Digital Commons Network^™

Rans-Dns Simulations For Uncertainty Quantification In Dns Data Of Turbulent Mixing Layer, Mohamed Abuhegazy

Mechanical Engineering ETDs

Mixing layer flow is one of the canonical free shear flows in fluid dynamics. Such a flow is formed when two fluid streams move along one another with different velocities. Investigation of this flow development has been an active topic of research for many decades not only due to a wide range of environmental and technological applications where this flow may be observed, but also because of large discrepancies in the results obtained experimentally and numerically regardless this flow simple geometry. In this dissertation, the quality and uncertainty of extracted turbulent statistics of mixing layer flow are analyzed by applying …

Modeling Of Asphalt Concrete For Cross-Anisotropic Visco-Elasticity And Heterogeneity, Zafrul Hakim Khan

Civil Engineering ETDs

Asphalt Concrete (AC) is a cross-anisotropic viscoelastic material. This study has developed a methodology to backcalculate the cross-anisotropic properties of the AC layer from the Falling Weight Deflectometer (FWD) sensor and pavement response data from embedded sensors inside a pavement section. This study has also developed a two-way coupled Multiscale Finite Element Model (MsFEM) with Phase Field Fracture (PFF) to study the microstructural heterogeneity and damage of the AC layer based on the actual field loadings. A Finite Difference Time Domain (FDTD) and Machine learning-based backcalculation algorithm were developed to determine the layer thickness and dielectric constant from air-coupled Ground …

Aerodynamic Dimpling For The Nose Cone Of A High-Power Competition Rocket, Graham Geoffrey Monroe

Mechanical Engineering ETDs

This thesis investigates nose cone dimpling for the reduction of the aerodynamic drag of a Level 3 High-Power amateur rocket. Two rocket launches were conducted. The first used a COTS nose cone with a smooth surface. A dimple distribution was created according to dimensions calculated by Sandia National Laboratories’ proprietary Right- Size Dimple Evaluator. A dimpled nose cone, designed with geometry matching the COTS component, was 3D printed. Axial acceleration and barometric pressure data, recorded by an onboard flight computer, were used to calculate and plot the drag coefficient as a function of the Reynolds number for the smooth and …

Main Effects Screening Study Of Fe/Kclo4 Thermal Battery Heat Pellet Resistive Activation, Bryan T. Steiner

Mechanical Engineering ETDs

Thermal battery iron-potassium perchlorate (Fe/KClO₄) heat pellets are often ignited by explosive igniters or heat paper. An alternative direct electrical ignition method via resistive heating is explored, which could improve thermal battery manufacturability and design flexibility. A main effects screening experiment was performed with the goal of confirming prior observed trends under more realistic test conditions and ranking the importance of design factors, to optimize future experiments and develop knowledge of the performance space. Relevant literature is examined to advance a theoretical understanding of resistive activation. Ignition sensitivity (go/no-go and time to ignition) and ignition energy are primary …

Screw Dislocations In A Holed Wedge, Gregory T. Whiteside

Mechanical Engineering ETDs

A numerical code has been designed and implemented to find the stress at any material point in a holed-wedge material due to any number of crystal or real screw dislocations in the wedge. The code implements the image dislocation method together with the collocation point method to find stresses at any material point. We demonstrate that the combined analytical-numerical method (analytical with the image dislocations and numerical with the collocation-point method) is valid in that it produces stress fields giving rise to zero traction on free surfaces as well at an arbitrary number of collocation points on void surfaces. Additionally, …

Control Of Fully-Actuated Aerial Manipulators And Omni-Directional Multirotors, Riley M. Mccarthy

Mechanical Engineering ETDs

This thesis details the system modeling, design, control, simulation, construction, and
testing of both a fully-actuated and omni-directional multirotor aerial system created
for the primary purpose of performing active tasks with their environment. This work
verifies the capabilities of both systems through empirical testing, and demonstrates
how through the use of new control methods and physical designs multirotors can
expand their purpose from passive inspection based tasks to active contact based
tasks. These systems take advantage of newly implemented control allocation features present in the PX4 flight control software, version 1.14. The use of which makes designing controllers for such …

Design, Fabrication And Characterization Of Zero Power Sensor/Harvester For Smart Grid Applications, Zeynel Guler

Mechanical Engineering ETDs

This study presents a flexible sensor/harvester device to be used in both electromagnetic sensing and energy harvesting applications for smart grids. When a current passes through a wire, the sensor detects the magnetic field created by that current. The sensor magnet interacts with the wire magnetic field resulting in a transfer of energy through the piezoelectric cantilever. Piezoelectric, conductive, magnetic, and magnetostrictive composite thin films were prepared to fabricate this device.

