A quasi-static magnetic leakage detection method based on magneto-electric composite

Magnetic flux leakage (MFL) testing is widely used for structural damage monitoring of ferromagnetic materials. However, AC MFL encounters challenges in identifying buried defects due to the skin effect. DC MFL induces residual magnetism on the material surface under the influence of a strong magnetizing field, which often interferes with the leakage field signal. Therefore, this paper presents a quasi-static MFL detection method based on magneto-electric (ME) composite. By using the nonlinear characteristics of magnetostrictive curves, the detection of quasi-static magnetic leakage fields in Metglas/PZT composites is realized by frequency conversion technique. The feasibility of the method is demonstrated by theoretical analysis and simulation studies. Next, the proposed MFL detection probe is fabricated and the corresponding experimental platform for defect detection is established. The experimental results show that the proposed method has a high sensitivity for surface defects of 0.5 mm width, while the method using DC magnetization has large signal fluctuations and even leads to defect omission due to the interference of residual magnetism. The ME signal under quasi-static magnetization also exhibits a good linear relationship with defect depth. For subsurface defects, 0.5 Hz and 1.0 Hz are capable of detecting defects up to a maximum depth of 9 mm (close to DC magnetization) and the defect signal is larger than the DC magnetization signal. In conclusion, the proposed method demonstrates outstanding detection performance for both surface and subsurface defects.