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Proceedings Paper

Investigations on a novel technique for experimental structural dynamics: theoretical analysis of impact testing using CSLDV
Author(s): R. Ribichini; D. Di Maio; A. B. Stanbridge; D. J. Ewins
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Paper Abstract

In the past decade, Continuous Scanning Laser Doppler Velocimetry (CSLDV) has been successfully used in experimental modal analysis and vibration tests. Essentially, this technique consists in the use of a Laser Scanning Velocimeter (LDV) moving continuously across a vibrating surface rather than stepping in a point-by- point fashion. If the structure is undergoing harmonic vibration, its Operating Deflection Shape (ODS) can be recovered in a very short time and without the limitations in spatial resolution typical of discrete point measurements. Recently, this technique has been extended to transient excitation -i.e. the object is swept by the laser transducer during a period of transient free response caused by an impact. The combination of a broadband excitation with a full-field measurement results in a highly complex signal, modulated both by the mode shapes of the structure and by the exponential decays due to damping effects. Thus, the signal contains in its spectrum a mixture of temporal information (the eigenvalues of the structure) and spatial information (the eigenvectors), all in a single time history. This paper presents a mathematical model of this new concept, first applied to a simple one-dimensional scan and then to a rectangular 2-D area scan. The numerically-simulated signals of the 1-D case are compared with actual measurements, both in time and frequency domains. Finally, an analysis of the measurement parameters involved in this method is provided.

Paper Details

Date Published: 17 June 2008
PDF: 9 pages
Proc. SPIE 7098, Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 709807 (17 June 2008); doi: 10.1117/12.802918
Show Author Affiliations
R. Ribichini, Imperial College London (United Kingdom)
D. Di Maio, Univ. of Bristol (United Kingdom)
A. B. Stanbridge, Imperial College London (United Kingdom)
D. J. Ewins, Imperial College London (United Kingdom)

Published in SPIE Proceedings Vol. 7098:
Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications
Enrico Primo Tomasini, Editor(s)

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