Three-Dimensional Vibration Analysis Using Electronic Speckle Pattern Interferometry (ESPI)

ESPI is an established analysis technique, offering the benefits of non-contact, full-field resolution and real-time observation. It has previously been used in many applications for analysis of out-of-plane vibrations and in-plane strains. In this paper it is shown that a combination of out-of-plane and in-plane sensitive ESPI arrangements can be used to measure the vibration amplitude of an object in three independent orthogonal components. These results can then easily be interpreted to determine the full three-dimensional mode shape. The method is demonstrated by observing volume vibrations of a thick hollow cylinder. Experimental results are compared with finite element predictions, enabling the mode shapes to be easily identified and analysed.