3D defect reconstruction method based on projection Levenberg-Marquart algorithm

Magnetic flux leakage detection is widely used in the on-line detection of ferromagnetic materials and equipment. It is an effective defect detection method. How to reconstruct the outline of three-dimensional irregular defect by using magnetic flux leakage signal is the key problem in magnetic flux leakage detection. However, the finite element model of magnetic flux leakage detection for three-dimensional irregular defects requires a large amount of computation, and the ill-posed defect reconstruction problem makes it difficult to obtain the accurate outline of irregular defects. In this paper, an element magnetic dipole band superposition model is proposed for calculating magnetic flux leakage signals of three-dimensional irregular defects, and the validity of the forward model for calculating magnetic flux leakage signals is demonstrated. For the high-dimensional optimization problem of three-dimensional defect contour reconstruction, a projection Levenberg-Marquart algorithm with boundary constraints is proposed. Reconstruction of three - dimensional irregular defect contour is realized. The simulation results show that the defect reconstruction method does not need a lot of magnetic flux leakage detection data, and the contour reconstruction results have high accuracy.