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Structure surface crack monitoring method based on a rotating electromagnetic field

A technology of structural surface and electromagnetic field, applied in the direction of using electromagnetic means, measuring devices, using electrical devices, etc., can solve problems such as the influence of monitoring sensitivity, increase the difficulty and cost of making monitoring probes, and difficult to accurately monitor key structural cracks in industrial equipment. The effect of reducing the difficulty and cost of production and high measurement accuracy

Active Publication Date: 2021-05-28
CHINA UNIV OF PETROLEUM (EAST CHINA)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, it is difficult to accurately monitor the cracks in the key structures of industrial equipment by using the overall structural health monitoring method based on dynamic responses such as vibration, displacement, and acceleration.
Electromagnetic monitoring technology is currently an effective method for monitoring micro-structural cracks in key nodes of industrial equipment. However, in order to obtain the direction and size information of cracks, conventional electromagnetic monitoring methods need to use sensor arrays, which increase the monitoring probe. Manufacturing difficulty and cost, and monitoring sensitivity will be affected by crack direction

Method used

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  • Structure surface crack monitoring method based on a rotating electromagnetic field
  • Structure surface crack monitoring method based on a rotating electromagnetic field

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Experimental program
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Effect test

Embodiment 1

[0020] Such as figure 1 As shown, the monitoring system mainly includes a signal generator, a monitoring probe, a structure to be monitored, and a lock-in amplifier. The signal generator generates two sinusoidal signals with equal frequencies and amplitudes and initial phases of 0° and 90° respectively. The sinusoidal signals are respectively Loaded on the upper coil and the lower coil of the excitation coil, the excitation coil will induce a rotating electromagnetic field that changes periodically with time on the structure under test. Compared with the spiral induced electromagnetic field induced by conventional eddy current testing, the rotating electromagnetic field is rotating. The uniform field has the same detection sensitivity for cracks in any direction.

[0021] Further, such as figure 2 As shown, the upper coil and the lower coil are composed of two rectangular coils, the rectangular coils are symmetrically distributed, and the winding directions are opposite. At ...

Embodiment 2

[0023] The signal generator generates 10kHz, 2-way sinusoidal signals with 5V initial phases of 0° and 90° respectively, and the two-way sinusoidal signals are respectively loaded on the upper coil and the lower coil of the excitation coil, and the excitation coil induces the space in the measured structure. The induced electromagnetic field rotates periodically with time. When there is a crack, the induced electromagnetic field will be disturbed. The magnetic field sensor is located at the center of the excitation coil. The magnetic field sensor will pick up the magnetic field perpendicular to the surface of the measured structure, and then convert it into Electrical signal Bz. The sinusoidal signal with an initial phase of 0° is used as a reference signal, and Bz is used as an input signal for lock-in amplification processing, and the amplitude of Bz is F=50mV and the phase P=136°.

[0024] Further, before the formal monitoring, the position without defect is monitored, and ...

Embodiment 3

[0027] According to the steps of the second implementation case, according to the requirements of structural safety inspection, the monitoring system can be operated all the time to monitor the key positions of the tested structure in real time, or it can be monitored according to the detection cycle of industrial equipment, and the monitoring system can be operated at regular intervals. Collect crack information at key locations of the tested structure.

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Abstract

The invention discloses a structure surface crack monitoring method based on a rotating electromagnetic field, which comprises the following steps of: respectively loading two paths of sinusoidal signals with an initial phase difference of 90 degrees on an exciting coil, inducing the rotating electromagnetic field which periodically changes along with time on a monitored structure, and when the monitored structure encounters a crack, disturbing an induced current, meanwhile, disturbing a secondary magnetic field generated by the induction current, wherein a magnetic field sensor is used for picking up a changing magnetic field signal perpendicular to the surface direction of the measured object in the space, the picked-up magnetic field signal is subjected to phase-locked amplification and is decomposed into an amplitude and a phase, and amplitude information can be used for representing the danger degree of the influence of the crack on the structure, the phase information can be used for representing the angle of the crack, and the method provided by the invention can obtain the angle and danger degree of the crack by using a single sensor, so that the manufacturing cost of the monitoring probe can be greatly reduced.

Description

technical field [0001] The invention relates to the field of non-destructive detection signal processing, in particular to a method for monitoring cracks on the surface of rotating electromagnetic field structures. Background technique [0002] Industrial equipment such as oil pipelines, jacket platforms, and thermal pressure vessels are exposed to alternating loads, high temperatures, high pressures, and corrosive media for a long time, and cracks are easily generated at key nodes. If early cracks cannot be effectively monitored, when special working conditions are encountered , the crack will expand rapidly and lead to structural failure, resulting in safety accidents. Therefore, cracks in key nodes of the structure seriously threaten the safe operation of industrial equipment. Timely monitoring of cracks in key nodes of industrial equipment and keeping track of the crack growth status of key nodes are crucial to the safe operation and maintenance of industrial equipment. ...

Claims

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Application Information

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IPC IPC(8): G01B7/30G01N27/83
CPCG01B7/30G01N27/83
Inventor 赵建明李伟袁新安李肖赵建超丁建喜唐鑫袁亚星
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)
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