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Mechanical Engineering Commons™

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2008

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Articles 541 - 567 of 567

Full-Text Articles in Mechanical Engineering

Analysis Of The Effects Of The Residual Charge And Gap Size On Electrospun Nanofiber Alignment In A Gap Method, Lihua Liu, Yuris A. Dzenis Jan 2008

Analysis Of The Effects Of The Residual Charge And Gap Size On Electrospun Nanofiber Alignment In A Gap Method, Lihua Liu, Yuris A. Dzenis

Department of Engineering Mechanics: Faculty Publications

In this paper, the effects of residual charges on nanofiber alignment in a gap method are studied and presented. The gap method was presented by Li and Xia (2003 Nano Lett. 3 1167); in it, a gap is introduced into a traditional collector. Due to the non-perfect conductivity of electrospun nanofibers, they carry residual charges after deposition across the gap. These residual charges will interact with the charges carried by the upcoming jet/fiber, that will also deposit across the gap. The effects of these charge interactions on nanofiber alignment were studied numerically at various gap sizes. Results showed that alignments …

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Numerical Simulation Of A Novel Blast Wave Mitigation Device, Zhenbi Su, Wen Peng, Zhaoyan Zhang, George Gogos, Reed Skaggs, Bryan Cheeseman Jan 2008

Numerical Simulation Of A Novel Blast Wave Mitigation Device, Zhenbi Su, Wen Peng, Zhaoyan Zhang, George Gogos, Reed Skaggs, Bryan Cheeseman

Department of Mechanical and Materials Engineering: Faculty Publications

This paper proposes a novel blast wave mitigation device, consisting of a piston–cylinder assembly. A shock wave is induced inside the device when it is subject to a blast wave. The shock wave propagates inside the device and is reflected repeatedly. The physical processes within the blast wave mitigation device are simulated numerically. Numerical predictions are in excellent agreement with analytical solutions for special cases of the investigated problem that are available in the literature. The peak pressure on the base of the device caused by the blast wave is studied using a number of design parameters. The numerical simulation …

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Efficient Uncertainty Quantification Applied To The Aeroelastic Analysis Of A Transonic Wing, Serhat Hosder, Robert W. Walters, Michael Balch Jan 2008

Efficient Uncertainty Quantification Applied To The Aeroelastic Analysis Of A Transonic Wing, Serhat Hosder, Robert W. Walters, Michael Balch

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The application of a Point-Collocation Non-Intrusive Polynomial Chaos method to the uncertainty quantification of a stochastic transonic aeroelastic wing problem has been demonstrated. The variation in the transient response of the first aeroelastic mode of a three-dimensional wing in transonic flow due to the uncertainty in free-stream Mach number and angle of attack was studied. A curve-fitting procedure was used to obtain time-independent parameterization of the transient aeroelastic responses. Among the uncertain parameters that characterize the time-dependent transients, the damping factor was chosen for uncertainty quantification, since this parameter can be thought as an indicator for flutter. Along with the …

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An Integrated Framework For Applying Lean Manufacturing And Other Strategies In Mass Customization Environments, Gregory Brandon Stump Jan 2008

An Integrated Framework For Applying Lean Manufacturing And Other Strategies In Mass Customization Environments, Gregory Brandon Stump

University of Kentucky Master's Theses

Manufacturing organizations are facing fragmented markets and increased demand of variety from consumers. As a result, many of these firms have adopted mass customization manufacturing strategies in an effort to offer their customers the freedom of choice while maintaining operational efficiency. Lean manufacturing strategies have also seen heavy use in manufacturing environments. This study investigates the possibilities of integrating lean manufacturing principles and practices into mass customization environments in order to improve system performance. The feasibility of other manufacturing strategies such as agility, Quick Response Manufacturing and the Theory of Constraints assisting in the application of lean manufacturing for mass …

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Virtual Prototyping With Surface Reconstruction And Freeform Geometric Modeling Using Level-Set Method, Weihan Zhang Jan 2008

Virtual Prototyping With Surface Reconstruction And Freeform Geometric Modeling Using Level-Set Method, Weihan Zhang

Doctoral Dissertations

"More and more products with complex geometries are being designed and manufactured by computer aided design (CAD) and rapid prototyping (RP) technologies. Freeform surface is a geometrical feature widely used in modern products like car bodies, airfoils and turbine blades as well as in aesthetic artifacts. How to efficiently design and generate digital prototypes with freeform surfaces is an important issue in CAD. This paper presents the development of a Virtual Sculpting system and addresses the issues of surface reconstruction from dexel data structures and freeform geometric modeling using the level-set method from distance field structure. Our virtual sculpting method …

