Magnetic mechanisms of magnetic flux leakage nondestructive testing

The widely applied magnetic flux leakage (MFL) nondestructive testing for ferrous materials has been simply explained by “MFL escaping from defects and being induced is exactly the MFL testing principle,” with a rough application for evaluation. Hence, we analyze the “escape” course of MFL generation using magnetic refraction and explain the reason why the MFL technology really exists in practice. Furthermore, we also point out that the presently so-called MFL testing technique essentially hides a different signal component arising from bump-shaped defects features unlike the MFL caused by concave-shaped ones, explained by another forming mechanism.