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Full-Text Articles in Mechanical Engineering

Quasi-Static And Impact Characterization Of Sandwich Structures With An Iso-Grid Stiffened Syntactic Foam Core, Venkata Sandeep Chakka Jan 2008

Quasi-Static And Impact Characterization Of Sandwich Structures With An Iso-Grid Stiffened Syntactic Foam Core, Venkata Sandeep Chakka

LSU Master's Theses

In this study, a novel hybrid sandwich structure with an integrated, iso-grid stiffened syntactic foam core was fabricated and evaluated by impact test and static test. Sandwich beams with different grid cell areas were prepared using a pin-guided dry weaving process. Low velocity impact test on different locations (rib, node, and bay) was conducted with varying hammer weight and impact velocities by an instrumented impact testing machine. Ultrasonic C-scan was utilized before and after impact to identify the damage induced by impact. Scanning Electron Microscopy observation was also implemented to visualize the impact damage at micro- length scale. Compressions after ...


Numerical Simulations Of Flow And Mass Transport In Micro-Fluidic Components For Modular Bio-Analytic Chip Applications, Sudheer D. Rani Jan 2008

Numerical Simulations Of Flow And Mass Transport In Micro-Fluidic Components For Modular Bio-Analytic Chip Applications, Sudheer D. Rani

LSU Doctoral Dissertations

Microfluidics has received a great deal of attention in the past decade. The ability of modular microfluidic chips to miniaturize integrate chemical and biological systems (┬ÁTAS) can be greatly productive in terms of cost and efficiency. During the design of these modular devices, misalignment of materials, geometrical or both is one of the most common problems. These misalignments can have adverse effect in both pressure driven and electrokinetically driven flows. In the present work, Numerical Simulations have been performed to study the effect of material and geometrical mismatch on the flow behavior and species progression in microfluidic interconnects. In the ...


Nanoclay Reinforced Polymer Composite And Its Application To Hybrid Composite Structures, Gefu Ji Jan 2008

Nanoclay Reinforced Polymer Composite And Its Application To Hybrid Composite Structures, Gefu Ji

LSU Master's Theses

The purpose of this study was to find the optimum mixing technique that leads to maximum gain in mechanical, thermal, and fire-retardant properties of vinyl ester based nanocomposites. Specifically, five combinations of incremental mixing intensity were applied to five groups of samples that were made of vinyl ester resin reinforced by 1 wt. % of montmorillonite (MMT). Changes in mechanical properties associated with each mixing combination were examined through a variety of tests, which were low velocity impact test, bending test, compression test, and dynamic mechanical analysis (DMA). Additionally, changes in thermal properties (e.g., thermal diffusivity, glass transition temperature) and ...


Experimental And Numerical Investigation Of Fluid Flow And Heat Transfer In Microchannels, Wynn Allen Phillips Jan 2008

Experimental And Numerical Investigation Of Fluid Flow And Heat Transfer In Microchannels, Wynn Allen Phillips

LSU Master's Theses

Microchannels are of current interest for use in heat exchangers where very high heat transfer performance is desired. Microchannels provide very high heat transfer coefficients because of their small hydraulic diameters. In this study, an investigation of fluid flow and heat transfer in microchannels is conducted. A review of the literature published regarding fluid flow and heat transfer in microchannels is provided in this study. A thorough background on the theory of internal convective heat transfer is provided as well. A critical analysis of some of the published heat transfer experiments on microchannels is also given. It was found that ...


Magnetic Field Effects On Diffusion Flames, Diego F. Gonzalez Jan 2008

Magnetic Field Effects On Diffusion Flames, Diego F. Gonzalez

LSU Master's Theses

Magnetic field effects in combustion is an area of study that has previously been overlooked. The influence of magnetic fields on flames has only recently been explored and is of interest both from a scientific and a practical standpoint. This study provides theoretical, numerical and experimental evidence that combustion can be affected with the use of suitable magnetic fields. This thesis focuses on four different types of magnetic field: homogeneous, gradient, oscillating and pre-combustion. For the homogeneous field case, the Gibbs Free Energy method was used to determine the mole fraction of product species. It was found that homogeneous fields ...


Microassembly Technology For Modular, Polymer Microfluidic Devices, Byoung Hee You Jan 2008

Microassembly Technology For Modular, Polymer Microfluidic Devices, Byoung Hee You

LSU Doctoral Dissertations

Assembly of modular, polymer microfluidic devices with different functions to obtain more capable instruments may significantly expand the options available for detection and diagnosis of disease through DNA analysis and proteomics. For connecting modular devices, precise, passive alignment structures can be used to prevent infinitesimal motions between the devices and minimize misalignment. The motion and constraint of passive alignment structures were analyzed using screw theory. A combination of three v-groove and hemisphere-tipped post joints constrained all degrees of freedom of the two mating modules without overconstraint. Simulations and experiments were performed to assess the predictability of dimensional and location variations ...


