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Acoustical Imaging of near Surface Properties at the Rayleigh Critical Angle

  • G. L. Fitzpatrick
  • B. P. Hildebrand
  • A. J. Boland
Part of the Acoustical Imaging book series (ACIM, volume 12)

Abstract

Surface waves excited on a liquid-solid boundary by an incident longitudinal wave in water can be used to examine flaws and other defects near the surface of a solid. The method involves a focused acoustic source producing longitudinal waves at an average angle of incidence equal to the so-called “Rayleigh” critical angle. At this angle, an incident longitudinal wave in water excites a surface wave along a liquid-solid boundary. This surface wave penetrates roughly one shear wavelength into the solid and then reradiates back into the water along the direction of a would-be specular reflection angle θ. A point-like receiver at a reflection angle θ is used to record the amplitude R(θ) and the phase ?(θ) of this nonspecularly reflected signal. Because these signals are influenced by subsurface flaws, images of R(θ) and ?(θ) obtained by scanning the detector in a plane parallel to the sample (or scanning the sample) holding θ = θ(critical), yield images of these flaws. The quality of these images is good and provides an excellent method of near surface flaw detection. However, certain quantitative aspects of the critical angle phenomenon remain unresolved, making detailed image interpretation difficult. If these problems can be solved, a new and useful tool for nondestructive examaination will become available.

Keywords

Longitudinal Wave Surface Wave Nondestructive Test Critical Angle Phase Curve 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1982

Authors and Affiliations

  • G. L. Fitzpatrick
    • 1
  • B. P. Hildebrand
    • 1
  • A. J. Boland
    • 1
  1. 1.Spectron Development Laboratories, Inc.SeattleUSA

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