Aerospace Engineering Commons^™

A Panel Data Regression Model For Defense Merger And Acquisition Activity, Corey D. Mack, Clay Koschnick, Michael Brown, Jonathan D. Ritschel, Brandon M. Lucas

Faculty Publications

Excerpt: This paper examines the relationship between a prime contractor's financial health and its mergers and acquisitions (M&A) spending in the defense industry. It aims to provide models that give the United States Department of Defense (DoD) indications of future M&A activity, informing decision-makers and contributing to ensuring competitive markets that benefit the consumer.

The results show a significant relationship between efficiency and M&A spending, indicating that companies with lower efficiency tend to spend more on M&As. However, there was no significant relationship between M&A spending and a company's profitability or solvency. These results were consistent with previous research and …

Enhancing Crossflow Dynamics Through The Gas Injection From Multiple Cylinders, Sahrish B. Naqvi, Sadia Siddiqa, Maciej Matyka, Rama S. R. Gorla, Md. Mamum Molla

Faculty Publications

We investigate unsteady, two-dimensional laminar fluid flow around cylinders, focusing on understanding the impact of injecting methane gas through two diametrically opposite arcs on the cylinder in the crossflow of the second fluid. This study encompasses applications in mixing and dispersion, which are crucial in various technological and natural processes. Our analysis addresses velocity field’s contribution to the spatiotemporal distribution of transported quantities. We observed that mixing induces a transition from laminar to turbulent flow. Depending on the injected-to-crossflow velocity ratios, the wake vortices downstream of cylinder arrays separate from or connect to the injected gas. This phenomenon significantly impacts …

Ultrashort Pulsed Laser Treatment Is Effective At Sterilizing Metal Surfaces For Planetary Protection, Kaleb Mcquillan

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

To prevent forward contamination from microbes aboard spacecraft intended for exploration of solar system bodies there is a need for effective sterilization methods. However, current techniques are both time-consuming and expensive. For example, dry heat sterilization requires removal from the assembly site and several days of treatment. Furthermore, some components such as optics and electronics are not compatible with current sterilization techniques. In this thesis, a novel femtosecond laser surface processing technique for the rapid sterilization of spacecraft hardware is reported. Femtosecond lasers produce extremely high photon fluxes (10²⁹ photons/s*cm², ~0.03 J/cm²) in extremely short …

Heat Treatment Post-Processing For The Improved Mechanical Properties Of Scalmalloy® Processed Via Directed Energy Deposition, Rachel Boillat-Newport, Sriram Praneeth Isanaka, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

As high-strength aluminum alloys present several processability issues with additive manufacturing (AM), Scalmalloy®, an Al-Mg-Sc-Zr-based alloy, has been developed. This alloy is age-hardenable, allowing it to precipitate out a strengthening precipitate phase, Al3(Sc,Zr). The manufacturer recommends a single-stage aging treatment at 325 °C for 4 h; however, the majority of the literature studies utilize a powder bed processing known as selective laser melting (SLM) over powder-fed processing directed energy deposition (DED). This study addresses the lack of information on heat treatments for DED fabrication by exploring the application of artificial aging temperatures of 300–400 °C for 2, 4, and 6 …

Tension–Compression Fatigue Of A Hybrid Polymer-Matrix/Ceramic-Matrix Composite At Elevated Temperature, Marina B. Ruggles-Wrenn, Joshua Schmidt

Faculty Publications

Fully reversed tension–compression fatigue of a hybrid material comprising polymer matrix composite (PMC) co-cured with a ceramic matrix composite (CMC) was investigated. The PMC portion had a polyimide matrix reinforced with 15 plies of carbon fibers woven in an eight-harness satin weave (8HSW). The CMC portion had three plies of a quartz-fiber 8HSW fabric in a zirconia-based ceramic matrix. The hybrid PMC/CMC was developed for use in aerospace thermal protection systems (TPS). Hence, the experimental setup aimed to simulate the TPS service environment—the CMC side was kept at 329 °C, whereas the PMC side was open to laboratory air. Compression …

