Engineering Commons^™

Measurement And Simulation Of Aeroacoustic Sources Generated By Elementary Muffler Components, Seth Donkin

Theses and Dissertations--Mechanical Engineering

Mufflers and silencers are commonly used to control noise from sources such as internal combustion engines and heating, ventilating, and air conditioning (HVAC) systems. In these applications, flow interacts with muffler components generating aeroacoustic noise sources. In order to measure these sources in a lab setting, specialized flow rigs are designed to isolate aeroacoustic noise sources. Flow sometimes compromises muffler performance. However, muffler performance is sometimes improved because flow can increase the attenuation of some muffler elements such as perforates. To better understand the complicated impact of flow, the University of Kentucky developed a muffler test rig to measure insertion …

Propagation Of Vibro-Acoustic Energy In Ducts: Measurement, Simulation, And Attenuation Studies, Caoyang Li

Theses and Dissertations--Mechanical Engineering

Vibro-acoustic energy propagates through heating, ventilating, and air conditioning (HVAC) systems through both airborne and structureborne paths. In this research, measurement and simulation studies are performed to better understand this propagation of energy and how to better attenuate the sound before it impacts building occupants.

First, a scaled-down experiment was developed to assist in the validation of numerical simulation models. A small source room was attached to a wooden duct with variable cross-sectional area. The sound power for both untreated and treated ductwork was measured using sound intensity scanning, and the insertion loss is the difference between untreated and treated …

Droplet Analysis Of Spray Inside A Compact Column Gas Scrubber Through Shadowgraphy, Brandon Heller

Theses and Dissertations--Mechanical Engineering

The shadowgraphy imaging technique was adapted to analyze the droplet field from a spray nozzle inside the gas absorption section of a compact column gas scrubber. This technique in conjunction with a developed image processing technique was able to gain statistical size information at different distances from two types of spray nozzles. The gas scrubber then ran a parametric campaign of eight operating conditions and statistical size information was captured for each case with the goal of understanding how operating conditions affect the droplet field properties. Lastly, several simulations were completed to understand how the addition of recirculation zones would …

High-Fidelity Coupling For Studies Of Ablative Materials At Hypersonic Conditions, Aleksander Zibitsker

Theses and Dissertations--Mechanical Engineering

The development of accurate models and robust numerical tools for simulating ablative thermal protection materials (TPMs) in hypersonic flows is crucial for advancing atmospheric entry and hypersonic technologies. Traditional methods for simulating ablative materials often rely on heavy assumptions, such as equal heat and mass transfer coefficients and chemical equilibrium in the boundary layer, leading to conservative thermal protection system (TPS) designs and insufficient accuracy for certain in-flight ablation phenomena.

This work presents a high-fidelity and versatile coupled framework between hypersonic flow and material response solvers. The flow domain is modeled with an innovative overset CHAMPS NBS-Cart solver, which features …

Pulse-Width Modulation Spray System Performance And Development Of A Novel System To Optimize Spray Use Efficacy, Prashanta Pokharel

Theses and Dissertations--Biosystems and Agricultural Engineering

The overarching objective of this research was to enhance our understanding of pulse width modulation (PWM) based nozzle control system and develop an intelligent nozzle control system for agricultural spray applications. This dissertation focused on measuring and analyzing the transient nozzle pressure characteristics and performance under PWM control. Additionally, it explored the development of an innovative multi-degree-of-freedom (DOF) nozzle control system for precise chemical applications in specialty crop systems.

The pressure dynamics of a PWM system were studied by developing an instrumentation system capable of operating a solenoid valve and recording pressure signals. A nozzle body and two manifolds of …

Thermomechanical Process Simulation And Quantification Of Nanoscale Precipitation Influencing Ductility And Strength During Alloy Processing, Alyssa Stubbers

Theses and Dissertations--Chemical and Materials Engineering

Experimental process simulation and quantification of microstructure development during processing are challenging due to limitations with machinery temperature capability, inadequate resolution and sampling volume of currently available characterization techniques, and difficulty characterizing material microstructures as close to processing-relevant conditions as possible. This dissertation addresses how process simulation can be performed using Gleeble thermomechanical technologies and how microstructure development during these processing simulations can be quantified both in-situ and ex-situ.

