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Test-Anchored Vibration Response Predictions for an Acoustically Energized Curved Orthogrid Panel with Mounted Componentsrich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for component-loaded curved orthogrid panels typical of launch vehicle skin structures. The test data were used to anchor computational predictions of a variety of spatially distributed responses including acceleration, strain and component interface force. Transfer functions relating the responses to the input pressure field were generated from finite element based modal solutions and test-derived damping estimates. A diffuse acoustic field model was applied to correlate the measured input sound pressures across the energized panel. This application quantifies the ability to quickly and accurately predict a variety of responses to acoustically energized skin panels with mounted components. Favorable comparisons between the measured and predicted responses were established. The validated models were used to examine vibration response sensitivities to relevant modeling parameters such as pressure patch density, mesh density, weight of the mounted component and model form. Convergence metrics include spectral densities and cumulative root-mean squared (RMS) functions for acceleration, velocity, displacement, strain and interface force. Minimum frequencies for response convergence were established as well as recommendations for modeling techniques, particularly in the early stages of a component design when accurate structural vibration requirements are needed relatively quickly. The results were compared with long-established guidelines for modeling accuracy of component-loaded panels. A theoretical basis for the Response/Pressure Transfer Function (RPTF) approach provides insight into trends observed in the response predictions and confirmed in the test data. The software developed for the RPTF method allows easy replacement of the diffuse acoustic field with other pressure fields such as a turbulent boundary layer (TBL) model suitable for vehicle ascent. Structural responses using a TBL model were demonstrated, and wind tunnel tests have been proposed to anchor the predictions and provide new insight into modeling approaches for this environment. Finally, design load factors were developed from the measured and predicted responses and compared with those derived from traditional techniques such as historical Mass Acceleration Curves and Barrett scaling methods for acreage and component-loaded panels.
Document ID
20120002977
Acquisition Source
Marshall Space Flight Center
Document Type
Presentation
Authors
Frady, Gregory P. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Duvall, Lowery D. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Fulcher, Clay W. G. (Jacobs Technologies Engineering Science Contract Group Huntsville, AL, United States)
Laverde, Bruce T. (Jacobs Technologies Engineering Science Contract Group Huntsville, AL, United States)
Hunt, Ronald A. (Jacobs Technologies Engineering Science Contract Group Huntsville, AL, United States)
Date Acquired
August 25, 2013
Publication Date
December 7, 2011
Subject Category
Acoustics
Report/Patent Number
M11-0647
M11-1362
Meeting Information
Meeting: JANNAF 5th Spacecraft Propulsion Subcommittee Meeting
Location: Huntsville, AL
Country: United States
Start Date: December 5, 2011
End Date: December 9, 2011
Sponsors: Department of the Air Force, NASA Headquarters, Department of the Navy, Department of the Army
Distribution Limits
Public
Copyright
Public Use Permitted.

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