抄録
This paper studies the position, diameter and depth determination for internal defects by a. c. potential method. Alternative currents from 500Hz to 6000Hz were applied to specimens that have artificial holes with 1.0mm-2.5mm diameter and 0.8mm-5.0mm depth. A. c. potentials from 500Hz to 6000Hz were measured at 13 positions on the specimen surface. The potential difference between 500Hz and 6000Hz depended on the diameter and hole depth. A new a. c. method was proposed for determining the position, diameter and depth of internal holes. The hole position was determined as the symmetric point of the disturbed potential profile by a defect. The diameter and depth of the internal hole were determined by utilizing potential difference and critical frequency. Finite element method analyses were carried out for confirming the reliability of experimental results. The potential differences and critical frequencies obtained in FEM analyses agreed with the experiment results quantitatively.
