A novel method of omnidirectional defects detection by MFL testing under single axial magnetization at the production stage of lathy ferromagnetic materials

Abstract

Aiming to the current situation that single axial magnetization can hardly qualified for omnidirectional defects detection, meanwhile, conventional complex magnetization method features with low speed and low efficiency. Thus, a novel method of magnetic flux leakage (MFL) testing for omnidirectional defects based on super-strong single axial magnetization as well as the corresponding detection apparatus were proposed. First, principles of single axial magnetization method were introduced, where a through-coil with high direct current was mainly used to generate the super-strong magnetic field. Then, methods of omnidirectional defects detection through magneto sensor arrays were concretely presented. What’s more, details of equation sets for lateral and longitudinal defects detection and classification were given. Additionally, a summation and comparison combination method was put forward and different defect signal amplitudes were compensated. Naturally, a unified judgment for omnidirectional defects inspection with same sensitivity or accuracy was formed. Most importantly, series of simulations and experiments were conducted, and finally, the feasibility and reliability of the new MFL testing method were demonstrated by those results. The obvious advantages for the suggested method are that it not only makes the detection for omnidirectional defects under single axial magnetization possible, but also the low economic cost, high speed and high efficiency detection for both lateral and longitudinal defects adaptable for various shaped ferromagnetic objects with great application promise in engineering is ultimately accomplished.