Exploring Small-Scale Propellers Performance At Low Advance Ratios, Ali Akber Mollick, Sara Catto, Forrest E. Ames, Clement Tang

Mechanical Engineering Student Publications

The performance of small-scale propellers was experimentally measured at low advance ratios and Reynolds numbers. The propeller diameters range from 14 to 19 inches, with all propellers having the same pitch value of 12. Using a thrust stand situated in a low-speed open-circuit wind tunnel, the propeller thrust, torque, and angular speed were measured at various freestream velocities. The results from this study offer insights on the performance of small propellers at low advance ratios and low Reynolds numbers. Propeller performance results at these conditions tend to be limited in the literatures. At the same pitch value of 12, the …

Modeling Powder Spreadability In Powder-Based Processes Using The Discrete Element Method, Austin T. Sutton, M. Hossein Sehhat, Ming C. Leu, Joseph W. Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Powder-bed fusion (PBF) processes refer to a subset of Additive Manufacturing (AM) techniques where powder is spread on the build-plate before melting (by a laser or electron beam). While PBF processes are attractive due to their ability for realizing complex structures that are either difficult or impossible to create through conventional means, the parts fabricated with these techniques can exhibit defects such as pores, inclusions, and excessive surface roughness. To minimize these defects, much research has been dedicated towards process maturation by optimizing laser or electron beam parameters. However, these developmental efforts typically do not address the recoating process where …

A Study Of Directionality Effects In Three-Beam Coaxial Titanium Wire-Based Laser Metal Deposition, Remy Mathenia, Braden Mclain, Todd Sparks, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Coaxial wire-based laser metal deposition is a versatile and efficient additive process that can achieve a high deposition rate in the manufacturing of complex structures. In this paper, a three-beam coaxial wire system is studied, with particular attention given to the effects of the deposition direction and laser beam orientation on the resulting bead geometry symmetry. With the three-beam laser delivery, the laser spot pattern is not always symmetric with respect to the deposition direction. Single titanium beads are deposited in different directions and at varying deposition rates, and the bead profile is quantitatively scored for multiple symmetry measures. Through …

Analytical And Fem Models For Thermal Analysis And Residual Stresses Using Wire Arc-Based Welding And Additive Manufacturing Of Sus304, Muhammad Arif Mahmood, Usman Tariq, Mihai Oane, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Austenitic stainless steel, also known as SUS304, has a wide industrial application. The resultant residual stresses and deformation due to arc welding play a critical role in an in-service SUS04 part failure. Various experimental studies have been presented to predict residual stresses and part deformation. However, these techniques are expensive and time-consuming owing to the trial-and-error approach, limiting their application to industrial applications. Based on the emergent need, this study introduces two simulation models based on analytical and FEM techniques for thermal distribution and residual stress estimation. The experimentally calibrated models results have been implemented for SUS304 multi-pass arc welding. …

Unmanned Aerial Vehicle (Uav)-Based High-Throughput Phenotyping For Maize Improvement, Eric T. Rodene

Dissertations and Doctoral Documents from University of Nebraska-Lincoln, 2023–

Modern breeding programs rely heavily on efficiently screening large numbers of genotypes for agronomic traits, such as disease resistance, drought tolerance, and yield. Identifying the genetic loci or genes associated with these traits using GWAS or functional analyses will benefit future plant breeding efforts seeking to incorporate these traits into new crop varieties, whether through conventional breeding or gene editing techniques. Unmanned aerial vehicle (UAV)-based image data has been increasingly used for this task, as it allows entire test plots to be quickly and cost-effectively phenotyped. In my research, I have developed methods to improve the accuracy of machine learning …

An Integrated Space Test Lexicon: A Taxonomy For The Integrated Test And Evaluation Of Space Systems, Stephen Tullino, Andrew Keys, Robert A. Bettinger, Amy M. Cox, David R. Jacques