The first portion of this dissertation demonstrates how Gleeble technologies can be applied to simulate complex material processing conditions in order to produce process-property profiles that can be used to inform …

Advanced Microstructural Characterization Of Functionally Graded Dental Ceramic Material For Materials-Informed Finishing, Angani Vigneswaran

Theses and Dissertations--Manufacturing Systems Engineering

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has gained popularity as the choice of material for dental prosthetics. Ivoclar Vivadent’s IPS e.max ZirCAD Prime dental ceramic incorporates a unique gradient technology that varies the yttria content over the thickness of the material. The top layer is composed of 5Y-TZP which is desired for its optical properties while the bottom layer is composed of a much stronger 3Y-TZP. In between the two layers, 5Y-TZP and 3Y-TZP are mixed to form a transition layer. Varying the amount of yttria allows for more esthetically pleasing translucency in the visible areas of the restoration without compromising …

Mechanical Energy Harvester For Powering Rfid Systems Components: Modeling, Analysis, Optimization And Design, Alireza Babaei

Theses and Dissertations--Mechanical Engineering

Finding alternative power sources has been an important topic of study worldwide. It is vital to find substitutes for finite fossil fuels. Such substitutes may be termed renewable energy sources and infinite supplies. Such limitless sources are derived from ambient energy like wind energy, solar energy, sea waves energy; on the other hand, smart cities megaprojects have been receiving enormous amounts of funding to transition our lives into smart lives. Smart cities heavily rely on smart devices and electronics, which utilize small amounts of energy to run. Using batteries as the power source for such smart devices imposes environmental and …

Anisotropic Material Behavior Of 3d Printed Fiber Composites, Jordan Garcia

Theses and Dissertations--Mechanical Engineering

Literature has shown that 3D printed composites may have highly anisotropic mechanical properties due to variation in microstructure as a result of filament deposition process. Laminate composite theory, which is already used for composite products, has been proposed as an effective method for quantifying these mechanical characteristics. Starting with the analysis of comparing the printing orientation of premanufactured carbon fiber reinforced filament, the mechanical properties of 3D printed objects were examined. The mechanical properties changed not only as a result of machine choice, but how the sample is oriented along the printing bed. The analysis continued with looking at the …

A Computational Fluid Dynamic Analysis Of Oxyacetylene Combustion Flow For Use In Material Response Boundary Conditions, Craig Meade

Theses and Dissertations--Mechanical Engineering

Oxyacetylene torches are used in the aerospace industry and research to test thermal protection system materials (TPS) due to their high flame temperatures and high heat flux capabilities. The purpose of this work is to determine a combustion model to accurately simulate the high temperature flow of an oxyacetylene torch. The flow conditions around a sample material can then be used as boundary conditions when modeling TPS material response. Two separate combustion models with equilibrium chemistry were investigated using ANSYS Fluent™; the Eddy-Dissipation Model, and the Partially Premixed model.The results of this study are compared to existing experiments for validation.

Impact Of Spallation And Internal Radiation On Fibrous Ablative Materials, Raghava Sai Chaitanya Davuluri

Theses and Dissertations--Mechanical Engineering

Space vehicles are equipped with Thermal Protection Systems (TPS) that encounter high heat rates and protect the payload while entering a planetary atmosphere. For most missions that interest NASA, ablative materials are used as TPS. These materials undergo several mass and energy transfer mechanisms to absorb intense heat. The size and construction of the TPS are based on the composition of the planetary atmosphere and the impact of various ablative mechanisms on the flow field and the material. Therefore, it is essential to quantify the rates of different ablative phenomena to model TPS accurately. In this work, the impact of …

Multiscale Modeling Of Cardiac Growth And Baroreflex Control, Hossein Sharifi

Theses and Dissertations--Mechanical Engineering

The heart functions within a complex system that adapts its function to any alteration in loading via several mechanisms. For example, the baroreflex is a short-term feedback loop that modulates the heart's function on a beat-to-beat basis to control arterial pressure. On the other hand, cardiac growth is a long-term adaptive response that occurs over weeks or months in response to changes in left ventricular loading. Understanding the mechanisms that drive ventricular growth and biological remodeling is critical to improving patient care. Multiscale models of the cardiovascular system have emerged as effective tools for investigating G&R, offering the ability to …

