Mechanics of Materials Commons^™

Implementation Of New System For Oxygen Generation And Carbon Dioxide Removal, Angelo Peter Karavolos

Open Access Theses & Dissertations

This research effort develops an integrated system for CO2 removal and O2 production. A unique material, dodeca-tungsto-phosphoric acid (H3PO4W12O3; henceforth referred to as DTPA) is mixed with tetra-ethyl-ortho-silicate Si(OC2H5)4 or TEOS. This mixture exhibits unique properties of heat absorption and high electrical conductivity. In the system described herein, the DTPA resides within a cross linked arrangement of TEOS. The DTPA furnishes a source of O2, while the TEOS furnishes structural support for the large DTPA crystals. In addition, the large amount of H2O within the crystal also adsorbs CO2. It can also be cross-linked with other polymers such as polycarbonate, …

Vascularization In Interconnected 3d Printed Ti-6al-4v Foams With Hydrogel Matrix For Biomedical Bone Replacement Implants, Victor Correa

Open Access Theses & Dissertations

Abstract:

Vascularization or angiogenesis on newly implanted metal orthopedic implants has remained a challenge in the field of tissue engineering. In this research, an interconnected foam structure of Ti-6Al-4V was micro-fabricated by Electron Beam Melting (EBM) technique. The foam in question has a density of 1.77g/cm3 with 60% porosity and a tensile strength of 18GPa. An Extracellular Matrix based hydrogel was added as an aqueous matrix to the foam in question. Hypoxia mimetic stress has been closely related to many wound healing biomedical applications as it increases survival and proliferation molecular signals. To that end, increased expression of Hypoxia-Inducible Factor-1α …

A Cracking Methodology To Assess Fracture And Fatigue Properties Of Asphalt Concrete Mixtures Using Overlay Tester, Victor M. Garcia

Open Access Theses & Dissertations

Several highway agencies have either implemented or considered implementing performance tests to predict the cracking potential of asphalt concrete (AC) mixtures in the laboratory setting. One such test, the Overlay Tester (OT) test, measures the number of cycles to failure of the AC specimens by simulating the opening and closing of the cracks induced by daily temperature variations and high tensile strain generated by the traffic load. The variability of the OT test results is expressed as a major concern in reliably characterizing the cracking potential of the AC mixes.

The performance of the OT test, in general, and current …

Liquid-Phase Exfoliation Of Two-Dimensional Graphite For Ink-Jet Printing, Monica Michel

Open Access Theses & Dissertations

Over the last decade, the study of two-dimensional (2D) materials has seen an incredible growth due to their unique thermal, mechanical and electronic properties. Solution phase manufacturing offers a way in which they can be produced at large scale by creating dispersions from the exfoliated material. Once created, different options for assembling devices exist. One technique for large scale manufacturing of materials in this form is ink-jet printing, which is a form of additive manufacturing that has proven to be attractive for the printed electronics industry. One challenge that ink-jet printing still faces is the shortage of inks with appropriate …

Wettability Of Magnesium Based Alloys, Victor Manuel Ornelas

Open Access Theses & Dissertations

The premise of this project was to determine the wettability behavior of Mg-based alloys using three different liquids. Contact angle measurements were carried out along with utilizing the Zisman method for obtaining values for the critical surface tension. Adhesion energy values were also found through the use of the Young-Dupre equation. This project utilized the Mg-based alloy Mg-2Zn-2Gd with supplemented α-Minimum Essential Medium (MEM), Phosphate Buffer Saline solution (PBS), and distilled water. These three liquids are commonly used in cell cultivation and protein adsorption studies. Supplemented α-MEM consisted of α-MEM, fetal bovine serum, and penicillin-streptomycin. Mg-2Zn-2Gd was used because of …

Investigation Of Ti-6al-4v Alloy Response To Atmospheric Re-Entry Exposure, Jessica Lynn Buckner

