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Articles 9001 - 9030 of 11121
Full-Text Articles in Engineering
Efficiency And Pressure Loss Characteristics Of An Ultra-Compact Combustor With Bulk Swirl, James T. Radtke
Efficiency And Pressure Loss Characteristics Of An Ultra-Compact Combustor With Bulk Swirl, James T. Radtke
Theses and Dissertations
Research was conducted on a novel combustor design using a highly centrifugal loaded circumferential cavity to enhance flame speeds and lower mixing time to lower overall combustion time achieving improved efficiency and stability. This Ultra-Compact Combustor (UCC) is fed air with a bulk swirl, resembling gas leaving a compressor without the final set of compressor guide vanes to straighten the flow, at higher than normal Mach numbers for a combustor. The larger Mach numbers in the combustor do not cause a total pressure loss in excess of what Rayleigh theory would dictate for the given heat addition taking place within …
Catalytic Partial Oxidation Reforming Of Jp8 And S8, Thomas G. Howell
Catalytic Partial Oxidation Reforming Of Jp8 And S8, Thomas G. Howell
Theses and Dissertations
Catalytic partial oxidation (CPOX) reforming experiments were performed using a 10 kW Aspen Products Group, Inc. fuel processing prototype utilizing military logistic fuels JP8 and S8. S8 is a sulfur-free Fisher-Tropsch fuel, while JP8 is a multi-fuel blend, which could impact reforming efficiency, product distribution and byproduct production. Sulfur contained within the JP8 will adversely affect the product distribution; therefore, desulfurization beds, capable of removing up to 1000 ppm sulfur, were incorporated into the system. The catalyst used in the prototype is noble metal dispersed on cordierite monolith. The goal of this experiment was to evaluate the efficiency and product …
Effects Of Prior Aging On The Creep Response Of Carbon Fiber Reinforced Pmr-15 Neat Resin At 288°C In An Air Environment, Christopher A. Back
Effects Of Prior Aging On The Creep Response Of Carbon Fiber Reinforced Pmr-15 Neat Resin At 288°C In An Air Environment, Christopher A. Back
Theses and Dissertations
The mechanical response of carbon fiber reinforced PMR-15 neat resin with a ± 45 fiber orientation was investigated at 288 °C. Mechanical testing was performed on unaged specimens and specimens that were aged up to 1000 hours in an air environment. Tensile tests were performed to determine Young's modulus of elasticity and Ultimate Tensile Strength. Creep tests were performed at creep stress levels of 30 and 60 MPa. Creep periods of at least 25 h in duration were followed by recovery at zero stress. Duration of the recovery period was at least twice the time of the creep period. Oxidation …
Process Improvements For The Ah-64 Tail Rotor Vibration Analysis, Mark C. Newkirk
Process Improvements For The Ah-64 Tail Rotor Vibration Analysis, Mark C. Newkirk
Theses and Dissertations
The Apache was the first helicopter of its kind to fly with the tail rotor blade offset by 55 degrees as opposed to the traditional 90 degrees. Current balancing methods approximate the rotor system as a traditional 4 bladed, same plane system with different weight sensitivity coefficients for each set of blades. The Apache tail rotor computer model was built using the Rotorcraft Comprehensive Analysis System (RCAS) program. The objective was not to develop solutions for the sensitivity coefficients, but to identify predictive trends that result from the tail rotor blade location. Currently, sensitivity coefficients applied to the adjustment algorithms …
High Temperature Degradation Of 5250-4 Polymer Resin, Patrick E. Link
High Temperature Degradation Of 5250-4 Polymer Resin, Patrick E. Link
Theses and Dissertations
5250-4 bismaleimide resin is used in high performance polymer matrix composites with high temperature aeronautical applications. This thesis investigated the thermal and oxidative degradation of 5250-4 neat resin powder in argon, air, and oxygen environments. The powder was aged at 163 deg. C, 177 deg. C, and 190 deg. C in all environments for at least 250 hours. Isothermal thermo-gravimetric analysis demonstrated that weight loss was negligible for aging in the argon environment, indicating weight loss is the result of an oxidative process at these temperatures. The 5250-4 powder exhibited an initial period of weight gain before eventually losing weight …
Compressive Creep Behavior Of Nextel™ 720/Alumina Ceramic Matrix Composite At 1200°C In Air And In Steam Environment, Neil R. Szymczak
Compressive Creep Behavior Of Nextel™ 720/Alumina Ceramic Matrix Composite At 1200°C In Air And In Steam Environment, Neil R. Szymczak
Theses and Dissertations
