The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical Imaging

The extension direction of welding defects is random and uncontrollable, while magneto-optical imaging detection has a good imaging effect on defects perpendicular to the magnetic field direction. At present, magneto-optical detection methods may fail to detect small weld defects parallel to the dir...

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Main Authors: Nvjie Ma, Xiangdong Gao, Yanxi Zhang, Shichao Gu, Jinyang Liu
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Metals
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Online Access:https://www.mdpi.com/2075-4701/15/4/340
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author Nvjie Ma
Xiangdong Gao
Yanxi Zhang
Shichao Gu
Jinyang Liu
author_facet Nvjie Ma
Xiangdong Gao
Yanxi Zhang
Shichao Gu
Jinyang Liu
author_sort Nvjie Ma
collection DOAJ
description The extension direction of welding defects is random and uncontrollable, while magneto-optical imaging detection has a good imaging effect on defects perpendicular to the magnetic field direction. At present, magneto-optical detection methods may fail to detect small weld defects parallel to the direction of the magnetic field. To overcome this problem, a non-destructive testing method based on magneto-optical imaging under a vertical combined magnetic field (VCMF) is proposed. The paper first establishes a simulation model to compare and analyze the magnetic leakage characteristics of cross grooves under a constant magnetic field (CMF), an alternating magnetic field (AMF), a rotating magnetic field (RMF), a parallel combined magnetic field (PCMF), and VCMF excitation, proving that detection does not easily fail under VCMF. Secondly, by changing the size of the CMF in the VCMF simulation model, it was found that, as the CMF intensity increases, a new maximum value will appear on the side of the defect contour close to the sample area. This maximum value increases with the increase of the CMF intensity, which can lead to misjudgment of the defect contour, that is, false contours. Finally, magneto-optical imaging was used to verify the imaging effect of weld defects under VCMFs. The results indicate that more comprehensive defect information can be detected under VCMFs. When the maximum value of the excitation current of the AMF is at least 12 times the excitation current of the CMF, there will be no false contour defects.
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spelling doaj-art-34f8ef02c7694c78839615a5f23006bc2025-08-20T02:18:19ZengMDPI AGMetals2075-47012025-03-0115434010.3390/met15040340The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical ImagingNvjie Ma0Xiangdong Gao1Yanxi Zhang2Shichao Gu3Jinyang Liu4School of Mechatronic Engineering, Guangdong Polytechnic Normal University, Guangzhou 510665, ChinaGuangdong Provincial Welding Engineering Technology Research Center, Guangdong University of Technology, Guangzhou 510006, ChinaGuangdong Provincial Welding Engineering Technology Research Center, Guangdong University of Technology, Guangzhou 510006, ChinaSchool of Intelligent Manufacturing, Guangzhou Maritime University, Guangzhou 510725, ChinaSchool of Mechatronic Engineering, Guangdong Polytechnic Normal University, Guangzhou 510665, ChinaThe extension direction of welding defects is random and uncontrollable, while magneto-optical imaging detection has a good imaging effect on defects perpendicular to the magnetic field direction. At present, magneto-optical detection methods may fail to detect small weld defects parallel to the direction of the magnetic field. To overcome this problem, a non-destructive testing method based on magneto-optical imaging under a vertical combined magnetic field (VCMF) is proposed. The paper first establishes a simulation model to compare and analyze the magnetic leakage characteristics of cross grooves under a constant magnetic field (CMF), an alternating magnetic field (AMF), a rotating magnetic field (RMF), a parallel combined magnetic field (PCMF), and VCMF excitation, proving that detection does not easily fail under VCMF. Secondly, by changing the size of the CMF in the VCMF simulation model, it was found that, as the CMF intensity increases, a new maximum value will appear on the side of the defect contour close to the sample area. This maximum value increases with the increase of the CMF intensity, which can lead to misjudgment of the defect contour, that is, false contours. Finally, magneto-optical imaging was used to verify the imaging effect of weld defects under VCMFs. The results indicate that more comprehensive defect information can be detected under VCMFs. When the maximum value of the excitation current of the AMF is at least 12 times the excitation current of the CMF, there will be no false contour defects.https://www.mdpi.com/2075-4701/15/4/340vertical combined magnetic field (VCMF)magneto-optical imagingspot weldingsimulation analysis
spellingShingle Nvjie Ma
Xiangdong Gao
Yanxi Zhang
Shichao Gu
Jinyang Liu
The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical Imaging
Metals
vertical combined magnetic field (VCMF)
magneto-optical imaging
spot welding
simulation analysis
title The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical Imaging
title_full The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical Imaging
title_fullStr The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical Imaging
title_full_unstemmed The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical Imaging
title_short The Influence of a Constant Magnetic Field on a Vertical Combined Magnetic Field in Magneto-Optical Imaging
title_sort influence of a constant magnetic field on a vertical combined magnetic field in magneto optical imaging
topic vertical combined magnetic field (VCMF)
magneto-optical imaging
spot welding
simulation analysis
url https://www.mdpi.com/2075-4701/15/4/340
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