Open Access Theses & Dissertations

Ti-6Al-4V is a widely used aerospace alloy for its high strength-to-weight ratio and high operating temperature properties. Despite widespread use, titanium and its alloys have been shown to ignite in oxygen and nitrogen rich test streams. The reactivity of titanium is attributed to the high solubility for oxygen that increases with temperature, accelerating the oxidation rate and resulting in a combustion reaction. When introduced to the monatomic oxygen rich and high enthalpy re-entry environment, Ti-6Al-4V X-link components from the space shuttle Columbia exhibited accelerated oxidation and combustion behavior. Ti-6Al-4V metal plates tested in the simulated re-entry environment of an arc-jet …

Low Temperature Solution-Processed Sb:Sno2 Nanocrystals For Efficient Planar Perovskite Solar Cells, Yang Bai, Yanjun Fang, Yehao Deng, Qi Wang, Jingjing Zhao, Xiaopeng Zheng, Yang Zhang, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Inorganic metal oxide electron-transport layers (ETLs) have the potential to yield perovskite solar cells with improved stability, but generally need high temperature to form conductive and defect-less forms, which is not compatible with the fabrication of flexible and tandem solar cells. Here, we demonstrate a facile strategy for developing efficient inorganic ETLs by doping SnO₂ nanocrystals (NCs) with a small amount of Sb using a low-temperature solution-processed method. The electrical conductivity was remarkably enhanced by Sb-doping, which increased the carrier concentration in Sb:SnO₂ NCs. Moreover, the upward shift of the Fermi level owing to doping results in improved …

Propagation Of Extensional Waves In A Piezoelectric Semiconductor Rod, C.L. Zhang, X. Y. Wang, W. Q. Chen, J. S. Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We studied the propagation of extensional waves in a thin piezoelectric semiconductor rod of ZnO whose c-axis is along the axis of the rod. The macroscopic theory of piezoelectric semiconductors was used which consists of the coupled equations of piezoelectricity and the conservation of charge. The problem is nonlinear because the drift current is the product of the unknown electric field and the unknown carrier density. A perturbation procedure was used which resulted in two one-way coupled linear problems of piezoelectricity and the conservation of charge, respectively. The acoustic wave and the accompanying electric field were obtained from the equations …

In Situ Microscopy Of The Self-Assembly Of Branched Nanocrystals In Solution, Eli Sutter, Peter Sutter, Alexei V. Tkachenko, Roman Krahne, Joost De Graaf, Milena Arciniegas, Liberato Manna

Department of Mechanical and Materials Engineering: Faculty Publications

Solution-phase self-assembly of nanocrystals into mesoscale structures is a promising strategy for constructing functional materials from nanoscale components. Liquid environments are key to self-assembly since they allow suspended nanocrystals to diffuse and interact freely, but they also complicate experiments. Real-time observations with single-particle resolution could have transformative impact on our understanding of nanocrystal self-assembly. Here we use real-time in situ imaging by liquid-cell electron microscopy to elucidate the nucleation and growth mechanism and properties of linear chains of octapod-shaped nanocrystals in their native solution environment. Statistical mechanics modelling based on these observations and using the measured chain-length distribution clarifies the …

Influence Of Shear Stress Magnitude And Direction On Atherosclerotic Plaque Composition, Ryan M. Pedrigi, Vikram V. Mehta, Sandra M. Bovens, Zahra Mohri, Christian Bo Poulsen, Willy Gsell, Jordi L. Tremoleda, Leila Towhidi, Ranil De Silva, Enrico Petretto, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

The precise flow characteristics that promote different atherosclerotic plaque types remain unclear. We previously developed a blood flow-modifying cuff for ApoE^−/− mice that induces the development of advanced plaques with vulnerable and stable features upstream and downstream of the cuff, respectively. Herein, we sought to test the hypothesis that changes in flow magnitude promote formation of the upstream (vulnerable) plaque, whereas altered flow direction is important for development of the downstream (stable) plaque. We instrumented ApoE^−/− mice (n=7) with a cuff around the left carotid artery and imaged them with micro-CT (39.6 μm resolution) eight to nine weeks …

Methodology For Analyzing Epoxy-Cnt Phononic Crystals For Wave Attenuation And Guiding, Madhu Kolati

Dissertations, Master's Theses and Master's Reports

Phononic crystals (PhnCs) control, direct and manipulate sound waves to achieve wave guiding and attenuation. This dissertation presents methodology for analyzing nanotube materials based phononic crystals to achieve control over sound, vibration and stress mitigation. Much of the analytical work presented is in identifying frequency band gaps in which sound or vibration cannot propagate through these PhnCs. Wave attenuation and mitigation analysis is demonstrated using finite element simulation. Engineering principles from current research areas of solid mechanics, solid-state physics, elasto-dynamics, mechanical vibrations and acoustics are employed for the methodology. A considerable effort is put to show that these PhnCs can …

The University Of Akron Human Powered Vehicle Team, Maria E. Rizzo, Andrew J. Derhammer, Christopher M. Trowbridge, Timothy M. Nutt, Joseph R. Boyd, Jeremy W. Marcum, Jonathan E. Adams, Donald G. Haiss, Julia Wood, Brian D. Goshia, Scott T. Fagan, Joshua D. Everhard, Rebecca L. Slivka

Williams Honors College, Honors Research Projects

The University of Akron Human Powered Vehicle Team’s 2016 vehicle, Klokan, was designed, manufactured and tested with safety, reliability, performance and ease of use in mind. The vehicle is a fully faired tadpole trike with a lightweight aluminum frame constructed from 6061-T6 tubing having a total weight of 8.9 lbs. To complement the lightweight frame, the fairing is constructed from polycarbonate, PETG and carbon fiber strips which combine into a lightweight, easy to manufacture weather barrier and aerodynamic structure. Klokan was designed to be a safe and efficient mode of everyday transportation which ensures that riders are sufficiently protected by …

Stress-Dependent Ultrasonic Scattering In Polycrystalline Materials, Christopher M. Kube, Christopher A Turner

Department of Mechanical and Materials Engineering: Faculty Publications

Stress-dependent elastic moduli of polycrystalline materials are used in a statistically based model for the scattering of ultrasonic waves from randomly oriented grains that are members of a stressed polycrystal. The stress is assumed to be homogeneous and can be either residual or generated from external loads. The stress-dependent elastic properties are incorporated into the definition of the differential scattering cross-section, which defines how strongly an incident wave is scattered into various directions. Nine stress-dependent differential scattering cross-sections or scattering coefficients are defined to include all possibilities of incident and scattered waves, which can be either longitudinal or (two) transverse …

Portable Camera Aided Simulator (Portcas) For Minimally Invasive Surgical Training, Ka-Chun Sui, Carl Nelson, Mohsen Zahiri, Dmitry Oleynikov

Department of Mechanical and Materials Engineering: Faculty Publications

The present disclosure is directed to a system and method for surgical training with low cost, reusable materials and a highly customizable virtual environment for skill-building. According to various embodiments, a surgical training tool is usable in conjunction with a support structure configured to at least partially constrain the tool movement. Meanwhile, the tool is tracked in real-time with off-tool detectors to generate a tool path driving a virtual rendering of the surgical training tool in an operative environment. The virtual rendering may be visually observable via a display device and may include a customizable and/or selectable operative environment with …

Field-Scale Testing And Numerical Investigation Of Soil-Boulder Interaction Under Vehicular Impact Using Fem And Coupled Fem-Sph Formulations, Lynsey Reese, Tong Qiu, Daniel Linzell, Zoltan Rado

Department of Civil and Environmental Engineering: Faculty Publications

A computational approach that couples the Finite Element Method and the Smoothed Particle Hydrodynamics method may be advantageous for simulating the response of complex, physical systems involving large deformations. However, comparisons of this modeling technique against field-scale test data are remarkably sparse in literature. This study presents three field-scale tests involving vehicular impact into three landscape vehicular anti-ram barriers. Each barrier consisted of a single boulder embedded in compacted American Association of State Highway and Transportation Officials soil and physical testing resulted in one of the following outcomes: minimal boulder/soil movement (Test 1), moderate boulder/soil movement (Test 2), and severe …

