DETECTION OF THE INITIATION OF CRACK BY A. C. POTENTIAL METHOD

The principle and characteristics of the A. C. potential method for crack de-tection has been described. Various types of steel specimens including ferritic, fer-rite-pearlitic, martensitic or austenitic etc. have been examined by this method. At-tempts have been made to clarify the different patterns of potential curves associ-ated with the different steels, the relation between the peak values of potentialcurves and the initiation of cracking, and the relation between the increment ofpotential and the crack growth. Factors causing changes on the potential curvesare tentatively discussed.