Engineering Commons^™

Torque Limit Of A Mechanical Fastener In A Graphite/Epoxy Joint, Kristian M. Kostreva

Master's Theses - Daytona Beach

Presently there is a lack of confidence amongst engineers when specifying the preload of a mechanical fastener in a composite joint due to a lack of a fundamental knowledge base regarding the behavior of composites under fastener compressive load. As such, a novel experimental procedure was developed herein to determine the through-the-thickness compressive (TTTC) material properties. A total of 206 property tests were performed on four different graphite/epoxy material systems. The results confirmed that TTTC material properties vary with fiber orientation, laminate thickness, fiber volume fraction, and even laminate surface finish. Hence, the 'rule of mixtures' provides a poor estimate …

Developmental Flight Test Of A Powered Approach Stability Augmentation System On The U.S. Navy's E- 2c Hawkeye 2000 Aircraft, Robert K. Williams

Masters Theses

The E-2C aircraft is a Navy carrier based high-wing, twin engine turboprop powered aircraft used for the Airborne Early Warning (AEW) mission. In the power approach configuration, the aircraft displays strong adverse yaw, weak directional stability, and excessive rudder control power. These antagonistic characteristics, when coupled together, result in an extremely high workload for the pilot during both carrier and field landings. Although the aircraft has a yaw axis stability augmentation system, it is currently only applicable to cruise conditions. Engaging the stability augmentation in the power approach configuration results in a 1 Hz directional oscillation due to the system’s …

Evolution Of A Monomer Concentration Field In A Micro-Fluidic Channel, Michael Francis Kirsch

Masters Theses

The purpose of this research is to determine how long a micro-channel could be in the production of Non-Linear Optical Thin Film Wave-Guides. In determining this length, it is necessary to compute the monomer diffusion process between two solutions of monomers in a micro channel flow. Two models of this flow were created, the first with no flow in a one dimensional channel making diffusion a function of time and position and the second of flow in a two dimensional channel with an imposed velocity profile. Using these models it was determined that the micro channel could be the longest …

Using The Boundary Element Method For Prediction Of Sound Radiated From An Arbitrarily Shaped Vibrating Body, Mark J. Christensen

Masters Theses

The Boundary Element Method can be used to predict sound pressure levels radiated from an arbitrarily shaped vibrating body. Using the Direct, Indirect and Approximation formulation one can solve such an ‘exterior’ acoustic problem. In this work, the Direct formulation was chosen. The two major methods employed for implementation of this formulation are the Combined Helmholtz Integral Equation Formulation (CHIEF) and the Burton–Miller Method. Since the CHIEF method was easier to program and adapt to changes, it was decided that the CHIEF method would be the focus of this research. Using the CHIEF method as a guide, a computer simulation …

F/A-18e/F Catapult Minimum End Airspeed Testing, Michael M. Wallace

Masters Theses

The F/A-18E/F Super Hornet is the result of major upgrades to previous series of F/A-18 Hornet aircraft (F/A-18A/B/C/D). These upgrades resulted in an airplane requiring a complete Engineering and Manufacturing Development (EMD) phase. Catapult minimum end airspeed tests took place near the end of the three and a half year EMD program to provide data for the Aircraft Launch Bulletin for Operational Evaluation and fleet operations. The tests had occurred on average only every six years for any type of aircraft and 10-15 years for the same model of aircraft in the last 30 years.

The objective of this thesis …

Use Of Dimples To Suppress Boundary Layer Separation On A Low Pressure Turbine Blade, Kurt P. Rouser

Theses and Dissertations

Flow separation on a low pressure turbine blade is explored at Reynolds numbers of 25k, 45k and 100k. Experimental data is collected in a low-speed, draw-down wind tunnel using a cascade of eight Pak-B blades. Flow is examined from measurements of blade surface pressures, boundary layer parameters, exit velocities, and total pressure losses across the blade. Two recessed dimple shapes are assessed for suppressing flow separation and associated losses. One dimple is spherical, and the second is asymmetric, formed from a full dimple spanwise half-filled. A single row of each dimple shape is tested at 50%, 55% and 65% axial …

Implementation Of Gy-Eq For Deterministic Effects Limitation In Shield Design, John W. Wilson, Myung-Hee Y. Kim, Giovanni De Angelis, Francis A. Cucinotta, Nobuaki Yoshizawa, Francis F. Badavi

Mathematics & Statistics Faculty Publications

The NCRP has recently defined RBE values and a new quantity (Gy-Eq) for use in estimation of deterministic effects in space shielding and operations. The NCRP's RBE for neutrons is left ambiguous and not fully defined. In the present report we will suggest a complete definition of neutron RBE consistent with the NCRP recommendations and evaluate attenuation properties of deterministic effects (Gy-Eq) in comparison with other dosimetric quantities.

Lunar Lava Tube Radiation Safety Analysis, Giovanni De Angelis, J. W. Wilson, M. S. Clowdsley, J. E. Nealy, D. H. Humes, J. M. Clem

Mathematics & Statistics Faculty Publications

For many years it has been suggested that lava tubes on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava tubes has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith …

Electromagnetic Scattering From A Gap In A Magneto-Dielectric Coating On An Infinite Ground Plane, George R. Simpson

Theses and Dissertations

The electromagnetic scattering from a gap in a magneto-dielectric coating on an infinite ground plane is analyzed. In this context, the gap forms a break only in the magneto-dielectric slab coating while the ground plane is continuous and unbroken. Volume equivalence is used to convert the gap region to one containing unknown volumetric equivalent electric and magnetic currents. The equivalent problem then is one of these currents radiating in the presence of an unbroken grounded magneto-dielectric slab. A Green's function for this geometry is developed consisting of two terms: a direct coupling term and correction term to account for the …

The Family Science Starter Kit: A Manual To Assist You In The Development Of A Family Aeronautical Science Program, Henry R. Leher, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 02-6

This book is designed to involve families working together on several different hands-on activities during evening meetings at school. The basis for these activities is the in-school study of related science and mathematical concepts and topics by the students in each family. The program provides an opportunity for families to work together in an interesting and enjoyable manner. The Family Aeronautical Science demonstration project consisted of three parts: (1) the in-school study of aeronautics during select science classes; (2) the extensive after-school use of the school’s computer laboratory; and (3) evening Family Aeronautical Science Nights. Key parts …

The Aeronautics Education, Research, And Industry Alliance (Aerial) 2002 Report, Brent D. Bowen, Mary M. Fink, Jocelyn S. Nickerson, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 02-7

The NASA Nebraska Space Grant Consortium (NSGC) & EPSCoR programs at the University I of Nebraska at Omaha are involved in a variety of innovative research activities. Such research is supported through the Aeronautics Education, Research, and Industry Alliance (AERIAL) and collaborative seed funds. AERIAL is a comprehensive, mulch-faceted, five year NASA EPSCoR initiative that contributes substantially to the strategic research and technology priorities of NASA while intensifying Nebraska’s rapidly growing aeronautics research and development endeavors.

AERIAL includes three major collaborative research teams (CRTs) whose nexus is a common focus in aeronautics research. Each CRT - Small …

Photoreflectance Spectroscopy Of Strained (In)Gaasn/Gaas Multiple Quantum Wells, J. B. Heroux, Xiaodong Yang, W. I. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effect of a variation of the indium and nitrogen concentrations in Inᵪ Ga_1-x As_1-y N_y /GaAs multiquantum wells grown by molecular beam epitaxy is studied systematically by room temperature photoreflectance spectroscopy. The band gap redshift caused by a nitrogen fraction of 1.5% decreases by as much as 30% as the indium fraction increases from 0% to 20%. A moderate increase of electron effective mass (Δmₑ ~ 0.03m₀) is found in all samples containing nitrogen (y ≳ 1%). In compressively strained quantum wells, the energy separation between the first confined heavy and light hole energy levels decreases …

Flightlines, Vol. 10, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Modeling Of Acoustic Emission Failure Mechanism Data From A Unidirectional Fiberglass/Epoxy Tensile Test Specimen, Daniel R. Lendzioszek

Master's Theses - Daytona Beach

The purpose of this work was to model the acoustic emission (AE) flaw growth data that resulted from the tensile test of a unidirectional fiberglass/epoxy specimen. The data collected and stored during the test were the six standard AE quantification parameters for each event. A classification neural network was used to sort the data into five failure mechanism clusters. The resulting frequency histograms of the sorted data were then mathematically modeled herein using the three types of Johnson distributions: bounded, lognormal, and unbounded. These provided a reasonably good fit for all six AE parameter distributions for each of the five …

An Intelligent System For Monitoring The Microgravity Environment Quality On-Board The International Space Station, Paul P. Lin, Kenol Jules

Mechanical Engineering Faculty Publications

An intelligent system for monitoring the microgravity environment quality on-board the International Space Station is presented. The monitoring system uses a new approach combining Kohonen's self-organizing feature map, learning vector quantization, and a back propagation neural network to recognize and classify the known and unknown patterns. Finally, fuzzy logic is used to assess the level of confidence associated with each vibrating source activation detected by the system.

Adaptive Harmonic Balance Method For Unsteady, Nonlinear, One-Dimensional Periodic Flows, Raymond C. Maple

Theses and Dissertations

A new adaptive split-domain harmonic balance computational fluid dynamics (CFD) method is developed to solve highly nonlinear time-periodic flows such as those found in turbomachinery. The basic harmonic balance CFD method transforms an unsteady time-periodic problem into a steady-state problem by assuming a solution in the form of a Fourier series in time. The new method employs a unique multi-domain split-operator solution technique to remove a large-series stability restriction present in previous harmonic balance CFD approaches. In addition, the new method adapts the frequency content to the flow, starting with a small number of Fourier frequencies and augmenting the frequency …

Mean Performance Optimization Of An Orbiting Distributed Aperture By Warped Aperture Image Plane Comparisons, Timothy W. Parker

Theses and Dissertations

This work models the aggregate performance of satellite receiver formations functioning as orbiting interferometers as compared to filled apertures of similar geometries. These models facilitate selecting initial conditions for formations such that their control-free dynamics yield interferometry performance with minimal errors as compared to the filled apertures. The solution method draws on the dynamic models of an orbiting planar satellite formation to define the size and shape of a reference aperture and to define the degrees of freedom for the formation members. The paths of formation elements yield geometries for which the aggregate performance of the array of discrete receivers …

Struggles Of The ‘Father’, Aimee Dechambeau

Aimée L. deChambeau

Biographical account of Konstantin Eduardovich Tsiolkovsky, the father of Soviet cosmonautics.

Analysis For Cooperative Behavior Effectiveness Of Autonomous Wide Area Search Munitions, Sang M. Park

Theses and Dissertations

The purpose of this study is to investigate how a simulation model can accurately represent the performance of the autonomous wide area search munitions, and to find the effectiveness of the cooperative behavior on the autonomous munitions. Though it does not provide a practical solution for the development of the autonomous wide area search munitions, this research will show some meaningful allocations of the munitions tasks that are applicable to the development of the autonomous munitions. For the first phase, this thesis presents how accurately a simplified simulation model can represent a proposed weapon system by comparing the simulation results …

Transient Jet Interaction Force And Moment Reconstruction In Dynamic Wind-Tunnel Testing, Mark Edward Smith

Doctoral Dissertations

In recent years there has been an increased interest in understanding the effect of missile divert jets upon the pressure distribution on the surface of a missile. Missile divert jets are jets located near the missile center of mass and thrusting along a lateral axis of a missile. The firing of a divert jet perturbs the pressure dis- tribution and thus alters the aerodynamic force acting on the missile. This is the aerodynamic jet interaction e®ect. It is essential to characterize and understand this effect when designing robust missile autopilots.

Testing techniques for determining the transient jet interaction effect must …

Design And Integration Of A Display For A Low Cost Laser Altimeter For General Aviation Applications, Scott Edward Hutcheson

Masters Theses

This project began when Opti-Logic, a local manufacturer of laser rangefinders for military and sporting applications, expressed a desire to design an altimeter for General Aviation application to measure absolute altitude based on the laser range finder as a sensor. The sensor they chose was the RS400, which was originally designed for security applications. The purpose of this thesis was to aid Opti-Logic by designing and flight-testing an intuitive display for the laser altimeter. A Systems Engineering approach was used throughout the design process. A basic assumption in the design of the system is that a suitable laser sensor was …

The Correlation Of Pedal Position To Tail Rotor Power Requirement On The Oh-58a+, Kan-Wai Tong

Masters Theses

Every mechanical component has a finite failure life. Excessive usage of a component may cause damage. Therefore, life determination is essential to safe operation. Replacement of mechanical components prior to the end of useful life results in higher costs of maintenance. Monitoring rotating components is not always reliable or cost effective. This thesis attempts to solve this problem for a helicopter tail rotor. The development of an algorithm to calculate the loads on a component using stationary measurements can eliminate the need for rotating measurement equipment.

The purpose is to predict the tail rotor power requirement of a helicopter throughout …

Nebraska Initiative For Aerospace Research And Industrial Development (Niarid): Final Report, Brent D. Bowen, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 02-1

The Nebraska Initiative for Aerospace Research and Industrial Development (NIARID) was designed to accelerate the state’s efforts to expand its capacity, national competitiveness, and infrastructure in aerospace research and industry. The systemic goal of the NIARID was to strengthen Nebraska’s long-term ability to develop new, and strengthen current, aerospace research activities that increase the state’s national research competitiveness, foster sustainable growth in aerospace-related industry and the state’s economic development; complement the mission and activities of the Nebraska Space Grant Consortium (NSGC); and advance the goals of NASA and its enterprises. Funding from NIARID accelerated the establishment of …

Integration Of The Control Display Navigation Unit (Cdnu) Into The Ea-6b Block 89a Aircraft And Its Impact On Navigation Operations, Robert Donald Croxson

Masters Theses

This thesis was to evaluate the attributes of the recent modification and installation of the Control Display Navigation Unit (CDNU) into the EA-6B aircraft. The author conducted multiple ground and flight test events during a three year evaluation of the EA-6B Block 89A aircraft.

