阅读说明：本技术 涡流探伤装置及涡流探伤方法 (Eddy current flaw detection device and eddy current flaw detection method ) 是由 小林德康 千星淳 秋元惠 鹈饲胜 于 2019-08-06 设计创作，主要内容包括：有关实施方式的涡流探伤装置具有：第一励磁检测器(20),被供给交流电流,通过对被检查体(11)赋予磁场的变化,能够在被检查体(11)诱发涡流；第二励磁检测器(21),夹着被检查体(11)配置在与第一励磁检测器(20)的相反侧,能够检测通过在被检查体(11)诱发的涡流而产生的反作用磁场的变化。(An eddy current flaw detector according to an embodiment includes: a first excitation detector (20) to which an alternating current is supplied and which is capable of inducing an eddy current in the subject (11) by applying a change in a magnetic field to the subject (11); and a second excitation detector (21) which is disposed on the opposite side of the subject (11) from the first excitation detector (20) and which is capable of detecting a change in the reaction magnetic field generated by eddy currents induced in the subject (11).)

1. An eddy current flaw detection device, comprising:

a first excitation detector capable of inducing an eddy current in a subject; and

and a second excitation detector disposed on the opposite side of the subject to be inspected from the first excitation detector with the subject interposed therebetween, and capable of detecting a change in a reaction magnetic field generated by the eddy current.

2. The eddy current testing apparatus according to claim 1,

the first excitation detector and the second excitation detector each have a coil in which a wire is wound in a spiral shape,

the wire of the coil of the first excitation detector is thicker than the wire of the coil of the second excitation detector.

3. The eddy current testing apparatus according to claim 1,

the second excitation detector is configured to induce an eddy current in the subject.

4. The eddy current testing apparatus according to claim 3,

the first excitation detector is configured to be able to detect a change in a reaction magnetic field generated by the eddy current.

5. The eddy current inspection apparatus according to claim 3 or 4,

the eddy current flaw detector includes an alternating current power supply for supplying alternating current to the first excitation detector and the second excitation detector,

the frequency of the alternating current supplied to the first excitation detector and the frequency of the alternating current supplied to the second excitation detector are the same and are synchronized with each other.

6. The eddy current inspection apparatus according to any one of claims 1 to 5,

the eddy current flaw detection device further includes a ferromagnetic shield arranged to cover at least a part of the portions of the surroundings of the first excitation detector and the second excitation detector that do not face the object.

7. An eddy current flaw detection device, comprising:

an excitation detector capable of inducing an eddy current in a subject and detecting a change in a reaction magnetic field generated by the eddy current; and

and a back member of the ferromagnetic body disposed on the opposite side of the excitation detector with respect to the device under test.

8. The eddy current testing apparatus according to claim 7,

the excitation detector has a separate exciter capable of inducing eddy currents in the object and a detector capable of detecting a change in a reaction magnetic field generated by the eddy currents.

9. An eddy current testing method, comprising:

a first excitation detector disposing step of disposing a first excitation detector in proximity to the subject;

a second excitation detector arrangement step of arranging a second excitation detector close to the subject on a side opposite to the first excitation detector with the subject interposed therebetween;

an excitation step of inducing an eddy current in the subject by the first excitation detector after the first excitation detector arranging step and the second excitation detector arranging step; and

a detecting step of detecting, by the second excitation detector, a change in a reaction magnetic field generated by the eddy current.

10. An eddy current testing method, comprising:

an excitation detector placement step of placing an excitation detector in proximity to a subject;

a back member disposing step of disposing a back member of a ferromagnetic body near the object to be inspected on a side opposite to the excitation detector with the object to be inspected interposed therebetween;

an excitation step of inducing an eddy current in the subject by the excitation detector after the excitation detector arrangement step and the back surface member arrangement step; and

a detection step of detecting, by the excitation detector, a change in a reaction magnetic field generated by the eddy current.

Technical Field

The embodiment of the invention relates to an eddy current testing device and an eddy current testing method.

Background

In general, eddy current flaw detection is performed by using a metal material as an object to be inspected, supplying an alternating current from an alternating current power supply to an excitation coil, inducing an eddy current in the vicinity of the surface of the object, and detecting a reaction magnetic field generated by the eddy current by a detection coil. If a defect exists near the surface of the object, the flow of eddy current changes due to the defect, and the intensity and distribution of the reaction magnetic field generated by the eddy current also change, so that the presence or absence of the defect can be detected.

