Comparison between Magnetic Field Distribution Analysis and Metal Magnetic Memory (MMM) Testing Results Around Artificial Cracks under Loads

In this research, the behavior of the metal magnetic memory (MMM) signals near the artificial cracks located the back side of A572 specimens are tried. The materials are used as power transmission tower material. The variations of the MMM signals with the applied tensile loads are studied. It is found that both the tangential component, Hp(x), and the normal component, Hp(y), are effectively showed the stress concentration zone (SCZ) caused by discontinuities. The results of modeling and MMM technique showed that the loads create residual stress and lead to the change of magnetic field strength around artificial cracks in the specimen and that is relatively different from the crack free area. This research is useful for expending MMM method as a tool of nondestructive testing method for detecting subsurface flaws.