The Block 89A modification included an embedded Global Positioning System (GPS)/ Inertial Navigation System (INS) (EGI), enhanced functionality with the recent GPS system modification, and the ability to control the navigation, weapon, and communication on one control panel. This modification was an attempt to replace a failing attitude system and also allow for additional capability. The …

Sidestick Controllers During High Gain Tasks, Brian J. Goszkowicz

Masters Theses

This research attempts to demonstrate the feasibility of a sidestick controller in a high gain environment. The research is assembled from several historical precedents and various projects.

New technologies have re-ignited interest in the use of sidestick controllers for commercial and military aircraft. There are many advantages and disadvantages utilizing a sidestick in fighter aircraft. Many pilots prefer the feel of a centerstick controller and the designer only needs to develop a few sets of command gradients or gearings to produce adequate handling qualities. However, centersticks require more cockpit room due to their larger size and range of motion. Consequently, …

Sum Normal Optimization Of Fuzzy Membership Functions, Daniel J. Simon

Electrical and Computer Engineering Faculty Publications

Given a fuzzy logic system, how can we determine the membership functions that will result in the best performance? If we constrain the membership functions to a certain shape (e.g., triangles or trapezoids) then each membership function can be parameterized by a small number of variables and the membership optimization problem can be reduced to a parameter optimization problem. This is the approach that is typically taken, but it results in membership functions that are not (in general) sum normal. That is, the resulting membership function values do not add up to one at each point in the domain. This …

Implementation Of The Digital Communication System In The F/A-18 Aircraft, Gregory D. Bigalk

Masters Theses

The F/A-18 Hornet is a Navy/Marine Corps carrier-based strike/fighter built by the Boeing Company. The Hornet is a dual role aircraft designed to have all weather intercept and ground attack capabilities. The purpose of this study was to examine the Variable Message Format (VMF) communications capability, integration compatibility and technical suitability of the RT-1824(C) ARC-210 radio as integrated into the F/A-18 aircraft. Normally, this aircraft would utilize two ARC-210 voice capable only RT-1556 radio sets designated Comm 1 and Comm 2. Comm 1 is switchable between an upper AS-4129/ARC antenna and lower AS-3557/A antenna. Comm 2 utilizes a separate lower …

Evaluation Of A Two-Way Datalink For Airborne Surveillance Of And Communication With A Remotely Operated Aircraft Operating In The National Airspace System, Timothy R. Clark

Masters Theses

The purpose of this study is to examine the use of a two-way digital datalink to implement the airborne surveillance and communication functions with a Remotely Operated Aircraft in the National Airspace System. These Air Traffic Control functions are currently implemented using primary and secondary radar systems for airborne surveillance, and radio transmissions for voice communications.

The present Air Traffic Control system was examined, as well as existing datalink technologies and surveillance and communication equipment. Remotely Operated Aircraft are currently employed almost exclusively by the military, and operational experience in the National Airspace System is very limited. Several key military …

A Study Of The Chemistry Between Fast Atomic Oxygen And Silver-Coated Qcm Crystals, Juan Carlos Valer

Masters Theses

Atomic Oxygen (AO) is the main constituent of Low Earth Orbit (LEO), and it is responsible for chemical reactions on spacecraft materials that may degrade the performance or terminate the usefulness of them, and eventually accelerate the end of the life of the vehicle. This situation has make it clear the need to simulate the AO flux of LEO in a ground laboratory, to better understand the mentioned interactions.

MSRI and a UTSI team lead by Dr. Frank Collins have heavily modified an atomic oxygen generator originally fabricated by Dr. Gar Hoflund that promises to at least duplicate the AO …

Numerical Studies Of Transition For Flows Around Multi-Element Airfoils, Fengjun Liu

Dissertations

The transition of flows around a multi-element airfoil has been numerically studied using RANS with a k - e two-equation transition model, LST and DNS. The transition model uses an effective eddy-viscosity by coupling an intermittence-like correction to a turbulence eddy-viscosity that can be obtained via solving a parent k - e turbulence model. The transition model is truly predictive in that it is able to predict transition onset locations without having to specify prior knowledge of the targeted transition process. The predicted transition onset locations for all the cases studied were compared with the measured data. The results suggest …