On the other hand, a composite material composed of two or more different materials may have a lower electrical conductivity than a metal material due to a laminated structure or the use of fibers or the like. When such a composite material is used as an inspection target for eddy current testing, the electrical conductivity of the composite material is low, and thus the eddy current density induced by the composite material is reduced. Therefore, the magnetic flux density of the reaction magnetic field generated by the eddy current is also reduced, and the sensitivity of defect detection is reduced.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 9-33489

Disclosure of Invention

Problems to be solved by the invention

In order to improve the defect detection sensitivity of eddy current flaw detection under a micro magnetic field condition, a technique using a SQUID (Superconducting Quantum Interference Device) fluxmeter is known. In this technique, the SQUID fluxmeter has high sensitivity to a magnetic field, and therefore, it is expected that the defect detection sensitivity of eddy current flaw detection under a low magnetic field condition is improved. However, the SQUID fluxmeter requires cooling, and there are problems such as the device structure becoming complicated and the device price becoming high.

The electrical conductivity of the composite material is sometimes lower than that of the metal material, and if the composite material is subjected to eddy current flaw detection, the eddy current density flowing through the composite material and the magnetic flux density generated by the eddy current are reduced, so that the flaw detection sensitivity of eddy current flaw detection is reduced. Further, if a highly sensitive magnetic sensor is used as the detection unit of eddy current testing, the apparatus configuration may be complicated and the apparatus may be expensive.

An object of an embodiment of the present invention is to realize eddy current testing that can detect defects with high sensitivity using a simple and inexpensive apparatus configuration even for an inspection target of a material having low conductivity, such as a composite material.

Means for solving the problems

In order to solve the above problem, according to one embodiment of the present invention, an eddy current flaw detection apparatus includes: a first excitation detector capable of inducing an eddy current in a subject; and a second excitation detector disposed on the opposite side of the subject to be inspected from the first excitation detector with the subject to be inspected interposed therebetween, and capable of detecting a change in a reaction magnetic field generated by the eddy current.

In addition, according to another embodiment of the present invention, an eddy current flaw detection apparatus includes: an excitation detector capable of inducing an eddy current in a subject and detecting a change in a reaction magnetic field generated by the eddy current; and a back member of a ferromagnetic body disposed on the opposite side of the excitation detector with the subject interposed therebetween.

In addition, according to another embodiment of the present invention, an eddy current testing method includes:

a first excitation detector disposing step of disposing a first excitation detector in proximity to the subject; a second excitation detector arrangement step of arranging a second excitation detector close to the subject on a side opposite to the first excitation detector with the subject interposed therebetween; an excitation step of inducing an eddy current in the subject by the first excitation detector after the first excitation detector arranging step and the second excitation detector arranging step; and a detection step of detecting, by the second excitation detector, a change in a reaction magnetic field generated by the eddy current.

In addition, according to another embodiment of the present invention, an eddy current testing method includes: an excitation detector placement step of placing an excitation detector in proximity to a subject; a back member disposing step of disposing a back member of a ferromagnetic body near the object to be inspected on a side opposite to the excitation detector with the object to be inspected interposed therebetween; an excitation step of inducing an eddy current in the subject by the excitation detector after the excitation detector arrangement step and the back surface member arrangement step; and a detection step of detecting, by the excitation detector, a change in a reaction magnetic field generated by the eddy current.

Effects of the invention

According to the embodiments of the present invention, eddy current testing capable of detecting defects with high sensitivity can be realized even for an inspection target of a material having low conductivity, such as a composite material, with a simple and inexpensive apparatus configuration.

Drawings

Fig. 1 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a first embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing a state during flaw detection by the eddy-current flaw detection apparatus according to the second embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a third embodiment of the present invention.

Fig. 4 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a fourth embodiment of the present invention.

Fig. 5 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a fifth embodiment of the present invention.

Fig. 6 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a sixth embodiment of the present invention.

Fig. 7 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a seventh embodiment of the present invention.

Detailed Description

Hereinafter, an eddy current testing apparatus and an eddy current testing method according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar portions are denoted by the same reference numerals, and overlapping description is omitted.

[ first embodiment ]

Fig. 1 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a first embodiment of the present invention.

