JP7450305B1 - Inspection equipment and inspection method - Google Patents

Abstract

[Problem] An inspection that can accurately inspect for damage to the inspection target even when it is difficult to directly contact the inspection target made of magnetic material, such as piping or tanks whose surfaces are covered with a protective member. Provides equipment and testing methods. An inspection device (1) includes a transmitting unit (11) and a receiving unit (12). The transmitting unit 11 includes a transmitting bias electromagnet that generates a bias magnetic field between both magnetic poles, and an excitation electromagnet that changes the magnetic flux between both magnetic poles and generates a guided wave in the inspection target due to the magnetostrictive effect. The bias electromagnet is arranged so that the direction in which both magnetic poles are connected is orthogonal to the direction in which both magnetic poles of the excitation electromagnet are connected. The receiving unit 12 includes a receiving bias electromagnet that generates a bias magnetic field between both magnetic poles, and a guided wave detection electromagnet that detects an induced current generated by a guided wave, and has a direction that connects both magnetic poles of the receiving bias electromagnet. and the direction connecting both magnetic poles of the guided wave detection electromagnet are arranged so as to be orthogonal to each other. [Selection diagram] Figure 1

Description

The present invention relates to an inspection apparatus and an inspection method, and more particularly to an inspection apparatus and an inspection method for inspecting a magnetic material to be inspected for damage.

BACKGROUND ART Conventionally, methods have been developed for non-destructively inspecting members made of magnetic materials, such as plates and piping, for the presence or absence of damage. For example, an inspection method using ultrasonic guided waves has been developed as a nondestructive inspection method for easily inspecting long sections of piping for damage such as corrosion and cracks. As an inspection method using ultrasonic guided waves, as in Patent Document 1 and Patent Document 2, guided waves are generated using the magnetostrictive effect of piping, which is a magnetic material, and guided waves reflected from damaged parts of the piping are detected. Methods of measuring waves are known.

Japanese Patent Application Publication No. 2008-76296 JP2020-79790A

In the ultrasonic flaw detection device of Patent Document 1, the heat insulating material of the metal pipe is removed, and a guided wave transmitting sensor using Lorentz force as a driving force and a receiving sensor that receives the guided wave are brought into direct contact with the pipe. We are planning to conduct a flaw detection. However, piping in buildings, factories, etc. is often protected with heat insulating material, etc., and when removing the heat insulating material and attaching transmitting sensors and receiving sensors to the pipes, it takes a lot of effort to inspect. In addition, if the protective member of the inspection target such as piping cannot be removed, or if the inspection target is coated, it is not possible to directly contact the transmitting sensor or the receiving sensor with the inspection target, so the inspection target cannot be inspected. It's difficult to do.

Further, in Patent Document 2, even if the piping is covered with a protective member, the piping is inspected by uniformly magnetizing the piping and generating guided waves in the piping. This makes it possible to increase the intensity of the guided wave and detect the reflected wave of the guided wave with high accuracy. However, the guided wave signal strength depends on the strength of the magnetic field due to residual magnetization, and it is thought that the strength of the magnetic field due to residual magnetization is only about 60 to 70% of the saturation magnetic field. Therefore, it may be difficult to increase the guided wave detection accuracy by increasing the residual magnetization.

The present invention was made in view of the above-mentioned circumstances, and is applicable to cases where it is difficult to directly contact the magnetic material to be inspected, such as piping whose surface is covered with a protective member, or a tank with a coating. It is an object of the present invention to provide an inspection device and an inspection method that can accurately inspect damage on an inspection target even when the inspection target is damaged.

In order to achieve the above object, an inspection device according to a first aspect of the present invention includes:
A transmitting unit that generates guided waves on a magnetic object to be inspected;
a receiving unit that receives the guided wave transmitted from the transmitting unit and reflected by the damaged part of the inspection target,
The transmitting unit is
a transmission bias electromagnet that generates a bias magnetic field between two magnetic poles facing the inspection target by applying a direct current to a coil;
Applying an alternating current to the coil to change the magnetic flux between the two magnetic poles facing the test object, and generate the guided wave by the magnetostrictive effect in the region of the test object to which a bias magnetic field is applied by the transmission bias electromagnet. an excitation electromagnet,
arranged so that a direction connecting both magnetic poles of the transmission bias electromagnet and a direction connecting both magnetic poles of the excitation electromagnet are perpendicular to each other,
The receiving unit includes:
a receiving bias electromagnet that generates a bias magnetic field between both magnetic poles facing the inspection target by applying a direct current to a coil;
a guided wave detection electromagnet with both magnetic poles facing the inspection target and detecting an induced current generated by the guided wave passing through a region to which a bias magnetic field is applied by the reception bias electromagnet;
The receiving bias electromagnet is arranged so that the direction in which both magnetic poles are connected is orthogonal to the direction in which both magnetic poles of the guided wave detection electromagnet are connected.

Further, the transmitting unit includes:
The direction of the bias magnetic field by the transmission bias electromagnet is a distance measurement direction for measuring the distance from the transmission unit or the reception unit to the damaged part,
arranged so that the excitation direction by the excitation electromagnet is perpendicular to the ranging direction;
It may also be a thing.

Further, the receiving unit includes:
The direction of the bias magnetic field by the reception bias electromagnet is the distance measurement direction,
arranged so that the direction connecting both magnetic poles of the guided wave detection electromagnet is perpendicular to the ranging direction;
It may also be a thing.

Further, the inspection target is piping,
The distance measurement direction is an axial direction of the piping,
A direction perpendicular to the ranging direction is a circumferential direction of the piping,
It may also be a thing.

Further, it includes a plurality of the transmitting units and a plurality of the receiving units arranged in a direction orthogonal to the ranging direction of the inspection target,
It may also be a thing.

