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Articles 1 - 27 of 27
Full-Text Articles in Mechanical Engineering
Short-Term Failure Analysis Of Aluminum Conducting Composite Core Transmission Lines, Brian Burks
Short-Term Failure Analysis Of Aluminum Conducting Composite Core Transmission Lines, Brian Burks
Electronic Theses and Dissertations
Recently the inefficiency and lack of capabilities of electric energy transmission have been put in the global spotlight; a transmission line design known as the Aluminum Conducting Composite Core Trapezoidal Wire (ACCC/TWTM) attempts to eliminate the deficiencies. The ACCC core is comprised of a new hybrid composite material. The most probable causes of short-term damage to the ACCC core were investigated through a series of finite element models. It was found that excessive bending was the most likely cause of short-term damage to the core. During bending of the ACCC core, stresses are concentrated at the interface in …
Development Of An Integrated Solar Heat Pipe System For Improving Building Energy Efficiency., Michael Vincent Albanese
Development Of An Integrated Solar Heat Pipe System For Improving Building Energy Efficiency., Michael Vincent Albanese
Electronic Theses and Dissertations
The one dimensional heat transfer, thermal diode effect of heat pipes makes them ideal for passive solar applications. Gains in a heat pipe passive solar wall are not lost during cloud cover or periods of low irradiation. An experimental model was built to test the performance of a heat pipe passive solar wall in a laboratory setting. Experimental variations included varying fluid fill levels and the addition of insulation along the adiabatic section of the heat pipe. Filling the heat pipe to 120% volume of the evaporator section and insulating the adiabatic section achieved efficiencies of 85%. The average rate …
Flow Visualization In Microfluidic Expansion And Mixing, Ehsan Yakhshi-Tafti
Flow Visualization In Microfluidic Expansion And Mixing, Ehsan Yakhshi-Tafti
Electronic Theses and Dissertations
Micro particle image velocimetry (microPIV) is a non-intrusive tool for visualizing flow in micron-scale conduits. Using this investigative instrument, two experimental studies were performed to understand flow behaviors in microfluidic channels - a sudden expansion step flow and laminar velocity profile variation in diffusion driven mixing. First, flow in a backward facing step feature (1:5 expansion ratio) in a microchannel was taken as the subject of microPIV flow visualization. The onset and development of a recirculation flow was studied as a function of flow rate. This flow pattern was further used to investigate two major parameters affecting microPIV measurements; the …
Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty
Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty
Electronic Theses and Dissertations
Shock-tube experiments were performed with syngas mixtures near atmospheric pressure with varying equivalence ratios behind reflected shock waves. Pressure and hydroxyl radical (OH*) emission traces were recorded and used to calculate ignition delay time for a single mixture at equivalence ratios of [phi ]=0.4, 0.7, 1.0, and 2.0 over a range of temperatures from 913-1803 K. The syngas mixture was tested at full concentration as well as with 98% dilution in Argon. The full concentration mixtures were used to compare ignition delay time measurements with the theoretical calculations obtained through the use of chemical kinetics modeling using the Davis et …
Percolation Study Of Nano-Composite Conductivity Using Monte Carlo Simulationpercolation, Jing Bai
Percolation Study Of Nano-Composite Conductivity Using Monte Carlo Simulationpercolation, Jing Bai
Electronic Theses and Dissertations
A Monte Carlo model is developed for predicting electrical conductivity of carbon nanofiber composite materials. The conductive nanofibers are models as both 2D and 3D network of finite sites that are randomly distributed. The percolation behavior of the network is studied using the Monte Carlo method, which leads to the determination of the percolation threshold. The effect of the nanofiber aspect ratio on the critical nanofiber volume rate is investigated in the current model, each of the nanofibers needs five independent geometrical parameters (i.e., three coordinates in space and two orientation angles) for its identification. There are three controlling parameters …
Structural Analysis And Active Vibration Control Of Tetraform Space Frame For Use In Micro-Scale Machining, Kevin Knipe
Structural Analysis And Active Vibration Control Of Tetraform Space Frame For Use In Micro-Scale Machining, Kevin Knipe
Electronic Theses and Dissertations
