PURPOSE: To realize the highly accurate measurement of a crack, by setting separately a feed terminal and a measurement terminal at both sides of the surface orthogonal to the cracked surface.
CONSTITUTION: A DC power supply is connected to both ends 1P of the lower end surface of a CT test piece having a fatigued crack. Then the potential difference V is measured at both ends MP of a cut inlet. The potential difference ratio V/V0 is obtained on the basis of the potential difference V0 of a test piece having a prescribed length of the crack along with a prescribed width. Based on the ratio V/V0, the crack length a/W (a: length of crack; W: width of test piece) is measured. Thus the optimum position of a terminal is obtained since the difference of potential is measured between two areas which hold the crack between them. In such way, the length of the crack can be measured with high accuracy.
SAKATA SHINJI
SHIMIZU TASUKU
