Mechanical Engineering Commons^™

Gpu-Enabled Genetic Algorithm Optimization And Path Planning Of Robotic Arm For Minimizing Energy Consumption, Yichuan Cao

Theses and Dissertations

The robotic arm represents a complicated mechanical system and advanced engineering principles in robotics, enabling precise and efficient manipulation and interaction with objects in a variety of applications, such as manufacturing, healthcare, space exploration, and other industries. In most cases, energy consumption of robotic tools has been given little consideration due to their perceived insignificance compared to the benefits they offer. However, the increasing capacity demands of factories and the expanding use of robotic arms necessitate careful evaluation and reduction of energy consumption. In this regard, given a task configuration, adjusting the arm's movement path emerges as one of the …

Liquid Cooling System For A High Power, Medium Frequency, And Medium Voltage Isolated Power Converter, Hooman Taghavi

Theses and Dissertations

Controlling and transforming electrical power from one form into another is the Primary function of the power electronics systems that are employed today. These systems have a wide variety of applications and are utilized in things like industrial automation, electric cars, consumer electronics, and renewable energy systems, among other things. The functioning of power electronics systems results in the production of a substantial quantity of heat, despite the fact that these systems are very dependable and efficient. This heat must be dispersed to preserve system performance and avoid component damage. By ensuring that the working temperature of the components stays …

Development Of Atomistic Machine Learning Approaches For Thermal Properties Of Multi-Component Solids And Liquids, Alejandro David Rodriguez

Theses and Dissertations

Currently, heat transfer in many industries is the limiting factor for innovation, especially in the energy sector. For example, maximizing thermal conductivity of ceramic coatings in power plant devices improves the overall electrical to thermal energy ratio, whereas minimizing thermal conductivity is required for desirable heat-to-electricity conversion in thermoelectric devices. As such, rapid discovery of new materials with extreme thermal conductivity values is quintessential for the near-future deployment of current and developing energy applications.

The vibrational properties of crystalline materials are essential for their ability to conduct heat. Fundamentally, the restorative atomic forces of displaced atoms are sufficient to represent …

Automated Fiber Placement Through Thickness Defect Stacking Optimization, Noah Christopher Swingle

Theses and Dissertations

In its 2022 commercial market outlook, Boeing forecasted an 80% increase in the global fleet through 2041 compared to 2019 pre-pandemic levels. This sharp rise in demand will drive pressure onto airframe manufacturers to ramp up production and find more efficient ways to design and manufacture airplanes. Complicating this challenge is the industry’s recent transformation from traditional metal-based airframes towards hybrid composite-metal aircraft. While composites have been used in aviation for decades, aircraft manufacturers are still struggling to design and manufacture quality parts at a high rate. Automated Fiber Placement (AFP) is one of the main manufacturing techniques used to …

Spin Mediated Topological Black Hole In Acoustic Metamaterials Near Dirac-Like Cone Frequencies., Mustahseen Mobashwer Indaleeb

Theses and Dissertations

A unique bulk-boundary distinction and acoustic topological phenomena is discovered and explained in this dissertation. The overall objective was to discover the hidden physics, dynamic and mechanics of acoustic wave behavior that causes the formation of extremely rare ‘Topologically protected Black Hole’ (TBH) in acoustic microarchitecture metamaterials. This behavior is immensely valuable for numerous mechanical and civil engineering applications where acoustic insulators are required to create sound-free or vibration-free exterior surfaces. On the other hand, to contain the energy within the structure, for impact mitigation and energy absorption in vehicles, space crafts, aircrafts, and civil infrastructures such materials will be …

Leveraging Automated Fiber Placement Computer Aided Process Planning Framework For Defect Validation And Dynamic Layup Strategies, Joshua Allen Halbritter

Theses and Dissertations

Process planning represents an essential stage of the Automated Fiber Placement (AFP) workflow. It develops useful and efficient machine processes based upon the working material, composite design, and manufacturing resources. The current state of process planning requires a high degree of interaction from the process planner and could greatly benefit from increased automation. Therefore, a list of key steps and functions are created to identify the more difficult and time-consuming phases of process planning. Additionally, a set of metrics must exist by which to evaluate the effectiveness of the manufactured laminate from the machine code created during the Process Planning …

Experimental Observation Of Sphere Symmetric Isolated Single Droplet Combustion In A Converging Channel, Mason Carrington Williams

Theses and Dissertations

Spherically symmetric isolated single droplet combustion has been observed mainly in microgravity conditions. This study sought to determine if spherically symmetric combustion can be produced in a lab-scale experiment using flow acceleration to counteract the effects of buoyancy. The experiment was conducted in a converging channel that decreased in width along its length to accelerate the flow and limit the formation of a boundary layer. The rate at which the area decreased was governed by the initial velocity condition set at the channel inlet.

