Mechanical Engineering Commons^™

X-Ray Photoelectron Spectroscopic Studies Of Dolomite Surfaces Exposed To Undersaturated And Supersaturated Aqueous Solutions, Xiaoming Hu, Pratik Joshi, Sharmila M. Mukhopadhyay, Steven R. Higgins

Mechanical and Materials Engineering Faculty Publications

Cleaved surfaces of dolomite were studied using ex-situ X-ray photoelectron spectroscopy (XPS) following exposure of the surfaces to various experimental conditions. Dolomite samples exposed to air, to a highly undersaturated solution (0.1 M NaCl, pH = 9), and to solution with a supersaturation (-Delta mu/kT) of 5.5 (pH = 9) were investigated with semiquantitative methods of analysis to ascertain the degree of non-stoichiometry resulting at the dolomite surface from reactive conditions. It was found that the dolomite cleavage surface in undersaturated solution was not altered significantly from the stoichiometric surface termination. The composition of the cleaved surface after exposure to …

Landfill Gas As A Fuel For Ic Engine Operations, Guruprasath Narayanan

Masters Theses

An alternative fuel research facility was developed to study different alternative gaseous fuels like Landfill gases and Biogases and their mixtures with hydrogen as a fuel in a single cylinder spark ignition engine. Landfill gas was used as a fuel and the optimum process parameters such as compression ratio, spark timing and equivalence ratio were identified and reported.

Hydrogen enhanced combustion of landfill gas was studied and it was found that the addition of small amounts of hydrogen in the land fill gas has improved the combustion characteristics of the fuel and the performance of the spark ignition engine in …

Effect Of Dislocation On The Growth Of Quantum Dot In The Layered Semiconductor, Samir R. Kanade

Theses and Dissertations

Self assembled quantum dots (SAQDs) have drawn great interest recently due to their novel optoelectronic properties. We present an in-depth analytical study of the nucleation and growth of SAQDs on a heteroepitaxial layer. We discuss the fundamental uses of SAQDs on the epitaxial layers. Shape and size distribution of SAQDs greatly affect the functionality of the semiconductor nanostructure. Organized nucleation and growth are most of the times, if not all, desired. Fabrication of organized SAQDs may be fulfilled by using different types of stressors7 which concentrate energy and help in the nucleation of a surface QD. Numerical simulations with a …

A Stochastic Production Cost Model For Remanufacturing Systems, Gaurang S. Patel

Theses and Dissertations - UTB/UTPA

Growing environmental concern throughout this decade coupled with enforced legislation, customer expectations and economic incentives have forced increasing number of manufacturers to take back their products from end user. Managing this reverse flow of products is called reverse logistics. The stochastic nature of returned products complicates the production planning for remanufacturing systems in reverse logistics. In this thesis a stochastic production cost model, considering various costs associated under different situations for remanufacturing systems of returned products is developed. A search algorithm method is recommended to determine optimal production run size, production rate and space for remanufacturing systems in reverse logistics. …

Unsteady Numerical Analysis Of A 2-Dimensional, Hydrogen Fueled, Air-Breathing Dual Mode Scramjet Engine, Nathan John Luetke

Mechanical & Aerospace Engineering Theses & Dissertations

Upstream interaction in a transient two-dimensional dual-mode scramjet engine is examined. This research is performed to compare completed and verified steady results with unsteady results in order to have a better understanding of the flow field. The flow is solved numerically with a Mach 2.5 free stream and sonic normal injection of hydrogen fuel emanating from facing walls while no symmetry assumptions were made. The free stream is modeled as vitiated air in order to produce comparable flight enthalpies and stagnation properties at the combustor inlet during flight conditions of approximately Mach 7. The vitiated stream consists of water vapor …

Statistical Interpretation Of Mohr-Coulomb Theory As Applied To Fracture In Brittle Materials Containing Cracks, Mudit J. Monsi