This research thesis aims to achieve the structural analysis and active vibration damping of the Tetraform machining structure. The Tetraform is a space frame made up of four equilateral triangles with spherical masses at the four vertices. This frame was originally developed for grinding of optical lenses and is now being adapted for use in micro-precision milling. The Tetraform is beneficial to the milling process due to its exceptionally high dynamic stiffness characteristics, which increases the machining stability and allows for higher material removal rates and accuracy. However, there are still some modes of vibration that are critical to the …
Stress Intensity Factor Dependence Of Hg-Al Liquid Metal Embrittlement, Scott Keller
Stress Intensity Factor Dependence Of Hg-Al Liquid Metal Embrittlement, Scott Keller
Electronic Theses and Dissertations
When high strength aluminum alloys are subjected to liquid metals, physical and chemical reactions ensue resulting in what is known as liquid metal embrittlement (LME). A subset of environmentally-assisted cracking, LME is exhibited when a liquid metal, e.g. Hg or Ga, comes into intimate contact with a solid metal having significant susceptibility. As mechanical loads are applied, the interaction between the two metals results in a reduction in the flow properties of the solid metal. Several theories have been proposed to identify the underlying microstructural failure mechanism; however, none have been widely accepted, as failures can typically incorporate features common …
The Effect Of Heat Transfer Coefficient On High Aspect Ratio Channel Accompanied By Varying Rib Aspect Ratio, An Le
Electronic Theses and Dissertations
Heat transfer and pressure data were performed and reported on two different rigs. The first rig has an aspect ratio of (19:1) with two different inlet conditions and the second rig is composed of two different aspect ratio channels, (1:8) and (1:4). Rib turbulators were used as a flow disruptor scheme to enhance the heat transfer and friction factor. Rib aspect ratios ranging from (1:1) to (1:5) rib-height-to-width ratio were used. The first channel rib-width-to-pitch (Wr/P) ratio was kept at 1/2 where flow was kept at relatively low Reynolds numbers, between 3000 and 13000. Results from the current tests showed …
Tertiary Creep Damage Modeling Of A Transversely Isotropic Ni-Based Superalloy, Calvin Stewart
Tertiary Creep Damage Modeling Of A Transversely Isotropic Ni-Based Superalloy, Calvin Stewart
Electronic Theses and Dissertations
Anisotropic tertiary creep damage formulations have become an increasingly important prediction technique for high temperature components due to drives in the gas turbine industry for increased combustion chamber exit pressures, temperature, and the use of anisotropic materials such as metal matrix composites and directionally-solidified (DS) Ni-base superalloys. Typically, isotropic creep damage formulations are implemented for simple cases involving a uniaxial state of stress; however, these formulations can be further developed for multiaxial states of stress where materials are found to exhibit induced anisotropy. In addition, anisotropic materials necessitate a fully-developed creep strain tensor. This thesis describes the development of a …
Integrated Servomechanism And Process Control For Machining Processes, Yan Tang
Integrated Servomechanism And Process Control For Machining Processes, Yan Tang
Electronic Theses and Dissertations
In this research, the integration of the servomechanism control and process control for machining processes has been studied. As enabling strategies for next generation quality control, process monitoring and open architecture machine tools will be implemented on production floor. This trend brings a new method to implement control algorithm in machining processes. Instead of using separate modules for servomechanism control and process control individually, the integrated controller is proposed in this research to simultaneously achieve goals in servomechanism level and the process level. This research is motivated by the benefits brought by the integration of servomechanism control and process control. …
Characterization Of An Inline Row Impingement Channel For Turbine Blade Cooling Applications, Mark Ricklick
Characterization Of An Inline Row Impingement Channel For Turbine Blade Cooling Applications, Mark Ricklick
Electronic Theses and Dissertations
Gas turbines have become an intricate part of today's society. Besides powering practically all 200,000+ passenger aircraft in use today, they are also a predominate form of power generation when coupled with a generator. The fact that they are highly efficient, and capable of large power to weight ratios, makes gas turbines an ideal solution for many power requirement issues faced today. Designers have even been able to develop small, micro-turbines capable of producing efficient portable power. Part of the turbine's success is the fact that their efficiency levels have continuously risen since their introduction in the early 1800's. Along …