The droplets were generated using a piezoelectric actuator which forced fuel out of an injector with …

Nondestructive Damage Detection And Stress Corrosion Crack Mitigation In Stainless Steel Plates, Andrew Philip Campbell

Theses and Dissertations

The ability to inspect and detect damage within a structure without permanent damage has broad appeal in a range of engineering applications from aerospace structures to nuclear facilities. Non-destructive evaluation (NDE) using guided ultrasonic Lamb waves has growing potential and popularity in these fields. Lamb waves are known for being sensitive to material properties and various defects across the thickness such as cracks in metallic structures and delamination or debonding in composite structures. Research has also been done on the development of fully non-contact system that generates and detects Lamb waves, particularly focused on the use of pulsed laser for …

Comprehensive Process Planning Optimization Framework For Automated Fiber Placement, Alex Ryan Brasington

Theses and Dissertations

Advanced composite materials came about in 1966 and have since been widely used due to the possibility of superior structural performance while also achieving weight reductions. Such opportunities have led to composite materials being used to fabricate complex components, often in the aerospace sector. Most components, especially in aviation, are on a large scale and are outside the capabilities of traditional composite manufacturing techniques. Traditional manufacturing methods are also labor intensive, time consuming, have a high level of material scrap, and are prone to human error. This has led to the need for innovative manufacturing solutions to withstand the ever-increasing …

Vision Controlled Autonomous Stakebot For Driving Stakes And Its Digital-Twin, Corey Lee Leydig

Theses and Dissertations

In this thesis a novel vision-based AI driven autonomous ‘StakeBot’ is proposed to serve the agricultural 4.0 industries of the future. In recent years supply, demand and production of vegetables that are harvested from plants with weak stems like bell pepper, tomato, eggplant has been significantly up by several fold. With growing demand and new green-house establishments across the country production of vegetables will require a tremendous number of labors which will be hard to supply soon. To overcome the issues in addition to the labor shortages, automation through robotics will be the only viable solution. Plants like bell peppers …

Timing Deterministic Structural Model Updating Considering Impact And Fatigue Damage, Jason Michael Smith Jr.

Theses and Dissertations

Naval ship structures such as support trusses, hull sections, driving machinery, and load-bearing beams are subjected to various damage states that develop on short-term (i.e. impact) and long-term (i.e. fatigue) timescales. Naval structures fitted with a structural health monitoring system with damage detection abilities will enable appropriate real-time adjustments to the ships’ posture and control policies and thus have increased survivability and lethality. A digital twin can provide real-time condition assessment of naval structures when conjoined with a decision-making framework will increase naval ship survivability through informed response management. A fundamental challenge for the development of digital twins is reliable …

An Artificial Intelligence Approach To Fatigue Crack Length Estimation From Acoustic Emission Signals, Shane T. Ennis

Theses and Dissertations

As in service aircraft begin to age and fatigue, a method for evaluating the operational life they are currently operating under and have remaining comes into question. Structural health monitoring is (SHM) is a popular method of structural analysis with growing interest in the aerospace industry. SHM is capable of damage assessment and structural life estimations.

The ultimate goal of the research presented in this thesis is to develop a methodology of classifying the length of a fatigue crack though the use of machine learning. The thesis has three major chapters as described below.