Mechanical & Aerospace Engineering Theses & Dissertations

Fracture in brittle materials containing pre-existing cracks was studied. The probability of of crack growth under both shear and tensile stresses was determined for an arbitrary distribution of crack sizes. Two different crack orientation distributions, random and uniform, as well as friction were also taken into account. The material's reliability was assumed to depend on the number of active cracks at a particular stress level, and this was expressed as an arbitrary 2-parameter Weibull distribution. Two new and efficient methods for calculating crack growth probabilities based on spherical triangles and spherical caps were developed. They utilized normalized stress coordinates and …

Most Probable Point-Based Design Optimization, Akhil R. Tipnis

Mechanical & Aerospace Engineering Theses & Dissertations

Modem products ranging from simple components to complex systems should be designed to be optimal and reliable. The challenge of modem engineering is to ensure that manufacturing costs are reduced and design cycle times are minimized while achieving requirements for performance and reliability. If the market for the product is competitive, improved quality and reliability can generate very strong competitive advantages. Reliability based design optimization plays a very important role in designing almost any kind of product. This investigation focuses on the development of the hybrid PMNRIA approach which uses the active-in-reliability concept for reliability based design optimization. The efficiency …

Micron-Level Actuator For Thermal-Fluid Control In Microchannels, Nurhak Erbas

Mechanical & Aerospace Engineering Theses & Dissertations

Effectiveness of an actuator is investigated for thermal-flow control in microchannels. First, simulations of a single actuator in a quiescent external medium are performed in order to study the parameters characterizing the synthetic jet flow from the actuator. For this purpose, a simplified, two-dimensional configuration is considered. The membrane motion is modeled in a realistic manner as a moving boundary in order to accurately compute the flow inside the actuator cavity. The geometric and actuation parameters of the actuator are investigated to define the effectiveness of the jet flow. The study is done initially at macro scales. Then, the flow …

Life Cycle Impact Assessment Method For Early Design Phase Of Industrial Products, Harpreet Singh Multani

Mechanical & Aerospace Engineering Theses & Dissertations

The objective of this thesis is to develop a simplified life cycle impact assessment method that can reliably and quickly provide the values of Eco-indicator 99 single score, the Eco-indicator damage categories score (human health, ecosystem quality, resource depletion), environmental impacts like global warming, ozone depletion, acidification, eutrophication, photochemical oxidants potential of the product/process, which could be used in the initial design stages for alternative design comparisons and product improvements, thus leading towards green manufacturing.

To achieve this, a variety of products have been chosen and the life cycle inventory data is gathered from the environmental product declarations that are …

Socio-Economic Impacts Of Computer Viruses In Tanzania, M Victor

Tanzania Journal of Engineering and Technology (TJET)

This paper reports on a research project conducted with an objective of identifying and assessing various approaches used by different computer users (Management, System Administrators and end users) in Tanzania to combat computer viruses (CVs), and to assess users' awareness level on CVs. Specifically, the study aimed at assessing the awareness level on CVs to the Tanzanian business community; analyze the socio -economic impact caused by CVs in Tanzania and; assess existing methods, capacity and limitations on controlling CVs in Tanzania. Data was collected using both questionnaires and interview from financial institutions such as NBC and BOT, and telecommunications sector …

Seal Assembly For Machinery Housing, Lyndon Scott Stephens, Kevin W. Kelly

Mechanical Engineering Faculty Patents

A seal assembly for a machinery housing includes a seal ring having a micro heat exchanger and a gland plate for securing the seal ring to the machinery housing. The gland plate includes a cooling fluid port in communication with the micro heat exchanger.

Comparison Matrix Of Florida Residential Building Energy Code And The International Energy Conservation Code (Iecc) 2006, Florida Solar Energy Center, Mangesh Basarkar

FSEC Energy Research Center®

This report presents a comparison of the differences between the Florida and the IECC (2006) residential energy code requirements. In addition to this summary, the documentation is divided into three sets of distinct comparisons: Comparison of Performance-based methods, Comparison of Prescriptive methods and Comparison of key provisions of the texts. In order to provide the best housing stock, with a code that is easy to implement and enforce, the final recommendation of the study was for Florida to maintain its own code, but consider incorporating some of the newer IECC measures.

