NDT of rods and pipes using shear wave caustics

An important feature of shear wave insonification of circularly cylindrical samples is the caustic formations which occur inside the samples, after internal reflections at the external sample boundaries. Strong echoes are obtained from defects in the outer regions of the samples when they pass through these caustic regions because of the concentration of energy along the caustic. The caustic effectively acts as an acoustic microscope system which probes the surfaces of the defects as they intersect it. The returned pulse-echo data can be utilized to determine the size, shape, and position of the defects. This is illustrated with samples containing artificial and real defects.