Thermomechanical Interaction Analysis Of Bodies Subjected To Oscillatory Heat Source, Jun Wen Jan 2008

Thermomechanical Interaction Analysis Of Bodies Subjected To Oscillatory Heat Source, Jun Wen

LSU Doctoral Dissertations

Surface heating by application of a moving heat source is a common problem in most manufacturing processes as well as in many tribological applications. The existing literature on studies of moving heat source problems primarily concentrates on unidirectional moving heat sources. Yet, a more complete analysis requires understanding of thermal behavior of bodies in relative sliding contacts subjected to oscillatory heat sources and thermomechanical interaction. In this dissertation, two analytical models are developed for rapid evaluation of the transient temperature in solids undergoing oscillatory heat source. In the first model, an analytical technique is presented to treat oscillatory heat source ...


Replication Of Metal-Based Microscale Structures By Compression Molding: A Combined Experimental And Finite Element Analysis Study, Jing Jiang Jan 2008

Replication Of Metal-Based Microscale Structures By Compression Molding: A Combined Experimental And Finite Element Analysis Study, Jing Jiang

LSU Doctoral Dissertations

Fabrication of microscale Ta mold inserts by micro-electrical-discharge-machining (├ČEDM) is reported. Morphology, chemistry, and structure of the near-surface region of as-machined Ta blanks have been characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. A TaC surface layer forms on as-machined Ta surfaces. This altered surface layer was removed by electro-chemical-polishing. Further modification of Ta insert surfaces was accomplished by deposition of a conformal Ti-containing hydrogenated carbon coating. We demonstrate successful replication of high-aspect-ratio microscale structures (HARMS) in Al and Cu by compression molding with such surface-engineered Ta mold inserts. In addition, a hybrid microfabrication technique, combining ...


Cryopreservation Of Adipose Derived Adult Stem Cells And Multidimensional Cell Sheets, Sreedhar Thirumala Jan 2008

Cryopreservation Of Adipose Derived Adult Stem Cells And Multidimensional Cell Sheets, Sreedhar Thirumala

LSU Doctoral Dissertations

Human adipose tissue provides a uniquely abundant and accessible source of adult stem cells. In response to chemical, hormonal or structural stimuli, these human adipose-derived adult stem (ASCs) cells can differentiate along multiple lineage pathways, including adipocytes, chondrocytes, myocytes, neurons and osteoblasts. Successful cryopreservation of scientifically and commercially important ASCs would revolutionize the tissue engineering and regenerative medicine industry. In this research, we have investigated the water transport phenomenon during freezing of several passages of adipose derived adult stem cells and generated the membrane permeability parameters in the presence and absence of cryoprotective agents. These measured permeability parameters were then ...


An Investigation Into Fuel Cells And Flow Cytometers Optimal Design, Etim Sunday Udoetok Jan 2008

An Investigation Into Fuel Cells And Flow Cytometers Optimal Design, Etim Sunday Udoetok

LSU Doctoral Dissertations

The aim of the fuel cells part of this project was to investigate the performance of Proton Exchange Membrane Fuel Cells and closely related fuel cell types like the Alkaline Fuel Cells and Phosphoric Acid Fuel Cells. The investigation involved understanding the performance of fuel cells, addressing the shortcomings of currently used designs, and finding new methods for improving the performance of fuel cells. CFD was used to study flow channels and information learned from the study was used to design a new and improved flow channel. A prototype of the new design was fabricated, tested and found to perform ...


Parametric Study Of A Pulsed Vertical Jet In Cross-Flow, Guillaume Francois Bidan Jan 2008

Parametric Study Of A Pulsed Vertical Jet In Cross-Flow, Guillaume Francois Bidan

LSU Master's Theses

The potential of pulsed vertical jet in cross-flow for film cooling purposes was experimentally studied and is discussed in this Thesis. A single vertical jet placed in laminar cross-flow conditions was first characterized in steady state at relatively low blowing ratios ranging from 0.150 to 0.600, using Mie scattering visualization methods and hot-wire measurements. Wavelet spectral analysis and image quantification algorithms were applied to the velocity records and averaged visualizations to obtain quantitative data on the jet characteristic frequencies, penetration and coverage. Two different regimes characterized by different structures are identified and adapted scaling variables are provided. Trends ...


Design And Realization Of An Electrophoretron Cycler, Celine Raymonde Ramet Jan 2008

Design And Realization Of An Electrophoretron Cycler, Celine Raymonde Ramet

LSU Master's Theses

Polymerase Chain Reaction (PCR) is a powerful enzymatic reaction commonly used to amplify specific sequences of Deoxyribo Nucleic Acid (DNA). Since the introduction of the lab on a chip concept, numerous Continuous Flow PCR cyclers were realized with success at the micro scale. As reducing the reactor size and improving thermal management led to reduced sample volumes, results could be achieved much faster with these CF-PCR cyclers than with common commercial cycler. Furthermore, most of these demonstrated CF-PCRs are nowadays evolving towards high-throughput systems. However, most CF-PCR cyclers require complex manipulations and are not flexible (e.g. fixed number of ...


