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Full-Text Articles in Mechanical Engineering

Mid-Wave Infrared Imaging Of Supersonic Combustor Exhaust Flow, Nathan Childs Jan 2025

Mid-Wave Infrared Imaging Of Supersonic Combustor Exhaust Flow, Nathan Childs

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A study was completed on the application of mid-wave infrared (MW-IR) imaging for diagnostics in supersonic combustion exhaust flows, with the objective of enhancing optical access and measurement accuracy. Other optical based techniques of thermography require complicated setups and analysis to determine the temperature of a flow with high accuracy, where MW-IR is a more simplistic "point and shoot" technique. The simplicity of MW-IR comes with the trade off of gaining simplicity but adding uncertainty into the measurements. The MW-IR camera was positioned to view the exhaust of the combustor to provide an unobstructed view of the flow, addressing limitations …


Laminar Separation Control Of An Eppler 387 Airfoil, Vincent R. Sheeler Jan 2025

Laminar Separation Control Of An Eppler 387 Airfoil, Vincent R. Sheeler

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A variety of aerodynamic devices operate at low Reynolds number conditions, such as unmanned aerial vehicles and low-pressure turbines in gas turbine engines. At low Reynolds numbers, many airfoils experience laminar boundary layer separation as the fow lacks the energy to overcome the adverse pressure gradient. Researchers have documented a variety of methods which can suppress laminar separation, and now focus on ways to reduce energy requirements to provide efective fow control. Aspects of fow control strategy such as actuator location and pulsing at frequencies which exploit natural instabilities in the fow can reduce energy requirements. In a study by …


Optical Study Of Small Jet Engine Combustion Ignition, Bryce Anthony Ullman Jan 2025

Optical Study Of Small Jet Engine Combustion Ignition, Bryce Anthony Ullman

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Improving the ignition reliability in small-scale gas turbine engines is critical for safety aspects of auxiliary power units (APUs). To better understand the ignition characteristics of these small-scale combustors, an optically accessible combustor is designed and tested. The combustor accommodates twelve prevaporizer tubes (PVTs) in accordance with the commercial-off-the-shelf (COTS) rendition and allows for interchangeable materials (quartz and Inconel) and igniter positions. Another notable design feature introduces a quartz outer combustor liner to allow visualization into key regions of the combustor. The study aims to replicate a COTS ignition sequence using glow plug igniters and examine the effects of different …


Computational Analysis Of A Hafnium-Titanium Alloy Mechanical Properties From First Principles, Abdul Mughni Jan 2025

Computational Analysis Of A Hafnium-Titanium Alloy Mechanical Properties From First Principles, Abdul Mughni

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Hafnium and titanium, along with zirconium, are refractory metals with unique properties suitable for extreme-environment applications. Utilizing alloys based on these elements can provide suitable materials with engineered properties. Understanding their mechanical properties is necessary to determine appropriate applications. This thesis research aims at employing quantum-based atomistic simulations to estimate mechanical properties of pristine hafnium, titanium and an alloy based on these elements. The results are compared to available experimental data and the corresponding implications are explored.


Data-Driven Prediction Of Temperature Distribution In Multi-Laser Powder Bed Fusion Using Convolutional Neural Networks, Majid Dousti Jan 2025

Data-Driven Prediction Of Temperature Distribution In Multi-Laser Powder Bed Fusion Using Convolutional Neural Networks, Majid Dousti

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Additive Manufacturing (AM), particularly Laser Powder Bed Fusion (L-PBF), has gained significant traction in fabricating complex, high-performance metallic components. However, the inherent complexity and computational cost of high-fidelity simulations pose challenges for real-time monitoring and optimization of multi-laser powder bed fusion processes. This study proposes a data-driven surrogate modeling approach using a deep learning architecture to efficiently and accurately predict three-dimensional temperature distributions during ML-PBF. A 3D convolutional neural network (CNN) model, named Decoder-CNN, is developed and trained on a dataset of simulated thermal fields corresponding to various process configurations, including different laser power, scanning speed, and beam arrangements. The …


Evaluating Geometric Accuracy In 3d Printing (3dp) Comparative Study Of Different 3dp Processes Using Cmm And Vision Measurement Tools, Alexander Adams Jan 2025

