Three-dimensional identification of semi-elliptical crack on the back surface by means of direct-current electrical potential difference method with multiple-probe sensor

A method of three-dimensional identification of a semielliptical crack existing on the back surface of a conductive plate by direct-current electrical potential difference method with a multiple-probe sensor was proposed. The geometrical condition of the crack was specified by six parameters, the surface and inward angles of the crack plane, θ_sur and θ_in, the length and depth of the crack, c and a, and the two-dimensional location of the crack center, (y_c, z_c), on the back surface, respectively. Identification was carried out based on the distribution of electrical potential difference on the surface of the plate measured with a sensor composed of grid-arranged multiple probes called the "multiple-probe sensor." As an approximate cracked body and a quick analysis method were used, a number of repeated electrical potential field analyses necessary for the identification of the crack became possible within a practical time. The validity of the method was numerically confirmed by carrying out the identification based on the result by the finite element analysis.