Mechanics of Materials Commons^™

Heterogeneous Integration Of Metallic, Semiconducting And Dielectric Two-Dimensional Layered Material Inks For Electronics And Sensing Device Platforms, Jay Amrish Desai

Open Access Theses & Dissertations

In monolayers of two-dimensional (2-D) layered materials, the motion of electrons is confined to a 2-D plane yielding a "zero" effective thickness with regard to the electrons. These monolayers are commonly obtained by exfoliating membranes from the bulk crystal to overcome the weak interplanar Van der Waals bonding using the so-called top-down approach. The bottom-up approach is another avenue to realize these materials, where atoms and molecules coalesce together into increasingly larger assemblies for the realization of the bulk three-dimensional (3-D) crystal. The unique properties of many of these 2-D materials make them highly sought out candidates for advancing conventional …

A New Approach To Multiplanar, Real-Time Simulation Of Physiological Knee Loads And Synthetic Knee Components Augmented By Local Composition Control In Fused Filament Fabrication, Joshua Taylor Green

Open Access Theses & Dissertations

Despite numerous advances in biomedical engineering, few developments in surgical simulation have been made outside of computational models. Cadavers remain the primary media on which surgical research and simulation is conducted. Most attempts to quantify the effects of orthopedic surgical methods fail to achieve statistical significance due to limited quantities of cadaver specimen, large variations among the cadaver population, and a lack of repeatability among measurement techniques. The general purpose of the research covered in this dissertation is to develop repeatable simulation of physiological loads and develop techniques to fabricate a synthetic-based replacement of cadaver specimens. Future work applying this …

Structural And Optical Investigations Of Rbxcs1-Xh2po4, Alex D. Price

Open Access Theses & Dissertations

Proton conductor solid acid electrolytes RbxCs1-xH2PO4 (0≤x≤1) have been investigated using second harmonic generation and powder x-ray diffraction. Second harmonic generation is an optical technique which can be used to study the structural properties of materials. Microscopes of this nature have the ability to image objects with a variable penetration depth in a non-destructive manner, allowing for great potential to be used for in situ observations of the electrolyte’s structure when in a fuel cell under operating conditions.

X-ray powder diffraction was carried out on the series of samples and found for values of 0≤x≤0.5 the structure of the material …

Titanium Incorporated Gallium Oxide (Ga-Ti-O): Structure Property Relationship And Performance Evaluation For Extreme Environment Applications, Sandeep Manandhar

Open Access Theses & Dissertations

The existing power generation systems, which utilize fossil fuels, are in dire need of efficient, reliable chemical sensors that can operate safely at higher temperatures. These sensors control the combustion environment and the emissions during combustion. Several sensing materials such as SnO2, ZnO, TiO2, WO3, and Ga2O3 exhibit high sensitivity to certain type of chemical molecules and in a certain range of temperatures. Among these candidate materials, β-Ga2O3 is stable at very high temperatures and has shown functionality for oxygen sensing at higher temperatures (>700°C). However, the response time and sensitivity must be significantly improved in order to derive …

Streamlining Alloy Design And Thermo-Mechanical Processing Parameters For High Strength Line Pipe Steels And Hot Rolled Microalloyed Steels: Process - Structure - Property Paradigm, Venkata Vignesh Natarajan

Open Access Theses & Dissertations

The process parameters related to thermo-mechanical controlled processing (TMCP) of steels play a vital role in affecting the ultimate mechanical properties. We illustrate here the impact of coiling temperature, the impact of finish cooling temperature on interrupted cooling and compare with continuous cooling, and the impact of carbon and niobium on the microstructure and precipitation behavior and corresponding changes in mechanical properties, in an ultrahigh strength titanium-niobium microalloyed steel. The microstructural advancement was contemplated via transmission electron microscopy and electron backscattered diffraction (EBSD). The goal was to underscore the impact of coiling temperature on the nature and distribution of microstructural …

Evaluation Of Large Area Additively Manufactured Fiber Reinforced Acrylonitrile Butadiene Styrene (Abs), Kevin Schnittker

Open Access Theses & Dissertations

To enable the advancement of large-scale additive manufacturing processes, it is necessary to establish and standardize methodologies to characterize the mechanical properties of printed test coupons. Due to the large size of the print beads, conventional test standards are inadequate. The focus of this study was to determine the feasibility of using Digital image correlation (DIC) technology as a key enabler for robust data collection of strain measurements of large 3D printed parts. To incorporate the DIC measurements, a novel method was developed to prepare large 20 wt.% glass filled ABS test coupons for adequate contrast. Through this technique, Poisson's …