Further, the cores of the transmission bias electromagnet and the excitation electromagnet are approximately U-shaped,
The excitation electromagnet is arranged between two magnetic poles that are legs of the core of the transmission bias electromagnet.
It may also be a thing.

Further, the cores of the reception bias electromagnet and the guided wave detection electromagnet are approximately U-shaped,
The guided wave detection electromagnet is disposed between both magnetic poles that are the legs of the core of the reception bias electromagnet.
It may also be a thing.

The invention also includes an eddy current unit that generates an eddy current in the inspection target and detects a change in a magnetic field caused by the eddy current detouring around the damaged part,
The eddy current unit is
an excitation electromagnet that generates the eddy current in the test object around both magnetic poles facing the test object by applying an alternating current to a coil;
an eddy current detection electromagnet that detects a magnetic field generated by the eddy current,
arranged so that a direction connecting both magnetic poles of the excitation electromagnet and a direction connecting both magnetic poles of the eddy current detection electromagnet are orthogonal;
It may also be a thing.

Further, the inspection target is piping,
A direction connecting both magnetic poles of the excitation electromagnet is an axial direction of the piping,
A direction connecting both magnetic poles of the guided wave detection electromagnet is a circumferential direction of the piping,
It may also be a thing.

Further, the eddy current unit is
serving as the transmitting unit or the receiving unit;
It may also be a thing.

The invention also includes a magnetic sensor that measures the strength of the magnetic field detected by the eddy current detection electromagnet.
It may also be a thing.

In the inspection method according to the second aspect of the invention,
By applying a direct current to the coil of the transmission bias electromagnet, a bias magnetic field is generated between the two magnetic poles facing the magnetic object to be inspected.
An alternating current is applied to the coil of the excitation electromagnet, which is arranged so that the direction connecting both magnetic poles is perpendicular to the direction connecting both magnetic poles of the transmission bias electromagnet, and magnetic flux between the two magnetic poles facing the inspection target is generated. and generating a guided wave by a magnetostrictive effect in the region to be inspected to which a bias magnetic field is applied by the transmission bias electromagnet,
By applying a direct current to the coil of the receiving bias electromagnet, a bias magnetic field is generated between the two magnetic poles facing the inspection target,
A guided wave detection electromagnet is arranged such that a direction connecting both magnetic poles facing the inspection target is orthogonal to a direction connecting both magnetic poles of the receiving bias electromagnet, and the guided wave detection electromagnet is reflected at the damaged part of the inspection target and the receiving bias An induced current generated by the guided wave passing through a region to which a bias magnetic field is applied by a bias electromagnet is detected.

According to the inspection apparatus and inspection method of the present invention, a guided wave is generated by exciting an inspection object to which a bias magnetic field is applied in a direction orthogonal to the bias magnetic field by the magnetostrictive effect, and the guided wave reflected at the damaged part is generated. Since detection is performed using an electromagnet placed perpendicular to the applied bias magnetic field, the S/N ratio during generation of guided waves and detection is increased, even when the inspection target has protective members, coatings, etc. , it is possible to inspect the damage to the inspection target with high accuracy.

1 is a conceptual diagram showing the configuration of an inspection device according to an embodiment of the present invention. It is a functional block diagram of an inspection device concerning an embodiment. 1A and 1B are diagrams showing the structure of a transmitting unit according to an embodiment, in which (A) is a plan view, (B) is a sectional view taken along line A-A' in (A), and (C) is a front view. 2A and 2B are diagrams showing the structure of a receiving unit according to an embodiment, in which (A) is a plan view, (B) is a sectional view taken along line A-A' in (A), and (C) is a front view. FIG. 2 is a diagram schematically representing a magnetic field generated in a transmitting unit, in which (A) is a front view and (B) is a side view. 2A and 2B are diagrams showing the structure of an eddy current unit according to an embodiment, in which (A) is a plan view, (B) is a sectional view taken along line A-A' in (A), and (C) is a front view. FIG. 2 is a conceptual diagram showing the principle of magnetic signal measurement using eddy current, in which (A) is a diagram when there is no damage to the piping, and (B) is a diagram when the piping is damaged. It is a flowchart which shows the flow of inspection processing concerning an embodiment. FIG. 2 is a diagram showing the configuration of an experimental device in which a flat plate is used to detect magnetic signals caused by eddy currents. It is a figure which shows the example of the detection position based on an experiment when the magnetic signal by an eddy current was detected using a flat plate. FIG. 3 is a diagram showing an example of experimental results when a magnetic signal due to eddy current is detected using a flat plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An inspection apparatus and inspection method according to an embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, an example will be described in which a pipe 50 made of a magnetic material and covered with a protective member such as a heat insulating material is inspected using the inspection apparatus 1 shown in FIGS. 1 and 2. explain.

The inspection device 1 includes a transmitting unit 11 that generates a guided wave in the piping 50, a receiving unit 12 that receives the guided wave reflected by the damaged part of the piping 50, an eddy current unit 13 that identifies the position of the damaged part, and an inspection It includes a control unit 20 that controls the operation of the device 1, a DC power supply 31, a function generator 32, a low noise amplifier 33, and a lock-in amplifier 34. The inspection device 1 also includes a fixing member 40 that fixes the transmitting unit 11, the receiving unit 12, the eddy current unit 13, etc. to the piping 50.

The transmission unit 11 includes a transmission bias electromagnet 111 and an excitation electromagnet 112, as shown in FIGS. 3A to 3C. The transmission bias electromagnet 111 includes a core 111a and a coil 111b, each of which is a substantially U-shaped magnetic body consisting of a center portion and both legs. will be placed in In this embodiment, the coil 111b is wound around the center of the core 111a, which is a substantially U-shaped ferrite core.

The excitation electromagnet 112 includes a core 112a and a coil 112b, each of which is a substantially U-shaped magnetic body consisting of a center portion and both legs. Placed. In this embodiment, the coil 112b is connected in series and wound around both legs of the core 112a, which is a substantially U-shaped ferrite core.

