Multi-coil staggered arrangement eddy current probe for metal strip flaw detection

Abstract

The utility model provides a kind of metal strip flaw detection with multi-coil misplacement arrangement eddy current probe, it is related to metal strip flaw detection technical field.The utility model's eddy current probe includes shell and three rows of coils being set in shell, the coil in middle row is excitation coil, the coil in upper row and lower row is detection coil;Excitation coil is equidistantly set along the width direction of metal strip, and detection coil is misplacement set relative to excitation coil;Detection coil is composed of ring core and multiple coil windings being wound on ring core, wherein, coil winding is vertically set with excitation coil.The utility model's eddy current probe solves the problem of eddy current distortion and signal mutual interference by the mode of turn by turn loading excitation signal, and can more truly reflect the shape, size and specific location of defect, significantly improve the use effect of eddy current flaw detection, and effectively avoid the occurrence of misjudgment.

Description

Technical Field

[0001] This utility model is specifically a multi-coil staggered eddy current probe for flaw detection of metal strips, which relates to the field of flaw detection technology for metal strips. Background Technology

[0002] Eddy current testing is a technique that uses the principle of electric eddy currents to detect metal defects. Its core components are the excitation coil and the detection coil inside the eddy current probe.

[0003] See attached document Figure 1 The existing eddy current probe has an excitation coil 2 and a detection coil 3 coaxially arranged inside. The excitation coil 2 induces eddy currents in the metal being tested, and the detection coil 3 senses the electrical signal based on the changes in the eddy currents, thereby detecting whether there are defects in the metal being tested. The eddy current region 4 induced by the excitation coil 2 is relatively small. To meet the testing requirements of metal strips, many eddy current probes need to be arranged along the width of the metal strip. For the specific structure, please refer to the patent application number CN202310497149.4. This method of arranging multiple eddy current probes for flaw detection has the following main disadvantages: 1. Eddy current probes require a large number of setups and are costly, and each eddy current probe requires a corresponding control circuit and device; 2. If the spacing between the eddy current probes is too large, a detection blind zone will occur; if the spacing between the eddy current probes is too small, eddy current distortion and signal interference will occur. 3. The detection coil can detect the presence of defects in the metal strip, but it cannot detect the size, shape, or specific location of the defects. Utility Model Content

[0004] To overcome the shortcomings of the prior art, this utility model discloses a multi-coil staggered eddy current probe for flaw detection of metal strips, adopting the following technical solution: A multi-coil staggered eddy current probe for flaw detection of metal strip includes a housing and three rows of coils disposed within the housing. The coils in the middle row are excitation coils, and the coils in the upper and lower rows are detection coils. The excitation coils are equidistantly arranged along the width direction of the metal strip, and the detection coils are staggered relative to the excitation coils. The detection coil consists of a ring core and multiple coil windings wound on the ring core, wherein the coil windings are arranged perpendicular to the excitation coils. During operation, each excitation coil alternately applies an excitation signal at a time with an interval of one excitation coil.

[0005] Further improve the technical solution: the detection coil is equidistant from the two adjacent excitation coils.

[0006] Further improve the technical solution: Let the spacing between the excitation coils be 2a, and the radius of the eddy current induced by the excitation coils be r, then r > a.

[0007] Further improve the technical solution: Let the distance between two opposing detection coils be 2b, and the detection radius of the detection coil be R, then we have .

[0008] Further improve the technical solution: Let the number of excitation coils be N, N≥2, then the number of detection coils is 2N-2.

[0009] Further improve the technical solution: the excitation coil and the core are circular rings, and the coil winding is circular ring or square frame.

[0010] After implementing the above technical solution, compared with the prior art, the present invention can produce the following beneficial effects: 1. This utility model only requires one row of excitation coils, two rows of detection coils and a set of control circuits to achieve non-destructive testing of metal strips, which greatly reduces production costs.

[0011] 2. This utility model solves the problems of eddy current distortion and signal interference by alternately loading excitation signals, which significantly improves the application effect of eddy current flaw detection.

[0012] 3. This utility model can reflect the shape, size and specific location of defects more realistically, and can effectively avoid misjudgment. Attached Figure Description

[0013] Appendix Figure 1 The diagram shown is a structural schematic of an existing eddy current probe.

[0014] Appendix Figure 2 The diagram shown is a structural schematic of this eddy current probe.

[0015] Appendix Figure 3 The diagram shows the arrangement of the excitation coil and the detection coil.

[0016] Appendix Figure 4 The diagram shows the arrangement of the excitation coil and the detection coil when r < a.

[0017] Appendix Figure 5 The diagram shows the arrangement of the excitation coil and the detection coil when r > a.

[0018] Appendix Figure 6-7 The diagram shows the excitation coils being loaded with excitation signals in turn.

