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Articles 1 - 23 of 23
Full-Text Articles in Mechanical Engineering
Composite Sandwich Structure With Grid Stiffened Core, Venkata Dinesh Muthyala
Composite Sandwich Structure With Grid Stiffened Core, Venkata Dinesh Muthyala
LSU Master's Theses
Composite sandwich structures have been widely used in aerospace structures, ship building, infrastructure, etc. due to their light weight and high strength to weight ratio. Traditionally, light-weight core materials such as foam core, truss core, honeycomb core have been used in fabricating sandwich structures with limited success. In this study, a new composite sandwich structure with a hybrid core was proposed, fabricated, tested, and modeled. The hybrid core consists of a fiber reinforced polymer grid skeleton that is filled in by extremely light-weight syntactic foam in the bay areas. The new sandwich structure was manufactured using a new manufacturing process. …
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 …
Development Of Micropump For Microfluidic Applications, Dong Eun Lee
Development Of Micropump For Microfluidic Applications, Dong Eun Lee
LSU Doctoral Dissertations
This dissertation covers the research work on two types of micropumps, one is based on magnetohydrodynamic (MHD) principle that utilizes Lorentz force for actuation, and the other is based on electrochemical actuation. The AC-type MHD micropump was designed and analyzed as a solution to the bubble formation problem encountered in DC-type MHD micropump. A UV-LIGA process using thick layer of SU-8 negative photoresist was successfully developed to microfabricate the AC MHD micropump. Preliminary studies and tests of the AC MHD micropumps demonstrate that bubble formation was significantly reduced to permit the proper function of the micropump. A continuous flow was …
Characterization Of Advanced Composites- A Nondestructive Approach, Phani Surya Kiran Mylavarapu
Characterization Of Advanced Composites- A Nondestructive Approach, Phani Surya Kiran Mylavarapu
LSU Doctoral Dissertations
Adhesively bonded sandwich structures comprising of particulate composites as core and graphite epoxy skins as stiffeners are widely used for various applications in the marine and aerospace industry. The core material and the stiffener are held together by an adhesive bond. Particulate composites are made from a mixture of a polymer resin and hollow or solid particles. Hollow particulate composites are known as syntactic foams. Particulate composites possess attractive mechanical and physical properties such as high compressive strength etc, making them attractive materials for use in structural applications. Characterization of the adhesive bondline and core material in sandwich structures is …
Micro Injection Fuel/Air Premixer/Combustion, Jian Zhang
Micro Injection Fuel/Air Premixer/Combustion, Jian Zhang
LSU Doctoral Dissertations
Lean premixed (LP) combustion has become the dominant industrial approach to reduce NOx emissions. Homogeneous mixing of lean fuel and air mixtures prevents the presence of undesirable localized regions of near-stoichiometric fuel/air mixtures, thereby allowing a reduction in thermal NOx. A new concept, a multi-point micro injection premixer, is presented in this dissertation. The multi-point micro injection premixer is a porous plate that provides a simple but extremely effective method to mix air and fuel. An array of fuel jets is injected in a direction perpendicular to the plane of the premixer plate into an oncoming counterflow stream of air. …
An Investigation Of The Frictional And Thermal Behavior Of Oscillatory Sliding Line Contacts, Mongi Mansouri
An Investigation Of The Frictional And Thermal Behavior Of Oscillatory Sliding Line Contacts, Mongi Mansouri
LSU Doctoral Dissertations
This research deals with an experimental and numerical investigation of the frictional and thermal behavior of pin-bushing pairs, operating at reciprocating sliding motion or under heavy loads. Large interfacial temperatures developed due to frictional heating can cause failure. Therefore, numerical prediction and analysis of the surface temperature under various operating conditions are important. Laboratory tests using a pin-bushing tester provided measurements of the friction coefficient and temperature. Hard coated and plain (uncoated) bushings, both made of induction hardened stainless steel, were tested. Lower coefficient of friction and surface temperature were observed in the case of the coated bushing. In the …
Measurements And Computations Of The Flow In Full-Scale Sugar Evaporative-Crystallizers And In Lab-Scale Models, Luis Fernando Echeverri
Measurements And Computations Of The Flow In Full-Scale Sugar Evaporative-Crystallizers And In Lab-Scale Models, Luis Fernando Echeverri
LSU Doctoral Dissertations
The circulation of massecuite is a key factor in achieving efficient heat transfer and crystallization in sugar evaporative crystallizers, and should be as high as practically possible for recovery, quality, and capacity reasons. This research report presents results on the circulation obtained applying modern experimental and numerical techniques. The main goals are contributing to expand the understanding of the process in sugar crystallizers; developing realistic models for the simulation of the circulation; and studying the effect of different design parameters. The circulation of massecuite is driven by buoyancy force due to density difference between the vapor generated and the surrounding …
