Magnetic flux leakage by adjacent parallel surface slots

This paper clarifies the relation between the magnetic flux leakage signals caused by two adjacent parallel slots on a metal surface and the distance between the two. The depth of smaller slot can be evaluated by considering an effect that the amplitude of leakage flux decreases as the depth ratio of two slots and the slot-to-slot distance increase. A new method is proposed as an alternative to analysing the waveform: it is based on the analysis of locus of the vector consisting of tangential and normal components of the magnetic flux leakage signals.