Surface Crack Detection of Aluminum Alloy Using Injected Direct Current-Magnetic Field Measurement Method

Injected Direct Current-Magnetic Field Measurement (IDC-MFM) is a promising nondestructive technique for crack evaluation of aluminum alloy due to its high sensitivity to defect states. Finite element simulation and experiment were introduced in this research to reveal the relationship between the magnetic field and the crack size. The finite element simulation showed that the magnetic field at the defect increased with the currents, and the peak-to-peak value of the tangential component magnetic field B (ΔB) correlated with both the width and depth of the crack very well. The high-sensitivity tunnel magnetoresistance probe was used for crack detection of aluminum alloy specimens with different crack widths and depths, and the results show that the relationship between the ΔB and the crack was consistent with the simulation results, and ΔB has a nonlinear positive correlation with crack width and a linear positive correlation with crack depth. The results of the present work show that IDC-MFM has high sensitivity in crack size detection and is a feasible solution for the quantitative evaluation of cracks in aluminum alloy.