An Initial Non-Equilibrium Porous-Media Model For Cfd Simulation Of Stirling Regenerators, Roy Tew, Terry Simon, David Gedeon, Mounir B. Ibrahim, Wei Rong

Mechanical Engineering Faculty Publications

The objective of this paper is to define empirical parameters (or closwre models) for an initial thermai non-equilibrium porous-media model for use in Computational Fluid Dynamics (CFD) codes for simulation of Stirling regenerators. The two CFD codes currently being used at Glenn Research Center (GRC) for Stirling engine modeling are Fluent and CFD-ACE. The porous-media models available in each of these codes are equilibrium models, which assmne that the solid matrix and the fluid are in thermal equilibrium at each spatial location within the porous medium. This is believed to be a poor assumption for the oscillating-flow environment within Stirling …

A Comparative Study Of Various Loss Functions In The Economic Tolerance Design, Jehnan Pan, Jianbiao Pan

Industrial and Manufacturing Engineering

Engineering tolerance design plays an important role in modern manufacturing. In this paper, the Kapur's model was modified so that the economic specification limits for both symmetric and asymmetric losses can be established. Three different loss functions: (1) Taguchi's quadratic loss function; (2) Inverted Normal Loss Function; (3) Revised Inverted Normal Loss Function are compared in the economic tolerance design. The relationships between the three loss functions and process capability indices for symmetric tolerance are established. The results suggest that the revised inverted normal loss function be used in determination of economic specification limits.

Student Competitions - The Benefits And Challenges, Peter Schuster, Andrew Davol, Joseph Mello

Mechanical Engineering

Intercollegiate design competitions are a popular means to engage students in design activities that extend beyond the curriculum. When students gather around a project in their spare time and use their classroom skills to design, build, and test a product for an intercollegiate competition, something amazing happens: They develop a passion for engineering. This paper discusses the key benefits to engineering undergraduate students that flow from involvement in a team design competition. Advisor involvement plays a key role in both project success and student learning throughout the process. Different approaches to advising student competition teams are compared. Specific examples are …

Research In The Undergraduate Environment, Charles Birdsong, Peter Schuster

Mechanical Engineering

The benefits of research experiences for undergraduates are significant. For many faculty, these were the experiences that convinced us to pursue further education and a career in academia. However, performing research at an undergraduate institution carries with it certain challenges. In traditional research institutions, doctoral students perform most of the research activities, led by the faculty. These students have completed at least their undergraduate courses and can be expected to remain on the research team for four to six years. In contrast, at an undergraduate institution students may start in the group with only one or two engineering courses completed, …

Dynamic Characteristics Of Wide Exponential Film-Shape Slider Bearings Lubricated With A Nonnewtonian Couple Stress Fluid, Jaw-Ren Lin, Rong-Fang Lu, Chi-Ren Hung

Journal of Marine Science and Technology–Taiwan

On the basis of the Stokes micro-continuum theory, the nonNewtonian effects of couple stress fluids upon the dynamic characteristics of wide exponential-shaped slider bearings are presented in this paper. To take into account the couple stress effects arising from a Newtonian lubricant blended with various additives, the nonNewtonian couple-stress dynamic Reynolds-type equation is applied to calculate the bearing dynamics. According to the results obtained, the effects of couple stresses signify a decrease in the friction parameter and the volume flow rate, as well as an increase in the loadcarrying capacity, the dynamic stiffness coefficient and the dynamic damping coefficient for …

An Experimental Investigation Of Humidity And Temperature Effects On The Mechanical Properties Of Persfluorosulfonic Acid Membrane, Y. L. Tang, Anette M. Karlsson, Michael H. Santare, Michael Gilbert, Simon Cleghorn, William B. Johnson

Mechanical Engineering Faculty Publications

The mechanical properties of a perfluorosulfonic acid (PFSA) membrane have been investigated at different humidities and temperatures in a custom-designed environmental chamber. Tensile tests were conducted to determine Young’s modulus, the proportional limit stress (“yield strength”), break stress, and break strain. In-plane dimensional changes of the membrane at different temperature and humidities were also determined. The results indicate that Young’s modulus and the proportional limit stress of the PFSA membrane decrease as humidity and temperature increase. Higher temperature leads to lower break stress and higher break strain. However, humidity has little effect on the break stress and break strain. A …