Utilization Of Uncrewed Aircraft Systems Towards Investigating The Structure Of The Atmospheric Surface Layer, Loiy Al-Ghussain

Theses and Dissertations--Mechanical Engineering

This study presents two approaches to investigate the surface-layer structure during the morning transition using uncrewed aircraft systems. The first approach employs three uncrewed aircraft systems- each equipped with a single multi-hole probe- simultaneously measuring horizontal transects were partnered with a fourth measuring vertical profiles during two consecutive mornings as part of the 2017 Collaboration Leading Operational Unmanned Aerial System Development for Meteorology and Atmospheric Physics (CLOUDMAP) measurement campaign near Stillwater, Oklahoma, U.S.A. Data were analyzed to extract time-dependent single-point statistics of kinematic and thermodynamic variables from the uncrewed aircraft systems. In addition, an approach is presented by which multi-point …

The Toyota Production System (Tps) In A Non-Traditional Manufacturing Environment: The Role Of Standardization In The Fast-Food Industry, Kevin Mccracken

Theses and Dissertations--Manufacturing Systems Engineering

The Toyota Production System (TPS), also known as Lean Manufacturing (LM), was founded in the automotive industry and has contributed to Toyota’s decades of success. This has brought much attention to TPS and how this system may be implemented in other industries. Focusing on the TPS foundational element of standardization, this study examines the impact of target cycle time (TCT) on process fluctuation in a fast-food environment. In order to observe the effects of TCT, team members within 3 production lines were timed. Times were measured before and after the addition of a TCT to the Standardized Work (STW) in …

Energy And Economic Modeling Of Stillage Dewatering Processes In Kentucky Bourbon Distilleries, William Brennan

Theses and Dissertations--Mechanical Engineering

Stillage is a byproduct of alcohol distillation and must be managed in all distilleries to sustain operations. In the United States, fuel ethanol plants typically convert all stillage into Dried Distillers’ Grains with Solubles (DDGS). This process and its variations are well known. Typical stillage management approaches are not well known, however, for the Kentucky bourbon industry. A survey of stillage management approaches in operational bourbon distilleries was conducted. Process modeling was performed to evaluate the energy and economic considerations of the available stillage dewatering methods for a 7 Million Original Proof Gallon (MMOPG) distillery. Monte Carlo simulations were performed …

Quantitative Methods For Total Lifecycle Risk Likelihood And Impact Assessment In Sustainable Product Design Decision Making, Christian Enyoghasi

Theses and Dissertations--Mechanical Engineering

Sustainable products promise significant economic, environmental, and societal benefits. Numerous methods are available for use during the new product development process to identify alternate product designs that optimize sustainability performance. Once any such design is selected and the product is launched, many uncertainties are likely to affect its performance over the total lifecycle. Such uncertainties give rise to risks that can influence the overall product sustainability performance. However, comprehensive quantitative methods to evaluate the likelihood or the impact of different risks to enable sustainable product design decision making are lacking.

This research aims to address this gap by developing a …

Radiative Conductivity Estimation Using Direct Approach For Fibrous Materials, Mohammad Khaleel

Theses and Dissertations--Mechanical Engineering

During planetary entry, space vehicles encounter high loads of thermal energy which requires a thermal protection system. Ablative thermal protection systems are usually made out of fibrous materials that exhibit internal radiation. In order to model the internal radiation response of a thermal protection system one should obtain proper radiative properties as well as thermal properties. The objective of this work is to provide a method that solves for the solid/gas thermal conductivity. Which can be used in coupled detailed radiative analysis.

Keywords: radiative conductivity, fibrous materials, radiative transfer, thermal protection system, P1 approximation, Finite Volume method.