Evaluating Geometric Accuracy In 3d Printing (3dp) Comparative Study Of Different 3dp Processes Using Cmm And Vision Measurement Tools, Alexander Adams

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This study investigates how various additive manufacturing (AM) technologies and parameters influence part quality by fabricating three uniquely designed artefacts. Artefact 1 is a rectangular block with stepped arches, thin and solid extruded features, and holes of varying shapes and sizes. Artefact 2 consists of a base plate with angled overhangs from 15 to 90 degrees. Artefact 3 includes a tall cylinder, a five-step cylinder, and two half arches of different scales. Each artefact was printed ten times using: metal PBF (Inconel 718), nylon PBF (Nylon 12), Vat Polymerization (GRY photopolymer), and material extrusion (nylon carbon fiber). Dimensional analysis was …


Using Unsupervised Machine Learning To Experimentally Categorize Separation On Low-Pressure Turbine Blades, Aaron B. Suter Jan 2025

Using Unsupervised Machine Learning To Experimentally Categorize Separation On Low-Pressure Turbine Blades, Aaron B. Suter

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Laminar boundary layer separation can significantly degrade the efficiency of Low-Pressure Turbine (LPT) blades. While active flow control (AFC) methods can mitigate these losses, energy-efficient implementation requires activating the system only when performance decreases. This study validates an unsupervised machine learning framework that utilizes sparse, discrete surface-pressure measurements to distinguish between high and low aerodynamic loss states. A fuzzy c-means (FCM) clustering model was trained on limited pressure data obtained in a low-speed linear cascade across Reynolds numbers from 30,000 to 160,000 and used to categorize the flow regime in real time. At Re = 40,000, vortex generator jet (VGJ) …


Utilizing Optimization Tools For Passive Flow Control Passage Loss Reduction In Low-Pressure Turbines, Bryant Robert Duane Burton Jan 2025

Utilizing Optimization Tools For Passive Flow Control Passage Loss Reduction In Low-Pressure Turbines, Bryant Robert Duane Burton

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Low-pressure turbines (LPTs) play a crucial role in fuel efficiency and thrust generation of aero-engines. Traditional LPT designs, however, involve multiple stages and numerous blades, resulting in increased weight and manufacturing costs. The challenge of modern- day researchers is to reduce the weight and cost but maintain the high efficiency of LPTs. To address this, one approach is to increase the aerodynamic loading of individual blades, reducing the blade count. However, this can lead to increased secondary losses caused by flow separation, particularly in the endwall regions. This research focuses on optimizing the blade profile at the junction with the …


Quantification Of Porosity In Hfb2–20%Sic Using Convolutional Neural Networks, Cameron J. Floyd Jan 2025

Quantification Of Porosity In Hfb2–20%Sic Using Convolutional Neural Networks, Cameron J. Floyd

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Ultra-high-temperature ceramics, commonly used in aerospace applications, operate in high-temperature oxidizing environments where a surface scale forms and regulates oxy gen access. For hafnium diboride–silicon carbide (HfB2–SiC), that scale consists of a borosilicate glass layer over a porous HfO2 skeleton. Oxygen transport through this poros ity governs the kinetics of mechanistic models, requiring reproducible inputs for accurate pore fraction (PF), pore-size distributions, and ultimately tortuosity. This thesis replaces rule-based SEM thresholding with a convolutional neural network that segments pores and predicts the pore-radius distribution for transport models. The resulting calibrated porosity maps and size distributions transfer within the acquisition domain …


Effect Of Build Orientation And Environmental Conditions On Mechanical And Geometric Properties Of Polymeric Parts Fabricated By The Powder Bed Fusion Process, Adedamola O. Adeyemi Jan 2025

Effect Of Build Orientation And Environmental Conditions On Mechanical And Geometric Properties Of Polymeric Parts Fabricated By The Powder Bed Fusion Process, Adedamola O. Adeyemi

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Polyamide-12 (aka PA12) is a synthetic thermoplastic polymer that has been used in various applications, including the electronic and electrical, oil and gas industrial manufacturing and automotive industry. There are several ways to manufacture parts with PA12 and PA12 based composites. Injection molding, a traditional manufacturing process, has been the standard manufacturing route for polymers for a long time. Recently, however, additive manufacturing (AM) processes, such as powder bed fusion (PBF) and material extrusion (ME) have been introduced. PBF is a manufacturing process characterized by the selective sintering of successive layers of powdered material. It is the most effective AM …


