modeling Of Explosively Actuated Devices, Adam M. Braud
LSU Master's Theses
Explosively actuated devices (pin pullers, cable cutters, valves, etc) are used extensively to perform critical functions for aerospace, industrial, and defense related applications. The failure of these devices have led to a greater effort to quantify device design and performance. This thesis describes the actuation process of an explosively actuated valve, including: 1) the burning of the solid explosive HMX (C4H8N8O8) and production of its high pressure gas products, 2) the mass transfer of gas products through an actuator to an expansion volume including choked flow effects, 3) the resulting piston motion …
Simulations Of A Modified Micro-Scale Electrophoretron, Nada Elmajdoub
Simulations Of A Modified Micro-Scale Electrophoretron, Nada Elmajdoub
LSU Master's Theses
This paper presents theoretical analysis and numerical simulations of a modified micro-scale electrophoretron adapted for cycling reaction applications (PCR, LDR...). The electrophoretron consists of a closed-loop microchannel. If one part of the length of the channel has an electroosmotic mobility of an opposite sign than the remaining part, a continuous cyclic motion of the fluid can be sustained if a potential difference is applied on two electrodes strategically placed along the channel. Conservation of mass leads to the formation of a pressure gradient and a related hydrodynamic flow. Under appropriate combination of design parameters, the combined Electroosmotic -hydrodynamic flow contributes …
Modeling Fabrication And Characterization Of A Bio-Micro Thermoelectric Device For Highly Localized Temperature Control, Aparna Prabhakar
Modeling Fabrication And Characterization Of A Bio-Micro Thermoelectric Device For Highly Localized Temperature Control, Aparna Prabhakar
LSU Master's Theses
There is an ever expanding interaction between the fields of micro-electromechanical systems (MEMS) and biology to develop devices to monitor, control and act on living systems. Particularly in the field of cryobiology, there is a need to monitor and control temperature at the cellular level. An important step towards achieving this aim is to fabricate an array of microscale thermoelectric actuators. As a first step for towards achieving such localized control of temperatures in cells and tissues, an array of individually addressable micro-thermoelectric coolers (µTECs) were modeled, characterized, and fabricated. Prefabrication experimentation and modeling were carried out to understand the …
Modeling Of Fiber Reinforced Polymer Confined Concrete Cylinders, Indrani V. Volety
Modeling Of Fiber Reinforced Polymer Confined Concrete Cylinders, Indrani V. Volety
LSU Master's Theses
Fiber Reinforced Polymer (FRP) confined concrete columns have been developed for new construction and rebuilding of concrete piers/piles in engineering structures. Design of these FRP confined concrete columns requires an accurate estimate of the performance enhancement due to the confinement mechanism. Therefore, the key is to develop a confinement model, a model that relates the confined concrete strength with the unconfined concrete strength and the confining pressure provided by the FRP. Due to its closed-form expression and ease of application, design-oriented confinement models predominate in designing FRP confined concrete columns. Design oriented models are directly based on the interpretation of …
A New Method To Determine Radiative Properties Of Rough Solid Surfaces, Raghu Nandan Mutukulla
A New Method To Determine Radiative Properties Of Rough Solid Surfaces, Raghu Nandan Mutukulla
LSU Master's Theses
The radiative properties of the rough surfaces are important both from fundamental and practical standpoint. Thus, there is a need to determine the effect of roughness on radiative properties of materials accurately, as these properties effect the performance of electronic devices, communication devices, optical sensors, and furnaces, amongst others. The effects of roughness are assessed by measuring the reflection coefficients from the carbon rod surfaces and steel 1086 samples over the range of angles 25 to 75 in the visible range and near infrared region. Different levels of roughness are induced on the surfaces by utilizing different grid size sand-paper …
Heat/Mass Transfer In Rotating, Smooth, High Aspect-Ratio (4:1) Coolant Channels With Curved Walls, Eashwar Sethuraman
Heat/Mass Transfer In Rotating, Smooth, High Aspect-Ratio (4:1) Coolant Channels With Curved Walls, Eashwar Sethuraman
LSU Master's Theses
The thesis presents an experimental study of heat/mass transfer coefficient in 4:1 aspect ratio smooth channels with non-uniform cross-sections. Curved leading and trailing edges are studied, for two curvatures of 9.06 m-1 (0.23 in-1) and 15.11 m-1 (0.384 in-1) and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls), and the other configuration has leading and trailing walls that curve inwards into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). The experiments are conducted in a …
Modeling And Fabrication Of A Microthermocouple Array, Adam Cygan
Modeling And Fabrication Of A Microthermocouple Array, Adam Cygan
LSU Master's Theses