The first chapter deals with the …

An Autonomous Aerial Drone System For Water Fluorescence Mapping And Targeted Sampling, Kazi Ragib Ishraq Sanim

Theses and Dissertations

At present, aerial drones, also known as Uncrewed Aircraft Systems (UAS) or Unmanned Aerial Vehicles (UAV), are increasingly used in time and effort-heavy scientific exploration applications. One such application is inspecting the physical, chemical, and biological state of water bodies. This thesis presents a novel autonomous system capable of sensing water properties and collecting up to three 250 mL water samples from multiple sampling locations. The system features a customized aerial drone with an in-house built fluorescence sensor and pumping mechanism. It can also map the gradient of fluorescent content across the body of water to determine the best sampling …

Development Of System Pressure Drop Calculation Methods For Dilute Phase Pneumatic Conveying, Ross Daniel Gorman

Theses and Dissertations

This work is focused on dilute and dense phase pneumatic conveying of bulk solids. The motivation of this work is to use industrial data to scale up existing models for pressure drop in pneumatic conveying systems, determine which models best predict pressure drop in full conveying systems, and find the empirical coefficients that go with these models.

Several major research objectives were accomplished by this work. First, system pressure drop methods were evaluated in this research. Other researchers have focused on single pipe section type pressure drops. Second, the data used in this research both for the machine learning evaluations …

Multidimensional Transport-Coupled Numerical Investigation Of Non-Premixed Low-Temperature Flame In Atmospheric And High-Pressure Systems, Sudipta Saha

Theses and Dissertations

Gas-phase chemical reactions coupled with multidimensional fluid flow and heat and mass transport are found in various applications, i.e., from conventional engine applications to novel combustion techniques. With the goal of understanding such complex coupling in reacting flow systems, this dissertation work focuses on developing multi-physics simulation frameworks to investigate the effect of multidimensional transport on flame dynamics. This study primarily focuses on the modeling and simulation of low temperature flame formation in i) a canonical experimental setting with counterflow burners and ii) a supercritical water medium (i.e., hydrothermal flame).

In the first part of the dissertation, simulations of the …

Experimental Investigations Of Yarn Pull-Out Behavior In Kevlar®: Influence Of Applied Metallic Coatings And Effect Of Dynamic Loading, Julie Ann Roark

Theses and Dissertations

Flexible woven Kevlar® textile fabrics are widely used in protective armor applications. Yarn pull-out, comprised of yarn uncrimping (i.e., straightening) and yarn translation, is a major energy absorption mechanism during ballistic impact onto these fabrics, especially for impact velocities below the ballistic limit. Yarn pull-out is influenced by various parameters including inter-yarn friction, pull-out distance, pull-out velocity, transverse pre-tension, fiber diameter, fabric architecture, fabric waviness, fabric count and yarn modulus.

The first part of this thesis investigates yarn pull-out behavior of commercially available Kevlar® KM2+ individual yarns coated with metallic layers (copper, aluminum, aluminum nitride, silver) via a directed vapor …

Use Of Dic Measurements With Finite Element Models For Direct Heterogeneous Material Property Determination And Wrinkle Formation During Automated Fiber Placement, Sreehari Rajan Kattil

Theses and Dissertations

In this work, application of DIC in combination with finite element modeling is demonstrated for efficient material characterization for complex heterogeneous materials and tow wrinkle formation during automated fiber placement.

The first part of the work describes the integration of DIC measurements with finite element models for direct property identification in heterogeneous material systems. The material property identification is based on solving partial differential equations (PDE) of equilibrium for unknown elastic material properties with known boundary conditions and full field strain data (Eg. DIC). The PDEs are solved numerically using Petrov-Galerkin finite element procedure. The classical Bubnov-Galerkin method is shown …

Molten Salt Thermal Properties Database – Thermochemical Development And Thermodynamic Assessment Of Various Molten Salt Systems, Johnathon Chandler Ard

Theses and Dissertations

The Molten Salt Thermal Properties Database – Thermochemical (MSTDB-TC) is a validated open-source database for thermochemical modeling of molten salt reactor (MSR) relevant fluoride and chloride salt systems. The database has been created and populated by leveraging available models from literature as well as completing novel system assessments. The development and contents of the MSTDB-TC v1.2 initial release are detailed along with various system assessments performed in the course of the work. The database utilizes a major strength of the CALPHAD thermodynamic modeling method. This is the ability to estimate higher-order system behavior by combining modeled lower-order systems, …

A Hybrid Experimental-Computational Study: Prediction Of Flow Fields And Full-Field Pressure Distributions On Three-Tab Asphalt Roofing Shingles Subjected To Hurricane Velocity Winds, Troy A. Myers

