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High signal-to-noise ratio eddy thermal imaging detection method based on direction modulation

A technology with high signal-to-noise ratio and direction modulation, which can be used in material defect testing and other directions to solve problems such as poor detection results.

Active Publication Date: 2019-01-11
CHINA JILIANG UNIV
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Problems solved by technology

[0007] For the low signal-to-noise ratio problem of anti-corrosion coating crack detection, if the conventional modulation thermal imaging method is used to make the induced eddy current intensity change periodically as a whole, the detection effect is generally not good

Method used

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  • High signal-to-noise ratio eddy thermal imaging detection method based on direction modulation
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  • High signal-to-noise ratio eddy thermal imaging detection method based on direction modulation

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Embodiment approach 1

[0021] The structure of the eddy current thermal imaging system is as follows: figure 1 As shown, there is a crack 2 on the metal sample 1, the excitation coil 3 is wound on the ferrite core 4, and the alternating current is provided by the high-power high-frequency power supply 5, and the thermal imager 6 is located above the sample to observe the induction heating area , the software on the computer 7 controls the start and stop of the power supply 5, and at the same time collects the data of the thermal imager 6 for processing, analysis and display of results. Among them, the exciting coil 3 and the ferrite core 4 are composed of two sets of coils and magnetic cores whose excitation directions are perpendicular to each other. The structure is as follows: figure 2 As shown, the coil 3A is wound on the U-shaped magnetic core 4A, and the coil 3B is wound on the U-shaped magnetic core 4B. The induced eddy currents generated by the coil 3A and the coil 3B on the surface of the ...

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Abstract

The. The invention discloses a high signal-to-noise ratio eddy thermal imaging detection method based on direction modulation. According to the method, a rule that a crack in the eddy current thermalimaging detection has different responses to electromagnetic excitation in different directions is utilized, and a high-frequency magnetic field rotating at a low speed is adopted for excitation, so that thermal signals of a crack region are selectively modulated, and a crack detection result with a high signal-to-noise ratio is obtained after frequency domain analysis. According to the method, the modulation has selectivity to the crack, the crack position can generate a periodic heating power change (modulated) with a large amplitude, and the heating power of a non-crack position is almost not changed along with time (not modulated), so that when the modulation frequency of an observation signal and the amplitude and the phase of a frequency doubling component of the observation signal are analyzed, the crack and the non-crack position have higher contrast, and the crack detection signal-to-noise ratio is higher.

Description

technical field [0001] The invention relates to a non-destructive testing method, in particular to a high signal-to-noise ratio eddy current thermal imaging testing method based on direction modulation. Background technique [0002] Eddy current thermography is a non-destructive testing method mainly for surface and near-surface cracks of metal materials, which is a combination of eddy current testing and thermal imaging technology. The basic principle of eddy current thermal imaging is: metal samples generate induced eddy currents in the alternating electromagnetic field; when there are cracks on the surface or near the surface of the sample, the distribution of the eddy current field will be changed, which may lead to an abnormally large local eddy current density; When the magnetic field line is parallel to the crack, the eddy current density at the crack tip is generally much higher than other positions, and the eddy current density at the local contact point of the crac...

Claims

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Application Information

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IPC IPC(8): G01N25/72
CPCG01N25/72
Inventor 侯德鑫叶树亮
Owner CHINA JILIANG UNIV
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