A simple crack depth estimation method from backscattering response

A depth estimation method for a crack on metal surfaces has been studied and a simple estimation formula and measurement method have been proposed. This formula is based on our previous theoretical analysis that the backscattering from a crack causes periodical s (dips) as the frequency changes, and the first dip occurs when the depth of the crack becomes nearly one-half the incident wavelength. Dependencies of the crack´s aperture and the incident angle have also been studied and considered as our depth estimation parameters. Test measurement has been made to check the validity of our estimation procedure.