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Numerical Modeling Of Free Surface And Rapid Solidification For Simulation And Analysis Of Melt Spinning, Chunbai Wang 2010 Iowa State University

Numerical Modeling Of Free Surface And Rapid Solidification For Simulation And Analysis Of Melt Spinning, Chunbai Wang

Graduate Theses and Dissertations

The work provides methodologies for studying, designing, and optimizing melt spinning processes of fiber manufacture. Amorphous metallic materials can be created through melt spinning processes, in which a highly spinning wheel undercools a jet of molten metal or alloy below the equilibrium melting and the nucleation temperatures. Free-jet melt spinning employs a larger nozzle-wheel gap compared to planar flow casting. The instability of melt pool formation in a free-jet melt spinning will allow the variability of ribbon production. In general, a stable delivery of amorphous materials depends simultaneously on various control parameters, such as wheel speed, molten flow viscosity, surface ...


Frequency And Load Mode Dependence Of Vibrothermography, Wenjun Zhang 2010 Iowa State University

Frequency And Load Mode Dependence Of Vibrothermography, Wenjun Zhang

Graduate Theses and Dissertations

Vibrothermography is a method for finding cracks based on the heat generation due to vibration-induced rubbing of the crack surfaces. This technique has shown substantial promise for industrial use finding flaws in gas turbine parts, but the underlying physics remains unclear. Two long standing questions are the dependence of crack heating on excitation frequency, and the dependence of crack heating on loading mode (normal vs shear). With our broadband excitation system, we are able to excite the specimen at different resonances, and correlate the heating with dynamic vibrational stress and frequency of vibration. By exciting the specimen in different modes ...


Modeling Of Pulse-Echo Inspections Of Multi-Layer Panels Containing Delaminations, Nathaniel Lawrence Richter 2010 Iowa State University

Modeling Of Pulse-Echo Inspections Of Multi-Layer Panels Containing Delaminations, Nathaniel Lawrence Richter

Graduate Theses and Dissertations

To meet the needs of counter insurgency operations the armor of tanks need to be lighter. This is accomplished by using a combination of materials: metals, composites, and ceramics. This multi-material composite armor using any combination of the above materials will need to be inspected for manufacturing error, shipping damage, and combat damage. Nondestructive inspection, particularly ultrasonic inspection, has a long history of successfully inspecting thick composite structures.

To more easily develop inspection plans for many layered composites a computational model would be of use. A model of this type would need to have the ability to account for multiple ...


Configurational Effect On Dust Cloud Formation And Brownout, Sayan Ghosh 2010 Iowa State University

Configurational Effect On Dust Cloud Formation And Brownout, Sayan Ghosh

Graduate Theses and Dissertations

Rotorcraft brownout is in-flight visibility restriction caused by clouds of sand and dust particles during landing, take off, and near ground flight operations in arid desert terrain. This complex phenomenon is caused by entrainment of dust, sand, and ground particles by rotor downwash and is compounded by fuselage geometry and its orientation with respect to the ground. Nonlinear forces and moments on the fuselage, and highly unsteady wind velocities are common in near ground operations and play a significant role in the behavior of the particulate clouds that create the brownout condition.

In this current research, an efficient Computational Fluid ...


Microstructure Investigation Of Al-Rich Titanium Aluminum Alloys, David Pham 2010 University of Texas at El Paso

Microstructure Investigation Of Al-Rich Titanium Aluminum Alloys, David Pham

Open Access Theses & Dissertations

The microstructures of Ti-Al alloys with 70-80 wt% Al were investigated. Aluminum wire (99.999%) and TiH2 powder (99.7%) were used to produce the sample compositions inside a vertical tube furnace at 1600oC in an Ar atmosphere. Argon is purified through a dehumidification and deoxidation system. Magnesium perchlorate Mg(ClO4)2 acts as a desiccant and titanium sponge pulls oxygen from the Ar in furnaces operating at 800oC and 750oC. X-ray diffraction and an optical microscope are used to identify phases and compositions


Development Of A Micro-Catbed For Miniature Thrusters, Chance Paul Garcia 2010 University of Texas at El Paso

Development Of A Micro-Catbed For Miniature Thrusters, Chance Paul Garcia

Open Access Theses & Dissertations

The goal of this work is to develop a micro catalytic bed for miniature thrusters. A test bed was constructed for experimental testing to characterize several parts of the micro catalytic bed. The reactant fluid studied is 90% Hydrogen Peroxide (H2O2) by weight. Three different cross sectional area designs were tested to determine decomposition efficiency, temperature reaction propensity, optimum flow rate, and temperature distribution across each bed. The products of decomposition were condensed to measure the oxygen released from decomposition. The results will be used to develop the basis for a micro catalytic bed design to implement into future miniature ...


