Mechanical Engineering Commons^™

Phase Transitions In Mechanically Milled Mn-Al-C Permanent Magnets, Michael J. Lucis, Timothy E. Prost, Xiujuan Jiang, Meiyu Wang, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Mn-Al powders were prepared by rapid solidification followed by high-energy mechanical milling. The rapid solidification resulted in single-phase ε. The milling was performed in both the ε phase and the τ phase, with the τ-phase formation accomplished through a heat treatment at 500 °C for 10 min. For the ε-milled samples, the conversion of the ε to the τ phase was accomplished after milling via the same heat treatment. Mechanical milling induced a significant increase in coercivity in both cases, reaching 4.5 kOe and 4.1 kOe, respectively, followed by a decrease upon further milling. The increase in coercivity was the …

Arising Applications Of Ferroelectric Materials In Photovoltaic Devices, Yongbo Yuan, Zhengguo Xiao, Bin Yang, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

The ferroelectric-photovoltaic (FE-PV) device, in which a homogeneous ferroelectric material is used as a light absorbing layer, has been investigated during the past several decades with numerous ferroelectric oxides. The FE-PV effect is distinctly different from the typical photovoltaic (PV) effect in semiconductor p–n junctions in that the polarization electric field is the driving force for the photocurrent in FE-PV devices. In addition, the anomalous photovoltaic effect, in which the voltage output along the polarization direction can be significantly larger than the bandgap of the ferroelectric materials, has been frequently observed in FE-PV devices. However, a big challenge faced by …

Computational And Experimental Study On Vertical Axis Wind Turbine In Search For An Efficient Design, Mohammad M. Bashar

College of Graduate Studies: Theses & Dissertations

Wind alone can fulfill most of the energy requirement of the world by its efficient conversion in to energy. Though Horizontal Axis Wind Turbine (HAWT) is more popular but needs high wind speed to generate energy. On the other hand Vertical Axis Wind Turbine (VAWT) needs low wind speed and can be installed anywhere which are some of the reasons for this research. The main objective of this research is to improve the design and performance of VAWT to make it more attractive, efficient, durable and sustainable. For a VAWT the blades perform the main role to extract energy from …

Optimal Design Of Geothermal Power Plants, Joshua Clarke

Theses and Dissertations

The optimal design of geothermal power plants across the entire spectrum of meaningful geothermal brine temperatures and climates is investigated, while accounting for vital real-world constraints that are typically ignored in the existing literature. The constrained design space of both double-flash and binary geothermal power plants is visualized, and it is seen that inclusion of real-world constraints is vital to determining the optimal feasible design of a geothermal power plant. The effect of varying condenser temperature on optimum plant performance and optimal design specifications is analyzed. It is shown that condenser temperature has a significant effect on optimal plant design …

Modeling Acute Changes In Bladder Wall Tension, Shape And Compliance During Filling, Firdaweke Habteyes

Theses and Dissertations

The bladder wall consists primarily of detrusor smooth muscle. Tension-sensitive nerves in the bladder wall are responsible for providing bladder fullness information that is interpreted as urgency. Bladder wall tension, and therefore nerve output, is a function of bladder volume, shape and material properties. Studies have shown that the bladder wall exhibits acutely regulated detrusor compliance. In addition, bladder shape throughout filling depends on intra-abdominal forces and material properties of the bladder wall, such as regulated detrusor compliance. This thesis focused on modeling the potential influence of acute changes in bladder compliance, shape and bladder wall tension during filling. Laplace’s …

Cfd Assessment Of Respiratory Drug Delivery Efficiency In Adults And Improvements Using Controlled Condensational Growth, Ross L. Walenga

Theses and Dissertations

Pharmaceutical aerosols provide a number of advantages for treating respiratory diseases that include targeting high doses directly to the lungs and reducing exposure of other organs to the medication, which improve effectiveness and minimize side effects. However, difficulties associated with aerosolized drug delivery to the lungs include drug losses in delivery devices and in the extrathoracic region of human upper airways. Intersubject variability of extrathoracic and thoracic drug deposition is a key issue as well and should be minimized. Improvements to respiratory drug delivery efficiency have been recently proposed by Dr. P. Worth Longest and Dr. Michael Hindle through the …

