Change trends of magnetic flux leakage with increasing magnetic excitation

Magnetic flux leakage (MFL) non-destructive testing technology is widely used. The MFL of a defect first increases with an increase in the magnetic excitation and is then thought to remain constant after magnetically saturating the ferromagnetic objects being tested. This trend is in agreement with the B-H curve. In this work, the change trends of the MFL are assessed by further deriving and analysing the MFL signal description, and a reduction of the MFL is found when the component is subject to strong magnetic fields. Later, using simulations from finite element models with various notch sizes and test conditions, the change trends of the MFL are further described and verified. Furthermore, the reduction of the MFL is also modified by reducing the primary origin of the magnetic compression effect. The work mentioned above elucidates scenarios involving increasing MFL and provides further knowledge about MFL mechanisms.