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Articles 1 - 30 of 98
Full-Text Articles in Engineering
Development And Structural Origin Of Stretchable Semiconducting Polymers And Composites, Yunfei Wang
Development And Structural Origin Of Stretchable Semiconducting Polymers And Composites, Yunfei Wang
Dissertations
Stretchable semiconductors are pivotal in advancing wearable and implantable electronics, with those boasting both high stretchability and self-healing capabilities being especially significant for a myriad of wearable applications. In this dissertation, we developed an extremely soft, highly stretchable, and self-healing elastomer based on H-bonding crosslinked amide-functionalized polyisobutylene (PIB-amide). When blended with a high-performance conjugated diketopyrrolopyrrole (DPP-T) polymer, the composite exhibits unprecedented stretchability, exceptionally low elastic modulus, and an innate ability to self-heal at room temperature.
The morphology of conjugated polymer/elastomer semiconducting composites have significant impacts on electrical and mechanical properties Further investigations focused on manipulating the phase separation size in …
Laser Powder Directed Energy Deposition (Lp-Ded) Inconel 718: Laser Power And Heat Treatment Effect On Microstructure And Mechanical Properties, Dana Victoria Godinez
Laser Powder Directed Energy Deposition (Lp-Ded) Inconel 718: Laser Power And Heat Treatment Effect On Microstructure And Mechanical Properties, Dana Victoria Godinez
Open Access Theses & Dissertations
This study examines the microstructure and mechanical properties (tensile, hardness, and fatigue endurance) of laser powder-directed energy deposition (LP-DED) printed specimens with varying deposition parameters. Five samples with power inputs ranging from 350 to 2620W, all of similar thicknesses, were evaluated to enable a direct comparison. The varying specimens were heat treated, including stress relief, hot isostatic pressing, solution, and two-step aging. The resulting microstructures and their corresponding hardness values were compared at each heat treatment stage. The fully heat-treated specimens' tensile properties and fatigue life were also examined and compared. Key findings of this study indicate that complete heat …
A Study On High-Frequency Bending Fatigue, Microhardness, Tensile Strength, And Microstructure Of Parts Made Using Atomic Diffusion Additive Manufacturing (Adam) And Additive Friction Stir Deposition (Afsd), Hamed Ghadimi
LSU Doctoral Dissertations
This dissertation reports the findings of several studies on the mechanical and microstructural properties of parts made using atomic diffusion additive manufacturing (ADAM) and additive friction stir deposition (AFSD). The design of a small-sized bending-fatigue test specimen for an ultrasonic fatigue testing system is reported in Chapter 1. The design was optimized based on the finite element analysis and analytical solution. The stress–life (S–N) curve is obtained for Inconel alloy 718. Chapter 2 presents the findings of ultrasonic bending-fatigue and tensile tests carried out on the ADAM test specimens. The S-N curves were created in the very high-cycle fatigue regime. …
The Characterization And Nanomechanical Properties Of Microstructurally Complex Systems, Kerry Ann Baker
The Characterization And Nanomechanical Properties Of Microstructurally Complex Systems, Kerry Ann Baker
Theses and Dissertations--Chemical and Materials Engineering
Since the dawn of civilization, the use of metals has played an integral role in the evolution of human society. Over the years, and with the introduction of new engineering and science, we have learned how to combine metals to create new metallic systems. We have expanded our understanding of dealloying and chemical reactions, and, in doing so, we created nanoporous metals. Our use of metals has evolved from basic alloys such as bronze and steel to more complex alloys such as multi-principal element alloys. Nanoporous gold is an advanced metallic system that can be created through the dealloying process. …
Experimental Characterization And Quantification Of Deformation Behavior In A Porous Carbon Fiber Network, Robert N Quammen
Experimental Characterization And Quantification Of Deformation Behavior In A Porous Carbon Fiber Network, Robert N Quammen
Theses and Dissertations--Chemical and Materials Engineering
Due to their wide range of attractive functional properties (such as low thermal conductivity and low density) porous materials are utilized in a variety of applications. In order to characterize these properties and others, the intrinsically heterogeneous microstructures of these materials need to be taken into account. These microstructures result in interactions across multiple length scales spanning several orders of magnitude. This makes the creation of robust computational models and straight-forward predictions of mechanical properties difficult for porous materials. With this in mind, this dissertation aims to provide experimental mechanical and deformation information spanning the length scales of interest for …
