Aerospace Engineering Commons^™

Load Interaction Effects On Fatigue Crack Growth, Stoyan Ivanov Stoychev

Dissertations

Load excursions, in the form of tensile and compressive overloads are known to produce interaction effects during subsequent constant amplitude loading. In this work, the fatigue crack growth and crack closure levels, under both constant amplitude and variable amplitude loading, are investigated in the aluminium-lithium alloy 2090-T84, and the aluminium alloys 2024-T351 and 7150-T651. The crack closure measurements were obtained using both a crack tip opening displacement (CTOD) gauge and a crack mouth opening displacement (CMOD) gauge.

Fatigue crack growth tests were performed on specimens of thickness 1.6mm, 3mm, 6mm and 14mm. Tests were performed at load ratios of 0.1 …

An Investigation Of Starting Techniques For Inward Turning Inlets At Flight Speeds Below The On-Design Mach Number, John D. Mack

Theses and Dissertations

The purpose of this study was to create and investigate starting techniques aimed at allowing complex, three-dimensional, inward-turning inlets to start by swallowing the shock wave associated with unstarted inlets. The techniques are rooted in supersonic diffuser theory and the Kantrowitz limit; they attempt to alleviate the over contraction that occurs in inward-turning inlets at flight speeds below the on-design Mach number. Five cases, three geometries at two flow conditions and the base non-modified inlet at the two flow conditions, were generated, and all were numerically simulated using a commercially produced numerical solver: CFD++. The simulations were computed using the …

Boundary Layer Control Of A Circular Cylinder Using A Synthetic Jet, Christopher K. Smith

Theses and Dissertations

Active control of flow around a circular cylinder at a sub-critical Reynolds number was studied experimentally. The flow was controlled by using a synthetic jet which ran span wise along the cylinder and emanated radially from the cylinder. The experiments were conducted over a two dimensional cylinder in a water tunnel at a Reynolds number of approximately 5800. Seven different jet locations and seven different jet oscillation frequencies were examined. Particle image velocimetry (PIV) was used for flow visualization. The synthetic jet proved to delay flow separation at a wide range of locations and oscillation frequencies. The greatest positive effect …

Design And Ground-Testing Of An Inflatable-Rigidizable Structure Experiment In Preparation For Space Flight, Chad R. Moeller

Theses and Dissertations

As the demand for larger space structures increases, complications arise including physical dimensions, weight, and launch costs. These constraints have forced the space industry to look for smaller, more lightweight, and cost-effective solutions. Future antennas, solar sails, sun shields, and other structures have the potential to be exponentially larger than their launch envelopes. Current research in this area is focused on the use of inflatable, rigidizable structures to reduce payload size and mass, ultimately reducing launch costs. These structures can be used as booms, trusses, wings, or can be configured to almost any simple shape. More complex shapes can be …

Characterization Of A Rotary Flat Tail As A Spoiler And Parametric Analysis Of Improving Directional Stability In A Portable Uav, Troy A. Leveron

Theses and Dissertations

The United States Air Force Research Lab, Munitions Directorate, Flight Vehicles, Integration Branch (AFRL/MNAV), has developed a flexible wing micro air vehicle (MAV) to be used with special tactics groups. In keeping with the requirement that this MAV be compact, previous research developed a rotatable tail mechanism which resulted in tail movement similar to that of a bird's tail. In this study the design of this tail was modified to produce a more storable vehicle. The redesign also allowed the tail to deflect upward to large angles, enabling the tail to be used as a spoiler. The aerodynamic effects of …

Study Of Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Erik K. Ross

Theses and Dissertations

The research project studied the benefits of Magnetogasdynamic (MGD) acceleration on a scramjet nozzle. MGD is a technology that relies on electromagnetic fields to extract and/or add energy to flow fields. The scramjet engine in the "AJAX" concept proposed by D.I. Brichkii et al. (2001) of St. Petersburg, Russia would utilize an MGD power generator in the diffuser user which could potentially provide electrical power for the aircraft support systems and an MGD accelerator in the nozzle of the engine. Using an AFRL/VAAC CFD code that was modified for MGD computations, this project investigated the effect conductivity and load factor …

Drag Estimates For The Joined-Wing Sensor Craft, Ryan L. Craft

Theses and Dissertations

This research studied the drag effects of the joined-wing sensor craft technology demonstrator being developed at the Air Force Research Laboratory (AFRL). Although many performance parameters have been studied and evaluated for this vehicle, to date no detailed drag estimates have been conducted for the AFRL configuration. Previous performance parameters of the aircraft have been estimated based solely on a constant lift-to-drag ratio assumption. Using the Air Vehicles Technology Integration Environment created by Dr. Maxwell Blair, and supplemented by MATLAB code, this study explored three different drag prediction methods to determine accurate estimates of both parasite and induced drag. The …

Experimental Investigation Into The Aerodynamic Ground Effect Of A Tailless Chevron-Shaped Ucav, Brett L. Jones

Theses and Dissertations

This experimental study adequately identified the ground effect region of an unmanned combat air vehicle (UCAV). The AFIT 3' x 3' low-speed wind tunnel and a ground plane were used to simulate the forces and moments on a UCAV model in ground effect. The chevron planform used in this study was originally tested for stability and control and the following extends the already existing database to include ground effects. The ground plane was a flat plate mounted with cylindrical legs. To expand the capabilities of the AFIT 3' x 3' low-speed wind tunnel, hot-wire measurements and flow visualization revealed an …

Parametric Study Of The Towline Shape Of An Aircraft Decoy, Tyler L. Richardson

Theses and Dissertations

Some of today's aircraft use decoys as a defense against enemy weapons. The decoy is towed behind the aircraft with the intention of attracting the weapon propagator by deception, trying to mislead the weapon into detecting it instead of the aircraft. An aircraft deploys a decoy via a towline extending out behind and below the aircraft. However, during some maneuvers, the towline moves up into the jet exhaust plume of the aircraft. The high temperatures of the exhaust can cause damage to the towline cable, ranging from disrupting data flow between the decoy and aircraft to severing the towline altogether. …

Can A 10cm Cube Picosatellite Have Any Real Application In Space?, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Can a 10cm Cube Picosatellite Have Any Real Application in Space?" from May 13, 2005.

Design Of A Prototype Model Aircraft Utilizing Propulsive Airfoil Technology, Richard L. Pepe

Renée Crown University Honors Thesis Projects - All

Researchers have considered the concept of a simple, compact aircraft for personal use for many years. To date, no effort has led to the development of a practical and affordable vehicle. The Computational Fluid Dynamics (CFD) Lab atSyracuseUniversity, however, has been researching a distributed propulsion technique, called propulsive airfoil technology, that has significant promise to meet the requirements for personal ownership of a small, hybrid road and air vehicle.

The propulsive airfoil concept is rooted in HVAC technology, utilizing a cross-flow fan (CFF) embedded into the trailing edge of a thick airfoil section, drawing in air from the top surface …

Modeling Interface Failure In Fiber-Composites, Andrew J. Craig

Renée Crown University Honors Thesis Projects - All

Interface failure has been studied in depth for more than the past twenty years due to its significant impact on the application of composite materials. The objective of this work is to investigate the role of the interface in the mechanical response of fiber-matrix composite materials subjected to an applied load. To do this, a single composite cylinder consisting of a rigid core, the fiber, and an elastic annulus, the matrix, with an interface of vanishing thickness separating them, is considered as the first step in what will later be representative of a composite material. Three non-linear, Needleman-type, force-separation relations …

Derivation Of A Numerical Method For Computing 3-D Magnetoplasmadynamic Flows In Thermodynamic Non-Equilibrium, Caroline CéCile Marcelle Liron

Master's Theses - Daytona Beach

Various models exist for the propulsion concept using magnetohydrodynamics (MHD). Various authors, such as Powell, Canupp, Candler, and MacCormack have dealt with issues of solving the magnetic field induction equations simultaneously with Navier-Stokes equations using Computational Fluid Dynamics (CFD). Although most authors deal with species non-equilibrium and thermal non-equilibrium, a new emphasis is set to study the impact of electrons with the electron energy and the electronic excitation energy, as well as a complex energy non-equilibrium.

This thesis presents the derivation of a numerical method for computing 3-D MHD flows for the purpose of modeling steady-state magnetoplasma …

Stanford Satellite & Polar Programs: Polar Technology Conference, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Stanford Satellite & Polar Programs: Polar Technology Conference" from April 23, 2005.

Studying The Troposphere, Stratosphere And Ionosphere Of The Earth, Per Hoeg

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Per Hoeg titled "Studying the Troposphere, Stratosphere and Ionosphere of the Earth" from April 7, 2005.

A New Use For Cubesats Utilizing Low Data Rate Downlinks: Stec2005, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "A New Use for CubeSats Utilizing Low Data Rate Downlinks: STEC2005" from April 6, 2005.

Damage Assessment And Strength Predictions In S-Glass/Epoxy Laminates Subjected To Low Energy Impact, Tuan-Khoi Dang Nguyen

Master's Theses - Daytona Beach

Composite materials have become one of the leading materials for manufacturing in the aerospace industry today. Compared to "conventional" aerospace metals, composites generally have higher strength-to-weight and stiffness-to-weight ratios, good fatigue and corrosion resistance and reduced parts count. However, like any other material, they also have disadvantages. They are inherently brittle and are thus prone to impact damage. Low energy/velocity impact damage, in particular, can be dangerous because the damage oftentimes goes undetected and can subsequently grow under load. Also known as barely visible impact damage (BVID), this area of concentration focuses on the small-scale damage that may be very …

Investigation Of A Highly Loaded, High Pressure Ratio Axial Turbine Stage For Industrial Applications, Amit Garg

Master's Theses - Daytona Beach

The turbine component of a gas turbine engine is the most costly component due to its complexity, and life requirements, given the harsh environment in which it is required to operate. Minimizing the number of stages can lead to significant savings in terms of development efforts, materials, and serviceable parts. This philosophy has led to a significant increase in the work demanded from the typical stage. In this work, a highly loaded axial turbine stage was designed for high power-output industrial applications using a comprehensive set of investigations, which included parametric studies, throughflow solutions, and 2D airfoil shapes. The design …

Fabrication And Compressive Yield Strength Of Open Cell Corrugated Cellular Solids, Jeong Ho Choi

Master's Theses - Daytona Beach

This thesis studied the fabrication and compressive yield strength of open cell corrugated cellular solids made from type 304 stainless steel. Test samples were made by corrugating woven wire meshes, then laminating these in a high temperature argon environment. Mesh sizes ranging from 9.5 pore/cm (24 pore/in) to 31.5 pore/cm (80 pore/in) with wire diameters ranging from 0.178 mm (0.007 in) to 0.3556 mm (0.014 in) were bonded using lithobraze 925 (Ag-7.5Cu-0.2Li) to create cellular solids having relative densities ranging from 0.0384 to 0.0920. Test samples were then quasistatically compressed to measure the stress-strain response. The stress level at 25% …

Modeling And Slew-Maneuver Control Of A Flexible Spacecraft, Jeremy E. Eckhart

Master's Theses - Daytona Beach

Slew-maneuver control problem is studied for a flexible spacecraft consisting of a rigid main body to which a long flexible appendage is attached. Nonlinear dynamical system models are developed using both distributed parameter modeling and discrete parameter modeling; these models are shown to be equivalent for appropriately chosen system parameters. Lyapunov-based nonlinear feedback controllers are designed for the control of rigid-body motion while suppressing the lowest frequency vibrational mode. In case of large-angle maneuvers, these nonlinear controllers are shown to outperform the linearization-based controllers including the filtered proportional-derivative (PD) controllers as well as the linear quadratic regulator (LQR) controllers. Finally, …

The Coupling Effect Of Interfacial Adhesion And Tensile Residual Stress On A Thin Membrane Adhered To A Flat Punch, Kai Tak Wan, Lior Kogut

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adhesion and residual stress play a critical role in the performance and reliability of microdevices, in particular, the cross bridge of RF microswitches. to investigate their combinatorial influences on thin films, an elastic model is constructed for a clamped circular membrane in contact with the planar surface of a rigid cylindrical punch. External force applied to the punch leads to thin film delamination and ultimately 'pull-off' at a critical non-zero contact radius. Characteristic trends of the mechanical responses were obtained for fixed load and fixed grips in terms of pull-off force, punch displacement and contact radius. It is shown that …

Use Of Picosatellites & Rovers For Space Science And Education, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Use of Picosatellites & Rovers for Space Science and Education" from April 1, 2005.

Shape Memory Alloy Applications On Control Of Thermal Buckling, Panel Flutter And Random Vibration Of Composite Panels, Xinyun Guo

Mechanical & Aerospace Engineering Theses & Dissertations

Shape Memory Alloy (SMA) has a unique ability to recover large prestrain (up to 8∼10% elongation for Nitinol, a typical SMA material) completely when the alloy is heated (e.g. aerodynamic heating) above the austenite finish temperature Af. An innovative concept is to utilize the large recovery stress by embedding the prestrained SMA in a traditional fiber-reinforced laminated composite plate, which is called SMA hybrid composite (SMAHC) plate. In this research, static thermal and aerothermal deflections, dynamic panel flutter and random response are investigated for traditional composite plates and SMAHC plates under combined aerodynamic, random and thermal loads by employing nonlinear …

A Computational Study Of Thermo-Fluid Dynamics Of Pulse Detonation Engines, Alberto Davila Urresti

Master's Theses - Daytona Beach

The purpose of this thesis is to use a transient Computational Fluid Dynamics computer code written in FORTRAN 90 for full reaction kinetics, to perform an analysis of the physical processes and chemical phenomena occurring on a single cycle of an ideal Pulse Detonation Engine (PDE) using a stoichiometric mixture of H₂ and O₂. A small zone of high pressure and temperature is used to initiate the detonation wave in the PDE. A simple case with no chemical reactions and the same PDE geometry and “computational spark” is also tested. The speed of the wave relative to …

A Systematic Method For Characterizing The Elastic Properties And Adhesion Of A Thin Polymer Membrane, Bing Feng Ju, Yang Ju, Masumi Saka, Kuo Kang Liu, Kai Tak Wan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The elastic properties and adhesion of a thin silicone rubber membrane have been characterized. an effective instrumentation embodying a video-enhanced microscope, which meets force and displacement resolution of 0.1μN and 10 nm, was developed. It provides the capability of simultaneously measuring both the applied force and the resultant displacement of the thin polymer membrane. a linear theoretical elastic solution was applied to quantitatively interpret the measured central deflection of the membrane under a circular concentrical load. Young's modulus of the membrane can be easily determined once the applied force and the central deflection, together with the essential dimensions, are known. …

Development Of A Higher-Order Upwind Algorithm For Compressible Fluid Flow, Barry A. Croker

Theses and Dissertations

A global fourth-order solution method that incorporates compact differencing with Roe's approximate Riemann solver was investigated. This method was incorporated into a one-dimensional numerical simulation of the compressible Euler equations, and applied to a one-dimensional shock tube problem. The method was also extended to two dimensions, and applied to a two-dimensional shock tube problem and an advecting vortical structure problem on both rectilinear and curvilinear meshes. The results were compared to a third-order Roe scheme and a fourth-order compact difference scheme. An order of accuracy determination showed that it has an order of accuracy somewhere near fourth order, with absolute …

Evaluation Techniques For Determining Damping Mechanisms On Titanium Plates, Kyle S. Allen

Theses and Dissertations

High cycle fatigue (HCF) is the single largest cause of component failure for all modern military gas turbine engines. Hard coatings, such as magnesium aluminate spinel, have been found to provide significant damping properties. Past studies have had difficulties isolating the contributions of these hard coating damping layers from other damping mechanisms. This study explored techniques for assessing the contribution of different damping mechanisms on titanium plates during vibration testing. The study investigated 2nd bend and 2-stripe modes. Two different specimen sizes were tested in both a clamped-free-free-free and free-free-free-free condition. Specimens were tested at varying pressures. Increases in pressure …

Characterization Of Upstream Mixing Cavities And A Downstream Combustion Cavity In Supersonic Flow, Adam P. Quick

Theses and Dissertations

A key area of study in air-breathing hydrocarbon-fueled scramjet combustors is the characterization of cavity-based fuel injection and flame holding. One issue concerns oscillatory disturbances caused by trapped vortices in the main flame holder cavity as a fuel-air mixing enhancement technique. Previous research demonstrates that oscillatory disturbances can be carried downstream via the shear layer and alter the oscillatory characteristics of a downstream cavity. This study investigates the mixing effectiveness of three upstream direct-fueled mixing cavities as well as the effect on the oscillatory behavior of the downstream combustion cavity by the upstream mixing cavity. The three upstream mixing cavities …

Boundary Layer Flow Control Using Plasma Induced Velocity, Brian E. Balcer

Theses and Dissertations

An examination of the effects of plasma induced velocity on boundary layer flow was conducted. A pair of thin copper film electrodes spanned the test section, oriented at thirty degrees from normal to the free stream flow. An adverse pressure gradient was imposed over the electrode configuration using a pressure coefficient profile similar to that associated with suction side of a Pac-B low pressure turbine blade. In addition, suction was applied to keep flow attached on the upper wall, inducing separation over the electrode. The electrode is supplied by an AC source at three different power levels with the free …

Controlling Sideslip Angle To Reduce The Radar Exposure Of A Tactical, Rotary Winged Uav, Jonathan D. Bulseco

Theses and Dissertations

This work investigates another way of contributing to the radar minimization solution for air vehicles in a threat environment. While much research has been conducted on structural solutions to radar exposure minimization, not much work has been done in the area of using control to continuously assess and present the smallest radar cross section of an air vehicle to oncoming threat radar systems by changing the aircraft's orientation. This work looks at the application of sideslip/beta angle feedback control of an unmanned helicopter to minimize radar cross section exposure in a hostile radar environment. A new way of controlling aircraft …