The aerospace community continues to push the envelope in engineering aircraft that fly higher, faster, and safer while operating with a greater degree of efficiency. To meet these operational requirements innovative aerospace components must be designed to operate in aggressive environments. This research will investigate the ultimate compressive strength and the compressive creep behavior of NextelTM 720/Alumina ceramic matrix composite at 1200 °C in air and 100% steam environments. The effects of creep loading history on the tensile and compressive material behavior will also be examined. The primary strengths of the N720/A composite are its oxide/oxide composition which inherently …
Using Student Space Assets For Atmospheric Science Research, Robert J. Twiggs
Using Student Space Assets For Atmospheric Science Research, Robert J. Twiggs
Robert "Bob" Twiggs STEM Education Collection
A PowerPoint Presentation created by Professor Bob Twiggs titled "Using Student Space Assets For Atmospheric Science Research" from May 17, 2007.
The Emerging Small Satellite Industry And Opportunities For Education, Robert J. Twiggs
The Emerging Small Satellite Industry And Opportunities For Education, Robert J. Twiggs
Robert "Bob" Twiggs STEM Education Collection
A PowerPoint presentation created by Professor Bob Twiggs titled "The Emerging Small Satellite Industry and Opportunities for Education" from May 3, 2007.
Autonomous And Cooperative Multi-Uav Guidance In Adversarial Environment, Ugur Zengin
Autonomous And Cooperative Multi-Uav Guidance In Adversarial Environment, Ugur Zengin
Mechanical and Aerospace Engineering Dissertations - Archive
The research presented in this dissertation is aimed at developing rule-based autonomous and cooperative guidance strategies for UAVs to perform missions such as path planning, target tracking and rendezvous while reducing their risk/threat exposure level, and avoiding threats and/or obstacles by utilizing measurement information provided by sensors. First, a mathematical formulation is developed to represent the area of operation that contains various types of threats, obstacles, restricted areas, in a single framework. Once constructed, there will be no need to distinguish between adversaries as the framework already contains the information on what needs to be avoided and the level of …
Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation, Abhijit Hiraman Supekar
Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation, Abhijit Hiraman Supekar
Mechanical and Aerospace Engineering Theses - Archive
In this research, we propose mechanisms to continuously morph a wing from a lower aspect ratio to a higher and to further extremities of a gull and an inverted-gull configuration. The mechanism comprises of a linear actuator for the extension of the wing and the servo motors to obtain the gull and inverted gull configurations. The initial design and preliminary finite element representation using 3D-beams and plates in ANSYS Classic were the benchmarks to proceed for the detailed structural analysis of the complete wing in ANSYS Workbench. An elliptical pressure distribution at the quarter cord is assumed for the linear …
Design And Implementation Of A Feedback Linearizing Controller And Kalman Filter For A Magnetic Levitation System, John Andrew Henley
Design And Implementation Of A Feedback Linearizing Controller And Kalman Filter For A Magnetic Levitation System, John Andrew Henley
Mechanical and Aerospace Engineering Theses - Archive
The principal investigation undertaken in this research is the development and subsequent implementation of a feedback linearizing nonlinear controller and extended Kalman filter for a laboratory-based Magnetic Levitation (Maglev) device. The Maglev hardware is both highly nonlinear and open-loop unstable in its dynamic response. The control and estimation scheme proposed in this work is first validated using an increasingly sophisticated level of simulations. The control and estimation algorithm had the sensor noise identified using hardware data. Then, the plant noise covariance is tuned using both on-line and off-line hardware data. Additionally, the output of the nonlinear controller is then mapped …
A Generic Stability And Control Tool For Flight Vehicle Conceptual Design: Aeromech Software Development, Gary John Coleman
A Generic Stability And Control Tool For Flight Vehicle Conceptual Design: Aeromech Software Development, Gary John Coleman
Mechanical and Aerospace Engineering Theses - Archive
