A multidirectional magnetic flux leakage detection based crack 3-D profile reconstruction method

Abstract

Magnetic flux leakage detection is a widely used method for non-destructive testing of ferromagnetic materials. In the research field, the profile reconstruction of defects is the focus. Due to the small width and complex morphology of cracks, it is easy to have signals missing and distortion based on unidirectional magnetic field excitation. Such issues make it difficult to reconstruct the three-dimensional profile. In this paper, a crack three-dimensional profile reconstruction method based on multidirectional magnetic field excitation is proposed. It establishes the simultaneous equations for different excitation directions. Then, it finds the solution satisfying all signals using the regularized conjugate gradient inversion method. This approach can combine the MFL information from different excitation directions to achieve more accurate defect reconstruction. Comparison results based on simulated datas between different directional excitations are carried out. Different artificial defects were also used to experimentally verify the feasibility of the present method.