Analysis And Modeling Of The Roles Of Actin-Myosin Interactions In Bladder Smooth Muscle Biomechanics, Seyed Omid Komariza

Theses and Dissertations

Muscle mechanical behavior potentially plays an important role in some of the most common bladder disorders. These include overactive bladder, which can involve involuntary contractions during bladder filling, and impaired contractility or underactive bladder, which may involve weak or incomplete contractions during voiding. Actin-myosin cross-bridges in detrusor smooth muscle (DSM) are responsible for contracting and emptying the bladder. The total tension produced by muscle is the sum of its preload and active tensions. Studies suggest that actin-myosin cross-links are involved in adjustable preload stiffness (APS), which is characterized by a preload tension curve that can be shifted along the length …

Capillarity And Two-Phase Fluid Transport In Media With Fibers Of Dissimilar Properties, Thomas M. Bucher Jr.

Theses and Dissertations

Capillarity is a physical phenomenon that acts as a driving force in the displacement of one fluid by another within a porous medium. This mechanism operates on the micro and nanoscale, and is responsible for countless observable events. This can include applications such as absorption in various hygiene products, self-cleaning surfaces such as water beading up and rolling off a specially-coated windshield, anti-icing, and water management in fuel cells, among many others.

The most significant research into capillarity has occurred within the last century or so. Traditional formulations for fluid absorption include the Lucas–Washburn model for porous media, which is …

A Practical Tool For The Determination Of Surface Stresses In Railroad Bearings With Different Contact Geometries And Load Conditions Using Finite Element Analysis, Michael A. Mason

Theses and Dissertations

The connection between contact geometry and fatigue in tapered roller bearings utilized in the railroad environment is still of interest. Roller bearings for railroad applications are typically precision ground with crowned contact geometries to prevent edge loading of components. This normally results in completely elastic Hertzian contact stresses under standard railcar loads. However, under extreme load conditions, detrimental edge loading has been known to occur. It is proposed to develop a tool, using finite element analysis, that can be utilized to optimize complex raceway crown geometries for severe applications.

A successful implementation of this tool is presented and validated using …

Fabrication Of Out-Of-Autoclave Bismaleimide Based Composite Laminates With Embedded Fiber Optic Sensors, Sudharshan Anandan

Masters Theses

"Composites are becoming the material of choice in applications where weight savings are critical, like aerospace structures. The common composites used are- Carbon/Epoxy and Carbon/Bismaleimide (BMI). BMI based systems are preferred in applications which involve operating temperatures higher than conventional epoxies. Carbon/BMI laminates are traditionally fabricated in an autoclave, which is associated with high operating costs. In this work, a low cost out of autoclave (OOA) process is evaluated. It is desirable to have BMI OOA prepreg systems cure at reasonably low temperatures with sufficient degree of cure and green strength to maintain rigidity for subsequent freestanding post cure Carbon/BMI …

A Driving Simulator Study To Evaluate The Impact Of Portable Changeable Message Signs (Pcms) On Driver Speed Characteristics, Bharath Kolar Venkat

Masters Theses

"This research project examined the effects of sequential Portable Changeable Message Signs (PCMS) on driver behavior in work zones. PCMS are temporary traffic control (TTC) devices, part of Intelligent Transportation Systems, which supplement static signs to provide advance warning and real-time information to drivers. Text and number based messages are displayed on the PCMS for which detailed evaluation has not been carried out before. This research fills this gap using a driving simulator (DS) supplemented by objective and subjective surveys. A work zone on I-44 in rural Missouri was replicated in the DS using video recordings and GIS (Geographical Information …

Design And Development Of Scalable Solar Powered Water Purification Systems For Developing Nations, Shavin Pinto

Doctoral Dissertations and Master's Theses

This thesis presents the design and development of solar powered water purification systems. The systems were designed to meet specific customer requirements that were established from the experiences gained after the installation of five water purification systems in various Haitian communities. The systems are scalable and are able to supply 10,000-20,000 gallons of clean drinking water per day. The design consists of a three-stage filtration system with a disc-type sediment filter, a 0.1 micron ultrafiltration membrane, and an ultraviolet light for disinfection. The backwash cycle extends the life of the ultrafiltration membrane to 4-7 years before a new filter is …

