Magnetically confined pulsed eddy current testing method and device

Abstract

The invention discloses a magnetic confinement pulsed eddy current detection method and apparatus. The method is characterized by the following steps: arranging an annular permanent magnet on the surface of a detected component, wherein the upper surface and the lower surface of the annular permanent magnet are opposite-polarity magnetic poles, and the center line of the permanent magnet is overlapped with the normal line of the surface of the detected component; sequentially and coaxially arranging reception coils and exciting coils inside the permanent magnet; loading a direct current in the exciting coils to generate a steady primary magnetic field; and closing the direct current in the exciting coils and meanwhile measuring induction voltages of the reception coils to obtain a detection signal. The apparatus comprises a pulsed eddy current sensor, an excitation control unit, a signal processing unit, an A / D transition unit and a calculating processor, wherein the pulsed eddy current sensor is provided with the annular permanent magnet. According to the pulsed eddy current detection method and apparatus, the annular permanent magnet, of which the upper surface and the lower surface are opposite-polarity magnetic poles is utilized to generate a bias magnetic field perpendicular to the surface of the detected component in the detected component, thereby confining outward diffusion of interaction eddy current in the detected component, and effectively improving detection sensitivity.

Description

technical field [0001] The invention relates to the field of non-destructive testing, in particular to a pulsed eddy current testing method and device based on magnetic confinement. Background technique [0002] In the pulsed eddy current testing technology, the electromagnetic response in the tested component can be equivalent to the downward and outward diffusion of eddy current, and the diffusion law of the eddy current can reflect the size and thickness of the tested area of ​​the test piece. By detecting the magnetic field generated by the eddy current, the detection of the thinning of the wall thickness of the measured component can be realized. However, due to the outward diffusion of the eddy current during detection, the eddy current energy is dispersed, which makes the detection sensitivity low. [0003] CN200910061369.2 discloses a method and device for detecting corrosion of components with a protective layer of magnetically conductive material, wherein by reduc...

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Problems solved by technology

However, due to the outward diffusion of the eddy current during detection, the eddy current energy is dispersed, which makes the detection sensitivity low

[0003] CN200910061369.2 discloses a method and device for detecting corrosion of components with a protective layer of magnetically conductive material, wherein by reducing the permeability of the material of the magnetically conductive protective layer, more energy is applied to the component to be tested, which can be used in a certain However, this method needs to magnetize the magnetic permeable protective layer to saturation or deep saturation

In addition, this method also has the following disadvantages: For example, according to a preferred embodiment of the prior art, the magnetization unit includes a permanent magnet and a yoke, and a permanent magnet is respectively attached to the two ends of the yoke, and the yoke The polarities of the magnets at both ends are opposite, and the magnetization direction of the measured component is parallel to its surface during detection, which does not restrain the outward diffusion of the eddy current; according to another specific implementation mode in this prior art, the magnetization unit is set It is defined as a DC magnetization coil. Although the magnetization direction of the measured component is perpendicular to its surface during detection, the DC magnetization coil of this method generates serious heat, which will also affect the detection accuracy.

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