Mechanical Engineering Commons^™

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

Theses and Dissertations--Mechanical and Aerospace 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 …

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

Theses and Dissertations--Mechanical and Aerospace 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 …

Multiscale Modeling Of Cardiac Growth And Baroreflex Control, Hossein Sharifi

Theses and Dissertations--Mechanical and Aerospace 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 …

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

Theses and Dissertations--Mechanical and Aerospace 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 …

Machine Learning For Advancing Automation And Quality Control In Robotic Welding, Joseph Kershaw

Theses and Dissertations--Mechanical and Aerospace Engineering

Welding is a vital manufacturing process across a diverse range of industries to permanently join metallic components into needed assemblies. Though widely used and studied, the process is not fully understood due to the myriad of interconnected physics that present themselves during the welding process. Electrical, thermal, structural, and fluidic mechanics are simultaneously at work influencing one another to achieve the bonding that manufacturers desire. In addition to general manufacturing issues, such as tool wear or misalignment, micro-level changes to the material structure and composition can have cascading impacts on the final weld. This complexity makes it difficult, if not …

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

Theses and Dissertations--Mechanical and Aerospace 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 and Aerospace 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 …

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

Theses and Dissertations--Mechanical and Aerospace 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 …

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

Theses and Dissertations--Mechanical and Aerospace 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 and Aerospace 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 …

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

Theses and Dissertations--Mechanical and Aerospace 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, …

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

Theses and Dissertations--Mechanical and Aerospace 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.

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

Theses and Dissertations--Mechanical and Aerospace 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 …

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

Theses and Dissertations--Mechanical and Aerospace 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. …

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

Theses and Dissertations--Mechanical and Aerospace 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 and Aerospace 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 and Aerospace 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.

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

Theses and Dissertations--Mechanical and Aerospace 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 and Aerospace 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 and Aerospace 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 …

Shape Memory Behavior Of Nitihf Alloys Fabricated By Laser Powder Bed Fusion, Guher Pelin Toker

Theses and Dissertations--Mechanical and Aerospace Engineering

NiTiHf-based alloys have emerged as potential materials for applications requiring high transformation temperatures (> 100 °C) with high strength and work output. Currently, it is challenging to produce complex shapes of these materials with tailored shape memory properties or reduce the material waste from machining operations given the cost of these materials. Additive manufacturing via Laser Powder Bed Fusion (L-PBF) represents an attractive way to fill this gap by producing unique geometries from powder-based feedstock. In this method, process parameters such as laser power, scanning speed, hatch spacing and energy density play significant roles in controlling the mechanical behavior and …

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

Theses and Dissertations--Mechanical and Aerospace 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 …

Measurements Of Wind Turbine Wake Evolution And Trajectory During Morning Boundary Layer Transition And Under Wake Steering Conditions Via Unmanned Aerial Vehicles, Stewart Nelson

Theses and Dissertations--Mechanical and Aerospace Engineering

In July of 2019, a flight campaign was conducted using semi-autonomous Unmanned Aerial Vehicles (UAVs) at the Port Alma Kruger Energy wind farm in Ontario, Canada, to study various aspects of wind turbine wake evolution. Horizontal transects across the wakes were measured using modified fixed-wing aircraft fitted with a five-hole probe to measure the wind velocity vector. Reference boundary layer conditions were measured by an octocopter with an assortment of mounted sensors flying vertical profiles upstream of the turbines. Three experiments were conducted during the campaign, which consisted of a study on wake behavior during the morning boundary layer transition, …

Prediction Of Noise Emissions Using Panel Contribution Analysis Supplemented With Scale Modeling, Gong Cheng

Theses and Dissertations--Mechanical and Aerospace Engineering

Panel contribution analysis (PCA) can be used to predict machinery noise emissions, component contributions, and to assess the impact of sound reduction treatments. PCA is a measurement approach that is advantageous for complex machinery that is not easily modeled using conventional numerical analysis approaches. In this research, PCA is combined with scale modeling in order to speed up the necessary measurement work. Moreover, the method can be applied to much larger machinery and noise emissions can be assessed prior to locating and installing the equipment. This eliminates the necessity to use voluminous anechoic chambers.

