CN111812193B - Array eddy current probe for actively relieving electromagnetic coupling between adjacent coils - Google Patents

Abstract

The present invention proposes an array eddy current probe that actively releases the electromagnetic coupling between adjacent coils, which mainly solves the two shortcomings of the existing array eddy current probe that uses a shielding cover to passively shield the electromagnetic coupling: 1. It blocks the Joule heat of the detection coil in the cover and The external convective heat transfer channel will easily cause the temperature rise of the coil and cause temperature drift errors; 2. Increase the volume of the probe, and the spatial resolution of the probe will decrease. The technical solution is: outside the detection coil of the probe, two auxiliary coils coaxial with the detection coil are arranged, and the magnetic field generated by the auxiliary coil weakens the external magnetic field generated by the detection coil, thereby reducing the magnetic field interference of adjacent detection coils. The auxiliary coil is equipped with a metal slide, and moving the slide can change the length and number of turns of the auxiliary coil connected to the loading circuit, thereby adjusting the weakening degree of the external magnetic field to meet the different requirements of different application scenarios for the degree of electromagnetic decoupling of adjacent coils. Compared with the existing array eddy current probe, the probe proposed by the invention has smaller volume and smaller temperature drift error.

Description

An array eddy current probe that actively decouples the electromagnetic coupling between adjacent coils

technical field

The invention belongs to the technical field of non-destructive testing, and further belongs to the technical field of eddy current testing, in particular to an array eddy current probe for non-destructive testing, in particular to an array eddy current probe without a shield that reduces electromagnetic coupling between adjacent detection coils probe.

Background technique

Eddy current testing is a non-destructive testing technology widely used in the industrial field. Its working principle is based on the principle of electromagnetic induction: when the detection coil with alternating current is close to the metal conductor, an alternating magnetic field will be generated in the metal conductor, which is called the primary magnetic field. , at the same time, the alternating magnetic field induces an eddy current on the surface of the metal conductor; the eddy current in the metal conductor will also generate a magnetic field, which is called a secondary magnetic field; if there are defects such as cracks on the surface of the metal conductor, it will cause changes in the eddy current, which A change is then induced in the detection coil by the secondary magnetic field, and finally characterized as a change in coil impedance, from which the existence and severity of defects on the surface of the metal conductor can be judged. Eddy current testing has the advantages of non-contact, fast speed, and high sensitivity to surface defects. The single detection coil eddy current probe has a small coverage area, and it is time-consuming and labor-intensive to perform point-by-point scanning and detection of larger-area specimens, and sometimes missed detection may occur. The array eddy current probe is composed of multiple independent detection coils. Compared with the single detection coil probe, the array eddy current probe has the following advantages: the probe covers a large area and the detection efficiency is high; It is necessary to design and manufacture complex mechanical scanning devices. However, there is electromagnetic coupling between adjacent detection coils, and the resulting change in the impedance of the detection coil will be superimposed on the impedance change caused by the defect, resulting in deviations in the detection results. In order to solve this problem, the method of setting an electromagnetic shield outside the detection coil is currently used. However, the closed shield structure will hinder the heat exchange of the energized coil in the shield, which will easily cause the coil to overheat and affect the accuracy and service life of the coil; secondly, the introduction of the shield will increase the volume of the probe, resulting in low spatial resolution of the probe . Therefore, it is very necessary to invent an array eddy current probe that can eliminate the electromagnetic coupling effect between detection coils without adding a shield structure.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide an array eddy current probe that can actively release the electromagnetic coupling between adjacent coils. The heat is dissipated in time to avoid overheating; the volume of the probe is reduced, and the spatial resolution is improved.

The technical scheme adopted by the present invention to solve the technical problem is: remove the shielding cover, and arrange two solenoid coils coaxial with the detection coil and respectively located at the two ends of the detection coil as auxiliary coils outside the detection coil; The generated magnetic field weakens the radially distributed external magnetic field generated by the detection coil, thereby reducing the magnetic field interference between adjacent detection coils; a rheostat-type metal slide is set on the auxiliary coil, and a terminal of the metal slide and the auxiliary coil is connected Access to the loading circuit of the auxiliary coil, so that the length and number of turns of the auxiliary coil connected to the loading circuit can be changed by moving the metal slide, and the degree of weakening of the magnetic field of the auxiliary coil to the magnetic field of the detection coil can be adjusted to meet the needs of different application scenarios. Different requirements for the degree of electromagnetic decoupling.

