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Efforts In Numerical Modeling Of Undulating Propulsion, George Loubimov 2020 University of Central Florida

Efforts In Numerical Modeling Of Undulating Propulsion, George Loubimov

Electronic Theses and Dissertations, 2020-

Naval propulsion is a critical component for every vessel, and it is the subject of this thesis, specifically bio-inspired propulsion. Numerical modeling is used as a tool to understand the relationship between mechanical undulation and the hydrodynamic response. Through three stages, the research presented here examines and refines tools for understanding fundamentals of undulating propulsion. Those three objectives are: to verify and validate the proposed numerical models against existing experiments, establishing a baseline of fidelity; to examine the causal linkage between fluid-boundary interactions and undulating propulsion; and to create a moment based method for characterizing generalized undulating propulsive mechanisms. First ...


Mechanical Properties Of Boron Carbide (B4c), Ruslan Kuliiev 2020 University of Central Florida

Mechanical Properties Of Boron Carbide (B4c), Ruslan Kuliiev

Electronic Theses and Dissertations, 2020-

Boron carbide (B4C) is one of the most important opaque boride ceramics that has high hardness and Young's modulus that along with low density lead to a significant resistance to ballistic impact and, thus, B4C is broadly used as a protective material. B4C has also high neutron capturing cross section; therefore, it is used as control rods and neutron absorption shielding in nuclear reactors. In this work thermal, electrical and mechanical properties of dense B4C ceramics (99%) sintered using Spark Plasma Sintering (SPS) were investigated. The Young's modulus of B4C measured by three different techniques – IE, RUS, and ...


Piezospectroscopic Sensing Systems - Multi-Scale And In-Situ Sensing Technology For Structural Integrity, Remelisa Esteves 2020 University of Central Florida

Piezospectroscopic Sensing Systems - Multi-Scale And In-Situ Sensing Technology For Structural Integrity, Remelisa Esteves

Electronic Theses and Dissertations, 2020-

The aerospace industry relies on nondestructive evaluation (NDE) to ensure aircraft safety and will benefit from methods that allow for early damage detection. Photoluminescence piezospectroscopy (PS) has demonstrated stress and damage sensing of substrates when coupled with alpha-alumina nanoparticles in a polymer matrix applied as a sensor coating. Alpha phase alumina exhibits photoluminescent spectral emission lines (R-lines) that shift due to changes in the stress state of the alumina. The coatings' capability for sensing early subsurface damage suggests the potential for implementing stress sensing paint for integrity monitoring of aircraft structures. To achieve a viable stress sensing coating that can ...


Aeroelasticity Of Composite Plate Wings Using Hsdt And Higher-Order Fem, Justin A. Haught 2020 West Virginia University

Aeroelasticity Of Composite Plate Wings Using Hsdt And Higher-Order Fem, Justin A. Haught

Graduate Theses, Dissertations, and Problem Reports

The aeroelasticity of composite wings is becoming an increasingly researched topic in aircraft design, as designers continue to replace aluminum alloy components with those made of composite materials because of their favorable strength-to-weight ratio, fatigue characteristics, and corrosion resistance. Additionally, the bending-torsion coupling exhibited by composite laminates readily allow for the aeroelastic optimization of an aerodynamic structure through the process of aeroelastic tailoring. Wings made of composites materials, however, are more vulnerable to shear deformation.

The objective of the present research is to study the divergence and flutter characteristics of composite plate wings using a higher-order shear deformation theory (HSDT ...


Characterizing Premixed Syngas Combustion In Micro-Channels, Sunita Pokharel 2020 West Virginia University

Characterizing Premixed Syngas Combustion In Micro-Channels, Sunita Pokharel

Graduate Theses, Dissertations, and Problem Reports

Increasing demands in the next-generation portable power-generation devices such as unmanned aerial vehicles (UAV), microsatellite thrusters, micro-chemical reactors and sensors calls for fuels with high specific energy and low emissions to meet the current demand of green energy. Fuel-lean synthesis gas (syngas) meets both these requirements exhibiting a promising route to a clean and green environment. Thus, it is of critical importance to characterize syngas combustion and understand its properties in the micro-combustion industry. In addition to complicated flame dynamics in microscale systems, varying the syngas-fuel mixture composition as well as the boundary conditions and geometry of a combustor significantly ...