[0019] Appendix Figure 8 The flowchart shown is for eddy current testing.

[0020] Appendix Figure 9 The diagram shown is a schematic diagram of the flaw detection principle for coil windings.

[0021] Appendix Figure 10 The diagram shown is a flaw detection schematic of a single row of detection coils.

[0022] Appendix Figure 11 The diagram shown is a flaw detection schematic of a double-row detection coil.

[0023] In the attached diagram: 1. Housing; 2. Excitation coil; 3. Detection coil; 3.1. Ring core; 3.2. Coil winding; 4. Eddy current region; 5. Detection region; 6. Metal strip; 7. Crack. Detailed Implementation

[0024] The preferred embodiments of this utility model are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of this utility model and are not intended to limit the scope of protection of this utility model. It should be noted that in the description of this utility model, terms such as "front," "rear," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is merely for ease of description and does not indicate or imply that the device or element must have a specific orientation and positional relationship, and therefore should not be construed as a limitation of this utility model. It should also be noted that in the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0025] A multi-coil staggered eddy current probe for flaw detection of metal strips is disclosed, relating to the field of metal strip flaw detection technology. The composition and working principle of this invention are described in detail below.

[0026] See attached document Figure 2The eddy current probe of this invention mainly consists of a housing 1 and three rows of coils disposed within the housing 1. The coils in the middle row are excitation coils 2, and the coils in the upper and lower rows are detection coils 3. The excitation coils 2 are equidistantly arranged along the width direction of the metal strip 6. The detection coils 3 are offset relative to the excitation coils 2, and the distance between the detection coils 3 and any adjacent excitation coils 2 is equal. The detection coil 3 consists of a ring core 3.1 and multiple coil windings 3.2 wound on the ring core 3.1. The ring core 3.1 is parallel to the winding plane of the excitation coil 2, and the winding plane of the coil windings 3.2 is perpendicular to the winding plane of the excitation coil 2. During operation, the metal strip 6 moves close to the eddy current probe at a uniform speed, the winding plane of the excitation coil 2 is parallel to the metal strip 6, and the winding plane of the coil windings 3.2 is perpendicular to the metal strip 6. Since the eddy current induced by the excitation coil 2 rotates along the plane of the metal strip 6, the eddy current can pass perpendicularly through the plane where the coil winding 3.2 is located and generate an alternating magnetic field, thereby causing the coil winding 3.2 to generate a detection signal.

[0027] See attached document Figure 3 The function of excitation coil 2 is to induce eddy currents within the metal strip 6, and the function of detection coil 3 is to detect electrical signals based on changes in the eddy currents, thereby detecting whether defects exist within the metal strip 6. In this embodiment, excitation coil 2 and the ring core 3.1 are circular rings; the coil winding can be either circular or rectangular. Let the distance between the excitation coils 2 be 2a, and the radius of the eddy current region 4 induced by the excitation coil 2 be r, then r > a. Let the distance between the two opposing detection coils 3 be 2b, and the radius of the detection region 5 of the detection coil 3 be R, then... If the number of excitation coils 2 is N, where N≥2, then the number of detection coils 3 is 2N-2.

[0028] See attached document Figure 4 When r < a, after the excitation signal is applied, the induced eddy current regions 4 of the two adjacent excitation coils 2 will generate a blind zone because they do not overlap. In this blind zone, eddy currents will not be generated. At this time, even if the detection region 5 of the detection coil 3 covers the blind zone, it will not be able to detect whether there is a defect in the blind zone.

[0029] See attached document Figure 5 When r > a, the eddy current regions 4 induced by the two adjacent excitation coils 2 will overlap after the excitation signal is applied. The overlap will cause two difficult problems: first, the detection coil 3 will detect the eddy currents induced by the two excitation coils 2 at the same time, resulting in mutual signal interference; second, eddy current distortion will occur in the overlapping area, which will seriously affect the detection effect.

[0030] See attached document Figure 6 and attached Figure 7To solve the above problems, during operation, each excitation coil is alternately loaded with an excitation signal at a time with one excitation coil between them.

[0031] From the appendix Figure 6 As can be seen, taking four excitation coils as an example, when 1 # Excitation coil and 3 # When the excitation coil is loaded with an excitation signal and eddy current region 4 is induced, 2 # Excitation coil and 4 # The excitation coil is not loaded with an excitation signal, and no eddy current region 4 is induced. At this time, 1 # Excitation coil and 3 # The eddy current region 4 generated by the excitation coil will not overlap, and will not overlap with 1. # The two adjacent detection coils 3 of the excitation coil can only detect 1. # The eddy current induced in the excitation coil, and 2 # The four adjacent detection coils 3 of the excitation coil can only detect 2. # The eddy currents induced in the excitation coil will not cause signal interference.

