Aerospace Engineering Commons^™

A Robust Recurrent Neural Networks-Based Surrogate Model For Thermal History And Melt Pool Characteristics In Directed Energy Deposition, Sung Heng Wu, Usman Tariq, Ranjit Joy, Muhammad Arif Mahmood, Asad Waqar Malik, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In directed energy deposition (DED), accurately controlling and predicting melt pool characteristics is essential for ensuring desired material qualities and geometric accuracies. This paper introduces a robust surrogate model based on recurrent neural network (RNN) architectures—Long Short-Term Memory (LSTM), Bidirectional LSTM (Bi-LSTM), and Gated Recurrent Unit (GRU). Leveraging a time series dataset from multi-physics simulations and a three-factor, three-level experimental design, the model accurately predicts melt pool peak temperatures, lengths, widths, and depths under varying conditions. RNN algorithms, particularly Bi-LSTM, demonstrate high predictive accuracy, with an R-square of 0.983 for melt pool peak temperatures. For melt pool geometry, the GRU-based …

Ground Vacuum Facility To Simulate Low Earth Orbit Plasma Environment, Emmanuel Kofi Asuako Wie-Addo, Jacob Ortega, Daoru Han

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a large vacuum facility (6-ft-diameter, 10-ft-long chamber) equipped with a magnetic filter-type low Earth orbit plasma source. A recommended operating envelope for the plasma source was established through single-point measurements by varying the discharge currents of the plasma source and the gas flow rates. A three-axis translation stage was fabricated and tested with 2D and 3D scans of the simulated plasma environment. The measured plasma density during this study was between 1:63 x 1012 − 3:1 x 1012 m−3 for the electrons and 7:54 x 1012 − 1:82 x 1013 m−3 for the ions, whereas the electron …

Surrogate-Based Multidisciplinary Optimization For The Takeoff Trajectory Design Of Electric Drones, Samuel Sisk, Xiaosong Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Electric vertical takeoff and landing (eVTOL) aircraft attract attention due to their unique characteristics of reduced noise, moderate pollutant emission, and lowered operating cost. However, the benefits of electric vehicles, including eVTOL aircraft, are critically challenged by the energy density of batteries, which prohibit long-distance tasks and broader applications. Since the takeoff process of eVTOL aircraft demands excessive energy and couples multiple subsystems (such as aerodynamics and propulsion), multidisciplinary analysis and optimization (MDAO) become essential. Conventional MDAO, however, iteratively evaluates high-fidelity simulation models, making the whole process computationally intensive. Surrogates, in lieu of simulation models, empower efficient MDAO with the …

Heuristic Design Of Cislunar Space Situational Awareness Architectures, Jacob A. Dahlke

Theses and Dissertations

The growing interest in the cislunar domain, which encompasses geosynchronous Earth orbit (GEO), the Moon, and the region where Earth-Moon gravitational effects are the primary influence, necessitates the development of tools to ensure safe and successful exploration. Space situational awareness (SSA) involves monitoring an environment to detect, track, identify, and catalog space objects. While most SSA experience comes from near-Earth operations, expanding into the cislunar domain presents significant challenges due to its vast expanse—greater than 10 times the radius of GEO—and the unique dynamics governed by the Circular Restricted Three-Body Problem (CR3BP) influenced by both Earth and Moon gravitational forces. …

Optimal Placement Of Artificial Hair-Cell Airflow Sensors For Bioinspired Flight-By-Feel, Alex C. Hollenbeck

Theses and Dissertations

The Sparse Sensor Placement Optimization for Prediction (SSPOP) algorithm reduces highdimensional airflow data to a low-dimensional sparse approximation to identify an optimal placement for any number of sensors on airfoil or wing models of arbitrary shape and size, and outperforms conventional optimization techniques in accuracy and speed. For 2D flow this algorithm found a sensor placement solution (design point, or DP) which predicts AoA to within 0.10 degrees and ranks within the top 1 percent of the design space. On 3D wing models SSPOP found four-sensor DPs ranked well within the top 0.10 percent. Experimental validation with velocity and pressure …

Guidance, Navigation, And Control For Multi-Agent Inspection Of An Unknown Space Object, Mark R. Mercier

Theses and Dissertations

On-orbit inspection is a rapidly growing mission that enables extending the life of aging legacy space systems through refueling, replacing, or upgrading components. For an inspection operation, multiple agents taking observations simultaneously can more quickly map an RSO and assure an inspection is complete regardless of RSO dynamics. A multi-agent guidance, navigation, and control (GNC) scheme must be designed with cooperation in mind to achieve inspection objectives, while leveraging the unique capabilities of a distributed inspection system. This work splits the GNC system into two parts composed of an offline guidance scheme for translational reference trajectory generation and an online …

Koopman-Based Modeling For Nonlinear Control Of Multirotor Uavs, Simone Martini

Electronic Theses and Dissertations

This PhD dissertation focuses on adopting the emerging Koopman Operator theory for modeling and nonlinear control of multirotor UAVs, focusing specifically on quadrotors for proof-of-concept demonstration purposes.

