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The Modal Solution To The Moon's Orbit Using Canonical Floquet Perturbation Theory, Kurt A. Vogel
The Modal Solution To The Moon's Orbit Using Canonical Floquet Perturbation Theory, Kurt A. Vogel
Theses and Dissertations
Using the restricted three body problem, the equations of motion EOM and Hamiltonian are computed for the moons orbit in physical variables. A periodic orbit is found in the vicinity of the moons orbit, and classical Floquet theory is applied to the periodic orbit to give stability information and the complete solution to the equations of variation. Floquet theory also supplies a transformation from physical variables to modal variables. This transformation to modal variables is made canonical by constraining the initial transformation matrix to be symplectic. Actual lunar data is used to calculate the modes for the real moons orbit. …
Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gregory J. Schiller
Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gregory J. Schiller
Theses and Dissertations
The purpose of this thesis is to apply moving-bank multiple model adaptive estimation and control MMAEMMAC algorithms to an actual space structure SPICE being examined at Phillips Laboratory at Kirtland AFB, NM. The structure consists of a large platform and a smaller platform connected by three legs in a tripod fashion. Kalman filtering and LQG control techniques are utilized as the primary design tool. Implementing a bank of filters increases the robustness of the LQG controller when uncertainties exist in the system model, whereas the moving bank is utilized to reduce the computational load. Several reduced-order models are developed from …
Static Fracture Behavior Of A Ceramic Matrix Composite At Elevated Temperatures, David M. Agins
Static Fracture Behavior Of A Ceramic Matrix Composite At Elevated Temperatures, David M. Agins
Theses and Dissertations
This study investigated systematically the damage initiation damage progression, and failure modes of a ceramic matrix composite, Nicalon/CAS, when loaded in tension at elevated temperatures in the presence of air. A cross-ply lay-up, [0/90]2s, was studied. The primary means of analysis were stress-strain data taken during monotonic and incremental load tests and crack density assessments. Testing was conducted at room temperature 700°C, and 850°C. The stress-strain response was consistent for monotonic and incremental loading, except for a decrease in failure load at the elevated temperatures. Initial damage progression was also consistent, but the damage leading to failure and …
Analysis Of The Effects Of Wake Passage On Heat Transfer In A Linear Turbine Cascade, Kevin S. Allen
Analysis Of The Effects Of Wake Passage On Heat Transfer In A Linear Turbine Cascade, Kevin S. Allen
Theses and Dissertations
This study investigated the effect of wake passage on the heat transfer in a linear turbine cascade. The apparatus used was the Air-Force Institute of Technology linear Turbine Cascade Test Facility (TCTF). The TCTF was fitted with a be Pulley system to facilitate a series of translating bars. The bars, when passed d upstream of the cascade, created a series of wakes. The parameters varied were freestream model Reynolds number and bar conditions, i.e. , bars in, bars out, and bar passing frequency. One blade in the TCTF was instrumented to allow pressure and temperature measurements at discrete points on …
Evaluation Of A Concentration Probe For Application In A Supersonic Flow Field, John S. Alsup
Evaluation Of A Concentration Probe For Application In A Supersonic Flow Field, John S. Alsup
Theses and Dissertations
Aspirating, concentration probes are used to measure binary gas concentrations in a supersonic flow. In the past, a tank discharge method has been used to calibrate concentration probes. An alternate calibration method has been developed and tested on a probe in a steady, subsonic/sonic flow. This study evaluated the calibration and performance of a concentration probe in a steady, supersonic flow over a range of mixture ratios of air and helium. The results of this study and a comparison of the two calibration methods are presented.
