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Understanding Acoustic Emission Testing- Reading 1 Part B-A

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Surface (Rayleigh) waves are not as common as the longitudinal and shear<br />

waves, but are used to great advantage in a limited number of applications<br />

that require an ability of the wave to follow the contours of irregularly shaped<br />

surfaces such as jet engine blades and vanes.<br />

Rayleigh waves extend from the surface to a depth of about one wavelength<br />

into the material and thus are only sensitive to surface or very near-surface<br />

flaws.<br />

They are very sensitive to surface conditions including the presence of<br />

residual coupling compounds as well as finger damping.<br />

Rayleigh waves are usually generated by mode conversion using angle beam<br />

search units designed to produce shear waves just beyond the second critical<br />

angle.<br />

Charlie Chong/ Fion Zhang

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