The technical effect of the present invention is reflected in: (a) no shielding cover structure needs to be arranged outside the probe detection coil, which is conducive to the timely diffusion of Joule heat generated when the probe is working, improves the thermal stability of the probe, and reduces the impact of temperature drift on the detection signal At the same time, the volume of the probe is reduced and the spatial resolution of the probe is improved. (b) In different application scenarios, without redesigning and manufacturing the probe, the electromagnetic coupling effect between adjacent detection coils can be decoupled to different degrees by moving the metal slide on the auxiliary coil.

Description of drawings

Fig. 1 is the overall structural diagram of the array probe of the present invention;

Fig. 2 is a sub-probe structural diagram of the present invention;

Fig. 3 is an embodiment of the sub-probe coil current loading of the present invention.

Detailed ways

The overall structure diagram of the array probe designed by the present invention is shown in FIG. 1 . The probe is composed of a plurality of independent sub-probes (10) separated by a certain distance from each other, and each sub-probe has the same structure: a first auxiliary coil (2) and a second auxiliary coil are arranged outside the detection coil (1) (3), they are coaxial with the detection coil (1), and are respectively located at the upper and lower ends of the detection coil (1). The detection coil (1) is a hollow cylindrical coil, the first auxiliary coil (2) and the second auxiliary coil (3) are solenoid coils, and the detection coil (1), the first auxiliary coil (2) and the second auxiliary coil The windings of the three coils (3) are separated. The first auxiliary coil (2) contacts and conducts with the first metal slide (4), and the second auxiliary coil (3) contacts and conducts with the second metal slide (5). Two terminals of the detection coil (1) are connected to a loading circuit (6), and a first auxiliary coil (2) and a second auxiliary coil (3) are respectively connected to a first auxiliary loading circuit (7) and a loading circuit (8). Currents output by the loading circuit (6), the first auxiliary loading circuit (7) and the second auxiliary loading circuit (8) have the same frequency. The first metal slide (4) and the second metal slide (5) are installed on the guide rail (9), and the first metal slide (4) and the second metal slide (5) can be moved on the guide rail (9). The length and the number of turns of the first auxiliary coil (2) and the second auxiliary coil (3) connected to the first auxiliary loading circuit (7) and the second auxiliary loading circuit (8) are respectively changed. When the loading circuit (6) is turned on, the detection coil (1) generates an excitation magnetic field, which on the one hand induces an eddy current in the component under test for detection, and on the other hand its radial component will also affect the adjacent The detection coil produces electromagnetic coupling effect. When the first auxiliary loading circuit (7) and the second auxiliary loading circuit (8) are switched on, the magnetic field produced by the first auxiliary coil (2) and the second auxiliary coil (3) and the excitation magnetic field produced by the detection coil (1) The direction is opposite and decays rapidly in the axial direction. This magnetic field can largely cancel the radial component of the excitation magnetic field generated by the detection coil (1), but has little effect on the axial magnetic field that excites eddy currents in the measured component, thus weakening the electromagnetic coupling between adjacent detection coils , and will not affect the detection ability of the probe.

Fig. 2 is a sub-probe structure diagram of an array eddy current probe realized by the method of the present invention. The sub-probe (10) includes a detection coil (1), a first auxiliary coil (2), a second auxiliary coil (3), a metal slide (4), a metal slide (5), a guide rail (9), and a detection coil skeleton (11), auxiliary coil skeleton (12), shell (13), elastic washer (14), support plate (15), aviation socket (16) and 4-core cable (17). The detection coil (1) is wound on the detection coil skeleton (11), and the first auxiliary coil (2) and the second auxiliary coil (3) are wound on the auxiliary coil skeleton (12). Guide rail (9) is installed on the shell (13), and mark has scale. The first metal slide (4) and the second metal slide (5) are installed on the guide rail (9), and their contacts are connected with the first auxiliary coil (2) and the second auxiliary coil (3) respectively. The two terminals of the detection coil (1) are connected to the 1st and 2nd cores of the 4-core cable (17) through the aviation socket (16); the upper terminal of the first auxiliary coil (2) is connected to the 4-core cable (17) The third core is connected; the lower terminal of the second auxiliary coil (3) is connected with the fourth core of the 4-core cable (17). The first and second cores of the 4-core cable (17) are connected to the loading circuit (6), and the first metal slide (4) and the third core of the 4-core cable (17) are connected to the loading circuit (7). The 4th core of the two metal slides (5) and the 4-core cable (17) is connected to the loading circuit (8). Move the first metal slide (4) and the metal slide (5) according to the scale on the guide rail (9), respectively control the second auxiliary coil (3) and the second auxiliary coil (3) to access the first auxiliary load The length of the circuit (7) and the second auxiliary loading circuit (8). The sub-probe (10) is installed on the support plate (15) of the array probe in the form of suspension through the elastic washer (14) and the aviation socket (16).

