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Proceedings Paper

Monitoring shape change in compliant structures
Author(s): Euan J. Rigg; Robert R. J. Maier; James S. Barton; Andrew John Moore; Julian D. C. Jones; Scott McCulloch; Andrew Wallwork; Gary Burnell
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Paper Abstract

We describe an optical system to monitor small long-term changes in the shape of a surface by using a network of optical fibre Bragg grating strain gauges, for applications in which space does not permit the use of techniques such as photogrammetry or structured light methods. Gratings are bonded to copper beryllium strips held under tension in contact with the test surface. The copper beryllium strips enable sufficient force to be transferred to the optical fibre from the compliant surface. Shape changes are revealed as strain changes in the sensor strips, inferred from wavelength shifts in the Bragg peaks. The optical signals are obtained in reflection by illuminating the sensor fibres with a broadband source and using a scanning Fabry-Perot filter to generate the spectrum with a wavelength resolution of 0.3 pm over the range 1530 to 1570 nm. Laboratory tests show that a strain resolution of 8 microstrain can be achieved with temperature compensation over the range 20 to 50 C, with a multiplexing capability of between 11 and 16 temperature - strain sensor pairs, depending on temperature gradients on the test surface. We present experimental measurements on a cylindrical test object subject to diametral loading, and show a comparison with a finite element model.

Paper Details

Date Published: 22 July 2003
PDF: 12 pages
Proc. SPIE 5050, Smart Structures and Materials 2003: Smart Sensor Technology and Measurement Systems, (22 July 2003); doi: 10.1117/12.484229
Show Author Affiliations
Euan J. Rigg, Heriot-Watt Univ. (United Kingdom)
Robert R. J. Maier, Heriot-Watt Univ. (United Kingdom)
James S. Barton, Heriot-Watt Univ. (United Kingdom)
Andrew John Moore, Heriot-Watt Univ. (United Kingdom)
Julian D. C. Jones, Heriot-Watt Univ. (United Kingdom)
Scott McCulloch, AWE (United Kingdom)
Andrew Wallwork, AWE (United Kingdom)
Gary Burnell, AWE (United Kingdom)

Published in SPIE Proceedings Vol. 5050:
Smart Structures and Materials 2003: Smart Sensor Technology and Measurement Systems
Daniele Inaudi; Eric Udd, Editor(s)

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