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Evaluation of Mechanical Modal Characteristics Using Optical TechniquesIn this paper the sensitivity of embedded fiber optic sensors to changes in modal characteristics of plates is discussed. In order to determine the feasibility of embedded fiber Bragg gratings for the detection of modal shapes and modal frequencies, a comparison of holographically imaged modes and the detected dynamic strain from embedded fiber optic Bragg gratings is made. Time averaged optical holography is used for the detection of mechanical defects, or damage, in various aerospace components. The damage is detected by measuring an alteration in structural dynamics, which is visually apparent when using time-averaged holography. These shifts in the mode shapes, both in frequency of the resonance and spatial location of vibration nodes, are caused by changes in parameters that affect the structure's mechanical impedance, such as stiffness, mass and damping, resulting from cracks or holes. It is anticipated that embedded fiber optic sensor arrays may also be able to detect component damage by sensing these changes in modal characteristics. This work is designed to give an initial indication to the feasibility of damage detection through the monitoring of modal frequencies and mode shapes with fiber optic sensors.
Document ID
Document Type
Technical Memorandum (TM)
Lekki, John
(NASA Glenn Research Center Cleveland, OH United States)
Adamovsky, Grigory
(NASA Glenn Research Center Cleveland, OH United States)
Flanagan, Patrick
(Cleveland State Univ. Cleveland, OH United States)
Weiland, Ken
(NASA Glenn Research Center Cleveland, OH United States)
Date Acquired
September 7, 2013
Publication Date
June 1, 2002
Subject Category
Report/Patent Number
NAS 1.15:211678
Meeting Information
Ninth Annual International Symposium on Smart Structures and Materials(San Diego, CA)
Funding Number(s)
PROJECT: RTOP 708-87-13
Distribution Limits
Work of the US Gov. Public Use Permitted.
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