CN113433212B - Uniform field excitation directional eddy current probe with high interference resistance and detection method - Google Patents

Abstract

The probe comprises an excitation part and a detection part, wherein the excitation part is uniformly wound by a rectangular framework and a plurality of turns of wires to form a rectangular excitation coil; the detection part consists of two disc-type small coils with axes perpendicular to the normal direction of the metal member to be detected and the same winding direction, and the middle wires on the lower surface of the rectangular exciting coil are symmetrically distributed by taking the middle wires as symmetry axes. During detection, excitation signals are introduced into the rectangular excitation coil, and a relatively uniform vortex field is induced by the metal component to be detected below the coil; since the rectangular excitation coil is large enough, the detection signals of the two detection coils are approximately the same when no defect exists; when the detection device is defective, the defect can generate disturbance to the uniform vortex field, and the differential signals of the two small coils are taken as target signals, so that on one hand, the detection sensitivity can be enhanced, and meanwhile, the influence of lift-off noise can be effectively reduced. And by rotating the probe, analyzing the relation between the scanning direction and the scanning signal, and realizing the directional identification of the defects.

Description

Uniform field excitation directional eddy current probe with strong anti-interference and detection method

technical field

The invention relates to an electromagnetic non-destructive detection probe, in particular to a high-sensitivity anti-interference directional uniform field excitation differential output eddy current probe and a detection method.

Background technique

Metal components are used in many occasions, such as aerospace, additive manufacturing, nuclear power and other fields. Under extreme service conditions, metal components will inevitably produce defects such as micro cracks or residual stress, which will cause component damage and failure, and lead to serious industrial accidents. Therefore, regular non-destructive evaluation of such defects is essential.

The eddy current testing method is a non-destructive testing method based on the principle of electromagnetic induction. It has the advantages of non-contact, no coupling medium, high detection speed, easy automatic detection, and high detection sensitivity for surface and near-surface defects. In the crack detection of metal components, the traditional eddy current probe often uses a small disk coil with a magnetic core. This probe is a pen type eddy current probe, and the overall size of the probe is small, so its detection spatial resolution and sensitivity are high. However, the probe generally adopts the self-excitation and self-detection mode, which causes the detection noise of the probe to be large, such as lift-off noise, tilt noise, etc., that is, the probe has weak anti-interference ability and poor robustness. In addition, the disc-type small coil has a circular axisymmetric structure, which cannot realize the directional identification of defects.

In order to make up for the problems of the traditional disk coil probes, which are susceptible to noise interference, poor robustness, and unable to detect the direction of defects, etc., the present invention designs a uniform-field-excited directional eddy current probe with strong anti-interference.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the purpose of the present invention is to provide a uniform field excitation directional eddy current probe and a detection method with strong anti-interference. The probe can effectively enhance the defect detection sensitivity, reduce the influence of lift-off noise, and at the same time, effectively identify the direction of the defect.

In order to achieve the above object, the present invention adopts following technical scheme:

The uniform field excitation directional eddy current probe with strong anti-interference is an external eddy current detection probe, which is placed on the surface of the metal component 1 to be tested for scanning and detection; it includes an excitation part and a detection part. The excitation part It is a rectangular excitation coil, including a large rectangular frame 2 and a multi-turn wire 4 evenly wound on the large rectangular frame; the detection part is two disc-shaped small coils 3, located directly below the rectangular excitation coil.

The detection part is a differential detection unit, which is composed of two small disc-shaped coils 3 whose axes are perpendicular to the normal direction of the metal component 1 to be tested; The small coils are symmetrically distributed on the lower surface of the rectangular excitation coil, and the position is the center of the lower surface of the rectangular excitation coil, and there is a lift-off distance from the rectangular excitation coil.

The wires of the two disc-shaped small coils 3 in the detection part are wound in the same direction.

The final detection signal of the detection part is the differential signal of the two small disc coils 3 .