Early-Age Strength And Failure Characteristics Of 3d Printable Polymer Concrete: Numerical Modelling And Experimental Testing, Mohammad Amin Dehghani Najvani
Early-Age Strength And Failure Characteristics Of 3d Printable Polymer Concrete: Numerical Modelling And Experimental Testing, Mohammad Amin Dehghani Najvani
Civil Engineering ETDs
The time-dependent rheological and early-age strength parameters of Polymer concrete (PC) were investigated. PC flow decreased, and the static yield stress and thixotropy increased as the specimen aged, while the dynamic yield stress remained unchanged. The study found that the Herschel-Bulkley model can accurately describe the PC’s rheological behavior over time. The change in cohesion strength and internal friction angle over time was observed using uniaxial unconfined compression and direct shear tests of fresh PC. A time-dependent MohrCoulomb failure criterion was established. Temperature analysis was used to determine the gel time and explain the evolution of the time-dependent early-age strength …
Spatially Resolved Elastic Modulus Of Magnesium Silicate Hydrate: A Cementitious Material, Arif Syed
Spatially Resolved Elastic Modulus Of Magnesium Silicate Hydrate: A Cementitious Material, Arif Syed
Material Science and Engineering Theses
Magnesium-based cements such as magnesium silicate hydrate (MSH) have drawn interest as an environmentally friendly substitute for ordinary Portland cement because of their potential for reduced carbon footprint. The precise determination of these materials' elastic moduli is important to better assess their mechanical performance. Atomic force microscopy (AFM) is an effective tool for precise and spatially resolved quantification of nanomechanical characteristics of materials, including thin films. In this study, elastic modulus maps of MSH grown on single crystal mica surfaces were obtained using amplitude modulation-frequency modulation AFM. The effects of the Mg:Si ratio and morphology on the elastic modulus of …
Synergistic Strategies In Sinter-Based Material Extrusion (Mex) 3d Printing Of Copper: Process Development, Product Design, Predictive Maps And Models., Kameswara Pavan Kumar Ajjarapu
Synergistic Strategies In Sinter-Based Material Extrusion (Mex) 3d Printing Of Copper: Process Development, Product Design, Predictive Maps And Models., Kameswara Pavan Kumar Ajjarapu
Electronic Theses and Dissertations
3D printing pure copper with high electrical conductivity and exceptional density has long been challenging. While laser-based additive manufacturing technologies suffered due to copper's highly reflective nature towards laser beams, parts printed via binder-assisted technologies failed to reach over 90% IACS (International Annealed Copper Standard), electrical conductivity. Although promising techniques such as binder jetting, filament, and pellet-based 3D printing that can print copper exist, they however still face difficulties in achieving both high sintered densities and electrical conductivity values. This is due to a lack of comprehensive understanding of property evolution from green to sintered states and the strategies that …
Analyzing The Effects Of Ultrafast Laser Processing On Mechanical Properties Of 3d-Printed Pla Parts, Darshan Pramodbhai Yadav
Analyzing The Effects Of Ultrafast Laser Processing On Mechanical Properties Of 3d-Printed Pla Parts, Darshan Pramodbhai Yadav
Theses and Dissertations
Recent advances in additive manufacturing technologies have already led to wide-scale adoption of 3D-printed parts in various industries. The expansion in choice of materials that can be processed, particularly using Fused Deposition Modeling (FDM), and the steady advancements in dimensional accuracy control have extended the range of applications far beyond rapid prototyping. However, additive manufacturing still has considerable limitations compared to traditional and subtractive manufacturing processes. This work addresses limitations associated with the as-deposited surface roughness of 3D-printed parts. The effects of roughness-induced stress concentrations were studied on ultimate tensile strength and fatigue life. The samples were manufactured using a …
Molecular Dynamics Study Of Characterization In Metal-Free Friction Materials, Yizhan Zhang
Molecular Dynamics Study Of Characterization In Metal-Free Friction Materials, Yizhan Zhang
Electronic Theses and Dissertations
Metallic friction materials currently used in industry may adversely impact the environment. Substitutions for metals in friction materials, on the other hand, can introduce operational safety issues and other unforeseeable issues such as thermal-mechanical instabilities and insufficient strength. In view of it, this dissertation focuses on developing different kinds of materials from simple structure to complex structure and evaluating the material properties with the assistance of molecular dynamics (MD) tools at the nano scale.