Modeling Human Control Behavior In Command-Following Tasks, Sajad Koushkbaghi

Theses and Dissertations--Mechanical Engineering

Humans interact with a variety of complex dynamic systems on a daily basis. However, they are often the lesser understood component of human-in-the-loop (HITL) systems. In this dissertation, we present the results of two HITL experiments to investigate the control strategies that humans use when performing command-following tasks. The first experiment is designed to investigate the control strategies that humans use to interact with nonlinear dynamic systems. Two groups of human subjects interact with a dynamic system and perform a command-following task. One group interacts with a linear time-invariant (LTI) dynamic system and the other group interacts with a Wiener …

In-Situ Characterization Of Surface Quality In Γ-Tial Aerospace Alloy Machining, David Adeniji

Theses and Dissertations--Mechanical Engineering

The functional performance of critical aerospace components such as low-pressure turbine blades is highly dependent on both the material property and machining induced surface integrity. Many resources have been invested in developing novel metallic, ceramic, and composite materials, such as gamma-titanium aluminide (γ-TiAl), capable of improved product and process performance. However, while γ-TiAl is known for its excellent performance in high-temperature operating environments, it lacks the manufacturing science necessary to process them efficiently under manufacturing-specific thermomechanical regimes. Current finish machining efforts have resulted in poor surface integrity of the machined component with defects such as surface cracks, …

Formation Control With Bounded Controls And Collision Avoidance: Theory And Application To Quadrotor Unmanned Air Vehicles, Zachary S. Lippay

Theses and Dissertations--Mechanical Engineering

This dissertation presents new results on multi-agent formation control and applies the new control algorithms to quadrotor unmanned air vehicles. First, this dissertation presents a formation control algorithm for double-integrator agents, where the formation is time varying and the agents’ controls satisfy a priori bounds (e.g., the controls accommodate actuator saturation). The main analytic results provide sufficient conditions such that all agents converge to the desired time-varying relative positions with one another and the leader, and have a priori bounded controls (if applicable). We also present results from rotorcraft experiments that demonstrate the algorithm with time-varying formations and bounded controls. …

Numerical And Scaling Study On Application Of Inkjet Technology To Automotive Coating, Masoud Arabghahestani Dr.

Theses and Dissertations--Mechanical Engineering

A thorough literature review identified lack of precision control over quality of droplets generated by the currently available industrial sprayers and a growing need for higher quality droplets in the coating industry. Particularly, lack of knowledge and understanding in continuous inkjets (CIJ) and drop-on-demand (DOD) technologies is identified as significant. Motivated by these needs, this dissertation is dedicated to computational fluid dynamics (CFD) and scaling studies to improve existing inkjet technologies and develop new designs of efficient coating with single and/or multiple piezoelectric sensors to produce on-demand droplets. This dissertation study aims at developing a new DOD type coating technology, …

In-Situ Characterization Of Burr Formation In Finish Machining Of Inconel 718, Hamzah M. Zannoun

Theses and Dissertations--Mechanical Engineering

One of the undesirable byproducts that occur during the machining process is the development of burrs, which are defined as rough excess material that forms around the geometric discontinuities of a part. Burrs are especially problematic because they have negative impacts across the triple bottom line: economic, environmental, societal. For one, they are expensive to remove because the deburring process is entirely manual and requires skill. Further, burr material is typically discarded which is adding to the already mounting waste generated from machining such as in coolant and chip disposal. Lastly, there are many societal implications, such as operator injury …

Peridynamic Material Correspondence Models: Bond-Associated And Higher-Order Formulations, Wailam Chan

Theses and Dissertations--Mechanical Engineering

Peridynamic material correspondence model is able to incorporate material constitutive models directly from classical continuum mechanics theory. However, conventional correspondence model faces two major technical issues for its application to practical problems. The first is the material instability, which results severe oscillations in the predicted displacement fields. The second issue is the length scale effects of materials mechanical behavior at low length scales. This research journey mainly consists of three stages. The first two stages of this research journey focus on the development of the bond-associated peridynamic material correspondence model to inherently remove the material instability. The last stage focuses …

Formation Control With Collision Avoidance For Fixed-Wing Unmanned Air Vehicles With Speed Constraints, Christopher Heintz

Theses and Dissertations--Mechanical Engineering

Advances in the miniaturization of powerful electronic components and motors, the democratization of global navigation satellite systems (GNSS), and improvements in the performance, safety, and cost in lithium batteries has led to the proliferation of small and relatively inexpensive unmanned aerial vehicles (UAVs). Many of these UAVs are of the multi-rotor design, however, fixed-wing designs are often more efficient than rotary-wing aircraft, leading to a reduction in the power required for a UAV of a given mass to stay airborne. Autonomous cooperation between multiple UAVs would enable them to complete objectives that would be difficult or impossible for a single …

