METHOD OF DETECTING FLAWS IN MOVING ELONGATED OBJECTS Russian patent published in 1994 - IPC

FIELD: flaw detection. SUBSTANCE: method of determining flaws in an elongated object including measuring cross-section area of elongated object is based on magnetizing the object and producing a relative change in magnetic field indicative of change in cross-section area and involves the steps of: magnetizing by an alternating current, shaping a periodic electric signal, comparing it with a reference one generated proportionally to the magnetizing current. The signal produced on the object is compared by superimposing the out-of-phase magnetizing AC on the signal produced on the object. The field is monitored by a phase shift and change in higher harmonics of the signal produced on the object. EFFECT: accuracy maintained at enhanced movement velocity of objects, widened range of elongated objects to be inspected with regard to cross-sections not depending on the presence of coatings. 1 dwg