Flow Patterns Through Vascular Graft Models With And Without Cuffs, Chia Min Leong, Gary B. Nackman, Timothy Wei

Department of Mechanical and Materials Engineering: Faculty Publications

The shape of a bypass graft plays an important role on its efficacy. Here, we investigated flow through two vascular graft designs±with and without cuff at the anastomosis. We conducted Digital Particle Image Velocimetry (DPIV) measurements to obtain the flow field information through these vascular grafts. Two pulsatile flow waveforms corresponding to cardiac cycles during the rest and the excitation states, with 10% and without retrograde flow out the proximal end of the native artery were examined. In the absence of retrograde flow, the straight end-to-side graft showed recirculation and stagnation regions that lasted throughout the full cardiac cycle with …

Dislocations Interaction Induced Structural Instability In Intermetallic Al2cu, Qing Zhou, Jian Wang, Amit Misra, Ping Huang, Fei Wang, Kewei Xu

Department of Mechanical and Materials Engineering: Faculty Publications

Intermetallic precipitates are widely used to tailor mechanical properties of structural alloys but are often destabilized during plastic deformation. Using atomistic simulations, we elucidate structural instability mechanisms of intermetallic precipitates associated with dislocation motion in a model system of Al₂Cu. Interaction of non-coplanar <001> dislocation dipoles during plastic deformation results in anomalous reactions—the creation of vacancies accompanied with climb and collective glide of <001> dislocation associated with the dislocation core change and atomic shuffle—accounting for structural instability in intermetallic Al₂Cu. This process is profound with decreasing separation of non-coplanar dislocations and increasing temperature and is likely to be …

Mechanical Performance Of Plla Stent, Longzhen Wang, Junfei Tong, Pengfei Dong, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Stent implantation is widely used to treat blocked lumen. Stents were meshed structure made of polymers and metal alloys, including stainless steel, cobalt chrome and nitinol [1]. Clinical studies had demonstrated that stents helped to scaffold the diseased lesion up to one year when tissue adapted to the stented environment [2]. However, the permanently implanted stents inside artery were associated with complications such as stent fracture, tissue inflammation, in-stent restenosis and thrombosis [3]. Currently, biodegradable stents are attracting more attention due to its potential long-term efficacy in treating blocked lumens. The detailed characterizations of biodegradable stents are essential for the …

Plaque Burden Influences Accurate Classification Of Fibrous Cap Atheroma By In-Vivo Optical Coherence Tomography In A Porcine Model Of Advanced Coronary Atherosclerosis., Christian B. Poulsen, Ryan M. Pedrigi, Nilesh Pareek, Ismail D. Kilic, Niels R. Holm, Jacob F. Bentzon, Hans Erik Botker, Erling Falk, Rob Krams, Ranil De Silva

Department of Mechanical and Materials Engineering: Faculty Publications

Advanced coronary atherosclerosis assessed by in-vivo optical coherence tomography (OCT) has not been directly compared with histology. In a porcine model with human-like coronary atherosclerosis we compared in-vivo OCT images with histology in five animals. We found a high sensitivity but modest specificity of OCT in classifying fibrous cap atheroma (FCA). The modest specificity was caused by misclassification of FCA lesions as pathological intimal thickening. The misclassification most frequently occurred when plaque burden exceeded ~20%. Compared with histology, OCT has high sensitivity but modest specificity for identifying FCA. The study suggests that plaque burden should be considered when interpreting OCT …

Multifunctional Operational Component For Robotic Devices, Shane M. Farritor, Amy Lehman, Mark Rentschler

Department of Mechanical and Materials Engineering: Faculty Publications

The various embodiments disclosed herein relate to modular medical devices, including various devices with detachable modular components and various devices with pivotally attached modular components. Additional embodiments relate to procedures in which various of the devices are used cooperatively. Certain embodiments of the medical devices are robotic in vivo devices.

