Research on magnetic leakage detection of defect edge angles based on the asymmetric magnetic dipole model

Abstract Fast and accurate magnetic flux leakage (MFL) detection methods are essential for reconstructing and evaluating surface and near-surface defects in ferromagnetic materials. The existing magnetic dipole model (MDM) can simulate MFL signals of regular or limited types of irregular defects. Still, it cannot simulate trapezoidal defects with different edge angles (i.e. the angle between the defect boundary and the horizontal direction) of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> </mml:math> . Therefore, this paper proposes an improved MDM method, namely the asymmetric MDM (AMDM), to study the relationship between different edge angles <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> </mml:math> and MFL signals. The results demonstrate that the improved AMDM not only reveals the relationship between the edge angle of the defect and the characteristics of the magnetic leakage signal, but also verifies the model’s applicability to asymmetric defects through numerical simulation and experimental testing. Compared with the traditional MDM, this method breaks through the limitations of the symmetry model and can effectively verify the changes in magnetic leakage signals at different edge angles, providing an efficient and accurate analytical tool for magnetic leakage detection of complex defects (e.g. non-right-angle edge defects).