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Articles 1 - 30 of 71
Full-Text Articles in Engineering
Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu
Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu
Doctoral Dissertations
A number of computational methodologies have been developed to investigate the deformation and damage mechanism of various structural materials at different length scale and under extreme loading conditions, and also to provide insights in the development of high-performance materials.
In microscopic material behavior and failure modes, polycrystalline metals of interest include heterogeneous deformation field due to crystalline anisotropy, inter/intra grain or phase and grain boundary interactions. Crystal plasticity model is utilized to simulate microstructure based polycrystalline materials, and micro-deformation information, such as lattice strain evolution, can be captured based on crystal plasticity finite element modeling (CPFEM) in ABAQUS. The comparison …
Process Development For Compression Molding Of Hybrid Continuous And Chopped Carbon Fiber Prepreg For Production Of Functionally Graded Composite Structures, Corinne Marie Warnock
Process Development For Compression Molding Of Hybrid Continuous And Chopped Carbon Fiber Prepreg For Production Of Functionally Graded Composite Structures, Corinne Marie Warnock
Master's Theses
Composite materials offer a high strength-to-weight ratio and directional load bearing capabilities. Compression molding of composite materials yields a superior surface finish and good dimensional stability between component lots with faster processing compared to traditional manufacturing methods. This experimental compression molding capability was developed for the ME composites lab using unidirectional carbon fiber prepreg composites. A direct comparison was drawn between autoclave and compression molding methods to validate compression molding as an alternative manufacturing method in that lab. A method of manufacturing chopped fiber from existing unidirectional prepreg materials was developed and evaluated using destructive testing methods. The results from …
Imaging Thermal Conductivity With Nanoscale Resolution Using A Scanning Spin Probe, Abdelghani Laraoui, Halley Aycock-Rizzo, Yang Gao, Xi Lu, Elisa Riedo, Carlos A. Meriles
Imaging Thermal Conductivity With Nanoscale Resolution Using A Scanning Spin Probe, Abdelghani Laraoui, Halley Aycock-Rizzo, Yang Gao, Xi Lu, Elisa Riedo, Carlos A. Meriles
Department of Mechanical and Materials Engineering: Faculty Publications
The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the nitrogen vacancy to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. By combining atomic force and confocal microscopy, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. …
Effect Of Processing History And Material Properties On The Growth Of Wrinkle Amplitude, Yu-Cheng Chen
Effect Of Processing History And Material Properties On The Growth Of Wrinkle Amplitude, Yu-Cheng Chen
Doctoral Dissertations
Wrinkling has been employed by many organisms to form unique topography, such as fingerprints, gut villi, and surface of flower petal cells. The wavy wrinkle structure provides friction enhancement, surface area increase, optical, and wetting properties improvement. Inspired by Nature, scientists have created wrinkles synthetically and proposed numerous uses for them. However, wrinkling surfaces encounters limitations on achieving massive area and high amplitude-to-wavelength ratio (aspect ratio). The three phase contact line wrinkling technique creates well-defined wrinkles in a continuous fashion, and has great potential to scale-up for massive production. In addition to the velocity dependent adhesion force, we find the …
Pattern Formation Of Elastic Waves And Energy Localization Due To Elastic Gratings, A. Berezovski, J. Engelbrecht, Mihhail Berezovski
Pattern Formation Of Elastic Waves And Energy Localization Due To Elastic Gratings, A. Berezovski, J. Engelbrecht, Mihhail Berezovski
Publications
Elastic wave propagation through diffraction gratings is studied numerically in the plane strain setting. The interaction of the waves with periodically ordered elastic inclusions leads to a self-imaging Talbot effect for the wavelength equal or close to the grating size. The energy localization is observed at the vicinity of inclusions in the case of elastic gratings. Such a localization is absent in the case of rigid gratings.
Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou
Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou
Electronic Thesis and Dissertation Repository
Dielectric elastomer transducers with large deformation, high energy output, light weight and low cost have been drawing great interest from both the research and industry communities, and shown potential for versatile applications in biomimetics, dynamics, robotics and energy harvesting. However, in addition to multiple failure modes such as electrical breakdown, electromechanical instability, loss-of-tension and fatigue, the performance of dielectric elastomer transducers are also strongly influenced by the hyperelastic and viscoelastic properties of the material. Also, the interplay among these material properties and the failure modes is rather difficult to predict. Therefore, in order to provide guidelines for the optimal design …
System And Method For Estimating States Of Spacecraft In Planet-Moon Environment, Piyush Grover
System And Method For Estimating States Of Spacecraft In Planet-Moon Environment, Piyush Grover
Department of Mechanical and Materials Engineering: Faculty Publications
A method estimates a state of a spacecraft in a planet-moon environment by executing iteratively a particle filter. The particle filter comprising integrates individually states of each particle of the particle filter according to a probability-evolution equation using a model of the state of the spacecraft represented as a planar circular restricted three-body problem and determines a prior probability of each particle as a previous posterior probability of a corresponding particle during a previous iteration. A joint probability distribution of the state of the spacecraft is determines using the states of each particle and the prior probabilities of each particle …
Mimicking The Arterial Microenvironment With Peg-Pc To Investigate The Roles Of Physicochemical Stimuli In Smc Phenotype And Behavior, William G. Herrick
Mimicking The Arterial Microenvironment With Peg-Pc To Investigate The Roles Of Physicochemical Stimuli In Smc Phenotype And Behavior, William G. Herrick
Doctoral Dissertations
The goal of this dissertation was to parse the roles of physical, mechanical and chemical cues in the phenotype plasticity of smooth muscle cells (SMCs) in atherosclerosis. We first developed and characterized a novel synthetic hydrogel with desirable traits for studying mechanotransduction in vitro. This hydrogel, PEG-PC, is a co-polymer of poly(ethylene glycol) and phosphorylcholine with an incredible range of Young’s moduli (~1 kPa - 9 MPa) that enables reproduction of nearly any tissue stiffness, exceptional optical and anti-fouling properties, and support for covalent attachment of extracellular matrix (ECM) proteins. To our knowledge, this combination of mechanical range, low …
Effect Of Surface Omniphobicity On Drying By Forced Convection, Madani A. Khan, Jeffrey Alston, Andrew Guenthner
Effect Of Surface Omniphobicity On Drying By Forced Convection, Madani A. Khan, Jeffrey Alston, Andrew Guenthner
STAR Program Research Presentations
Low energy surfaces can strongly repel both oil and water. Recently these surfaces have been fabricated on various substrates including fabric, aluminum, stainless steel and many other materials. In this experiment we explore the use of low energy surface deposition on aluminum alloy, stainless steel and silicon substrates, to enhance the drying rate of liquids removed from the surface by forced convection. We control surface roughness by substrate abrasion and by the growth of Al2O3 nanograss to enhance liquid repellence by use of a hierarchical texture. Liquid repellence of the substrates is measured by contact angles of …
An Estimate Of The Second-Order In-Plane Acceleration Sensitivity Of A Y-Cut Quartz Thickness-Shear Resonator, Huijing He, Jiashi Yang, John A. Kosinski
An Estimate Of The Second-Order In-Plane Acceleration Sensitivity Of A Y-Cut Quartz Thickness-Shear Resonator, Huijing He, Jiashi Yang, John A. Kosinski
Department of Mechanical and Materials Engineering: Faculty Publications
We perform a theoretical analysis of the second-order in-plane acceleration sensitivity of a Y-cut quartz thick-ness-shear mode resonator. The second-order nonlinear theory of elasticity for anisotropic crystals is used to determine the biasing fields in the resonator under in-plane acceleration. The acceleration-induced frequency shift is determined from a per-turbation analysis based on the plate equations for small-amplitude vibrations superposed on a finite bias. We show that, whereas the first-order acceleration-induced frequency shift is zero for a structurally symmetric resonator under in-plane ac-celeration, the second-order frequency shift is nonzero and is quadratic in the acceleration. As the fourth-order nonlinear elastic constants …
Biodegradable Medical Device Having An Adjustable Degradation Rate And Methods Of Making The Same, Yuebin Guo, Michael Sealy, Meisam Salahshoor Pirsoltan
Biodegradable Medical Device Having An Adjustable Degradation Rate And Methods Of Making The Same, Yuebin Guo, Michael Sealy, Meisam Salahshoor Pirsoltan
Department of Mechanical and Materials Engineering: Faculty Publications
Disclosed herein are biodegradable medical devices comprising biodegradable material (e.g., magnesium-calcium alloys) having an adjustable rate of degradation that can be used in various applications, including, but not limited to, drug delivery applications, cardiovascular applications, and orthopedic applications to make biodegradable and biocompatible devices. Also disclosed herein are methods of making biodegradable medical devices comprising biodegradable materials by using, for instance, hybrid dry cutting/hydrostatic burnishing.