Laptop Recycling Case Study: Estimating The Contained Value And Value Recovery Process Feasibility Of End-Of-Life Consumer Electronics, Zebulon Hart

Theses and Dissertations--Mining Engineering

Work has been done to establish, through the development and use of novel assay techniques and analysis metrics, the contained value of a sampling of laptop computers (as an analog for myriad e-waste sources). This work has conceptualized e-waste as an alternative to geologic-origin complex metallic ores and has likewise evaluated the feasibility of value recovery from e-waste sources in a similar manner to an ore. The application of conventional and novel mineral separation techniques to e-waste recycling processes has been evaluated and positive results are demonstrated. Further, this work has demonstrated the ability to identify the presence of base …

A Decoupled Engineering Methodology For Accurate Prediction Of Ablative Surface Boundary Conditions In Thermal Protection Systems, Justin Cooper

Theses and Dissertations--Mechanical Engineering

The main objective of the present work is to demonstrate a method for prediction of aerothermal environments in the engineering design of hypersonic vehicles as an alternative to the current heritage method. Flat plate and stagnation point boundary layer theory require multiple assumptions to establish the current engineering paradigm. Chief among these assumptions is the similarity between mass and heat transfer. Origins of these assumptions are demonstrated and their relationship to conservative engineering design is analyzed, as well as conditions where they possibly break down. An alternative approach for assessing aerothermal environments from the fluid domain is presented, which permits …

The Effects Of Reference-Command Preview On The Strategies That Humans Use In Command-Following Tasks, Amelia J. S. Sheffler

Theses and Dissertations--Mechanical Engineering

This thesis presents results from an experiment in which 22 human subjects each interact with a dynamic system 40 times over a one-week period. For each interaction, a subject performs a command-following task, where the reference command is the same for all 22 subjects but different on each trial. The subjects are divided into 2 groups of 11 subjects. One group performs the command-following task without reference-command preview. The other group is provided with 1-s preview of the reference command. The experimental results are used to examine the effects of reference-command preview. For the group with 1-s reference-command preview, the …

Small-Satellite Attitude Control Using Sinusoidal Actuator Motion: Experiments On The International Space Station, K. Ryan Lush

Theses and Dissertations--Mechanical Engineering

In this work, we design, build, and test two 1.25U CubeSats. These small satellites were deployed on the International Space Station to perform attitude control experiments in microgravity. These CubeSats use an oscillating-mass actuation system for attitude control as opposed to traditional flywheels. Each CubeSat uses 3 pairs of servomotors to oscillate masses about 3 orthogonal axes. The servomotors have strict rotational stroke limits. Thus, they cannot spin continually. To oscillate each pair of masses, the angle of each servomotor is commanded using signals that are continuous and piecewise sinusoidal with amplitudes that do not violate the servomotor stroke constraints. …

Experimental Comparison Of Two Sampled-Data Adaptive Control Algorithms For Rejecting Sinusoidal Disturbances, William Grayson Woods

Theses and Dissertations--Mechanical Engineering

We review two adaptive control algorithms that address the problem of rejecting sinusoids with known frequencies that act on an unknown asymptotically stable linear time-invariant system. We present modifications to the algorithms that address the problems of sensor noise and actuator saturation. We demonstrate the effectiveness of the algorithms and compare the performance of the algorithms via numerical simulation and experimental testing.

A Theoretical Study On Integration And Optimization Of Gas Turbine Problems With Solar Energy System, Ahmad M. Abubaker

Theses and Dissertations--Mechanical Engineering

Gas Turbine (GT) power plants suffer from sensitivity to ambient-air temperatures, high fuel consumption, and a high amount of waste heat dumped into the ambient. Various solutions were proposed to solve these drawbacks, which could simultaneously solve at most two problems, usually at the expense of the third. For instance, inlet-air cooling can reduce ambient-air temperatures but will result in increased fuel consumption. However, in this work, a novel cascaded system was integrated into a combined cycle, capable of simultaneously solving all the aforementioned GT drawbacks. Parabolic trough collectors were used to preheat the air at the combustion chamber inlet …