Theses and Dissertations

A novel hybrid experimental-computational study is performed to predict the flow fields and pressure distributions on the measured shapes of flexible, three-tab asphalt roofing shingles undergoing increasing uplift when exposed to hurricane velocity winds. StereoDIC analysis is performed to measure the transient full-field deformed shapes of full-size three-tab asphalt shingles when subjected to hurricane velocity winds for two hours. Steady state computational fluid dynamics (CFD) simulations of the shingled roof facsimile-plenum region representative of the experiments are successfully performed. The simulations are performed to predict wind loading of the uplifted shingle shapes by utilizing the measured full-field three-dimensional uplifted shapes …

Shear Localization In The Metallic Nanolayered Composites, Shujing Dong

Theses and Dissertations

In this dissertation, the influences of layer thickness (h), interface orientation relationship (OR) and dislocation slip activities on shear band (SB) formation mechanisms was investigated by means of molecular dynamics (MD) simulations.

The effect of h and dislocation slip systems on the shear localization in Cu-FCC/Nb-BCC MNCs was studied. The strain softening observed in those samples was triggered by the SB formation. The microstructure evolutions and dislocation slips revealed that the unsymmetrical dislocation transmission across the interface induces the shear localization and promotes the SB formation. The quantitative analysis of the change in the separation distance of initially …

Towards Modeling Of Induction Welding Of Thermoplastic Laminates With A Mixed Finite Element Boundary Element Approach, Florentius Johannes Van Zanten

Theses and Dissertations

There is an increased interest in induction welding of carbon fiber reinforced thermoplastic composite laminates within the aerospace industry. Currently, optimal manufacturing process parameters (e.g., current, power, and frequency settings, coil movement speed, etc.) are determined through an experimental trial-and-error approach. To reduce the need for an experimental approach that can determine the manufacturing process parameters, which would be expensive in both time and money, accurate and computationally efficient numerical tools are desired. This research is focused on improving the existing numerical tool, WelDone, in regard to its speed and accuracy.

WelDone utilizes a hybrid element formulation that combines traditional …

High-Throughput Computation Of Interfacial Thermal Management Of Wide-Bandgap Semiconductors, Hao-Wen Chen

Theses and Dissertations

As semiconductor electronics, in particular high electron mobility transistors, get hot in operation, people are trying to incorporate different semiconductor materials to solve the problem of heat dissipation to maintain the device efficiency and performance. In this master thesis, two different packages, LAMMPS and almaBTE, that are focusing on micro-scale and atomic scale respectively, are used to simulate the heat transfer process across interfaces in two different scales. In the LAMMPS simulation, the research is exploring how the location of atoms and the thickness of interfacial layers will influence the interfacial thermal conductance. On the other hand, using the almaBTE …

Uncrewed Aircraft Systems For Autonomous Infrastructure Inspection, Michail Kalaitzakis

Theses and Dissertations

Uncrewed Aircraft Systems (UAS) are becoming increasingly popular for infrastructure inspections since they offer increased safety, decreased costs and consistent results, compared to traditional methods. However, there are still many open challenges before fully autonomous, reliable, and repeatable UAS inspections. While a UAS platform has increased mobility and can easily approach hard to reach areas, it has limited range and payload capacity and is susceptible to environmental disturbances. Therefore, current operations are limited to Visual Line of Sight (VLOS) manual inspections that usually result in just a qualitative (visual) assessment of the structure.

The objective of this work is to …

Fabrication Of Asymmetrical Hollow Fiber-Supported Thin Film Membranes, Stack Assembly, And Accelerated Long-Term Stability Test For Oxygen Production From Air, Myongjin Lee

Theses and Dissertations

Air separation is a widely used process for oxygen production. Several separation technologies have been developed for air separation, including cryogenic distillation, swing adsorption, redox process of metal oxides, and electrochemical process. Among these technologies, electrochemical permeation process stands out as a cost-effective and simple process for pure oxygen production from air. The electrochemical permeation process employs a gas-tight membrane to permeate and separate oxygen from air directly, where the membrane conducts both ions and electrons simultaneously. Different membrane designs have been studied to obtain the improved performance for oxygen permeation, typically planar and tubular designs. Among these membrane configurations, …

