NOVEL-APPROACH FOR DETECTING DISTRIBUTED SURFACE-BREAKING CRACKS

A novel approach to the problem of detecting finely distributed surfac e cracks in a structure is proposed. The approach relies on the detect ion of anisotropy introduced into the surface by an oriented array of cracks and can be used for crack detection even when individual cracks in the array are below the practical threshold of detectability by co nventional inspection techniques. The feasibility of detecting anisotr opy associated with distributed cracking was established experimentall y using: (i) a directional eddy-current probe to detect anisotropy in the effective electrical conductivity and (ii) a line-focused laser-ul trasonic source to detect anisotropy in the attenuation of ultrasonic Rayleigh waves.