Faculty Publications

The proposed Integrated Space Test Lexicon is intended to amalgamate the numerous definitions of integrated (IT or IT&E), development test (DT or DT&E), and operational test (OT or OT&E) into unified, service-wide definitions, aligned with the Space Test Enterprise Vision. Refining such definitions will help distill the core characteristics of these fundamental test types to first identify space system activities composing what is traditionally known as DT and OT, then to provide a means of how these activities fit into the IT paradigm and support space system development. In forging a common understanding of how DT and OT support space …

Infrared Phase-Change Chiral Metasurfaces With Tunable Circular Dichroism, Haotian Tang, Liliana Stan, David A. Czaplewski, Xiaodong Yang, Jie Gao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Integrating Phase-Change Materials in Meta surfaces Has Emerged as a Powerful Strategy to Realize Optical Devices with Tunable Electromagnetic Responses. Here, Phase-Change Chiral Meta surfaces based on GST-225 Material with the Designed Trapezoid-Shaped Resonators Are Demonstrated to Achieve Tunable Circular Dichroism (CD) Responses in the Infrared Regime. the Asymmetric Trapezoid-Shaped Resonators Are Designed to Support Two Chiral Plasmonic Resonances with OppositeCDresponses for Realizing SwitchableCDbetween Negative and Positive Values using the GST Phase Change from Amorphous to Crystalline. the Electromagnetic Field Distributions of the Chiral Plasmonic Resonant Modes Are Analyzed to Understand the Chiroptical Responses of the Meta surface. Furthermore, the …

Transfer-Learning-Enhanced Regression Generative Adversarial Networks For Optimal Evtol Takeoff Trajectory Prediction, Shuan Tai Yeh, Xiaosong Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Electric vertical takeoff and landing (eVTOL) aircraft represent a crucial aviation technology to transform future transportation systems. The unique characteristics of eVTOL aircraft include reduced noise, low pollutant emission, efficient operating cost, and flexible maneuverability, which in the meantime pose critical challenges to advanced power retention techniques. Thus, optimal takeoff trajectory design is essential due to immense power demands during eVTOL takeoffs. Conventional design optimizations, however, adopt high-fidelity simulation models in an iterative manner resulting in a computationally intensive mechanism. In this work, we implement a surrogate-enabled inverse mapping optimization architecture, i.e., directly predicting optimal designs from design requirements (including …

Effects Of Process-Induced Defects On The Corrosion Of Additively Manufactured Stainless Steel 304l, Leila Saberi, Frank W. Liou, Mehdi Amiri

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This Study Investigates the Impact of Process-Induced Defects Such as Gas Pores, Lack of Fusions, and Surface Roughness on Corrosion Behavior of Stainless Steel 304L (SS304L) Fabricated by Laser Powder Bed Fusion Additive Manufacturing. Specimens Are Printed with Optimized Process Parameters but Selected from Different Locations on the Build Plate. Parallel and Perpendicular Surfaces to the Build Direction Are Investigated and Compared with Corrosion Properties of Wrought SS304L in 5 Wt% NaCl. the Results Reveal Significant Difference in Corrosion Behavior among Specimens Due to Variations in their Defect Features. Pitting Potential, Pit Initiation, and Growth Rates Are Found to Be …

Effect Of Pre-Heating On Residual Stresses And Deformation In Laser-Based Directed Energy Deposition Repair: A Comparative Analysis, Usman Tariq, Sung Heng Wu, Muhammad Arif Mahmood, Michael M. Woodworth, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser-Directed Energy Deposition (DED), a Metal Additive Manufacturing Method, is Renowned for its Role in Repairing Parts, Particularly When Replacement Costs Are Prohibitive. Ensuring that Repaired Parts Avoid Residual Stresses and Deformation is Crucial for Maintaining Functional Integrity. This Study Conducts Experimental and Numerical Analyses on Trapezoidal Shape Repairs, Validating Both the Thermal and Mechanical Models with Experimental Results. Additionally, the Study Presents a Methodology for Creating a Toolpath Applicable to Both the DED Process and Abaqus CAE Software. the Findings Indicate that Employing a Pre-Heating Strategy Can Reduce Residual Stresses by over 70% Compared to No Pre-Heating. However, Pre-Heating …