The Koopman Operator theory is based on the foundation that nonlinear dynamics in the state space may be represented as a linear evolution of some functions in the state space. Thus, using appropriately defined and possibly nonlinear functions of the state variables, called observables, as a new and maybe infinite set of coordinates that are referred to as lifted space, the original nonlinear dynamics appear to be linear. The implications of this theory …

Contributions To The Understanding Of Turbulent Boundary Layers Over Curved Walls, Nicholas Zhu

Doctoral Dissertations and Master's Theses

A wind tunnel campaign was conducted to investigate the DARPA Suboff boundary layer. To emphasize the axisymmetric boundary layer, the generic submarine model's sail, appendages, and propeller were omitted. The study focused on the afterbody from 70–95% of the model length to examine the concurrent pressure gradient and wall curvature effects, which are commonplace in engineering. Three particle image velocimetry (PIV) configurations were employed to measure the boundary layer in detail: one spanned the entire afterbody, another had narrow strips sampled at 16 kHz, and the third used two simultaneous orthogonal measurement planes. Considerable effort was made to reduce the …

End-To-End Full-Width Induction Welding Of Unidirectional Tape-Based Thermoplastic Composites, Jaspreet Singh Pandher

Theses and Dissertations

The current large scale application of thermoset composite materials in large, twin aisle, civil transport aircraft have resulted in significant performance enhancements, such as aerodynamic efficiency, weight reduction, and durability. These large aircraft are, however, produced in relatively low numbers. For the next generation smaller single aisle aircraft, large scale applications of composites are of interest in the airframe. Application of composites in single aisle aircraft will require not only proof of similar and/or significant performance improvements, but also proof of adequate manufacturing rates. One option to achieve both is large scale application of thermoplastic instead of thermoset composites.

Thermoplastic …

Towards The Induction Welding Of Complex, Curved Thermoplastic Composite Structures, Andrew Cole Cromer

Theses and Dissertations

Recent advancements in the aerospace industry, coupled with the anticipated future significance of air travel, have spurred research aimed at increasing manufacturing production and aircraft flying efficiency by implementing new materials and assembly methods. Advanced air mobility (AAM), a subset of the aerospace industry, is anticipated to become a crucial component of the transportation infrastructure in densely populated regions. To meet the expected demand, there is a need for investigations into novel manufacturing and joining methods. This industry necessitates materials that are lightweight, durable, and amenable to high-rate production. One potential avenue under exploration is the utilization of thermoplastic composites. …

The Study And Development Of Autonomous Scarf Repair For Composite Structures: A Focus On Advanced Air Mobility Vehicles, Stephen Hilton

Theses and Dissertations

“I’m sorry I haven’t been able to truly give you a solution to thermoplastic repair” – Arnt. Director GKN Global Tech Center, 2023

The aerospace industry has a prevalence of composite materials due to their outstanding benefits to the mechanical properties of structures while serving to reduce the overall structure weight. With the development of the Advanced Air Mobility market, there is an anticipated growth in the number of composite structures. Also, with the manufacturing environment of the 21st century, these composite structures are more and more being made using thermoplastic composites that can be recycled at the end of …

High-Rate Production Of Thermoplastic Composite Structures For Urban Air Mobility Vehicles Utilizing Fastener-Free Assembly Methods, Robert H. Shumpert

Theses and Dissertations

This study aimed to develop a manufacturing plan for a Thermoplastic fiber-reinforced propeller blade for urban air mobility applications. This propeller blade offer a few unique challenges including the complex geometries of the blade. Another important aspect of the blade is using fusion bonding methods to increase the strength of joints in the product while reducing weight from fasteners and adhesives. This manufacturing process will be validated by producing a physical demonstrator to ascertain the efficacy of the manufacturing techniques used. First, the techniques that will make up the manufacturing plan must be selected. To do this, a review of …

Customized Agile Project Management For Scientific Computing: Addressing Challenges And Developing A Framework, Yashesh Sakharikar

Harrisburg University Dissertations and Theses

This paper presents a novel Agile framework tailored for scientific computing projects. Identifying gaps in existing methodologies, the research emphasizes the need for adaptable solutions in this dynamic field. The proposed framework, characterized by flexibility and stakeholder engagement, addresses specific challenges posed by scientific computing endeavors. Through a comprehensive literature review, the paper highlights the limitations of generic Agile practices and positions the proposed framework as a valuable contribution. The study motivates further exploration into specialized Agile approaches, promising enhanced efficiency and success in scientific computing projects.

Heat Transfer To Arrays Of Oscillating Impingement Jets, Alex Q. Clay

Doctoral Dissertations and Master's Theses

In gas turbine engines, the desire to increase turbine entry temperatures has become more relevant in order to increase engine efficiency. However, materials used in these engines can only withstand temperatures that are so high. Because of this, the ability to cool hot section components will always limit operating temperatures. Impingement cooling jets have become a common way of cooling due to the high rates of heat transfer that can be achieved. However, previous research has shown that the interaction of impingement jets with cylinder wake can improve the intensity and uniformity of heat transfer. The goal of this study …

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 …

Error Detection & Correction, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs on "Error Detection & Correction" from August 2, 2024.

Re-Architecting Space Systems: Infrastructure Changes Everything, Rick Fleeter

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Rick Fleeter on "Re-Architecting Space Systems: Infrastructure Changes Everything" from

Comm-Modulation & Data Transmission Errors, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs on "Comm-Modulation & Data Transmission Errors" from August 2, 2024.

Development And Processing Of Shape Memory Polymer Composites (Smpcs) For Application In Structural Robotics And Robotic Sensors., Kavish Sudan

Electronic Theses and Dissertations

Shape Memory Polymers (SMPs) have attracted significant attention since their introduction in the 1980s due to their remarkable ability to regain their original shape from a temporarily deformed state when exposed to an external stimulus, typically heat. This shape memory effect, driven by thermal transitions such as the glass transition temperature (T_g) or melting temperature (T_m), has made SMPs highly attractive for applications in soft robotics, aerospace, and biomedical devices. However, SMPs face challenges such as limited mechanical strength, thermal stability, and electrical conductivity, which hinder their broader adoption in advanced applications. To address these challenges, …

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 …