Robust Estimation And Adaptive Guidance For Multiple Uavs' Cooperation, Randal Allen
Robust Estimation And Adaptive Guidance For Multiple Uavs' Cooperation, Randal Allen
Electronic Theses and Dissertations
In this paper, an innovative cooperative navigation method is proposed for multiple Unmanned Air Vehicles (UAVs) based on online target position measurements. These noisy position measurement signals are used to estimate the target's velocity for non-maneuvering targets or the target's velocity and acceleration for maneuvering targets. The estimator's tracking capability is physically constrained due to the target's kinematic limitations and therefore is potentially improvable by designing a higher performance estimator. An H-infinity filter is implemented to increase the robustness of the estimation accuracy. The performance of the robust estimator is compared to a Kalman filter and the results illustrate more …
Molecular Dynamics Study Of Thermal Conductivity Enhancement Of Water Based Nanofluids, Parveen Sachdeva
Molecular Dynamics Study Of Thermal Conductivity Enhancement Of Water Based Nanofluids, Parveen Sachdeva
Electronic Theses and Dissertations
A systematic investigation using molecular dynamics (MD) simulation involving particle volume fraction, size, wettability and system temperature is performed and the effect of these parameters on the thermal conductivity of water based nanofluids is discussed. Nanofluids are a colloidal suspension of 10 -100 nm particles in base fluid. In the last decade, significant research has been done in nanofluids, and thermal conductivity increases in double digits were reported in the literature. This anomalous increase in thermal conductivity cannot be explained by classical theories like Maxwell's model and Hamilton-Crosser model for nanoparticle suspensions. Various mechanisms responsible for thermal conductivity enhancement in …
Design Of Sea Water Heat Exchanger For Miniature Vapor Compression Cycle, James Hughes
Design Of Sea Water Heat Exchanger For Miniature Vapor Compression Cycle, James Hughes
Electronic Theses and Dissertations
Recent advances in the development of miniature vapor compression cycle components have created unique opportunities for heating and cooling applications, specifically to human physiological requirements that arise in extreme environments. Diving in very cold water between 1.7 and 5°C requires active heating because passive thermal insulation has proven inadequate for long durations. To maintain diver mobility and cognitive performance, it is desirable to provide 250 to 300 W of heat from an untethered power source. The use of a miniature vapor compression cycle reduces the amount of power (batteries or fuel cell) that the diver must carry by 2.5 times …
Effect Of Sodium And Absorber Thickness On Cigs2 Thin Film Solar Cells, Parag Vasekar
Effect Of Sodium And Absorber Thickness On Cigs2 Thin Film Solar Cells, Parag Vasekar
Electronic Theses and Dissertations
Chalcopyrites are important contenders among solar cell technologies due to direct band gap and higher absorption coefficient. CuIn1-xGaxS2 (CIGS2) thin-film solar cells are of interest for space power applications because of near optimum bandgap of 1.5 eV for AM0 solar radiation outside the earth's atmosphere. The record efficiency of 11.99% has been achieved on a 2.7 µm CIGS2 thin film prepared by sulfurization at FSEC PV Materials Laboratory. Since CIGS2 films are typically grown in copper-rich regime, excess cuprous sulfide which helps in the formation of CIGS2 is etched away. This makes CIGS2 nearly stoichiometric. However, it is difficult to …
Droplet Flows In Microchannels Using Lattice Boltzmann Method, Amit Gupta
Droplet Flows In Microchannels Using Lattice Boltzmann Method, Amit Gupta
Electronic Theses and Dissertations
Microelectromechanical systems (MEMS) have widespread applications in medical, electronical and mechanical devices. These devices are characterized by the smallest dimension which is at least one micrometer and utmost one millimeter. Rapid progress in the manufacture and utilization of these microdevices has been achieved in the last decade. Current manufacturing techniques of such devices and channels include surface silicon micromachining; bulk silicon micromachining; lithography; electrodeposition and plastic molding; and electrodischarge machining (EDM). In recent years, electrostatic, magnetic, electromagnetic and thermal actuators, valves, gears and diaphragms of dimensions of hundred microns or less have been fabricated successfully. Sensors have been manufactured that …