Experimental Data Analysis Of The Vortex Structures In The Wakes Of Flapping Wings, Kai Wang, Umesh Vaidya, Baskar Ganapathysubramanian, Hui Hu 2010 Iowa State University

Experimental Data Analysis Of The Vortex Structures In The Wakes Of Flapping Wings, Kai Wang, Umesh Vaidya, Baskar Ganapathysubramanian, Hui Hu

Mechanical Engineering Conference Presentations, Papers, and Proceedings

The objective of this paper is to compare the existing methods and develop novel approaches for the experimental data analysis of the unsteady aerodynamics of the flapping wing microaerial-vehicle. These methods are developed for the purpose of identification of the beneficial dynamics and for the development of reduced order models for control design. We first employ Proper Orthogonal Decomposition (POD) method for the data analysis of the PIV measurements in the wakes of piezoelectric flapping wings. The basic idea behind POD based data analysis method is to decompose the time series snapshots of PIV measurements into high energy, POD, modes ...


Constrained Optimal Orbit Design For Earth Observation, Sharon D. Vtipil 2010 Old Dominion University

Constrained Optimal Orbit Design For Earth Observation, Sharon D. Vtipil

Mechanical & Aerospace Engineering Theses & Dissertations

The purpose of this dissertation is to demonstrate use requirements for a satellite observation mission can be used to determine a constrained optimal orbit based on observation site requirements, observation condition restraints, and sensor characteristics. The typical Earth observation satellite is first designed according to an appropriate orbit; then the observation requirements are used to develop a target schedule. The new design process outlines the development of the appropriate orbit by incorporating user requirements at the forefront of mission planning, not after an orbit has been selected. This research shows how to map the user requirements into constraints for the ...


Orbit Options For An Orion-Class Spacecraft Mission To A Near-Earth Object, Nathan C. Shupe 2010 University of Colorado at Boulder

Orbit Options For An Orion-Class Spacecraft Mission To A Near-Earth Object, Nathan C. Shupe

Aerospace Engineering Sciences Graduate Theses & Dissertations

Based on the recommendations of the Augustine Commission, President Obama has proposed a vision for U.S. human spaceflight in the post-Shuttle era which includes a manned mission to a Near-Earth Object (NEO). A 2006-2007 study commissioned by the Constellation Program Advanced Projects Office investigated the feasibility of sending a crewed Orion spacecraft to a NEO using different combinations of elements from the latest launch system architecture at that time. The study found a number of suitable mission targets in the database of known NEOs, and predicted that the number of candidate NEOs will continue to increase as more advanced ...


Solar Sail Attitude Dynamics And Coning Control: On Developing Control Methods For Solar Sail Coning At Orbit Rate To Attain Desired Orbital Effects, Farheen Rizvi 2010 University of Colorado at Boulder

Solar Sail Attitude Dynamics And Coning Control: On Developing Control Methods For Solar Sail Coning At Orbit Rate To Attain Desired Orbital Effects, Farheen Rizvi

Aerospace Engineering Sciences Graduate Theses & Dissertations

In this thesis, a control method is developed for the solar sail normal vector to trace a desired circular coning trajectory at orbit rate. The coning trajectory is defined in the local vertical local horizontal (LVLH) frame and the coning occurs about an LVLH equilibrium sail attitude. Past research has shown that sail attitude equilibria exist in the LVLH frame under the influence of aerodynamic, gravity gradient and solar torques. Precession of the sail normal from these equilibria causes sail normal coning about that equilibrium attitude. If the coning happens at orbit rate, wide variety of orbital effects can be ...


Finite Element Modeling And Optimization Of High-Speed Aerothermoelastic Systems, Micah A. Howard 2010 University of Colorado at Boulder

Finite Element Modeling And Optimization Of High-Speed Aerothermoelastic Systems, Micah A. Howard

Aerospace Engineering Sciences Graduate Theses & Dissertations

The design of supersonic and hypersonic aerospace vehicles is by nature a multi-disciplinary problem requiring the close integration of compressible fluid dynamics, heat transfer, and structural dynamics. The transient flow around the body must be accurately characterized in order to assess its effect on the thermal and structural responses; conversely, the thermal and structural behavior may significantly alter the aerodynamic performance. The core of this dissertation effort is concerned with the development and demonstration of an analysis and design capability for the aerothermoelastic behavior of high-speed aerospace vehicles. This nominally involves coupling of the compressible Navier-Stokes equations for the fluid ...


Assessing Feasibility Of Electrochromic Space Suit Radiators For Reducing Extravehicular Activity Water Consumption, Jonathan Glen Metts 2010 University of Colorado at Boulder

Assessing Feasibility Of Electrochromic Space Suit Radiators For Reducing Extravehicular Activity Water Consumption, Jonathan Glen Metts

Aerospace Engineering Sciences Graduate Theses & Dissertations

Water consumption for space suit thermal control is a limiting factor on long-term space exploration missions. A concept is proposed for an integrated, flexible suit radiator using infrared electrochromic materials for modulated heat rejection from the suit. Properties of electrochromic materials, the structure of electrochromic devices, and relevant heat transfer processes are presented as background information. Analytical methods are employed to bound theoretical performance and determine required emissivity ranges for lunar surface operations. Case studies are presented incorporating Apollo program and Advanced Walkback Test metabolic and environmental data to estimate sublimator water consumption and hypothetical water savings with the electrochromic ...


Two-Craft Coulomb Formation Study About Circular Orbits And Libration Points, Ravi Kishore Inampudi 2010 University of Colorado at Boulder

Two-Craft Coulomb Formation Study About Circular Orbits And Libration Points, Ravi Kishore Inampudi

Aerospace Engineering Sciences Graduate Theses & Dissertations

This dissertation investigates the dynamics and control of a two-craft Coulomb formation in circular orbits and at libration points; it addresses relative equilibria, stability and optimal reconfigurations of such formations. The relative equilibria of a two-craft tether formation connected by line-of-sight elastic forces moving in circular orbits and at libration points are investigated. In circular Earth orbits and Earth-Moon libration points, the radial, along-track, and orbit normal great circle equilibria conditions are found. An example of modeling the tether force using Coulomb force is discussed. Furthermore, the non-great-circle equilibria conditions for a two-spacecraft tether structure in circular Earth orbit and ...


Earth's Outer Radiation Belt Electrons: Identifying Sources, Improving Forecasts, And A New Particle Detector Design, Drew Lawson Turner 2010 University of Colorado, Boulder

Earth's Outer Radiation Belt Electrons: Identifying Sources, Improving Forecasts, And A New Particle Detector Design, Drew Lawson Turner

Aerospace Engineering Sciences Graduate Theses & Dissertations

Earth's outer radiation belt is a highly dynamic region composed primarily of relativistic electrons, which can pose a threat to spacecraft and astronauts. Despite decades of acquiring data and conducting research, the exact mechanisms and relative importance of outer belt electron source, loss, and transport processes are still not fully understood. Here, I follow the full cycle of outer belt electron data, from acquiring it in situ to analysis and practical use. I start by discussing a new instrument designed to measure relativistic particles from a low-cost picosatellite in low-Earth orbit, which will provide complementary data to NASA's ...


Characterizing Longitude-Dependent Orbital Debris Congestion In The Geosynchronous Orbit Regime, Paul V. Anderson 2010 University of Colorado Boulder

Characterizing Longitude-Dependent Orbital Debris Congestion In The Geosynchronous Orbit Regime, Paul V. Anderson

Aerospace Engineering Sciences Graduate Theses & Dissertations

The geosynchronous orbit (GEO) is a unique commodity of the satellite industry that is becoming increasingly contaminated with orbital debris, but is heavily populated with high-value assets from the civil, commercial, and defense sectors. The GEO arena is home to hundreds of communications, data transmission, and intelligence satellites collectively insured for an estimated 18.3 billion USD. As the lack of natural cleansing mechanisms at the GEO altitude renders the lifetimes of GEO debris essentially infinite, conjunction and risk assessment must be performed to safeguard operational assets from debris collisions.

In this thesis, longitude-dependent debris congestion is characterized by predicting ...


Analysis Of Wake Vortices Of A Medium Range Twin-Propeller Military Cargo Aircraft Using Statistically Designed Experiments, Burhan Sahin 2010 Old Dominion University

Analysis Of Wake Vortices Of A Medium Range Twin-Propeller Military Cargo Aircraft Using Statistically Designed Experiments, Burhan Sahin

Mechanical & Aerospace Engineering Theses & Dissertations

An experimental study was initiated to analyze the trajectories of the streamwise vortices behind the wing tip and flap of a medium range and propeller driven twin-engine military cargo aircraft. The model used for the experimental study was a generic, high wing and half model of a propeller driven aircraft and mounted within Old Dominion University's Low Speed Wind Tunnel where the wind tunnel flow speed was set to constant value of 9 m/sec. The main purpose of the study was to reach regression models for the motion and vorticity strength of both vortices under varying factors such ...


Active Control Of Shocks And Sonic Boom Ground Signal, Bedri Yagiz 2010 Old Dominion University

Active Control Of Shocks And Sonic Boom Ground Signal, Bedri Yagiz

Mechanical & Aerospace Engineering Theses & Dissertations

The manipulation of a flow field to obtain a desired change is a much heightened subject. Active flow control has been the subject of the major research areas in fluid mechanics for the past two decades. It offers new solutions for mitigation of shock strength, sonic boom alleviation, drag minimization, reducing blade-vortex interaction noise in helicopters, stall control and the performance maximization of existing designs to meet the increasing requirements of the aircraft industries. Despite the wide variety of the potential applications of active flow control, the majority of studies have been performed at subsonic speeds. The active flow control ...


Solution Approximation For Atmospheric Flight Dynamics Using Volterra Theory, Ashraf Mohammed Kandeel Omran 2010 Old Dominion University

Solution Approximation For Atmospheric Flight Dynamics Using Volterra Theory, Ashraf Mohammed Kandeel Omran

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation introduces a set of novel approaches in order to facilitate and enrich Volterra theory as a nonlinear approximation technique for constructing mathematical solutions from the governing relationships describing aircraft dynamic behavior. These approaches reconnect Volterra theory and flight mechanics research, which has not been addressed in the technical literature for over twenty years. Volterra theory is known to be viable in modeling weak nonlinearities, but is not particularly well suited for directly describing high performance aircraft dynamics. In order to overcome these obstacles and restrictions of Volterra theory, the global Piecewise Volterra Approach has been developed. This new ...


Numerical Investigation Of Aeroelastic Mode Distribution For Aircraft Wing Model In Subsonic Air Flow, Marianna A. Shubov, Stephen B. Wineberg, Robert Holt 2010 University of New Hampshire

Numerical Investigation Of Aeroelastic Mode Distribution For Aircraft Wing Model In Subsonic Air Flow, Marianna A. Shubov, Stephen B. Wineberg, Robert Holt

Mathematics & Statistics Scholarship

In this paper, the numerical results on two problems originated in aircraft wing modeling have been presented. The first problem is concerned with the approximation to the set of the aeroelastic modes, which are the eigenvalues of a certain boundary-value problem. The affirmative answer is given to the following question: can the leading asymptotical terms in the analytical formulas be used as reasonably accurate description of the aeroelastic modes? The positive answer means that these leading terms can be used by engineers for practical calculations. The second problem is concerned with the flutter phenomena in aircraft wings in a subsonic ...


Spacecraft Coating-Induced Charging: A Materials And Modeling Study Of Environmental Extreme, Michelle M. Donegan, Jennifer L. Sample, JR Dennison, R. Hoffman 2010 Johns Hopkins University

Spacecraft Coating-Induced Charging: A Materials And Modeling Study Of Environmental Extreme, Michelle M. Donegan, Jennifer L. Sample, Jr Dennison, R. Hoffman

All Physics Faculty Publications

As mankind reaches to explore extreme environments in space, the application of ceramics surface coatings is increasing. The 2005 mission concept for Solar Probe used a unique design to achieve the necessary thermal control for a very close approach to the solar corona, including the use of a highly refractory, electrically insulating ceramic coating over a carbon-carbon composite heat shield. The proposed trajectory takes the spacecraft from a Jovian fly-by to within 4 solar radii of the Sun, spanning 5 orders of magnitude in solar radiation and solar wind plasma density as well as spacecraft temperatures from <100 K to >2000 K. Using ...


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