As described above, the coil 111b is wound around the center of the substantially U-shaped core 111a, and the coil 112b is connected and wound in series to both legs of the substantially U-shaped core 112a. . Thereby, it is possible to reduce the size of the transmitting unit 11 while avoiding interference between the coil 111b and the coil 112b. The winding positions of the coil 111b and the coil 112b are not limited to this. For example, the coil 111b may be wound around both legs of the core 111a, or the coil 112b may be wound around both legs of the core 112a at the center. It may be wrapped around the body. Thereby, a high magnetic flux density can be efficiently ensured in the coils 111b and 112b, so that the piping 50 to be inspected can be excited efficiently.

Further, as shown in FIGS. 3B and 3C, the excitation electromagnet 112 is arranged between the two magnetic poles that are the legs of the core 111a of the transmission bias electromagnet 111. Furthermore, the transmission bias electromagnet 111 and the excitation electromagnet 112 are arranged so that the direction in which the two magnetic poles of the transmission bias electromagnet 111 are connected is perpendicular to the direction in which the two magnetic poles of the excitation electromagnet 112 are connected.

The coil 111b of the transmission bias electromagnet 111 is connected to the DC power supply 31, and when a current is applied to the coil 111b, a magnetic field (bias magnetic field) is generated between the legs of the core 111a. The strength of the bias magnetic field generated by the transmission bias electromagnet 111 can be adjusted by the magnitude of the current applied by the DC power supply 31.

The coil 112b of the excitation electromagnet 112 is connected to the function generator 32. By applying an alternating current from the function generator 32 to the coil 112b, a magnetostrictive effect is produced in the piping 50. As a result, guided waves are generated in the pipe 50.

When a guided wave is generated using magnetostriction, the orientation of the magnetic domains of the test object, which is a magnetic material, is usually random. Therefore, when an excitation magnetic field is applied, magnetostriction occurs in each magnetic domain, and it is difficult to generate guided waves that are in phase as a whole and have little noise. In the inspection device 1 according to this embodiment, strong magnetostriction is caused by applying a bias magnetic field. Specifically, by applying a bias magnetic field to the pipe 50 to be inspected, the magnetic domains of the pipe 50 can be aligned. Therefore, by exciting the region to which the bias magnetic field is applied using the excitation electromagnet 112 disposed inside the transmission bias electromagnet 111, strong magnetostriction (vibration) with uniform phase can be generated.

The strength (size) of the guided wave generated in the inspection object can be adjusted by the strength of the bias magnetic field applied to the area where the magnetostrictive effect occurs; the stronger the bias magnetic field, the greater the magnetostriction, and the stronger the guided wave. occurs. In this embodiment, a transmission bias electromagnet 111 is arranged outside the excitation electromagnet 112, and the bias magnetic field in the region where the magnetostrictive effect is caused by the excitation electromagnet 112 is adjusted. Therefore, even if the outside of the piping 50 to be inspected is covered with a protective member such as a heat insulating material and the excitation electromagnet 112 cannot be brought into direct contact with the piping 50, the transmitting unit 11 with a simple configuration This makes it possible to generate guided waves with little noise and a high S/N ratio.

The receiving unit 12 includes a receiving bias electromagnet 121 and a guided wave detection electromagnet 122, as shown in FIGS. 4(A) to 4(C). The reception bias electromagnet 121 includes a core 121a and a coil 121b, each of which is a substantially U-shaped magnetic body consisting of a center portion and both legs. will be placed in In this embodiment, the coil 121b is wound around the center of the core 121a, which is a substantially U-shaped ferrite core.

The guided wave detection electromagnet 122 includes a core 122a and a coil 122b, which are approximately U-shaped magnetic bodies consisting of a center portion and both legs, and the end surfaces of both legs of the core 122a, which serve as magnetic poles, face the piping 50. It is arranged like this. In this embodiment, the coil 122b is connected in series and wound around both legs of the core 122a, which is a substantially U-shaped ferrite core.

As described above, the coil 121b is wound around the center of the substantially U-shaped core 121a, and the coil 122b is connected and wound in series to both legs of the substantially U-shaped core 122a. . Thereby, it is possible to reduce the size of the receiving unit 12 while avoiding interference between the coil 121b and the coil 122b. The winding positions of the coil 121b and the coil 122b are not limited to this. For example, the coil 121b may be wound around both legs of the core 121a, or the coil 122b may be wound around both legs of the core 122a at the center. It may be wrapped around the body. Thereby, a high magnetic flux density can be efficiently ensured in the coils 121b and 122b, so that the detection sensitivity of the reflected wave of the guided wave can be improved.

Further, as shown in FIGS. 4(B) and 4(C), the guided wave detection electromagnet 122 is arranged between both magnetic poles, which are the legs of the core 121a of the reception bias electromagnet 121. Further, the reception bias electromagnet 121 and the guided wave detection electromagnet 122 are arranged so that the direction in which the two magnetic poles of the reception bias electromagnet 121 are connected is orthogonal to the direction in which the two magnetic poles of the guided wave detection electromagnet 122 are connected. .

The coil 121b of the receiving bias electromagnet 121 is connected to the DC power supply 31, and when a current is applied to the coil 121b, a magnetic field (bias magnetic field) is generated between the legs of the core 121a. The strength of the bias magnetic field generated by the reception bias electromagnet 121 can be adjusted by the magnitude of the current applied by the DC power supply 31.

The coil 122b of the guided wave detection electromagnet 122 is connected to the control unit 20 via the low noise amplifier 33, and detects the induced current generated by the reflected wave of the guided wave. The receiving unit 12 uses the opposite effect of the magnetostrictive effect of the transmitting unit 11, so by applying a bias magnetic field to the guided wave detection region of the guided wave detection electromagnet 122, it detects magnetic signals with the same phase as an induced current. be able to. Thereby, it becomes possible to improve the accuracy of the inspection of the inspection target.