Impacts Of Preferential Vaporization Of Multi-Component Liquid Fuels On Near-Limit Combustion Behaviors, Seungjae Lim

Theses and Dissertations

Combustion technologies used in energy conversion devices involve multi-phase and multi-component combustion behaviors associated with chemical kinetic characteristics coupled with spray dynamics. For reliable engine operation, the engine operation envelope is necessarily required to be determined by near-limit combustion behaviors such as flame flashback, lean blowout, ignition, and extinction, which are influenced by both fuel chemical and physical properties. Liquid fuels are composed of a wide range of molecular structures and weights, therefore exhibiting relatively large distillation temperature range. When fuel chemical properties change during fuel vaporization, preferential vaporization effects could play a considerable role in near-limit combustion behaviors. In …

Hybrid Theory-Machine Learning Methods For The Prediction Of Afp Layup Quality, Christopher M. Sacco

Theses and Dissertations

The advanced manufacturing capabilities provided through the automated fiber placement (AFP) system has allowed for faster layup time and more consistent production across a number of different geometries. This contributes to the modern production of large composite structures and the widespread adaptation of composites in industry in general and aerospace in particular. However, the automation introduced in this process increases the difficulty of quality assurance efforts. Industry available tools for predicting layup quality are either limited in scope, or have extremely high computational overhead. With the advent of automated inspection systems, direct capture of semantic inspection data, and therefore complete …

Nondestructive Material Characterization Using A Fully Noncontact Ultrasonic Lamb Wave System For Thin Metals, Nuclear Cladding, And Composite Materials, Elsa Z. Compton

Theses and Dissertations

Effective non-destructive evaluation (NDE) inspection system and methods are highly desired in a broad range of engineering applications including thin metal structure thickness evaluation. Ultrasonic guided waves in thin-walled structures, namely Lamb waves, have gained popularity as a NDE method. By using the ultrasonic waves in conjunction with high spatial resolution multidimensional wavefield measurements, thickness evaluations for thin metals can be achieved. This thesis explores the configuration and application of a fully noncontact ultrasonic Lamb wave NDE system for thickness characterization and evaluation of very thin metal plates. We have tested the actuation and sensing of Lamb waves for thickness …

Fundamental Study Of Multiphase Solid/Molten Carbonate Membranes For Co2 Capture And Conversion, Xin Li

Theses and Dissertations

Due to the burning of fossil fuels and human activities, many greenhouse gases such as carbon dioxide are released into the atmosphere, which causes global warming and has a significant negative impact on the human living environment. Therefore, it is imperative to develop carbon capture technologies that can prevent carbon dioxide emission and reduce carbon dioxide concentration in the air. Further, if the captured carbon dioxide can be converted back to fossil fuels, the emission of carbon dioxide is delayed, and more time is gained to develop new and advanced carbon free and clean energy technologies. Motivated by this thought, …

Advancement Of New Solid-Oxide Iron-Air Battery (Soiab) Operated On High-Temperature Oxide-Ion Chemistry, Qiming Tang

Theses and Dissertations

Climate change caused by anthropogenic greenhouse gas (GHG) emissions such as the burning of fossil fuels for power generation and industrial processing is affecting the global climate. To address this critical issue, a transition from fossil energy to renewable energy, especially wind and solar, is necessary. However, to successfully realize this transition, a cost-effective and large-scale stationary electricity storage system is indispensable. In this work, a new type of solid-oxide iron-air battery (SOIAB) operated on high-temperature oxide-ion chemistry is studied for this purpose due to its unique cycling characteristics suitable for large-scale Long Duration Electricity Storage (LDES) applications.

In the …

On The Influence Of Afp-Induced Defects On Mechanical Behavior Of Composite Laminates Under Fatigue Loading, Pierre Chevalier

Theses and Dissertations

The objective of the work presented in this thesis is to propose and validate a numerical solution to quantify the influence of Automated Fiber Placement (AFP) induced defects on the mechanical behavior of conventional composite laminates in fatigue. The work presented here will be divided in six sections. At first, a description of the Automated Fiber Placement process and its associated defects is proposed. In association, two tools developed for a rapid analysis and a progressive damage analysis respectively are discussed and used as an introduction to the work conducted in this thesis. In the second section, an extensive literature …