A method of eddy current flaw test that detects disturbed magnetic flux was proposed, to improve the crack direction dependency of the detectability of bobbin-coil-type probes. These are conventionally used for eddy-current nondestructive examination of steam generator tubes in pressurized- water-type nuclear plants. The principle of this method is based on the fact that the symmetrical spatial distribution of the magnetic field induced by the exciting coils is disturbed by a flaw and that the pick-up coils effectively detect only the magnetic flux component disturbed by a flaw. The feasibility of this method was examined by using a sample probe in the test conditions in which the direction and location of an artificial flaw were varied.