Traction-Separation Relationships For Hydrogen-Induced Grain Boundary Embrittlement In Nickel Via Molecular Dynamics Simulations, Wesley Allen Barrows
Traction-Separation Relationships For Hydrogen-Induced Grain Boundary Embrittlement In Nickel Via Molecular Dynamics Simulations, Wesley Allen Barrows
Graduate Theses and Dissertations
The deleterious effects of atomic and molecular hydrogen on the mechanical properties of metals have long been observed. Although several theories exist describing the mechanisms by which hydrogen negatively influences the failure of materials, a consensus has yet to be reached regarding the exact mechanism or combination of mechanisms. Two mechanisms have gained support in explaining hydrogen’s degradative role in non-hydride forming metals: hydrogen-enhanced localized plasticity and hydrogen-enhanced decohesion. Yet, the interplay between these mechanisms and microstructure in metallic materials has not been explained. Accordingly, for this thesis, the three main objectives are: (i) to develop a numerical methodology to …
Optical Detection Of Acoustic Emission Signals, C Harvey Palmer, Robert E. Green Jr
Optical Detection Of Acoustic Emission Signals, C Harvey Palmer, Robert E. Green Jr
Robert A. Green
Piezoelectric transducers, long used in the generation and detection of ultrasonic waves, have more recently been the detector of choice for acoustic emission signals. Optical probing methods, however, have several important advantages for acoustic emission studies: (1) they have an inherent broad frequency response, free from mechanical resonances, (2) they do not interfere with the acoustic waves. (3) since the focused optical beam diameters are typically only a few hundredths of a millimeter, optical methods can probe very close to a crack or a twin, (4) they can probe internally in transparent media, and (5) they can be used over …
Molecular Dynamics Investigation Of The Arabinan-Cellulose Interface For Cellulose Nanocomposite Applications, Luke Thornley
Molecular Dynamics Investigation Of The Arabinan-Cellulose Interface For Cellulose Nanocomposite Applications, Luke Thornley
Materials Engineering
Atom level computer simulations of the arabinan and cellulose interface were performed to better understand the mechanisms that give arabinan-cellulose composites (ArCCs) their strength with the goal to improve man-made ArCCs. The molecular dynamics (MD) software LAMMPS was used in conjunction with the ReaxFF/c force field to model the bond between cellulose and arabinan. A cellulose nanocrystal with dimensions 51 x 32 x 8 Å was minimized with various weight percent of water, 0%, 3%, 5%, 8%, 10%, and 12%. After the system was equilibrated for at least 100,000 femtoseconds, an arabinan molecule composed of 8 arabinose rings was added …
Effect Of Time Delay Between Etching And Adhesive Bonding (“Outlife” Time) On Lap-Shear Strength Of Aluminum Alloys Using Environmentally-Friendly P2 Etch, Josh Barkhimer, Matthew Erich, Gokul Nair
Effect Of Time Delay Between Etching And Adhesive Bonding (“Outlife” Time) On Lap-Shear Strength Of Aluminum Alloys Using Environmentally-Friendly P2 Etch, Josh Barkhimer, Matthew Erich, Gokul Nair
Materials Engineering
Raytheon Company currently uses a Forest Products Laboratory (FPL) paste etchant for preparing aluminum surfaces for adhesive bonding, and FPL is a source of hazardous hexavalent chromium. The goal of this study was to evaluate a less-toxic P2 paste etchant as a possible replacement. Coupons of 2024-T3, 6061-T6, and 7075-T6 grades of aluminum alloy were solvent-degreased, abrasively cleaned, and etched at room temperature using P2 paste following a strict protocol adopted from Raytheon. Coupons were then left exposed to air for assigned time intervals (or “outlife” times) of 0, 1, 4, 8, 16, and 63 or 72 hours. The aluminum …