Flow Field And Heat Transfer Analyses Of Mechanical Seals, Zhaogao Luan
Flow Field And Heat Transfer Analyses Of Mechanical Seals, Zhaogao Luan
LSU Doctoral Dissertations
Mechanical seals are widely used in rotating equipment such as pumps, turbines and agitators to prevent leakage. One crucial factor for keeping seals reliable is the thermal behavior of the seal rings. The existing literature on thermal effects in seals primarily concentrates on the conduction of heat into the rings. Yet, a more complete analysis requires understanding of the flow field around the rings. In this dissertation, both the laminar and turbulent flows within the seal chamber are studied and their effects on the heat transfer in the seal rings are evaluated. Based on extensive sets of numerical simulations, heat …
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 …
Turbulence Modeling For Film Cooling Flows, Asif Hoda
Turbulence Modeling For Film Cooling Flows, Asif Hoda
LSU Doctoral Dissertations
An improved two equation turbulence model has been developed in this dissertation to better predict the complex film cooling flow field that is formed from the interaction of a coolant jet and a crossflow over a modeled turbine blade surface. Film cooling of turbine blades is commonly employed to effectively protect turbine blades from thermal failure and thereby to allow higher inlet temperatures in order to increase the efficiency of gas turbine engines. Film cooling involves the injection of rows of coolant jets from slots on the surface of a turbine blade which is then bent over by the crossflow …
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 …
Manufacturing And Characterization Of High-Aspect-Ratio Diffusive Micro-Mixers, Vamsidhar Palaparthy
Manufacturing And Characterization Of High-Aspect-Ratio Diffusive Micro-Mixers, Vamsidhar Palaparthy
LSU Master's Theses
In the Ligase Detection Reaction (LDR) technique different chemical reagents of varying concentration are mixed with the by-products of the polymerase chain reaction (PCR) for the detection of low abundant cancer diagnostic markers [1]. An effective micro-mixer which is cheap, durable over a relatively broad range of flows with easy manufacturing is required in this process. This work is aimed at manufacturing mixers according to the required specifications with metrology at every manufacturing process to estimate the limits and tolerances during manufacturing and analyzing their efficiency both numerically and experimentally. An optimum mixer design developed earlier by Maha et.al [2] …
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 …
Granular Contact Lubrication: Theory And Experiment, Karim El Kholy
Granular Contact Lubrication: Theory And Experiment, Karim El Kholy
LSU Doctoral Dissertations
This dissertation is devoted to a theoretical and experimental study of the granular contact lubrication, both. The theory is based on the kinetic of the granular material where the granules interact with each other and with the boundary surfaces through instantaneous, binary collisions, characterized by a constant coefficient of restitution. Specifically this study focuses on granular lubrication in Couette flows. A series of simulations is reported and the results show good agreement with several published papers. Also, a theory that ties the true temperature to the grain mobility is developed. The true temperature of a granular material depends on the …
Design, Fabricaton, And Testing Of A Compact Quasi-Isothermal Prox Reactor Using Micro Heat Exchangers, Curtis Maurice Hebert
Design, Fabricaton, And Testing Of A Compact Quasi-Isothermal Prox Reactor Using Micro Heat Exchangers, Curtis Maurice Hebert
LSU Master's Theses
A two stage PROX reactor with micro heat exchangers was designed, built, and tested to demonstrate the ability to control the temperature in the reactor and improve PROX performance in terms of CO conversion and selectivity. The gas stream was composed of 40% H2, 1% CO, 9% CO2, 0.5% O2, and 49.5% Ar. Metal foams were used to support a 5 wt% Pt/0.5 wt% Fe/γ-Al2O3 catalyst. Two sections of foam catalyst were used with heat exchangers positioned before and after each section. The resulting axial temperature profile of the gas stream …
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, …
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 …
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 …
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 …
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 …
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 …
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 …
Eigenvalue Optimization And Its Applications In Buckling And Vibration, Srinivas Gopal Krishna
Eigenvalue Optimization And Its Applications In Buckling And Vibration, Srinivas Gopal Krishna
LSU Doctoral Dissertations
Eigenvalue problems are of immense interest and play a pivotal role not only in many fields of engineering but also in pure and applied mathematics. An in-depth understanding of this class of problems is a pre-requisite for vibration and buckling analyses of structures. Design optimization of structures to prevent failure due to instability (bucking) and vibration introduces the problem of determining optimal physical parameters such that load carrying capacity or the fundamental natural frequency is maximized. A classical example of such problems is the Lagrange problem of determining the shape of the strongest column against buckling. The primary objective of …