Crack depth estimation by back scattering response

Crack detection is one of the important tasks for industrial materials and products from the standpoint of safety. The assessment of the crack geometry would be a crucial parameter for quality control of products. Electromagnetic plane wave scattering by a narrow trough, which could serve as a canonical structure for a crack model, has been analyzed rigorously. Based on our theoretical and numerical analysis (Sato et al. (1994), Sekiguchi et al. (2002)), a simple estimation formula for the crack depth has been derived using dip frequency on the monostatic radar cross section (RCS). In order to check the validity of our crack depth estimation formula, some measurement results are obtained and shown in this paper. The estimation error is found to be less than 3 percent.