Multifidelity Comparison Of Supersonic Wave Drag Prediction Methods Using Axisymmetric Bodies †, Troy Abraham, David Lazzara, Douglas Hunsaker

Mechanical and Aerospace Engineering Student Publications and Presentations

Low-fidelity analytic and computational wave drag prediction methods assume linear aerodynamics and small perturbations to the flow. Hence, these methods are typically accurate for only very slender geometries. The present work assesses the accuracy of these methods relative to high-fidelity Euler, compressible computational-fluid-dynamics solutions for a set of axisymmetric geometries with varying radius-to-length ratios (R/L). Grid-resolution studies are included for all computational results to ensure grid-resolved results. Results show that the low-fidelity analytic and computational methods match the Euler CFD predictions to around a single drag count (~1.0 × 10^–4) for geometries with R/L ≤ 0.05 …

Martian Atmospheric Rover Simulation (M.A.R.S.), Matt Berard, Shelby Beddard, Alexander Brunette, Emma Conti, Collin Duke, Delaney Novak, Keelin Weaver

Aerospace, Physics, and Space Science Student Publications

While rovers have been used by various agencies to explore Mars, their travel is limited by terrain obstacles, which may prevent mission completion. Creating a vehicle equipped with both driving and flight capabilities would allow greater range of motion on extraterrestrial planets. Integrating the technology for both transportation modes into one rover allows for efficiency and advancements in technological and planetary research.

Convolutional Spiking Neural Networks For Intent Detection Based On Anticipatory Brain Potentials Using Electroencephalogram, Nathan Lutes, V. Sriram Siddhardh Nadendla, K. Krishnamurthy

Computer Science Faculty Research & Creative Works

Spiking neural networks (SNNs) are receiving increased attention because they mimic synaptic connections in biological systems and produce spike trains, which can be approximated by binary values for computational efficiency. Recently, the addition of convolutional layers to combine the feature extraction power of convolutional networks with the computational efficiency of SNNs has been introduced. This paper studies the feasibility of using a convolutional spiking neural network (CSNN) to detect anticipatory slow cortical potentials (SCPs) related to braking intention in human participants using an electroencephalogram (EEG). Data was collected during an experiment wherein participants operated a remote-controlled vehicle on a testbed …

Experimental, Computational, And Machine Learning Methods For Prediction Of Residual Stresses In Laser Additive Manufacturing: A Critical Review, Sung Heng Wu, Usman Tariq, Ranjit Joy, Todd Sparks, Aaron Flood, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In recent decades, laser additive manufacturing has seen rapid development and has been applied to various fields, including the aerospace, automotive, and biomedical industries. However, the residual stresses that form during the manufacturing process can lead to defects in the printed parts, such as distortion and cracking. Therefore, accurately predicting residual stresses is crucial for preventing part failure and ensuring product quality. This critical review covers the fundamental aspects and formation mechanisms of residual stresses. It also extensively discusses the prediction of residual stresses utilizing experimental, computational, and machine learning methods. Finally, the review addresses the challenges and future directions …

Insight Into Uniform Filming Of Lif-Rich Interphase Via Synergistic Adsorption For High-Performance Lithium Metal Anode, Yufang He, Li Wang, Aiping Wang, Bo Zhang, Hiep Pham, Jonghyun Park, Xiangming He

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Multi-scale simulation is an important basis for constructing digital batteries to improve battery design and application. Lif-rich solid electrolyte interphase (sei) is experimentally proven to be crucial for the electrochemical performance of lithium metal batteries. However, the lif-rich sei is sensitive to various electrolyte formulas and the fundamental mechanism is still unclear. Herein, the structure and formation mechanism of lif-rich sei in different electrolyte formulas have been reviewed. On this basis, it further discussed the possible filming mechanism of lif-rich sei determined by the initial adsorption of the electrolyte-derived species on the lithium metal anode (lma). It proposed that individual …

