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Measurement of slopes of structural deflections by speckle-shearing interferometry

A new technique has been developed that allows slopes of structural deflections to be determined. The technique utilizes speckle effect of coherent light and is an interferometric method. However, the technique overcomes several of the limitations associated with conventional and holographic interferometry

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Abstract

A specimen illuminated by coherent light is imaged by a camera through a shearing mechanism so that the speckle from one point on the surface can be made to interfere with the speckle from a neighboring point. The resultant speckle pattern is recorded. By mechanically interfering the recorded speckle pattern corresponding to deformed and undeformed states of the specimen, respectively, using double-exposure technique, a speckle-moiré-fringe pattern is generated. These fringes which depict derivatives of deflections of the specimen are made visible by spatial-filtering technique. Speckle-moiré fringes can also be obtained in real time. This method is a new interferometry and will be referred to as “speckle-shearing interferometry”.

Speckle-shearing interferometry has the same function as Ligtenberg's technique. However, it does not have the sometimes inconvenient requirement of Ligtenberg's technique that the surface of the specimen must be of mirror quality. The new technique will be particularly useful in studies of flexural deformation such as flexed beams and plates.

Although speckle-shearing interferometry is an interferometric method, it overcomes several of the limitations associated with holographic and speckle interferometries, namely: (1) the setup is simple and does not need laborious alignments of optical components, (2) it does not require stringent mechanical and ambient stabilities, (3) coherent requirement of light is greatly relaxed, and (4) the sensitivity is reduced that somehow fills the gap in sensitivity between moiré techniques and holographic or speckle interferometry.

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References

  1. Theocaris, P. S., Moiré Fringes in Strain Analysis, Pergamon Press, New York (1969).

    Google Scholar 

  2. Hovanesian, J. D. andHung, Y. Y., “Moiré Contour-sum, Contour-difference, and Vibration Analysis of Arbitrary Objects,”Applied Optics,10 (12),2734–2738 (Dec. 1971).

    Google Scholar 

  3. Hovanesian, J. D. and Varner, J., “Methods for Determining the Bending Moments in Normally Loaded Thin Plates by Hologram Interferometry,” Strathclyde Symposium on the Engineering Use of Holography, Cambridge University Press (1968).

  4. Boone, P. M. andVerbiest, R., “Application of Hologram Interferometry to Plate Deformation and Translation Measurement,”Optica Acta,16,555–567 (Oct. 1969).

    Google Scholar 

  5. Aprahamian, R., Evensen, D. A., Mixson, J. S. andWright, J. E., “Application of Pulsed Holographic Interferometry to the Measurement of Propagating Transverse Waves in Beams,”Experimental Mechanics,11(7),309–314 (1971).

    Google Scholar 

  6. Aprahamian, R., Evensen, D. A., Mixson, J. S. andJacoby, J. L., “Holographic Study of Propagating Transverse Waves in Plates,”Experimental Mechanics,11 (8),357–362 (1971).

    Google Scholar 

  7. Tsuruta, T., Shiotake, N. andItoh, Y., “Formation and Localization of Holographically Produced Interference Fringes,”Optica Acta,16(6),723–733 (1969).

    Google Scholar 

  8. Stetson, K. A., “A Rigorous Treatment of the Fringes of Hologram Interferometry,”Optik,29,386–400 (1969).

    Google Scholar 

  9. Leendertz, J. A., “Interferometric Displacement Measurement on Scattering Surface Utilizing Speckle Effect,” J. Phys. E. Sc. Instr.,3 (1970).

  10. Hung, Y. Y. andHovanesian, J. D., “Full-field Surface-strain and Displacement Analysis of Three-dimensional Objects by Speckle Interferometry,”Experimental Mechanics,12(10),454–460 (1972).

    Google Scholar 

  11. Ligtenberg, F. K., “The Moiré Method: A New Experimental Method for the Determination of Moments is Small Slab Models,”Proc. SESA XII(2),83–98 (1954).

    Google Scholar 

  12. Reider, G. andRitter, R., “Drummungsmessung an belasteten platten nach dem Ligtenbergschen Moiré-Verfahren,”Forschung im Ingenieurwesen VDI-Verlag, Dusseldorf,31(2),33–44 (1965).

    Google Scholar 

  13. Theocaris, P. S., Moiré Fringes in Strain Analysis, Pergamon Press, New York, 249–250 (1969).

    Google Scholar 

  14. Chiang, F. P. andTreiber, J., “A Note on Ligtenberg's Reflective Moiré Method,”Experimental Mechanics,10(12),537–538 (1970).

    Google Scholar 

  15. Sokolnikoff, L. S., Mathematical Theory of Elasticity, McGraw-Hill Book Co., New York (1956).

    Google Scholar 

  16. Archbold, E., Burch, J. M. andEnnos, A. E., “Recording of In-plane Surface Displacement by Double-exposure Speckle Photography,”Optica Acta,17(12),883–898 (1970).

    Google Scholar 

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Authors and Affiliations

  1. IIT Research Institute, 60616, Chicago, IL

    Y. Y. Hung (Associate Research Engineer)

  2. Department of Theoretical and Applied Mechanics, University of Illinois, 61801, Urbana, IL

    C. E. Taylor (Professor)

Authors
  1. Y. Y. Hung
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  2. C. E. Taylor
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Hung, Y.Y., Taylor, C.E. Measurement of slopes of structural deflections by speckle-shearing interferometry. Experimental Mechanics 14, 281–285 (1974). https://doi.org/10.1007/BF02322832

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  • DOI: https://doi.org/10.1007/BF02322832

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