The machinery is first discretized into …

Kinetics Of Elementary Reactions In Graphene Oxidation And Kinetics Of Oh* In Hydrogen Flames, Siamak Mahmoudi

Theses and Dissertations--Mechanical and Aerospace Engineering

Due to diverse applications of graphene, a kinetic mechanism describing rates of elementary reactions is extremely useful. To achieve that goal the elementary reactions need to be detected and their rates need to be determined. In this work the objectives are to use first-principle tools to find those reactions and analyze their paths in the context of graphene oxidation. Density functional theory (DFT) calculations provide the best approximation to the Schr\"{o}dinger equation, which is not feasible to solve analytically for large molecules like graphene. We have performed these calculations to find stable configurations (geometry optimization) and minimum energy paths between …

Balancing Trade-Offs In One-Stage Production With Processing Time Uncertainty, Jingjing You

Theses and Dissertations--Mechanical and Aerospace Engineering

Stochastic production scheduling faces three challenges, first the inconsistencies among key performance indicators (KPIs), second the trade-offs between the expected return and the risk for a portfolio of KPIs, and third the uncertainty in processing times. Based on two inconsistent KPIs of total completion time (TCT) and variance of completion times (VCT), we propose our trade-off balancing (ToB) heuristic for one-stage production scheduling. Through comprehensive case studies, we show that our ToB heuristic with preference =0.0:0.1:1.0 efficiently and effectively addresses the three challenges. Moreover, our trade-off balancing scheme can be generalized to balance a number of …

Tailoring Texture, Microstructure, And Shape Memory Behavior Of Niti Alloys Fabricated By L-Pbf-Am, Sayed Ehsan Saghaian N.E.

Theses and Dissertations--Mechanical and Aerospace Engineering

Laser Powder Bed Fusion (L-PBF) is one of the most promising Additive Manufacturing (AM) methods to fabricate near net-shape metallic materials for a wide range of applications such as patient-specific medical devices, functionally graded materials, and complex structures. NiTi shape memory alloys (SMAs) are of great interest due to a combination of unique features, such as superelasticity, shape memory effect, high ductility, work output, corrosion resistance, and biocompatibility that could be employed in many applications in automotive, aerospace, and biomedical industries. Due to the difficulties with traditional machining and forming of NiTi components, the ability to fabricate complex parts, tailor …

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

Theses and Dissertations--Mechanical and Aerospace 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 …

The Role Of Live Conifer Fuels In Crown Fires Spread, Adnan Darwish Ahmad

Theses and Dissertations--Mechanical and Aerospace Engineering

Live foliage for some tree and shrub species can support flaming fire spread at much higher moisture content than dead fuel materials. However, the role of live fuels in forest fires has been controversial in the past decades. Although ignition and spread statistical data for live and dead fuels exist in the literature, a clear understanding of the fundamental difference in the burning behavior is missing. To illuminate the role of live fuel on forest fire spreading, a laboratory ignition experiment was designed to examine the burning behavior of live Norway spruce needles. A schlieren-Infrared combined measurement apparatus was developed …

Use Of Microscale Hydrophobic Surface Features For Integration Of 3d Cell Culture Into Multi-Functional Microfluidic Devices, Soroosh Torabi

Theses and Dissertations--Mechanical and Aerospace Engineering

3D cell culture and microfluidics both represent powerful tools for replicating critical components of the cell microenvironment; however, challenges involved in integration of the two and compatibility with standard tissue culture protocols still represent a steep barrier to widespread adoption. Here we demonstrate the use of engineered surface roughness in the form of microfluidic channels to integrate 3D cell-laden hydrogels and microfluidic fluid delivery. When a liquid hydrogel precursor solution is pipetted onto a surface containing open microfluidic channels, the solid/liquid/air interface becomes pinned at sharp edges such that the hydrogel forms the “fourth wall” of the channels upon solidification. …