As described above, the transmitting unit 11 and the receiving unit 12 are electromagnet units each including two electromagnets, and have the same structure. Therefore, either one may be connected to the function generator 32 and used as the transmitting unit 11, and either one may be connected to the control unit 20 and used as the receiving unit 12, so that maintenance of the device such as parts replacement can be improved. I can do it.

Further, as shown in FIG. 1, the transmitting unit 11 and the receiving unit 12 are arranged apart from each other in the distance measuring direction in which the distance to the damaged part is measured, that is, in the axial direction (longitudinal direction) of the pipe 50. As shown in FIGS. 5A and 5B, in the transmission unit 11, the direction connecting both magnetic poles, which are the legs of the transmission bias electromagnet 111, is the axial direction of the piping 50 (Y-axis direction in FIG. 5). , contacts the protective member of the pipe 50 so that the direction connecting both magnetic poles, which are the legs of the excitation electromagnet 112, is perpendicular to the axial direction of the pipe 50 (circumferential direction, X-axis direction in FIG. 5). It is arranged so that Thereby, the excitation direction by the excitation electromagnet 112 becomes the circumferential direction of the pipe 50, and a guided wave, which is a T(0,1) mode SH wave, can be generated in the pipe 50. Moreover, when the piping 50 does not have a protection member, the transmitting unit 11 is arranged so as to be in contact with the piping 50.

The legs of each electromagnet of the transmitting unit 11 and the receiving unit 12 are preferably arranged so as to contact the piping 50 or the protective member in order to improve inspection accuracy. However, depending on the diameter of the pipe 50, it may be difficult to bring them into direct contact. In this case, there is a gap between the piping 50 or the protective member and the leg within a range where inspection accuracy can be ensured by adjusting the magnitude of the input current to generate the bias magnetic field (for example, within a range of about 5 mm or less). You can.

Similar to the transmitting unit 11 shown in FIGS. 5A and 5B, in the receiving unit 12, the direction connecting both magnetic poles, which are the legs of the core 121a of the receiving bias electromagnet 121, is the axial direction of the piping 50, and the guide The core 122a of the wave detection electromagnet 122 is arranged so as to be in contact with the protective member of the pipe 50 so that the direction connecting the two magnetic poles, which are the legs, is perpendicular to the axial direction of the pipe 50 (circumferential direction). Ru. Thereby, the guided wave, which is a T(0,1) mode SH wave, can be accurately detected by the guided wave detection electromagnet 122. Moreover, when the piping 50 does not have a protection member, the receiving unit 12 is arranged so that it may contact the piping 50.

Further, as shown in FIG. 1, in the inspection apparatus 1 according to the present embodiment, a plurality of transmitting units 11 and receiving units 12 are arranged at approximately equal intervals in the circumferential direction of the pipe 50. Although the number of transmitting units 11 and receiving units 12 is not particularly limited, for example, eight transmitting units 11 and receiving units 12 are disposed around the entire circumference of the pipe 50. Furthermore, the transmitting unit 11 and the receiving unit 12 are arranged so that their positions in the axial direction of the piping 50 overlap. As a result, the guided wave can be transmitted to the entire circumferential direction of the pipe 50, and by analyzing the reflected waves received by each receiving unit 12, the circumferential position of the damaged part of the pipe 50 can be roughly identified. be able to. Note that the position of the damaged part in the axial direction can be calculated based on the time from generation of the guided wave to reception of the reflected wave and the propagation speed of the guided wave.

The eddy current unit 13 includes an excitation electromagnet 131 and an eddy current detection electromagnet 132, as shown in FIGS. 6(A) to 6(C). The excitation electromagnet 131 includes a core 131a and a coil 131b, each of which is a substantially U-shaped magnetic body consisting of a center portion and both legs. Placed. In this embodiment, the coil 131b is wound around the center of the core 131a, which is a substantially U-shaped ferrite core.

The eddy current detection electromagnet 132 includes a core 132a and a coil 132b, which are substantially U-shaped magnetic bodies consisting of a center portion and both legs, and the end surfaces of the legs, which serve as magnetic poles of the core 132a, face the piping 50. It is arranged like this. In this embodiment, the coil 132b is connected in series and wound around both legs of a core 132a, which is a substantially U-shaped ferrite core.

As described above, the coil 131b is wound around the center of the substantially U-shaped core 131a, and the coil 132b is connected in series to both legs of the substantially U-shaped core 132a. . Thereby, it is possible to reduce the size of the eddy current unit 13 while avoiding interference between the coil 131b and the coil 132b. The winding positions of the coil 131b and the coil 132b are not limited to this. For example, the coil 131b may be wound around both legs of the core 131a, or the coil 132b may be wound around both legs of the core 132a at the center. It may be wrapped around the body. Thereby, a high magnetic flux density can be efficiently ensured in the coils 131b and 132b, so that eddy currents, which will be described later, can be efficiently generated and the detection sensitivity of magnetic signals derived from eddy currents can be improved.

Further, as shown in FIGS. 6(B) and 6(C), the eddy current detection electromagnet 132 is arranged between both magnetic poles that are the legs of the core 131a of the excitation electromagnet 131. Furthermore, the excitation electromagnet 131 and the eddy current detection electromagnet 132 are arranged so that the direction in which the two magnetic poles of the excitation electromagnet 131 are connected is perpendicular to the direction in which the two magnetic poles of the eddy current detection electromagnet 132 are connected.

The coil 131b of the excitation electromagnet 131 is connected to the function generator 32, and by applying an alternating current to the coil 131b, a magnetic field is generated in both legs of the core 131a, which interlinks with the piping 50. As a result, eddy currents are generated in the piping 50 around both magnetic poles, which are the legs of the core 131a.