A Numerical Study Of High-Speed Missile Configurations Using A Block- Structured Parallel Algorithm, Douglas C. Blake
A Numerical Study Of High-Speed Missile Configurations Using A Block- Structured Parallel Algorithm, Douglas C. Blake
Theses and Dissertations
A numerical analysis of the aerodynamic phenomena associated with the high-speed flight of a sharp-nosed, four-finned, high-fineness ratio missile using a block-structured, parallel computer algorithm is presented. The algorithm, PANS-3EM, utilizes a second-order-accurate, shock-capturing, Total Variation Diminishing scheme and incorporates a Baldwin-Lomax turbulence model. PANS-3EM allows for extreme flexibility in the choice of computational domain decomposition and computing machine of implementation. Developmental work consists of conceptualization and verification of the algorithm as well as parallel performance and scalability studies conducted on a variety of computing platforms. Using PANS-3EM, the aerodynamic characteristics of the missile are investigated. Drag and pitching moment …
Investigation Of Tension-Compression Fatigue Behavior Of A Cross-Ply Metal Matrix Composite At Room And Elevated Temperatures, Elizabeth A. Boyum
Investigation Of Tension-Compression Fatigue Behavior Of A Cross-Ply Metal Matrix Composite At Room And Elevated Temperatures, Elizabeth A. Boyum
Theses and Dissertations
This research, the first load-controlled tension-compression fatigue testing to be performed on a MMC, extends the existing knowledge of MMC fatigue damage mechanisms to include the tension compression loading condition. To accomplish this, a (0/90)2, SCS-6/Ti-15-3 laminate was subjected to tension- tension fatigue at room temperature, and tension-compression fatigue at both room temperature and 427°C. Stress and strain data was taken to evaluate the macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanic level. On a maximum applied stress basis, the room temperature tension-tension specimens had longer fatigue lives than the room …
Wake Passage Effects On The Losses In A Linear Turbine Cascade, James A. Braunschneider
Wake Passage Effects On The Losses In A Linear Turbine Cascade, James A. Braunschneider
Theses and Dissertations
A linear turbine cascade was used to investigate the effects of wake passage due to stator-rotor interaction. The wakes were modeled by passing 1.98 mm (0.078 in) diameter bars upstream of a linear cascade blade row. Total pressure loss coefficients, mass averaged total pressure loss coefficients and velocities were used to characterize the effects of wake passage. Bar passing frequencies of 80, 160, 320 bars/sec were tested. These frequencies were tested, with the bars at 6.35 mm (0.25 in) intervals and at two Reynolds numbers, 341, 000 and 45,5000 Bar spacings of 12.7 mm (0.5 in), and 89 mm (3.5 …
Off-Design Performance Of Crenulated Blades In A Linear Compressor Cascade, Michael J. Costello
Off-Design Performance Of Crenulated Blades In A Linear Compressor Cascade, Michael J. Costello
Theses and Dissertations
The effects of using compressor blades with a crenulated (notched) trailing edge in a low aspect ratio (AR= 1) linear compressor cascade at four incidence angles (-1.08°, +4.49°, +9.32° and +12.44°) were investigated. Blade performance and wake mixing characteristics for crenulated blades were compared with similar data for blades with a straight trailing edge. A seven-bladed cascade was operated with a flow Mach number of 0.4 and a blade chord Reynolds number of 4.1 (10)5. The diffusion factor ranged from 0.22 to 0. 42 and strong three-dimensional flow effects were present. Total pressure losses were measured with a …
Development And Implementation Of A Scramjet Cycle Analysis Code With A Finite-Rate-Chemistry Combustion Model For Use On A Personal Computer, Clarence F. Chenault
Development And Implementation Of A Scramjet Cycle Analysis Code With A Finite-Rate-Chemistry Combustion Model For Use On A Personal Computer, Clarence F. Chenault
Theses and Dissertations
This study compared the performance of an equilibrium combustion model to a finite-rate-chemistry combustion model for a fixed geometry Scramjet flying at the flight conditions of Mach 12, 15, and 18 with a constant dynamic pressure of 50,000 Pa. An integrated PC-based code, developed specifically for this study, models the combustor as an equilibrium combustion process or as finite-rate-chemistry combustion process. This integrated program is based on two existing programs, Ramjet Performance Analysis (RJPA) and 3 STREAM. The effects of mixing schedule, combustor length, and combustor exit area were investigated. The results of this study indicate that inefficient mixing is …
The Effect Of Cutout Dimensionality On The Collapse Characteristics Of Cylindrical Composite Shells Of Varying Thickness, John C. Del Barga
The Effect Of Cutout Dimensionality On The Collapse Characteristics Of Cylindrical Composite Shells Of Varying Thickness, John C. Del Barga
Theses and Dissertations
This study involved a numerical and experimental investigation of the (geometric instability of graphite/epoxy cylindrical panels with free vertical edges undergoing axial compression. Symmetric quasi-isotropic laminates with five different size centralized cutouts, were investigated for two axial lengths of panels and three thicknesses. The study compared experimental data to results from SHELL, a geometrically nonlinear finite-element program which incorporates a parabolic transverse shear strain distribution through the thickness. The research verified that the SHELL program will provide good predictions of the collapse characteristics of a panel with large cutouts of varying dimensions undergoing large displacements and rotations. The best correlation …
Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel
Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel
Theses and Dissertations
This study investigated the effects of embedding optical fibers into advanced composite materials. This combination was meant to simulate 'smart structures' that have been shown to sense several different variables in the composite including strain, temperature, and damage. A laminate orientation taken from an existing aircraft structure was used to fabricate sixteen groups of specimens which were subjected to compression testing in an IITRI fixture to determine the ultimate compressive strength and modulus of elasticity. Ten of these groups were fabricated with optical fibers while the other six were control groups and contained no optical fibers. This study showed that …
Comparison Of The Dynamic Behavior Of Composite Plates And Shells Incorporating Green's Strain Terms With The Von Karman And Donnell Models, Arthur E. Forral
Comparison Of The Dynamic Behavior Of Composite Plates And Shells Incorporating Green's Strain Terms With The Von Karman And Donnell Models, Arthur E. Forral
Theses and Dissertations
The dynamic collapse behavior of thin, composite cylindrical shells subjected to transverse point loads is considered. The dynamic behavior of the undamped cylindrical shells of varying radii is analyzed with a finite element formulation that incorporates all nonlinear Green's strain terms in the in-plane directions; transverse strains are linear and vary parabolically through the shell thickness. This formulation is denoted as the simplified large displacement/rotation (SLR) theory. Graphical representations are used extensively to examine dynamic behaviors not noted in similar research that utilized the DSHELL finite element code. Composite plate behavior is also explored. Comparison of the higher-order formulations to …
Analysis And Characteristics Of Compressor Stall Precursor Signals In Forward And Aft Swept High Speed Compressor, Bernard J. Frank
Analysis And Characteristics Of Compressor Stall Precursor Signals In Forward And Aft Swept High Speed Compressor, Bernard J. Frank
Theses and Dissertations
The stall characteristic of four single-stage transonic compressor rotors were investigated as they were throttled to stall. Forward-swept, backward-swept, and straight leading edge rotors were examined. Three methods of analysis (1) windowed power spectrum densities of pressure and spatial Fourier coefficients, (2) phase tracking analysis, and (3) system identification were used to identify the first appearance of modal waves and their accompanying frequencies in order to identify a stall warning time. A direct correlation between the amount of stall warning time and the shape of the compressor characteristic was found. Specifically, if the compressor characteristic had a significant period of …
Investigation Of Compressive Behavior For Metal Matrix Composites With A Circular Hole, Janet L. Gooder
Investigation Of Compressive Behavior For Metal Matrix Composites With A Circular Hole, Janet L. Gooder
Theses and Dissertations
This study investigated the notched and unnotched macromechanical response due to micromechanical behavior of [0/±45/90]S SCS-6/β 21 S and [0/90] 2S Sigma/β 21S subjected to static compressive loads at room temperature. The stress-strain behavior and mechanical response in the presence of a circular hole was examined. A clear description of the progressive nature of damage, which ultimately resulted in failure, was provided. The effect of elevated temperature was shown for SCS-6/β 21S. The ultimate compressive strength and elastic modulus were reported for both MMCs. Sigma/β 21S and SCS-6/β 21S were mildly notch sensitive at room temperature. Notch sensitivity of …
Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Under Strain Controlled Tension-Tension And Tension-Compression Loading, James J. Gudaitis
Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Under Strain Controlled Tension-Tension And Tension-Compression Loading, James J. Gudaitis
Theses and Dissertations
This stuidy investigates the fatigue response of a cross-ply [0/90]2s Nicalon/Calcium Aluminosillicate (Nicalcc/CAS) ceramic matrix composite at room temperature under strain controlled tension-tension and tension-compression fatigue loading. The primary objectives were to determine strain fatigue limits for both loading cases and to complete a fatigue life diagram (Δe-N) for all tests. Failure mechanisms were also studied. The average initial modulus value for this lay-up was 120 GPa. The ultimate tensile strain was 0.00988 mn/mm (285 MPa). Eight tests were conducted with maximum strains that ranged from 0.00300 mm/mm to 0.00722 mm/mm. The tension-tension fatigue limit was found to be …
A Study Of Graphite Peek Composite With Central Elliptical Holes Under Tension, Bill J. Lau
A Study Of Graphite Peek Composite With Central Elliptical Holes Under Tension, Bill J. Lau
Theses and Dissertations
This study investigated the stress-strain response and failure modes of Graphite/Polyetheretherketone (Gr/PEEK) tension specimens containing a central elliptical hole. Both experiments and finite element numerical analyses were conducted. Test specimens included seven layups and three hole geometries; three of each combination were tested. The holes consisted of an ellipse with major axis aligned with the load axis, an ellipse with major axis transverse to the load axis, and a circle. Strain gages were located adjacent to the hole and midway between the hole and tab on all specimens. Strain data was used to plot stress-strain response. The analysis utilized a …
Nonlinear Large Deformation Theory Of Composite Arches Using Truncated Rotations, Daniel A. Miller Ii
Nonlinear Large Deformation Theory Of Composite Arches Using Truncated Rotations, Daniel A. Miller Ii
Theses and Dissertations
This research has been directed toward capturing large cross sectional rotation during bending of composite arches. A potential energy based nonlinear finite element model that incorporates transverse shear strain was modified to include large bending rotations. Large rotation kinematics were derived in a vector format leading to nonlinear strain that was decomposed into convenient forms for inclusion in the potential energy function. Problem discretization resulted in a finite element model capable of large deformations. Riks method and displacement control solution techniques were used. Numerous problems and examples were compared and analyzed. Code vectorization and parallelization were briefly examined to improve …
Exploring Qdes As A Tool For Determining Limits Of Achievable Performance In Aircraft Design, Mark F. Reidinger
Exploring Qdes As A Tool For Determining Limits Of Achievable Performance In Aircraft Design, Mark F. Reidinger
Theses and Dissertations
This thesis explores the usefulness of a computer aided control design software package called QDES in determining the limits of achievable aircraft performance as it relates to controller capability. Modern aircraft, particularly fighters, are being designed to be statically unstable to enhance their maneuverability and performance. It is possible that the aircraft, although physically capable of a certain level of performance due to its engine/ airframe combination, may be uncontrollable up to this level. This study sought to develop a methodology to use QDES to make a preliminary analysis of an aircraft design to determine if there exists a controller …
Effects Of Crenulations On Three Dimensional Losses In A Linear Compressor Cascade, William L. Spacy Ii
Effects Of Crenulations On Three Dimensional Losses In A Linear Compressor Cascade, William L. Spacy Ii
Theses and Dissertations
An experimental investigation into the effect of compressor blade trailing edge geometry on three-dimensional flows in a linear cascade was conducted at the AFIT linear cascade test facility. Hot-wire/hot-film anemometry along with total pressure instrumentation was used to analyze crenulation generated vortices and their interaction with the three-dimensional flows in the cascade. The effects of this interaction on the performance parameters associated with the cascade were quantified. The results-indicate that wake mixing is better for crenulated trailing edges and that the precise geometry of the crenulations is critical to performance. One crenulation geometry was found to increase wake mixing while …
Optimal Control Design Advantages Utilizing Two-Degree-Of-Freedom Controllers, Michael J. Stephens
Optimal Control Design Advantages Utilizing Two-Degree-Of-Freedom Controllers, Michael J. Stephens
Theses and Dissertations
The purpose of this study was to investigate and describe the differences between a one-degree-of-freedom (1-DOF) controller, in which a controller is placed in a single location in the control loop, and a two-degree- of-freedom (2-DOF) controller, in which two separate controllers are designed -- one in the feedback loop and the other as a prefilter in the forward loop. The approach involved summarizing the major rules governing loop shaping for performance and robustness in the 1-DOF case and then extending the concepts to the 2-DOF case. H2 optimization was utilized to perform several types of SISO examples and …
Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperatures Under Tension-Tension Loading, Richard J. Tuznik
Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperatures Under Tension-Tension Loading, Richard J. Tuznik
Theses and Dissertations
A study was conducted which investigated the behavior of a Nicalon/ Calcium-Aluminosilicate (Nicalon/CAS) cross-ply [0/90]2S ceramic matrix composite at elevated temperatures under tension-tension fatigue loading. Tension-tension fatigue tests were performed with a load ratio of R = 0.10 and a frequency of 10 Hertz at 700°C and 850°C. These results were compared to results from a previous study conducted at room temperature. Material behavior and damage was recorded by fatigue life curves, elastic modulus' maximum and minimum strain, acetate replication techniques, and post-mortem fractography. Analysis of these results showed identical matrix dominated damage behavior at RT and 700°C. Ultimate …
A Numerical Determination Of Bifurcation Points For Low Reynolds Number Conical Flows, Larry K. Waters
A Numerical Determination Of Bifurcation Points For Low Reynolds Number Conical Flows, Larry K. Waters
Theses and Dissertations
It has long been established that supersonic flow over axisymmetric conical bodies at high angles of attack tend to develop a side force due to vortical asymmetry. One of the proposed reasons for the asymmetry is a bifurcation point in the solution of the Navier-Stokes equations. This study investigated the possible existence of a bifurcation point in the Navier-Stokes equations for subsonic flow. Newton's method, with gauss elimination, was used- to solve the steady-state, viscous, compressible Navier-Stokes equations in spherical coordinates assuming conical similarity.
Experimental Analysis Of Heat Transfer Characteristics And Pressure Drop Through Screen Regenerative Heat Exchangers, Jeffrey L. Wiese
Experimental Analysis Of Heat Transfer Characteristics And Pressure Drop Through Screen Regenerative Heat Exchangers, Jeffrey L. Wiese
Theses and Dissertations
This study investigated the effect on heat transfer and friction characteristics for screen regenerative heat exchangers with the screen thickness reduced by rolling. The experiments were performed on 250 and 325 mesh, 304 stainless steel screen using helium gas. Reynolds numbers, based on hydraulic radius, Re, were between 10 and 100. Both the Colburn factor, StPr2/3, and friction factor, f, decreased as the screen thickness was reduced. A correlation was found for predicting friction factor, f. The drag coefficient per screen remained nearly unchanged for thicknesses reduced not more than 30 percent. The decrease in Colburn factor was …
Electrical Properties Of P-Type Gainp2, Roy S. Calfas
Electrical Properties Of P-Type Gainp2, Roy S. Calfas
Theses and Dissertations