Review Of Development Stages In The Conceptual Design Of An Electro Hydrostatic Actuator For Robotics, Velibor Karanović, Mitar Jocanović, Vukica Jovanović

Engineering Technology Faculty Publications

The design of modern robotic devices faces numerous requirements and limitations which are related to optimization and robustness. Consequently, these stringent requirements have caused improvements in many engineering areas and lead to development of new optimization methods which better handle new complex products designed for application in industrial robots. One of the newly developed methods used in industrial robotics is the concept of a self-contained power device, an Electro-Hydrostatic Actuator (EHA). EHA devices were designed with a central idea, to avoid the possible drawbacks which were present in other types of actuators that are currently used in robotic systems. This …

Design And Construction Of A Subcooled Boiling Flow Loop With An Internally Heated Vertical Annulus For Use In Testing Departure From Nucleate Boiling (Dnb), Joseph Kreynin

Dissertations and Theses

The design and testing of an apparatus to use in subcooled boiling flow experiments. A vertical annulus flow loop was design to mimic a rod used in a reactor boiler. The system was tested at different velocities and temperatures to verify it could be used in a range of experiments to try and match real world conditions. The system managed to produce the desired outcome of bubble growth in a desired location as well as run with the PIV system showing good prospect in the intended use of the experimental set up.

Comparison Of Manufacturing Techniques For Composites Subjected To High Speed Impact, Kenneth Gollins

Dissertations and Theses

No abstract provided.

Early Prediction Of Fracture In Bodies Bounded By Random Rough Surfaces, Hector Medina

Theses and Dissertations

Under certain loading conditions, surfaces topography coupled with materials degree of brittleness can significantly compromise the mechanical performance of structures. The foregoing remains valid even if roughness is intentionally introduced for engineering reasons. In either case, stress can concentrate. The case of the stress concentration in surfaces having randomly distributed pits is a problem that, although being very practical, yet it remains unsolved. The complexity of a random configuration renders difficult the problem of analytically finding relationships between surface parameters and markers indicative of mechanical failure. Another difficulty is the reproducibility of replicates of specimens possessing random rough surfaces, for …

Jump And Pull-In Dynamics Of An Electrically Actuated Bistable Mems Device, Laura Ruzziconi, Stefano Lenci, Mohammad I. Younis

Mechanical Engineering Faculty Scholarship

This study analyzes a theoretical bistable MEMS device, which exhibits a considerable versatility of behavior. After exploring the coexistence of attractors, we focus on each rest position, and investigate the final outcome, when the electrodynamic voltage is suddenly applied. Our aim is to describe the parameter range where each attractor may practically be observed under realistic conditions, when an electric load is suddenly applied. Since disturbances are inevitably encountered in experiments and practice, a dynamical integrity analysis is performed in order to take them into account. We build the integrity charts, which examine the practical vulnerability of each attractor. A …

The Influence Of Mesa Activities On Underrepresented Students Nsf Dr K-12 Proposal 1020019, C. Hailey, Chandra Austin Stallworth, Cameron Denson, Daniel L. Householder

Mechanical and Aerospace Engineering Faculty Publications

Mathematics, Engineering, Science Achievement (MESA) outreach programs are partnerships between K-12 schools and higher education in nine states. MESA efforts introduce integrated experiences in science, mathematics and engineering to K-12 students from groups that are traditionally underrepresented in the STEM disciplines. This exploratory study examined the influence of selected MESA activities on students' self-efficacy, their perceptions of engineering, and their interest in engineering and other STEM fields. Field trips, guest lecturers, design competitions, hands-on activities and student career and academic advisement were of specific interest in this survey. The project also investigated the relationship between student engagement in MESA and …

A Study Of Passenger Car Acoustic Cavity Boom Simulation Methods, Shreerang Dhabe

Dissertations, Master's Theses and Master's Reports - Open

The project objective is the study of acoustic boom phenomenon at 40 Hz in Chevrolet Cruze LTZ and recommend modeling techniques to improve accuracy of model prediction. Acoustic boom is caused by solid-fluid interaction between car structure and air inside the car cavity.

