Np. Benklevskaya et Ai. Pashagin, MAGNETIC MONITORING OF HOT-ROLLED TUBES BY MEANS OF HARMONICS IN THE EMF IN AN INDUCTION PROBE, Russian journal of nondestructive testing, 30(6), 1994, pp. 448-450
The higher-harmonic method has been used to examine the signals from v
arious types of defect in hot-rolled tubes having various orientations
within the tube wall. It is possible to monitor components with much
larger gaps between the sensor and the surface than when the fundament
al is used.