Journal of Nondestructive Evaluation

, Volume 8, Issue 4, pp 225–234 | Cite as

Some examples of nondestructive flaw detection by shearography

  • F. S. Chau
  • S. L. Toh
  • C. J. Tay
  • H. M. Shang
Article

Abstract

This paper presents some examples of nondestructive flaw detection using an optical method based on speckle shearing interferometry called shearography. In the method, a structure under study is illuminated by laser and imaged by a special image-shearing camera. After suitable processing, a fringe pattern which represents loci of surface displacement derivatives, i.e., strains, is observed in the image. Since defects in structures usually induce strain concentrations around them and since strain concentrations usually cause perturbations on the surface of structures, shearography reveals defects from anomalies in the recorded fringe pattern. In this work, the technique has been applied to the nondestructive detection of various flaws in plain and welded pipes, composite plates, and other engineering components. A simple model was also developed for the estimation of the depth of disbonds in glassfiber reinforced plastic sheets. Results obtained are good and demonstrate the usefulness of the method as a complement to other conventional NDT techniques.

Key words

Laser speckle interferometry shearography NDE metals composites 

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Copyright information

© Plenum Publishing Corporation 1989

Authors and Affiliations

  • F. S. Chau
    • 1
  • S. L. Toh
    • 1
  • C. J. Tay
    • 1
  • H. M. Shang
    • 1
  1. 1.Department of Mechanical and Production EngineeringNational University of SingaporeSingapore

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