The size of the rectangular excitation coil is at least one order of magnitude larger than the size of the two small disk coils 3, so that the two small disk coils are in a relatively uniform excitation magnetic field. The axial direction of the rectangular excitation coil is consistent, on the one hand, it improves the detection sensitivity of the probe to defects, on the other hand, it also effectively reduces the influence of lift-off noise, and improves the anti-interference ability of the probe against noise.

The detection method of the uniform field excitation directional eddy current probe with strong anti-interference,

First, a steady-state sinusoidal excitation current is passed into the rectangular excitation coil, and the steady-state sinusoidal excitation current will generate an alternating magnetic field, that is, a direct magnetic field, and the metal component 1 to be tested in the alternating magnetic field will generate a relatively uniform eddy current field The alternating eddy current field will induce a secondary magnetic field again, and the composite magnetic field after the superimposition of the direct magnetic field and the secondary magnetic field will cause voltage signals to be generated at the two ends of the two disk-type small coils 3; Due to the influence of defects of different sizes, the induced secondary magnetic field will also produce corresponding changes, and then cause different voltage signals to be generated in the two small disc coils 3;

Secondly, compared with the small disk coil 3 in the detection part, the size of the rectangular excitation coil is designed to be large enough so that the two small disk coils can be in a relatively uniform magnetic field, and the differential signal of the two small disk coils 3 is taken is the final detection signal; when there is no defect in the uniform eddy current field area, the detection signals of the two disc-type small coils 3 are the same, and the final detection differential signal should be 0 in principle; and when there is a defect in the uniform eddy current field area , the defect will disturb the uniform eddy current field, and the final detected differential signal will also be disturbed at this time; in addition, since the axial directions of the two disc-shaped small coils are consistent with the axial directions of the rectangular excitation coil, the enhanced secondary magnetic field will The penetration rate of the detection coil;

Finally, the rectangular excitation coil of the excitation part and the two disc-shaped small coils 3 of the detection part are integrated, which are placed on the surface of the metal component 1 to be tested for scanning; the detection signal is compared with the detection signal of the non-defective component. Compare to determine whether there is a defect in the current scanning area; if there is a defect, the area of the metal component to be tested is scanned repeatedly to finally determine the position of the defect, and further combine the signal processing to analyze and evaluate the size of the defect;

At the same time, the eddy current induced by the rectangular excitation coil in the metal component 1 to be tested has a directional characteristic. By rotating the probe, the relationship between the scanning direction and the scanning signal is analyzed to effectively identify the defect direction.

Compared with the prior art, the present invention has the following advantages:

The invention is a uniform field excitation directional eddy current probe with strong anti-interference. The rectangular excitation coil generates a relatively uniform eddy current field in the metal member, which can effectively reduce the influence of lift-off noise and improve the anti-interference ability of the probe to noise. The detection part is composed of two disc-shaped small coils whose axes are perpendicular to the normal direction of the metal component to be tested. This arrangement method enhances the penetration rate of the secondary magnetic field to the detection coil, effectively enhancing the detection signal and detection sensitivity; The wires of the two disc-type small coils have the same winding direction, which makes it easier to analyze and process the signal; the detection signals of the two disc-type small coils have the same noise for difference, which can reduce the noise.

Description of drawings

Fig. 1 is a schematic diagram of the placement of the probe and the metal component to be tested according to the present invention.

Fig. 2 is a schematic diagram of the cooperation between the probe of the present invention and the eddy current detection system.

Fig. 3 is a schematic structural diagram of the exciting coil part of the present invention.

Fig. 4 is a schematic structural diagram of the detecting coil part of the present invention.

Detailed ways

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

As shown in Figure 1, this embodiment is an eddy current detection probe for metal component defects. Field excited directional eddy current probes. The external eddy current detection probe includes an excitation part and a detection part. During detection, the excitation part and the detection part are integrated, and the detection part needs to be close to the metal component 1 to be tested and the excitation coil to ensure that the lift-off is small, the eddy current field strength is large, and the detection coil can pick up more defect signal. The excitation part is a rectangular excitation coil, including a large rectangular frame 2 and a multi-turn wire 4 uniformly wound on the large rectangular frame; The vertical disk-type small coil 3 is formed. Taking the central wire on the lower surface of the rectangular excitation coil as the axis of symmetry, two disc-type small coils 3 are symmetrically distributed on the lower surface of the rectangular excitation coil, and the position is the center of the lower surface of the rectangular excitation coil, and there is a certain gap between the rectangular excitation coil and the rectangular excitation coil. distance.

