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Ferro magnetic material irregular crack ACFM visual imaging method

A technology of ferromagnetic materials and imaging methods, applied in the direction of material magnetic variables, etc., can solve the problems of complex electromagnetic field distortion, inability to visually display the surface contour of irregular cracks, and inability to realize imaging display of irregular cracks.

Active Publication Date: 2019-09-17
CHINA UNIV OF PETROLEUM (EAST CHINA)
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The existing AC electromagnetic field detection technology is judged based on the characteristic signals Bx and Bz or their butterfly diagrams, where the Bx and Bz signals are parallel to the surface of the test piece (parallel to the scanning direction of the probe) and perpendicular to the surface of the test piece, respectively. Magnetic field signal, this characteristic signal can only determine the existence of cracks perpendicular to the induced current, and cannot realize the imaging display of irregular cracks
The electromagnetic field distortion around the irregular cracks of ferromagnetic materials is complicated, and the existing technical methods cannot directly display the surface contours of the irregular cracks

Method used

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  • Ferro magnetic material irregular crack ACFM visual imaging method
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Embodiment 1

[0029] figure 1 The flow chart of the ACFM visual imaging method for irregular cracks in ferromagnetic materials provided by the embodiment of the present invention includes:

[0030] S1. Prepare a carbon steel test block. There are irregular cracks on the surface of the test block. The irregular cracks are composed of four cracks at 0°, 30°, 60° and 90°. The crack depth is 2.0mm and the width is 0.8mm. figure 2 shown. The schematic diagram of the probe grid scanning path is as follows: image 3 As shown, the scanning direction of the probe is defined as the X direction. Using the grid scanning method, the AC electromagnetic field detection probe is used to detect the 89.0mm×88.0mm area along the scanning path at the same height plane on the surface of the irregular crack of the test block, and the X direction scans The search step length is 1.0mm, the number of equidistant position points on the scanning path in the X direction is 90, the spacing of the scanning path in th...

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Abstract

The invention discloses a ferro magnetic material irregular crack ACFM visual imaging method, and relates to the field of nondestructive detection defect imaging technologies. The method comprises the steps of acquiring a magnetic field signal Bz amplitude matrix of irregular crack alternating current electromagnetic field surface sweeping results with the aid of a grid scanning method; acquiring an X direction gradient field matrix and a Y direction gradient field matrix of a distorted magnetic field signal Bz by using a gradient field, and reflecting the aggregation condition of a sensing current around an irregular crack and a leakage magnetic field in an original excitation magnetic field; further performing extreme value acquisition, background removal, and normalization operations on the two direction gradient field matrixes to acquire two direction normalization matrixes; and summing the two direction normalization matrixes, thus achieving an intuitive imaging result of the irregular crack surface profile of the ferro magnetic material. According to the method provided by the invention, the visual assessment of the crack of the ferro magnetic material and the accurate prediction of the residual service life of the ferro magnetic material are facilitated.

Description

technical field [0001] The invention relates to the technical field of non-destructive detection defect imaging, in particular to an ACFM visualization imaging method for irregular cracks in ferromagnetic materials. Background technique [0002] Marine structures have served in seawater for a long time. Under the joint action of corrosion, storms, ocean currents, alternating loads, and self-weight, various types of crack defects are easily generated on the surface of the structure, threatening the safe service of the structure. Alternating Current Field Measurement (ACFM) technology is a new electromagnetic non-destructive testing technology, which has the characteristics of non-contact detection, no need to clean up attachments, quantitative evaluation, etc. It is widely used in the detection of defects in marine structures. It uses detection probes in The uniform current induced on the surface of the conductive test piece, the current disturbs around the defect and causes ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N27/83
CPCG01N27/83Y02A90/30
Inventor 袁新安李伟陈国明赵建明王振翔刘阳王勇胜王克宇
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)
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