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Modeling, Analysis And Experimentation For Building Ice Parts With Supports Using Rapid Freeze Prototyping, Frances D. Bryant Jan 2008

Modeling, Analysis And Experimentation For Building Ice Parts With Supports Using Rapid Freeze Prototyping, Frances D. Bryant

Doctoral Dissertations

"Rapid Freeze Prototyping (RFP) is a freeform fabrication method that freezes water droplets into ice in a layer-by-layer manner to additively create a 3-dimensional part. Each layer of a geometry is deposited and allowed to freeze before the next layer is added. Ice parts produced by RFP can be used in investment casting to replace wax patterns and in other applications which may benefit from the unconventional method of using ice as a pattern or mold. More recently, a sacrificial support material has been incorporated into RFP so that over-hung areas and complex geometries can be fabricated. The research presented …

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Experimental Investigation Of Active Control Of Bluff Body Vortex Shedding, Ilteris Koc Jan 2008

Experimental Investigation Of Active Control Of Bluff Body Vortex Shedding, Ilteris Koc

Mechanical & Aerospace Engineering Theses & Dissertations

Mean and fluctuating forces acting on a body are strongly related to vortex shedding generated behind it. Therefore, it is possible to obtain substantial reductions of at least the unsteady forces if vortex shedding is controlled or its regularity is reduced. While conventional active flow control methods are mainly concerned with direct interaction with, and alteration of, the mean flow about a body, modern techniques involve altering existing flow instabilities using relatively small inputs to obtain large-scale changes of mean flows. Aerodynamic flow control may be intended to delay or suppress boundary layer separation through creation of a boundary layer …

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Phase Change Cooling Applications - Engine Cooling, Kiran Kumar Katta Jan 2008

Phase Change Cooling Applications - Engine Cooling, Kiran Kumar Katta

Open Access Theses & Dissertations

Waste heat recovery system composed of two phase cooling system, exhaust heat exchanger, and mini-turbine has been proposed by Henry Works, Inc to generate auxiliary power via harvesting engine cooling and exhaust heat loss from heavy duty vehicles. The objective of this research is to evaluate the two phase cooling system through the engine dynamometer test and obtain initial test data for the development of the waste heat recovery system. Engine dynamometer experiment for evaluating two phase cooling has been conducted using Perkins diesel engine. During two phase cooling phase, the coolant temperature showed less than 1 °C variation in …

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An Integrated Simulation Design With Three-Dimensional Motions And A Hydraulic Stewart Simulator, Cheng Lin, Gene Hou, Yuzhong Shen, Hector Garcia Jan 2008

An Integrated Simulation Design With Three-Dimensional Motions And A Hydraulic Stewart Simulator, Cheng Lin, Gene Hou, Yuzhong Shen, Hector Garcia

Engineering Technology Faculty Publications

This paper presents an integrated design process and tests of a Stewart simulator with a virtual visualization tool, which uses Virtools to create and generate three-dimensional motions. An inverse kinematic algorithm is written to convert each visualized motion to the displacements of six cylinders in a Stewart motion simulator. Information of the displacements is then transferred through the User Datagram Protocol (UDP) to a personal computer which has the LabVIEW software. An NI USB-6251 data acquisition device is applied to interact with the LabVIEW program and the Stewart hydraulic simulator. The approach presented in this paper to function an old …

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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 (ìEDM) 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 …

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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 …

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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 …

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A New Method Of Synthesizing Black Birnessite Nanoparticles: From Brown To Black Birnessite With Nanostructures, Marcos A. Cheney, Pradip K. Bhowmik, Shizhi Qian, Sang W. Joo, Wensheng Hou, Joseph M. Okoh Jan 2008

A New Method Of Synthesizing Black Birnessite Nanoparticles: From Brown To Black Birnessite With Nanostructures, Marcos A. Cheney, Pradip K. Bhowmik, Shizhi Qian, Sang W. Joo, Wensheng Hou, Joseph M. Okoh

Mechanical & Aerospace Engineering Faculty Publications

A new method for preparing black birnessite nanoparticles is introduced. The initial synthesis process resembles the classical McKenzie method of preparing brown birnessite except for slower cooling and closing the system from the ambient air. Subsequent process, including wet-aging at 7° C for 48 hours, overnight freezing, and lyophilization, is shown to convert the brown birnessite into black birnessite with complex nanomorphology with folded sheets and spirals. Characterization of the product is performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), and N(2) adsorption ( BET) techniques. Wet-aging and lyophilization times are …