In the first embodiment, the object 11 to be inspected is made of a composite material having a lower electrical conductivity than a normal metal material. The composite material can be a composite material using silicon carbide fiber, Carbon Fiber Reinforced Plastic (CFRP), Glass Fiber Reinforced Plastic (GFRP), or the like, for example. The object 11 is, for example, a flat plate-like body, and has a first plane 12 and a second plane 13 parallel to the first plane 12 on the back surface side thereof. It is assumed that a defective portion (thin-walled portion) 14 exists in the first plane 12.

The eddy current testing apparatus according to the first embodiment includes an exciter 20 as a first excitation detector and a detector 21 as a second excitation detector. The exciter 20 and the detector 21 are, for example, helical coils. The exciter 20 is disposed in contact with the first plane 12 of the subject 11, and the detector 21 is disposed in contact with the second plane 13 of the subject 11. The exciter 20 and the detector 21 are disposed such that the axes a of their coils face the first plane 12 and the second plane 13 perpendicularly. The ac power source 22 is connected to the exciter 20. The detector 21 is connected to a detector circuit not shown.

The coil wire constituting the exciter 20 is made thicker than the coil wire constituting the detector 21. This is to suppress joule loss in the exciter 20 because a relatively large current needs to flow in the exciter 20.

If an ac current is supplied to the exciter 20 by the ac power supply 22, a varying magnetic field is formed around the exciter 20. The magnetic induction line M at this time is indicated by a broken line in fig. 1. The magnetic field formed by the exciter 20 is substantially symmetrical about the axis a of the exciter 20, but only the magnetic induction line M to the right of the axis a is shown in fig. 1.

By forming a varying magnetic field around the exciter 20, an eddy current is induced in the object 11. A reaction magnetic field is formed by the eddy current. The reaction magnetic field is detected as a voltage by the detector 21 and the detector circuit. Since the reaction magnetic field changes due to the presence of the defective portion 14, the detector circuit can detect the defective portion 14 as a change in voltage.

When the subject 11 is a normal metal material, almost all the magnetic induction lines pass through the inside of the subject 11 due to the skin effect, and almost no magnetic field exists on the back surface (second plane 13) of the subject 11. For example, when the object 11 is stainless steel having a thickness of 2mm and the frequency of the supplied alternating current is 500kHz, the penetration depth of the magnetic field due to the skin effect is about 0.7 mm.

On the other hand, when the test object 11 is a composite material having low conductivity, the penetration depth of the magnetic field due to the skin effect is deeper than when the test object 11 is a normal metal material, and the magnetic field penetrates through the test object 11 as shown in fig. 1 and also exists on the back surface (second plane 13) of the test object 11. However, in this case, the magnetic flux density generated in the device 11 is lower than in the case where the device 11 is made of a normal metal material.

In this embodiment, the exciter 20 and the detector 21 are provided as separate bodies, and the exciter 20 and the detector 21 are disposed so as to sandwich the subject 11. Thereby, both the exciter 20 and the detector 21 can be disposed close to the subject 11. That is, the detector 21 can be disposed at a position where the magnetic flux density is relatively high, and flaw detection can be performed with relatively high accuracy.

Further, the exciter 20 and the detector 21 do not need to have the same structure and specification, and can be designed to be suitable for the wire diameter, the number of turns, the shape, the size, and the like of the respective coils. However, since a relatively large current needs to flow through the coil of the exciter 20, it is desirable to increase the wire diameter of the coil. On the other hand, the coil of the detector 21 is required to be detected as a large voltage although a large current does not need to flow, and therefore, it is desirable to make the wire diameter of the coil relatively small and increase the number of turns.

When the test object 11 is a low-conductivity material such as a composite material, the penetration depth of the magnetic induction lines can be reduced by setting the frequency of the power supply high, and high-sensitivity flaw detection can be performed. Therefore, it is desirable to set the frequency of the power supply to the MHz level.

[ second embodiment ]

Fig. 2 is a schematic cross-sectional view showing a state during flaw detection by the eddy-current flaw detection apparatus according to the second embodiment of the present invention.

The eddy current flaw detector of the second embodiment includes a first excitation detector 25 and a second excitation detector 26.

