A model for magnetic flux leakage signal predictions

Abstract

An analytical model was developed to determine the length of a surface-breaking defect along the direction of the applied field when using the magnetic flux leakage (MFL) non-destructive technique. The theoretical model fits the experimental MFL results from simulated defects. The extreme positions of the normal magnetic leakage field component were subsequently used for a quantitative evaluation of the defect length. Permeability variations were neglected by employing a flux density close to sample saturation. Four different defect geometries were experimentally investigated and the validity of the analytical model was verified. Good agreement between theoretical and experimental results suggests that this method can be used as an inverse MFL data interpretation technique.

An Analytical Model for Prediction of Magnetic Flux Leakage from Surface Defects in Ferromagnetic Tubes

“…Percentage of the error for this single cylindrical hole is 0.62 %. The diameter estimated using analytical expression proposed by Mandache and Clapham [8] was 15.7 mm whose percentage error is 1.87 %. Proposed analytical expression has minimum error percentage.…”

“…Four different types of geometry were experimentally investigated and they validated the analytical model with the experimental results. Constant lift-off is considered and the lift-off studies have MEASUREMENT SCIENCE REVIEW Journal homepage: http://www.degruyter.com/view/j/msr ISSN 1335 -8871 not been performed [8]. Dutta et al proposed an analytical model by accounting the variation of surface magnetic charge density for defect surfaces oblique to the direction of applied field.…”

Iterative coarse to fine approach for interpretation of defect profiles using MFL measurements

“…For the following derivation, it is assumed that a Dipolar magnetic charge (DMC) is developed on the defect faces intersecting the exciting magnetic field as a result of its interaction with the excitation field as described in [3] and [5]. Moreover, local variations in magnetisation and permeability were avoided by assuming high magnetic excitation, corresponding to the saturation region of the material.…”

Theoretical Analysis of the Rectangular Defect Orientation using Magnetic Flux Leakage

“…The data obtained through the in-situ inspection of the specimen in literature are compared with the MFL profile generated by the calibrated samples. Recording the pattern of the leakage profile for the known defect in forward approach is not necessary when the dipole model is considered [2], [7]. Zatsepin et al (1966) introduced an analytical model using the point or strip of dipole for rectangular shape defect [8].…”