Non-Wetting Surface-Driven High-Aspect-Ratio Crystalline Grain Growth For Efficient Hybrid Perovskite Solar Cells, Cheng Bi, Qi Wang, Yongbo Yuan, Zhengguo Xiao, Jinsong Huang
Non-Wetting Surface-Driven High-Aspect-Ratio Crystalline Grain Growth For Efficient Hybrid Perovskite Solar Cells, Cheng Bi, Qi Wang, Yongbo Yuan, Zhengguo Xiao, Jinsong Huang
Department of Mechanical and Materials Engineering: Faculty Publications
Large-aspect-ratio grains are needed in polycrystalline thin-film solar cells for reduced charge recombination at grain boundaries; however, the grain size in organolead trihalide perovskite (OTP) films is generally limited by the film thickness. Here we report the growth of OTP grains with high average aspect ratio of 2.3–7.9 on a wide range of non-wetting hole transport layers (HTLs), which increase nucleus spacing by suppressing heterogeneous nucleation and facilitate grain boundary migration in grain growth by imposing less drag force. The reduced grain boundary area and improved crystallinity dramatically reduce the charge recombination in OTP thin films to the level in …
Analysis Of A Carbon Fiber Reinforced Polymer Impact Attenuator For A Formula Sae Vehicle Using Finite Element Analysis, John T. Rappolt
Analysis Of A Carbon Fiber Reinforced Polymer Impact Attenuator For A Formula Sae Vehicle Using Finite Element Analysis, John T. Rappolt
Master's Theses
The Hashin failure criteria and damage evolution model for laminated fiber reinforced polymers are explored. A series of tensile coupon finite element analyses are run to characterize the variables in the physical model as well as modeling techniques for using an explicit dynamic solver for a quasi-static problem. An attempt to validate the model on an axial tube crush is presented. It was found that fiber buckling was not occurring at the impactor-tube interface. Results and speculation as to why the failure initiation is incorrect are discussed. Lessons learned from the tube crush are applied successfully to the quasi-static Formula …
Predictive Modeling Of Oxygen Transmission Through Micro-Perforations For Packaging Applications, Ayman Abdellatief, Bruce A. Welt, Jason Butler, Eric Mclamore, Arthur Teixeira, Sanjay Shukla
Predictive Modeling Of Oxygen Transmission Through Micro-Perforations For Packaging Applications, Ayman Abdellatief, Bruce A. Welt, Jason Butler, Eric Mclamore, Arthur Teixeira, Sanjay Shukla
Journal of Applied Packaging Research
Methods for creating precise perforations in respiring produce packaging are being increasingly adopted. Knowledge of oxygen transfer through perforated packaging and oxygen distribution in packages is necessary for successful packaging design of fresh produce. An approach to modeling perforated packaging performance was developed using a cylindrical chamber with precision perforations using Fick’s second law. The model was simulated using two techniques including Finite Element Method (FEM) using commercially available software and Finite Volume Method (FVM) through programming. Perforations were approximated as a source term in the second method. Both simulation techniques showed trends similar to experimental data.
Development Of An Efficient Data Processing Procedure For The Prediction Of Cleavage Fracture In Reactor Pressure Vessel Steels Using The J-A2 Method, Phoebe E. Fogelman
Development Of An Efficient Data Processing Procedure For The Prediction Of Cleavage Fracture In Reactor Pressure Vessel Steels Using The J-A2 Method, Phoebe E. Fogelman
Chancellor’s Honors Program Projects
No abstract provided.