Characterization Of Simulated Low Earth Orbit Space Environment Effects On Acid-Spun Carbon Nanotube Yarns, Ryan A. Kemnitz, Gregory R. Cobb, Abhendra K. Singh, Carl R. Hartsfield 2019 Air Force Institute of Technology

Characterization Of Simulated Low Earth Orbit Space Environment Effects On Acid-Spun Carbon Nanotube Yarns, Ryan A. Kemnitz, Gregory R. Cobb, Abhendra K. Singh, Carl R. Hartsfield

Faculty Publications

The purpose of this study is to quantify the detrimental effects of atomic oxygen and ultraviolet (UV) C radiation on the mechanical properties, electrical conductivity, and piezoresistive effect of acid-spun carbon nanotube (CNT) yarns. Monotonic tensile tests with in-situ electrical resistance measurements were performed on pristine and exposed yarns to determine the effects of the atomic oxygen and UVC exposures on the yarn’s material properties. Both type of exposures were performed under vacuum to simulate space environment conditions. The CNT yarns’ mechanical properties did not change significantly after being exposed to UV radiation, but were significantly degraded by the ...


Highly Reactive Energetic Films By Pre-Stressing Nano-Aluminum Particles, Michael N. Bello, Alan M. Williams, Valery I. Levitas, Nobumichi Tamura, Daniel K. Unruh, Juliusz Warzywoda, Michelle L. Pantoya 2019 Texas Tech University

Highly Reactive Energetic Films By Pre-Stressing Nano-Aluminum Particles, Michael N. Bello, Alan M. Williams, Valery I. Levitas, Nobumichi Tamura, Daniel K. Unruh, Juliusz Warzywoda, Michelle L. Pantoya

Aerospace Engineering Publications

Energetic films were synthesized using stress altered nano-aluminum particles (nAl). The nAl powder was pre-stressed to examine how modified mechanical properties of the fuel particles influenced film reactivity. Pre-stressing conditions varied by quenching rate. Slow and rapid quenching rates induced elevated dilatational strain within the nAl particles that was measured using synchrotron X-ray diffraction (XRD). An analytical model for stress and strain in a nAl core–Al2O3 shell particle that includes creep in the shell and delamination at the core–shell boundary, was developed and used for interpretation of strain measurements. Results show rapid quenching induced 81% delamination at the ...


Multiscale Modeling Of Fracture In Quasi-Brittle Materials Using Bifurcation Analysis And Element Elimination Method, Keyvan Zare Rami 2019 University of Nebraska-Lincoln

Multiscale Modeling Of Fracture In Quasi-Brittle Materials Using Bifurcation Analysis And Element Elimination Method, Keyvan Zare Rami

Civil and Environmental Engineering Theses, Dissertations, and Student Research

Analyzing the fracture of heterogeneous materials is a complex problem, due to the fact that the mechanical behavior of a heterogeneous material is strongly dependent on a variety of factors, such as its microstructure, the properties of each constituent, and interactions between them. Therefore, these factors must be effectively taken into account for accurate analysis, for which the multiscale method has been widely used. In this scheme, the computational homogenization method is used to obtain the effective macroscopic properties of a heterogeneous material based on the response of a Representative Volume Element (RVE). The growth of damage in an RVE ...


Methodology Of Topology Optimization, Naziha Khandoker 2019 Western Michigan University

Methodology Of Topology Optimization, Naziha Khandoker

Honors Theses

The need for lighter products is becoming increasingly essential as it cuts material cost and significant amount of weight, which is a key factor in the automotive and aerospace industries. Topology optimization allows us to achieve that by applying the concept to different structures with the goal of optimal distribution of material within finite volume design domain. Its algorithms selectively remove and relocate elements to achieve the optimum performance. This project performs a study on the effect of each design parameter over mechanical performance using Finite Element Analysis and applies it to set of wing attachment brackets. The optimized brackets ...


The Effectiveness Of Augmented Reality For Astronauts On Lunar Missions: An Analog Study, Godfrey Valencio D’souza 2019 Embry-Riddle Aeronautical University

The Effectiveness Of Augmented Reality For Astronauts On Lunar Missions: An Analog Study, Godfrey Valencio D’Souza

Dissertations and Theses

The uses of augmented reality and head-up displays are becoming more prominent in industries such as aviation, automotive, and medicine. An augmented reality device such as the Microsoft HoloLens can project holograms onto the user’s natural field of view to assist with completion of a variety of tasks. Unfortunately, only a little research and development has begun in the space sector for astronauts using these head-up displays. Future lunar missions could incorporate augmented reality for astronauts to ease task load and improve accuracy. This study evaluated the usability, subjective workload, and task performance of 22 participants using the Microsoft ...


