Abstract
As a promising non-destructive testing (NDT) method, magnetic flux leakage (MFL) testing has been widely used for steel structure inspection. However, MFL testing still faces a great challenge to detect inner defects. Existing MFL course researches mainly focus on surface-breaking defects while that of inner defects is overlooked. In the paper, MFL course of inner defects is investigated by building magnetic circuit models, performing numerical simulations, and conducting MFL experiments. It is found that the near-surface wall has an enhancing effect on the MFL course due to higher permeability of steel than that of air. Further, a high-sensitivity MFL testing method consisting of Helmholtz coil magnetization and induction coil with a high permeability core is proposed to increase the detectable depth of inner defects. Experimental results show that inner defects with buried depth up to 80.0 mm can be detected, suggesting that the proposed MFL method has the potential to detect deeply-buried defects and has a promising future in the field of NDT.
Highlights
As a powerful and highly efficient non-destructive testing (NDT) method, magnetic flux leakage (MFL) testing is conducted based on the physical phenomenon that a ferromagnetic specimen in a certain magnetization state will produce magnetic flux leakage if any discontinuities are presented in it [1]
In the MFL application, two common questions of MFL testing for inner defects must be figured out as follows: (1) why inner defects have a lower sensitivity than surface-breaking ones? (2) What is the detectable depth of MFL testing for inner defects? The first question is about MFL course of inner defects
In order to investigate the magnetic effect of near-surface wall on the MFL course, the magnetic flux distributions inside the specimen are simulated as indicated by rainbow color map
Summary
As a powerful and highly efficient non-destructive testing (NDT) method, magnetic flux leakage (MFL) testing is conducted based on the physical phenomenon that a ferromagnetic specimen in a certain magnetization state will produce magnetic flux leakage if any discontinuities are presented in it [1]. The distorted magnetic flux caused by the defect firstly passes through the near-surface wall with a thickness of db3 (i.e., the buried depth of the defect), leaks into the air, and reaches the sensor location.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