During the conceptual design (CD) phase, various solution concepts must, and should, be explored to select the best flight vehicle size and configuration in order to meet the mission requirements. As the aerospace industry advances novel aerospace flight vehicle configurations promising larger operational performance and overall efficiency, demanding integrated flight vehicles like the flying wing configuration (FWC) or blending wing body (BWB) are under investigation. Some of these novel configurations rely on novel control effectors (CE) and complex flight control systems in order to obtain the desired performance objectives. Clearly, stability and control plays an important roll in the design …
An Evaluation Of Using Component Mode Synthesis For Structural Models, Richard Lynn Scott
An Evaluation Of Using Component Mode Synthesis For Structural Models, Richard Lynn Scott
Mechanical and Aerospace Engineering Theses - Archive
Structural analysts have used component mode synthesis (CMS), also known as substructuring, for decades to divide large structural models into smaller, more manageable models, and to reduce the size of the associated mathematical problem. Applying CMS can also reduce the front-end effort to build models, even models that are smaller than those for which CMS has typically been applied. This paper presents an evaluation of the accuracy of two smaller substructured models so that analysts might feel confident in applying CMS to gain the benefits. The evaluation starts with an introduction to CMS. Then, CMS is applied to a small, …
Control And Simulation Of Relative Motion For Aerial Refueling In Racetrack Maneuver, Eunyoung Kim
Control And Simulation Of Relative Motion For Aerial Refueling In Racetrack Maneuver, Eunyoung Kim
Mechanical and Aerospace Engineering Theses - Archive
This thesis addresses the problem of controlling the receiver aircraft to achieve a successful aerial refueling. For the performance verification of the controller, a new set of nonlinear, 6-DOF, rigid body equations of motion for the receiver aircraft has been used. The equations are written in terms of state variables that are relative to the reference frame that is attached to, translates and rotates with the tanker aircraft. Furthermore, the nonlinear equations contain the wind effect terms and their time derivatives to represent the aerodynamic coupling involved between the two aircraft. These wind terms are obtained using an averaging technique …
Prediction Of Fatigue Life In 7075-T6 Aluminum From Neural Network Analysis Of Acoustic Emission Data, Nicholas S. Spivey
Prediction Of Fatigue Life In 7075-T6 Aluminum From Neural Network Analysis Of Acoustic Emission Data, Nicholas S. Spivey
Master's Theses - Daytona Beach
Through the use of an acoustic emission (AE) data acquisition system, a Kohonen self-organizing map, and a back-propagation neural network, AE data from 7075-T6 aluminum specimens were used to classify failure mechanisms and predict the number of fatigue cycles to failure. AE waveforms were captured from 40 notched tensile specimens during the low-cycle fatiguing process. A Kohonen self-organizing map and initial data filters were used to classify the data into two distinct failure mechanisms, plane strain and plane stress fracture, plus a third less prevalent mechanism. These results were employed to construct a back-propagation neural network to predict the number …
A Novel Cylindrical Punch Method To Characterize Interfacial Adhesion And Residual Stress Of A Thin Polymer Film, Bing Feng Ju, Kuo Kang Liu, Ming Fung Wong, Kai Tak Wan
A Novel Cylindrical Punch Method To Characterize Interfacial Adhesion And Residual Stress Of A Thin Polymer Film, Bing Feng Ju, Kuo Kang Liu, Ming Fung Wong, Kai Tak Wan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Adhesion of a pre-stressed silicone rubber film to a planar graphite surface was investigated by a new cylindrical punch method. a homemade apparatus was constructed to meet force and displacement resolutions of 0.1 μN and 10 nm. When the punch approached the intersurface force range across the punch-film gap, the film jumped into contact at "pull-in". Upon unloading, once the tensile load reached a threshold, a spontaneous delamination occurred at "pull-off" with a non-zero contact circle. a theoretical model was constructed based a simple energy balance. the new method can be used to characterize an adhesion interface between a pre-stressed …
Optimization Of Zero Net-Mass Flow Actuators For Aero-Optics Applications, Moira L. Denatale, Jonathan M. Mihaly
Optimization Of Zero Net-Mass Flow Actuators For Aero-Optics Applications, Moira L. Denatale, Jonathan M. Mihaly
Renée Crown University Honors Thesis Projects - All
Using experimental methods, zero net-mass flow actuators were optimized to manipulate flow around an airborne laser turret in order to reduce destructive aero-optics effects. Synthetic jets are created by 50 mm and 27 mm piezoelectric disk actuators. Our optimization process involved identifying an actuator’s cavity size, driving frequency, and amplitude to achieve the strongest, most consistent jet possible. The effects of driving a single actuator versus driving two actuators in or out of phase with one another were also investigated. An initial cavity depth was determined using the Helmholtz resonator cavity approximation which estimates the ideal cavity depth for a …
