23 October 2001 Strain measurement in curved industrial components using multicomponent shearography
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Shearography is a full-field optical technique usually used for the determination of surface strain. Interferometric speckle patterns recorded before and after object deformation are correlated to obtain the displacement gradient. Further calculation yields the surface strain. Ful surface strain measurement of displacement derivative from a minimum of three illumination, or viewing, directions. Shearography can also be used to measure surface slope and shape by recording interferometric speckle patterns before and after displacement of the optical source. For a curved object the object shape introduces errors into the displacement gradient measurement, resulting from the variation in the sensitivity vector across the object surface, and from the dependence of the applied shear upon the surface slope. In this paper the surface slope of a gas main pipe, of diameter 90 mm, is measured using a source displacement technique in shearography. The surface slope is then integrated in the shear direction to yield the surface shape. The displacement gradient is measured using three illumination directions and a single viewing direction. The displacement gradient measurements are corrected for errors due to the object shape and mapped onto the surface of the object.
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Roger M. Groves, Roger M. Groves, Stephen W. James, Stephen W. James, Ralph P. Tatam, Ralph P. Tatam, } "Strain measurement in curved industrial components using multicomponent shearography", Proc. SPIE 4398, Optical Measurement Systems for Industrial Inspection II: Application in Industrial Design, (23 October 2001); doi: 10.1117/12.445554; https://doi.org/10.1117/12.445554

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