Numerical Treatment Of Schrödinger’S Equation For One-Particle And Two-Particle Systems Using Matrix Method, Spatika Dasharati Iyengar 2019 Embry-Riddle Aeronautical University

Numerical Treatment Of Schrödinger’S Equation For One-Particle And Two-Particle Systems Using Matrix Method, Spatika Dasharati Iyengar

Dissertations and Theses

With an increased interest in accurately predicting aerothermal environments for planetary entry, recent researches have concentrated on developing high fidelity computational models using quantum-mechanical first principles. These calculations are dependent on solving the Schrödinger equation using molecular orbital theory techniques. They are either approximate solutions to actual equations or exact solutions to approximate equations. Exact solutions have not found favor due to the computational expense of the problem. Hence, a novel numerical approach is developed and tested here using linear algebraic matrix methods to enable precise solutions.

The finite-difference technique is used to cast the Time-Independent Schrödinger equation (TISE) in ...


In-Situ Measurement Of Resin Shrinkage For Aerospace Components, Samarth Motagi 2019 Embry-Riddle Aeronautical University

In-Situ Measurement Of Resin Shrinkage For Aerospace Components, Samarth Motagi

Dissertations and Theses

Resin shrinkage due to chemical changes and thermal gradients plays an important role in the residual stress evolution during composite manufacturing. In this thesis, we develop a new in-situ experimental approach for measuring resin shrinkage during curing with the help of digital image correlation (DIC) instrumented on a specially designed autoclave with borosilicate viewports. The images of the resin sample are captured at regular intervals with the help of DIC to measure the displacement and strains during the curing process. We utilize this method for a comparative analysis of resin shrinkage in two common aerospace epoxies, Epoxy 105 and EPON ...


Fuel Shortages During Hurricanes: Epidemiological Modeling And Optimal Control, Sabique Ul Islam 2019 Embry-Riddle Aeronautical University

Fuel Shortages During Hurricanes: Epidemiological Modeling And Optimal Control, Sabique Ul Islam

Dissertations and Theses

Hurricanes are powerful agents of destruction with significant socioeconomic impacts. A persistent problem due to the large-scale evacuations during hurricanes in the southeastern United States is the fuel shortages during the evacuation. Fuel shortages often lead to stranded vehicles and exacerbate the evacuation efforts. Computational models can aid in emergency preparedness and help mitigate the impacts of hurricanes. In this thesis, the hurricane fuel shortages are modeled using the Susceptible-Infected-Recovered (SIR) epidemic model. Crowd-sourced data corresponding to Hurricane Irma and Florence are utilized to parametrize the model. An estimation technique based on Unscented Kalman filter (UKF) is employed to evaluate ...


Numerical Investigation Of Scaling Effects Of A Ramjet-Powered Projectile, Arjun Jaishankar Vedam 2019 Embry-Riddle Aeronautical University

Numerical Investigation Of Scaling Effects Of A Ramjet-Powered Projectile, Arjun Jaishankar Vedam

Dissertations and Theses

Ramjet flowpath miniaturization is a potentially useful technology for integration into munitions to increase range, accuracy, and lethality. The emphasis of this effort is to numerically characterize the performance of a miniature hydrogen-fueled and ethylene-fueled ramjet flowpath during Mach 3 and Mach 3.5 sea-level flight. The effect of geometric scale on ramjet performance is evaluated using high-fidelity RANS CFD models. Sensitivity to nonequilibrium laminar and turbulence-limited chemistry, and transitional turbulence treatments are evaluated. The physical sources of small scale performance limitations are identified for both fuel types. Finally, flowpath integration for small-scale applications is briefly addressed.


Adaptive Learning Terrain Estimation For Unmanned Aerial Vehicle Applications, Pedro L. Vergara Garcia 2019 Embry-Riddle Aeronautical University

Adaptive Learning Terrain Estimation For Unmanned Aerial Vehicle Applications, Pedro L. Vergara Garcia

Dissertations and Theses

For the past decade, terrain mapping research has focused on ground robots using occupancy grids and tree-like data structures, like Octomap and Quadtrees. Since flight vehicles have different constraints, ground-based terrain mapping research may not be directly applicable to the aerospace industry. To address this issue, Adaptive Learning Terrain Estimation algorithms have been developed with an aim towards aerospace applications. This thesis develops and tests Adaptive Learning Terrain Estimation algorithms using a custom test benchmark on representative aerospace cases: autonomous UAV landing and UAV flight through 3D urban environments. The fundamental objective of this thesis is to investigate the use ...