First, the concept of the contacted surfaces in friction at the atomic scale was introduced in order to get accurate understanding of the friction process compared …
Investigation Into The Load Transfer Mechanism Of Trees To Develop An Innovative Foundation Configuration Using 3d Finite Element Modeling, Kaleb Boland
All Theses
This study was inspired by a tree’s reliance on its root system that enables it to withstand a natural disaster, such as an extreme hydroclimatic event or hurricane. This curiosity has led to an investigation into what makes this possible, developing a new and innovative foundation configuration for infrastructure systems, and a new possible construction material and method. This study provides results on a material that does not have conventional testing procedures or standards: a tree root. The trees studied are common to the upstate of South Carolina, which are Pine, Sweetgum, and White Oak. According to the results, on …
Enhancing Microstructure, Composition Homogeneity, And Mechanical Properties In Laser Powder Bed Fused Metallic Alloys: Design, Fabrication, And Evaluation, Bahzad Farhang
Mechanical and Aerospace Engineering Dissertations
ABSTRACT: Over the past five decades, Nickel-based and Titanium-based alloys have become increasingly popular materials. As the manufacturing industry for these alloys has advanced, the demand for fabricating complex parts with enhanced mechanical properties at elevated temperatures has grown. Laser Powder Bed Fusion (LPBF), one of the most prevalent additive manufacturing techniques, has been employed successfully to produce these alloys. Nonetheless, there is still considerable effort being made to improve the microstructural, compositional, and mechanical properties of LPBF-processed components. In this study, we focused on adjusting the multi-scale microstructure and composition of LPBF-fabricated Nickel-based and Titanium-based alloys. The first objective …
Engineering 3d Architected Metamaterials For Enhanced Mechanical Properties And Functionalities., Huan Jiang
Engineering 3d Architected Metamaterials For Enhanced Mechanical Properties And Functionalities., Huan Jiang
Electronic Theses and Dissertations
Compared with conventional materials, architected metamaterials have shown unprecedented mechanical properties and functionalities applications. Featured with controlled introduction of porosity and different composition, architected metamaterials have demonstrated unprecedent properties not found in natural materials. Such design strategies enable researchers to tailor materials and structures with multifunctionalies and satisfy conflicting design requirements, such as high stiffness and toughness; high strength with vibration mitigation properties, etc. Furthermore, with the booming advancement of 3D printing technologies, architected materials with precisely defined complex topologies can be fabricated effortlessly, which in turn promotes the research significantly. The research objectives of this dissertation are to achieve …
Effect Of Boron In Cast Iron, Suyash Durendra Pawaskar
Effect Of Boron In Cast Iron, Suyash Durendra Pawaskar
Masters Theses
"Boron, mostly considered a residual element, has started to cause issues in the cast iron foundries by causing a decrease in the strength of pearlitic gray and ductile iron castings. Because of the increase in the use of boron-added steel scrap from automotive steel and a lack of agreement on the critical levels of boron in cast iron, foundries are facing difficulties in controlling the microstructure of gray iron castings when boron is present. The current investigation was designed to analyze the effects of boron in cast irons and predict a mechanism to understand its effects with a vision of …
Insect Antennae As Bioinspirational Superstrong Fiber-Based Microfluidics, Griffin J. Donley
Insect Antennae As Bioinspirational Superstrong Fiber-Based Microfluidics, Griffin J. Donley
All Theses
Nature is frequently turned to for inspiration for the creation of new materials. Insect antennae are hollow, blood-filled fibers with complex shape, and are cantilevered at the head. The antenna is muscle-free, but the insect can controllably flex, twist, and maneuver it laterally. To explain this behavior, a comparative study of structural and tensile properties of the antennae of Periplaneta americana (American cockroach), Manduca sexta (Carolina hawkmoth), and Vanessa cardui (painted lady butterfly) was performed. These antennae demonstrate a range of distinguishable tensile properties, responding either as brittle fibers (Manduca sexta) or strain-adaptive fibers that stiffen when stretched (Vanessa cardui …
Characterization Of Material For Composite Automotive Components, Thomas J. Chang
Characterization Of Material For Composite Automotive Components, Thomas J. Chang
Electronic Thesis and Dissertation Repository
A composite had been widely used for the lightweighting purpose amid increasing environmental concerns. Among composite manufacturing processes, compression molding is widely used for automotive parts. During compression molding, the mold geometry and molding process conditions significantly influence the fiber configuration and the mechanical performance.