Investigating The Impact Of Stress And Irradiation Flux On Latent Track Formation In Tio2 Under Swift Heavy Ion Irradiation: A Phase Field Study, Ebrahim Ebrahimi Jan 2024

Investigating The Impact Of Stress And Irradiation Flux On Latent Track Formation In Tio2 Under Swift Heavy Ion Irradiation: A Phase Field Study, Ebrahim Ebrahimi

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Swift Heavy Ions (SHI) irradiation, characterized by high kinetic energy ions, induces significant material/structural modification, e.g., latent track. However, the intricate interaction among various physics, i.e., mechanical stress, phase transition, and heat transfer, has been ignored in the continuum-based approaches in favor of simplicity. Here, we developed a two-dimensional coupled phase-field inelastic-thermal spike (PF-iTS) model to investigate the effect of thermal crosstalk, elastic energy, and irradiation flux on latent track formation. A particular focus is placed on investigating the influence of internal mechanical stress on latent track formation. Simulation results reveal a shift in critical stopping energy and a reduction …


Architectural Optimization Of Emulator Embedded Neural Networks For Aerospace Vehicle Design, James L. Schmitz Ii Jan 2024

Architectural Optimization Of Emulator Embedded Neural Networks For Aerospace Vehicle Design, James L. Schmitz Ii

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An approach for the architecture optimization of emulator embedded neural networks is proposed. While the emulator embedded neural network has been shown to provide accurate predictions with suitable emulators, there is still a challenge regarding how to select the optimal hyperparameters of network architectures, such as, the number of neurons, layers, types of activation functions, etc. The selection of hyperparameters greatly affects the performance of the neural network model training both in terms of accuracy and efficiency. To address this challenge, this study proposes an algorithm that tests a range of hyperparameters and selects the best performing set. The algorithm …


A Pade-Eno Flux Reconstruction For High-Speed Flows, Blake Martin Jan 2024

A Pade-Eno Flux Reconstruction For High-Speed Flows, Blake Martin

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The development of high order numerical schemes has been instrumental in advancing computational fluid dynamics (CFD), particularly for applications requiring high resolution of discontinuities and complex flow phenomena prevalent in high-speed flows. This thesis introduces the Pade-ENO scheme, a high-order method that integrates Essentially Non-Oscillatory (ENO) techniques with compact Pade stencils to achieve superior accuracy, up to 7th order, while maintaining stability in harsh environments. The scheme’s performance is evaluated through benchmark tests, including the advection equation, Burgers’ equation, and the Euler equations. For high Mach number flows, such as the sod shock tube the Pade-ENO method demonstrates its ability …


Void Fraction And Quality Correlation Analysis Using The Separated Flow Model For Pulsed-Power Heat Loads, Zachary Joseph Carner Jan 2024

Void Fraction And Quality Correlation Analysis Using The Separated Flow Model For Pulsed-Power Heat Loads, Zachary Joseph Carner

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Aircraft platforms are continually upgraded with increasingly high quantities of high-powered electronics. As such, efficient thermal management systems are crucially important to overcome system instabilities and support pulsed power profiles. To create effective thermal control systems, it is imperative to thoroughly examine and account for a variety of potential system behaviors caused by transient changes in the flow regime. If left unconstrained, these changes will create thermal instabilities, which can severely damage electronics and hurt the overall reliability of the aircraft. These instabilities can be described by both void fraction and quality. Electrical Capacitance Tomography (ECT) allows for the collection …


Mechanical Reliability Of Aerosol Jet Printed Sensors And Interconnects, Lemuel A. Duncan Jan 2024

Mechanical Reliability Of Aerosol Jet Printed Sensors And Interconnects, Lemuel A. Duncan

