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  • 1
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    Noise Reduction in an Aircraft Fuselage Model Using Active Trim Panels (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: An experiment was conducted to evaluate the use of force actuators on a model aircraft interior trim panel as the control element for active control of interior noise. The trim panel, designed specifically for this study, was constructed in three large identical sections and hard mounted to the ring frames of the primary structure. Piezoceramic actuators were bonded to the outer surface of the trim panels. Studies of the interior pressure response due to both the primary source alone and control sources alone were conducted as well as the control cases. A single acoustic loudspeaker, centered at the axial midpoint, generated the acoustic field to be controlled.
    Keywords: Acoustics
    Type: Proceedings of the 4th Annual Workshop: Advances in Smart Materials for Aerospace Applications; 215-218; NASA-CP-10185
    Format: text
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  • 2
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    Laboratory study of sidewall noise transmission and treatment for a light aircraft fuselage (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Aircraft (ISSN 0021-8669); 24; 660-665
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  • 3
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    Preliminary Work for Modeling the Propellers of an Aircraft as a Noise Source in an Acoustic Boundary Element Analysis (1998)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: An algorithm for generating appropriate velocity boundary conditions for an acoustic boundary element analysis from the kinematics of an operating propeller is presented. It constitutes the initial phase of Integrating sophisticated rotorcraft models into a conventional boundary element analysis. Currently, the pressure field is computed by a linear approximation. An initial validation of the developed process was performed by comparing numerical results to test data for the external acoustic pressure on the surface of a tilt-rotor aircraft for one flight condition.
    Keywords: Acoustics
    Type: Noise Control Engineering; Volume 46; No. 3; 132-136
    Format: text
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  • 4
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    XV-15 Structural-Acoustic Data (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tiltrotor aircraft are a potentially viable means of intercity travel. The tiltrotor is able to transport passengers relatively quickly from the center of a city to destinations within a 300-mile radius. For such vehicles to be commercially viable, the interior noise and vibration levels must be acceptable to the passengers. A review of the literature revealed very little structural-acoustic data related to the tiltrotor. For this reason, structural-acoustic measurements were taken aboard an XV-15 tiltrotor. The six flight conditions included five in level flight, nominally 140-220 knots, for airplane mode (nacelle at 0 degrees) and one out-of-ground-effect (OGE) hover (nacelle at 90 degrees). The flight test measurements included nine exterior surface pressures, five structural accelerations, and two interior pressures. These sensors were located near the tip path plane on the port side of the aircraft. One minute of data was acquired at each condition. The data is presented as time histories, autospectra, coherence functions, and cross-spectra. In general, for level flight, the measured data showed very little effect of forward flight speed except to change the amplitude of the response; however, the character of the response was found to be dependent on spatial location. In contrast, in the hover mode the spatial location had very little effect on the character of the response. Additionally, the report highlights: the coherence between the transducer data and the rotor tach signal; and transfer function calculations between the exterior pressures.
    Keywords: Acoustics
    Type: NASA-TM-112855 , NAS 1.15:112855 , ARL-TR-1423
    Format: application/pdf
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  • 5
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    Predicted and measured strain responses of isotropic panels to base excitation (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The accuracy of classical linear theory for predicting acceleration and strain for cantilevered and Clamped-Free-Clamped-Free (C-F-C-F) panels excited through the base is studied. Aluminum, steel and titanium plates of various dimensions and thicknessess were vibration tested, using a broadband random signal applied through a shaker mounting fixture. The strains were measured at 9 locations on the cantilevered panels and at 5 locations on the C-F-C-F panels. Predictions were based on the Ritz method. The measured accelerations of the base were input to the analysis for the forcing function. Comparisons between predicted and measured strain acceleration spectra were within an average error of 20 percent for both the cantilevered and C-F-C-F panels.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-4054 , L-16446 , NAS 1.15:4054 , AVSCOM-TM-88-B-013 , AD-A197950
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  • 6
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    A Comparison of Measured and Predicted XV-15 Tiltrotor Surface Acoustic Pressures (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Predicted XV-15 exterior surface acoustic pressures are compared with previously published experimental data. Surface acoustic pressure transducers were concentrated near the tip-path-plane of the rotor in airplane mode. The comparison emphasized cruise conditions which are of interest for tiltrotor interior noise - level flight for speeds ranging from 72 m/s to 113 m/s. The predictions were produced by components of the NASA Langley Tiltrotor Aeroacoustic Code (TRAC) system of computer codes. Comparisons between measurements and predictions were made in both the time and frequency domains, as well as overall sound pressure levels. In general, the predictions replicated the measured data well. Discrepancies between measurements and predictions were noted. Some of the discrepancies were due to poor correlation of the measured data with the rotor tach signal. In other cases limitations of the predictive methodology have been indicated.
    Keywords: Acoustics
    Type: AHS Technical Specialists'' Meeting for Rotorcraft Acoustics and Aerodynamics; Oct 28, 1997 - Oct 30, 1997; Williamsburg, VA; United States
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  • 7
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    A Gas-Actuated Projectile Launcher for High-Energy Impact Testing of Structures (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A gas-act,uated penetration device has been developed for high-energy impact testing of structures. The high-energy impact. t,estiiig is for experimental simulation of uncontained engine failures. The non-linear transient finite element, code LS-DYNA3D has been used in the numerical simula.tions of a titanium rectangular blade with a.n aluminum target, plate. Threshold velocities for different combinations of pitch and yaw angles of the impactor were obtained for the impactor-target, t8est configuration in the numerica.1 simulations. Complet,e penet,ration of the target plate was also simulat,ed numerically. Finally, limited comparison of analytical and experimental results is presented for complete penetration of the target by the impactor.
    Keywords: Aircraft Design, Testing and Performance
    Type: AIAA Paper 99-1385 , AIAA/ASME/ASCE/AHS/ASC 40th Structures, Structural Dynamics, and Materials Conference; Apr 12, 2004 - Apr 15, 2004; Saint Louis, MO; United States
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  • 8
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    Application of Probabilistic Analysis to Aircraft Impact Dynamics (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Full-scale aircraft crash simulations performed with nonlinear, transient dynamic, finite element codes can incorporate structural complexities such as: geometrically accurate models; human occupant models; and advanced material models to include nonlinear stressstrain behaviors, laminated composites, and material failure. Validation of these crash simulations is difficult due to a lack of sufficient information to adequately determine the uncertainty in the experimental data and the appropriateness of modeling assumptions. This paper evaluates probabilistic approaches to quantify the uncertainty in the simulated responses. Several criteria are used to determine that a response surface method is the most appropriate probabilistic approach. The work is extended to compare optimization results with and without probabilistic constraints.
    Keywords: Air Transportation and Safety
    Type: AIAA Paper 2003-1482 , 44th AIAA/ASME/ASCE/AHS/ASC Structure, Structural Dynamics Conference; Apr 07, 2003 - Apr 10, 2003; Norfold, VA; United States
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  • 9
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    Data Reduction and Its Impact on Test-Analysis Correlation (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A research project has been initiated to improve crash test and analysis correlation. The research has focused on two specimen types: simple metallic beams and plates; and a representative composite fuselage section. Impact tests were performed under carefully controlled conditions. In addition, the specimens were densely instrumented to enable not only correlation with finite element simulations, but to also assess the repeatability of the data. Simulations utilizing a detailed finite element model were executed in a nonlinear transient dynamic code. The results presented in this paper concentrate on the effect of several data reduction processes, to include filtering frequency and sampling rate, on the correlation accuracy.
    Keywords: Air Transportation and Safety
    Type: Third Triennial International Fire and Cabin Safety Research Conference; Oct 22, 2001 - Oct 25, 2001; Atlantic City, NJ; United States
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  • 10
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    Simulation of Aircraft Landing Gears with a Nonlinear Dynamic Finite Element Code (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Recent advances in computational speed have made aircraft and spacecraft crash simulations using an explicit, nonlinear, transient-dynamic, finite element analysis code more feasible. This paper describes the development of a simple landing gear model, which accurately simulates the energy absorbed by the gear without adding substantial complexity to the model. For a crash model, the landing gear response is approximated with a spring where the force applied to the fuselage is computed in a user-written subroutine. Helicopter crash simulations using this approach are compared with previously acquired experimental data from a full-scale crash test of a composite helicopter.
    Keywords: Aircraft Design, Testing and Performance
    Type: AIAA Paper 2000-4090 , Modeling and Simulation Technologies; Aug 14, 2000 - Aug 17, 2000; Denver, CO; United States
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