First excitation detector 25 and second excitation detector 26 are, for example, helical coils. The first excitation detector 25 is disposed in contact with the first plane 12 of the test object 11, and the second excitation detector 26 is disposed in contact with the second plane 13 of the test object 11. First excitation detector 25 and second excitation detector 26 are disposed such that axes a of their coils face first plane 12 and second plane 13 perpendicularly. First excitation detector 25 is connected to ac power supply 22, and second excitation detector 26 is connected to ac power supply 22 a. First excitation detector 25 and second excitation detector 26 are connected to detector circuits, not shown, respectively.

The first excitation detector 25 and the second excitation detector 26 have substantially the same structure, and have both the exciter function and the detector function. The ac power sources 22, 22a may be of the same construction as each other, preferably both in frequency and phase with each other and in synchronism. The ac power supplies 22 and 22a may be one ac power supply instead of being provided as separate units.

According to the second embodiment, since the excitation actions of the first excitation detector 25 and the second excitation detector 26 overlap each other, a higher magnetic flux density is obtained and the eddy current induced in the object 11 is intensified. Thereby, the change of the reaction magnetic field due to the eddy current increases. Therefore, the first excitation detector 25 and the second excitation detector 26 as detectors can detect a change in voltage as a relatively large change. Further, by adding the voltages obtained by first excitation detector 25 and second excitation detector 26 as detectors, it is possible to detect a larger change in voltage.

In the above description, it is preferable that the ac currents supplied to first excitation detector 25 and second excitation detector 26 have the same frequency and phase and are synchronized with each other. However, even when such a condition is not satisfied, since there is a condition that the magnetic fields generated by the first excitation detector 25 and the second excitation detector 26 are mutually intensified, flaw detection can be performed under such a condition that the magnetic fields are mutually intensified.

In the above description, both the first excitation detector 25 and the second excitation detector 26 are caused to function as detectors, and the voltage signals detected by these detectors are added, but depending on the relationship of the phases of the alternating currents supplied to the first excitation detector 25 and the second excitation detector 26, the voltage signals detected by the first excitation detector 25 and the second excitation detector 26 may be subtracted to perform flaw detection.

Further, it is also possible to cause only one of the first excitation detector 25 and the second excitation detector 26 to function as a detector, and to perform flaw detection based on a voltage signal detected by the detector.

[ third embodiment ]

Fig. 3 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a third embodiment of the present invention.

The third embodiment is a modification of the second embodiment, and covers the parts of the outsides of the first excitation detector 25 and the second excitation detector 26 that do not face the object 11 with a shield 30 of a ferromagnetic material. The other structure is the same as that of the second embodiment.

According to the third embodiment, the operation and effect of the second embodiment can be obtained, and the magnetic field generated by supplying the alternating current to the first excitation detector 25 and the second excitation detector 26 forms a distribution along the magnetic path generated by the shield 30 of the ferromagnetic body, thereby increasing the magnetic flux density. This increases the magnetic flux density passing through the defect 14 and interlinking with the first excitation detector 25 or the second excitation detector 26, thereby realizing highly sensitive defect detection.

In the example shown in fig. 3, the entire portion of the outer sides of the first excitation detector 25 and the second excitation detector 26 that does not face the subject 11 is covered with a shield 30 made of a ferromagnetic material. As a modification of this example, the shield 30 may cover only a part of the portions of the outsides of the first excitation detector 25 and the second excitation detector 26 that do not face the subject 11. In this case, the effect of the ferromagnetic shield 30 can be partially obtained.

In the above description, the third embodiment is a modification of the second embodiment, and covers the parts of the outer sides of the first excitation detector 25 and the second excitation detector 26 of the eddy current flaw detector according to the second embodiment that do not face the test object 11 with the shield 30 of a ferromagnetic material. As a modification of the third embodiment, a shield 30 of a ferromagnetic material may cover a portion of the outside of the exciter 20 and the detector 21 of the eddy current flaw detector according to the first embodiment, which portion does not face the test object 11. In this case, the effect of increasing the magnetic flux density in the device under test 11 by the shield 30 of the ferromagnetic material can also be obtained.

[ fourth embodiment ]

Fig. 4 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a fourth embodiment of the present invention.

