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Full-Text Articles in Engineering
Aeroelastic Optimization Of Sounding Rocket Fins, Joseph R. Simmons Iii
Aeroelastic Optimization Of Sounding Rocket Fins, Joseph R. Simmons Iii
Theses and Dissertations
This research effort develops a multidisciplinary design tool to optimize sounding rocket fin geometries that minimize the mass of the fins while maintaining aerodynamic performance. This research grew out of a design problem experienced by the US Air Force Academy's Falcon LAUNCH program. The Falcon LAUNCH program is a senior design capstone project during which Air Force Academy cadets design, build and fly a sounding rocket over the course of an academic year. In the Spring of 2007, the Falcon LAUNCH V vehicle experienced a catastrophic failure when three of its four fins sheared off due to flutter. When the …
Least-Squares Finite Element Formulation For Fluid-Structure Interaction, Cody C. Rasmussen
Least-Squares Finite Element Formulation For Fluid-Structure Interaction, Cody C. Rasmussen
Theses and Dissertations
Fluid-structure interaction problems prove difficult due to the coupling between fluid and solid behavior. Typically, different theoretical formulations and numerical methods are used to solve fluid and structural problems separately. The least-squares finite element method is capable of accurately solving both fluid and structural problems. This capability allows for a simultaneously coupled fluid structure interaction formulation using a single variational approach to solve complex and nonlinear aeroelasticity problems. The least-squares finite element method was compared to commonly used methods for both structures and fluids individually. The fluid analysis was compared to finite differencing methods and the structural analysis type compared …
A Static Aeroelastic Analysis Of A Flexible Wing Mini Unmanned Aerial Vehicle, Nathan A. Pitcher
A Static Aeroelastic Analysis Of A Flexible Wing Mini Unmanned Aerial Vehicle, Nathan A. Pitcher
Theses and Dissertations
The static aeroelastic behavior of the Nighthawk mini unmanned aerial vehicle is examined using a combined experimental and computational approach. Three wings are examined. In order of increasing stiffness they are: a flexible wing, a stiff wing, and a fictitious rigid wing with zero deflection. Photogrammetry is used during wind tunnel testing to measure the average deflected shape of the flexible and stiff wings during flight. The independent variables during wind tunnel tests are angle of attack (ranging from −5.1° through 13.4°) and velocity, which is 20 mph, 30 mph, and 40 mph. Roll angle and yaw angle are control …
Critical Life Prediction Research On Boron-Enhanced Ti-6al-4v, Kevin A. Schwendiman
Critical Life Prediction Research On Boron-Enhanced Ti-6al-4v, Kevin A. Schwendiman
Theses and Dissertations
Research on boron-enhanced Ti-6-4 has demonstrated the following improvements to the Ti-6-4 alloy: up to 40% increase in ultimate tensile strength, up to 30% increase in modulus/stiffness, while maintaining greater than 10% ductility at RT conditions. The increased properties are attributed to small additions of boron (-or= wt%), which refine the microstructure and result in a small volume fraction (~6 vol%) of fine TiB whiskers. Previous research indicates potential for substantial improvements in fatigue, fatigue crack growth, and fracture toughness. However, uncertainty regarding these second-tier mechanical properties is currently limiting implementation of this class of titanium alloys. This study of …
Structural Stability Of A Joined-Wing Sensorcraft, Brandon J. Adams
Structural Stability Of A Joined-Wing Sensorcraft, Brandon J. Adams
Theses and Dissertations
This thesis employed a multi-disciplinary design approach to determine the structural stability of the Boeing Joined-Wing SensorCraft. Specifically, this thesis sought to characterize the free vibration modes, ensure a buckling safe design and determine the influence of the geometric and aeroelastic nonlinearities associated with this joined-wing design. The clamped free vibration modes were developed for a wind tunnel model and were compared to the free-free vibration modes, several differences were found. Linear static analyses were performed on numerous maneuver loads and gust conditions to determine the critical loading condition. The SensorCraft was then redesigned for the critical load case to …
Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland
Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland
Theses and Dissertations
Dynamic stability and stall during steady level turns were examined for VA-1, a joined-wing flight demonstrator aircraft. Configurations with a lower vertical tail and fairings over the main landing gear were compared with a recommendation on the combination had the best drag and dynamic stability characteristics. The dynamic stability analysis was broken into four key parts: a twist test experimentally measured mass moments of inertia, a panel method was used to find non-dimensional stability derivatives, lateral and longitudinal state space models estimated dynamic stability characteristics and handling quality levels were evaluated using a Cooper-Harper based rating system. VA-1 was found …
Structural Design Of Wing Twist For Pitch Control Of Joined Wing Sensor Craft, Fred A. Kimler Iii
Structural Design Of Wing Twist For Pitch Control Of Joined Wing Sensor Craft, Fred A. Kimler Iii
Theses and Dissertations
This research investigated two aspects of the aft wing structure of a joined wing SensorCraft. First, the efficacy of a novel approach for incorporating wing twist for pitch control was analyzed. This design involved adding a spanwise sliding joint into the wing structure at the lower aft spar of the vehicle's aft wing. Second, the joint section where the forward and aft wings connect and form the outboard wing was redesigned and analyzed to improve the load transmission between the wing spars. Using MSC.NASTRAN, linear and non-linear static analyses were performed to examine the efficiency of the wing twist sliding …
Dynamic Aeroelastic Analysis Of Wing/Store Configurations, Gregory H. Parker
Dynamic Aeroelastic Analysis Of Wing/Store Configurations, Gregory H. Parker
Theses and Dissertations
Limit-cycle oscillation, or LCO, is an aeroelastic phenomenon characterized by limited amplitude, self-sustaining oscillations produced by fluid-structure interactions. In order to study this phenomenon, code was developed to interface a modal structural model with a commercial computational fluid dynamics program. LCO was simulated for a rectangular wing, referred to as the Goland+ wing. It was determined that the aerodynamic nonlinearity responsible for LCO in the Goland+ wing was the combination of strong trailing-edge and lambda shocks which periodically appear and disappear. This mechanism limited the flow of energy into the structure which quenched the growth of the flutter, resulting …
Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman
Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman
Theses and Dissertations
There is a growing interest in understanding how uncertainties in flight conditions and structural parameters affect the character of a limit cycle oscillation (LCO) response, leading to failure of an aeroelastic system. Uncertainty quantification of a stochastic system (parametric uncertainty) with stochastic inputs (initial condition uncertainty) has traditionally been analyzed with Monte Carlo simulations (MCS). Probability density functions (PDF) of the LCO response are obtained from the MCS to estimate the probability of failure. A candidate approach to efficiently estimate the PDF of an LCO response is the stochastic projection method. The objective of this research is to extend the …
Aeroelastic Analysis Of A Joined-Wing Sensorcraft, Jennifer J. Sitz
Aeroelastic Analysis Of A Joined-Wing Sensorcraft, Jennifer J. Sitz
Theses and Dissertations
This study performed an aeroelastic analysis of a joined-wing SensorCraft. The analysis was completed using an aluminum structural model that was splined to an aerodynamic panel model. The force and pressure distributions were examined for the four aerodynamic panels: aft wing, fore wing, joint, and outboard tip. Both distributions provide the expected results (elliptical distribution), with the exception of the fore wing. The fore wing appears to be affected by interference with the joint. The use of control surfaces for lift and roll was analyzed. Control surfaces were effective throughout most of the flight profile, but may not be usable …
Nonlinear, Transonic Flutter Prediction For F-16 Stores Configuration Clearance, Raymond G. Toth
Nonlinear, Transonic Flutter Prediction For F-16 Stores Configuration Clearance, Raymond G. Toth
Theses and Dissertations
Wing flutter, or more accurately limit cycle oscillation (LCO), has been an issue for the F-16 since its operational deployment. Different store configurations and the permutations of those configurations after weapons are released will cause LCO to either disappear or appear. Unfortunately, the current method used by engineers for predicting LCO onset is based on linear, subsonic aerodynamic theory with no corrections for transonic effects. Predictions using this method are often good in frequency, but can be far off in predicting onset speed, forcing flutter engineers to rely more on experience and interpolation from similar configurations to design flight test …
Techniques For Reduced Order Modeling Of Aeroelastic Structures With Deforming Grids, John S. R. Anttonen
Techniques For Reduced Order Modeling Of Aeroelastic Structures With Deforming Grids, John S. R. Anttonen
Theses and Dissertations
Reduced order modeling (ROM) seeks to make the modeling of aeroelastic behavior practical by reducing computation time for design codes. Deforming grids are often used in aeroelastic problems to account for the deformation of the structure. Proper Orthogonal Decomposition (POD/ROM) is a ROM technique that operates in an index-space for computations, not accounting for changes in grid dynamics, and must be modified to reflect grid deformation properly. To investigate and account for the effects of grid deformation on POD/ROM, a new algorithm is developed that incorporates modifications to the usual formulation. Evaluation of the new algorithm is accomplished through application …