Initially, the magnet of the cantilever was optimized considering its shape, thickness, length, taper angle etc. via both simulations and experiments. Peak to peak voltage versus cantilever position graph …

Extremum Seeking Control Algorithms For Extremely High Frequency Antenna System Pointing, Scott Shore

Mechanical Engineering ETDs

The research examines the application of extremum seeking control (ESC) algorithms to ground station antenna pointing for extremely high frequency (EHF) communication systems. ESC algorithms search for local maxima or minima by locating where an objective function gradient goes to zero. With wireless communication expanding into higher frequencies, the ground station pointing requirement is increasing. ESC presents a method which utilizes available equipment and information to perform ground station pointing. Additionally, ESC algorithms do not rely on assumptions or approximations needed for other techniques. The dissertation demonstrates ESC algorithm feasibility for the ground station pointing problem, benchmarks the ESC algorithms …

Effect Of Fiber Proximity On The Pullout Response: A Finite Element Study, Tyler Mitchell

Mechanical Engineering ETDs

With the advancement of computational capabilities, there is growing interest in
developing intricate models for composite materials. This has been historically chal-
lenging due to the multifaceted interactions and failure mechanisms of these materi-
als. Multiscale modeling holds promise for predicting the intricate dynamics of such
materials. A foundational understanding of their microscale behaviors is critical, par-
ticularly the interfacial interactions between the fiber and matrix. This study delves
into the influence of fiber volume fraction (FVF) on fiber pull-out tests, focusing
on the impact of neighboring fibers across different geometries and the underlying
cohesive properties.

Miniature, Submersible Electromagnetic Pumps Of Molten Lead And Sodium For Gen-Iv Nuclear Reactors Development, Ragai M. Altamimi

Nuclear Engineering ETDs

Heavy metals and alkali Liquid Metals are suitable coolants for Generation IV terrestrial nuclear reactors for operating at elevated temperatures for achieving plant thermal efficiency more than 40% and the thermochemical generation of hydrogen fuel. In addition, the low vapor pressure of these liquids eliminates the need for a pressure vessel and instead operates slightly below ambient pressure. A primary issue with the uses of these coolants is their compatibility with nuclear fuel, cladding and core structure materials at elevated temperatures more than 500oC. Therefore, in pile and out-of-pile test loops have been constructed or being considered for quantifying the …

Analysis Of Ternary Chloride Salt Corrosion In High Nickel Alloys, Dimitri Madden, Gowtham Mohan

Mechanical Engineering ETDs

The United States Department of Energy seeks to improve the efficiency of concentrating solar power technologies by employing thermal energy storage with operating temperatures above 700°C. To meet these goals, the National Solar Thermal Test Facility at Sandia National Laboratories has considered the use of a ternary molten chloride salt for sensible heat storage systems. While favored for low cost, good heat transfer properties, and stability at high temperature, ternary chloride salt also exhibits high corrosive attack. Components of a chloride salt storage system would include piping, valves, tanks, pumps, receivers, and heat exchangers, which would be exposed to high …

Design And Development Of Magnetoelastic Resonators For Pv Ground Fault Detection, Skyler H. Oglesby

Mechanical Engineering ETDs

This project will design, fabricate, and test a magnetoelastic nickel-iron-cobalt alloy resonator for ground fault detection applications, specifically in photovoltaic systems. The electrodeposition technique will be used to fabricate the proposed resonator as it enables a precise manufacturing process. It allows for better control and optimization of material properties (magnetic, mechanical, and electrical) while facilitating the necessary dimensions. A great deal of study and experimentation will go into the electrolyte development when dealing with challenges like intrinsic stress and surface defects within the film. Hull cell analysis will be done to study the composition of the material in different electrochemical …

Mechanical Characterization Of Additively Manufactured Alloys Compared To Their Wrought Counterparts, Laith A. Alqawasmi

Mechanical Engineering ETDs

Additive manufacturing is a method of manufacturing based on building parts layer by layer, allowing for more control over shape of the product, therefore reducing machining costs, reducing material waste, faster production times and the ability to build complex engineering design that other manufacturing technologies won’t be able to produce. This research is on the tensile and indentation testing (following ASME standards) of 3D printed Ti-6Al-4V and Inconel 718 built by powder-based direct energy deposition technology. Ti-6Al-4V is an attractive material for the aerospace and aviation industry, and Inconel 718, a nickel-chromium based superalloy, is an attractive material for usage …

Development Of Models For The Velocity-Pressure Gradient Correlations In Incompressible Wall-Bounded Planar Turbulent Flows Using Multiple Linear Regression, Juampablo E. Heras Rivera

Mechanical Engineering ETDs

In this thesis, the multiple linear regression method is applied to clarify terms and their coefficients in data-driven models for velocity/pressure-gradient (VPG) correlations in the Reynolds stress transport equations. Additionally, a method for developing universal linear models for the VPG correlations with unchanging coefficients when complex conditions arise in a flow is introduced. The generated models were assessed using residual analysis to ensure an appropriate level of accuracy. Data from direct numerical simulation in an incompressible fully-developed turbulent channel flow at Re_tau = 392 with an adverse pressure gradient is used in the study as the data source.

Characterization Of Materials Properties In Additively Manufactured Aisi-420 Martensitic Steel Deposited By Laser Engineered Net Shaping, Md Mehadi Hassan

Nanoscience and Microsystems ETDs

Metal additive manufacturing (AM) is a disruptive technology enabling the fabrication of complex and near-net-shaped parts by adding material layer-wise. It offers reduced lead production time. AM processes are finding applications in many industrial sectors such as aerospace, automotive, biomedical, and mold tooling. Despite the tremendous advantages of AM, some challenges still prevent this technology's adoption in high-standard applications. Anisotropy and inhomogeneity in the mechanical properties of the as-built parts and the existence of pores and lack-of-fusion defects are considered the main issues in directed energy deposition (L-DED) parts. Laser-engineered net shaping LENS® offers excellent possibilities to fabricate metal tools …

Particle Image Velocimetry Methodology For Calculating The Advective Losses At The Solar Tower For The Gen 3 Concentrated Solar Power System, Guillermo Anaya

Mechanical Engineering ETDs

The Falling Particle Receiver (FPR) built by Sandia National Laboratory (SNL) at the National Solar Thermal Testing Facilities (NSTTF) is one of the latest concentrated energy harvesting systems for Concentrated Solar Power (CSP). The FPR system at the NSTTF uses solid particles as both the heat transfer fluid and storage media. This FPR operates by having a gravity-driven particles curtain being irradiated through an open cavity by CSP, provided by a heliostat field. However, during operation plumes of particles being expelled out of the receiver cavity can be observed, resulting in heat losses as well as particle inventory losses. The …

Evolution Of Shock-Driven Multi-Phase Instability, Joshua Chavez

Mechanical Engineering ETDs

ABSTRACT

In many models and experiments using shock tubes and shock tube instabilities, measurements of velocity and position of the flow features are frequently taken in a single horizontal direction (or in one plane), however, the three-dimensional flow structure is important and cannot be fully resolved by such measurements. By placing a mirror at 45 degrees atop a test section of a shock tube, it becomes possible to visualize the flow from two directions simultaneously. The mirror is used to see if viable data can be gathered from the second view in conjunction with the main view. With high-speed video …

Material Characterization And Comparison Of Sol-Gel Deposited And Rf Magnetron Deposited Lead Zirconate Titanate Thin Films, Katherine Lynne Miles

Mechanical Engineering ETDs

Lead zirconate titanate (PZT) has been a material of interest for sensor, actuator, and transducer applications in microelectromechanical systems (MEMS). This is due to their favorable piezoelectric, pyroelectric and ferroelectric properties. While various methods are available to deposit PZT thin films, radio frequency (RF) magnetron sputtering was selected to provide high quality PZT films with the added capability of batch processing. These sputter deposited PZT films were characterized to determine their internal film stress, Young’s modulus, composition, and structure. After characterization, the sputtered PZT samples were poled using corona poling and direct poling methods. As a means of comparison, commercially …

Simulation Of Supercritical Multiphase Flows Using Machine Learning, Nelson P. Longmire

Mechanical Engineering ETDs

In many technologies, such as rocket engines and modern power plants, the pressures of the fluids in these systems have increased to increase efficiency. As a result, the fluids are under pressures higher than the critical pressure meaning the fluids are supercritical. Supercritical fluids are unique as a liquid/gas phase equilibrium no longer exists, and a process called pseudo boiling occurs where the fluid properties have steep gradients, which lead to interesting fluid mechanics and heat transfer characteristics. Our understanding of supercritical fluids has had exciting advances over the years. However, there are still phenomena that are still not well …

Run-To-Run Control Via Constrained Optimization Of A Mechanical Serial-Sectioning System, Damian L. Gallegos-Patterson

Mechanical Engineering ETDs

This thesis develops a methodology for run-to-run (R2R) control of a mechanical serial sectioning (mss) system for microstructural investigations. mss is a destructive material characterization process which repeatedly removes a thin layer of material and images the exposed surface. The images are then used to gain insight into the internal structure and arrangement of a material and are often used to generate a 3-dimensional (3D) reconstruction of the sample. Currently, an experienced human operator selects the parameters for mss to achieve the desired per slice removal rate. The proposed R2R control methodology automates this process while improving the precision and …

Expanded-Range Venturi Flow Meter: Development And Testing Of A 3d-Printed Flow Meter And Solid-State Valve Concept, Joseph M. Pomo

Mechanical Engineering ETDs

In this thesis, I document the design, testing and performance of a novel Expanded-Range Venturi Flow Meter (ERVFM) concept. The ERVFM combines two, parallel-configured Venturi Flow Meters (VFM) with a Solid-State Selector Valve (SSSV). The goal was to create a reliable, high-turndown ratio flow meter which directs the fluid to either Venturi tube using the inherent pressure drop of the SSSV, and without moving parts. I constructed a pumped-fluid loop test-setup and quantified the ERVFM’s performance through pressure loss and mass flow rate measurements. In addition, I used python to develop models to assist in prototype design and data-processing. My …

Fiesta And Shock-Driven Flows, Brian E. Romero

Mechanical Engineering ETDs

In this study, the interaction of a shock with various gas and particle interfaces is analyzed through simulations using a new, GPU capable, multi-species flow solver, FIESTA (Fast, Interface Evolution, Shocks, and Transport in the Atmosphere), de- veloped for this research. The cases studied include the interaction between a shock and i) a two-dimensional (2D), circular cloud of a dense gas; ii) a 2D curtain of a dense gas; iii) a three-dimensional (3D) cylinder of a dense gas, and iv) a 3D curtain of solid particles.

In simulations of a 2D gas curtain and a 3D gas column, the curtain …

Multi-Scale Modeling Of Dislocation Motion And Interaction: Theory, Plastic Properties, And Boundary Conditions, Abu Bakar Siddique

Mechanical Engineering ETDs

Dislocation theory is the fundamental tool for explaining plasticity in the material. The elastic field of a material is always influenced by the presence of dislocations and other defects independent of the loading configurations. Scientists and researchers have minimal success in solving plasticity problems analytically. And for this reason, the capturing of dislocation dynamics is highly dependent on numerical modeling, which is always a challenge for its inherent multi-scale nature. Current research investigates and develops self-consistent numerical models for different plasticity problems based on the distributed-dislocation technique and the collocation-point method. Numerical methods are developed for different boundary conditions in …

Understanding Processing And Mechanics Of Extrusion-Based Additive Manufacturing For Multi-Material Parts, Jafar N/A Ghorbani

Mechanical Engineering ETDs

Despite the design freedom that additive manufacturing (AM) processes provide, there are still challenges in using some AM processes for end-use products. Fused filament fabrication (FFF), also known as material extrusion, is one of the AM technologies that has been used mainly for prototyping due to the low cost of machines, raw material, and ease of operation. Another advantage of FFF is its ease of integration with other additive or subtractive technologies. However, some disadvantages such as relatively poor and anisotropic mechanical properties have hindered FFF for end-use engineering components. The first chapter of this dissertation is a brief review …

A Novel Imaging Methodology To Estimate Advective Losses From A Concentrating Solar Power Particle Receiver, Jesus Daniel Ortega

Mechanical Engineering ETDs

Falling particle receivers (FPRs) such as the one at Sandia National Labs, represent the state-of-the-art Concentrating Solar Power (CSP) technology for energy harvesting. The FPR operates by creating a gravity-driven particle curtain in a receiver that is irradiated by concentrated sunlight from a field of concentrators. The particles are used directly as the heat transfer and storage media for the concentrated energy absorbed. However, during operation, particles can egress through the open aperture of the receiver cavity, resulting in particle-inventory and heat losses from the system. The particle plumes egressing from the cavity present a unique challenge to metrology due …

Dc Microgrid Fault Detection Using Multiresolution Analysis Of Traveling Waves, Rudy Montoya

Mechanical Engineering ETDs

Fast detection and isolation of faults in a DC microgrid is of particular importance. Fast tripping protection (i) increases the lifetime of power electronics (PE) switches by avoiding high fault current magnitudes and (ii) enhances the controllability of PE converters. This thesis proposes a traveling wave (TW) based scheme for fast tripping protection of DC microgrids. The proposed scheme utilizes a discrete wavelet transform (DWT) to calculate the high-frequency components of DC fault currents. Multiresolution analysis (MRA) using DWT is utilized to detect TW components for different frequency ranges. The Parseval energy calculated from the MRA coefficients are then used …

Dc Microgrid Fault Detection Using Multiresolution Analysis Of Traveling Waves, Rudy Montoya

Mechanical Engineering ETDs

Fast detection and isolation of faults in a DC microgrid is of particular importance. Fast tripping protection (i) increases the lifetime of power electronics (PE) switches by avoiding high fault current magnitudes and (ii) enhances the controllability of PE converters. This thesis proposes a traveling wave (TW) based scheme for fast tripping protection of DC microgrids. The proposed scheme utilizes a discrete wavelet transform (DWT) to calculate the high-frequency components of DC fault currents. Multiresolution analysis (MRA) using DWT is utilized to detect TW components for different frequency ranges. The Parseval energy calculated from the MRA coefficients are then used …

Zero-Power Ac Current Sensor, Omar Aragonez

Mechanical Engineering ETDs

In this study, a magnetic piezoelectric cantilever powered AC current and frequency sensor is proposed. This paper covers the configuration of the experimental setup, finite element modeling of the magnetic coupling, and the optimal spatial location of the magnetic proof mass in relation to the wire for smart grid applications. Solid and stranded copper wires of various gauges were used and carried current up to 30A. The magnets act as a proof mass to lower the frequency while also coupling to the magnetic field generated by the current carrying wire. The frequency of the AC current produces a sinusoidal force …

Method Of Embedded Imperfections For The Direct Simulation Of Deformation Instabilities In Film-Substrate Structures, Siavash Nikravesh Kazeroni

Mechanical Engineering ETDs

In this dissertation, a novel finite-element methodology called “embedded imperfections” is proposed and employed for computationally simulating various types of deformation instabilities observed in film-substrate structures subjected to mechanical loading. The approach involves the incorporation of elements having distinctive material properties within the film-substrate interface. One can interpret this practice as a deliberate distribution of material defects within the numerical model. It has been shown that embedded imperfections not only can trigger the onset of instability, but also can lead to “direct” simulation of deformation instability problems in that primary and subsequent instability modes can all be captured in a …

Incorporating In-Situ Monitoring To Detect Anomalies In Additively Manufactured Kovar Steel On A Layer-To-Layer Basis, Matthew Aragon

Mechanical Engineering ETDs

Combining traditional methods of material analysis with in-situ monitoring of a Laser Powder Bed Fusion (LPBF) printed part, on a layer-to-layer basis, provides the data necessary to adjust printing parameters to achieve specific material properties. Additively manufactured technology has advanced in the ability to accommodate new materials and provide new use cases. Uncertainties in material properties have arisen alongside the advancements in additive manufacturing. The layer-wise print analysis will allow for detection and correlation of print anomalies to the material properties such as density, material strength, and surface roughness. The data processed from each layer will be used to further …