Range of Applicability of a Technique for Constructing Magnetic Induction Lines for Flaw Sizing in Extended Objects

A technique for approximate solution of the inverse geometric problem of magnetostatics for a plate made of a high-permeability ferromagnet in a magnetic field is presented. The technique is presented both for the case of magnetic transducers located directly above a surface defect of loss of metal continuity and for the case where magnetic transducers are located above the defect-free surface of the plate. It is assumed that the plate is accessible from one side only. The sizes of defects in which the proposed technique works reliably are determined. It is shown that the proposed technique can be used in mobile devices to carry out flaw detection of drill pipes using the MFL (magnetic flux leakage) method directly at drilling sites.