INVARIANCE-TRANSFORMATIONS FOR MAGNETIC-FLUX LEAKAGE SIGNALS

Magnetic flux leakage (MFL) methods are used extensively for inspectin g ferromagnetic materials. The analysis of the MFL signal is however f raught with problems associated with the sensitivity of the signal to a number of factors such as the MFL sensor velocity and variations in the permeability of the test specimen. The interpretation can be simpl ified if the signals can be processed to attain invariance to these co nditions. This paper presents novel methods for obtaining permeability invariant and velocity invariant MFL signals.