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Heterogeneous integration (HI) is currently being investigated to maintain the pace of technological progress in the electronics industry. With the recent acceleration witnessed in additive manufacturing (AM) technology, interest has been expressed in introducing aerosol jet (AJ) printing to the fabrication process for sensors and electronic packages. Integrating AM technology in these areas promises design flexibility and minimal material waste. Three AJ printed applications investigated in this work include strain sensors, electrical interconnects, and metal embedded chip assemblies. Before moving forward with the use of AJ printing in these applications, it is necessary to evaluate their performance under standard mechanical …


Investigation Of Spalart-Allmaras Turbulence Model For Vortex Flows, Abigail Rayna Kerestes Jan 2024

Investigation Of Spalart-Allmaras Turbulence Model For Vortex Flows, Abigail Rayna Kerestes

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Conventional turbulence models often predict behaviors opposite as to what is observed in flows subject to rotation. In this type of flow scenario, rotation typically induces turbulence suppression. To address this limitation, a modification to the Spalart Allmaras Model with Rotation Correction (SA-R) was proposed to enhance the original Spalart Allmaras Model’s sensitivity to rotation and curvature. To test the validity and accuracy of this modification, two cases were investigated. The first case involved an axisymmetric rotating pipe. A Reynolds Number of 37,000 was implemented and the initial and boundary conditions established by Zaets et. al. were utilized. Initially non-rotating, …


Experimental Validation Of Two Highly Loaded Low Pressure Turbine Blades At High Speed Low Reynolds Number Conditions, Ryan Sauder Jan 2024

Experimental Validation Of Two Highly Loaded Low Pressure Turbine Blades At High Speed Low Reynolds Number Conditions, Ryan Sauder

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In the constant search for more efficient engines, one approach to gain performance is to reduce the weight of the low pressure turbine (LPT) module. This module can account for up to 30% of the total engine weight [1], and a reduction in LPT weight results in clear gains to engine performance and a reduction in engine cost. High lift airfoils accomplish this weight reduction by each blade extracting a larger amount of work from the flow and thus requiring fewer blades to drive the compressor when compared to conventional blades. However, high lift LPT blades, quantified by a high …


Additively Manufactured Polymeric Surface-Based Lattice Structures For Vibration Attenuation, Imabin Kelvin Ekpelu Jan 2023

Additively Manufactured Polymeric Surface-Based Lattice Structures For Vibration Attenuation, Imabin Kelvin Ekpelu

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The focus of this study was to select triply periodic minimal surface (TPMS) structures made of 3D-printed polymers. The primary variables in this study were: TPMS shape, lattice volume ratio, and lattice material. Vibration absorption was characterized by damping ratio via transmissibility at the system’s natural frequency. The vibration testing was performed using an electro-dynamic shaker, a known mass, an input/control accelerometer, and an output/response accelerometer. The 3D-printed absorber/lattice was mounted to the shaker baseplate and a mass will be mounted on top of the absorber. One accelerometer will be mounted to the shaker baseplate and the other will be …


Effects Of Elastic Anisotropy On Residual Stress Measurements Performed Using The Hole-Drilling Technique, Joshua T. Ward Jan 2023

Effects Of Elastic Anisotropy On Residual Stress Measurements Performed Using The Hole-Drilling Technique, Joshua T. Ward

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In the present work, the variation in through-thickness residual stress profiles driven by elastic anisotropy is investigated using the incremental hole-drilling method. The standardized hole-drilling technique allows for the calculation of in-plane stresses based on measured surface strains, however, these calculations assume elastic isotropy. The assumption of elastic isotropy allows for the material constants to be reduced down to two values, however, this assumption is invalid for many materials used in aerospace design. These materials are often times elastically anisotropic, which leads to inaccuracy and uncertainty in measured stress profiles. An interference fit ring and plug sample was designed, using …


Effect Of Size And Shape Parameters On Microstructure Of Additively Manufactured Inconel 718, Showmik Ahsan Jan 2023

Effect Of Size And Shape Parameters On Microstructure Of Additively Manufactured Inconel 718, Showmik Ahsan

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Additive Manufacturing (AM) methods are promising in applications where complex part geometries, exotic materials and small lot sizes are required. Aerospace manufacturing stands to use AM methods extensively in the future, and frequently requires temperature- and corrosion-resistant alloy materials such as Inconel 718. However, the microstructural evolution of Inconel 718 during additive manufacturing is poorly understood and depends on part size and shape. We studied the microstructure of Inconel 718 parts manufactured by Laser Powder Bed Fusion in order to further elucidate these dependencies. Microstructural analysis, SEM imaging, EBSD scans and Microhardness testing were performed.