Reinforcing Effects And Mechanical Properties Of Rc Beam With Cfs Under Static And Running Loads, Ming-Chien Hsu, Tadashi Abe, Tetsukazu Kida, Toshiaki Sawano, Kazuhiko Minakuchi

Journal of Marine Science and Technology–Taiwan

Through a series of experiments on RC beams reinforced with the carbon fiber sheet (CFS) under the static and running loads, the authors verified the effects of the aspect ratio (ratio of beam width to depth) and CFS reinforcement on the failure mechanism. The experiments revealed that: (1) CFS can effectively reinforce beams subjected to static loads in the flexural region, and increase the strength of beams subjected to running loads but such beams failed in shear, and (2) the tensile strength of CFS is greatly influenced by the aspect ratio. The authors evaluated how the aspect ratio influences the …

Development Of A Variational Part Model Using In-Process Dimensional Measurement Error, Shane A. Carlson

Theses and Dissertations

To improve the geometric accuracy of CNC machined parts, dynamic machining errors due to on-line disturbances (tool deflection, tool wear, heat deformation, etc.) should be accounted for in some manner. Unless these on-line disturbances are properly handled, it is obvious that a high degree of geometric accuracy is difficult to achieve. Many attempts have been made to compensate for these on-line disturbances such as the development of engineering models; however, the models are not adequate enough for reflecting the real phenomenon and are dependent on continuous process monitoring using a variety of sensors. Closed-loop process control is a scheme for …

A Lifting-Line Approach To Estimating Propeller/Wing Interactions, Doug F. Hunsaker, Deryl O. Snyder

Mechanical and Aerospace Engineering Faculty Publications

A combined wing and propeller model is presented as a low-cost approach to first-cut modeling of slipstream effects on a finite wing. The wing aerodynamic model employs a numerical lifting-line method utilizing the 3D vortex lifting law along with known 2D airfoil data to predict the lift distribution across a wing for a prescribed upstream flowfield. The propeller/slipstream model uses a blade element theory combined with momentum conservation equations. This model is expected to be of significant importance in the design of tail-sitter vertical take-off and landing (VTOL) aircraft, where the propeller slipstream is the primary source of air flow …

Compliant Mechanism Suspensions, Timothy Melvin Allred

Theses and Dissertations

This thesis has explored the use of compliant mechanisms in vehicle suspension systems, specifically where a compliant mechanism acts as part of the wheel locating mechanism and as the energy storage element. A compliant mechanism has the potential of reducing part count, joints, and manufacturing and assembly costs of a suspension system. Fatigue failure has been found to be a limiting design constraint which competes with space and weight constraints. Controlling wheel motion in response to control forces has also been shown to be an important functional requirement for a compliant suspension system. Vehicle applications that are best suited for …

Exchange Faculty Perspectives On International Collaborations, Donal Mchale

Conference Papers

The main purpose of the paper is to document key issues in developing successful transatlantic faculty exchanges and to document perspectives and key learnings’ emanating from the development and implementation of an international exchange process.

Plotting A Bright Future For Manufacturing Education: Results Of A Brainstorming Session, Daniel Waldorf, Sema E. Alptekin, Robert Bjurman

Industrial and Manufacturing Engineering

Manufacturing industries worldwide have undergone dramatic changes in recent years and now demand more from graduating manufacturing engineers. The effects of globalization have forever changed the parameters for success in manufacturing. Our educational institutions must respond to these changes with innovation. That agenda formed the basis for a special SME/CIRP international conference on manufacturing engineering education called “Looking Forward: Innovations in Manufacturing Engineering Education,” held in San Luis Obispo, California, June 22-25, 2005. At the meeting, manufacturing education professionals from around the world came together to share their own innovative ideas and to brainstorm ways to shape the future of …