Matl 260/360: Elements Of Materials Science—A Peer Review Of Teaching Project Benchmark Portfolio, Bai Cui

UNL Faculty Course Portfolios

The goal of MATL 260/360 Elements of Materials Science is to make undergraduate students understand the fundamental concepts of the microstructure-property relationship of materials. This course portfolio addresses several key questions in teaching, such as how to teach new knowledge more effectively, how to increase student engagement, how to promote students’ interests and motivations, and how to use this course to improve students’ analysis and critical thinking skills.

To address each of key questions, the course activities include: relating the new knowledge with daily-life and industry examples; giving PPT slides for after- class study; assigning homework questions after each lecture; …

Characterization In 2d Sulfides And Graphene Composites For Sensing Applications, Alberto Delgado

Open Access Theses & Dissertations

In this work, we have evaluated 2D layered material composites for opto-electro-mechanical sensing applications. In particular, we have focused on TMDCs and graphite and studied the effects of chemical liquid exfoliation on the structural characteristics of the 2D layered materials, through particle size, x-ray diffraction, Raman and surface area analysis. An approach was developed to combine the solution-processed dispersion with organic and inorganic matrix materials for forming the composites. From Raman Spectroscopy of the ultra-sonicated samples, the I2D/IG>2 for graphite, and for MoS2 the difference between the A1g and E2g peak was 22.85cm-1, consistent with few layer 2D MoS2. …

Damage Tolerance And Assessment Of Unidirectional Carbon Fiber Composites, Mark David Flores

Open Access Theses & Dissertations

Composites are beginning to be used in a variety of different applications throughout industry. However, certification and damage tolerance is a growing concern in many aerospace and marine applications. Although compression-after-impact have been studied thoroughly, determining a damage tolerance methodology that accurately characterizes the failure of composites has not been established. An experimental investigation was performed to study the effect of stacking sequence, low-velocity impact response, and residual strength due to compression and fatigue. Digital Image Correlation (DIC) captured the strains and deformation of the plate due to compression. Computational investigations integrated non-destructive techniques (C-Scan, X-Ray) to determine the extent …

Molecular Dynamics Proxy Applications For Optimizing Performance Of Simulations Under Extreme Conditions, Jayalath Abeywardhana Mudiyanselage Madawa Abeywardhana

Open Access Theses & Dissertations

Exascale performance of scientific application is a prominent goal for the scientific community and computer hardware vendors. As a result, several proxy applications for the widely used scientific codes have been developed with the purpose of testing performance, memory and power consumption issues associated with simulations at the exascale. Co-MD is a proxy application for classical Molecular Dynamics (MD) codes based on the (SPaSM) Los Alamos code.

This work comprises two different but related computational aspects: performance evaluation and optimization of Co-MD (Co-Design Molecular Dynamics) for different computer architectures/execution models, and direct application of SPaSM (Scalable Parallel Short-range Molecular Dynamics) …

Yttria Rich Tbcs As Candidates For Cmas Resistant Top Coats, Juan Jose Gomez

Open Access Theses & Dissertations

State of the art thermal barrier coatings (TBC) commonly made of 7-8 wt. % yttria stabilized zirconia (7YSZ) are used in modern gas turbines to generate a thermal protection to the underlying super alloy components. TBCs allow higher operating temperatures for hot gas path components, thus, generating higher engine efficiency. The infiltration of molten glassy mineral deposits composed of CaO-MgO-Al2O3-SiO2 (CMAS) represents one of the major threats in reducing performance and service life in aero and land based gas turbine engines. The CMAS deposits are ingested into the engine carried commonly in sand, runways debris, fly ash and volcanic ash. …