As shown in Figure 2, the process flow of the uniform field excitation directional eddy current probe detection system with strong anti-interference is as follows: the signal generator generates a steady-state sinusoidal excitation current; the steady-state sinusoidal excitation current is passed into the power amplifier to increase the power of the excitation current Then the amplified steady-state sinusoidal excitation current is connected to the rectangular excitation coil; two disc-type small coils 3 receive the voltage signal containing the defect information of the inspected component, and the detection signal is transmitted to the The signal acquisition and display system analyzes and processes the signals.

As shown in Figure 3, the excitation part is a rectangular coil, including a large rectangular frame 2, on which a multi-turn wire 4 is uniformly wound, and the wire bundles of each layer and the wire bundles between layers are tight and uniform Distribution.

As shown in FIG. 4 , the detection part is a differential detection unit, which is composed of two small disc-shaped coils 3 whose axes are the same as those of the rectangular excitation coil. Taking the central wire on the lower surface of the rectangular excitation coil as the axis of symmetry, two disc-type small coils are symmetrically distributed on the lower surface of the rectangular excitation coil, and the position is the center of the lower surface of the rectangular excitation coil, and there is a certain lift-off distance from the rectangular excitation coil. distance. The axial directions of the two small disc-shaped coils 3 are consistent with the axial directions of the rectangular excitation coil, and the wires of the two small disc-shaped coils 3 are wound in the same direction, which is more conducive to the analysis and processing of defect signals.

The working principle of the present invention is as follows: the present invention is to realize the detection and evaluation of tiny cracks or residual stress of the metal component to be tested.

First, a steady-state sinusoidal excitation current is passed into the rectangular excitation coil, and the steady-state sinusoidal excitation current will generate an alternating magnetic field (direct magnetic field), and the metal component 1 to be tested in the alternating magnetic field will generate a relatively uniform eddy current field. The alternating eddy current field will induce a secondary magnetic field, and the composite magnetic field after the superimposition of the direct magnetic field and the secondary magnetic field will cause voltage signals to be generated at both ends of the two small disk coils 3 . Due to the influence of different shapes and different sizes of defects in the metal component 1 to be tested, the induced secondary magnetic field will also produce corresponding changes, thereby causing different voltage signals to be generated in the two small disc coils 3 .

Secondly, compared with the small disk coil 3 in the detection part, the size of the excitation coil is designed to be large enough so that the two small disk coils can be in a relatively uniform magnetic field. The differential signal of the two small disk coils 3 is Finally detect the signal. When there is no defect in the uniform eddy current field area, the detection signals of the two disc-type small coils 3 are the same, and the final detection differential signal should be 0 in principle; and when there is a defect in the uniform eddy current field area, the defect will affect the uniform eddy current If the field is disturbed, the final detected differential signal will also be disturbed. In addition, the axial direction of the two disc-shaped small coils is consistent with the axial direction of the rectangular excitation coil through the design, so as to enhance the penetration rate of the secondary magnetic field to the detection coil. Through the above series of designs, on the one hand, the detection sensitivity of the probe to defects can be improved, on the other hand, the influence of lift-off noise can be effectively reduced, and the anti-interference ability of the probe to noise can be improved.

Finally, the rectangular coil of the exciting part and the two small disc-shaped coils 3 of the detecting part are integrated, which are placed on the surface of the metal component 1 to be tested for scanning. The probe first scans on a non-defective metal component to obtain a non-defect signal, and then scans on the component to be tested to obtain a detection signal, and compares the detection signal with the non-defect signal to determine whether there is a defect in the current scanning area. If there is a defect, the area of the metal component to be tested can be scanned repeatedly to finally determine the position of the defect, and further combined with signal processing analysis to evaluate the size of the defect.