The coil 132b of the eddy current detection electromagnet 132 is connected to the control unit 20 via the lock-in amplifier 34. Further, the lock-in amplifier 34 is connected to the function generator 32 and receives a reference signal.

As described above, in this embodiment, the direction in which the two magnetic poles of the excitation electromagnet 131 are connected is orthogonal to the direction in which the two magnetic poles of the eddy current detection electromagnet 132 are connected. As shown in FIG. 7A, when an excitation electromagnet 131 is placed outside and an alternating current is applied to the coil 131b, eddy currents are generated in the piping 50 around both magnetic poles, which are the legs of the core 131a. . A current flows through the coil 132b of the eddy current detection electromagnet 132 due to the influence of a magnetic field generated by the eddy current in a direction perpendicular to the plane of the paper in FIG. 7(A). As shown in FIG. 7B, when the piping 50 is damaged, the eddy current bypasses the damaged part, so the state of the magnetic field that the eddy current detection electromagnet 132 receives changes, and as a result, the current generated in the coil 132b changes. (the potential difference between both ends of the coil 132b) changes. In this embodiment, the position of the damaged part is detected by measuring the potential difference between both ends of the coil 132b at a plurality of positions near the damaged part.

Further, in this embodiment, the eddy current detection electromagnet 132 is arranged so that an axis connecting the centers of both magnetic poles of the eddy current detection electromagnet 132 is located on the center line of both magnetic poles of the exciting electromagnet 131. As shown in FIG. 7(A), when an excitation electromagnet 131 is placed outside and an alternating current is applied, positive (outflow) and negative (suction) Magnetic flux is generated. Here, when the excitation magnetic field of the excitation electromagnet 131 interlinks with the eddy current detection electromagnet 132, it becomes background noise in the measurement and the measurement accuracy decreases. Furthermore, when the amount of interlinked magnetic flux increases, magnetic saturation occurs, making it impossible for the eddy current detection electromagnet 132 to detect a magnetic signal. Therefore, in the eddy current unit 13 according to the present embodiment, the center line of both magnetic poles of the excitation electromagnet 131 (in FIG. The eddy current detection electromagnet 132 is arranged on the dashed line). Thereby, the excitation magnetic field of the excitation electromagnet 131 does not interlink with the eddy current detection electromagnet 132, and the magnetic signal derived from the eddy current can be accurately measured.

In the inspection device 1 according to the present embodiment, the transmitting unit 11 and the receiving unit 12 are used to identify the position of the damaged part in the pipe axis direction, and the eddy current unit 13 is arranged near the identified damaged part. Then, by shifting the position of the eddy current unit 13 near the damaged part and measuring changes in the magnetic field caused by the current detour, the exact position of the damaged part is detected.

As described above, the eddy current unit 13 is an electromagnet unit including two electromagnets, and has a similar structure to the transmitting unit 11 and the receiving unit 12.

The control unit 20 controls the operation of the inspection apparatus 1 as a whole. Specifically, the control unit 20 is connected to the transmitting unit 11, the receiving unit 12, and the eddy current unit 13 via a DC power supply 31, a function generator 32, a low noise amplifier 33, a lock-in amplifier 34, etc. It controls the transmission and reception of guided waves, calculates the distance to the damaged part, calculates the position of damage caused by eddy current, etc.

The control unit 20 includes a control section 21, a storage section 22, a display section 23, and an input section 24, as shown in the functional block diagram of FIG.

The control unit 21 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and controls the transmitting unit 11, the receiving unit 12, the eddy current unit 13, etc. The control unit 21 realizes each function of the control unit 21 shown in FIG. 2 by loading various operating programs and data stored in the ROM, storage unit 22, etc. of the control unit 21 into the RAM and operating the CPU. let Thereby, the control section 21 operates as a guided wave control section 211, a distance calculation section 212, an eddy current control section 213, and a damage position calculation section 214.

The guided wave control unit 211 controls the DC power supply 31 to apply a preset DC current to the transmission bias electromagnet 111 of the transmission unit 11 and the reception bias electromagnet 121 of the reception unit 12, thereby generating a bias magnetic field. let The guided wave control unit 211 also controls the function generator 32 to apply an alternating current to the excitation electromagnet 112 to generate a guided wave in the pipe 50 due to the magnetostrictive effect.

The distance calculating section 212 calculates the arrival time of the guided wave reflected at the damaged part of the pipe 50 from the output voltage of the guided wave detection electromagnet 122 of the receiving unit 12. Further, the distance calculation unit 212 calculates the arrival time of the guided wave from the transmitting unit 11 or the receiving unit 12 based on the calculated arrival time of the guided wave, the time when the guided wave control unit 211 generates the guided wave, and the preset propagation speed of the guided wave. The distance in the axial direction (distance measurement direction) of the pipe 50 from to the damaged part is calculated.

The eddy current control unit 213 controls the function generator 32 to apply an alternating current to the excitation electromagnet 131 of the eddy current unit 13 to generate an eddy current in the pipe 50.

The damage position calculating section 214 calculates the position of the damaged part from the magnetic signal measured as a voltage change using the eddy current unit 13 at each measurement position.

The storage unit 22 is a non-volatile memory such as a hard disk or a flash memory, and calculates the distance to the damaged part based on the set value of applied current for generating guided waves and eddy currents and the received signal of the receiving unit 12. Memorize programs, etc.

The display section 23 is a display device provided in the control unit 20, and is, for example, a liquid crystal panel. The display unit 23 displays the distance to the damaged part calculated based on guided wave measurement, the position of the damaged part calculated using eddy current, and the like.

The input unit 24 is an input device for inputting setting parameters such as input current values for generating guided waves and eddy currents. The input unit 24 is a keyboard, a mouse, etc. provided in the control unit 20.