Energy Selective Neutron Imaging For The Characterization Of Polycrystalline Materials, Robin Woracek
Energy Selective Neutron Imaging For The Characterization Of Polycrystalline Materials, Robin Woracek
Doctoral Dissertations
This multipart dissertation focuses on the development and evaluation of advanced methods for material testing and characterization using neutron diffraction and imaging techniques. A major focus is on exploiting diffraction contrast in energy selective neutron imaging (often referred to as Bragg edge imaging) for strain and phase mapping of crystalline materials. The dissertation also evaluates the use of neutron diffraction to study the effect of multi-axial loading, in particular the role of applying directly shear strains from the application of torsion. A portable tension-torsion-tomography loading system has been developed for in-situ measurements and integrated at major user facilities around the …
Effects Of Temperature Change On Interfacial Delamination In Thermal Barrier Coatings, Hossein Ebrahimi, Soheil Nakhodchi
Effects Of Temperature Change On Interfacial Delamination In Thermal Barrier Coatings, Hossein Ebrahimi, Soheil Nakhodchi
Hossein Ebrahimi
No abstract provided.
Local Control Robotic Surgical Devices And Related Methods, Eric Markvicka, Tom Frederick, Jack Mondry, Joe Bartels, Shane Farritor
Local Control Robotic Surgical Devices And Related Methods, Eric Markvicka, Tom Frederick, Jack Mondry, Joe Bartels, Shane Farritor
Department of Mechanical and Materials Engineering: Faculty Publications
The various robotic medical devices include robotic devices that are disposed within a body cavity and positioned using a support component disposed through an orifice or opening in the body cavity. Additional embodiments relate to devices having arms coupled to a device body wherein the device has a minimal profile such that the device can be easily inserted through smaller incisions in comparison to other devices without such a small profile. Further embodiments relate to methods of operating the above devices.
Implications Of Heterogeneity In The Shock Wave Propagation Of Dynamically Shocked Materials, Jeffrey W. Lajeunesse
Implications Of Heterogeneity In The Shock Wave Propagation Of Dynamically Shocked Materials, Jeffrey W. Lajeunesse
Master's Theses (2009 -)
The field of shock physics as a whole has only recently begun to pay particular attention to modeling heterogeneous materials under shock loading. These materials are important because of their practicality in terms of creating stronger, more shock resistant materials. To understand why they absorb shock impact energy better than homogeneous materials means that the small-scale processes that occur during the shock loading of these heterogeneous materials needs to be understood. Recent computational experiments, called mesoscale simulations, have shown that explicitly incorporating small-scale heterogeneous features into hydrocode simulations allows the bulk shock response of the heterogeneous material to be observed …
Methods And Systems For Handling Or Delivering Materials For Natural Orifice Surgery, Carl Nelson, Jeff Midday, Dimitry Oleynikov, Alan Goyzueta
Methods And Systems For Handling Or Delivering Materials For Natural Orifice Surgery, Carl Nelson, Jeff Midday, Dimitry Oleynikov, Alan Goyzueta
Department of Mechanical and Materials Engineering: Faculty Publications
The embodiments disclosed herein relate to various medical systems, including systems that can be used in conjunction with medical devices used in endoscopic surgery. Certain embodiments include various material handling devices that can transport materials between the inside and the outside of an endoscopic surgery patient.