Hence, this thesis aims to characterize the microstructural and mechanical properties of the complex shaped composite automotive components: outer seatback and inner seatback. Both parts were compression molded using commercial glass mat thermoplastic sheet with long glass fibers (30mm-50mm) embedded in the polyamide resin. The microstructural characterization results showed that the microstructural properties are influenced …
An Investigation Into Energy-Material Properties Interaction In Additive Manufacturing Of Polymers., Pu Han
An Investigation Into Energy-Material Properties Interaction In Additive Manufacturing Of Polymers., Pu Han
Electronic Theses and Dissertations
Additive manufacturing (AM), known as three-dimensional (3D) printing, is a fabrication process to build 3D objects layer by layer based on computer aided design (CAD) model or digital 3D model. Fused filament fabrication (FFF) has become a preferred method for additive manufacturing due to its cost-effectiveness and flexibility. However, the parts built using FFF process suffer from lower mechanical strength compared to that fabricated using traditional method and rough surface finish. With this motivation, this dissertation aims to develop and implement a novel in-process laser assisted technique on FFF to heal the microstructure of FFF built objects by enhancing reptation …
Searching Extreme Mechanical Properties Using Active Machine Learning And Density Functional Theory, Joshua Ojih
Searching Extreme Mechanical Properties Using Active Machine Learning And Density Functional Theory, Joshua Ojih
Theses and Dissertations
Materials with extreme mechanical properties leads to future technological advancements. However, discovery of these materials is non-trivial. The use of machine learning (ML) techniques and density functional theory (DFT) calculation for structure properties prediction has helped to the discovery of novel materials over the past decade. ML techniques are highly efficient, but less accurate and density functional theory (DFT) calculation is highly accurate, but less efficient. We proposed a technique to combine ML methods and DFT calculations in discovering new materials with desired properties. This combination improves the search for materials because it combines the efficiency of ML and the …
Strengthening Of 7175 Aluminum Alloy Through Multi-Step Aging Process, Colin E. Masterson, Ryland W. Jolliffe
Strengthening Of 7175 Aluminum Alloy Through Multi-Step Aging Process, Colin E. Masterson, Ryland W. Jolliffe
Materials Engineering
7175 is a heat-treatable aluminum alloy commonly used in aerospace forgings. This alloy is aged with a multi-step heat treatment. This treatment must balance strength with stress corrosion cracking resistance through a degree of overaging. The team was tasked by Weber Metals to increase the strength of this treatment without sacrificing stress corrosion cracking resistance. Both two-step and retrogression and reaging treatments were tested in experiments to find a heat treatment that could increase the yield and tensile strength by 1-2 ksi while maintaining a minimum electrochemical conductivity equivalence of 38% relative to copper. Two-step aging is the more conventional …
Development And Characterization Of Sustainable Novel Aluminum Metal Matrix Composites, John Victor Christy
Development And Characterization Of Sustainable Novel Aluminum Metal Matrix Composites, John Victor Christy
Dissertations
Low crude oil prices have impacted the economy of the Gulf Cooperation Council (GCC) member countries especially the United Arab Emirates (UAE). Hence it is vital to accelerate the diversification of the economy. Among the many potential diversification avenues, manufacturing is a promising area that could add to the GDP. This work brings out a sustainable and cost-effective method for manufacturing AMCs and expanding their applications.