Farmer Perceptions Of Land Cover Classification Of Uas Imagery Of Coffee Agroecosystems In Puerto Rico, Jose Cabrera, Blake Neal, Kevin Adkins, Ronny Schroeder, Gwendolyn Klenke, Shannon Brines, Nayethzi Hernandez, Kevin Li, Riley Glancy, Ivette Perfecto

Publications

Highly diverse agroecosystems are increasingly of interest as the realization of farms’ invaluable ecosystem services grows. Simultaneously there has been an increased use of uncrewed aerial systems (UAS) in remote sensing as drones offer a finer spatial resolution and faster revisit rate than traditional satellites. With the combined utility of UAS and the attention on agroecosystems, there exists an opportunity to assess UAS practicality in highly biodiverse settings. In this study, we utilized UAS to collect fine-resolution 10-band multispectral imagery of coffee agroecosystems in Puerto Rico. We created land cover maps through a pixel-based supervised classification of each farm and …

Relative Vectoring Using Dual Object Detection For Autonomous Aerial Refueling, Derek B. Worth, Jeffrey L. Choate, James Lynch, Scott L. Nykl, Clark N. Taylor

Faculty Publications

Once realized, autonomous aerial refueling will revolutionize unmanned aviation by removing current range and endurance limitations. Previous attempts at establishing vision-based solutions have come close but rely heavily on near perfect extrinsic camera calibrations that often change midflight. In this paper, we propose dual object detection, a technique that overcomes such requirement by transforming aerial refueling imagery directly into receiver aircraft reference frame probe-to-drogue vectors regardless of camera position and orientation. These vectors are precisely what autonomous agents need to successfully maneuver the tanker and receiver aircraft in synchronous flight during refueling operations. Our method follows a common 4-stage process …

Jet-Driven Mixing Regimes Identified In The Unsteady Isothermal Filling Of Rectangular Municipal Water Storage Tanks, Pramod Narayan Bangalore, K. (Kelly) O. Homan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Poor mixing of old and new water in municipal water storage vessels is a well-documented basis for potentially harmful water quality degradation in drinking water distribution systems. This numerical study investigates the effects of inflow and operational variables on mixing in the jet-driven filling process, with a particular focus on the transition from inadequate to sufficient mixing levels. An isothermal unsteady reynolds-averaged-navier-stokes volume-of-fluid (RANS-VOF) simulation is used to model the variable-volume filling process, accounting for the moving free surface following a draw-down in the stored water volume. A low diffusivity tracer is used to mark the old-water volume, and a …

Heat Treatments For Minimization Of Residual Stresses And Maximization Of Tensile Strengths Of Scalmalloy® Processed Via Directed Energy Deposition, Rachel Boillat-Newport, Sriram Praneeth Isanaka, Jonathan Kelley, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Scalmalloy® is an Al-Mg-Sc-Zr-Based Alloy Specifically Developed for Additive Manufacturing (AM). This Alloy is Designed for Use with a Direct Aging Treatment, as Recommended by the Manufacturer, Rather Than with a Multistep Treatment, as Often Seen in Conventional Manufacturing. Most Work with Scalmalloy® is Conducted using Powder Bed Rather Than Powder-Fed Processes. This Investigation Seeks to Fill This Knowledge Gap and Expand Beyond Single-Step Aging to Promote an overall Balanced AM-Fabricated Component. for This Study, Directed Energy Deposition (DED)-Fabricated Scalmalloy® Components Were Subjected to Low-Temperature Treatments to Minimize Residual Stresses Inherent in the Material Due to the Layer-By-Layer Build Process. …

Optimal Abort Guidance And Experimental Verification Based On Feature Learning, Vinay Kenny, Sixiong You, Chaoying Pei, Godfrey Hendrix, Roha Gul, Ran Dai, Jeremy Rea