Determination Of Uniaxial Residual Stress And Mechanical Properties By Instrumented Indentation, Manhong Zhao, Xi Chen, Jin Yan, Anette M. Karlsson

Mechanical Engineering Faculty Publications

We propose an improved technique to determine the uniaxial residual stress, elastic modulus, and yield stress of a linear elastic, perfectly plastic bulk material from the force–displacement curve of one conical indentation test. Explicit relationships between the indentation loading–unloading parameters, material properties, and residual stress are established through extensive finite element analyses. Good agreement is found between the input material parameters used in numerical indentation tests and the properties identified from the reverse analysis, with an error of less than 10% in most cases. The technique is applied to a nanoindentation experiment on the crosssection of a thermal barrier system, …

A Bimodular Theory For Finite Deformations: Comparison Of Orthotropic Second-Order And Exponential Stress Constitutive Equations For Articular Cartilage, Stephen M. Klisch

Mechanical Engineering

Cartilaginous tissues, such as articular cartilage and the annulus fibrosus, exhibit orthotropic behavior with highly asymmetric tensile–compressive responses. Due to this complex behavior, it is difficult to develop accurate stress constitutive equations that are valid for finite deformations. Therefore, we have developed a bimodular theory for finite deformations of elastic materials that allows the mechanical properties of the tissue to differ in tension and compression. In this paper, we derive an orthotropic stress constitutive equation that is second-order in terms of the Biot strain tensor as an alternative to traditional exponential type equations. Several reduced forms of the bimodular second-order …

Vision-Based Target Localization From A Fixed-Wing Miniature Air Vehicle, Joshua D. Redding, Timothy W. Mclain, Randal W. Beard, Clark N. Taylor

Faculty Publications

This paper presents a method for localizing a ground-based object when imaged from a small fixed-wing unmanned aerial vehicle (UAV). Using the pixel location of the target in an image, with measurements of UAV position and attitude, and camera pose angles, the target is localized in world coordinates. This paper presents a study of possible error sources and localization sensitivities to each source. The localization method has been implemented and experimental results are presented demonstrating the localization of a target to within 11 m of its known location.

Vector Field Path Following For Small Unmanned Aerial Vehicles, Derek R. Nelson, D. Blake Barber, Timothy W. Mclain, Randal W. Beard

Faculty Publications

This paper presents a new method for unmanned aerial vehicle path following using vector fields to represent desired ground track headings to direct the vehicle onto the desired path. The key feature of this approach is that ground track heading error and lateral following error approach zero asymptotically even in the presence of constant wind disturbances. Methods for following straight-line and circularorbit paths, as well as combinations of straight lines and arcs, are presented. Experimental results validate the effectiveness of this path following approach for small air vehicles flying in high-wind conditions.

Effect Of Polymorphic Phase Transformations Within An Alumina Layer On The Ignition Of Aluminum Particles, Mikhaylo Aleksiyovych Trunov

Dissertations

Experimental measurements of aluminum ignition temperature and models used to describe aluminum ignition are reviewed. It is shown that the current models cannot describe ignition of aluminum powders of different sizes and ignited under various experimental conditions. The properties of and phase changes occurring in the alumina scale existing on the surface of aluminum particles at different temperatures are systematically studied. The mechanism of aluminum oxidation is quantified and a new simplified ignition model is developed.

Thermogravimetry was used to study the oxidation of aluminum powders of various particle sizes and surface morphologies in oxygen at temperatures up to 1500°C. …

Synthesis And Characterization Of Mechanically Alloyed Aluminum-Based Compounds As High Energy Density Materials, Xiaoying Zhu

Dissertations

A new type of metastable reactive powders for potential use as high energy density materials in propellants, explosives, and pyrotechnics was developed. These powders are intended to replace aluminum typically added to energetic formulations to increase reaction enthalpy and temperature. The new materials are metastable aluminum-based alloys, which enable achievement of substantially reduced ignition temperatures and accelerated bulk burn rates compared to aluminum. Titanium and lithium were used as alloying components. The materials properties and characteristics leading to their enhanced combustion performance were investigated. The powders were prepared using mechanical alloying and characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy …