JP7786089B2 - Eddy current flaw detection device and flaw detection method - Google Patents

Description

This disclosure relates to an eddy current flaw detection device and a flaw detection method.

Traditionally, steel bridge inspections have been carried out by visual inspection and magnetic particle testing (MT). If paint cracks or rust are discovered during a visual inspection, the paint is first peeled off from the area where the cracks or rust are present to expose the metal part. Magnetic particle testing is then used to detect the presence or absence of flaws (cracks) in the metal part.

However, magnetic particle testing requires the paint film to be removed, which increases costs due to the need to secure personnel and the increased manpower required.

Therefore, technology is being considered that uses an eddy current flaw detector to perform flaw detection through the paint film (see, for example, Patent Document 1). In this case, if the detection signal obtained by the eddy current flaw detector exceeds a predetermined threshold, it is determined that a flaw is present.

Patent No. 5191873

The detection signal from an eddy current flaw detector is strongest when the direction of the central axis of the detection coil coincides with the depth direction of the flaw.

However, it is not possible to visually check the depth direction of a flaw from above the paint film. Furthermore, the location of the crack in the paint film and the location of the flaw may not coincide, making it impossible to confirm the location of the flaw from above the paint film. Therefore, skilled techniques are required to align the direction of the detection coil's central axis with the depth direction of the flaw, and depending on the skill level of the inspection technician, there is a risk of the flaw being misidentified or overlooked due to errors in the signal strength of the detection signal.

In light of these issues, the present disclosure aims to provide an eddy current flaw detection device and flaw detection method that can prevent flaws from being overlooked.

In order to solve the above problem, an eddy current flaw detection device according to one aspect of the present disclosure includes a probe body having a contact surface with an object to be detected, in which a first plate and a second plate are joined by a weld ; an excitation coil provided in the probe body; a first detection coil provided in the probe body and having a central axis that is approximately perpendicular to the contact surface; a second detection coil provided in the probe body and having a central axis that forms an acute angle with the central axis of the first detection coil; an excitation unit that applies an alternating current to the excitation coil to generate an induced current in the object to be detected by electromagnetic induction; and a detection unit that detects a second detection signal based on the induced current through the second detection coil while detecting a first detection signal based on the induced current through the first detection coil, and is configured to be able to detect flaws that may occur in the object to be detected that extend in a first direction and flaws that extend in a second direction different from the first direction .

The first and second detection coils may also be arranged between the excitation coil and the contact surface.

The second detection coil may also have a central axis that forms an angle of 35° or more and 55° or less with the central axis of the first detection coil.

In order to solve the above problem, a flaw detection method according to one aspect of the present disclosure uses an eddy current flaw detection device that includes: a probe body having a contact surface with an object to be detected, the object being formed by joining a first plate and a second plate by a weld ; an excitation coil provided in the probe body; a first detection coil provided in the probe body, the central axis of which is approximately perpendicular to the contact surface; and a second detection coil provided in the probe body, the central axis of which forms an acute angle with the central axis of the first detection coil, and is configured to be able to detect flaws that may occur in the object to be detected, extending in a first direction and flaws that extend in a second direction different from the first direction, the flaw detection method including the steps of: applying an alternating current to the excitation coil to generate an induced current in the object to be detected by electromagnetic induction; detecting a second detection signal based on the induced current through the second detection coil while detecting a first detection signal based on the induced current through the first detection coil; and notifying the presence of a flaw when the difference between the signal strength of the first detection signal and the signal strength of the second detection signal is equal to or greater than a predetermined value.

This disclosure makes it possible to prevent flaws from being overlooked.

FIG. 1 is a diagram illustrating an object to be inspected by an eddy current flaw detector according to this embodiment. FIG. 2 shows an eddy current flaw detection device according to this embodiment, which includes a probe and a control unit. FIG. 3 is a diagram illustrating the probe according to this embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a diagram illustrating the relationship between a flaw occurring in the support and the first and second detection coils. FIG. 6 is a functional block diagram of the control unit according to this embodiment. FIG. 7 is a flowchart showing the flow of processing in the flaw detection method according to this embodiment. FIG. 8 is a diagram illustrating a detection signal when the contact surface is in contact with the object to be inspected and there is no flaw. FIG. 9 is a diagram illustrating a detection signal when the contact surface is in contact with the object to be inspected and there is a flaw.

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values shown in these embodiments are merely examples for ease of understanding and, unless otherwise specified, do not limit the present disclosure. Furthermore, in this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

Figure 1 is a diagram illustrating an object 10 to be inspected by an eddy current flaw detection device 100 according to this embodiment. In Figure 1 of this embodiment and Figure 5 described below, the perpendicularly intersecting X-axis (horizontal direction, road width direction), Y-axis (horizontal direction, road length direction), and Z-axis (vertical direction) are defined as shown.

As shown in Figure 1, the object to be inspected 10 is, for example, a steel bridge. The object to be inspected 10 includes a support 20 and a pavement 30.

The support body 20 is a deck slab made of steel members. The support body 20 supports the vertical downward load from vehicles. The surface of the support body 20 is covered with a paint film. The support body 20 includes a first plate 22, a second plate 24, and a weld 26.

The first plate 22 is a steel plate extending in a generally horizontal direction. The second plate 24 is a steel plate extending vertically downward from the first plate 22. The second plate 24 is welded (e.g., fillet welded) to the first plate 22. The welded portion 26 is a portion formed as a result of welding the first plate 22 and the second plate 24 together.

The pavement 30 is layered on the first plate 22. The pavement 30 is made of asphalt or the like. Vehicles run on the pavement 30.

Due to fatigue caused by vehicles passing over the pavement 30, cracks and other defects may occur in the welds 26 of the support body 20. The cracks propagate from the welds 26 toward the first plate 22 or from the welds 26 toward the second plate 24.

The eddy current flaw detector 100 shown in Figure 2 below inspects the support 20 for flaws.

[Eddy current flaw detection device 100]
2, the eddy current flaw detector 100 according to this embodiment includes a probe 110 and a control unit 120. Each component will be described below.

[Probe 110]
3 is a diagram illustrating the probe 110 according to this embodiment, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG.

As shown in Figures 3 and 4, the probe 110 includes a probe body 210, a first coil unit 220, and a second coil unit 230.

The probe body 210 includes a grip portion 212, a contact surface 214, and an inclined surface 216. The probe body 210 is formed, for example, from plastic.

The gripping portion 212 is, for example, a rectangular prism-shaped portion. The gripping portion 212 is held by an inspection technician.

The contact surface 214 is provided at the tip 210a of the probe body 210. The contact surface 214 is a flat surface that can come into contact with the object 10 to be inspected. That is, the inspection engineer grasps the gripping portion 212 and brings the contact surface 214 into contact with the object 10 to be inspected to perform inspection. Furthermore, when performing inspection, the inspection engineer brings the contact surface 214 into contact with the object 10 to be inspected so that the depth direction in Figure 4 coincides with the Y-axis direction in Figure 1. In this embodiment, the area of the contact surface 214 is smaller than the cross-sectional area of the gripping portion 212.

The inclined surfaces 216 are provided between the grip portion 212 and the contact surface 214. In this embodiment, the probe body 210 has four inclined surfaces 216. The inclination angles of the four inclined surfaces 216 may be equal or different.

The first coil unit 220 is composed of a first detection coil 222 and a first excitation coil 224. The second coil unit 230 is composed of a second detection coil 232 and a second excitation coil 234. The first coil unit 220 and the second coil unit 230 are substantially identical in configuration except for the angle they make with the contact surface 214 and their positions within the probe body 210. Furthermore, the first coil unit 220 is positioned at a different depth direction position in Figure 4 than the second coil unit 230.

The first detection coil 222 is provided within the probe body 210. The central axis of the first detection coil 222 is perpendicular to the contact surface 214. In other words, the angle α between the central axis of the first detection coil 222 and the contact surface 214 is 90°.

The first excitation coil 224 (excitation coil) is provided within the probe body 210. The first excitation coil 224 is provided farther from the contact surface 214 than the first detection coil 222. In other words, the first detection coil 222 is provided between the first excitation coil 224 and the contact surface 214. This makes it possible to suppress input of noise due to the AC current applied by the first excitation coil 224 to the first detection coil 222.

The central axis of the first excitation coil 224 (depth direction in Figure 4) is perpendicular to the central axis of the first detection coil 222.

The second detection coil 232 is provided within the probe body 210. The angle β between the central axis of the second detection coil 232 and the central axis of the first detection coil 222 is an acute angle (greater than 0° and less than 90°). The angle β is, for example, greater than or equal to 35° and less than or equal to 55°. In this embodiment, the angle β is 45°.

The second excitation coil 234 (excitation coil) is provided within the probe body 210. The second excitation coil 234 is provided farther from the contact surface 214 than the second detection coil 232. In other words, the second detection coil 232 is provided between the second excitation coil 234 and the contact surface 214. This makes it possible to suppress input of noise due to the AC current applied by the second excitation coil 234 to the second detection coil 232.

The central axis of the second excitation coil 234 (the depth direction in Figure 4) is perpendicular to the central axis of the second detection coil 232.

Figure 5 is a diagram illustrating the relationship between a flaw occurring in the support 20 and the first and second detection coils 222 and 232. Note that dashed lines in Figure 5 indicate flaws. Also, thick lines in Figure 5 indicate the direction 222a of the central axis of the first detection coil 222 and the direction 232a of the central axis of the second detection coil 232.

Stress is applied to the support 20 in a direction in which the first plate 22 and the second plate 24 move apart or move closer to each other. Therefore, as shown in FIG. 5, flaws propagate from the ends 26a, 26b of the weld 26. Furthermore, flaws often propagate in direction A, direction B, direction C, or direction D on the support 20. Direction A is a direction (Z-axis direction in FIG. 5) perpendicular to the in-plane direction of the first plate 22 (XY in-plane direction in FIG. 5). Direction B is a direction (X-axis direction in FIG. 5) perpendicular to the in-plane direction of the second plate 24 (YZ in-plane direction in FIG. 5). Direction C is a direction that forms a 45° angle with the in-plane direction of the first plate 22. Direction D is a direction that forms a 45° angle with the in-plane direction of the second plate 24.

When the inspection technician scans the probe 110 over the support 20, it scans the first plate 22, the weld 26, and the second plate 24 in that order, or the second plate 24, the weld 26, and the first plate 22 in that order.

Here, when the contact surface 214 of the probe 110 contacts the first plate 22 and the inclined surface 216 contacts the welded portion 26, the direction 222a of the central axis of the first detection coil 222 can be made to roughly coincide with direction A. Furthermore, since the angle β formed between the central axis of the first detection coil 222 and the central axis of the second detection coil 232 is 45°, when the direction 222a of the central axis of the first detection coil 222 is made to coincide with direction A, the direction 232a of the central axis of the second detection coil 232 can be made to coincide with direction C.

Similarly, when the contact surface 214 of the probe 110 contacts the second plate 24 and the inclined surface 216 contacts the weld 26, the direction 222a of the central axis of the first detection coil 222 can be made to roughly coincide with direction D. Furthermore, since the angle β formed between the central axis of the first detection coil 222 and the central axis of the second detection coil 232 is 45°, when the direction 222a of the central axis of the first detection coil 222 is made to coincide with direction D, the direction 232a of the central axis of the second detection coil 232 can be made to coincide with direction B.

Therefore, with the contact surface 214 in contact with the first plate 22, the probe 110 according to this embodiment can align a flaw that has propagated in direction A with the direction 222a of the central axis of the first detection coil 222, and can align a flaw that has propagated in direction B with the direction 232a of the central axis of the second detection coil 232. Similarly, with the contact surface 214 in contact with the second plate 24, the probe 110 according to this embodiment can align a flaw that has propagated in direction D with the direction 222a of the central axis of the first detection coil 222, and can align a flaw that has propagated in direction C with the direction 232a of the central axis of the second detection coil 232.

[Control unit 120]
6 is a functional block diagram of the control unit 120 according to this embodiment. As shown in FIG. 6, the control unit 120 includes an excitation unit 310, a detection unit 330, an A/D converter 340, a central control unit 360, a memory 370, and a display device 380.

The excitation unit 310 applies an alternating current to the first excitation coil 224 and the second excitation coil 234, generating an induced current in the object 10 (support 20) to be inspected by electromagnetic induction. In this embodiment, the excitation unit 310 includes a function generator 312 and an amplifier 314.

Function generator 312 (indicated by "F/G" in Figure 6) generates an AC signal of a first frequency and an AC signal of a second frequency different from the first frequency. The AC signals from function generator 312 are output to amplifier 314 and detection unit 330.

The amplifier 314 (denoted by "B/P" in Figure 6) amplifies the AC signal of the first frequency generated by the function generator 312 and applies AC current to the first excitation coil 224. Similarly, the amplifier 314 amplifies the AC signal of the second frequency generated by the function generator 312 and applies AC current to the second excitation coil 234. This generates an induced current in the object 10 to be inspected due to electromagnetic induction. The amplifier 314 is, for example, a bipolar power supply.

The detection unit 330 is composed of, for example, a lock-in amplifier (indicated by "L/I" in Figure 6). The detection unit 330 extracts the frequency component of the current applied to the first excitation coil 224 (first detection signal based on induced current) from the AC voltage detected by the first detection coil 222 based on the AC signal (reference signal) of the first frequency output from the function generator 312. Similarly, the detection unit 330 extracts the frequency component of the current applied to the second excitation coil 234 (second detection signal based on induced current) from the AC voltage detected by the second detection coil 232 based on the AC signal (reference signal) of the second frequency output from the function generator 312.

The A/D converter 340 (denoted by "A/D" in Figure 6) converts the output value (analog signal) of the detection unit 330 into a digital signal.

The central control unit 360 is composed of a semiconductor integrated circuit that includes a CPU (central processing unit). The central control unit 360 reads programs and parameters for operating the CPU from ROM. The central control unit 360 works in conjunction with RAM as a work area and other electronic circuits to manage and control the entire eddy current flaw detection device 100.

Memory 370 is composed of ROM, RAM, flash memory, HDD, etc. Memory 370 stores programs and various data used by the central control unit 360.

The display device 380 is composed of a liquid crystal display, an organic EL (Electro Luminescence) display, etc.

In addition, in this embodiment, the central control unit 360 functions as a determination unit 362 and a notification unit 364.

The determination unit 362 determines whether or not there is a flaw based on the signal strength of the first detection signal detected through the first detection coil 222 and the signal strength of the first detection signal detected through the second detection coil 232. The determination of whether or not there is a flaw by the determination unit 362 will be described in detail later.

If the determination unit 362 determines that a flaw exists, the notification unit 364 displays this information on the display device 380.

[Flaw detection method]
Next, a flaw detection method for detecting flaws in the object 10 to be detected using the eddy current flaw detection device 100 will be described. Fig. 7 is a flowchart showing the processing flow of the flaw detection method according to this embodiment. As shown in Fig. 7, the flaw detection method according to this embodiment includes a current application step S110, a signal detection step S120, a first determination step S130, a first notification step S140, a second determination step S150, a second notification step S160, a third determination step S170, and a third notification step S180. Each step will be described below.

[Current application step S110]
The current application step S110 is a step in which the excitation unit 310 applies an AC current to the first excitation coil 224 and the second excitation coil 234 to generate an induced current by electromagnetic induction in the object to be detected 10. As described above, the excitation unit 310 applies an AC current of a first frequency to the first excitation coil 224 and applies an AC current of a second frequency to the second excitation coil 234.

[Signal detection step S120]
The signal detection step S120 is a step in which the detection unit 330 detects a first detection signal S1 based on an induced current through the first detection coil 222, while detecting a second detection signal S2 based on an induced current through the second detection coil 232. In this embodiment, the detection unit 330 simultaneously detects the first detection signal S1 and the second detection signal S2.

Figure 8 shows the detection signal when the contact surface 214 is in contact with the object 10 to be inspected and there is no flaw. Figure 9 shows the detection signal when the contact surface 214 is in contact with the object 10 to be inspected and there is a flaw.

As shown in Figures 8 and 9, the detection signal is represented by a Lissajous waveform. The Lissajous waveform shows the fluctuations in the sine component (amplitude, vertical axis in Figures 8 and 9) and cosine component (phase, horizontal axis in Figures 8 and 9) of the detection signal, with the excitation voltage as the reference. In the eddy current flaw detector 100, the probe 110 is brought into contact with a standard test piece for calibration, and adjustment (origin correction) is performed so that the reference point of the Lissajous waveform is the origin (0,0). After the origin correction is performed, flaw detection is performed using the eddy current flaw detector 100. Therefore, the reference point of the Lissajous waveform is the origin (0,0). In the Lissajous waveform, the sine component and cosine component of the detection signal fluctuate with the origin as the reference point.

As shown in Figure 8, when there is no flaw, the fluctuation range of the sine component of the detection signal is approximately zero. On the other hand, as shown in Figure 9, when there is a flaw, the fluctuation range of the sine component of the detection signal becomes larger than when there is no flaw.

The detection unit 330 therefore determines the fluctuation range of the sine component of the detection signal as the signal strength Sc of the detection signal. Note that the signal strength Sc of the detection signal is the value from the minimum value (negative peak) to the maximum value (positive peak) of the vertical axis (sine component) of the Lissajous waveform.

[First determination step S130]
7, the determination unit 362 determines whether the signal strength Sc of the first detection signal S1 is equal to or greater than the threshold value Th and whether the signal strength Sc of the second detection signal S2 is equal to or greater than the threshold value Th. The threshold value Th is determined in advance based on the depth of the flaw that is desired to be detected.

If the determination unit 362 determines that the signal strength Sc of the first detection signal S1 is equal to or greater than the threshold value Th and that the signal strength Sc of the second detection signal S2 is equal to or greater than the threshold value Th (YES in S130), the determination unit 362 proceeds to the first notification step S140. On the other hand, if the determination unit 362 determines that either or both of the signal strength Sc of the first detection signal S1 and the signal strength Sc of the second detection signal S2 are not equal to or greater than the threshold value Th (NO in S130), the determination unit 362 proceeds to the second determination step S150.

[First notification step S140]
The notification unit 364 causes the display device 380 to display a message stating that "A flaw has been detected or lift-off has occurred."

Even if there is no flaw, when the contact surface 214 and the object 10 to be detected separate, noise (lift-off signal) occurs, causing the sine component of the detection signal to fluctuate. Because the separation distance between the first detection coil 222 and the object 10 to be detected and the separation distance between the second detection coil 232 and the object 10 to be detected are substantially equal, the lift-off signal is detected through both the first detection coil 222 and the second detection coil 232.

Furthermore, even if the contact surface 214 is in contact with the object 10 to be detected, if the flaw is larger than a predetermined size, a detection signal based on the flaw will be detected through both the first detection coil 222 and the second detection coil 232.

Therefore, if the signal strength Sc of the first detection signal S1 and the signal strength Sc of the second detection signal S2 are equal to or greater than the threshold value Th (YES in S130), the notification unit 364 notifies that a flaw has been detected or that the noise is due to lift-off between the contact surface 214 and the object 10 to be detected.

When the first notification step S140 is performed, the inspection technician checks for any visible defects. If the inspection technician does not find any defects, the current application step S110 through the first determination step S130 can be repeated again.

Once the inspection technician has finished checking for flaws, the technician moves the probe 110 and repeats the process from current application step S110.

[Second determination step S150]
The determination unit 362 determines whether the signal strength Sc of the first detection signal S1 is equal to or greater than a threshold value Th, or whether the signal strength Sc of the second detection signal S2 is equal to or greater than a threshold value Th.

If the determination unit 362 determines that either the signal strength Sc of the first detection signal S1 or the signal strength Sc of the second detection signal S2 is equal to or greater than the threshold value Th (YES in S150), the determination unit 362 proceeds to the second notification step S160. On the other hand, if the determination unit 362 determines that the signal strength Sc of the first detection signal S1 or the signal strength Sc of the second detection signal S2 is not equal to or greater than the threshold value Th (NO in S150), the determination unit 362 proceeds to the third determination step S170.

[Second notification step S160]
The notification unit 364 causes the display device 380 to display a message indicating that a flaw has been detected.

As described above, the distance between the first detection coil 222 and the object 10 to be detected is substantially equal to the distance between the second detection coil 232 and the object 10 to be detected, so the lift-off signal is detected through both the first detection coil 222 and the second detection coil 232.

However, detection signals based on flaws smaller than a predetermined size will be detected through either the first detection coil 222 or the second detection coil 232.

For this reason, the notification unit 364 notifies that a flaw has been detected when it determines that either the signal strength Sc of the first detection signal S1 or the signal strength Sc of the second detection signal S2 is equal to or greater than the threshold value Th (YES in S150). In addition, the notification unit 364 notifies that a flaw has been detected when it determines that the difference between the signal strength Sc of the first detection signal S1 and the signal strength Sc of the second detection signal S2 is equal to or greater than a predetermined value (YES in the third determination step S170 described below).

This allows the notification unit 364 to notify of flaws with high accuracy.

Then, the inspection engineer moves the probe 110 and repeats the process from the current application step S110.
[Third determination step S170]
The determination unit 362 determines whether the difference between the signal strength Sc of the first detection signal S1 and the signal strength Sc of the second detection signal S2 is equal to or greater than a predetermined value.

If the determination unit 362 determines that the difference between the signal strength Sc of the first detection signal S1 and the signal strength Sc of the second detection signal S2 is equal to or greater than a predetermined value (YES in S170), the determination unit 362 proceeds to the second notification step S160. On the other hand, if the determination unit 362 determines that the difference between the signal strength Sc of the first detection signal S1 and the signal strength Sc of the second detection signal S2 is not equal to or greater than the predetermined value (NO in S170), the determination unit 362 proceeds to the third notification step S180.

[Third notification step S180]
The notification unit 364 causes the display device 380 to display a message indicating that the device is "healthy (no flaws)."

Then, the inspection technician moves the probe 110 and repeats the process from the current application step S110.

As described above, the eddy current flaw detector 100 according to this embodiment is equipped with a first detection coil 222 and a second detection coil 232. This allows the eddy current flaw detector 100 to detect flaws in various directions and depths simply by scanning the probe 110 along the object 10 (support 20) to be detected, without changing the angle of the probe 110. This makes it possible to detect flaws regardless of the skill level of the inspection technician, preventing flaws from being overlooked.

Although the embodiments have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to the above-described embodiments. It is clear that a person skilled in the art could conceive of various modifications or alterations within the scope of the claims, and it is understood that these naturally fall within the technical scope of the present disclosure.

For example, in the above-described embodiment, the probe 110 includes the first detector coil 222 and the second detector coil 232. However, the probe 110 may include three or more detector coils. For example, the probe 110 may include a first detector coil, a second detector coil, and a third detector coil. In this case, the central axis of the first detector coil is perpendicular to the contact surface 214. The angle between the central axis of the first detector coil and the central axis of the second detector coil is, for example, 45°, and the angle between the central axis of the first detector coil and the central axis of the third detector coil is, for example, 90°. Furthermore, the angle between the central axis of the first detector coil and the central axis of the second detector coil is, for example, 30°, and the angle between the central axis of the first detector coil and the central axis of the third detector coil is, for example, 60°.

Furthermore, in the above embodiment, an example was given in which the first excitation coil 224 and the second excitation coil 234 were provided. However, there is no limit to the number of excitation coils. For example, the probe 110 may be provided with one excitation coil, or may be provided with three or more excitation coils.

Furthermore, in the above embodiment, an example was given in which the central axis of the first detection coil 222 is perpendicular to the contact surface 214 (angle α is 90°). However, the central axis of the first detection coil 222 may be approximately perpendicular to the contact surface 214. "Approximately perpendicular" means that the angle α between the central axis of the first detection coil 222 and the contact surface 214 is within the range of 90°±1°, that is, in the range of 89° to 91°.

Furthermore, in the above embodiment, an example was given in which the threshold value Th of the signal strength Sc of the first detection signal S1 and the threshold value Th of the signal strength Sc of the second detection signal S2 are equal. However, the threshold value Th of the signal strength Sc of the first detection signal S1 and the threshold value Th of the signal strength Sc of the second detection signal S2 may be different.

In the above embodiment, a steel bridge was used as an example of the object 10 to be inspected. However, the object 10 to be inspected only needs to include at least the first plate 22, the second plate 24, and the weld 26. In other words, the object 10 to be inspected may have a corner weld such as a T-joint. The object 10 to be inspected may be, for example, the wall surface of a steel bridge or a plant.

This disclosure can contribute, for example, to Goal 12 of the Sustainable Development Goals (SDGs), "Ensure sustainable consumption and production patterns."

10 Object to be inspected 100 Eddy current flaw detector 210 Probe body 214 Contact surface 222 First detection coil 224 First excitation coil (excitation coil)
232 Second detection coil 234 Second excitation coil (excitation coil)
310 Excitation unit 330 Detection unit

Claims (4)

a probe body having a contact surface with the object to be detected, the contact surface being formed by joining a first plate and a second plate by a weld ;
an excitation coil provided in the probe body;
a first detection coil provided in the probe body, the first detection coil having a central axis substantially perpendicular to the contact surface;
a second detection coil provided in the probe body and having a central axis that forms an acute angle with the central axis of the first detection coil;
an excitation unit that applies an AC current to the excitation coil and generates an induced current in the object to be detected by electromagnetic induction;
a detection unit that detects a second detection signal based on the induced current through the second detection coil while detecting a first detection signal based on the induced current through the first detection coil;
Equipped with
An eddy current flaw detection device configured to be able to detect flaws that may occur in the object to be detected and that extend in a first direction, and flaws that extend in a second direction different from the first direction. The eddy current flaw detector of claim 1, wherein the first detection coil and the second detection coil are disposed between the excitation coil and the contact surface. The eddy current flaw detector according to claim 1 or 2, wherein the second detection coil has a central axis that forms an angle of 35° or more and 55° or less with the central axis of the first detection coil. A flaw detection method using an eddy current flaw detection device comprising: a probe body having a contact surface with an object to be detected, which is formed by joining a first plate and a second plate by a weld ; an excitation coil provided in the probe body; a first detection coil provided in the probe body, the central axis of which is approximately perpendicular to the contact surface; and a second detection coil provided in the probe body, the second detection coil having a central axis which forms an acute angle with the central axis of the first detection coil, the flaw detection method being capable of detecting flaws that may occur in the object to be detected and extend in a first direction and flaws that extend in a second direction different from the first direction ,
applying an alternating current to the excitation coil to generate an induced current in the object to be detected by electromagnetic induction;
detecting a second detection signal based on the induced current through the second detection coil while detecting a first detection signal based on the induced current through the first detection coil;
a step of notifying that there is a flaw when a difference between the signal strength of the first detection signal and the signal strength of the second detection signal is equal to or greater than a predetermined value;
A flaw detection method comprising: