Mechanical Engineering Commons^™

Developing Simulation To Improve G3p3 Efficiencies, Andrew Gaudette

Mechanical Engineering ETDs

Concentrated solar power (CSP) systems offer a promising method of renewable energy generation by using heliostats to focus sunlight onto a falling particle receiver. At the National Solar Thermal Testing Facility (NSTTF), particles absorb and store solar energy for later power generation. A major source of efficiency loss is wind-driven particle escape through the receiver aperture. This thesis develops computational fluid dynamics (CFD) simulations to characterize wind flow around the G3P3 falling particle receiver and support future wind mitigation strategies. Numerical studies were conducted to establish an appropriate simulation methodology. Iteration studies showed that 2,000 iterations were sufficient for convergence, …

Control Of Reshock In A Shock Tube, Alexander Sweis

Mechanical Engineering ETDs

Reshocks can pose a threat to the structural integrity of structures and buildings. While incident shock waves pose larger threats, the study of reshocks and reshock attenuation is important to consider. This thesis investigates methods for controlling and attenuating reshock strength within a shock tube through material-based damping and modifications to baffle box geometric configurations. Experiments are performed using a custom-built shock tube in the University of New Mexico fluid mechanics laboratory. Four baffle box configurations are examined: a foam-lined configuration, a foam-lined configuration with ”egg crate-like” textured foam, an empty (no foam) configuration, and a configuration which incorporates a …

Assessing The Impact Of Multi-Physics Effects On Photovoltaic Module Degradation Using Computational Modeling, James Yuan Hartley

Mechanical Engineering ETDs

This dissertation describes research to develop and apply multi-physics simulation capabilities using finite element methods to analyze photovoltaic module damage mechanisms. Analyses of full-scale solar modules under mechanical load are presented, including experimental validation against measurements of external deflection and internal strain. Module damage by solar cell breakage and interconnection fatigue are discussed, and the applicability of simplifying analyses using mathematical plate theory is assessed. Detailed sub-module component models undergoing thermal-mechanical stressors are also presented, to identify the design features and materials most influential to stress generation and to assess the representativeness of using sub-module assemblies in accelerated testing. Finally, …

Active Brazing Of Single Crystal Al2o3 To Kovar Alloy With Agcuzr Filler Metal, Anthony M. Mcmaster

Mechanical Engineering ETDs

Brazing provides high strength and hermetic joining between metal, ceramic, and composite materials. Origins of the brazing process trace back to 3000BC, yet the technique continues to maintain relevance and demand across aerospace, medical, electronic, optical, and mechanical engineering. Here, single crystal Al2O3 (sapphire) was joined to Kovar in a single step via an AgCuZr active braze filler metal. The microstructure of the completed joint was investigating using microscopy and spectroscopy techniques. A unique braze chamber, paired with an optically clear top substrate (sapphire), allowed further investigation into the dynamics of the active braze process via in situ video monitoring. …

Graph Based Planning With Guarantees, Trazon Tyrik Jimerson

Mechanical Engineering ETDs

This thesis presents two graph-based methods with formal guarantees for motion planning and routing. First, the invariant-set motion planner (ISMP), which uses constraint admissible positive invariant (CAPI) sets of closed-loop dynamics, is adapted for spacecraft attitude planning to avoid moving keep-out zones. Contributions include time bounds for maneuvers via exponential stability, a single-stage reachability graph from one-step backward reachable CAPI sets, and its multi-stage expansion to certify node safety over time. Simulations verify safe attitude control with moving obstacles. Second, we formulate a convex optimization problem over a network for evacuation planning with operational constraints such as helicopter capacity and …

Real-Time Frequency Tuning Of Kinetic Energy Harvesters Via System Mass Adjustment, Rahul Adhikari

Mechanical Engineering ETDs

This research presents a method for real-time frequency tuning of piezoelectric kinetic energy harvesters through system-mass adjustment. Custom 3D-printed proof masses with cavity arrays were used to redistribute solid or liquid mass, enabling controlled modification of resonant frequency. Experimental studies using microparticles and liquids—including water, silicone oil, and sodium polytungstate—demonstrated an achievable tuning range of 115.27 Hz with sub-hertz resolution (< 0.1 Hz), confirming precise and repeatable frequency control. Finite-element modeling guided design optimization, while a microfluidic channel system enabled automated liquid filling for real-time operation. A MATLAB-based EH_Tuning application was developed to visualize and predict frequency responses. The combined …

Design And Development Of Evacuated Photovoltaic-Thermal Systems For Efficient Cogeneration Of Heat And Electricity, Behnam Roshanzadeh

Mechanical Engineering ETDs

In conventional PV systems, most of the solar energy is dissipated into the environment as heat. Accordingly, hybrid Photovoltaic-thermal systems have been developed to utilize the waste heat from PV cells for various thermal applications. However, most PVT systems suffer from low thermal performance compared to solar thermal collectors, as the absorber plate in PVT systems is partially or fully covered by PV cells. This dissertation focuses on improving the thermal performance of PVT systems by introducing the evacuated PVT systems.

An evacuated-tube PVT system was designed and simulated for domestic hot water supply. The evacuated-tube PVT system demonstrated 40% …

Simulation Of Stress Induced By Laser Heating Of Glass, Austin Marsh Schuberth

Mechanical Engineering ETDs

The purpose of this work is to create a method for accurately simulating the stresses due to heating from femtosecond laser pulses. Our work aims to calculate stress and strain in glass exposed to laser pulses used for laser welding. We simulate the effects of thermal heating, thermal expansion, and the viscoelasticity of glass for a single straight weld bead. The laser heating of K9 borosilicate glass was simulated using Finite Element Analysis (FEA). Thermal models developed by other researchers in earlier work were utilized in calculating the temperatures due to the laser exposure to the glass material. 2D simulations …

Predicting Leakage From Nuclear Material Containers At Los Alamos National Laboratory Through Drop Testing, Leak Testing, Finite Element Analysis And Digital Image Correlation, Jude M. Oka, Yu-Lin Shen, Osman Anderoglu, Pankaj Kumar, Rajendra Vaidya

Mechanical Engineering ETDs

Los Alamos National Laboratory (LANL) relies on containment vessels to safely manage special nuclear material. These containers are subject to rigorous testing—such as drop, fire, and water ingress testing—to ensure integrity under adverse conditions. While elastomer-based seals are well studied, metal-to-metal sealing mechanisms remain under investigation, particularly under dynamic loading. This research focuses on the relationship between container mating surfaces and impact loading through drop testing. Finite Element Analysis (FEA) models were developed and validated using Digital Image Correlation (DIC) to measure strain during impact. Drop tests at varying heights showed strong correlation between FEA and DIC results, confirming the …

Networked Systems: Synchronization, Decomposition And Transient Dynamics, Amirhossein Nazerian

Mechanical Engineering ETDs

This dissertation investigates synchronization, transient dynamics, control, and signal amplification in networked dynamical systems. First, it examines complete and cluster synchronization, including cases with large parametric mismatches, in both natural (e.g., brain networks, fireflies) and technological systems (e.g., power grids, robotics). Second, it studies transient dynamics in consensus processes, designing synchronization strategies that link reactivity, contraction theory, and Lyapunov exponents. Third, it addresses the computational limits of Model Predictive Control (MPC) for large networks by introducing an algebraic decomposition method that enables parallel online computation of smaller subproblems, enhancing MPC performance under hardware constraints. Finally, it analyzes the structural role …

Instability Analysis In Cylindrical Thin Film–Compliant Core Structures: Numerical Simulations And Effects Of Inelastic Deformation, Md Al Rifat Anan

Mechanical Engineering ETDs

When a thin film bonded to a thick compliant substrate is subject to in-plane compression, wrinkles can develop if the critical state for instability is reached. In various applications the film/substrate system may also take the form of cylindrical fibers, where an axial compressive loading can trigger axisymmetric wrinkles. A straightforward computational approach to simulate such wrinkling behavior is needed for material design, to either prevent wrinkling or to exploit its benefits for flexible device applications. In this work a comprehensive numerical study is undertaken by employing the finite element method. The embedded imperfection approach used previously for planar structures …

Multiscale And Multi-Model Studies Of Metal Plasticity, Luo Li

Mechanical Engineering ETDs

Plastic deformation is the process in which the material deforms permanently due to external effects. Twinning and slip are two main mechanisms of plastic deformation in metallic materials. The prominent mechanism of plastic deformation in metals that have FCC crystal structures is slip or gliding movement of dislocations, which is mainly focused on here. In the current study, frameworks for investigating plasticity phenomena of metals at different scales ranging from microscale to macroscale are demonstrated. Specifically, the macroscale modeling of plastic response of metallic materials induced by indentations are emulated by nonlinear FEA simulations. Simulation results of macroscale modeling are …

Data-Driven Constrained Control, Ali Kashani

Mechanical Engineering ETDs

Ensuring safety is a fundamental challenge. Traditional methods often rely on precise mathematical models, which are difficult, impractical, or costly to obtain for real-world systems with complex, nonlinear dynamics. This dissertation develops direct data-driven control approaches that enable safe and efficient operation of nonlinear systems without requiring explicit models or performing system identification. This effort leverages machine learning, optimization, and control theory to bridge theoretical rigor and practical applicability. Deterministic guarantees are provided based on the Lipschitz continuity of the system, and probabilistic guarantees through scenario optimization. The computation of safe sets is performed using one-shot approaches with broad neural …

Evaluation Of Electrode Configurations For (0,2) Piezoelectric Ultrasound Transducers, Abdul Qayoum Popal

Mechanical Engineering ETDs

Piezoelectric micro ultrasound transducers (PMUT array) are pivotal in MEMS applications. They typically operate in the fundamental (0,1) acoustic mode and are not significantly researched for higher modes (0,2) and (0,3). Similarly, vibrating mesh atomizers (VMAs) demand the second (0,2) mode and third mode (0,3) for effective aerosol generation, highlighting the need for optimized electrode configurations—a relatively unexplored area. This study presents the first comprehensive analysis of how electrode designs influence PMUT performance in the (0,2) mode for VMA applications.

Utilizing COMSOL multiphysics finite element modeling (FEM) with residual stress considerations alongside experimental validation, we demonstrate that optimized electrode configurations …

Custom Cathode Optimization For Electropolishing Additively Manufactured 316l Stainless Steel, Kasandra Escarcega Herrera

Mechanical Engineering ETDs

Laser powder bed fusion (LPBF) has become increasingly popular for its ability to rapidly manufacture complex metallic parts. However, the surface properties of as-built LPBF parts may degrade overall performance due to tortuous surface features. Consequently, post-processing like electropolishing (EP) to reduce the surface asperities is often needed for LPBF parts to perform as expected. Utilizing experimental and computational approaches, this project aims to more uniformly EP complex shaped parts made from LPBF 316L. For the experimental approach, parts with a three-dimensional T-shape were printed out of 316L stainless steel and EP using an acidic-based and a polyethylene glycol/NaCl-based electrolyte. …

Robust Data-Driven Run-To-Run Control Via One-Step Constrained Optimization For Automated Serial Sectioning, Rhianna M. Oakley

Mechanical Engineering ETDs

This Thesis develops a one-step predictive run-to-run controller (R2R-MPC) for automating a mechanical serial sectioning (MSS) system. MSS is a destructive material analysis process that iteratively removes slices of material and captures 2D images, reconstructing them into 3D representations. Commonly used in material science for characterizing materials and failure analysis, MSS typically operates in an open-loop fashion, which experiences high variability in material removal due to system disturbances. To address this, a robust closed-loop R2R-MPC is presented, modeling MSS process uncertainty using a linear differential inclusion identified from operational historical data. The R2R-MPC is posed as an optimization problem that …