The fixing member 40 is a member made of a non-magnetic material that attaches and fixes the transmitting unit 11, receiving unit 12, eddy current unit 13, etc. to the outer periphery of the pipe 50. The fixing member 40 may be any member as long as it can be fixed so that each magnetic pole of the transmitting unit 11, receiving unit 12, and eddy current unit 13 faces the outer circumference of the piping 50 or the protection member, and the shape of the fixing member 40 and the fixing method may vary. etc. are not particularly limited.

The flow of the inspection process according to this embodiment will be described below with reference to the flowchart in FIG.

First, the fixing member 40 of the inspection apparatus 1 including the transmitting unit 11 and the receiving unit 12 is installed in the piping 50 (step S1). The fixing member 40 is fixed to the piping 50 by a fixing means (not shown), and as shown in FIG. 1, the transmitting unit 11 and the receiving unit 12 are arranged at approximately equal intervals in the circumferential direction of the piping 50.

The guided wave control section 211 of the control unit 20 controls the DC power supply 31 to apply a voltage of a preset magnitude to the coil 111b of the transmission bias electromagnet 111 of the transmission unit 11 (step S2). As a result, a direct current flows through the coil 111b, and a bias magnetic field is generated between the legs, which are both magnetic poles, of the transmission bias electromagnet 111. In the region where the bias magnetic field is generated, the directions of the magnetic domains of the piping 50 are aligned.

Furthermore, the guided wave control section 211 controls the DC power supply 31 to apply a voltage of a preset magnitude to the coil 121b of the reception bias electromagnet 121 of the reception unit 12 (step S3). As a result, a direct current flows through the coil 121b, and a bias magnetic field is generated between the legs, which are both magnetic poles, of the receiving bias electromagnet 121. In the region where the bias magnetic field is generated, the directions of the magnetic domains of the piping 50 are aligned.

Subsequently, the guided wave control unit 211 controls the function generator 32 to apply an alternating current to the coil 112b of the excitation electromagnet 112 of the transmitting unit 11, and generates a guided wave, which is an SH wave, in the pipe 50 due to the magnetostrictive effect. (Step S4).

The distance calculating section 212 of the control unit 20 derives the reception time of the reflected wave of the guided wave from the voltage that is the output of the low noise amplifier 33 connected to the coil 122b of the guided wave detection electromagnet 122 of the receiving unit 12 ( Step S5).

The distance calculation unit 212 calculates the time from sending out the guided wave to detecting the reflected wave based on the arrival time of the guided wave derived in step S5 and the generation time of the guided wave in step S4. In addition, the distance in the axial direction from the transmitting unit 11 or the receiving unit 12 to the damaged part of the pipe 50 is calculated based on the propagation velocity of the guided wave that has been obtained in advance through actual measurement and stored in the storage unit 22 ( Step S6). Further, calculation of these distances is performed by a combination of the respective transmitting units 11 and receiving units 12 arranged overlapping in the axial direction. As a result, the approximate circumferential position of the damaged portion can be grasped.

Next, based on the distance calculated in step S6, the fixing member 40 of the inspection device 1 is moved and fixed to the pipe 50 so that the eddy current unit 13 is located near the damaged part (step S7). As shown in FIG. 1, a plurality of eddy current units 13 according to the present embodiment are arranged at equal intervals in the circumferential direction of the pipe 50. By sequentially performing measurements with a plurality of eddy current units 13, inspection can be performed efficiently.

The eddy current control unit 213 sequentially applies an alternating current to each eddy current unit 13 and measures a magnetic signal based on the eddy current generated in the pipe 50 (step S8). In this embodiment, the potential difference generated in the coil 132b of the eddy current detection electromagnet 132 is measured as a magnetic signal based on eddy current.

The damage position calculation unit 214 displays the measurement result representing the measurement value and the measurement position on the display unit 23 and stores it in the storage unit 22 (step S9). After measuring each eddy current unit 13, the operator refers to the measurement results displayed on the display unit 23 and continues the measurement until the position, shape, etc. of the damaged part can be determined (NO in step S10). . Specifically, the operator refers to the measurement results, moves the fixing member 40 of the inspection device 1 to change the position of the eddy current unit 13 in the axial direction, and inputs the changed position from the input unit 24. (Step S11).

The measurements in steps S8 to S9 are repeated at the changed position. Specifically, an alternating current is applied to each eddy current unit 13, and a magnetic signal based on the eddy current is measured. Then, the damage position calculation section 214 displays the measurement result at the position changed in step S11 and the previous measurement result together on the display section 23 and stores it in the storage section 22.

When the acquisition of measurement data for understanding the position, shape, etc. of the damaged part is completed, the operator removes the fixing member 40 of the inspection device 1 from the pipe 50, and finishes the pipe inspection.

9 and 10 are diagrams showing the configuration of an experimental apparatus when searching for damaged parts due to eddy current using a flat plate as an inspection object, and FIG. 11 is an example of measurement results. In this example, as shown in FIGS. 9 and 10, eddy current units 13 are sequentially placed at 36 measurement positions around a slit made to imitate a damaged area, and a sine wave voltage of 0. 1V _pp , a frequency of 10 kHz, and an excitation current value of 40 mA _pp were input to the excitation electromagnet 131. The excitation current value was measured using an oscilloscope from the voltage across a 1Ω resistor. Further, as a reference signal for the lock-in amplifier 34, a clock signal with a frequency of 10 kHz was applied from the function generator 32.

Further, the output voltage of the lock-in amplifier 34 was used as a measurement value representing a magnetic signal based on eddy current. More specifically, from the values displayed by X (real part voltage [mV]) and Y (imaginary part voltage [mV]) of the lock-in amplifier 34, the voltage and phase difference are calculated based on the following formula. Calculated.

As shown in the contour map showing the magnitude of the measured voltage in FIG. It can be seen that it has been identified.

