Mechanical Engineering Commons^™

Applicability Of Nanofluids In High Flux Solar Collectors, R. A. Taylor, P. E. Phelan, Todd Otanicar, C. A. Walker, M. Nguyen, S. Trimble, R. Prasher

Mechanical Engineering Faculty Works

Concentrated solar energy has become the input for an increasing number of experimental and commercial thermal systems over the past 10-15 years [M. Thirugnanasambandam et al., Renewable Sustainable Energy Rev. 14 (2010)]. Recent papers have indicated that the addition of nanoparticles to conventional working fluids (i.e., nanofluids) can improve heat transfer and solar collection [H. Tyagi et al., J. Sol. Energy Eng. 131, 4 (2009); P. E. Phelan et al., Annu. Rev. Heat Transfer 14 (2005)]. This work indicates that power tower solar collectors could benefit from the potential efficiency improvements that arise from using a nanofluid working fluid. A …

Advanced Underwater Vehicle Navigation, M. Jordan Stanway

Link Foundation Ocean Engineering and Instrumentation Fellowship Reports

Underwater vehicles–both manned and unmanned–are critical in our efforts to explore and study the depths of the ocean. Most underwater sensors possess a relatively small field of view; this means they must be carried over large distances to achieve high spatial coverage and resolution. The vast amount of data these sensors collect is much more valuable if the location of the vehicle is precisely known at the time the data is collected. This gives rise to the maxim: The data is only as good as the navigation. Navigation remains a challenging problem for underwater vehicles. Fundamental limitations of sensing technology …

Framework For Cohesive Zone Model Based Multiscale Damage Evolution In A Fatigue Environment, Michael Andrew Thomas

Browse all Theses and Dissertations

The focus of this research is to develop a framework to track damage evolution in a structural model subjected to a fatigue environment. This framework incorporates a micromechanical approach of continuous damage modeling, where damage in a homogenized representative microstructure is introduced at the continuum scale through the material constitutive matrix. In this research, damage in the representative microstructure is simulated utilizing cohesive zone models (CZM) whose properties are a function of the magnitude of applied stresses and the resulting separation. In order to minimize the mesh dependence of the cohesive zone model an adaptive meshing technique is employed. A …

A Study On The Effects Of Coil Wedge During Rewinding Of Thin Gauge Metals, Jantzen L. Hinton

Browse all Theses and Dissertations

With the increase in demand for high quality thin gauge metals improvements to control systems that monitor strip characteristics must first be acquired. During the rewinding of sheet metal, little insight is known as to what stresses are attributed to the actual winding process, not simply those induced by the mill. When winding effects become too severe they will alter control system readings, prompting the need for a rapid model that can predict winding effects and filter them from current control systems. This research develops a new method to determine a 4th order Airy function that predicts the 2D stress …

Computational Investigation Of Optimal Heavy Fuel Direct Injection Spark Ignition In Rotary Engine, Asela A. Benthara Wadumesthrige

Browse all Theses and Dissertations

The main objective of this computational study is to investigate the optimum injection and spark parameters for the direct injection spark ignition (DISI) Wankel rotary engine using diesel fuel. Currently only port fuel injected gasoline rotary engines are available in the automotive industry. Compared to reciprocating type engines rotary engine is mechanically simple, less vibrate, have higher power to weight ratio and achieve better performance at high rpm. Due to the inherent low fuel efficiency of rotary engine and increasing gas prices, application of the rotary engine in conventional automobiles is decreasing. This project seeks to introduce DISI technology to …

An Implicit High-Order Spectral Difference Method For The Compressible Navier-Stokes Equations Using Adaptive Polynomial Refinement, Caleb J. Barnes

Browse all Theses and Dissertations

A high/variable-order numerical simulation procedure for gas dynamics problems was developed to model steep grading physical phenomena. Higher order resolution was achieved using an orthogonal polynomial Gauss-Lobatto grid, adaptive polynomial refinement and artificial diffusion activated by a pressure switch. The method is designed to be computationally stable, accurate, and capable of resolving discontinuities and steep gradients without the use of one-sided reconstructions or reducing to low-order. Solutions to several benchmark gas-dynamics problems were produced including a shock-tube and a shock-entropy wave interaction. The scheme's 1st-order solution was validated in comparison to a 1st-order Roe scheme solution. Higher-order solutions were shown …

A Study Of The Aerodynamic Behavior Of A Nrel Phase Vi Wind Turbine Using The Cfd Methodology, Yen-Pin Chen

Browse all Theses and Dissertations

Wind energy is an abundant natural resource that people have been trying to tap in recent decades. More and more wind turbines are being built to solve the world's energy shortage problem. For a wind turbine, power extracted from the wind by the rotor and the torque applied to the wind turbine blades are important issues in the design process. Thus there is a need to predict the performance of wind turbine blades using computer modeling. This work shows the results of a computational fluid dynamic simulation developed to predict the air flow field and associated aerodynamic quantities around the …

Effect Of Material Anomalies On Fatigue Life Of Turbine Disks, Jace A. Carter

Browse all Theses and Dissertations

There is an economic need to extend the fatigue life of turbine engine rotor disks. The probability of failure during the operation life must be quantified as components remain in service beyond their traditional safe-life limit. Fracture mechanics based probabilistic methods are utilized to predict the probability of failure of components containing manufacturing and fatigue anomalies. Total fatigue life is defined in terms of crack initiation and propagation phases. A micromechanical initiation model uses material properties at the micro-scale to characterize the initiation phase, while short and long fatigue-crack growth models predict the crack propagation phase. A Monte Carlo simulation …

Niyama Based Taper Optimizations In Steel Alloy Castings, Daniel A. Gorsky

Browse all Theses and Dissertations

In the casting process, regions of shrinkage porosity can be reduced or eliminated through the implementation of taper, or small angled additions of mass on the boundaries of the part design, before risers are placed on the casting. Taper supplements the effect of risers so that a smaller riser volume is necessary to make a casting sound. Typically, taper is determined for a casting by using industry guidelines that were developed for simple two-dimensional simplifications of a complex casting. There is no accepted method of defining taper directly on part geometry aside from using expert opinions to make final decisions …

Computational Modeling And Analysis Of Heavy Fuel Feasibility In Direct Injection Spark Ignition Engine, Suniludaya Simha Moda

Browse all Theses and Dissertations

Direct Injection spark ignition (DISI) technology is helpful for the present day engine to increase the fuel efficiency. Power output and the choice of fuel as the demand and scarcity for fossil fuels are increasing. As a new technology DISI engines are employed in some commercial cars like the Pontiac Solstice using gasoline fuel. The advantages of DISI engines like use of different fuels, reduced compression ratio, reduced injection pressure and reduced operating pressures in DISI engines has not been widely tested. As a new technology DISI engines lack experimental results and combustion co-relations that can be directly used as …

Modeling And Optimization To Evaluate Sustainability Performance Of Customizable Product Service Systems, Ken Harsha Tilakaratne Wijekoon

University of Kentucky Master's Theses

The aim of this thesis is to present a new methodology to evaluate and optimize sustainability of customizable product-service systems while ensuring economic, environmental and societal constraints are also satisfied. Activities across the total product lifecycle are considered to develop a model that evaluates closed-loop flow, while being monitored through the growth, maturity and decline stages of the product to provide a comprehensive analysis. A novel method to evaluate the customer satisfaction is also presented. The research considers a modular product where customization can be achieved by selecting from alternatives while ensuring the compatibility between these alternatives. A manufacturer will …

Achieving High Efficiency Laminated Polymer Solar Cell With Interfacial Modified Metallic Electrode And Pressure Induced Crystallization, Yongbo Yuan, Yu Bi, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

We report efficient laminated organic photovoltaic device with efficiency approach the optimized device by regular method based on Poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). The high efficiency is mainly attributed to the formation of a concrete polymer/metal interface mechanically and electrically by the use of electronic-glue, and using the highly conductive and flexible silver film as anode to reduce photovoltage loss and modifying its work function for efficiency hole extraction by ultraviolet/ozone treatment, and the pressure induced crystallization of PCBM.

In Vitro Models For Glaucoma Research: Effects Of Hydrostatic Pressure, Yuan Lei, Shadi Rajabi, Ryan M. Pedrigi, Darryl R. Overby, A. Thomas Read, C. Ross Ethier

Department of Mechanical and Materials Engineering: Faculty Publications

PURPOSE. The response of cells (e.g., optic nerve head [ONH] cells) to mechanical stress is important in glaucoma. Studies have reported the biological effects of hydrostatic pressure on ONH cells cultured on a rigid substrate. An apparatus, designed to independently vary hydrostatic pressure and gas tension (including oxygen tension) in culture medium, was used to evaluate the effects of pressure and tension on cell migration, shape, and α-tubulin architecture in a transformed cell line (DITNC1 rat cortical astrocytes).

METHODS. During the assay period, cells were exposed to one of four experimental configurations: (1) control pressure and control gas tension; (2) …

Impact Of Elliptical Trainer Ergonomic Modifications On Perceptions Of Safety, Comfort, Workout, And Usability For People With Physical Disabilities And Chronic Conditions, Judith M. Burnfield, Yu Shu, Thad W. Buster, Adam P. Taylor, Carl A. Nelson

Department of Mechanical and Materials Engineering: Faculty Publications

Background The popularity of elliptical training has grown in rehabilitation, fitness, and home settings as a means for improving fitness and walking, yet many people with physical disabilities and chronic conditions experience difficulties when trying to use elliptical trainers.

Objective The purpose of this study was to compare, for people with disabilities and chronic conditions, perceptions of safety, comfort, workout, and usability of 4 elliptical trainers before and after the development of a set of low-cost adaptations.

Design This study was a quasi-experimental repeated-measures investigation.

Methods Twenty adults with diverse medical conditions and functional abilities evaluated 4 elliptical trainers for …

Assessment Of Shape Memory Alloy Stent Deployment In A Stenosed Artery, Shijia Zhao, Linxia Gu, Stacey R. Froemming

Department of Mechanical and Materials Engineering: Faculty Publications

Purpose — Shape memory alloy (SMA) stents have been used increasingly for the treatment of complex arterial occlusions. There is an immediate need to quantify the mechanical performance of SMA stents to open occluded arteries.
Methods — The stent crimping and expanding process was assessed through both numerical modeling and in-vitro studies. The implantation of a SMA stent in curved arteries with eccentric stenosis were simulated to evaluate the effect of artery curvature on arterial mechanics.
Results — The crimping process stored a considerable amount of strain energy in the stent, which were then released through self-expansion until a balance …

Comparative Analysis Of The Biaxial Mechanical Behavior Of Carotid Wall Tissue And Biological And Synthetic Materials Used For Carotid Patch Angioplasty, Alexey Kamenskiy, Iraklis I. Pipinos, Jason N. Mactaggart, Syed A. Jaffar Kazmi, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Patch angioplasty is the most common technique used for the performance of carotid endarterectomy. A large number of patching materials are available for use while new materials are being continuously developed. Surprisingly little is known about the mechanical properties of these materials and how these properties compare with those of the carotid artery wall. Mismatch of the mechanical properties can produce mechanical and hemodynamic effects that may compromise the long-term patency of the endarterectomized arterial segment. The aim of this paper was to systematically evaluate and compare the biaxial mechanical behavior of the most commonly used patching materials. We compared …

It’S Not What You Think: A Theory For Understanding The Lack Of Interest Among Domestic Students In The Engineering Phd, Michelle C. Howell Smith, Amanda L. Garrett, Ellen Weissinger, Namas Chandra

Department of Mechanical and Materials Engineering: Faculty Publications

We live in a fast-paced world surrounded by technological advances. Engineers with advanced skills perform important functions in our society. However we know very little about how engineers consider obtaining advanced education and skills. The purpose of this study is to understand and develop a theory explaining the process domestic engineers undergo in developing an interest in obtaining a PhD in engineering. Our research was guided by the following central research question: What is the theory that explains the process of developing interest in doctoral-level engineering education for engineers? We used qualitative, grounded theory methods, to investigate the process of …

Frequency Shifts In Plate Crystal Resonators Induced By Electric, Magnetic, Or Mechanical Fields In Surface Films, Nan Liu, J.S. Yang, Yuantai Hu, Xuedong Chen, Wei Jiang

Department of Mechanical and Materials Engineering: Faculty Publications

We study frequency shifts in plate crystal resonators with surface films. The films are multiphysical, including the effects of inertia, stiffness, intrinsic stress, piezoelectric coupling, and piezomagnetic coupling. Mindlin’s two-dimensional equations for a crystal plate with two elastic surface films are generalized to include the multiphysical effects of the films. They are used to study thickness-shear vibrations of a rotated Y-cut quartz plate with initial fields resulting from the mechanical, electric, and magnetic fields in the surface films. Frequency shifts caused by the initial fields are calculated and examined. Results show that plate crystal resonators with multiphysical surface films may …

A Few Transient Effects In At-Cut Quartz Thickness-Shear Resonators, Runyu Zhang, Hongping Hu

Department of Mechanical and Materials Engineering: Faculty Publications

We study a few transient effects of AT-cut quartz thickness-shear resonators, including resonator turning on and turning off as well as voltage amplitude and frequency fluctuations. Mindlin’s two-dimensional plate equations are used and solved analytically. Both a sudden change and a gradual change of the driving voltage are studied. It is found that for a resonator with a frequency of 1.649430868 MHz and material quality factor of Q = 10⁵, the characteristic time scale of the transient effects is of the order of 0.1 s.

Use Of Environmental Scanning Electron Microscopy For In Situ Observation Of Interaction Of Cells With Micro- And Nanoprobes, Alexander Goponenko, B. J. Boyle, K. I. Jahan, Maxim V. Gerashchenko, Dmitri E. Fomenko, Vadim N. Gladyshev, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Precision intracellular sensing, probing and manipulation offer unprecedented opportunities for advances in biological sciences. Next-generation ultra-fine probes will be capable of targeting individual cell organelles. Development of such probes as well as probes capable of penetrating through tough cell walls requires detailed knowledge of cell-probe interaction. This Letter evaluated the applicability of environmental scanning electron microscopy (ESEM) for cell and cell-probe interaction imaging. Several types of cells (plant and yeast cells as well as mouse spermatozoa) were successfully imaged in their natural state, with mouse spermatozoa observed by ESEM for the first time. Computerized stage applied to image was tough …