This article highlights warning signs that a composite panel may be delaminating or thinning, but engineers have a powerful nondestructive testing tool in shearography. This is a laser interferometric method developed originally for full-field observation of surface strains of components. Flaws usually induce strain concentrations around them, and shearography can be employed to detect those flaws. A relatively new variation, digital speckle-shearing interferometry (DSSI), uses a charged-coupled device (CCD) camera and computer image processing to capture and process the interferometric fringe patterns. The digital version is faster than conventional shearography, and does not require any film or Fourier filtering. The main advantages of digital speckle shearing interferometer are the ease and speed with which fringe patterns can be obtained.
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February 1999
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Using Shearography to Find the Flaws
Digital Speckle Shearing Interferometry Uses a CCD Camera and Computer Image Processing to Produce the Fringe Patterns that Spell Trouble in Composite Panel and Pipes.
Siew-Lok Toh and Fook-Siong Chau are associate professors in the Department of Mechanical and Production Engineering at the National University of Singapore.
Mechanical Engineering. Feb 1999, 121(02): 62-63 (2 pages)
Published Online: February 1, 1999
Citation
Toh, S., and Chau, F. (February 1, 1999). "Using Shearography to Find the Flaws." ASME. Mechanical Engineering. February 1999; 121(02): 62–63. https://doi.org/10.1115/1.1999-FEB-7
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