Wall-Jet Turbulence And Mixing Control By Way Of A Pulsed Inlet Velocity, Cristale D. Garnica Vallejo 2019 Embry-Riddle Aeronautical University

Wall-Jet Turbulence And Mixing Control By Way Of A Pulsed Inlet Velocity, Cristale D. Garnica Vallejo

Dissertations and Theses

Understanding wall-jet-induced turbulence and mixing is an important challenge in modern engineering, as drag reduction and mixing enhancement are attainable by modifying the flow development. Simulations are performed to investigate the effect on skin friction and flow mixing due to introducing controlled perturbations, at the initial shear layer of a planar wall-jet using jet inlet cyclic pulsing. The billow production by the Kelvin-Helmholtz instability, the instability that drives turbulence in a wall-jet, is modified by the excitation of the inlet velocity profile by a sine wave perturbation. Two types of wall-jet simulations are carried out, a two-dimensional compressible case at ...


Estimation Of The Fatigue Life Of Additively Manufactured Metallic Components Using Modified Strain Life Parameters Based On Surface Roughness, Peter Grohs 2019 Western Michigan University

Estimation Of The Fatigue Life Of Additively Manufactured Metallic Components Using Modified Strain Life Parameters Based On Surface Roughness, Peter Grohs

Master's Theses

In this study, a method is developed to estimate the effects of surface roughness on the fatigue life of additively manufactured titanium Ti6Al4V, aluminum 7075–T6, and steel 4340 alloys through modified strain life parameters using finite element analysis (FEA). This method is highly beneficial to the fatigue analysis of as-built additively manufactured metal components, which possess rough surfaces that reduce fatigue life significantly but are challenging to analyze directly using finite element simulation because of complex geometries, i.e., modeling an exact surface profile is arduous.

An effective stress concentration factor, incorporating roughness data, is defined to quantify their ...


Autonomous Autorotation Of A Tilt-Rotor Aircraft Using Model Predictive Control, Elias Wilson 2019 Embry-Riddle Aeronautical University

Autonomous Autorotation Of A Tilt-Rotor Aircraft Using Model Predictive Control, Elias Wilson

Dissertations and Theses

Tilt rotor vehicles are governed by FAA laws also used for conventional helicopters, which require autorotational maneuvering and landing given a total power failure. With low inertia rotors and high disk loading of tilt rotor vehicles, this already difficult task becomes significantly more challenging. In this work, a model predictive controller is developed to autonomously maneuver and land a tilt rotor given complete power loss. A high fidelity model of a tilt rotor vehicle is created and used to simulate the vehicle dynamics and response to control inputs. A reduced order dynamic model is used within a model predictive control ...


A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa 2019 Western Michigan University

A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa

Dissertations

This dissertation explores a novel method of solving low-thrust spacecraft targeting problems using reinforcement learning. A reinforcement learning algorithm based on Deep Deterministic Policy Gradients was developed to solve low-thrust trajectory optimization problems. The algorithm consists of two neural networks, an actor network and a critic network. The actor approximates a thrust magnitude given the current spacecraft state expressed as a set of orbital elements. The critic network evaluates the action taken by the actor based on the state and action taken. Three different types of trajectory problems were solved, a generalized orbit change maneuver, a semimajor axis change maneuver ...


Tumble Bot, Alena Beyer, Blake Gonzales, Jensen Severance, Liam Chaffey 2019 California Polytechnic State University, San Luis Obispo

Tumble Bot, Alena Beyer, Blake Gonzales, Jensen Severance, Liam Chaffey

Mechanical Engineering

Passive locomotion is the ability for an object to move from one place to another by the means of the environment. In nature species such as tumbleweed, fox tails, plankton, and man o’ war jellyfish rely on passive modes of transportation for survival and are able to cross vast distances with little to no expenditure of their own energy. This document seeks to explore the feasibility of building a machine relies on the energy of Mars’ environment to explore the Martian surface.

The “Tensegrity Tumbleweed Locomotion” (nicknamed Tumble Bot) senior project was sponsored by NASA Jet Propulsion Laboratory (JPL). The ...


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