As described above, according to the inspection apparatus and inspection method of the present invention, a region to be inspected to which a bias magnetic field is applied is excited by the magnetostrictive effect in a direction perpendicular to the bias magnetic field to generate guided waves. . Furthermore, a guided wave that is reflected at the damaged area and passes through the area to which the bias magnetic field is applied is detected by an electromagnet placed perpendicular to the applied bias magnetic field. Therefore, the S/N ratio at the time of generation and detection of guided waves is increased, and even when the test object has a protective member, coating, etc., it is possible to accurately test the test object made of magnetic material.

Furthermore, in the inspection device 1 according to the present embodiment, the direction of the bias magnetic fields of the transmitting unit 11 and the receiving unit 12 is set as the ranging direction, and both the excitation direction of the transmitting unit 11 and the guided wave detection electromagnet 122 of the receiving unit 12 are set as the ranging direction. The direction in which the magnetic poles are connected is perpendicular to the ranging direction. This makes it possible to efficiently generate and detect T(0,1) mode guided waves, which are easy to separate from other modes of guided waves and whose propagation speed changes little with frequency, with a high S/N ratio. Inspection accuracy improves.

Furthermore, in the inspection device 1 according to the present embodiment, the distance from the transmitting unit 11 or the receiving unit 12 to the damaged part is calculated, and the eddy current unit 13 is arranged near the damaged part based on the calculated distance. Measurements will be taken to pinpoint the detailed location of the damaged area. The eddy current unit 13 is configured such that the direction in which the magnetic poles of the excitation electromagnet 131 that generates eddy currents are connected is orthogonal to the direction in which the magnetic poles of the eddy current detection electromagnet 132 that detects the magnetic field generated by the eddy current are connected. There is. Thereby, a magnetic signal based on eddy current can be detected with high accuracy with a simple configuration, and the position of the damaged part can be specified.

In the above-described embodiment, the inspection apparatus 1 was described that inspected piping made of magnetic material, but the inspection subject is not limited to piping. For example, even when inspecting tanks coated with heat insulating paint or other coatings for magnetic materials, plates used for highway steel decks, containers, etc., the inspection apparatus according to the present invention can be used for inspection. A method can be used. In this case, the transmitting unit 11 and the receiving unit 12 are arranged with the longitudinal direction of the inspection object as the ranging direction, the distance to the damaged part is calculated, and the eddy current unit 13 is placed near the damaged part based on the calculated distance. By positioning and detecting the detailed position of the damaged part, inspection can be carried out efficiently.

Further, in the inspection device 1 according to the present embodiment, the transmitting unit 11, the receiving unit 12, and the eddy current unit 13 are electromagnet units having the same structure and including two electromagnets. Thereby, maintenance of the device such as parts replacement can be improved.

In this embodiment, the eddy current unit 13 is provided separately from the transmitting unit 11 and the receiving unit 12, but the present invention is not limited to this. For example, the receiving unit 12 and the eddy current unit 13 may be used in common. Thereby, the structure of the inspection device 1 can be simplified and manufacturing costs can be reduced. In this case, a switch is provided between the transmitting unit 11 or the receiving unit 12 and the DC power supply 31, the function generator 32, the low noise amplifier 33, or the lock-in amplifier 34, and by switching the connection destination, the transmitting bias electromagnet 111 or The reception bias electromagnet 121 may be operated as the excitation electromagnet 131, and the excitation electromagnet 112 or the guided wave detection electromagnet 122 may be operated as the eddy current detection electromagnet 132.

In this embodiment, each electromagnet of the transmitting unit 11, the receiving unit 12, and the eddy current unit 13 has a ferrite core, but the present invention is not limited to this. For example, if the magnetostriction effect of the object to be inspected is small and a stronger magnetic field is desired to be applied, the material of the core of each electromagnet may be a magnetic material having a higher saturation magnetic flux density, such as permalloy or permendur.

In the inspection apparatus 1 according to the present embodiment, the operator attaches the fixing member 40 of the inspection apparatus 1 to the pipe 50 and performs the pipe inspection while moving it, but the invention is not limited to this. For example, the fixing member 40 may be provided with a mechanism for moving the pipe 50 in the axial direction. Thereby, it is possible to efficiently switch between measurement using guided wave transmission and reception and measurement using eddy current, and measurement using eddy current near the damaged part.

Although the eddy current unit 13 according to the present embodiment is arranged so that the direction connecting both magnetic poles of the eddy current detection electromagnet 132 is the axial direction of the piping 50, the present invention is not limited to this. . For example, in FIG. 7A, there is a slit-shaped damaged part in the axial direction of the piping 50 (in the left-right direction in the paper), and the eddy current is When the unit 13 is arranged, the eddy current flows in the vertical direction in FIG. 7(A) near the detection electromagnet. In this case, damage perpendicular to the direction of the eddy current will disrupt the current flow and will be easier to detect. On the other hand, in FIG. 7A, when the slit-shaped damaged portion is in the vertical direction, the disturbance of the eddy current becomes small. Therefore, in measuring the damage position using the eddy current unit 13, it is preferable to arrange the eddy current unit 13 at a predetermined angle and perform the inspection, and then rotate the eddy current unit 13 by 90 degrees and perform the inspection. Thereby, the possibility of overlooking damage to the piping 50 can be reduced.

Furthermore, although the inspection device 1 according to the present embodiment detects the output of the receiving unit 12 and the output of the eddy current unit 13 by the control unit 20 via the amplifier, the present invention is not limited to this. For example, the measurement may be performed by transmitting a signal to a magnetic sensor placed near the guided wave detection electromagnet 122 and the eddy current detection electromagnet 132. In this case, the magnetic sensor may be selected depending on the strength of the magnetic signal to be detected. Specifically, when the intensity of the magnetic signal to be detected is on the order of 1×10 ⁻⁹ T (=1 nT) or less, SQUID (superconducting quantum interference device), which can detect minute changes in magnetic field, is used as a magnetic sensor. , a high-sensitivity magnetic sensor such as a flux gate may be used. This makes it possible to perform piping inspections with high accuracy.

