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  • 1
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    Multidisciplinary Design, Analysis, and Optimization Tools Developed at NASA Armstrong Flight Research Center (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Aircraft Design, Testing and Performance; Numerical Analysis
    Type: DFRC-E-DAA-TN37553 , Multidisciplinary Design, Analysis, and Optimization Tools Developed at NASA Armstrong Flight Research Center; Dec 09, 2016; Edwards, CA; United States
    Format: application/pdf
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  • 2
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    New Flutter Analysis Technique for CFD-based Unsteady Aeroelasticity (2009)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: This paper presents a flutter analysis technique for the transonic flight regime. The technique uses an iterative approach to determine the critical dynamic pressure for a given mach number. Unlike other CFD-based flutter analysis methods, each iteration solves for the critical dynamic pressure and uses this value in subsequent iterations until the value converges. This process reduces the iterations required to determine the critical dynamic pressure. To improve the accuracy of the analysis, the technique employs a known structural model, leaving only the aerodynamic model as the unknown. The aerodynamic model is estimated using unsteady aeroelastic CFD analysis combined with a parameter estimation routine. The technique executes as follows. The known structural model is represented as a finite element model. Modal analysis determines the frequencies and mode shapes for the structural model. At a given mach number and dynamic pressure, the unsteady CFD analysis is performed. The output time history of the surface pressure is converted to a nodal aerodynamic force vector. The forces are then normalized by the given dynamic pressure. A multi-input multi-output parameter estimation software, ERA, estimates the aerodynamic model through the use of time histories of nodal aerodynamic forces and structural deformations. The critical dynamic pressure is then calculated using the known structural model and the estimated aerodynamic model. This output is used as the dynamic pressure in subsequent iterations until the critical dynamic pressure is determined. This technique is demonstrated on the Aerostructures Test Wing-2 model at NASA's Dryden Flight Research Center.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: DFRC-934 , International Forum on Aeroelasticity and Structural Dynamics (IFASD) 2009; Jun 21, 2009 - Jun 25, 2009; Seattle, WA; United States
    Format: text
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  • 3
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    Shape Sensing for Wings with Spars and Ribs Using Simulated Strain (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: This presentation will discuss application of a two step approach to wings with ribs and spars using public domain techniques.
    Keywords: Aircraft Design, Testing and Performance; Structural Mechanics
    Type: AFRC-E-DAA-TN63298 , AIAA SciTech Forum 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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  • 4
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    Shape Sensing for Wings with Spars and Ribs Using Simulated Strain (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Active trim shape control can be used to minimize error between target and actual aircraft trim shape during flight. Trim shape sensing for aircraft during flight is not only important for highly flexible aircraft, such as the National Aeronautics and Space Administration (NASA) Helios Prototype remotely piloted flying wing aircraft, but also for a delta-wing type aircraft, such as a supersonic commercial transport aircraft. A two-step theory utilizing distributed strain for a real-time shape sensing of a full three-dimensional structure has been introduced previously. This study focuses on the application of the two-step theory to finite element models of a wing with spars and ribs such as the X-59 QueSST aircraft (Lockheed Martin Corporation, Bethesda, Maryland), a tapered wing, a dihedral/anhedral wing, and a stiffened dihedral/anhedral wing. A finely meshed finite element structural model is desired to capture accurate curvature distributions along the neutral axes of the wing cross sections during pre-test analysis for shape sensing of a wing with ribs and spars. The two-step theory used in this study gives excellent deformation correlation with the MSC/NASTRAN (MSC Software, Newport Beach, California) results along the neutral axis for all test cases used in this study except the X-59 QueSST aircraft.
    Keywords: Aerodynamics; Structural Mechanics
    Type: AFRC-E-DAA-TN61538 , AIAA SciTech Forum 2019; Jan 07, 2018 - Jan 10, 2018; San Diego, CA; United States
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  • 5
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    Wing Shape Sensing from Measured Strain (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new two step theory is investigated for predicting the deflection and slope of an entire structure using strain measurements at discrete locations. In the first step, a measured strain is fitted using a piecewise least squares curve fitting method together with the cubic spline technique. These fitted strains are integrated twice to obtain deflection data along the fibers. In the second step, computed deflection along the fibers are combined with a finite element model of the structure in order to extrapolate the deflection and slope of the entire structure through the use of System Equivalent Reduction and Expansion Process. The theory is first validated on a computational model, a cantilevered rectangular wing. It is then applied to test data from a cantilevered swept wing model.
    Keywords: Aircraft Stability and Control; Aircraft Design, Testing and Performance
    Type: DFRC-E-DAA-TN19606 , SciTech 2015; Jan 05, 2015 - Jan 09, 2015; Kissimmee, FL; United States
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  • 6
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    Wing Shape Sensing from Measured Strain (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new two-step theory is investigated for predicting the deflection and slope of an entire structure using strain measurements at discrete locations. In the first step, a measured strain is fitted using a piecewise least-squares curve fitting method together with the cubic spline technique. These fitted strains are integrated twice to obtain deflection data along the fibers. In the second step, computed deflection along the fibers are combined with a finite element model of the structure in order to interpolate and extrapolate the deflection and slope of the entire structure through the use of the System Equivalent Reduction and Expansion Process. The theory is first validated on a computational model, a cantilevered rectangular plate wing. The theory is then applied to test data from a cantilevered swept-plate wing model. Computed results are compared with finite element results, results using another strainbased method, and photogrammetry data. For the computational model under an aeroelastic load, maximum deflection errors in the fore and aft, lateral, and vertical directions are -3.2%, 0.28%, and 0.09%, respectively; and maximum slope errors in roll and pitch directions are 0.28% and -3.2%, respectively. For the experimental model, deflection results at the tip are shown to be accurate to within 3.8% of the photogrammetry data and are accurate to within 2.2% in most cases. In general, excellent matching between target and computed values are accomplished in this study. Future refinement of this theory will allow it to monitor the deflection and health of an entire aircraft in real time, allowing for aerodynamic load computation, active flexible motion control, and active induced drag reduction.
    Keywords: Aeronautics (General); Aircraft Stability and Control; Aircraft Design, Testing and Performance
    Type: DFRC-E-DAA-TN16065 , AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; Jan 05, 2015 - Jan 09, 2015; Kissimmee, FL; United States
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  • 7
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    Follow on Research for Multi-Utility Technology Test Bed Aircraft at NASA Dryden Flight Research Center (FY13 Progress Report) (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Modern aircraft employ a significant fraction of their weight in composite materials to reduce weight and improve performance. Aircraft aeroservoelastic models are typically characterized by significant levels of model parameter uncertainty due to the composite manufacturing process. Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of Multi Utility Technology Test-bed (MUTT) aircraft is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of MUTT aircraft. The ground vibration test-validated structural dynamic finite element model of the MUTT aircraft is created in this study. The structural dynamic finite element model of MUTT aircraft is improved using the in-house Multi-disciplinary Design, Analysis, and Optimization tool. In this study, two different weight configurations of MUTT aircraft have been improved simultaneously in a single model tuning procedure.
    Keywords: Aeronautics (General); Structural Mechanics
    Type: DFRC-E-DAA-TN11588 , 2013 Aerospace Flutter and Dynamic Council Meeting; Oct 31, 2013; Palmdale CA; United States
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  • 8
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    Aeroelastic Optimization Study Based on X-56A Model (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A design process which incorporates the object-oriented multidisciplinary design, analysis, and optimization (MDAO) tool and the aeroelastic effects of high fidelity finite element models to characterize the design space was successfully developed and established. Two multidisciplinary design optimization studies using an object-oriented MDAO tool developed at NASA Armstrong Flight Research Center were presented. The first study demonstrates the use of aeroelastic tailoring concepts to minimize the structural weight while meeting the design requirements including strength, buckling, and flutter. A hybrid and discretization optimization approach was implemented to improve accuracy and computational efficiency of a global optimization algorithm. The second study presents a flutter mass balancing optimization study. The results provide guidance to modify the fabricated flexible wing design and move the design flutter speeds back into the flight envelope so that the original objective of X-56A flight test can be accomplished.
    Keywords: Aircraft Design, Testing and Performance
    Type: DFRC-E-DAA-TN15587 , AIAA Atmospheric Flight Mechanics Conference; Jun 16, 2014 - Jun 20, 2014; Altanta GA; United States
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  • 9
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    Creating a Test Validated Structural Dynamic Finite Element Model of the Multi-Utility Technology Test Bed Aircraft (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of Multi Utility Technology Test Bed, X-56A, aircraft is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of X-56A. The ground vibration test validated structural dynamic finite element model of the X-56A is created in this study. The structural dynamic finite element model of the X-56A is improved using a model tuning tool. In this study, two different weight configurations of the X-56A have been improved in a single optimization run.
    Keywords: Structural Mechanics
    Type: DFRC-E-DAA-TN14986 , AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference; Jun 16, 2014 - Jun 20, 2014; Atlanta, GA; United States
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  • 10
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    Creating a Test Validated Structural Dynamic Finite Element Model of the X-56A Aircraft (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the Multi Utility Technology Test-bed, X-56A aircraft, is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground vibration test-validated structural dynamic finite element model of the X-56A aircraft is created in this study. The structural dynamic finite element model of the X-56A aircraft is improved using a model tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, while other properties such as center of gravity location, total weight, and offdiagonal terms of the mass orthogonality matrix were used as constraints. The end result was a more improved and desirable structural dynamic finite element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.
    Keywords: Structural Mechanics
    Type: DFRC-E-DAA-TN13855 , AIAA Aviation 2014; Jun 16, 2014 - Jun 20, 2014; Atlanta, GA; United States|AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference; Jun 16, 2014 - Jun 20, 2014; Atlanta, GA; United States
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