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Large Modal Survey Testing Using the Ibrahim Time Domain Identification TechniqueThe ability of the ITD identification algorithm in identifying a complete set of structural modal parameters using a large number of free-response time histories simultaneously in one analysis, assuming a math model with a high number of degrees-of-freedom, has been studied. Identification results using simulated free responses of a uniform rectangular plate, with 225 measurement stations, and experimental responses from a ground vibration test of the Long Duration Exposure Facility (LDEF) Space Shuttle payload, with 142 measurement stations, are presented. As many as 300 degrees-of-freedom were allowed in analyzing these data. In general, the use of a significantly oversized math model in the identification process was found to maintain or increase identification accuracy and to identify modes of low response level that are not identified with smaller math model sizes. The concept of a Mode Shape Correlation Constant is introduced for use when more than one identification analysis of the same structure are conducted. This constant quantifies the degree of correlation between any two sets of complex mode shapes identified using different excitation conditions, different user-selectable algorithm constants, or overlapping sets of measurements.
Document ID
19860004121
Acquisition Source
Legacy CDMS
Document Type
Other
Authors
Ibrahim, S. R.
(Old Dominion Univ. United States)
Pappa, R. S.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 12, 2013
Publication Date
November 1, 1985
Publication Information
Publication: Old Dominion Univ. Dyn. Identification for Control of Large Space Struct.
Subject Category
Structural Mechanics
Report/Patent Number
AIAA PAPER 81-0528R
Meeting Information
Meeting: AIAA/ASME/ASCE/AHS Struct., Struct. Dyn. and Mater. Conf.,
Location: Atlanta, GA
Country: United States
Start Date: August 6, 1981
Accession Number
86N13589
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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