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A method of non-destructive testing using flux leakage rate of change

A non-destructive testing and rate-of-change technology, applied in the direction of material magnetic variables, etc., can solve the problems of high energy consumption and large size of the magnetizer, and achieve the effect of overcoming the large volume, avoiding background noise, and meeting the requirements of engineering quality evaluation.

Inactive Publication Date: 2016-07-06
XIAMEN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The main technical problem to be solved by the present invention is to provide a method of non-destructive testing, which overcomes the disadvantages of large magnetizer volume and high energy consumption in the existing testing methods

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  • A method of non-destructive testing using flux leakage rate of change
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  • A method of non-destructive testing using flux leakage rate of change

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Embodiment Construction

[0023] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0024] refer to figure 1 , select a Q235 steel plate with a thickness of 10 mm as the ferromagnetic material 1 to be tested. The magnetizer is composed of a yoke 2, an excitation 3 and an AC excitation coil 4. In this embodiment, the excitation 3 is preferably a permanent magnet excitation; The magnetic excitation selects a neodymium-iron stilt magnet with a length of 25*width 25*height of 10mm and installs it at the pole shoe of the yoke 2; side.

[0025] further reference figure 2 , place the magnetizer on the steel plate according to the first lift-off value d1. In this embodiment, d1 is preferably 2mm. An AC sine wave excitation signal with a frequency of 10HZ and an amplitude of 0.3A is generated by an arbitrary waveform generator, and the This excitation signal is applied to the AC excitation coil 4 . The detection coil 5 is selecte...

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Abstract

The invention discloses a method for nondestructive testing by use of change rate of magnetic flux leakage, belonging to the technical field of nondestructive testing. A static magnetic field with low strength, which is generated by direct current or permanent magnet excitation, is used for magnetizing a ferro magnetic material to be tested; the ferro magnetic material to be tested generates static bias under the action of a magnetizing field and is in a shallow magnetizing state; low-frequency low-amplitude alternating excitation is applied to the ferro magnetic material to be tested, and a magneto-dependent sensor or a detecting coil is utilized for picking up alternating excitation response above a testing point; the alternating excitation response corresponds to the change rate of magnetic flux leakage and has nothing to do with the strength of the leakage magnetic field, if the response strength delta B1 is more than or equal to the set threshold value delta B, the condition that the testing point has a defect is judged; otherwise, the condition that the testing point does not have a defect is judged. According to the method, the ferro magnetic material can be prevented from being magnetized in a saturation condition and the volume of a magnetizer can be reduced by use of the character of the change rate of magnetic flux leakage; the alternating excitation response is used as a detection signal, and signal amplification and follow-up treatment are facilitated.

Description

technical field [0001] The invention relates to a non-destructive detection technology applicable to ferromagnetic materials, in particular to a new type of magnetic flux leakage detection technology with DC or permanent magnet excitation. Background technique [0002] The current non-destructive testing methods used in steel plate testing include magnetic flux leakage testing, ultrasonic testing, far-field eddy current testing, and radiographic testing. The magnetic flux leakage detection method has the advantages of simple probe, high detection speed and accuracy, easy automation, high detection sensitivity, no need to clean the surface and use couplant during the detection process, so it is the most widely used pipeline and storage at home and abroad in recent years. Can defect detection technology. [0003] Chinese patent CN10358688A "A DC motor-driven variable-diameter pipeline external magnetic flux leakage detector" discloses a DC motor-driven variable-diameter pipel...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N27/83
Inventor 吴德会杨秀淼黄一民李雪松
Owner XIAMEN UNIV
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