Highly-Selective Chemiresistive Sensing And Analysis Of Vapors Using Functionalized Nanotubes, Deon Hines
Highly-Selective Chemiresistive Sensing And Analysis Of Vapors Using Functionalized Nanotubes, Deon Hines
Dissertations, Theses, and Capstone Projects
Specifically, the project involves the development of a diversified array of nanostructured gas-sensors comprised of selectively, novel surface-functionalized carbon nanotubes (for analyte selectivity by virtue of functionality). Harnessing carbon nanotubes with various electron withdrawing and donating groups help in determining their affinity toward certain prognostic gaseous markers thus increasing specificity of such created sensors. We have devised synthetic routes that have led to the facile production of covalently polyfunctionalized nanotubes in high yield. Seven carbon nanotube analogues were systematically considered and then chemically synthesized, from pristine single-walled nanotubes (SWNT's), for use as the main component of sensory units that was …
Synthesis And Characterization Of A Novel Polyacetal & Design And Preparation Of Superhydrophobic Photocatalytic Surfaces, Yuanyuan Zhao
Synthesis And Characterization Of A Novel Polyacetal & Design And Preparation Of Superhydrophobic Photocatalytic Surfaces, Yuanyuan Zhao
Dissertations, Theses, and Capstone Projects
Polyacetal polymers are thermoplastic resins that play an important role in industry because of numerous industrial applications including automobile; household appliance; etc. The first part of this thesis (Chapter 2) is about the synthesis of a new acetal copolymer that exhibits superior thermal stability. The second part of this thesis (Chapter 3) is about the preparation and applications of TiO2-based polymer nanocomposite films, where the reactive oxygen species (ROS) are generated on the solid surface. Catalytic nanocomposite films are an active area of research because of their potential uses for environmental remediation and chemical synthesis. Furthermore, to …
Computational Study Of Microstructure-Propertymechanism Relations In Ferroic Composites, Fengde D. Ma
Computational Study Of Microstructure-Propertymechanism Relations In Ferroic Composites, Fengde D. Ma
Dissertations, Master's Theses and Master's Reports - Open
Ferroic materials, as notable members of smart materials, have been widely used in applications that perform sensing, actuation and control. The macroscopic property change of ferroic materials may become remarkably large during ferroic phase transition, leading to the fact that the macroscopic properties can be tuned by carefully applying a suitable external field (electric, magnetic, stress). To obtain an enhancement in physical and/or mechanical properties, different kinds of ferroic composites have been fabricated. The properties of a ferroic composite are determined not only by the properties and relative amounts of the constituent phases, but also by the microstructure of individual …
Exchange Mechanisms In Macroscopic Ordered Organic Magnetic Semiconductors, Naveen Rawat
Exchange Mechanisms In Macroscopic Ordered Organic Magnetic Semiconductors, Naveen Rawat
Graduate College Dissertations and Theses
Small molecule organic semiconductors such as phthalocyanines and their derivatives represent a very interesting alternative to inorganic semiconductor materials for the development of flexible electronic devices such as organic thin field effect transistors, organic Light Emitting Diodes and photo-voltaic cells. Phthalocyanine molecules can easily accommodate a variety of metal atoms as well in the central core of the molecule, resulting in wide range of magnetic properties. Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to sub-micron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. However, this can be overcome by …
Ruo2 Nanorods As An Electrocatalyst For Proton Exchange Membrane Water Electrolysis, Richard Smith
Ruo2 Nanorods As An Electrocatalyst For Proton Exchange Membrane Water Electrolysis, Richard Smith
Graduate College Dissertations and Theses
The desire for pure diatomic hydrogen gas, H2(g), has been on the rise since the concept of the hydrogen economy system was proposed back in 1970. The production of hydrogen has been extensively examined over 40 + years as the need to replace current fuel sources, hydrocarbons, has become more prevalent. Currently there are only two practical and renewable production methods of hydrogen; landfill gas and power to gas. This study focuses on the later method; using various renewable energy sources, such as photovoltaics, to provide off-peak energy to perform water electrolysis. Efficient electrolysis takes place in electrochemical cells which …
Microindentation Of Bi57in26sn17 Lead-Free Alloy, Ruiting Zhao
Microindentation Of Bi57in26sn17 Lead-Free Alloy, Ruiting Zhao
Theses and Dissertations--Chemical and Materials Engineering
There is great need to understand the mechanical properties of lead-free alloys—an alternative of lead-based alloys—to address the environmental problems associated with the use of lead-based materials in microelectronics. In this work, the microstructures of Bi57In26Sn17 lead-free alloy were examined using Optical Microscopy and Energy Dispersive X-ray Spectroscopy analysis. The micro-indentation technique was used to study the mechanical properties of Bi57In26Sn17 lead-free alloy. The experimental results of the hardness and contact modulus were presented and discussed. Local creep during the indentation was observed from the load-displacement curves. The Vickers hardness (HV) increases with the decrease of the indentation depth, suggesting …