Experimental Study of Three-Dimensional Identification of Semi-Elliptical Crack on the Back Surface by Means of Direct-Current Electrical Potential Difference Method of Multiple-Point Measurement Type

A method for identification of a semi-elliptical crack on the back surface of metal plate by means of direct-current electrical potential difference method (DC-PDM) of multiple-point measurement type was proposed by the authors previously. Geometry of the crack was given by the two-dimensional location of the crack center, the surface and inward angles of the crack, and the length and depth of the crack. In this paper, experiments on the crack identification were carried out using six metal plates with different geometries of semi-elliptical cracks made on the back surface by electric discharge machining. Geometrical parameters of the crack were evaluated by the proposed method. The result of identification was successful and it was clarified that the semi-elliptical crack on the back surface can be identified nondestructively by dc-PDM of multiple-point measurement type.