Understanding Acoustic Emission Testing- Reading 1 Part B-A

The major axis of the ellipse is perpendicular to the surface of the solid. As
the depth of an individual atom from the surface increases the width of its
elliptical motion decreases. Surface waves are generated when a
longitudinal wave intersects a surface near the second critical angle and
they travel at a velocity between .87 and .95 of a shear wave. Rayleigh
waves are useful because they are very sensitive to surface defects (and
other surface features) and they follow the surface around curves.
Because of this, Rayleigh waves can be used to inspect areas that other
waves might have difficulty reaching.
Wave velocity:
• Longitudinal wave velocity =1v,
• The velocity of shear waves through a material is approximately half that
of the longitudinal waves, (≈0.5v)
• Surface waves are generated when a longitudinal wave intersects a
surface near the second critical angle and they travel at a velocity
between .87 and .95 of a shear wave. ≈(0.87~0.95)x0.5v
Charlie Chong/ Fion Zhang