Magnetic anomaly characteristics of surface crack defects in a titanium alloy plate

A finite element simulation analysis of micromagnetic signals of surface crack defects on a titanium (Ti) alloy plate was performed, and a verification experiment was designed. Simulation results showed that micromagnetic detection exhibited strong detection capability when used for crack defects with 0.15–0.6 mm widths. Good detection capability could be ensured if the detection lift-off height was controlled within 1 mm. The best detection effect was achieved when the angle of crack inclination was 90°. Micromagnetic detection was highly sensitive when the crack space between two adjacent independent crack defects was larger than 0.4 mm. Experimental results showed that the critical defect width of surface cracks in the Ti alloy was 0.6 mm. When the defect width was less than the critical value, the magnitude of magnetic anomaly increased with the increase in crack width, and the sensitivity of micromagnetic detection was enhanced. The experimental results were consistent with the simulation ones. Moreover, micromagnetic detection could accurately locate the surface crack defects of Ti alloy. The defect morphology could be visually displayed using 2D imaging on the basis of the magnetic gradient characteristics, but sufficiently accurate quantification of defect size remained a challenge.