3D FEM analysis in magnetic flux leakage method

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3D FEM analysis in magnetic flux leakage method

Huang, Z. / Que, P. / Chen, L.

Magnetic flux leakage technique is generally considered to be the most cost-effective method for corrosion monitoring. In this technique, the wall of the pipeline is magnetized axially to near saturation flux density. If, at some point, the wall thickness is reduced by a defect, a higher fraction of the magnetic flux will 'leak' from the wall into the air inside and outside the pipe. The magnetic leakage field measured on the nearby of the pipe contains information about the pipe conditions. The MFL inspection tool, propelled by the oil pressure or driven equipment, magnetizes the pipe wall; MFL signals due to any irregularities are detected and stored within the tool. The inspection vehicle consists of a magnetizer which is made of permanent magnet or coil and circumferentially distributed sensor assembly which is hall sensor or signal pick up coil and. Analytical approaches to the modeling of MFL have largely been difficult due to both the awkward boundaries associated with realistic defect shapes and the lack of generality that ensures when making the necessary assumptions needed to obtain tractable analytical solutions and. Viable models are needed in order to understand the ways in which fields and defects interact to produce measurable indications, to help in the design of detection probes for diverse applications, to simulate those testing environments which are difficult and/or expensive to replicate in the laboratory, and perhaps most important in many of the critical testing situations facing industries today, to provide training data for automated defect characterization schemes.