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Proceedings Paper

Using spatial DFT-IDFT techniques for mapping of nonsquare and unevenly 2-D velocity data acquired by scanning laser Doppler vibrometer
Author(s): William Xinzuo Li; Larry D. Mitchell; Min Fu Lu; Michael L. Neumann
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Paper Abstract

The state-of-the-art Scanning Laser Doppler Vibrometry (SLDV) technique provides an efficient data acquisition method for modal testing, especially on a large structure with high spatial data density. Two-dimensional angularly evenly spaced (in the laser beam scanning sense) data point distribution are generated. This causes an unevenly spaced data point distribution on the surface of the test structure in the most cases. The interval variations between data points can be quite large if the surface of the structure is not flat, such as an aircraft fuselage. The grid of data points will also become non-square. However, in many cases evenly spaced data point distribution with square or rectangular grids is highly desirable. One such case is when the structure is too large for one scan. A few separate scans are required to be patched together to describe the entire structure. The second example is when a structure needs to be scanned from different viewing angles and data points from different scans need to be coincident to extract 3-D velocity data of the surface of the structure. The third example is where the data points are used to obtain the wavenumber of the vibrating surface of the structure. In this paper, the original velocity data of a partial surface area of an aircraft fuselage were acquired to busing the SLDV technique with a high spatial density. The 2-D angular evenly spaced data then were mapped to a truly spatial evenly spaced coordinates by using the spatial DFT-IDFT technique. This DFT-IDFT technique can preserve original measured velocity information (even including the noise) during the mapping process. This 2-D data mapping technique certainly is not only limited to the fuselage, but also can be very useful for any 3-D structures, large or small, that require more than one scan to compleate surface velocity data acquisition.

Paper Details

Date Published: 8 September 1994
PDF: 7 pages
Proc. SPIE 2358, First International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (8 September 1994); doi: 10.1117/12.185302
Show Author Affiliations
William Xinzuo Li, Virginia Polytechnic Institute and State Univ. (United States)
Larry D. Mitchell, Virginia Polytechnic Institute and State Univ. (United States)
Min Fu Lu, Virginia Polytechnic Institute and State Univ. (United States)
Michael L. Neumann, Newport News Shipbuilding (United States)

Published in SPIE Proceedings Vol. 2358:
First International Conference on Vibration Measurements by Laser Techniques: Advances and Applications
Enrico Primo Tomasini, Editor(s)

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