Magneto-Optical Imaging Characteristics of Weld Defects under Alternating Magnetic Field Excitation

This paper examines the characteristics of magneto-optical images of weld defects under alternating magnetic field excitation. Weld defects such as non-penetration, surface cracks and sub-surface cracks were detected by magneto-optical imaging method. The weld defects are subjected to magneto-optical imaging nondestructive testing experiments under alternating magnetic field excitation, and the magneto-optical images are subjected to image processing to obtain binarization and three-dimensional grayscale. Also, the difference of the magneto-optical image of weld defects was obtained by contrast analysis. Experimental results show that there is a significant difference in the light and dark images of non-penetration welds, and the difference between the bright and dark changes of the magneto-optical images is smaller than that of non-penetration. Under the same excitation conditions, the leakage flux of welds with non-penetration is stronger than that of weld cracks.