The GaInP2 n+—p junction diode has recently become important to the development of high efficiency GaInP2GaAs dual junction solar cells, which have a demonstrated air mass 1.5 conversion efficiencies in excess of 27. In order to study the effects of long term exposure to the space environment, the GaInP2 n+—p junction diodes were irradiated with a 1 MeV electron beam with a fluence of 1016 electrons/cm2. Since little is known about deep level defects traps in GaInP2, a deep level transient spectroscopy DLTS study was made to characterize the …
High Resolution Fourier Transform Absorption Spectrum Of 79Br2 B3Π(0U+) ← X1ΣG+, Robert E. Franklin
High Resolution Fourier Transform Absorption Spectrum Of 79Br2 B3Π(0U+) ← X1ΣG+, Robert E. Franklin
Theses and Dissertations
High Resolution Fourier Transform Spectroscopy has been conducted for the 79Br2 B3π(0u+) ← X1Σg+ system of 79Br2. A total of 64 vibrational levels, including v"= 0-3 and v' = 10-33, have been observed and assigned. Rotational levels as high as J=76 were observed. A global fitting routine has been developed to fit the rotational spectra to the Dunham Expansion. Using Bv and Dv for both the X and B state, rotational transitions were calculated to within 0. 02 cm-1. The expansions of …
Infrared Fluorescence Studies Of Electronic-To-Vibrational Energy Transfer In A Br2:No System, Michael R. Hawks
Infrared Fluorescence Studies Of Electronic-To-Vibrational Energy Transfer In A Br2:No System, Michael R. Hawks
Theses and Dissertations
Steady-state photolysis techniques were used to study electronic-to- vibrational energy transfer mechanisms from atomic bromine to nitric oxide. Molecular bromine was photodissociated by 488nm radiation to produce equal parts Br(2P1/2) and Br(2P3/2). Side fluorescence intensity from Br(2P1/2) at 2.7 µm and from NO (v=1 and 2) around 5.3 µm measured as a function of bromine pressure and nitric oxide pressure. The branching ratio collisional transfer into the first and second states of NO was determined, and previously reported rates for quenching of NO by molecular bromine were verified.
Characterization Of An Lcd For Use As A Programmable Phase Shifter To Produce A Single-Lobed Far-Field Pattern In A Phased Array, Gregory S. Kenyon
Characterization Of An Lcd For Use As A Programmable Phase Shifter To Produce A Single-Lobed Far-Field Pattern In A Phased Array, Gregory S. Kenyon
Theses and Dissertations
The liquid crystal display LCD from an inexpensive pocket television was converted to a spatial light modulator SLM for the purpose of altering the phase front of a ten element diode laser array to produce a single lobe far field pattern. Characterization of the SLM determined the amount of phase shift, amplitude modulation and polarization rotation properties. Nonuniformities within the phase shifter and insufficient phase shift prevented the formation of a single lobe. However, a very limited phase grating was created and analyzed. LCDs from inexpensive commercial pocket televisions were found unsuitable for use as phase shifting spatial light modulators.
Shock Wave Interaction With L-Shaped Structures, Richard C. Miller
Shock Wave Interaction With L-Shaped Structures, Richard C. Miller
Theses and Dissertations
This study investigated the interaction of shock waves with L-shaped structures using the CTH hydrodynamics code developed by Sandia National Laboratories. Computer models of shock waves traveling through air were developed using techniques similar to shock tube experiments. Models of L-shaped buildings were used to determine overpressures achieved by the reflecting shock versus angle of incidence of the shock front. An L-shaped building model rotated 45 degrees to the planar shock front produced the highest reflected overpressure of 9.73 atmospheres in the corner joining the two wings, a value 9.5 times the incident overpressure of 1.02 atmospheres. The same L-shaped …
The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch
The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch
Theses and Dissertations
Vertical Cavity Surface Emitting Lasers VCSELs are a type of semiconductor laser with a cavity oriented orthogonally to the planes of material growth. These lasers differ from conventional edge emitting lasers in several important ways. They have symmetric output beams and they are easily built into two dimensional arrays, making them very attractive as photonic components. The characteristic of interest in this thesis is polarization. While the asymmetric cavities of edge emitters exhibit a clear preference for light polarized in a particular direction, the cylindrically symmetric cavity of a VCSEL has no clear preference. Therefore, it should be relatively easy …