ISSN:
1573-4862
Schlagwort(e):
Rayleigh critical angles
;
interface waves
;
local isonification
;
subsurface information
;
anisotropy
;
nonlinearities
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Elektrotechnik, Elektronik, Nachrichtentechnik
,
Mathematik
Notizen:
Abstract Acoustic critical angle measurements usually involve broad beam or global isonification of a water-solid interface. In order to obtain local interface data, it is convenient to use a focused acoustic source with lens axis at incident angle θ and point-receiver at specular reflection angle θ. By scanning this combination at various critical angles (θ=θcrit), interface waves are generated locally near the lens focus. These waves penetrate the solid to a depth of approximately one shear wavelength λ T and are modulated by discontinuities such as flaws, inclusions, and debonds that may be present there. A radiated longitudinal wave in water accompanies these modulated interface waves and carries information on subsurface flaws to the point-detector along the direction of a specularly reflected wave. By scanning the focus-receiver combination along the interface, the receiver output may be used to form images of local subsurface detail. We show that in anisotropic materials, such as crystals, there are generally two different θcrit where a radiating interface wave provides subsurface information. We also discuss special problems associated with the use of a focused acoustic source including nonlinear effects (generation of harmonics) in the water.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00565865
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