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Finite Element Method Characterization of 3D Magnetic Flux Leakage Signal of Crack Discontinuities at Multiple Liftoff Values

Previous studies commonly did analysis of magnetic flux leakage (MFL) signals at only one linescan liftoff and could not give comprehensive information about the MFL field. This paper uses the finite element method to analyze MFL information of surface cracks on pipelines at multiple liftoff values. The valley-valley spacing value of axial components and peak-valley spacing value of radial components are analyzed at multiple liftoff values. Studies show that signals at multiple liftoff values indicate more information than signals at one liftoff. A technique using a double liftoff compensation algorithm is proposed to measure width more precisely.

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