At the same time, the eddy current induced in the metal component 1 by using the rectangular excitation coil has the characteristic of directionality, and the relationship between the scanning direction and the scanning signal can be analyzed by rotating the probe to effectively identify the defect direction.

Claims (3)

1. The directional eddy current probe is excited by a uniform field with strong anti-interference, and is characterized in that: the probe is an external eddy current detection probe, and is arranged on the surface of a metal component (1) to be detected for scanning detection; the device comprises an excitation part and a detection part, wherein the excitation part is a rectangular excitation coil and comprises a large rectangular framework (2) and a plurality of turns of wires (4) uniformly wound on the large rectangular framework; the detection part is two small disc coils (3) which are positioned right below the rectangular exciting coils;

the detection part is a differential detection unit and consists of two small disc coils (3) with axes perpendicular to the normal direction of the metal member (1) to be detected; the center wire of the lower surface of the rectangular exciting coil is used as a symmetry axis, two small disc coils are symmetrically distributed on the lower surface of the rectangular exciting coil, the position of the small disc coils is the center of the lower surface of the rectangular exciting coil, and a lifting distance is reserved between the small disc coils and the rectangular exciting coil;

the size of the rectangular exciting coil is at least 1 order of magnitude larger than that of the two small disc coils (3), so that the two small disc coils are in a relatively uniform exciting magnetic field, the axial directions of the two small disc coils (3) are consistent with the axial directions of the rectangular exciting coil, on one hand, the detection sensitivity of the probe to defects is improved, on the other hand, the influence of lift-off noise is effectively weakened, and the anti-interference capability of the probe to noise is improved;

the detection method of the uniform field excitation directional eddy current probe with strong interference resistance,

firstly, a steady-state sinusoidal excitation current is introduced into a rectangular excitation coil, the steady-state sinusoidal excitation current can generate an alternating magnetic field, namely a direct magnetic field, and a metal component (1) to be detected in the alternating magnetic field can generate a relatively uniform vortex field; the alternating vortex field can generate a secondary magnetic field, and the composite magnetic field obtained by superposition of the direct magnetic field and the secondary magnetic field can enable two ends of the two small disc coils (3) to generate voltage signals; the secondary magnetic field induced by the influence of the defects of different forms and different sizes of the metal component (1) to be detected also generates corresponding changes, so that different voltage signals are generated in the two small disc coils (3);

secondly, the size of the rectangular exciting coil is designed to be large enough relative to the disc-shaped small coil (3) of the detection part, so that the two disc-shaped small coils can be in a relatively uniform magnetic field, and the differential signals of the two disc-shaped small coils (3) are taken as final detection signals; when the uniform vortex field area is free of defects, the detected signals of the two small disk coils (3) are the same, and the final detected differential signal is supposed to be 0 in principle; when the uniform vortex field area has defects, the defects can generate disturbance on the uniform vortex field, and the final detected differential signal can be disturbed; in addition, as the axial directions of the two small disc-shaped coils are consistent with the axial directions of the rectangular exciting coils, the passing rate of the secondary magnetic field to the detecting coils is enhanced;

finally, the rectangular exciting coil of the exciting part and the two small coils (3) of the detecting part are integrated, and are arranged on the surface of the metal member (1) to be detected for scanning; comparing the detected signal with the detected signal of the non-defective member to judge whether the current scanning area has a defect; if the defect exists, repeatedly scanning the region of the metal member to be detected, finally determining the position of the defect, and further analyzing and evaluating the size of the defect by combining with signal processing;

meanwhile, by utilizing the characteristic that eddy currents induced by the rectangular exciting coil in the metal component (1) to be detected have directivity, the relation between the scanning direction and the scanning signal is analyzed through the rotating probe, and the defect direction is effectively identified.

2. The high interference resistance uniform field excitation directional eddy current probe according to claim 1, wherein: the wire winding directions of the two small disc coils (3) of the detection part are the same.

3. The high interference resistance uniform field excitation directional eddy current probe according to claim 1, wherein: the detection part finally detects that the signal is a differential signal of two small coils (3).