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The abort mission refers to the mission where the landing vehicle needs to terminate the landing mission when an anomaly happens and be safely guided to the desired orbit. This paper focuses on solving the time-optimal abort guidance (TOAG) problem in real-time via the feature-based learning method. First, according to the optimal control theory, the features are identified to represent the optimal solutions of TOAG using a few parameters. After that, a sufficiently large data set of time-optimal abort trajectories is generated offline by solving the TOAG problems with different initial conditions. Then, the features are extracted for all generated …

Extraterrestrial Life: The Possibility Of A Human-Alien Interaction, Ariana M. Piscoya

CAFE Symposium 2024

We all have heard of at least one case where someone assured having seen a flying extraterrestrial object. There are thousands of thousands of videos we can find online that “prove” the existence of aliens. In the hypothetical case where aliens are really out there, why haven't we been able to talk to them and look at them face-to-face? A human-extraterrestrial interaction has not yet been achieved for two reasons. First, alien energy is much more powerful than that of humans, so it would require thousands of thousands of years for the human race to develop a technology able to …

Mission-Driven Inverse Design Of Blended Wing Body Aircraft With Machine Learning, Rohan S. Sharma, Serhat Hosder

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The intent of this work was to investigate the feasibility of developing machine learning models for calculating values of airplane configuration design variables when provided time-series, mission-informed performance data. Shallow artificial neural networks were developed, trained, and tested using data pertaining to the blended wing body (BWB) class of aerospace vehicles. Configuration design parameters were varied using a Latin-hypercube sampling scheme. These data were used by a parametric-based BWB configuration generator to create unique BWBs. Performance for each configuration was obtained via a performance estimation tool. Training and testing of neural networks were conducted using a K-fold cross-validation scheme. A …

Effects Of Laser Defocusing On Bead Geometry In Coaxial Titanium Wire-Based Laser Metal Deposition, Remy Mathenia, Aaron Flood, Braden Mclain, Todd Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Coaxial wire-based laser metal deposition is a versatile and efficient additive process that can achieve a high deposition rate in the manufacturing of complex structures. In this paper, a three-beam coaxial wire system is studied, with particular attention to the effects of deposition height and laser defocusing on the resulting bead geometry. As the deposition standoff distance changes, so does the workpiece illumination proportion, which describes the ratio of energy going directly into the feedstock wire and into the substrate. Single titanium beads are deposited at varying defocus levels and deposition rates and the bead aspect ratio is measured and …

Upconversion Photoluminescence Of Monolayer Wse2 With Biaxial Strain Tuning, Shrawan Roy, Jie Gao, Xiaodong Yang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Mechanical strain can be used to tune the optical properties of monolayer transition metal dichalcogenides (1L-TMDs). Here, up conversion photoluminescence (UPL) from 1L-WSe₂ flakes is tuned with biaxial strain induced by cruciform bending and indentation method. It is found that the peak position of UPL is redshifted by around 24 nm as the applied biaxial strain increases from 0% to 0.51%. At the same time, the UPL intensity increases exponentially for the up-conversion energy difference that lies within a broad range between −157 meV to −37 meV. The observed linear and sublinear power dependence of UPL emission in 1L-WSe …

Effects Of Organic Surface Contamination On The Mass Accommodation Coefficient Of Water: A Molecular Dynamics Study, Jordan Hartfield, Eric Bird, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The mass accommodation coefficient (MAC), a parameter that quantifies the possibility of a phase change to occur at a liquid-vapor interface, can strongly affect the evaporation and condensation rates at a liquid surface. Due to the various challenges in experimental determination of the MAC, molecular dynamics (MD) simulations have been widely used to study the MAC on liquid surfaces with no impurities or contaminations. However, experimental studies show that airborne hydrocarbons from various sources can adsorb on liquid surfaces and alter the liquid surface properties. In this work, therefore, we study the effects of organic surface contamination, which is immiscible …