Optimization Of Zero Net-Mass Flow Actuators For Aero-Optics Applications, Moira L. Denatale, Jonathan M. Mihaly
Optimization Of Zero Net-Mass Flow Actuators For Aero-Optics Applications, Moira L. Denatale, Jonathan M. Mihaly
Renée Crown University Honors Thesis Projects - All
Using experimental methods, zero net-mass flow actuators were optimized to manipulate flow around an airborne laser turret in order to reduce destructive aero-optics effects. Synthetic jets are created by 50 mm and 27 mm piezoelectric disk actuators. Our optimization process involved identifying an actuator’s cavity size, driving frequency, and amplitude to achieve the strongest, most consistent jet possible. The effects of driving a single actuator versus driving two actuators in or out of phase with one another were also investigated. An initial cavity depth was determined using the Helmholtz resonator cavity approximation which estimates the ideal cavity depth for a …
Analysis Of Tapered Laminated Composite Tubes Under Tension And Torsion, Chethana Shankara Rao
Analysis Of Tapered Laminated Composite Tubes Under Tension And Torsion, Chethana Shankara Rao
Mechanical and Aerospace Engineering Theses - Archive
Closed form expressions for determining the displacement and twisting angle of tapered composite tubes are developed. The analytical expressions are developed based on the modified laminated plate theory which includes the tubular wall curvature of the laminate. It is found that the axial deformation and the twisting angle calculated by the current method agree well with the results obtained from the finite element method. The effect of stacking sequence, taper angle and fiber orientations on the axial deformation and twisting angle are studied by using the developed method. It is found that the taper angle plays a significant role on …
Management Of An Intelligent Argumentation Network For A Web-Based Collaborative Engineering Design Environment, Xiaoqing Frank Liu, Man Zheng, Ganesh K. Venayagamoorthy, Ming-Chuan Leu
Management Of An Intelligent Argumentation Network For A Web-Based Collaborative Engineering Design Environment, Xiaoqing Frank Liu, Man Zheng, Ganesh K. Venayagamoorthy, Ming-Chuan Leu
Computer Science Faculty Research & Creative Works
Conflict resolution is one of the most challenging tasks in collaborative engineering design. In our previous research, a web-based intelligent collaborative system was developed to address this challenge based on intelligent computational argumentation. However, two important issues were not resolved in that system: priority of participants and self-conflicting arguments. In this paper, we develop two methods for incorporating priorities of participants into the computational argumentation network: 1) weighted summation and 2) re-assessment of strengths of arguments based on priority of owners of the argument using fuzzy logic inference. In addition, we develop a method for detection of self-conflicting arguments. Incorporation …
Recent Developments In Smart Adaptive Structures For Solar Sailcraft, Mark Whorton, Young Kim, Jerry Oakley, Olawale Adetona, Lee Keel
Recent Developments In Smart Adaptive Structures For Solar Sailcraft, Mark Whorton, Young Kim, Jerry Oakley, Olawale Adetona, Lee Keel
Information Systems and Engineering Management Research Publications
The "Smart Adaptive Structures for Solar Sailcraft" development activity at MSFC has investigated issues associated with understanding how to model and scale the subsystem and multi-body system dynamics of a gossamer solar sailcraft with the objective of designing sailcraft attitude control systems. This research and development activity addressed three key tasks that leveraged existing facilities and core competencies of MSFC to investigate dynamics and control issues of solar sails. Key aspects of this effort included modeling and testing of a 30 m deployable boom; modeling of the multi-body system dynamics of a gossamer sailcraft; investigation of control-structures interaction for gossamer …
Launch And Field Operations Without Leaving Your Office And Cubesat Test Opportunities, Robert J. Twiggs
Launch And Field Operations Without Leaving Your Office And Cubesat Test Opportunities, Robert J. Twiggs
Robert "Bob" Twiggs STEM Education Collection
A PowerPoint presentation created by Professor Bob Twiggs titled "Launch and Field Operations without leaving your Office and CubeSat Test Opportunities" from April 19, 2007.
Coupled-Mode Theory For Stimulated Raman Scattering In High-Q/Vm Silicon Photonic Band Gap Defect Cavity Lasers, Xiaodong Yang, C. W. Wong
Coupled-Mode Theory For Stimulated Raman Scattering In High-Q/Vm Silicon Photonic Band Gap Defect Cavity Lasers, Xiaodong Yang, C. W. Wong
Mechanical and Aerospace Engineering Faculty Research & Creative Works
We examine the dynamics of stimulated Raman scattering in designed high-Q/Vm silicon photonic band gap nanocavities through the coupled-mode theory framework towards optically-pumped silicon lasing. The interplay of other X(3) effects such as two-photon absorption and optical Kerr, related free-carrier dynamics, thermal effects, as well as linear losses such as cavity radiation and linear material absorption are included and investigated numerically. Our results clarify the relative contributions and evolution of the mechanisms, and demonstrate the lasing and shutdown thresholds. Our studies illustrate the conditions for continuous-wave and pulsed highly-efficient Raman frequency conversion for practical realization in monolithic silicon …
The Onset For Compressibility Effects For Aerofoils In Ground Effect, G. Doig, T.J. Barber, E. Leonardi, A.J. Neely
The Onset For Compressibility Effects For Aerofoils In Ground Effect, G. Doig, T.J. Barber, E. Leonardi, A.J. Neely
Aerospace Engineering
The influence of flow compressibility on a highly-cambered inverted aerofoil in ground effect is presented, based on two-dimensional computational studies. This type of problem has relevance to open-wheel racing cars, where local regions of high-speed subsonic flow form under favourable pressure gradients, even though the maximum freestream Mach number is typically considerably less than Mach 0.3. An important consideration for CFD users in the field is addressed in this paper, the freestream Mach number at which flow compressibility significantly affects aerodynamic performance. More broadly, for aerodynamicists, the consequences of this are also considered. Comparisons between incompressible and compressible CFD siulations …
Fabrication And Compressive Behavior Of Corrugated Aramid-Epoxy Cellular Solids, Jeffrey Arthur Schneider
Fabrication And Compressive Behavior Of Corrugated Aramid-Epoxy Cellular Solids, Jeffrey Arthur Schneider
Master's Theses - Daytona Beach
Cellular solids are materials whose base material does not always occupy the entire solid fraction available. A number of cellular solids can provide blast protection and absorb impact energy, but few perform well resisting blunt object (ballistic) penetration. In this thesis, a method is proposed for fabricating cellular solids from aramid-epoxy composites that can absorb impact energy and resist blunt object penetration. The aramid-epoxy samples were fabricated using wet-layup techniques, with two different styles of Kevlar 49 woven fabric in a variety of orientations. Test sample density ranged from 0.08 0.23 g/cm3. Different lamination orientations, assembly techniques, and bonding adhesives …
Investigation Of Magnetic Field Profile Effects In Hall Thrusters, Oren Kornberg
Investigation Of Magnetic Field Profile Effects In Hall Thrusters, Oren Kornberg
Master's Theses - Daytona Beach
The purpose of this study was to show the relationship of different magnetic field profiles to the acceleration region length of a Hall thruster. The general transport equations were simplified and solved using a one-dimensional analysis. Some of the model assumptions include quasineutrality, Maxwellian electrons, and negligible thruster wall effects. The solved equation kept magnetic field as an input to the model for the analysis. The magnetic field was altered by changing the shape through the thruster, while keeping the maximum point fixed, and by shifting the profile, while keeping the shape fixed. Results indicate a strong correlation between the …
Impact-Induced Damage Characterization Of Composite Plates Using Neural Networks, Steve Eugene Watkins, Farhad Akhavan, Rohit Dua, K. Chandrashekhara, Donald C. Wunsch
Impact-Induced Damage Characterization Of Composite Plates Using Neural Networks, Steve Eugene Watkins, Farhad Akhavan, Rohit Dua, K. Chandrashekhara, Donald C. Wunsch
Electrical and Computer Engineering Faculty Research & Creative Works
Impact-induced damage in fiber-reinforced laminated composite plates is characterized. An instrumented impact tower was used to carry out low-velocity impacts on thirteen clamped glass/epoxy composite plates. A range of impact energies was experimentally investigated by progressively varying impactor masses (holding the impact height constant) and varying impact heights (holding the impactor mass constant). The in-plane strain profiles as measured by polyvinylidene fluoride (PVDF) piezoelectric sensors are shown to indicate damage initiation and to correlate to impact energy. Plate damage included matrix cracking, fiber breakage, and delamination. Electronic shearography validated the existence of the impact damage and demonstrated an actual damage …
Efficient Sampling For Non-Intrusive Polynomial Chaos Applications With Multiple Uncertain Input Variables, Serhat Hosder, Robert W. Walters, Michael Balch
Efficient Sampling For Non-Intrusive Polynomial Chaos Applications With Multiple Uncertain Input Variables, Serhat Hosder, Robert W. Walters, Michael Balch
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The accuracy and the computational efficiency of a Point-Collocation Non-Intrusive Polynomial Chaos (NIPC) method applied to stochastic problems with multiple uncertain input variables has been investigated. Two stochastic model problems with multiple uniform random variables were studied to determine the effect of different sampling methods (Random, Latin Hypercube, and Hammersley) for the selection of the collocation points. The effect of the number of collocation points on the accuracy of polynomial chaos expansions were also investigated. The results of the stochastic model problems show that all three sampling methods exhibit a similar performance in terms of the the accuracy and the …
Micro Synthetic Jets As Effective Actuator, Mehti Koklu
Micro Synthetic Jets As Effective Actuator, Mehti Koklu
Mechanical & Aerospace Engineering Theses & Dissertations
Synthetic jets have previously been studied as actuators for external macroflow control and recently been proposed for internal microflow applications. Despite the wide variety of the potential applications of synthetic jet actuators, the majority of the studies have been done at macro scales. Furthermore, there has not been any design methodology that addresses the effectiveness of the micro synthetic jet actuators. Bearing these needs in mind, a micro synthetic jet configuration is considered in a microscale environment where Kn number is less than 0.1 and more than 0.001. Flowfields are simulated by solving the compressible Navier-Stokes equations. The wall boundary …
Assessment Of Preliminary Design Approaches For Metallic Stiffened Cylindrical Shell Instability Problems, Vicki Owen Britt
Assessment Of Preliminary Design Approaches For Metallic Stiffened Cylindrical Shell Instability Problems, Vicki Owen Britt
Mechanical & Aerospace Engineering Theses & Dissertations
A preliminary design tool for metallic stiffened fuselage cylindrical panels subjected to longitudinal compression has been developed and validated by comparison to test results. Several methodologies for stiffened panel buckling and failure predictions were examined and evaluated. An appropriate level of analysis fidelity was determined for different failure modes and design details. Results from panel tests conducted to verify analytical methods used to design the Gulfstream V aircraft were presented. The panels were representative of four general skin/stringer configurations on the aircraft. Finite Element analyses and standard analytical methods were used to predict panel failure loads. The accuracy of the …