The eddy current flaw detector according to the fourth embodiment includes an excitation detector 35 and a ferromagnetic back surface member 36. The excitation detector 35 is the same as the first excitation detector 25 of the second embodiment, and is disposed in contact with the first plane 12 of the test object 11. Excitation detector 35 is connected to ac power supply 22 and also to a detector circuit, not shown. The back member 36 of the ferromagnetic body is disposed so as to contact the second flat surface 13 at a position opposite to the excitation detector 35 with the subject 11 therebetween. The back member 36 is preferably arranged to cover the entire part on the opposite side of the excitation detector 35 with the subject 11 interposed therebetween. The excitation detector 35 has both a function as an exciter and a function as a detector.

According to the fourth embodiment, an alternating current is supplied from the alternating current power supply 22 to the excitation detector 35, and a varying magnetic field is formed in and around the subject 11. Thereby, an eddy current is induced in the test object 11, and a reaction magnetic field is formed. The reaction magnetic field can be detected as a voltage signal by the excitation detector 35 as a detector. In this case, the presence of the back surface member 36 of the ferromagnetic material can increase the magnetic flux density in the object 11, thereby improving the detection sensitivity of the defective portion 14.

[ fifth embodiment ]

Fig. 5 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a fifth embodiment of the present invention.

The fifth embodiment is a modification of the fourth embodiment, and the excitation detector 35 of the fourth embodiment is replaced with an exciter 20 and a detector 21. The structures of the exciter 20 and the detector 21 are the same as those of the exciter 20 and the detector 21 of the first embodiment. However, in the fifth embodiment, the exciter 20 is disposed in contact with the first plane 12 of the subject 11, and the detector 21 is disposed on the opposite side of the subject 11 with respect to the exciter 20. The other structure is the same as that of the fourth embodiment.

According to the fifth embodiment, as in the fourth embodiment, the presence of the back surface member 36 of a ferromagnetic material can increase the magnetic flux density in the object 11, thereby increasing the detection sensitivity of the defective portion 14. Further, since the exciter 20 and the detector 21 are separate bodies as in the first embodiment, it is not necessary to make the structures and specifications of the exciter 20 and the detector 21 the same, and design suitable for the wire diameter, the number of turns, the shape, the size, and the like of the respective coils can be made.

[ sixth embodiment ]

Fig. 6 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a sixth embodiment of the present invention.

The sixth embodiment is a modification of the fifth embodiment, and a ferromagnetic shield 40 is disposed so as to cover the outside of the exciter 20 and the detector 21 which are configured and disposed similarly to the fifth embodiment.

According to the sixth embodiment, in addition to the effect of the fifth embodiment, the presence of the ferromagnetic shield 40 can further increase the magnetic flux density in the object 11, thereby further improving the detection sensitivity of the defective portion 14.

[ seventh embodiment ]

Fig. 7 is a schematic cross-sectional view showing a state during flaw detection by an eddy-current flaw detection apparatus according to a seventh embodiment of the present invention.

In the seventh embodiment, which is a modification of the fifth embodiment, the exciter 20 and the detector 21 are arranged in parallel in contact with the first plane 12 of the test object 11. The back member 36 of the ferromagnetic body is disposed so as to contact the second flat surface 13 at a position opposite to the exciter 20 and the detector 21 with the subject 11 therebetween. The back member 36 is preferably arranged to cover the entire part of the device under test 11 on the side opposite to the exciter 20 and the detector 21. The other structure is the same as that of the fifth embodiment.

According to the seventh embodiment, as in the fifth embodiment, the presence of the back surface member 36 of a ferromagnetic material can increase the magnetic flux density in the object 11, thereby increasing the detection sensitivity of the defective portion 14. Since the exciter 20 and the detector 21 are separate bodies, the exciter 20 and the detector 21 do not need to have the same structure and the same specification, and can be designed to be suitable for the wire diameter, the number of turns, the shape, the size, and the like of the respective coils.

[ other embodiments ]

It is also possible to combine the features of the above embodiments with each other. For example, the cover 40 of the sixth embodiment may be added to the fourth or seventh embodiment.

While the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments may be implemented in various other forms, and various omissions, substitutions, and changes may be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

Description of the reference symbols

11 … testing object; 12 … a first plane; 13 … second plane; 14 … defective portion (thin-walled portion); 20 exciter (first excitation detector); 21 … detector (second excitation detector); 22. 22a … a.c. power supply; 25 … a first excitation detector; 26 … second excitation detector; 30 … a shield; 35 … excitation detector; 36 … back side member; 40 … shield.