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Proceedings Paper

Whole-field modal analysis using electronic speckle pattern interferometry
Author(s): George Graham; Jon N. Petzing; Margaret Lucas; John Raymond Tyrer
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Paper Abstract

Pointwise modal analysis techniques suffer from the compromises required to infer wholefield vibration behavior from a predetermined number of measurement data points. The measurement grid is normally chosen before the most sensitive area of the test piece have been identified and this can lead to a requirement for further grid refinement, with the consequent spatial and temporal disadvantages. This paper presents a technique for obtaining wholefield modal data using electronic speckle pattern interferometry (ESPI), and focuses on the manipulation of optical information to provide a grid of data points which is transferred to a modal analysis software package for comparison with traditional pointwise modal data sets. The advantages of obtaining the initial wholefield vibration picture in real time and subsequently overlaying a chosen measurement data grid, are demonstrated. Modal analysis of a steel plate is presented. By taking advantage of wholefield data, grabbed at the same instant in time and then transferred into modal analysis software, ESPI mode shape information is directly compared with measurements using other pointwise techniques and finite element analysis (FEA), through a modal assurance criterion calculation. Results showing successful mode identification by ESPI are illustrated, by comparison of results for the fourth resonant mode of the plate with those from laser Doppler vibrometry, accelerometer measurements and FEA.

Paper Details

Date Published: 23 August 1996
PDF: 10 pages
Proc. SPIE 2868, Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (23 August 1996); doi: 10.1117/12.248659
Show Author Affiliations
George Graham, Loughborough Univ. (United Kingdom)
Jon N. Petzing, Loughborough Univ. (United Kingdom)
Margaret Lucas, Univ. of Glasgow (United Kingdom)
John Raymond Tyrer, Loughborough Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 2868:
Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications
Enrico Primo Tomasini, Editor(s)

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