This work deals with the processing and characterization of recycled AMCs manufactured using a novel approach. With the emphasis on sustainable manufacturing, this work aims to use Scrap Aluminum Alloy Wheels (SAAW) of cars …
Investigation Of The Microstructural And Mechanical Properties Of Selectively Laser Melted In718 Overhangs Fabricated Without Support Structures, Manjunath Hanumantha
Investigation Of The Microstructural And Mechanical Properties Of Selectively Laser Melted In718 Overhangs Fabricated Without Support Structures, Manjunath Hanumantha
Mechanical and Aerospace Engineering Theses
Additive manufacturing is a new manufacturing technology that allows for extreme design freedom as well as the simultaneous production of many parts with high complexities. IN718 is a high-strength, corrosion-resistant super alloy of nickel and chromium. It is ideal for high-end applications such as rocket nozzles and turbines because it can handle exceptionally high pressure and heat. Because of its high stiffness qualities, conventional manufacturing of complex IN718 geometries is challenging. Various fabrication techniques have been developed, and this study focuses on selective laser melting (SLM) because of its potential to produce near-perfect parts at a low cost when working …
A Computational Study Of Cocrfeniti High Entropy Alloys: Phase Diagrams, Thermodynamics, And Mechanical Properties From Calphad And First Principles, Geraldine Anis
Theses and Dissertations
High entropy alloys (HEAs) are multi-component alloys, which are often defined as those consisting of at least 5 principal elements with concentrations ranging between 5 and 35 atomic weight percent (at.%). Since their introduction by Yeh et al. and Cantor et al. in 2004, HEAs have been found to possess many important properties and have become prime candidates for several high-performance applications such as high-temperature and biomedical applications. Despite their multi-principal element nature, many HEAs favor the formation of solid solution phases as opposed to the intermetallic phases expected for such systems. This was originally only attributed to their high …
Experimental Characterization And Crystal Plasticity Modeling Of Mechanical Properties And Microstructure Evolution Of Additively Manufactured Inconel 718 Superalloy, Saeede Ghorbanpour
Experimental Characterization And Crystal Plasticity Modeling Of Mechanical Properties And Microstructure Evolution Of Additively Manufactured Inconel 718 Superalloy, Saeede Ghorbanpour
Doctoral Dissertations
In this thesis, the mechanical behavior of the additively manufactured (AM) IN718 nickel-based superalloy and their correlations with the evolution of microstructure are studied comprehensively. The effects of manufacturing parameters, build orientations, and post processing procedures, i.e. standard heat treatment and hot isostatic pressing (HIP), on various mechanical properties including monotonic compression and tension strength, low cyclic fatigue performance, high cyclic fatigue behaviour, and fatigue crack growth behavior are investigated. Due to the high temperature applications of the IN718 alloy, elevated temperature properties are examined as well. Electron Backscattered Diffraction (EBSD) technique is employed to measure the initial and deformed …
Determination Of Hydrogel Degradation By Passive Mechanical Testing, Avery Rosh-Gorsky
Determination Of Hydrogel Degradation By Passive Mechanical Testing, Avery Rosh-Gorsky
Honors Theses
This paper details a new technique to measure the mechanical properties of ETTMP PEGDA hydrogels using Hertz Contact Theory and simultaneously analyze both the model drug release and gel erosion in situ. This method involves curing a drug loaded hydrogel in a standard cuvette and placing a glass bead and phosphate buffer solution (PBS). Over time, the cross-linked network of the hydrogel breaks down, and, as a result, the ball sinks into the hydrogel. This method provides a macroscopic and inexpensive way to continuously and passively measure properties of the hydrogel as the hydrogel degrades. By plotting both the …
Exploring Rapid Solidification And Equal Channel Angular Pressing In The Fabrication Of Mg-Based Alloys For Medical Applications, Emily Tom
Dissertations, Master's Theses and Master's Reports
The development of magnesium bioresorbable implants has become increasingly popular due to the increased need for temporary implants and magnesium’s excellent biocompatibility and suitable elastic modulus. Even though magnesium is an excellent candidate, when alloyed with other metals magnesium’s corrosion rate becomes too rapid for bioresorbable medical applications. The investigation into novel processing techniques to control the formation of precipitates to improve mechanical strength and ductility as well as corrosion rates has become of interest. This work investigates the combination of two nonequilibrium processing techniques, rapid solidification (RS) and equal channel angular pressing (ECAP), and the effects it has on …
