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Full-Text Articles in Engineering Science and Materials

Development Of Multi-Axial Fatigue Retrofits For Lock Gate Components, Logan Verkamp May 2020

Development Of Multi-Axial Fatigue Retrofits For Lock Gate Components, Logan Verkamp

Theses and Dissertations

Lock gates are essential infrastructure components to the United State (US) supply chain. They create large cost savings and environmental benefits when compared with traditional methods of transport (freight and rail). Because of the large quantity of goods and dependence on these shipping chains, the US economy can be drastically affected by an unexpected gate closure. Unfortunately, many lock gates within the US have reached or exceeded their designed life. Due to the intensity of cyclic loads and the environment, fatigue cracks have become a prominent issue. Developed cracks near the pintle region (a joint which the gate rotates and ...


Modeling Nonlinear Heat Transfer For A Pin-On-Disc Sliding System, Brian A. Boardman Mar 2020

Modeling Nonlinear Heat Transfer For A Pin-On-Disc Sliding System, Brian A. Boardman

Theses and Dissertations

The objective of this research is to develop a numerical method to characterize heat transfer and wear rates for samples of Vascomax® 300, or Maraging 300, steel. A pin-on-disc experiment was conducted in which samples were exposed to a high-pressure, high-speed, sliding contact environment. This sliding contact generates frictional heating that influences the temperature distribution and wear characteristics of the test samples. A two-dimensional nonlinear heat transfer equation is discretized and solved via a second-order explicit finite difference scheme to predict the transient temperature distribution of the pin. This schematic is used to predict the removal of material from the ...


Focused Beam System Biaxial Material Characterization, Nicholas A. O'Gorman Mar 2020

Focused Beam System Biaxial Material Characterization, Nicholas A. O'Gorman

Theses and Dissertations

Electromagnetic material characterization is the process of determining the constitutive parameters (complex permittivity and permeability) of given a sample. Due to the large number of unknowns involved, multiple unique measurements are required for material property extraction. Many measurement methods, such as waveguides and striplines, possess a rigid internal structure that the sample being measured must adhere to. This rigidity limits these methods to samples that fit within the device and inhibits oblique sample orientations, limiting the number of independent measurements that can be obtained. A focus beam system, due to being an open system with greater freedom in sample size ...


Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam, Thaddeus M. Williams Mar 2020

Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam, Thaddeus M. Williams

Theses and Dissertations

Advanced aerospace applications such as aircraft turbine engine components, hypersonic flight vehicles, and spacecraft reentry thermal protection systems require structural materials that have superior long-term mechanical properties under high temperature, high pressure, and varying environmental factors, such as moisture. Because of their low density, high strength and fracture toughness at high temperatures SiC fiber-reinforced SiC matrix composites are being evaluated for aircraft engine hot-section components. In these applications the composites will be subjected to various types of mechanical loadings at elevated temperatures in oxidizing environments. Because their constituents are intrinsically oxidation-prone, the most significant problem hindering SiC/SiC composites is ...


Structural Dynamic And Inherent Damping Characterization Of Additively Manufactured Airfoil Components, Andrew W. Goldin Mar 2020

Structural Dynamic And Inherent Damping Characterization Of Additively Manufactured Airfoil Components, Andrew W. Goldin

Theses and Dissertations

The push for low cost and higher performance/efficient turbine engines have introduced a new demand for novel technologies to improve robustness to vibrations resulting in High Cycle Fatigue (HCF). There have been many proposed solutions to this, some passive and some active. With the advent of Additive Manufacturing (AM), new damping techniques can now be incorporated directly into the design and manufacture process to suppress the vibrations that create HCF. In this study, this novel unfused pocket damping technology is applied to a blade structure and the resulting damping effectiveness is quantified. The application of this technology to complex ...


Generation Of Warm Dense Plasma On Solar Panel Infrastructure In Exo-Atmospheric Conditions, Harrison C. Wenzel Jan 2020

Generation Of Warm Dense Plasma On Solar Panel Infrastructure In Exo-Atmospheric Conditions, Harrison C. Wenzel

Theses and Dissertations

The use of a weaponized thermo-nuclear device in exo-atmospheric conditions would be of great impact on the material integrity of orbiting satellite infrastructure. Particular damage would occur to the multi-layered, solar cell components of such satellites. The rapid absorption of X-ray radiation originating from a nuclear blast into these layers occurs over a picosecond time scale and leads to the generation of Warm Dense Plasma (WDP). While incredibly difficult and costly to replicate in a laboratory setting, a collection of computational techniques and software libraries may be utilized to simulate the intricate atomic and subatomic physics characteristics of such an ...


Optimizing Block-Stacking Operations With Relocation, Hueon Lee Dec 2019

Optimizing Block-Stacking Operations With Relocation, Hueon Lee

Theses and Dissertations

The focus of the dissertation is developing the optimization problem of finding the minimum-cost operational plan of block stacking with relocation as well as devising a solution procedure to solve practical-sized instances of the problem. Assuming changeable row depth instead of permanent row depth, this research is distinguished from conventional block stacking studies.

The first contribution of the dissertation is the development of the optimization problem under the assumption of deterministic demand. The problem is modeled using integer programming as a variation of the unsplittable multi-commodity flow problem. To find a good feasible solution of practical-sized instances in reasonable time ...


Effects Of Carbon-Based Ablation Products On Hypersonic Boundary Layer Stability, Olivia S. Elliott Sep 2019

Effects Of Carbon-Based Ablation Products On Hypersonic Boundary Layer Stability, Olivia S. Elliott

Theses and Dissertations

Hypersonic vehicles require an accurate prediction of the transition of the boundary layer for the design of the thermal protection system due to the high heating rates under turbulent flow. Many thermal protection systems are carbon-based and introduce new species, specifically CO2, into the boundary layer flow which are known to dampen the instabilities that lead to transition for hypersonic vehicles. A Computation Fluid Dynamics study was accomplished examining the concentration of CO2 required to impact boundary layer transition over both sharp and blunt cones. These results were used in conjunction with air-carbon ablation models models to determine if ...


On The Pulsed Laser Ablation Of Metals And Semiconductors, Todd A. Van Woerkom Aug 2019

On The Pulsed Laser Ablation Of Metals And Semiconductors, Todd A. Van Woerkom

Theses and Dissertations

This dissertation covers pulsed laser ablation of Al, Si, Ti, Ge, and InSb, with pulse durations from tens of picosecond to hundreds of microseconds, fluences from ones of J/cm2 to over 10,000 J/cm2, and in ambient air and vacuum. A set of non-dimensional scaling factors was created to interpret the data relative to the laser and material parameters, and it was found that pulse durations shorter than a critical timescale formed craters much larger than the thermal diffusion length, and longer pulse durations created holes much shallower than the thermal diffusion length. Low transverse order ...


Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller May 2019

Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller

Theses and Dissertations

Materials with features at the nanoscale can provide unique mechanical properties and increased functionality when included as part of a nanocomposite. This dissertation utilizes computational methods at multiple scales, including molecular dynamics (MD) and density functional theory (DFT), and the coupled atomistic and discrete dislocation multiscale method (CADD), to predict the mechanical properties of nanocomposites possessing nanomaterials that are either 1-D (carbyne chains), 2-D (graphene sheets), or 3-D (Al/amorphous-Si core-shell nanorod).

The MD method is used to model Ni-graphene nanocomposites. The strength of a Ni-graphene nanocomposite is found to improve by increasing the gap between the graphene sheet and ...


Influence Of Leading Edge Oscillatory Blowing On Time-Accurate Dynamic Store Separation, Ryan G. Saunders Mar 2019

Influence Of Leading Edge Oscillatory Blowing On Time-Accurate Dynamic Store Separation, Ryan G. Saunders

Theses and Dissertations

The primary objective of this research is to support the static and dynamic characterization and the time-accurate dynamic load data acquisition of store separation from a cavity with leading edge oscillatory blowing. Developing an understanding of, and potentially controlling, pitch bifurcation of a store release is a motivation for this research. The apparatus and data acquisition system was used in a two-part experiment to collect both static and dynamic testing data in the AFIT low speed wind tunnel in speeds of 60, 100, and 120 mph, from Reynolds numbers varying from 5.5x104 to 4.6x105, depending on ...


Ballistic Evaluation Of Carbon Nanotube Sheet Material In Multifunctional Applications, Casey M. Keilbarth Mar 2019

Ballistic Evaluation Of Carbon Nanotube Sheet Material In Multifunctional Applications, Casey M. Keilbarth

Theses and Dissertations

Significant development of carbon nanotubes has occurred since they were first studied in the 1990's. Attempts to capture the phenomenal molecular properties in practical applications are gaining ground as new methods of producing CNTs have been developed. This thesis sought to determine if the addition of commercially produced CNT sheets to thin carbon fiber panels improved the ballistic properties of the panel. The difference between 0 and 4 CNT sheets was studied. The hypothesis was that inte- grating CNT sheets into the laminate would increase the projectile energy absorbed by the panel and reduce the damage to the panel ...


Tracking Shock Movement On The Surface Of An Oscillating, Straked Semispan Delta Wing, Justin A. Pung Mar 2019

Tracking Shock Movement On The Surface Of An Oscillating, Straked Semispan Delta Wing, Justin A. Pung

Theses and Dissertations

A recent research effort, sponsored by the Air Force Office of Scientific Research, numerically investigated the unsteady aerodynamic flow field around an oscillating, straked, delta wing. The study was centered on determining the importance of the unsteady aerodynamic forces acting as a driver for a nonlinear motion known as limit cycle oscillations. The current effort focused on creating a computational model to compare to the results of previous tests and modeling efforts and discover new information regarding the onset of LCO. The computational model was constructed using the Cartesian overset capabilities of the CREATE-AV™ fixed wing fluid dynamics solver Kestrel ...


Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco Mar 2019

Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco

Theses and Dissertations

Computational aerothermodynamic analysis is presented for a spacecraft in low Earth orbit performing an atmospheric skip entry maneuver. Typically, atmospheric reentry is a terminal operation signaling mission end-of-life and, in some instances, executed for spacecraft disposal. A variation on reentry – skip entry – is an aeroassisted trans-atmospheric maneuver in which a spacecraft utilizes the effects of aerodynamic drag in order to reduce energy prior to a terminal entry, pinpoint a targeted entry, or change orbital elements such as inclination. Spacecraft performing a skip entry enable new modes of maneuver to enhance operations in nominal or possibly contested mission environments. The present ...


Analytical Models And Control Design Approaches For A 6 Dof Motion Test Apparatus, Kyra L. Schmidt Mar 2019

Analytical Models And Control Design Approaches For A 6 Dof Motion Test Apparatus, Kyra L. Schmidt

Theses and Dissertations

Wind tunnels play an indispensable role in the process of aircraft design, providing a test bed to produce valuable, accurate data that can be extrapolated to actual flight conditions. Historically, time-averaged data has made up the bulk of wind tunnel research, but modern flight design necessitates the use of dynamic wind tunnel testing to provide time-accurate data for high frequency motion. This research explores the use of a 6 degree of freedom (DOF) motion test apparatus (MTA) in the form of a robotic arm to allow models inside a subsonic wind tunnel to track prescribed trajectories to obtain time-accurate force ...


Manufacture Of Fused Deposition Modeling Joints Using Ultem 9085, Zane A. Willburn Mar 2019

Manufacture Of Fused Deposition Modeling Joints Using Ultem 9085, Zane A. Willburn

Theses and Dissertations

The manufacture of joints between a base structure and a structure manufactured via Fused Deposition Modeling (FDM) will be investigated. ULTEM 9085, a high temperature plastic with potential aerospace applications, will be the material used. The specific application this research is focused on is a robotic and mobile FDM printer capable of building structures onto other structures in space. A joint will be formed by fusing the base layer of the printed structure and the top of the base structure together. Tensile testing will be performed to determine the strength of the bond between parts. Tensile specimens will be manufactured ...


Comparative Study Of Power Semiconductor Devices In A Multilevel Cascaded H-Bridge Inverter, Kenneth Mordi Dec 2018

Comparative Study Of Power Semiconductor Devices In A Multilevel Cascaded H-Bridge Inverter, Kenneth Mordi

Theses and Dissertations

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET ...


Measuring Characteristic Shrinkage Variability Due To Metal Loading Effects In Low Temperature Co-Fired Ceramic Using Image Processing, John Ezekiel Zumbro Dec 2018

Measuring Characteristic Shrinkage Variability Due To Metal Loading Effects In Low Temperature Co-Fired Ceramic Using Image Processing, John Ezekiel Zumbro

Theses and Dissertations

Low temperature co-fired ceramic (LTCC) has many benefits when it comes to electronic packaging due to the low dielectric loss, reliability in extreme environments, and high breakdown voltage. Though the ceramic has a lot of benefits it is not widely used due to the high cost and complexities associated with manufacturing. One of these issues with manufacturing is compensating for the shrinkage of the ceramic, this is accomplished by using an expansion factor, creating the “green” or manufactured design. This expansion factor is approximated through knowledge of the ceramic factors such as the metal loading, layers of ceramic tape, firing ...


Aberration Corrected Analytical Electron Microscopy Studies Of Nanometallic Catalysts, Sultan Althahban Aug 2018

Aberration Corrected Analytical Electron Microscopy Studies Of Nanometallic Catalysts, Sultan Althahban

Theses and Dissertations

Catalysis by nanoscopic metal structures, ranging from nanoparticles to sub-nm clusters and even individual atoms, is amongst the most intensely studied topics in nanoscience. The catalytic performance of supported metal nanoparticles is governed by their crysallographic structure, shape, size, composition and interaction with the support. Aberration-corrected scanning transmission electron microscopy (AC-STEM), with its ultra-high spatial resolution for imaging and compositional analysis, is an ideal tool for characterizing such features in metallic nanocatalysts. In this thesis, five case studies are presented where AC-STEM has been invaluable in elucidating synthesis route - structure - performance relationships in some technologically important catalyst systems.


Grain Size Effects On Viscoelastic Relaxation Of Sub-Micron Thickness Fcc Metallic Films, Jeffrey Smyth Aug 2018

Grain Size Effects On Viscoelastic Relaxation Of Sub-Micron Thickness Fcc Metallic Films, Jeffrey Smyth

Theses and Dissertations

Sub-micron thickness metallic thin films are known to exhibit mechanical size effects, where the thin film mechanical behavior can differ significantly from that of a bulk version of the same material. One such mechanical behavior, and the focus of this work, is the unique thin film viscoelastic deformation response to sub-yield, low-strain stimuli in near-ambient temperature environments. In engineering components using bulk materials, strains within the elastic regime are generally considered instantaneous. It is only at higher operating temperatures that temporal deformation processes, such as creep, are considered in bulk component design. However, in Micro-Electro-Mechanical Systems (MEMS), specifically Radio Frequency ...


Creep Of Nextel 720/A Ceramic Matrix Composite With Laser Drilled Effusion Holes At 1200°C In Air And In Steam, Savannah N. Minor Mar 2018

Creep Of Nextel 720/A Ceramic Matrix Composite With Laser Drilled Effusion Holes At 1200°C In Air And In Steam, Savannah N. Minor

Theses and Dissertations

Creep behavior of an oxide-oxide ceramic matrix composite (CMC) containing an array of effusion holes was investigated at 1200⁰C in air and in steam. The composite (N720/A) consisted of a porous alumina matrix reinforced with alumina-mullite NextelTM 720 fibers. Test specimens had an array of 17 effusion holes with 0.5-mm diameter. The effusion holes were drilled through the specimen thickness normal to the specimen surface using a CO2 laser. Effect of the effusion holes on tensile properties was evaluated tension tests to failure at 1200°C in air. Creep of specimens with effusion holes at 1200°C was ...


Tensile Properties And Fatigue Behavior Of Geopolymer Matrix Composites With Carbon Fiber Reinforcement At Elevated Temperature, Steffan M.L. Wilcox Mar 2018

Tensile Properties And Fatigue Behavior Of Geopolymer Matrix Composites With Carbon Fiber Reinforcement At Elevated Temperature, Steffan M.L. Wilcox

Theses and Dissertations

The tensile stress-strain and tension-tension fatigue of geopolymer matrix composites reinforced with 0/90 carbon fibers was investigated at 23 and 300°C in laboratory air. Geopolymers are inorganic polymeric materials composed of alumina, silica, and alkali metal oxides. Because geopolymers are synthesized as a fluid mixture or particles and liquid, they can be cast into a desired shape, and cured at only slightly elevated temperatures. The relative ease of synthesis and low processing temperatures make geopolymers an attractive choice as a matrix material for composite materials. Geopolymers also offer resistance to heat and oxidizing environments. Currently, geopolymer matrix composites ...


Creep Of Hafnium Diboride -20 Vol% Silicon Carbide At 1500°C In Air, Glen E. Pry Mar 2018

Creep Of Hafnium Diboride -20 Vol% Silicon Carbide At 1500°C In Air, Glen E. Pry

Theses and Dissertations

Refractory metal borides, commonly referred to as Ultra High Temperature Ceramics (UHTCs), exhibit a number of unique properties, such as extremely high melting temperature and hardness, chemical stability, high electrical and thermal conductivity and corrosion resistance. It has been demonstrated that the addition of SiC improves the oxidation resistance of ZrB2- and HfB2-based UHTCs above 1200°C by modifying the composition of the oxide scale. Addition of SiC retards the oxidation rate of ZrB2 and HfB2 by forming a protective layer of borosilicate glass. Creep deformation is one of the critical criterion for structural application of ceramics at elevated temperatures ...


Influence Of Coolant Flow Rate Parameters In Scaling Gas Turbine Cooling Effectiveness On A Flat Plate, Jacob P. Fischer Mar 2018

Influence Of Coolant Flow Rate Parameters In Scaling Gas Turbine Cooling Effectiveness On A Flat Plate, Jacob P. Fischer

Theses and Dissertations

Effective film cooling relies on the performance of the selected cooling hole shape and placement of the holes on the surface of the blade. To test each holes effectiveness, large scale, low-temperature testing has been used to reduce cost and complexity. The resulting quantity from this testing is called the adiabatic effectiveness (n). The adiabatic effectiveness can then scaled up to engine operating conditions to predict how the selected film cooling hole will perform. This process is complicated by the nonlinear variation of gas properties between coolant and freestream conditions as well as between the experimental and engine conditions. In ...


Consuming Digital Debris In The Plasticene, Stephen R. Parks Jan 2018

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 ...


Feasibility Of Using Oxide Thickness Measurements For Predicting Crack Growth Rates In P91 Steel Components, Ralph Edward Huneycutt Iv May 2017

Feasibility Of Using Oxide Thickness Measurements For Predicting Crack Growth Rates In P91 Steel Components, Ralph Edward Huneycutt Iv

Theses and Dissertations

There are only few methods available for predicting the age of cracks that are found in high

temperature structural components during service; among the promising ones is the oxide

thickness measurement technique. Oxide thickness profiles are taken from crack surfaces of

components and used for predicting the rates of crack propagation. This technique is particularly

suitable for high temperature components fabricated from ferritic steels commonly used in power

plants that run on fossil fuels. To implement this technique, it is necessary to fully understand the

kinetics of high temperature oxidation in these steels. In this study, the oxidation characteristics

of ...


Stressed Oxidation Of Hafnium Diboride In Air At 1500°C, Thomas A. Bowen Mar 2017

Stressed Oxidation Of Hafnium Diboride In Air At 1500°C, Thomas A. Bowen

Theses and Dissertations

Hypersonic vehicles with narrow airfoils produce thin boundary layers and shock temperatures in excess of 2000 deg C, exceeding the operating limits of traditional aerospace materials. The use of ultra-high temperature ceramics (UHTCs) allows for operating temperatures far exceeding those of metallic alloys. One such UHTC is hafnium diboride (HfB2). Transition metal diborides generally experience significant oxidation degradation at elevated temperatures. The use of additives, such as silicon carbide (SiC) has been shown to reduce the oxidation of transition metal diborides. This research focused on the compressive creep of HfB2 with varying amounts of SiC in air at 1500 deg ...


Tunable Terahertz Metamaterials With Germanium Telluride Components, Christopher H. Kodama Mar 2016

Tunable Terahertz Metamaterials With Germanium Telluride Components, Christopher H. Kodama

Theses and Dissertations

Terahertz (THz) technology is an emerging field with many exciting applications. THz waves can be used to locate explosives and illicit drugs in security applications, or DNA and other molecule resonances in medical applications. THz frequencies represent the next level of modern, high-speed computing, but they also can be used for covert battlefield communications links. Metamaterials are an integral part of THz technology because they can be used to create exotic material properties—permittivities and permeabilities—in a part of the frequency spectrum that is otherwise rather empty and passive. This work aims to acquire a fuller understanding of THz ...


Finite Element Analysis (Fea) Study Of The Thermal Stress Concentrations In Planar-Type Sodium Sulfur (Nas) Secondary Batteries, Jeffrey P. Colker Dec 2015

Finite Element Analysis (Fea) Study Of The Thermal Stress Concentrations In Planar-Type Sodium Sulfur (Nas) Secondary Batteries, Jeffrey P. Colker

Theses and Dissertations

The importance of a reliable and safe way to store energy, and allow for on-demand usage, has led to much research in the field of secondary battery development. The thesis herein explores a technology that has shown promising results when implemented in large-scale energy grid applications. Though the technology has proven viable in both load-leveling on existing grids as well as serving to legitimize renewable energy sources, the development of such advanced battery systems is not without challenge. Sodium-sulfur (NaS) secondary cells have shown promising results when implemented in the aforementioned energy storage applications. One of the main drawbacks to ...


Field And Laboratory Study Of The Flàajökull Glacier, Iceland, William Russell Jacobson, Jr. Dec 2015

Field And Laboratory Study Of The Flàajökull Glacier, Iceland, William Russell Jacobson, Jr.

Theses and Dissertations

The increased surface melting of the outlet glaciers of the Vatnajökull Ice Cap has a profound affect on the dynamics of the ice-bed couple and landform genesis. Soft-bedded glaciers are largely inaccessible, which creates a problem. One challenge is to understand the complex interactions of the glacier bed and its resultant depositional and deformational landform systems. This study investigates an outlet glacier from the Vatnajökull Ice Cap, described herein as the Fláajökull glacier system. To circumvent some of these problems, three separate projects were conducted in this dissertation: (1) magnetic fabric study of effective pressure (difference between the ice-overburden pressure ...