Scaffold Structural Microenvironmental Cues To Guide Tissue Regeneration In Bone Tissue Applications, Xuening Chen, Hongyuan Fan, Xiaowei Deng, Lina Wu, Tao Yi, Linxia Gu, Changchun Zhou, Yujiang Fan, Xingdong Zhang

Department of Mechanical and Materials Engineering: Faculty Publications

In the process of bone regeneration, new bone formation is largely affected by physico-chemical cues in the surrounding microenvironment. Tissue cells reside in a complex scaffold physiological microenvironment. The scaffold should provide certain circumstance full of structural cues to enhance multipotent mesenchymal stem cell (MSC) differentiation, osteoblast growth, extracellular matrix (ECM) deposition, and subsequent new bone formation. This article reviewed advances in fabrication technology that enable the creation of biomaterials with well-defined pore structure and surface topography, which can be sensed by host tissue cells (esp., stem cells) and subsequently determine cell fates during differentiation. Three important cues, including scaffold …

Heat Transfer Across A Nanoscale Pressurized Air Gap And Its Application In Magnetic Recording, Jinglin Zheng, Yung-Kan Chen, Qin Zhou

Department of Mechanical and Materials Engineering: Faculty Publications

In this study, we investigated how a thermally actuated air bearing slider heats up a fast-spinning storage disk through a highly pressurized nanoscale air gap in a magnetic recording system. A Euleriandescription- based computational approach is developed considering heat conduction through a pressurized air film and near-field radiation across the gap. A set of field equations that govern the air bearing dynamics, slider thermo-mechanics and disk heat dissipation are solved simultaneously through an iterative approach. A temperature field on the same order as the hot slider surface itself is found to be established in the disk. The effective local heat …

Interfacial Characterization By Pull-Out Test Of Bamboo Fibers Embedded In Poly(Lactic Acid), Quentin Viel, Antonella Esposito, Jean-Marc Saiter, Carlo Santulli, Joseph A. Turner

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, the apparent shear strength at the interface between a bamboo fiber and the surrounding poly(lactic acid) (PLA) matrix is quantified. A method for processing pull-out test samples within a controlled embedded length is proposed and the details of the test procedure are presented, along with a critical discussion of the results. Two series of samples are considered: untreated and mercerized bamboo fibers from the same batch, embedded in the same polyester matrix. Electron and optical microscopy are used to observe the fiber–matrix interface before and after the test, and to identify the failure mode of each sample, …

Complementary Microscopy Techniques Applied For Characterizing The Localized Nanoscale Structure Of Poly (Vinylidene Fluoride), Wen Qian, Shuo Sun, Charles Nguyen, Wenlong Li, Stephen Ducharme, Joesph A. Turner

Department of Mechanical and Materials Engineering: Faculty Publications

Poly (vinylidenefluoride) (PVDF), a well-recognized electroactive polymer, has been studied extensively over many decades. Recently, there has been increasing interest in tuning the electrical properties of PVDF from ferroelectric to piezoelectric and to pyroelectric, which can be attained via controlling the microscale structure down to the nanoscale structure [1-2]. To optimize the preparation conditions of PVDF and its copolymers, as well as to improve the performance for many applications, comprehensive analytical techniques are of great importance. In this paper, we demonstrate complementary nanoscale characterization and measurement techniques, by conducting a systematic and coordinated study involving scanning electron microscopy (SEM), high …

Improved A-B10C2+XHY/Si P-N Heterojunction Performance After Neutron Irradiation, George Peterson, Qing Su, Yongqiang Wang, Natale J. Ianno, Peter Dowben, Michael Nastasi

Department of Mechanical and Materials Engineering: Faculty Publications

The impact of neutron irradiation, in the energy range of ~0.025 eV, on amorphous semiconducting partially dehydrogenated boron carbide (a-B₁₀C_2+xH_y) on silicon p-n heterojunction diodes was investigated. The heterojunction devices were created by synthesizing a-B₁₀C_2+xH_y via plasma enhanced chemical vapor deposition on n-type silicon. Unlike many electronic devices, the performance of the a-B₁₀C_2+xH_y heterojunction diode improved with neutron irradiation, in spite of the large neutron cross section of ¹⁰B. There is also increased charge carrier lifetime of more than …

Tissue Stresses In Stented Coronary Arteries With Different Geometries: Effect Of The Relation Between Stent Length And Lesion Length, Xiang Shen, Song Ji, Yong-Quan Deng, Hong-Fei Zhu, Jia-Bao Jiang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In-stent restenosis after stent deployment remains an obstruction in the long-term benefits of stenting. This study sought to investigate the influence of the relation between stent length and lesion length on the mechanics of the arterial wall with different geometries, including straight and tapered vessels. Results showed that when the length of the stent was longer than the lesion length, the maximum stress in plaque and vessel increased as the length of stent increased. When the length of the stent was shorter than the lesion length, the vessel stress induced by stent inflation was lower; both ends of the stenosis …