In this report, finite element analysis software Abaqus 6.12-3 is used to simulate the acoustic-structural coupling. The structural and acoustic mesh for the Chevrolet Cruze LTZ are fully coupled and solved using Abaqus ‘strongly coupled’ solution. In order to understand the physics of acoustic boom in a car simple car box models were designed. Simple box car …

Measuring Head Impact Contact Pressure In Collegiate Football Games To Correlate Head Kinematics To Brain Kinetics Elucidating Brain Injury Dynamics, Chandrika S. Abhang

Dissertations, Master's Theses and Master's Reports - Open

Does a brain store thoughts and memories the way a computer saves its files? How can a single hit or a fall erase all those memories? Brain Mapping and traumatic brain injuries (TBIs) have become widely researched fields today. Many researchers have been studying TBIs caused to adult American football players however youth athletes have been rarely considered for these studies, contradicting to the fact that American football enrolls highest number of collegiate and high-school children than adults. This research is an attempt to contribute to the field of youth TBIs.

Earlier studies have related head kinematics (linear and angular …

Military Vehicle Optimization And Control, Denise M. Rizzo

Dissertations, Master's Theses and Master's Reports - Open

It is remarkable that there are no deployed military hybrid vehicles since battlefield fuel is approximately 100 times the cost of civilian fuel. In the commercial marketplace, where fuel prices are much lower, electric hybrid vehicles have become increasingly common due to their increased fuel efficiency and the associated operating cost benefit. An absence of military hybrid vehicles is not due to a lack of investment in research and development, but rather because applying hybrid vehicle architectures to a military application has unique challenges. These challenges include inconsistent duty cycles for propulsion requirements and the absence of methods to look …

Model Updating And Structural Health Monitoring Of Horizontal Axis Wind Turbines Via Advanced Spinning Finite Elements And Stochastic Subspace Identification Methods, Antonio Velazquez Hernandez

Dissertations, Master's Theses and Master's Reports - Open

Wind energy has been one of the most growing sectors of the nation’s renewable energy portfolio for the past decade, and the same tendency is being projected for the upcoming years given the aggressive governmental policies for the reduction of fossil fuel dependency. Great technological expectation and outstanding commercial penetration has shown the so called Horizontal Axis Wind Turbines (HAWT) technologies. Given its great acceptance, size evolution of wind turbines over time has increased exponentially. However, safety and economical concerns have emerged as a result of the newly design tendencies for massive scale wind turbine structures presenting high slenderness ratios …

Numerical Analysis Of Thermal Stress And Deformation In Multi-Layer Laser Metal Deposition Process, Heng Liu

Masters Theses

"Direct metal deposition (DMD) has gained increasing attention in the area of rapid manufacturing and repair. It has demonstrated the ability to produce fully dense metal parts with complex internal structures that could not be achieved by traditional manufacturing methods. However, this process involves extremely high thermal gradients and heating and cooling rates, resulting in residual stresses and distortion, which may greatly affect the product integrity. The purpose of this thesis is to study the features of thermal stress and deformation involved in the DMD process. Utilizing commercial finite element analysis (FEA) software ABAQUS, a 3-D, sequentially coupled, thermo-mechanical model …

Effect Of Stress Concentrations On Fatigue Of Composite And Metallic Structures, Ross Henry Falen

Masters Theses

"The complex shapes of hydrokinetic turbine blades can include part features such as a fillet, step, or hole. Situations can arise where two part features, such as a hole and a fillet, may be in close proximity which can introduce stress concentrations within the blade structure, adversely affecting the structure's life. Because the interaction between the part features isn't well known, fatigue data is needed to determine the proper analysis.

In this thesis, two separate topics are discussed and investigated. The first topic deals with stress concentrations in hydrokinetic turbine blades. Several blade designs were tested and improved upon to …

An Effectiveness - Based Analysis Of Ground Coupled Heat Exchangers, Chou Shen

Masters Theses

"This thesis develops a theoretical framework, termed [Effectiveness] - BLU, to characterize the relation between temperatures, thermal contact and borehole length as it relates to the heat transfer processes in ground coupled heat exchangers used for ground source heat pump systems.