The arrangement of the auxiliary coils is not limited to the above-mentioned symmetrical arrangement of a group of coils, including but not limited to a single coil, symmetrical arrangement of multiple sets of coils, etc., as long as the radial component of the exciting magnetic field generated by the detection coil can be canceled out.

Fig. 3 shows the current loading implementation of the sub-probe coil of the present invention. If the detection coil (1), the first auxiliary coil (2) and the second auxiliary coil (3) have the same rotation direction, then the first auxiliary coil (2) and the second auxiliary coil (3) are loaded with the same phase The current of the detection coil (1) is loaded with the current of the opposite phase with the first two; if the first auxiliary coil (2) and the second auxiliary coil (3) have the same rotation direction, and the detection coil (1) If the direction of rotation is opposite, the three coils are loaded with the same phase current; if the direction of rotation of the detection coil (1) and the first auxiliary coil (2) is the same, and the direction of rotation of the second auxiliary coil (3) is opposite, the detection coil (1) and the second auxiliary coil (3) are loaded with the current of the same phase, and the first auxiliary coil (2) is loaded with the current of the opposite phase with the former two; if the detection coil (1) and the second auxiliary coil (3) The direction of rotation is the same as that of the first auxiliary coil (2), and the detection coil (1) and the first auxiliary coil (2) are loaded with the same phase current, while the second auxiliary coil (3) is loaded with the same phase current as the first auxiliary coil (2). The two currents are in opposite phases.

Claims (5)

1. An array eddy current probe for actively relieving electromagnetic coupling between adjacent coils is characterized in that: a first auxiliary coil (2) and a second auxiliary coil (3) are arranged on the periphery of each detection coil (1) of the array probe, and the external magnetic field of an excitation magnetic field generated by the detection coils (1) is weakened by adjusting the length and the number of turns of the first auxiliary coil (2) and the second auxiliary coil (3), so that the mutual interference of magnetic fields generated by adjacent detection coils of the array probe is reduced;

if the rotation directions of the three coils of the detection coil (1), the first auxiliary coil (2) and the second auxiliary coil (3) are the same, the same-phase current is loaded in the first auxiliary coil (2) and the second auxiliary coil (3), and the current opposite to the first two currents is loaded in the detection coil (1); if the rotation directions of the first auxiliary coil (2) and the second auxiliary coil (3) are the same and opposite to the rotation direction of the detection coil (1), the three coils are loaded with currents with the same phase; if the rotation directions of the detection coil (1) and the first auxiliary coil (2) are the same and opposite to the rotation direction of the second auxiliary coil (3), the detection coil (1) and the second auxiliary coil (3) load the same-phase current, and the first auxiliary coil (2) loads the current opposite to the first auxiliary coil and the second auxiliary coil; if the rotation directions of the detection coil (1) and the second auxiliary coil (3) are the same and opposite to the rotation direction of the first auxiliary coil (2), the detection coil (1) and the first auxiliary coil (2) load the same-phase current, and the second auxiliary coil (3) loads the opposite-phase current.

2. An array eddy current probe for actively decoupling electromagnetic coupling between adjacent coils as recited in claim 1, wherein: the detection coil (1) is a hollow cylindrical coil; the first auxiliary coil (2) and the second auxiliary coil (3) are solenoid coils which are coaxial with the detection coil (1) and are respectively positioned at the upper end and the lower end of the detection coil (1).

3. An array eddy current probe for actively decoupling electromagnetic coupling between adjacent coils as recited in claim 1, wherein: the windings of the detection coil (1), the first auxiliary coil (2) and the second auxiliary coil (3) are separated.

4. An array eddy current probe for actively decoupling electromagnetic coupling between adjacent coils as recited in claim 1, wherein: the two terminals of the detection coil (1) are connected with the loading circuit (6), the first auxiliary coil (2) is in contact with and is conducted with the first metal sliding sheet (4), the second auxiliary coil (3) is in contact with and is conducted with the second metal sliding sheet (5), the first auxiliary coil (2) and the second auxiliary coil (3) are respectively connected with the first auxiliary loading circuit (7) and the second auxiliary loading circuit (8), and currents output by the loading circuit (6), the first auxiliary loading circuit (7) and the second auxiliary loading circuit (8) have the same frequency.

5. An array eddy current probe for actively decoupling electromagnetic coupling between adjacent coils as recited in claim 4, wherein: the first metal sliding sheet (4) and the second metal sliding sheet (5) are arranged on the guide rail (9), and the length and the number of turns of the first auxiliary loading circuit (7) and the second auxiliary loading circuit (8) which are respectively connected with the first auxiliary coil (2) and the second auxiliary coil (3) can be respectively changed by moving the first metal sliding sheet (4) and the second metal sliding sheet (5) on the guide rail (9).

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