Experimental Measurement Of Dolphin Thrust Generated During A Tail Stand Using Dpiv, Frank E. Fish, Terrie M. Williams, Erica Sherman, Yae Eun Moon, Vicki Wu, Timothy Wei

Department of Mechanical and Materials Engineering: Faculty Publications

Estimation of force generated by dolphins has long been debated. The problem was that indirect estimates of force production for dolphins resulted in low values that could not be validated. Bubble digital particle image velocimetry (DPIV) measured hydrodynamic force production for swimming dolphins and demonstrated high force production. To validate the bubble DPIV and reconcile force production measurements, two bottlenose dolphins (Tursiops truncatus) performing tail stands were measured with bubble DPIV. Microbubbles were generated from a finely porous hose and compressed air source. Displacement of the bubbles by the propulsive motions of the dolphin was tracked with a …

Structural And Aerodynamic Design, Procedure And Analysis Of A Small V-Shaped Vertical Axis Wind Turbine, Odari J. Whyte

College of Graduate Studies: Theses & Dissertations

Over the last two decades there has been a renewed interest in Vertical Axis Wind Turbines. This turbine configuration though unpopular for large-scale generation has found a niche market in the way of offshore energy harvesting. However, offshore wind has its challenges. In this thesis a detailed comprehensive study of a proposed V-shaped vertical axis turbine rotor is performed in order to examine its structural and aerodynamic characteristics. The design met and exceeded the safety parameters establish for test bed operation, showing a factor of safety of 1.87 with regard to fatigue stress response. A satisfactory fatigue stress design life …

Thermal-Fatigue And Thermo-Mechanical Equivalence For Transverse Cracking Evolution In Laminated Composites, Javier Cabrera Barbero

Graduate Theses, Dissertations, and Problem Reports (ETD)

Carbon fiber reinforced plastics (CFRP) are potential materials for many aerospace and aeronautical applications due to their high specif strength/weight and a low coeffcient of thermal expansion (CTE) resulting in a high long-term stability. Among candidate structures, the re-entry reusable launch vehicles (RLV), the fuel oxidant storage and transportation at cryogenic temperature, space satellites, and aircraft structure (frame, wings, etc...) can be highlighted. However, CFRP are prone to internal damage as a result of high residual stresses and thermal fatigue loading. In this study, micro-cracking damage evolution in laminated composites subjected to monotonic cooling and thermal cyclic loads is developed …

Manufacturing Applications Of The One-Dimensional Cutting Stock Problem As A Team Project, Hüseyin Sarper, Nebojsa I. Jaksic

Electrical & Computer Engineering Faculty Publications

This paper explains the beneficial and practical impact of operations research in two real manufacturing settings. Two manufacturing examples used in student projects were (1) cutting rails (80‘ or 40‘) to manufacture railroad frogs of many sizes and (2) cutting round metal rolls (12‘ to 20‘) to meet customer demands for various lengths of cuts. Student teams in Engineering of Manufacturing Processes and Operations Research courses wrote computer programs. The program first identified all possible patterns that can be cut out of a given stock length. Next, the program created a mathematical model (a text file) as an output. This …

Consuming Digital Debris In The Plasticene, Stephen R. Parks

Theses and Dissertations

Claims of customization and control by socio-technical industries are altering the role of consumer and producer. These narratives are often misleading attempts to engage consumers with new forms of technology. By addressing capitalist intent, material, and the reproduction limits of 3-D printed objects’, I observe the aspirational promise of becoming a producer of my own belongings through new networks of production. I am interested in gaining a better understanding of the data consumed that perpetuates hyper-consumptive tendencies for new technological apparatuses. My role as a designer focuses on the resolution of not only the surface of the object through 3-D …

Functional Bio-Nano Hybrids Through A Precise Control Of Interfacial Interactions At The Nanoscale, Sirimuvva Tadepalli

McKelvey School of Engineering Graduate Student Theses & Dissertations

During the course of evolution, proteins have evolved to perform exquisite functions including structural support, signal transduction, actuation, sensing, catalysis, trafficking, gating, light-harvesting, charge transfer, molecular recognition, self-assembly, self-organization, or combinations of two or more of these functions. A precise control and manipulation of the structure and function of proteins is conceivable with the advent of nanotechnology, which has facilitated the integration of nanomaterials with functional biomolecules to realize bio-nano hybrids with synergistically enhanced functionalities.

