Engineering Commons^™

Toward An Understanding Of Fundamental Mechanisms In Transitional And Turbulence Flow Control, Ethan A. Davis

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Turbulence is an emergent phenomenon found throughout nature and engineering, alike. It plays a vital role in the aquatic locomotion of organisms, scalar mixing, fluid transport, shipping and transportation, and even the flow of biological fluids in the human body. Therefore, it is of utmost importance in both a practical and engineering sense to better understand turbulence with the goal of better controlling it. This dissertation focuses broadly on better understanding the underlying mechanisms behind wall-bounded turbulent flows, with an emphasis on exploiting those mechanisms for turbulence flow control.

We developed a numerical simulation to study the effect of slip …

Development Of A Mash Tl-3 Compliant Parapet Mounted Fence, Luis Rodriguez Alvizo

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

When roadways pass over railway tracks, there is a risk that debris from the roadway or pedestrians may fall onto the tracks and interfere with railway operations. Because of this, state Departments of Transportation (DOTs) commonly install debris fences in conjunction with bridge rails over railway tracks. However, the safety performance of debris fence systems when impacted by an errant vehicle has not been demonstrated through full-scale crash testing. Thus, the objective of this research was to develop a new, parapet-mounted debris fence for the Iowa DOT according to safety performance guidelines included in the American Association of State Highway …

Reduced-Order Modeling Of Loosening In Bolted Joints And Dynamic Interactions Between Axially Aligned Threaded Joints, Sandro Aldana

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Maintaining effective preload in bolted joints is critical for ensuring long-term performance and safety throughout the operation of any assembled structure. The loosening of bolted joints has been studied since the Industrial Revolution, but modeling approaches have only emerged over the past three decades. Although existing approaches are capable of simulating or predicting loosening in a single joint consisting of a single bolt, they are too computationally expensive to be used to model loosening in large structures consisting of many bolts. The objective of this thesis is to construct and employ a reduced-order modeling (ROM) approach that treats the internal …

Thermal & Mechanical Analysis Of Bombyx Mori Silk Nanofibers, Justin Busnot

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This thesis presents a study on the thermomechanical properties of Bombyx Mori silk nanofibers. These nanofibers were obtained from silkworm cocoons which were degummed to separate the fibroin and the sericin, the two proteins that make up silk. The fibroin was then centrifuged to remove insoluble particles and stored and 4°C before the electrospinning process. A parametric study of the electrospinning process was carried out in order to identify the factors allowing to obtain optimal mechanical properties. The current as well as the flow rate applied, the diameter of the syringe, the distance separating the syringe from collector or even …

Novel And Fast Peridynamic Models For Material Degradation And Failure, Siavash Jafarzadeh

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Fracture is one of the main mechanisms of structural failure. Corroded surfaces with chemically-induced damage are, notably, potential sites for crack initiation and propagation in metals, which can lead to catastrophic failure of structures. Despite some progress in simulating fracture and damage using classical models, realistic prediction of complex damage progression and failure has been out of reach for many decades. Peridynamics (PD), a nonlocal theory introduced in 2000, opened up new avenues in modeling material degradation and failure. Existing numerical methods used to discretize PD equations, however, are quite expensive as the PD nonlocal interactions make them unaffordable for …

Mash 2016 Test Level 3 And Test Level 4 Evaluation Of Roadside Safety Barrier With Pedestrian Features, Miguel Angel Hinojosa Palacios

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The Minnesota Department of Transportation (MnDOT) desires to use a vehicle, bicycle, and pedestrian combination bridge railing system along pedestrian and bicycle bridge paths. The system was evaluated per MASH 2016.

In full-scale crash test no. MNPD-3, the system was evaluated according to MASH test designation no. 3-11. The 2014 Dodge Ram 1500 crew cab pickup truck impacted the system 71¼ in. upstream from the centerline of post no. 4 with a speed of 63.4 mph at an angle of 25.3 degrees. The combination railing system was found to meet the AASHTO MASH 2016 TL-3 impact safety criteria.

MnDOT uses …

Exploration Of The Sludge Biodiesel Pathway, Zachary Christman

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Wastewater sludge is an overlooked source of fat, oil, and grease (FOG) that could be converted into biodiesel. The United States produces about 8 million tons of sludge per year. The disposal cost for this amount of sludge is about 2 billion dollars. The widespread availability and low cost of sludge compared to other biodiesel raw materials make it an economical choice for a renewable fuel. Using sludge as a raw material can produce 25 to 30 mg per gram of fatty acid methyl ester (FAME); the main component of biodiesel. Sludge biodiesel has the potential of transforming a portion …

Device Development For Long-Term Systemic Oral Biologic Drug Delivery, Benjamin Wankum

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

A biologic drug is a drug that is produced by a living organism. Biologic drugs are used to treat various medical conditions such as arthritis, diabetes, or certain forms of cancers due to their high potency and high selectivity of action. Drawbacks of biologics include their poor stability in the gastrointestinal tract and their poor absorption. In effect, this gives the drugs very low bioavailability and short therapeutic half-lives. To combat these obstacles, current delivery methods include subcutaneous injections at home or intravenous or intramuscular injections in a medical facility.