Design, Fabrication, And Testing Of A Micro Fuel Injection Swirler For Lean Premixed Combustion In Gas Turbine Engines, Anthony Louis Giglio Jan 2008

Design, Fabrication, And Testing Of A Micro Fuel Injection Swirler For Lean Premixed Combustion In Gas Turbine Engines, Anthony Louis Giglio

LSU Master's Theses

Due to growing energy demands and the need for increased fuel consumption efficiency, environmental protection agencies are imposing more stringent emissions regulations on gas turbine combustion systems with emphasis on NOx emissions reduction. Emerging technological combustion schemes to reduce NOx commonly employ lean premixed combustion. Decreases in NOx are globally obtained by flame temperature decrease and locally improved by homogeneity of the reacting mixture. A new micro fuel injection swirler, capable of providing efficient and rapid mixing over a short distance, is presented in this thesis. The conception of the Micro Fuel Injection Swirler (MFIS) was motivated by the need ...


High Strain Rate Characteristics Of Rubber Modified Syntactic Foams, Paul Wehmer Jan 2008

High Strain Rate Characteristics Of Rubber Modified Syntactic Foams, Paul Wehmer

LSU Master's Theses

This thesis deals with the characterization of hybrid syntactic foams under high strain rates (HSR) ranging from 450/s to 1000/s. The foams studied are comprised of epoxy resin matrix filled with 63% volume fraction glass microspheres and 2% volume fraction of ground rubber fragments. The focus of this study is to compare the strength, ultimate strain, and modulus of these composite materials at high strain rates and quasi-static conditions and to find out the effects of HSR on the failure mode and fracture behavior of these materials. Split Hopkinson Pressure Bar (SHPB) apparatus is used for the HSR ...


Analysis Of Gas Dynamic Waves In Explosively Actuated Valves, Blaise H. Paul Jan 2008

Analysis Of Gas Dynamic Waves In Explosively Actuated Valves, Blaise H. Paul

LSU Master's Theses

A mathematical model is formulated for assessing quasi-one-dimensional gas dynamics occurring within axis-symmetric explosively actuated valves. The model describes complete valve operation and accounts for pressure-dependent explosive combustion within an actuator, compressible product gas flow within the actuator, through a small port, and into and within a gas expansion chamber. The gas dynamic waves induce piston motion at the terminal end of the expansion chamber which is needed for valve operation. The model is mathematically posed as an initial-boundary-value problem in terms of generalized coordinates to facilitate numerical computations on a domain that volumetrically expands due to combustion and piston ...


Nanoclay Syntactic Foam Composites, Sameer Leo Peter Jan 2008

Nanoclay Syntactic Foam Composites, Sameer Leo Peter

LSU Master's Theses

Syntactic foams are composite materials in which the matrix phase is reinforced with hollow particles called microballoons. They possess low moisture absorption, low thermal conductivity and high damage tolerance because of their compositions. Traditionally, syntactic foams are used in many high strength applications such as in aerospace and marine industries, thus there is a need to achieve both high compressive strength and high fracture strain with minimal increase in density. This research studies the effect of nanoclay on the high strain rate mechanical properties of syntactic foams. Nanoclay reinforced syntactic foams are fabricated by adding 1, 2 and 5% volume ...


Freezing Processes In Cell Suspensions Evaluated Using Cryomicroscopy, Tathagata Acharya Jan 2008

Freezing Processes In Cell Suspensions Evaluated Using Cryomicroscopy, Tathagata Acharya

LSU Master's Theses

This thesis aims at evaluating the freezing response of three different cell types, Pacific Oyster embryos, Jurkats and Helas, using the technique of cryomicroscopy. The choice of cells was primarily based on supporting ongoing research work at the Bioengineering Laboratory, Department of Mechanical Engineering at Louisiana State University in Baton Rouge. On a secondary basis, the cells were chosen based on their contrasting nature. While Pacific Oyster being a favorite food in USA calls for successful techniques of cryopreservation of their embryos in order to keep up with the growing demand, Jurkat and HeLa are undesired malignant human cells that ...


Fabrication Of Micro Bumps For Micro Scale Thermal Management, Ajay Ashok Kardak Jan 2008

Fabrication Of Micro Bumps For Micro Scale Thermal Management, Ajay Ashok Kardak

LSU Master's Theses

Cryopreservation is storage of biological systems at ultra low temperatures for a prolonged duration; such that they can be thawed and restored to the same living state. It is important to understand the behavior of cells when they are subjected to subzero temperatures. Research in this area has shown the occurrence of two main biophysical events; cellular dehydration and intracellular ice formation. Current techniques for characterizing the dehydration in cells as part of a tissue are not adequate for studying intracellular ice formation in tissues. An integrated device consisting of an array of thermal sensors (microthermocouples) and actuators (microthermoelectric coolers ...