Cryobiology is the study of how living cells and tissues respond to freezing and exposure to subzero temperatures. Studies in this field are aimed toward improving methods of cryosurgery as well as the storage of cells and tissues. For example, one area of research is to link the biophysical cellular dehydration and intracellular ice formation in cells during tissue freezing to cell viability and mechanical properties after thawing. There is currently a method for measuring dehydration in cells as part of a tissue, but not an adequate method for measuring intracellular ice formation in tissues. A prototype device that would …
A Generalized Approach For The Control Of Micro-Electromechanical Relays, Mohamed Abdelrahman Younis
A Generalized Approach For The Control Of Micro-Electromechanical Relays, Mohamed Abdelrahman Younis
LSU Master's Theses
MEMS (Micro-Electromechanical Systems) is an area of research and applications that is becoming increasingly popular. It's mainly concerned with integrating micro-mechanical transducers with micro-electronic circuits on common substrates, traditionally silicon, through micro-fabrication. Instead of traditionally having the transducer and the communicating (or control) circuit as two separate entities, MEMS miniaturizes and combines them on a single chip, giving it several advantages, saving space, money, and increasing the sensitivity and accuracy of the integrated system. A micro-electromechanical relay is a type of MEM devices that is becoming increasingly important in a wide range of industries such as the computer industry, the …
Thermal Management Of Micro Gas Chromatographs, Chetan Ramesh
Thermal Management Of Micro Gas Chromatographs, Chetan Ramesh
LSU Master's Theses
Gas chromatography is an analytical technique for separating and analyzing individual components in a gas mixture. Applications of gas chromatographs (GCs) include chemical analysis, environmental maintenance, green house gases monitoring, and forensic analysis when used in conjunction with mass spectrometry. There has been a tremendous interest in miniaturization of gas chromatograph systems because of significantly reduced size, portability, fast response times, low power consumption and low cost. Isothermal analysis is a chromatographic analysis at one column temperature. In temperature programming, a linear increase of column temperature with time is used during the course of the analysis. Temperature programming facilitates separation …
Design And Test Of A Displacement Workspace Mapping Station For Articular Joints, Michael Daly Guillet
Design And Test Of A Displacement Workspace Mapping Station For Articular Joints, Michael Daly Guillet
LSU Master's Theses
In 2003, 267,000 Americans received total knee replacements prohibiting high impact athletics for the remainder of a patient’s life. A better understanding of the movement and constraint of the knee is necessary to provide more realistic motion of or possibly eliminate the need for joint prosthetics. Fixed Orientation Displacement Workspaces (FODW) can be applied to study the relationship of the passive constraint system and six (6) degree of freedom (DOF) movement of the human knee. A FODW consists of the volume of possible positions the tibia/fibula can occupy relative to a fixed femur without changing the relative orientation of the …
Characterization And Tribological Behavior Of Diamond-Like Carbon And Nitrogen-Doped Diamond-Like Carbon Thin Films, Krishna Chaitanya Kadiyala
Characterization And Tribological Behavior Of Diamond-Like Carbon And Nitrogen-Doped Diamond-Like Carbon Thin Films, Krishna Chaitanya Kadiyala
LSU Master's Theses
Diamond-like carbon (DLC) films have been extensively studied for more than two decades due to their highly attractive properties. These films exhibit unique mechanical, electrical and tribological behavior and thus, possess great potential for applications in tribology. However, the high level of internal stress developed and low thermal stability are the main drawbacks. Synthesis of nitrogen-doped DLC (N-DLC) offers the possibility of overcoming these drawbacks. In the present study, DLC and N-DLC films (with low N content) were deposited on Si substrates using a hybrid plasma-assisted CVD/PVD process. Film characterization in terms of microstructure, composition and chemical state of components …
Jet Impingement Cooling Configurations For Gas Turbine Combustion, Eric Ian Esposito
Jet Impingement Cooling Configurations For Gas Turbine Combustion, Eric Ian Esposito
LSU Master's Theses
Impinging jets are commonly used to enhance heat transfer in modern gas turbine engines. Impinging jets used in turbine blade cooling typically operate at lower Reynolds numbers in the range of 10,000 to 20,000. In combustor liner cooling, the Reynolds numbers of the jets can be as high as 60,000. The present study is aimed at experimentally testing two different styles of jet impingement geometries to be used in backside combustor cooling. The higher jet Reynolds numbers lead to increased overall heat transfer characteristics, but also an increase in crossflow caused from spent air. The crossflow air has the effect …
Numerical Solution Of Flow Resistance In Outflow Pathway And Intravitreal Drug Delivery In Vitrectomised Eyes, Jyoti Gururaj Kathawate