Tuning Of Real-Time Optimization Of Heliostat Concentrated Solar Power, Zachary L. Bernius

Mechanical Engineering ETDs

This paper investigates a real-time optimization algorithm for autonomously calibrating the heliostats in a concentrated solar power plant with the goal of maximizing power generation. The current state-of-the-art uses human operators to provide feedback for the heliostats. We use real-time/online measurements to produce an autonomous closed-loop system that does not require human intervention. The paper investigates tuning the gain of the real-time optimization algorithm to quickly and robustly converge to the optimal alignment and stabilize the system. The exponential stability of the system is certified using a quadratic Lyapunov function and static output feedback methods to couple the Lyapunov functions …

Sofast Cad Layout Tool, Felicia Brimigion

Mechanical Engineering ETDs

Concentrating solar mirrors need to have correct geometry to accurately focus sunlight onto a receiver. SOFAST is a tool created at Sandia National Laboratories which measures a mirror’s surface normal at a dense sampling of points, enabling evaluation of a given mirror’s expected performance. SOFAST supports general mirrors, including concentrating solar heliostats, troughs, and dishes. The examples presented in this report predominantly focus on heliostats.

There are generally four major components of a SOFAST system – the mirror, camera, projector, and screen. For SOFAST to properly measure a mirror, the following geometric constraints must be satisfied:

1. The reflection of …

Mechanical Characterization And Evaluation Of Additively Manufactured Titanium 5v-5mo-5al-3cr Alloy, Zachary Casias

Mechanical Engineering ETDs

Ti-5V-5Mo-5Al-3Cr (Ti-5553) is a near beta titanium alloy commonly used in aerospace applications. It is currently being explored for additive manufacturing (AM), but the fatigue behavior of this AM alloy needs to be well-understood for adoption in aerospace applications. The present work examines the tensile and fatigue behavior of LPBF manufactured Ti-5553. The effect of post-print heat treatments, effects of surface roughness, and print defects on the mechanical properties of AM Ti-5553 were also evaluated. Fatigue lives of as-LPBF and BAA material are nearly identical, and both are far below the fatigue lives of conventionally manufactured Ti-5553 of 350 MPa. …

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 …

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 …

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 …

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, …

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.

Reference Governor For Air-Conditioner, Ganiyu E. Azeez

Mechanical Engineering ETDs

Advanced control for heating ventilation and air-conditioning (HVAC) systems has primarily focused on optimizing energy efficiency. However, ensuring the safe and reliable operation of HVAC equipment is another crucial control objective. This Thesis presents a reference governor (RG) that can augment existing energy-optimized controllers with the capability to enforce constraints to ensure safe and reliable operation. The RG makes minimal adjustments to the reference room temperature setpoint to ensure that the refrigerant entering the compressor is super-heated, thereby preventing potential damage. Designing the RG requires synthesizing a constraint admissible positive invariant (CAPI) set which characterizes the subset of states for …

Wind Farm Optimization And Analysis Of Complex Wake Structures, Rubel Chandra Das

Mechanical Engineering ETDs

A high-fidelity computational solver was developed with direct numerical simulation (DNS), large eddy simulation (LES), and Concurrent Precursor Method (CPM) capabilities. Extensive validation ensured the solver's accuracy in modeling fluid dynamics, including the wake characteristics of both utility and miniature-scale wind turbines. Key performance statistics (e.g., velocity and turbulence intensity profiles) were compared against established theoretical, computational, and experimental results. The study examined the influence of ground clearance on turbine performance, comparing two scenarios with different hub heights. Results showed that larger ground clearance facilitates quicker wake recovery. Finally, the study uses a nine-turbine array model to explore wind farm …

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 …