The overall scientific goal of the research was to utilize …

Voltage-Controlled Magnetic Anisotropy In Antiferromagnetic Mgo-Capped Mnpt Films, P. H. Chang, Wuzhang Fang, T. Ozaki, Kirill Belashchenko

Kirill Belashchenko Publications

The magnetic anisotropy in MgO-capped MnPt films and its voltage control are studied using first-principles calculations. Sharp variation of the magnetic anisotropy with film thickness, especially in the Pt-terminated film, suggests that it may be widely tuned by adjusting the film thickness. In thick films the linear voltage control coefficient is as large as 1.5 and -0.6 pJ/Vm for Pt-terminated and Mn-terminated interfaces, respectively. The combination of a widely tunable magnetic anisotropy energy and a large voltage-control coefficient suggest that MgO-capped MnPt films can serve as a versatile platform for magnetic memory and antiferromagnonic applications.

Development Of An Intraperitoneal Catheter Placement Device For Use On The Battlefield, Riley Reynolds

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The objective of this project was to simplify peritoneal cavity access so an Airforce field medic can safely infuse oxygen microbubbles (OMBs) into the intraperitoneal space for the emergency treatment of hypoxia due to lung damage. To solve this problem, we created an intraperitoneal catheter placement device for use on the battlefield. The three common methods and some of the most common devices for peritoneal cavity access were reviewed. Injury frequencies for each of the three methods were analyzed. The results showed that each of the access techniques gives a similar rate of iatrogenic injury.

The battlefield conditions where the …

Growth And Characterization Of Molecular Ferroelectric Thin Films, Yifan Yuan

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Compared with inorganic ferroelectrics, organic ferroelectrics have advantages of low cost and low toxicity, are in increasing demand in capacitors, piezoelectric, and memory devices to reduce the environmental load. This work focuses on two types of organic molecular ferroelectric materials, croconic acid (CA) and 2-methylbenzimidazole (MBI). The work here introduces several origins of ferroelectricity in typical organics and their switching mechanism. We then investigated the nucleation, growth, and ferroelectric measurements of CA thin films. We explored the effect of substrate temperature and an external electric field on the nucleation and growth processes. The results can be used to improve the …

In-Service Performance Evaluation And Installation Recommendations For Cable Median Barriers On Non-Continuously Shielded, Divided-Median Kansas Freeways, Nathan Dowler

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The Kansas Department of Transportation (KDOT) installed 7.95 miles of cable median barrier (CMB) along K-10, K-96, and US-75 freeways in 2011 and 2012. In January 2020, KDOT funded a study to determine the in-service performance of its CMBs. In addition, KDOT sought to determine if it was cost-effective to modify guidelines for installing median barriers, which were based on annual daily traffic and median width.

Researchers reviewed every crash within approximately ¼ mile of a CMB installation and extracted crashes which involved a CMB impact. Researchers analyzed the critical details of each CMB crash, with particular emphasis on penetrations, …

On Road Coordinates For Autonomous Vehicle Guidance, Ricardo Jacome

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

A new roadmap framework is proposed to improve the guidance and trajectory prediction capabilities of connected and automated vehicles (CAVs). Independent of road shape determination through external sensors, the system serves as a backup for challenging conditions, such as low sensor visibility and adverse environmental effects (e.g., rain, fog, snow). Based on the fusion of vehicle dynamics principles, differential geometry, and road design standards, the roadmap framework provides a consolidated collection of critical reference points of roadway centerlines and information about the shape of the roadway in the vicinity of a vehicle, including curvature, optimal travel velocity, and road alignment …

Research Trend Of Metal Matrix Composites Reinforced With Silica Extracted By Green Route: A Bibliometric Analysis, Rinku Datkhile, Meena Laad, Babaji Ghule

Library Philosophy and Practice (e-journal)

Metal Matrix Composites have acquired an important place in the engineering applications due to their distinctive characteristics such as high specific strength, lower specific gravity, improved material stiffness, better durability, enhanced creep and fatigue strength etc. Worldwide scientists are working on the improvement of mechanical properties of composite materials. The present work attempts to summarise all the research carried out on metal matrix composites reinforced with silica extracted by green route and provides up-to-date research material for researchers who are interested in the field of composites with metal matrices. Scopus databases and software such as Gephi Vos Viewer and Table2Net …

Surface Acoustic Waves Increase Magnetic Domain Wall Velocity, Anil Adhikari, Shireen Adenwalla

Shireen Adenwalla Papers

Domain walls in magnetic thin films are being explored for memory applications and the speed at which they move has acquired increasing importance. Magnetic fields and currents have been shown to drive domain walls with speeds exceeding 500 m/s. We investigate another approach to increase domain wall velocities, using high frequency surface acoustic waves to create standing strain waves in a 3 micron wide strip of magnetic film with perpendicular anisotropy. Our measurements, at a resonant frequency of 248.8 MHz, indicate that domain wall velocities increase substantially, even at relatively low applied voltages. Our findings suggest that the strain wave …