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Development And Validation Of A Dynamic Model Of The Maglev Transportation System At Old Dominion University, Ajinkya Deodhar, Sebastian Bawab, Aravind Hanasoge Jan 2008

Development And Validation Of A Dynamic Model Of The Maglev Transportation System At Old Dominion University, Ajinkya Deodhar, Sebastian Bawab, Aravind Hanasoge

Mechanical & Aerospace Engineering Faculty Publications

A dynamic model of the vehicle/guideway coupled with a controller is developed for the maglev demonstration system currently being developed at ODU, using the MAthematical DYnamic MOdeling software - MADYMO. The fundamental characteristics of the vehicle and guideway are obtained from detailed finite element analyses using MSC-NASTRAN. As a result, the vehicle is modeled in MADYMO as a 21- degree-of-freedom spring-mass-damper system. A three span concrete guideway is modeled using 3D solid Hex8 elements. The air gap is modeled as a penetration of the magnets into the guideway. Decentralized colocated PD controllers are used for controlling the penetration of each …

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Comparison Of Roadside Crash Injury Metrics Using Event Data Recorders, Doug Gabauer, Hampton C. Gabler Jan 2008

Comparison Of Roadside Crash Injury Metrics Using Event Data Recorders, Doug Gabauer, Hampton C. Gabler

Faculty Journal Articles

The occupant impact velocity (OIV) and acceleration severity index (ASI) are competing measures of crash severity used to assess occupant injury risk in full-scale crash tests involving roadside safety hardware, e.g. guardrail. Delta-V, or the maximum change in vehicle velocity, is the traditional metric of crash severity for real world crashes. This study compares the ability of the OIV, ASI, and delta-V to discriminate between serious and non-serious occupant injury in real world frontal collisions. Vehicle kinematics data from event data recorders (EDRs) were matched with detailed occupant injury information for 180 real world crashes. Cumulative probability of injury risk …

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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 …

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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 cycles, …

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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 …

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Investigation Of Blast Mitigation Properties Of Carbon And Polyurethane Based Foams, Bradley E. Toon Jan 2008

Investigation Of Blast Mitigation Properties Of Carbon And Polyurethane Based Foams, Bradley E. Toon

University of Kentucky Master's Theses

Solid foams have been studied for years for their ability to mitigate damage from sudden impact. Small explosive attacks threaten to damage or destroy key structures in some parts of the world. A newly developed material, carbon foam, may offer the ability to mitigate the effects of such blasts. This project investigates the energy absorbing properties of carbon and polyurethane based foams in dynamic compression to illustrate their viability to protect concrete structures from the damaging effects of pressure waves from a small blast. Cellular solid mechanics fundamentals and a survey of the microscopic cellular structure of each type of …

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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 …

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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 testing. Foams …

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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 …

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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 …

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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 …

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Performance Optimization Of A Structured Cfd Code - Ghost On Commodity Cluster Architectures, Pavan K. Kristipati Jan 2008

Performance Optimization Of A Structured Cfd Code - Ghost On Commodity Cluster Architectures, Pavan K. Kristipati

University of Kentucky Master's Theses

This thesis focuses on optimizing the performance of an in-house, structured, 2D CFD code – GHOST, on commodity cluster architectures. The basic philosophy of the work is to optimize the cache usage of the code by implementing efficient coding techniques without changing the underlying numerical algorithm. Various optimization techniques that were implemented and the resulting changes in performance have been presented. Two techniques, external and internal blocking that were implemented earlier to tune the performance of this code have been reviewed. What follows is further tuning effort in order to circumvent the problems associated with using the blocking techniques. Later, …

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Elastic-Plastic Indentation Deformation In Homogeneous And Layered Materials: Finite Element Analysis, Siva Naga Venkata Ravi Kiran Kurapati Jan 2008

Elastic-Plastic Indentation Deformation In Homogeneous And Layered Materials: Finite Element Analysis, Siva Naga Venkata Ravi Kiran Kurapati

University of Kentucky Master's Theses

The complex phenomenon of indentation deformation is studied using finite element analysis for both homogeneous and layered materials. For the homogeneous materials, the elastic-plastic deformation at large indentation depth is studied. The variation of the load-displacement curves as well as the variation of the energy ratio with the applied indentation depth for different strain hardening indices is presented. The power law relation between the indentation load and depth for shallow indentation becomes invalid for deep indentation. The ratio of plastic energy to total mechanical work is a linear function of the ratio of residual indentation depth and maximum indentation depth. …

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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 …

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