[0032] From the appendix Figure 7 It can be seen that when 2 # Excitation coil and 4 # When the excitation coil is loaded with an excitation signal and eddy current region 4 is induced, 1 # Excitation coil and 3 # The excitation coil is not loaded with an excitation signal, and no eddy current region 4 is induced. At this time, 2 # Excitation coil and 4 # The eddy current region 4 generated by the excitation coil will not overlap, and will not overlap with 2. # The four adjacent detection coils 3 of the excitation coil can only detect 1. # The eddy current induced in the excitation coil, and 4 # The two adjacent detection coils 3 of the excitation coil can only detect 2. # The eddy currents induced in the excitation coil will not cause signal interference. Then, 1 # Excitation coil and 3 # The excitation coil is then reloaded with an excitation signal, and so on.

[0033] See attached document Figure 8To enable flaw detection of metal strips, this invention also includes an FPGA programmable logic device, an excitation generation circuit, a multiplexing circuit, and an eddy current differential amplifier circuit. The excitation generation circuit generates a sine wave and is connected to each excitation coil 2, enabling the excitation coil 2 to generate a sine wave excitation signal. The coil windings 3.2 on each detection coil 3 are connected to the eddy current differential amplifier circuit and feed back the detection signal to the FPGA programmable logic device through the multiplexing circuit. The multiplexing circuit is existing technology; its connection to the excitation generation circuit, excitation coil 2, and eddy current differential amplifier circuit enables multiple transmissions and receptions, simplifying the circuit.

[0034] See attached document Figure 9 During operation, the eddy currents induced by the excitation coil 2 rotate along the plane of the metal strip. If the metal strip is free of defects, the eddy currents pass almost perpendicularly through the plane containing the coil winding 3.2 and generate a ring-shaped magnetic field. Since the ring-shaped magnetic field is almost parallel to the plane containing the coil winding 3.2, the coil winding 3.2 rarely participates in cutting the magnetic lines of force, and therefore generates virtually no signal. However, once defects such as cracks 7 appear in the metal strip, the flow direction of the eddy currents changes due to the defects, resulting in abnormal magnetic field distortion. At this time, the coil winding 3.2 generates a significant detection signal.

[0035] See attached document Figure 10 Because the multiple coil windings 3.2 on the ring core 3.1 are directional, the closer the coil winding 3.2 is to the defect, the stronger the detection signal it receives; the farther away the coil winding 3.2 is from the defect, the weaker the detection signal it receives. Thus, by comparing the signal strength of each coil winding 3.2, the specific location of the defect can be determined. If only a single row of detection coils 3 is used, the detection coils 3 can only detect defects in one direction. When a defect appears in the metal strip, as shown in the attached image... Figure 9 When the crack is 7, the shape and size of the defect displayed by the system will be severely distorted, which may lead to misjudgment.

[0036] See attached document Figure 11 After setting up two rows of detection coils 3, the two detection coils 3 can jointly detect the crack 7 from different angles. At this time, the system can reflect the shape and size of the crack 7 more realistically through image synthesis, avoiding misjudgment.

[0037] It is worth noting that the content not described in detail in the above embodiments is prior art. It is also worth noting that any additions, subtractions, substitutions, and improvements made by those skilled in the art based on the structure and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A multi-coil staggered eddy current probe for flaw detection of metal strips, characterized in that: It includes a housing and three rows of coils disposed within the housing. The coils in the middle row are excitation coils, and the coils in the upper and lower rows are detection coils. The excitation coils are equidistantly arranged along the width direction of the metal strip, and the detection coils are staggered relative to the excitation coils. The detection coil consists of a ring core and multiple coil windings wound on the ring core, wherein the coil windings are arranged perpendicular to the excitation coils.

2. The multi-coil staggered eddy current probe for flaw detection of metal strips as described in claim 1, characterized in that: The detection coil is equidistant from the two adjacent excitation coils.

3. The multi-coil staggered eddy current probe for flaw detection of metal strips as described in claim 2, characterized in that: Let the spacing between the excitation coils be 2a, and the radius of the eddy current induced in the excitation coils be r, then r > a.

4. The multi-coil staggered eddy current probe for flaw detection of metal strips as described in claim 3, characterized in that: Let the distance between two opposing detection coils be 2b, and the detection radius of the detection coils be R, then we have .

5. The multi-coil staggered eddy current probe for flaw detection of metal strips as described in claim 1, characterized in that: If the number of excitation coils is N, and N≥2, then the number of detection coils is 2N-2.

6. The multi-coil staggered eddy current probe for flaw detection of metal strips as described in claim 1, characterized in that: The excitation coil and core are circular rings, and the coil windings are either circular rings or square frames.

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