Fiber Prestressing In Glass Fiber Reinforced Polymer (Gfrp) Composites, Mahmoud Mohamed
Fiber Prestressing In Glass Fiber Reinforced Polymer (Gfrp) Composites, Mahmoud Mohamed
All ETDs from UAB
Fiber Reinforced Polymer (FRP) composite have found increasing use in several vital industries and applications, such as transportation, construction, sporting goods, and aircraft. The quality and mechanical properties of FRP composites are significantly influenced by many factors including the manufacturing technique. Introducing the technique of fiber prestressing during the manufacturing process of FRP composites can effectively improve their performance without a considerable additional cost. This study contributes to further investigation and understanding about utilizing the elastic method of fiber prestressing to produce Glass Fiber Reinforced Polymer (GFRP) composites, in the following ways:First, a novel and effective method to manufacture unidirectional …
The Effect Of Compaction Temperature And Pressure On Mechanical Properties Of 3d Printed Short Glass Fiber Composites, Pushpashree Jain Ajith Kumar Jain
The Effect Of Compaction Temperature And Pressure On Mechanical Properties Of 3d Printed Short Glass Fiber Composites, Pushpashree Jain Ajith Kumar Jain
Mechanical & Aerospace Engineering Theses & Dissertations
Among many thermoplastics that are used in engineering, polyamide 6 (nylon 6) is an extremely versatile engineering thermoplastic. Nylon filled with glass fibers has higher mechanical strength and high wear resistance than general purpose nylon. 3D printed composites, based on fused filament modeling, typically suffer from poor bead-to-bead bonding and relatively high void content, limiting their mechanical properties
This thesis explores the effect of compaction pressure and temperature on improving the mechanical properties of 3D printed composites. Engineering moduli in the printing and transverse to printing direction, as well as ultimate strength were measured using the tensile testing with Digital …
Molecular Level Mechanical Properties Of Ultra High Temperature Ceramics And Their Nanocomposites, Md Riaz Kayser
Molecular Level Mechanical Properties Of Ultra High Temperature Ceramics And Their Nanocomposites, Md Riaz Kayser
Mechanical and Aerospace Engineering Dissertations
Ultra High-Temperature Ceramics (UHTC) have been of great interest in the spacecraft, aerospace, and aeronautic industry due to their high melting point and their potential application as a protective material for the stagnation areas of leading edges. In this work, the effect of nanoparticle reinforcement for achieving tailored mechanical properties of UHTC’s has been studied. Two different material systems have been considered, namely the ZrB2-based and the HfO2-based nanocomposites. In the first study, the grain boundary driven mechanical behavior of polycrystalline ZrB2 and ZrC-ZrB2 nanocomposites using large-scale molecular dynamics simulations have been performed. The atomistic models of polycrystalline ZrB2 and …
Mechanical Properties And Cyclic Behavior Of High Strength Steel After Fire Exposure, Fang Wang
Mechanical Properties And Cyclic Behavior Of High Strength Steel After Fire Exposure, Fang Wang
Dissertations - ALL
Behavior of High Strength Steels (HSS) after exposure to high temperature has become an important research topic in recent years. A number of studies have demonstrated that different grades of HSS can exhibit noticeable differences in their mechanical properties under and after fire exposure, and different cooling methods may have an effect on the post-fire mechanical properties of HSS. In this research, the post-fire mechanical properties of Q690 steel and the post-fire residual stress distributions of Q690 welded I-sections heated to various temperatures using different heating rates and cooled using two cooling methods are determined experimentally and simple empirical equations …
Materials-Processing Relationships For Metal Fused Filament Fabrication Of Ti-6al-4v Alloy., Paramjot Singh
Materials-Processing Relationships For Metal Fused Filament Fabrication Of Ti-6al-4v Alloy., Paramjot Singh
Electronic Theses and Dissertations
Additive manufacturing (AM) is at the mainstream to cater the needs for rapid tooling and small-scale part production. The metal AM of complex geometries is widely accepted and promoted in the industry. While several metal AM technologies exist and are matured to a level where expectation in terms of design and properties are possible to realize. But the metal AM suffers from the heavy expense to acquire equipment, isotropic property challenges, and potential hazards to work with loose reactive metal powder. With this motivation, the dissertation aims to develop the fundamental aspects to print metal parts with bound Ti-6Al-4V powder …