Borehole outflow temperature depends on the inflow temperature, the heat imposed on the borehole and the temperature history of the ground. In addition, variation of outflow temperature influences inflow temperature, even for the case of constant heat pump load. Because of this kind of feedback, the borehole inflow temperature may not be constant even with a fixed building load. …

Additive Manufacturing Laser Deposition Of Ti-6al-4v For Aerospace Repair Application, Nanda Kumar Dey

Masters Theses

"Parts or products machined from high performance metals are very expensive, partly due to the processing complexities during manufacturing. Therefore, many high performance metal parts users, such as the aerospace industry, mold/die casting industry, heavy machinery consumers etc., extend the service of these damaged parts by employing repair or remanufacturing technology. The research objective is to use laser deposition and machining processes to repair titanium parts.

This thesis discusses a new way of approach for developing a repair process for Ti-6Al-4V for the aerospace industry using Laser Metal Deposition (LMD). The repairs were conducted in a multi-axis hybrid manufacturing systems …

Design And Development Of A High Velocity Oxy-Fuel Thermal Spray Gun, Luisa Alejandra Cabrera Maynez

Open Access Theses & Dissertations

The High Velocity Oxy-Fuel (HVOF) system is a highly promising technique for the production of thermal barrier coatings (TBCs), helpful in the protection of materials exposed to extreme thermal and corrosive environments. Coatings generated through the technique are employed in industrial settings to extend product life, increase performance and decrease maintenance costs. HVOF yields lower porosity and higher adhesion TBCs when compared to similar thermal spraying processes. Though gas fuelled systems are the norm in this technique, there is a recent interest in employing liquids due to their low cost and increased deposit density. Economic and highly scalable, HVOF process …

Fused Deposition Modeling (Fdm) Fabricated Part Behavior Under Tensile Stress, Thermal Cycling, And Fluid Pressure, Mohammad Shojib Hossain

Open Access Theses & Dissertations

Material extrusion based additive manufacturing (AM) technology, such as fused deposition modeling (FDM), is gaining popularity with the numerous 3D printers available worldwide. FDM technology is advancing from exclusively prototype construction to achieving production-grade quality. Today, FDM-fabricated parts are widely used in the aerospace industries, biomedical applications, and other industries that may require custom fabricated, low volume parts. These applications are and were possible because of the different production grade material options (e.g., acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyphenylsulfone (PPSF), etc.) available to use in FDM systems. Recent researchers are exploring other material options including polycaprolactone (PCL), polymethylmethacrylate (PMMA), …

Experimental Evaluation Of Flame Stability And Pollutant Emissions From A Multi-Tube Fuel Injector, Sarzina Hossain

Open Access Theses & Dissertations

According to US Energy Information Administration coal is predicted to be the dominant source of power production in the United States until 2035. With fifty percent of the electricity generated in the United States originating from coal, the US produces close to 2 billion tons of CO2 per year from coal-burning power plants. The Integrated Gasification Combined Cycle (IGCC) offers a cleaner way to generate electricity-using coal. IGCC is a process where the feedstock is gasified and converted into to syngas (CO-H2) which can then be used as a fuel source to power energy-generating gas turbines. Compared to other hydrocarbons, …

Effect Of Multi-Tube Injector Geometry On Flame Stability And Nox Emission In A High Pressure Gas Turbine Combustor, Sudipa Sarker

Open Access Theses & Dissertations

Future generation gas turbine combustors for power production are expected to have the capability of operating on high hydrogen content fuels. To ensure the implementation of high hydrogen content (HHC) fuel in a power generation unit without negotiating with operational or emission advantages, the study of the flame stability regime and behavior of (HHC) fuel under gas turbine condition leads to the necessity of the development of an optically accessible high-pressure combustor. This Dissertation first presents the design of an optically high-pressure combustor facility based on 500 kW power and 1.5 MPa pressure which is the representative pressure of a …