Further insight into the potential role of shear wave caustics in NDE of rods and pipes

After reflection from the inner wall a diverging beam of shear waves inside a rod or pipe converges to form a caustic. This surface of high sound intensity forms a well defined structure within the sample under test which can be used as a probe for internal defects. The width of the energy concentration at the caustic has been measured and used to calculate the resolution of such a testing system. The use of shear wave caustics to determine the size of internal cracks, in a manner independent of flaw geometry, is demonstrated.