A Theoretical Approach for the Discrimination of Crack Tip and Small Defect Echoes

Abstract

Due to diffraction of US by crack tips, a misinterpretation of C-Scans can be made by mistaking detection of a large misoriented crack for a small flaw. As the latter is often tolerable, the former jeopardizes the life of the piece. Fig. 1. shows C-Scans at various amplification levels. The two spots due to diffraction by the near and far tips of a crack can be interpreted as arising from two small defects, even at high amplification level (+18 dB) for which S/N ratio becomes unacceptable