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Membrane Vibration Analysis Above the Nyquist Limit with Fluorescence VideogrammetryA new method for generating photogrammetric targets by projecting an array of laser beams onto a membrane doped with fluorescent laser dye has recently been developed. In this paper we review this new fluorescence based technique, then proceed to show how it can be used for dynamic measurements, and how a short pulsed (10 ns) laser allows the measurement of vibration modes at frequencies several times the sampling frequency. In addition, we present experimental results showing the determination of fundamental and harmonic vibration modes of a drum style dye-doped polymer membrane tautly mounted on a 12-inch circular hoop and excited with 30 Hz and 62 Hz sinusoidal acoustic waves. The projected laser dot pattern was generated by passing the beam from a pulsed Nd:YAG laser though a diffractive optical element, and the resulting fluorescence was imaged with three digital video cameras, all of which were synchronized with a pulse and delay generator. Although the video cameras are capable of 240 Hz frame rates, the laser s output was limited to 30 Hz and below. Consequently, aliasing techniques were used to allow the measurement of vibration modes up to 186 Hz with a Nyquist limit of less than 15 Hz.
Document ID
20040082250
Acquisition Source
Langley Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Dorrington, Adrian A. (NASA Langley Research Center Hampton, VA, United States)
Jones, Thomas W. (NASA Langley Research Center Hampton, VA, United States)
Danehy, Paul M. (NASA Langley Research Center Hampton, VA, United States)
Pappa, Richard S. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2004
Subject Category
Instrumentation And Photography
Meeting Information
Meeting: SEM X International Congress and Exposition on Experimental and Applied Mechanics
Location: Costa Mesa, CA
Country: United States
Start Date: June 7, 2004
End Date: June 10, 2004
Sponsors: Society for Experimental Mechanics
Funding Number(s)
OTHER: 23-090-20-15
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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