Rankine Cycle Investigation On Meeting Power And Thermal Requirements Of High-Speed Aircraft, Jacob J. Spark Jan 2023

Rankine Cycle Investigation On Meeting Power And Thermal Requirements Of High-Speed Aircraft, Jacob J. Spark

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This work is investigating a dual mode Rankine cycle for aircraft applications, specifically meeting vehicle thermal and power requirements. This multiconfigurational approach allows the Thermal Management System (TMS) to be controlled based on aircraft needs. In this design, waste heat is removed from critical areas of the aircraft (e.g., propulsion, structure, subsystems) using the fuel as a heat sink. Hot fuel is then forced through a heat exchanger actively boiling water. The vapor byproduct is fed to a turbine coupled to a generator, providing power. The low-pressure steam is then condensed using cold fuel drawn from its tank; however, when …


Development Of Improved Cfd Tools For The Optimization Of A Scramjet Engine, Francis A. Centlivre Jan 2022

Development Of Improved Cfd Tools For The Optimization Of A Scramjet Engine, Francis A. Centlivre

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In the present work, a plugin has been developed for use with the DoD HPCMP CREATE-AV Kestrel multi-physics solver that adds volumetric source terms to the energy equation. These source terms model the heat released due to combustion, but are much more computationally efficient than a full chemistry model. A thrust-based optimization study was then carried out under the control of Sandia National Laboratories' Dakota toolkit. Dakota was allowed to control the amount of heat added to three regions of the scramjet combustor. The plugin was then extended to consider ignition delay time. By comparing ignition delay time to dwell …


Design Of A Surrogate Hypersonic Inlet For The Hifire-6 Configuration, Joseph W. Mileski Jan 2022

Design Of A Surrogate Hypersonic Inlet For The Hifire-6 Configuration, Joseph W. Mileski

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Shock wave-boundary layer interactions can significantly impact the operability of high-speed inlets by inducing flow separation. This flow separation is difficult to visualize in three-dimensional, inward-turning inlets because of the curved surfaces that form their internal flow paths. To remedy this challenge, a surrogate test article was created. Using the results from a previously completed Computational Fluid Dynamic (CFD) analysis of the HIFiRE-6, a surrogate inlet with a rectangular isolator section was streamline-traced, allowing for the use of schlieren imagery to capture the separation bubble. This thesis discusses the process of developing the test article. Experimental results from a planned …


Demonstration Of High-Temperature Operation Of Beta-Gallium Oxide (Β-Ga2o3) Metal-Oxide-Semiconductor Field Effect Transistors (Mosfet) With Electrostatic Model In Comsol, Nicholas Paul Sepelak Jan 2022

Demonstration Of High-Temperature Operation Of Beta-Gallium Oxide (Β-Ga2o3) Metal-Oxide-Semiconductor Field Effect Transistors (Mosfet) With Electrostatic Model In Comsol, Nicholas Paul Sepelak

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β-Ga2O3 is a robust semiconductor material set with a large band gap of ~4.8 eV, low intrinsic carrier concentration, and high melting point that offers a stable platform for operating electronic devices at high temperatures and extreme environments. The first half of this thesis will cover the fabrication of a fixture and packaging to test electronic components at high temperatures. Then it will highlight the characterization of β-Ga2O3 field effect transistors from room temperature (RT) up to 500 °C. The devices, fabricated with Ni/Au and Al2O3 gate metal-oxide-semiconductor (MOS), demonstrate stable operation up to 500 oC. The tested device shows …


Simulation Of Residual Stress Generation In Additive Manufacturing Of Complex Lattice Geometries, Katie Sue Bruggeman Jan 2022

Simulation Of Residual Stress Generation In Additive Manufacturing Of Complex Lattice Geometries, Katie Sue Bruggeman