Study Of Film Cooling Effectiveness: Conical, Trenched And Asymmetrical Shaped Holes, Humberto Zuniga
Study Of Film Cooling Effectiveness: Conical, Trenched And Asymmetrical Shaped Holes, Humberto Zuniga
Electronic Theses and Dissertations
Film cooling is a technique whereby air from the compressor stage of a gas turbine engine is diverted for cooling purposes to parts, such as the turbine stage, that operate at very high temperatures. Cooling arrangements include impingement jets, finned, ribbed and turbulated channels, and rows of film cooling holes, all of which over the years have become progressively more complex. This costly, but necessary complexity is a result of the industry's push to run engines at increasingly higher turbine inlet temperatures. Higher temperatures mean higher efficiency, but they also mean that the turbine first stage operates hundreds of degrees …
A Direct Compensator Profile Optimization Approach For Intensity Modulated Radiation Treatment Planning, Kevin Erhart
A Direct Compensator Profile Optimization Approach For Intensity Modulated Radiation Treatment Planning, Kevin Erhart
Electronic Theses and Dissertations
Radiation therapy accounts for treatment of over one million cancer patients each year in the United States alone, and its use will continue to grow rapidly in the coming years. Recently, many important advancements have been developed that greatly improve the outcomes and effectiveness of this treatment technique, the most notable being Intensity Modulated Radiation Therapy (IMRT). IMRT is a sophisticated treatment technique where the radiation dose is conformed to the tumor volume, thereby sparing nearby healthy tissue from excessive radiation dose. While IMRT is a valuable tool in the planning of radiation treatments, it is not without its difficulties. …
Fuzzy Optimal Swarm Of Autonomous Aircrafts For Target Determination And Convergence Control System, Zach D. Richards
Fuzzy Optimal Swarm Of Autonomous Aircrafts For Target Determination And Convergence Control System, Zach D. Richards
Electronic Theses and Dissertations
The thesis project proposes analytical and theoretical algorithms for a networked swarm of autonomous vehicles, such as those used in planet exploration, and to be used in target location determination and convergence, an algorithm of this type could be used in an Autonomous Stratospheric Aircraft (ASA), thus having the possibility of being used for the exploration of a planet as well as many other applications. Upon locating an unknown location of a specified target, the algorithm would then swarm and eventually converge upon the location. There are two similar, but fundamentally different algorithms proposed in this project. These algorithms are …
Heterogeneous Drive Mechanisms For Novel Locomotion In Rough Terrain, Roy Godzdanker
Heterogeneous Drive Mechanisms For Novel Locomotion In Rough Terrain, Roy Godzdanker
Electronic Theses and Dissertations
The smaller the robot the easier it is for it to access voids in a collapsed structure, however small size brings a host of other problems related to constrained resources. One of the primary constraints on small robots is limited motive power to surmount obstacles and navigate rough terrain. This thesis examines the addition of bulk motive force actuators to existing locomotion platforms and the impact of these heterogeneous actuators on conventional steering methods. The steering methods examined are those associated with skid steered vehicles and differential drive vehicles. In developing the Crabinator, a robot composed of a limbed crawler …
A Drag Estimate For Concept-Stage Ship Design Optimization, Douglas Read
A Drag Estimate For Concept-Stage Ship Design Optimization, Douglas Read
Electronic Theses and Dissertations
During the initial phases of ship design, the naval architect would like to have as much information as possible about the design space. This information not only helps determine a good set of initial characteristics, it allows for informed design changes when reacting to evolving requirements. One of the most difficult performance measures to evaluate is the ship wave drag. This estimate is important in an optimization, because wetted surface and wave drag must be balanced. Multi-parameter optimization algorithms exist, but need a very fast and inexpensive fitness evaluation for them to be effective. Even though linear theory does capture …
Study Of The Effects Of Sodium And Absorber Microstructure For The Development Of Cuin1-Xgaxse2-Ysy Thin Film Solar Cell Using An Alternative Selenium Precursor, Vinaykumar Hadagali