Numerical Solution Of Flow Resistance In Outflow Pathway And Intravitreal Drug Delivery In Vitrectomised Eyes, Jyoti Gururaj Kathawate
LSU Master's Theses
In this study, numerical computations of the ocular fluid dynamics in a human eye are presented with a perspective of understanding the mechanisms of increased flow resistance. In the present study, the TM is represented as a multilayered-graded porous structure with specific pore size and void fraction. The flow patterns and pressure distribution in anterior chamber are analyzed to delineate key flow mechanism; the shear stresses on the lens, iris and IW of SC are also examined to locate the maximum values. Inside the human eye, the largest pressure drop occurs across JCT and IW of SC. The highest pressure …
Two-Phase Flow In High Aspect Ratio, Polymer Microchannels For Reagent Delivery Applications, Estelle Evans
Two-Phase Flow In High Aspect Ratio, Polymer Microchannels For Reagent Delivery Applications, Estelle Evans
LSU Master's Theses
Multiphase flow in microfluidics is an increasingly growing field, especially in biotechnology. For instance, a steady-state slug flow would benefit lab-on-a-chip drug delivery methods. This flow would not only use minute amounts of reagents, but it would also decrease the sample processing time. Thus, researching a steady-state plug flow in a microchannel is beneficial to the drug delivery field. Five PMMA, directly-milled microchannels [2: Aspect Ratio 1 (with and without pressure ports, 2): Aspect ratio 2 (with and without pressure ports), and 1: Aspect Ratio 3 (without pressure ports)] were manufactured. These channels were then cleaned, and a PMMA cover …
Pulsed Vertical Jet In Cross Flow At Mean Blowing Ratios 0.35 And 0.45, Pierre-Emmanuel Jacques Joseph Bouladoux
Pulsed Vertical Jet In Cross Flow At Mean Blowing Ratios 0.35 And 0.45, Pierre-Emmanuel Jacques Joseph Bouladoux
LSU Master's Theses
This thesis deals with a pulsed vertical jet transverse to a cross flow (U∞=1.6m/s) at mean blowing ratios 0.35 and 0.45. First the reasons of this study are explained and the previous work in the field is described. Then the experimental setup, the experimental procedures and the data processing are detailed. The system (wind tunnel and jet) is characterized before studying the Jet in Cross Flow (JICF). The JICF is explored under unforced and forced conditions through LASER sheet visualizations and constant temperature anemometry (CTA) measurements using hot-wire sensors. Blowing ratios ranging from 0.150 to 0.600 are studied …
A Thermodynamic Model For Wear In Sliding Contact, Susheel Brahmeshwarkar
A Thermodynamic Model For Wear In Sliding Contact, Susheel Brahmeshwarkar
LSU Master's Theses
Consideration of wear, an irreversible phenomenon, is a very important criterion in design. The knowledge of wear and its behavior enables one to make major considerations to conceptualize and design efficient machinery components with enhanced performance and reliability. The present work deals with the introduction of a novel approach of correlating wear with the thermodynamic properties of the system. The approach involves relating wear to thermodynamic entropy flow in the system using the laws of thermodynamics. This relation is verified experimentally and theoretically by considering a sliding contact in a disk-on-disk configuration for two sets of contacting materials namely Bronze …
Mesoscale Simulation Of Grain Boundary Diffusion Creep In The Presence Of Grain Growth, Lucian Zigoneanu
Mesoscale Simulation Of Grain Boundary Diffusion Creep In The Presence Of Grain Growth, Lucian Zigoneanu
LSU Master's Theses
Grain-boundary (GB) diffusion creep (Coble creep) is the dominant deformation mechanism for the fine-grained materials under low stress and at elevated temperature. During creep deformation the grains become elongated in the tensile direction because of atoms diffusion along GBs from places in compression to those in tension. Consequently, the GB diffusion rate depends on the normal stress gradient along the boundaries. It is widely accepted that the GB migration generally plays two important roles during Coble creep: one leading to the decrease of the creep rate due to the increase of the grain size by GB migration mediated grain growth …
Mesoscale Predictions For The Dynamic Compaction Of Explosively-Coated Aluminum Micro-Particles, Michael Wayne Crochet
Mesoscale Predictions For The Dynamic Compaction Of Explosively-Coated Aluminum Micro-Particles, Michael Wayne Crochet
LSU Master's Theses
Conventional granular explosives are widely used in aerospace and defense-related industries. Powdered metals are often mixed with high explosives to enhance detonation. The effectiveness of these mixtures is limited by the slow burning of the metal relative to the explosive and their sensitivity to mechanical loading. Granular energetic composites, composed of an aluminum core coated with a layer of the high explosive RDX (C3H6N6O6), may be a high-performance alternative to conventional explosives because of a higher metal combustion rate and lower impact sensitivity. Though the technology required to manufacture granular energetic composites …