LAUSR

The detection of magnetic flux leakage (MFL) enables nondestructive detection and characterization of defects in magnetic structures. In this letter, Fourier transforms of the leakage fields from a two-dimensional surface defect are evaluated to produce analytical expressions for the frequency response of MFL signals detected by a flux-sensitive sensor. The expressions show the correlation between the spectral response of the leakage fields, defect dimensions, and sensing element lift-off spacing as a product of frequency-dependent defect-width loss function, spacing loss function, and thickness enhancement function. The lower and upper band edges of the band-limited leakage magnetic fields are theoretically identified. A spectral method for sizing of defects is proposed based on the frequency response.