Detection of Surface-Breaking Cracks in the Acoustic Microscope
The prime advantage of the scanning acoustic microscope lies in its ability to image the interaction of elastic waves with the specimen. Over the past two years a body of information has been accumulated which shows that the scanning acoustic microscope (SAM) is a powerful instrument for detection of cracks and elastic discontinuities. This ability is due to the dominant role played by leaky surface waves in the contrast of the SAM. When a Rayleigh wave propagates along the surface of the specimen it may be strongly scattered by defects much less than a wavelength thick. Fine cracks and grain boundaries which would not be resolvable by conventional criteria can thus be seen in acoustic micrographs.
KeywordsSurface Wave Rayleigh Wave Incident Plane Wave Acoustic Image Reflectance Function
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