At the genesis of bionanotechnology, a paucity in the fundamental understanding of the bio-nano interfaces is a grave impediment to the progress of the field. …

The Inter-Laminar Shearing Effect On Wrinkle Development In Composite Forming Processes, David Sundquist

McKelvey School of Engineering Graduate Student Theses & Dissertations

Composite materials are becoming prevalent in aerospace industries as the uniqueness of the composite structure allows the composite to be tailored specifically for individual applications. Many fabrication techniques produce defects in composite parts such as wrinkles, fiber waviness, fiber misalignment, and porosity. The driving mechanisms behind these defects occurring during forming processes are not fully understood and, thus, characterization formation of these defects in a uncured state is beneficial to optimize composite processing. This work primarily investigated the influence of how uncured pre-impregnated carbon ply properties affect the wrinkling behavior of a composite laminates. Several factors affecting composite ply forming …

Characterization And Modeling Of Asphalt Concrete For Dynamic Properties And Performances, A S M A. Rahman

Civil Engineering ETDs

The recently developed mechanistic-empirical pavement design guide (MEPDG, also known as Pavement M-E design method) uses the nationally calibrated, binder viscosity-based dynamic modulus predictive model for the design and analysis of asphalt pavements. In this study, this model is assessed for its appropriateness for asphalt-aggregate mixtures typically used in New Mexico. In essence, this study investigates the predictability issue of complex modulus of New Mexico mixes. A total of 54 Superpave mixes with different aggregate gradations, air voids, and binder grades were collected from the mixing plants and from the pavement construction sites. The loose asphalt mixtures were then compacted, …

A Comparison Study Of Composite Laminated Plates With Holes Under Tension, Joun S. Kim

Master's Theses

A Comparison Study of Composite Laminated Plates with Holes under Tension

A study was conducted to quantify the accuracy of numerical approximations to deem sufficiency in validating structural composite design, thus minimizing, or even eliminating the need for experimental test. Error values for stress and strain were compared between Finite Element Analysis (FEA) and analytical (Classical Laminated Plate Theory), and FEA and experimental tensile test for two composite plate designs under tension: a cross-ply composite plate design of [(0/90)4]s, and a quasi-isotropic layup design of [02/+45/-45/902]s, each with a single, centered hole of 1/8” diameter, and 1/4" diameter (four sets …

Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan

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

Vibration membrane equipped for earphone requires high performance in both mechanical properties and electronic properties. With extraordinary properties on both, graphene and graphene-based composite materials appear as a promising candidate for this application. Chemical vapor deposition (CVD) is believed to be the most convenient way to synthesize a large area (on scale of square centimeters) as well as a homogeneous thickness for the membrane. The thesis focuses on applying control variable experiment method to analyze different effects on mechanical property of the two CVD setting parameters: cooling rate, and hydrocarbon precursor. For isolating the specimens efficiently, a modified electrochemical method …

Method For Single Crystal Growth Of Photovoltaic Perovskite Material And Devices, Jinsong Huang, Qingfeng Dong

Department of Mechanical and Materials Engineering: Faculty Publications

Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container , also including at least one small perovskite single crystal , and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows , in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate . For example , a top portion of the substrate external to the solution may be cooled .

Oct-Based Three Dimensional Modeling Of Stent Deployment, Pengfei Dong, David Prabhu, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Stent deployment has been widely used to treat narrowed coronary artery. Its acute outcome in terms of stent under expansion and malapposition depends on the extent and shape of calcifications. However, no clear understanding as to how to quantify or categorize the impact of calcification. We have conducted ex vivo stenting characterized by the optical coherence tomography (OCT). The goal of this work is to capture the ex vivo stent deployment and quantify the effect of calcium morphology on the stenting. A three dimensional model of calcified plaque was reconstructed from ex vivo OCT images. The crimping, balloon expansion and …

Multiple Scattering Theory For Polycrystalline Materials With Strong Grain Anisotropy: Theoretical Fundamentals And Applications, Huijing He

Department of Mechanical and Materials Engineering: Faculty Publications

This work is a natural extension of the author’s previous work: “Multiple scattering theory for heterogeneous elastic continua with strong property fluctuation: theoretical fundamentals and applications” (arXiv:1706.09137 [physics.geo-ph]), which established the foundation for developing multiple scattering model for heterogeneous elastic continua with either weak or strong fluctuations in mass density and elastic stiffness. Polycrystalline material is another type of heterogeneous materials that widely exists in nature and extensively used in industry. In this work, the corresponding multiple scattering theory for polycrystalline materials with randomly oriented anisotropic crystallites is developed. To validate the theory, the theoretical results for a series of …