Some examples of nondestructive flaw detection by shearography
- 70 Downloads
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 wordsLaser speckle interferometry shearography NDE metals composites
Unable to display preview. Download preview PDF.
- 1.R. K. Erf, ed.,Holographic Nondestructive Testing (Academic Press, New York, 1974).Google Scholar
- 2.D. W. Robinson, Holography edges close to the shopfloor,Chart. Mech. Engineer 36–40 (October 1986).Google Scholar
- 3.C. M. Vest,Holographic Interferometry (John Wiley, New York, 1979).Google Scholar
- 4.R. K. Erf, ed.,Speckle Metrology (Academic Press, New York, 1978).Google Scholar
- 5.Y. Y. Hung, Shearography, a new optical method for strain measurement and nondestructive testing,Opt. Engineer. 21(3):391–395 (1982).Google Scholar
- 6.I. A. Wojtaszak, The calculation of maximum deflection, moment and shear for uniformly loaded rectangular plate with clamped edges,J. Appl. Mech. 4(4):A173-A176 (1937).Google Scholar
- 7.H. M. Shang, S. L. Toh, F. S. Chau, and C. J. Tay, Nondestructive Testing of Offshore Structures Using Laser Techniques, Proceedings of Offshore Technology Malaysia, Kuala Lumpur, Malaysia, February 1985.Google Scholar