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Mechanical Engineering Commons™

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2007

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Articles 451 - 467 of 467

Full-Text Articles in Mechanical Engineering

Study Of Demolding Process In Thermal Imprint Lithography Via Numerical Simulation And Experimental Approaches, Zhichao Song Jan 2007

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, …

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Passive Alignment Of Micro-Fluidic Chips Using The Principle Of Elastic Averaging, Sitanshu Gurung Jan 2007

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 …

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Studies On The Heat/Mass Transfer Characteristics And Fluid Structure In A Square Internal Cooling Channel With Dimpled Surfaces, Fuguo Zhou Jan 2007

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 …

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Fabrication Of Perforated Polymer Membranes Using Imprinting Technology, Anish Roychowdhury Jan 2007

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 …

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Experimental Investigation Of Heat Transfer Rate In Micro-Channels, Pritish Ranjan Parida Jan 2007

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 …

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Film Cooling From A Row Of Holes Supplemented With Anti Vortex Holes, Alok Dhungel Jan 2007

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 …

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Transcendental Eigenvalue Problems Associated With Vibration, Buckling And Control, Jayaram Subramanian Jan 2007

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 …

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On The Stress Analysis Of Bimetallic Packing Rings, Eric Richard Lewis Jan 2007

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 …

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Micro Injection Fuel/Air Premixer/Combustion, Jian Zhang Jan 2007

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. …

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Granular Contact Lubrication: Theory And Experiment, Karim El Kholy Jan 2007

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 …

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Flow Field And Heat Transfer Analyses Of Mechanical Seals, Zhaogao Luan Jan 2007

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 …

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Turbulence Modeling For Film Cooling Flows, Asif Hoda Jan 2007

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 …

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Reactive Multilayer Foils And Their Applications In Joining, Xiaotun Qiu Jan 2007

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 …

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Measuring Skeletal Kinematics With Accelerometers On The Skin Surface, Kevin Curtis Ayer Jan 2007

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 …

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Characterization And Flow Physics Of Plasma Synthetic Jet Actuators, Arvind Santhanakrishnan Jan 2007

Characterization And Flow Physics Of Plasma Synthetic Jet Actuators, Arvind Santhanakrishnan

University of Kentucky Doctoral Dissertations

Plasma synthetic jet actuators are investigated experimentally, in which the geometrical design of single dielectric barrier discharge (SDBD) plasma actuators is modified to produce zero-mass flux jets similar to those created by mechanical devices. The SDBD plasma actuator consists of two rectangular electrodes oriented asymmetrically and separated by a layer of dielectric material. Under an input of high voltage, high frequency AC or pulsed DC, a region of plasma is created in the interfacial air gap on account of electrical breakdown of the ambient air. A coupling between the electric field in the plasma and the neutral air near the …

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Capacitance Metrology Of Curved Surfaces: Study And Characterization Of A Novel Probe Design, Philip T. Smith Jr. Jan 2007

Capacitance Metrology Of Curved Surfaces: Study And Characterization Of A Novel Probe Design, Philip T. Smith Jr.

University of Kentucky Doctoral Dissertations

Capacitive sensors are frequently applied to curved target surfaces for precision displacement measurements. In most cases, these sensors have not been recalibrated to take the curvature of the target into consideration. This recalibration becomes more critical as the target surface becomes smaller in comparison to the sensor. Calibration data are presented for a variety of capacitance probe sizes with widely varying geometries. One target surface particularly difficult to characterize is the inner surface of small holes, less than one millimeter in diameter. Although contact probes can successfully measure the inner surface of a hole, these probes are often fragile and …

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Compliant High-Precision E-Quintet Ratcheting (Cheqr) Mechanism For Safety And Arming Devices, John A. Kennedy, Larry L. Howell, William Greenwood Jan 2007

Compliant High-Precision E-Quintet Ratcheting (Cheqr) Mechanism For Safety And Arming Devices, John A. Kennedy, Larry L. Howell, William Greenwood

Faculty Publications

Ratchet and pawl mechanisms are used in safety applications to provide mechanical isolation between inputs and an output to insure that extreme environmental conditions do not inadvertently allow an unexpected output. These devices have become smaller and are approaching a size regime where traditional precision components, such as precision bearings and springs, are not available. This paper introduces the Compliant High-precision E-Quintet Ratcheting (CHEQR) mechanism as a means of exploiting the advantages of compliant mechanisms to create safety devices that eliminate the need for bearings and springs. The pseudo-rigid-body model was used to design a mechanism with the desired force-deflection …

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