Study Of The Effects Of Sodium And Absorber Microstructure For The Development Of Cuin1-Xgaxse2-Ysy Thin Film Solar Cell Using An Alternative Selenium Precursor, Vinaykumar Hadagali
Electronic Theses and Dissertations
Thin film solar cells have the potential to be an important contributor to the world energy demand in the 21st century. CuInGaSe2 thin film solar cells have achieved the highest efficiency among all the thin film technologies. A steady progress has been made in the research and development of CuInSe2 based thin film solar cells. However, there are many issues that need to be addressed for the development of CuInSe2 based thin films solar cells. High price of PV modules has been a biggest factor impeding the growth of photovoltaic modules for terrestrial application. This thesis tries to address the …
Study Of The Hydrodynamics Of Droplet Impingement On A Dry Surface Using Lattice Boltzmann Method, Xin Gu
Study Of The Hydrodynamics Of Droplet Impingement On A Dry Surface Using Lattice Boltzmann Method, Xin Gu
Electronic Theses and Dissertations
In this work, a two-phase lattice Boltzmann method (LBM) approach is implemented to investigate the hydrodynamic behavior of a single droplet impingement on a dry surface. LBM is a recently developed powerful technique to compute a wide range of fluid flow problems, especially in applications involving interfacial dynamics and complex geometries. Instead of solving the non-linear Navier-Stokes equations, which are complicated partial differential equations, LBM solves a set of discretized linear equations, which are easy to implement and parallelize. The fundamental idea of LBM is to recover the macroscopic properties of the fluid which obeys Navier-Stokes equations, by using simplified …
Pressure Drop And Endwall Heat Transfer Effects Of Porous Turbulators In A Rectangular Channel, Jared Pent
Pressure Drop And Endwall Heat Transfer Effects Of Porous Turbulators In A Rectangular Channel, Jared Pent
Electronic Theses and Dissertations
This study examines the local and averaged endwall heat transfer effects of a staggered array of porous pin fins within a rectangular channel. The porous pin fins were made from aluminum and had a pore density of 10 pores per inch (PPI). The pressure drop through the channel was also determined for several flow rates and presented in terms of the friction factor. Local heat transfer coefficients on the endwall were measured using Thermochromic Liquid Crystal (TLC) sheets recorded with a charge-coupled device (CCD) camera. Static and total pressure measurements were taken at the entrance and exit of the test …
Numerical Study Of Encapsulated Phase Change Material (Epcm) Slurry Flow In Microchannels, Sarada Kuravi
Numerical Study Of Encapsulated Phase Change Material (Epcm) Slurry Flow In Microchannels, Sarada Kuravi
Electronic Theses and Dissertations
Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m …
Computational Studies On The Effective Properties Of Two-Phase Heterogeneous Media, Elyas El Arbi Tawerghi
Computational Studies On The Effective Properties Of Two-Phase Heterogeneous Media, Elyas El Arbi Tawerghi
Electronic Theses and Dissertations
The effective elastic modulus and conductivity of a two phase material system are investigated computationally using a Monte Carlo scheme. The continuum contains circular, spherical or ellipsoidal inclusions that are either uniformly or randomly embedded in the matrix. The computed results are compared to the applicable effective medium theories. It is found that the random distribution, permeability and particle aspect ratio have non-negligible effects on the effective material properties. For spherical inclusions, the effective medium approximations agree well with the simulation results in general, but the analytical predictions on void or non-spherical inclusions are much less reliable. It is found …
Explicit Finite Element Modeling Of Knee Mechanics During Simulated Dynamic Activities, Mark A. Baldwin
Explicit Finite Element Modeling Of Knee Mechanics During Simulated Dynamic Activities, Mark A. Baldwin
Electronic Theses and Dissertations
The natural knee is one of the most commonly injured joints in the body due to relatively high loads and motions that can lead to debilitating degenerative diseases such as osteoarthritis. Total knee arthroplasty is a clinically successful method for eliminating pain in the osteoarthritic knee, but is subject to complications that can affect patient satisfaction and long-term implant performance. The work presented in this dissertation is a demonstration of how anatomic three-dimensional (3D) computational knee models can be an effective alternative for investigating knee mechanics when compared to the cost and time prohibitive nature of in-vivo and in-vitro methods. …