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Residual stresses developed during additive manufacturing (AM) can influence the mechanical performance of structural components in their intended applications. In this study, thermomechanical residual stress simulations of the laser powder bed fusion (LPBF) process are conducted for both simplified (plate and cube-shaped) geometries as well as five complex lattice geometries fabricated with Inconel 718. These simulations are conducted with the commercial software package Simufact Additive©, which uses a non-linear finite element analysis and layer-by-layer averaging approach in determining residual stresses. To verify the efficacy of the Simufact Additive© simulations, numerical results for the plate and cube-shape geometries are analyzed for …


Hypersonic Conceptual Design Tool Comparison, James G. Wnek Jan 2022

Hypersonic Conceptual Design Tool Comparison, James G. Wnek

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The many iterations needed to explore a design space in the conceptual design process preclude the use of time-consuming RANS CFD for all but a few flight conditions. This research focuses on identifying the level of fidelity needed to adequately predict the aerothermodynamic characteristics of hypersonic vehicles. Three tools with differing levels of fidelity – CBAERO, Cart3D, and Kestrel – were used to analyze the Generic Hypersonic Vehicle (GHV) at the design condition of Mach 5.85 and an off-design condition of Mach 4.5. The results are representative of the different design tools but are not definitive due to the mesh …


Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith Jan 2022

Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith

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Repairing airfoil blades is necessary to extend the life of turbine engines. Directed energy deposition (DED) additive manufacturing (AM) provides the ability to add material at a specific location on an existing component. In this work, AM repairs on Ti-6Al-4V airfoil blades were analyzed to determine what effect the repair will have on the blade performance in high cycle vibration fatigue testing. Targeted sections were cut out of airfoil blades near high stress locations and repaired using DED. To understand the defects that arose with this type of repair, computed tomography imaging was used to quantify the defects from the …


Molecular Dynamics Simulation Study Of A Polymer Droplet Transport Over An Array Of Spherical Nanoparticles, Anish Thomas Jan 2022

Molecular Dynamics Simulation Study Of A Polymer Droplet Transport Over An Array Of Spherical Nanoparticles, Anish Thomas

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This study uses molecular dynamics simulations to evaluate the dynamic behavior of a partially wetting polymer droplet driven over a nanostructured interface. We consider the bead-spring model to represent a polymeric liquid that partially wets a rough surface composed of a periodic array of spherical particles. Results show that at sufficiently small values of external force, the droplet remains pinned at the particle's surface, whereas above the threshold its motion consists of alternating periods of pinning and rapid displacements between neighboring particles. The latter process involves large periodic variation of the advancing and receding contact angles due to the attachment …


Printing, Characterization, And Mechanical Testing Of Additively Manufactured Refractory Metal Alloys, Brianna M. Sexton Jan 2022

Printing, Characterization, And Mechanical Testing Of Additively Manufactured Refractory Metal Alloys, Brianna M. Sexton

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Refractory metal alloys in the tungsten molybdenum rhenium ternary system were additively manufactured using laser power bed fusion. Four ternary alloys with varying concentrations of tungsten, molybdenum, and rhenium were manufactured and manufactured again with an addition of 1 wt% hafnium carbide. Samples were heat treated to heal cracks, reduce porosity, and reduce inhomogeneity. Material microstructure was characterized before and after heat treatment using microscopy, energy dispersive x-ray spectroscopy, and electron backscatter diffraction mapping. Mechanical testing was conducted on both three-point bend specimens and compression specimens, resulting in maximum bending strengths of 677.86 MPa, and maximum compression 0.2% yield strengths …


A Digital Twin For Synchronized Multi-Laser Powder Bed Fusion (M-Lpbf) Additive Manufacturing, Shayna Petitjean Jan 2022

A Digital Twin For Synchronized Multi-Laser Powder Bed Fusion (M-Lpbf) Additive Manufacturing, Shayna Petitjean

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One of the technological challenges in the widespread application of additive manufacturing is the formation of undesired material microstructure and defects. Specifically, in metal additive manufacturing, the microstructural formation of columnar grains in Ti-6Al-4V is common and results in anisotropic mechanical properties and a reduction in properties such as ductility and endurance limit. This work presents the application of hexagonal and circular arrays of synchronized lasers to alter the microstructure of Ti-6Al-4V in favor of equiaxed grains. An anisotropic heat transfer model obtains the temporal/spatial temperature distribution and constructs the solidification map for various process parameters, including laser power, laser …