1 inspection device, 11 transmission unit, 111 electromagnet for transmission bias, 112 electromagnet for excitation, 111a, 112a core, 111b, 112b coil, 12 reception unit, 121 electromagnet for reception bias, 122 electromagnet for guided wave detection, 121a, 122a core , 121b, 122b coil, 13 eddy current unit, 131 exciting electromagnet, 132 eddy current detection electromagnet, 131a, 132a core, 131b, 132b coil, 20 control unit, 21 control section, 211 guided wave control section, 212 distance calculation part, 213 eddy current control part, 214 damage position calculation part, 22 storage part, 23 display part, 24 input part, 31 DC power supply, 32 function generator, 33 low noise amplifier, 34 lock-in amplifier, 40 fixing member, 50 piping

Claims (12)

A transmitting unit that generates guided waves on a magnetic object to be inspected;
a receiving unit that receives the guided wave transmitted from the transmitting unit and reflected by the damaged part of the inspection target,
The transmitting unit is
a transmission bias electromagnet that generates a bias magnetic field between two magnetic poles facing the inspection target by applying a direct current to a coil;
Applying an alternating current to the coil to change the magnetic flux between the two magnetic poles facing the test object, and generate the guided wave by the magnetostrictive effect in the region of the test object to which a bias magnetic field is applied by the transmission bias electromagnet. an excitation electromagnet,
arranged so that a direction connecting both magnetic poles of the transmission bias electromagnet and a direction connecting both magnetic poles of the excitation electromagnet are perpendicular to each other,
The receiving unit includes:
a receiving bias electromagnet that generates a bias magnetic field between both magnetic poles facing the inspection target by applying a direct current to a coil;
a guided wave detection electromagnet with both magnetic poles facing the inspection target and detecting an induced current generated by the guided wave passing through a region to which a bias magnetic field is applied by the reception bias electromagnet;
arranged so that a direction connecting both magnetic poles of the receiving bias electromagnet and a direction connecting both magnetic poles of the guided wave detection electromagnet are perpendicular to each other;
An inspection device characterized by: The transmitting unit is
The direction of the bias magnetic field by the transmission bias electromagnet is a distance measurement direction for measuring the distance from the transmission unit or the reception unit to the damaged part,
arranged so that the excitation direction by the excitation electromagnet is perpendicular to the distance measurement direction;
The inspection device according to claim 1, characterized in that: The receiving unit includes:
The direction of the bias magnetic field by the reception bias electromagnet is the distance measurement direction,
arranged so that the direction connecting both magnetic poles of the guided wave detection electromagnet is perpendicular to the ranging direction;
The inspection device according to claim 2, characterized in that: The inspection target is piping,
The distance measurement direction is an axial direction of the piping,
A direction perpendicular to the ranging direction is a circumferential direction of the piping,
The inspection device according to claim 2 or 3, characterized in that: comprising a plurality of the transmitting units and a plurality of the receiving units arranged in a direction orthogonal to the ranging direction of the inspection target;
The inspection device according to claim 3, characterized in that: The cores of the transmission bias electromagnet and the excitation electromagnet are approximately U-shaped;
The excitation electromagnet is arranged between two magnetic poles that are legs of the core of the transmission bias electromagnet.
The inspection device according to claim 1, characterized in that: The cores of the reception bias electromagnet and the guided wave detection electromagnet are approximately U-shaped;
The guided wave detection electromagnet is disposed between both magnetic poles that are the legs of the core of the reception bias electromagnet.
The inspection device according to claim 1, characterized in that: an eddy current unit that generates an eddy current in the inspection target and detects a change in the magnetic field caused by the eddy current bypassing the damaged part,
The eddy current unit is
an excitation electromagnet that generates the eddy current in the test object around both magnetic poles facing the test object by applying an alternating current to a coil;
an eddy current detection electromagnet that detects a magnetic field generated by the eddy current,
arranged so that a direction connecting both magnetic poles of the excitation electromagnet and a direction connecting both magnetic poles of the eddy current detection electromagnet are orthogonal;
The inspection device according to claim 1, characterized in that: The inspection target is piping,
A direction connecting both magnetic poles of the excitation electromagnet is an axial direction of the piping,
A direction connecting both magnetic poles of the guided wave detection electromagnet is a circumferential direction of the piping,
The inspection device according to claim 8, characterized in that: The eddy current unit is
serving as the transmitting unit or the receiving unit;
The inspection device according to claim 8, characterized in that: comprising a magnetic sensor that measures the strength of the magnetic field detected by the eddy current detection electromagnet;
The inspection device according to claim 8, characterized in that: By applying a direct current to the coil of the transmission bias electromagnet, a bias magnetic field is generated between the two magnetic poles facing the magnetic object to be inspected.
An alternating current is applied to the coil of the excitation electromagnet, which is arranged so that the direction connecting both magnetic poles is perpendicular to the direction connecting both magnetic poles of the transmission bias electromagnet, and magnetic flux between the two magnetic poles facing the inspection target is generated. and generating a guided wave by a magnetostrictive effect in the region to be inspected to which a bias magnetic field is applied by the transmission bias electromagnet,
By applying a direct current to the coil of the receiving bias electromagnet, a bias magnetic field is generated between the two magnetic poles facing the inspection target,
A guided wave detection electromagnet is arranged such that a direction connecting both magnetic poles facing the inspection target is orthogonal to a direction connecting both magnetic poles of the receiving bias electromagnet, and the guided wave detection electromagnet is reflected at the damaged part of the inspection target and the receiving bias detecting an induced current generated by the guided wave passing through a region to which a bias magnetic field is applied by a bias electromagnet;
An inspection method characterized by: