Flaw detection device

Abstract

To detect a flaw in a steel plate deck from a pavement body side.SOLUTION: A flaw detection device comprises: an excitation coil 132; an excitation unit 210 that applies AC current to the excitation coil 132 to generate induction current in a steel plate deck through electromagnetic induction; a detection unit 230 that detects a detection signal based on the electromagnetic induction; an electromagnetic wave transmission and reception unit 250 that includes a transmission unit transmitting an electromagnetic wave and a reception unit receiving a reflected wave based on the transmitted electromagnetic wave; a distance calculation unit 262 that calculates the distance from the steel plate deck on the basis of the reflected wave; and a comparison unit 264 that compares the detection signal with a threshold based on the distance calculated by the distance calculation unit 262.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a flaw detection device. [Background technology]

[0002] Highways, bridges, and other roads are made up of steel decks and a pavement such as asphalt laminated on top of the steel decks. The steel decks can develop cracks and other imperfections due to fatigue caused by vehicles passing over the pavement over time.

[0003] Therefore, ultrasonic flaw detection is used as a technique for inspecting defects in steel decks (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-14513 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the ultrasonic flaw detection method described in Patent Document 1 requires that the probe be in contact with the steel deck, i.e., directly underneath the road. This necessitates the erection of scaffolding or the like underneath the road, which poses the problem of enormous costs for flaw inspection.

[0006] In view of these problems, the present disclosure aims to provide a flaw detector capable of detecting flaws in steel decks from the pavement side. [Means for solving the problem]

[0007] In order to solve the above problem, a flaw detection device according to one aspect of the present disclosure includes: No. 1 An excitation coil; a second excitation coil arranged adjacent to the first excitation coil, connected in series to the first excitation coil, and having a winding direction opposite to that of the first excitation coil; Excitation coil and the second excitation coil an excitation unit that applies an AC current to the steel deck and generates an induced current in the steel deck by electromagnetic induction; a detection coil superimposed on adjacent portions of the first excitation coil and the second excitation coil; The electromagnetic wave transmitting / receiving unit includes a detecting unit that detects a detection signal based on an induced current, a transmitting unit that transmits electromagnetic waves, and a receiving unit that receives reflected waves based on the transmitted electromagnetic waves, a distance calculating unit that calculates the distance to the steel deck based on the reflected waves, and a comparing unit that compares the detection signal with a threshold value based on the distance calculated by the distance calculating unit.

[0008] The comparison unit may also convert the flaw component contained in the detection signal based on the initial phase of the lift-off component contained in the detection signal, and compare the converted flaw component with a threshold value.

[0009] The transmitting unit of the electromagnetic wave transmitting and receiving unit is No. 1 Excitation coil and the second excitation coil The electromagnetic wave is transmitted through the receiving section of the electromagnetic wave transmitting and receiving section. No. 1 Excitation coil and the second excitation coil The reflected wave may be received through [Effects of the Invention]

[0010] According to the present disclosure, it is possible to detect defects in steel decks from the pavement side. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a road that is a target of flaw detection by a flaw detector according to an embodiment. [Figure 2] FIG. 2 is a view of a vehicle that constitutes the flaw detector according to the embodiment, viewed from vertically below. [Figure 3] FIG. 3 is a first diagram illustrating the electromagnetic induction flaw detection method. [Figure 4] FIG. 4 is a second diagram illustrating the electromagnetic induction flaw detection method. [Figure 5] FIG. 5 is a top view of the probe according to the embodiment. [Figure 6] FIG. 6 is a first side view of the probe according to the embodiment. [Figure 7] FIG. 7 is a second side view of the probe according to the embodiment. [Figure 8] FIG. 8 is a functional block diagram of the flaw detector according to the embodiment. [Figure 9] FIG. 9 is a diagram illustrating a detection signal when the distance between the probe and the steel deck is 0 and there is no flaw. [Figure 10] FIG. 10 is a diagram illustrating a detection signal when the distance between the probe and the steel deck is 0 and there is a flaw. [Figure 11] FIG. 11 is a diagram illustrating a detection signal when the distance between the probe and the steel deck is greater than 0 and there is no flaw. [Figure 12] FIG. 12 is a diagram illustrating a detection signal when the distance between the probe and the steel deck is greater than 0 and there is a flaw. [Figure 13] FIG. 13 is a diagram for explaining the converted detection signal when there is a flaw. [Figure 14] FIG. 14 is a diagram illustrating the calibration curve. [Figure 15] FIG. 15 is a flowchart showing a processing flow of the flaw detection method according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. 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.

[0013] Fig. 1 is a diagram illustrating a road 10 that is the target of flaw detection by a flaw detection device 100 according to this embodiment. In Fig. 1 of this embodiment, and Figs. 2 and 5 to 7 described below, the X axis (horizontal direction, road width direction), Y axis (horizontal direction, road length direction), and Z axis (vertical direction) that intersect perpendicularly are defined as shown in the figure.

[0014] As shown in FIG. 1, a road 10 is composed of a steel deck 20 and a pavement 30. The steel deck 20 is a deck made of steel members. The steel deck 20 supports the vertical downward load of vehicles. The steel deck 20 includes a deck plate 40, a main girder web 42, vertical reinforcement members 44, cross ribs 46, and U-ribs 48.

[0015] The deck plate 40 is a steel plate that extends in a substantially horizontal direction. The main girder web 42 is a steel plate that stands vertically downward from the deck plate 40 and extends in the extension direction of the road 10. The vertical reinforcing steel members 44 are steel plates that are attached to the main girder web 42. The upper surfaces of the vertical reinforcing steel members 44 are welded to the deck plate 40. The transverse ribs 46 are steel plates that stand vertically downward from the deck plate 40 and extend in the width direction of the road 10. The transverse ribs 46 are connected to the main girder web 42. The U-ribs 48 are steel plates that have a U-shaped vertical cross section. The U-ribs 48 are welded to the deck plate 40 so as to extend in the extension direction of the road 10 (road length direction).

[0016] The pavement 30 is layered on the deck plate 40. The pavement 30 is made of asphalt or the like.

[0017] Fatigue caused by vehicles passing over the pavement 30 over time can cause cracks and other defects in the welds between the deck plate 40 and the U-ribs 48, and the welds between the deck plate 40 and the vertical reinforcing members 44, etc., in the steel deck 20. The cracks propagate from the welds toward the deck plate 40.

[0018] Therefore, the flaw detector 100 shown in Fig. 2 below inspects the presence or absence of flaws in the steel deck 20 from above the pavement 30. In this embodiment, the flaw detector 100 inspects the presence or absence of flaws while scanning the road 10 in the direction in which the vehicle passes (the Y-axis direction in Fig. 1, the extension direction of the road 10, i.e., the extension direction of the U-rib 48).

[0019] [Flaw detection equipment 100] FIG. 2 is a view of a vehicle 110 constituting the flaw detector 100 according to this embodiment, viewed from vertically below.

[0020] As shown in FIG. 2, the flaw detector 100 includes a vehicle 110, an antenna 120, a probe 130, an encoder 140, a marking mechanism 150, and a control unit 200.

[0021] The vehicle 110 runs (moves) on the pavement 30 when inspecting the steel deck 20 for defects. An antenna 120, a probe 130, an encoder 140, and a marking mechanism 150 are integrally fixed to the underside 112 of the vehicle 110. In this embodiment, the antenna 120, the probe 130, the encoder 140, and the marking mechanism 150 are provided in this order from the front in the traveling direction of the vehicle. A control unit 200 is provided inside the vehicle 110.

[0022] The antenna 120 transmits electromagnetic waves based on a current applied from the electromagnetic wave transmitting / receiving unit 250 (described later), and receives reflected waves based on the transmitted electromagnetic waves. The electromagnetic waves pass through the pavement 30 (e.g., asphalt). Therefore, the electromagnetic waves are reflected by the steel deck 20. The antenna 120 is, for example, a Vivaldi antenna, a quadric horn antenna, or a bowtie antenna.

[0023] The probe 130 is a probe for electromagnetic induction testing (EMIT), which is a type of testing method also known as eddy current testing.

[0024] Fig. 3 is a first diagram illustrating the electromagnetic induction flaw detection method. Fig. 4 is a second diagram illustrating the electromagnetic induction flaw detection method. Figs. 3 and 4 show an example in which excitation and detection are performed by the same coil C.

[0025] As shown in Figure 3, when an AC current is applied to coil C, an AC magnetic field is generated (excitation). Then, due to electromagnetic induction, an induced current (eddy current U) is generated in the steel deck 20 in a direction that cancels out the AC magnetic field.

[0026] As shown in Fig. 4, the eddy current U is interrupted by the flaw at the location of the flaw in the steel deck 20. As a result, the eddy current U is disturbed at the location of the flaw compared to the location without the flaw.

[0027] Therefore, in the electromagnetic induction flaw detection method, the presence or absence of a flaw is detected by detecting the amount of change in the eddy current U acquired through the coil C as a change in impedance.

[0028] Fig. 5 is a top view of the probe 130 according to this embodiment. Fig. 6 is a first side view of the probe 130 according to this embodiment. Fig. 7 is a second side view of the probe 130 according to this embodiment.

[0029] As shown in FIGS. 5 to 7, the probe 130 includes an excitation coil 132 and a detection coil 134.

[0030] In this embodiment, the excitation coil 132 includes a first excitation coil 132a and a second excitation coil 132b.

[0031] The first excitation coil 132a and the second excitation coil 132b are arranged side by side and close to each other in a substantially horizontal direction (the Y-axis direction in FIGS. 5 to 7). The second excitation coil 132b has a central axis that is substantially parallel to the central axis of the first excitation coil 132a. The second excitation coil 132b has a winding direction opposite to that of the first excitation coil 132a. For example, in FIG. 5, when the winding direction of the first excitation coil 132a is clockwise, the winding direction of the second excitation coil 132b is counterclockwise. The second excitation coil 132b is connected in series to the first excitation coil 132a.

[0032] The first excitation coil 132a and the second excitation coil 132b are installed on the pavement 30 so that the central axis is approximately parallel to the perpendicular direction (Z-axis direction in Figures 5 to 7) of the surface of the pavement 30 layered on the steel deck 20.

[0033] The detection coil 134 is superimposed on the first excitation coil 132a and the second excitation coil 132b at a different position in the direction of the central axes of the first excitation coil 132a and the second excitation coil 132b (the Z-axis direction in FIGS. 5 to 7). In this embodiment, the detection coil 134 is superimposed on adjacent portions of the first excitation coil 132a and the second excitation coil 132b. The detection coil 134 has a central axis that is approximately parallel to the central axes of the first excitation coil 132a and the second excitation coil 132b.

[0034] 2, the encoder 140 acquires path information indicating the distance of the path traveled by the probe 130. The path information acquired by the encoder 140 is output to the control unit 200.

[0035] The marking mechanism 150 marks the pavement 30 in response to a control command from the control unit 200. The marking mechanism 150 includes, for example, a choke and an actuator that drives the choke.

[0036] 8 is a functional block diagram of the flaw detection device 100 according to this embodiment. As shown in Fig. 8, the control unit 200 includes an excitation unit 210, a detection unit 230, an A / D converter 240, an electromagnetic wave transmission / reception unit 250, a central control unit 260, a memory 270, and a display device 280.

[0037] The excitation unit 210 applies an alternating current to the first excitation coil 132a and the second excitation coil 132b, and generates an induced current in the steel deck 20 by electromagnetic induction. In this embodiment, the excitation unit 210 includes a function generator 212 and an amplifier 214.

[0038] The function generator 212 (shown as "F / G" in FIG. 8) generates an AC signal of a predetermined frequency. The AC signal from the function generator 212 is output to the amplifier 214 and the detection unit 230.

[0039] The amplifier 214 (denoted by "B / P" in FIG. 8) amplifies the AC signal from the function generator 212 and applies AC current to the first excitation coil 132a and the second excitation coil 132b. This generates an induced current in the steel deck 20 due to electromagnetic induction. As described above, the winding direction of the first excitation coil 132a and the winding direction of the second excitation coil 132b are opposite, so current is applied in the same direction in the adjacent portions of the first excitation coil 132a and the second excitation coil 132b. The amplifier 214 is, for example, a bipolar power supply.

[0040] The detection unit 230 is configured with, for example, a lock-in amplifier (indicated by "L / I" in FIG. 8). The detection unit 230 extracts the frequency component of the current applied to the first excitation coil 132a and the second excitation coil 132b (detection signal based on induced current) from the AC voltage detected by the detection coil 134 based on the AC signal (reference signal) output from the function generator 212.

[0041] The A / D converter 240 (denoted by "A / D" in FIG. 8) converts the output value (analog signal) of the detection unit 230 into a digital signal.

[0042] The electromagnetic wave transmitting / receiving unit 250 is configured, for example, by a frequency analysis device (indicated by "N / A" in FIG. 8). The electromagnetic wave transmitting / receiving unit 250 functions as a transmitting unit that applies a current to the antenna 120 and transmits electromagnetic waves to the surface of the pavement 30 via the antenna 120. The electromagnetic wave transmitting / receiving unit 250 also functions as a receiving unit that receives, via the antenna 120, reflected waves (reflected electromagnetic waves) reflected by the steel deck 20. The electromagnetic wave transmitting / receiving unit 250 then analyzes signals based on the reflected waves and calculates the frequency components (spectrum) of the reflected waves.

[0043] The central control unit 260 is configured by a semiconductor integrated circuit including a CPU (Central Processing Unit). The central control unit 260 reads programs and parameters for operating the CPU from the ROM. The central control unit 260 manages and controls the entire flaw detection device 100 in cooperation with RAM as a work area and other electronic circuits.

[0044] The memory 270 is composed of a ROM, a RAM, a flash memory, a HDD, etc. The memory 270 stores programs and various data used by the central control unit 260. In this embodiment, the memory 270 stores a calibration curve, which will be described later.

[0045] The display device 280 is configured with a liquid crystal display, an organic EL (Electro Luminescence) display, or the like.

[0046] In this embodiment, the central control unit 260 functions as a distance calculation unit 262 , a comparison unit 264 , and a signal storage unit 266 .

[0047] The distance calculation unit 262 calculates the distance between the probe 130 and the steel deck 20 based on the time of the peak in the spectrum calculated by the electromagnetic wave transmitting and receiving unit 250.

[0048] The comparison unit 264 first removes the lift-off signal from the detection signal obtained by the detection unit 230. The lift-off signal is noise based on the distance between the probe 130 and the steel deck 20.

[0049] Specifically, the detection signal based on the induced current obtained by the detection unit 230 is a flaw signal (alternating magnetic field change) S F and a lift-off signal S based on the distance between the probe 130 and the steel deck 20. L Includes:

[0050] Damage signal S F is expressed by the following equation (1): L is expressed by the following formula (2). S F =A F exp(iωt) …Equation (1) S L =A L exp(iφ) …Equation (2) In the above formula (1), A Fdenotes the amplitude of the flaw signal; i denotes a complex constant; ω denotes frequency; and t denotes time. In the above formula (2), A L denotes the amplitude of the lift-off signal; i denotes a complex constant; φ denotes the initial phase.

[0051] When the flaw detector 100 scans the road 10 (the vehicle 110 moves along the road 10), one or more wheels 114 of the vehicle 110 may get stuck in a depression, such as a rut, in the pavement 30 or ride over a protrusion in the pavement 30, causing the distance between the underside 112 of the vehicle 110 and the surface of the pavement 30, i.e., the distance between the probe 130 and the surface of the pavement 30, to fluctuate. In this case, even if the thickness of the pavement 30 is constant, the distance between the surface of the pavement 30 and the probe 130 fluctuates, causing the distance between the probe 130 and the steel deck 20 to fluctuate. Furthermore, if the thickness of the pavement 30 fluctuates due to scraping of the pavement 30 by the vehicle traveling or an increase in the thickness of the pavement 30 due to repairs to the pavement 30, the distance between the probe 130 and the steel deck 20 will fluctuate, even if the distance between the surface of the pavement 30 and the probe 130 is constant.

[0052] Damage signal S F is the lift-off signal S L However, as the distance between the probe 130 and the steel deck 20 increases, the amplitude A F The signal is reduced from the detection signal to the flaw signal S F It becomes impossible to identify the

[0053] Fig. 9 is a diagram illustrating a detection signal when the distance between the probe 130 and the steel deck 20 is 0 and there is no flaw. Fig. 10 is a diagram illustrating a detection signal when the distance between the probe 130 and the steel deck 20 is 0 and there is a flaw. Fig. 11 is a diagram illustrating a detection signal when the distance between the probe 130 and the steel deck 20 is more than 0 and there is no flaw. Fig. 12 is a diagram illustrating a detection signal when the distance between the probe 130 and the steel deck 20 is more than 0 and there is a flaw.

[0054] In the flaw detection device 100, the lift-off signal S L is smallest, an adjustment (origin correction) is performed so that the reference point of the Lissajous waveform is the origin (0,0). Then, after the origin correction, flaw detection is performed using the flaw detection device 100. Therefore, as shown in Figures 9 and 10, when the distance between the probe 130 and the steel deck 20 is 0 (zero), the reference point of the Lissajous waveform is the origin (0,0). The Lissajous waveform indicates fluctuations in the sine component (amplitude, vertical axis in Figures 9 to 12) and cosine component (phase, horizontal axis in Figures 9 to 12) of the detection signal with respect to the excitation voltage. In other words, when the distance between the probe 130 and the steel deck 20 is 0, the sine component and cosine component of the detection signal fluctuate with the origin as the reference point in the Lissajous waveform.

[0055] As shown in Fig. 9, when there is no flaw, the fluctuation range of the sine and cosine components of the detection signal is approximately zero. Also, as shown in Fig. 10, when there is a flaw, the fluctuation range of the sine and cosine components of the detection signal becomes larger than when there is no flaw.

[0056] On the other hand, as shown in Figures 11 and 12, when the distance between the probe 130 and the steel deck 20 is greater than 0, the reference point of the Lissajous waveform is a point other than the origin. For example, in the cases shown in Figures 11 and 12, the reference point is (2.0, 1.0).

[0057] In addition, as the distance between the probe 130 and the steel deck 20 increases, the reference point of the fluctuations in the sine and cosine components of the detection signal moves away from the origin (0, 0). For example, in the examples shown in FIGS. 9 to 12, as the distance between the probe 130 and the steel deck 20 increases, the reference point moves in the upper right direction from the origin (the lift-off signal S L (and in phase with each other).

[0058] Regardless of the distance between the probe 130 and the steel deck 20, when there is no flaw, the fluctuation range of the sine and cosine components of the detection signal is approximately zero, as shown in Figure 11. Furthermore, when there is a flaw, the fluctuation range of the sine and cosine components of the detection signal becomes larger than when there is no flaw, as shown in Figure 12.

[0059] The defect evaluation is performed based on the fluctuation width of the sine component of the detection signal. L When it is included, the flaw signal S F The fluctuation range of the sine component becomes unclear.

[0060] Therefore, the comparison unit 264 compares the flaw signal S included in the detection signal with the F (flaw component) is detected by the lift-off signal S L The transformation is based on the initial phase φ (of the lift-off component).

[0061] As mentioned above, the flaw signal S F and lift-off signal S L are based on different phenomena. F and lift-off signal S L have different phases ("ωt" in the above formula (1) and "φ" in the above formula (2)).

[0062] Therefore, in this embodiment, the comparison unit 264 uses the lift-off signal S L The detection signal is converted so that the phase angle of the lift-off signal S becomes 0. L The sine component of the converted flaw signal S F ' can be expressed by the following formula (3). S F ´=A F exp{i(ωt-φ)} ...Equation (3)

[0063] 13 is a diagram illustrating the converted detection signal when there is a flaw. In the converted detection signal, the lift-off signal S L The sine component of the flaw signal SF The sin component of ´ is A F sin(ωt-φ). Therefore, the flaw signal S F The fluctuation range of the sine component of the signal can be clearly identified, and flaws can be evaluated with high accuracy. In other words, by calculating the signal strength Sc of the converted detection signal, flaws can be evaluated with high accuracy. The signal strength Sc of the converted detection signal is calculated by dividing the value (2×A F sin(ωt-φ)).

[0064] Then, the comparison unit 264 refers to the calibration curve stored in the memory 270 and determines a threshold value from the distance between the probe 130 and the steel deck 20 calculated by the distance calculation unit 262.

[0065] Fig. 14 is a diagram illustrating a calibration curve 300. As shown in Fig. 14, the calibration curve 300 is a curve that correlates the signal intensity Sc at which a flaw is determined to exist with the distance (lift-off) [mm] between the probe 130 and the steel deck 20. The calibration curve 300 is created in advance by detecting flaws in a test piece on which a predetermined flaw has been formed using the flaw detection device 100. As shown in Fig. 14, in the calibration curve 300, the signal intensity Sc decreases as the distance between the probe 130 and the steel deck 20 increases.

[0066] The comparison unit 264 refers to the calibration curve 300 and determines the threshold value from the distance between the probe 130 and the steel deck 20 calculated by the distance calculation unit 262. For example, if the distance between the probe 130 and the steel deck 20 is 80 mm, the threshold value is determined to be 0.36. Also, if the distance between the probe 130 and the steel deck 20 is 50 mm, the threshold value is determined to be 17.3.

[0067] The comparison unit 264 then compares the determined threshold value with the converted signal strength Sc (the sine component of the converted flaw component). If the comparison unit 264 determines that the signal strength Sc is equal to or greater than the threshold value, it determines that a flaw exists. The comparison unit 264 then drives the marking mechanism 150 to apply a mark to the pavement 30.

[0068] On the other hand, if it is determined that the signal strength Sc is less than the threshold value, the comparison unit 264 determines that there is no flaw.

[0069] The signal storage unit 266 stores the detection signal and the distance between the probe 130 and the steel deck 20 in the memory 270 in association with the path information acquired by the encoder 140 .

[0070] [Flaw detection method] Next, a flaw detection method for detecting flaws in the road 10 using the flaw detection device 100 will be described. Fig. 15 is a flowchart showing the processing flow of the flaw detection method according to this embodiment. As shown in Fig. 15, the flaw detection method according to this embodiment includes an end determination step S110, a signal acquisition step S120, a signal conversion step S130, a distance calculation step S140, a threshold determination step S150, a comparison step S160, a marking step S170, a saving step S180, and a moving step S190. Each step will be described below.

[0071] [End determination step S110] The central control unit 260 determines whether scanning of the predetermined flaw detection range has been completed. As a result, if it is determined that scanning of the flaw detection range has not been completed (NO in S110), the central control unit 260 proceeds to the signal acquisition step S120. On the other hand, if it is determined that scanning of the flaw detection range has been completed (YES in S110), the central control unit 260 ends the flaw detection method.

[0072] [Signal acquisition step S120] The excitation unit 210 applies an AC current to the first excitation coil 132a and the second excitation coil 132b. The detection unit 230 acquires a detection signal through the detection coil 134, and the A / D converter 240 converts the detection signal into a digital signal.

[0073] The electromagnetic wave transmitting / receiving unit 250 applies a current to the antenna 120 and transmits electromagnetic waves to the surface of the pavement 30 through the antenna 120. The electromagnetic wave transmitting / receiving unit 250 then receives, through the antenna 120, the waves reflected by the steel deck 20. The electromagnetic wave transmitting / receiving unit 250 analyzes the signal based on the reflected waves and calculates the spectrum.

[0074] The encoder 140 also acquires path information and outputs it to the control unit 200 .

[0075] [Signal conversion step S130] The comparison unit 264 compares the flaw signal S included in the detection signal acquired in the signal acquisition step S120. F is the lift-off signal S included in the detection signal. L is transformed based on the initial phase φ of

[0076] [Distance calculation step S140] The distance calculation unit 262 calculates the distance between the probe 130 and the steel deck 20 based on the spectrum acquired in the signal acquisition step S120.

[0077] [Threshold determination step S150] The comparison unit 264 refers to the calibration curve 300 stored in the memory 270 and determines a threshold value from the distance between the probe 130 and the steel deck 20 calculated in the distance calculation step S140.

[0078] [Comparison process S160] The comparison unit 264 determines whether the signal strength Sc of the detection signal converted in the signal conversion step S130 is equal to or greater than the threshold determined in the threshold determination step S150. As a result, if it is determined that the signal strength Sc is equal to or greater than the threshold (YES in S160), the comparison unit 264 proceeds to the marking step S170. On the other hand, if it is determined that the signal strength Sc is not equal to or greater than the threshold (NO in S160), that is, if it is determined that the signal strength Sc is less than the threshold, the comparison unit 264 proceeds to the saving step S180.

[0079] [Marking process S170] The comparison unit 264 drives the marking mechanism 150 to apply a mark to the pavement 30.

[0080] [Preservation process S180] The signal storage unit 266 stores the detection signal and the distance between the probe 130 and the steel deck 20 in the memory 270 in association with the path information acquired by the encoder 140 .

[0081] [Moving process S190] The vehicle 110 constituting the flaw detection device 100 moves from the first position where the signal acquisition step S120 was executed this time to the second position within a predetermined time. The second position is a position in the moving direction of the vehicle 110 (the Y-axis direction in FIG. 2) that is different from the first position.

[0082] As described above, the flaw detector 100 according to this embodiment includes the antenna 120, the probe 130, and the control unit 200. Therefore, the flaw detector 100 according to this embodiment can detect flaws in the steel deck 20 from the pavement 30 side.

[0083] As described above, the comparison unit 264 converts the flaw component contained in the detection signal based on the initial phase of the lift-off component contained in the detection signal, thereby enabling the comparison unit 264 to selectively extract the flaw component (signal caused by the flaw) from the detection signal.

[0084] Furthermore, as described above, the comparison unit 264 compares the signal strength Sc with a threshold value based on the distance between the probe 130 and the steel deck 20. This allows the comparison unit 264 to detect flaws with high accuracy.

[0085] As described above, the flaw detector 100 according to this embodiment is provided with the marking mechanism 150. This allows the user to visually grasp the position of a flaw.

[0086] As described above, the flaw detection method using the flaw detection device 100 repeats the steps from the end determination step S110 to the movement step S190. That is, the flaw detection device 100 detects the presence or absence of flaws in a time-division manner in accordance with the travel of the vehicle 110. This allows the flaw detection device 100 to comprehensively detect flaws in all areas on the road 10 where the vehicle 110 has traveled.

[0087] 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 can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0088] For example, in the above-described embodiment, the case where the excitation coil 132 includes the first excitation coil 132a and the second excitation coil 132b has been exemplified. However, there is no limit to the number of excitation coils 132 included in the probe 130. For example, the probe 130 may include one excitation coil 132, or three or more excitation coils 132. Similarly, the probe 130 may include multiple detection coils 134. Furthermore, the probe 130 may include a magnetic sensor instead of the detection coil 134.

[0089] In the above embodiment, the comparison unit 264 converts the flaw component included in the detection signal based on the initial phase of the lift-off component included in the detection signal. However, the comparison unit 264 does not have to convert the flaw component included in the detection signal based on the initial phase of the lift-off component included in the detection signal. In this case, the comparison unit 264 compares the detection signal obtained by the detection unit 230 with a threshold value.

[0090] In the above embodiment, the flaw detection device 100 is provided with the antenna 120. However, the flaw detection device 100 does not need to be provided with the antenna 120. In this case, the electromagnetic wave transmitting / receiving unit 250 may use the excitation coil 132 as a transmitter and a receiver instead of the antenna 120. In this case, it is preferable to make the frequency of the AC current applied by the excitation unit 210 different from the frequency of the AC current applied by the electromagnetic wave transmitting / receiving unit 250. This allows the flaw detection device 100 to omit the antenna 120 dedicated to calculating the distance to the steel deck 20.

[0091] In the above embodiment, the control unit 200 is provided in the vehicle 110. However, the control unit 200 may be provided in a location separate from the vehicle 110.

[0092] This disclosure can contribute, for example, to Goal 12 of the Sustainable Development Goals (SDGs), "Ensure sustainable consumption and production patterns." [Explanation of symbols]

[0093] 100 Flaw detection equipment 132 Excitation coil 20 Steel deck slab 210 Excitation section 230 Detector 250 Electromagnetic wave transmitting and receiving unit 262 Distance calculation unit 264 Comparison Section

Claims

1. A first excitation coil; a second excitation coil arranged adjacent to and in parallel with the first excitation coil, connected in series to the first excitation coil, and having a winding direction opposite to that of the first excitation coil; an excitation unit that applies an alternating current to the first excitation coil and the second excitation coil to generate an induced current in the steel deck by electromagnetic induction; a detection unit having a detection coil superimposed on a portion adjacent to the first excitation coil and the second excitation coil, and detecting a detection signal based on the induced current; an electromagnetic wave transmitting / receiving unit including a transmitting unit that transmits electromagnetic waves and a receiving unit that receives reflected waves based on the transmitted electromagnetic waves; a distance calculation unit that calculates the distance to the steel deck based on the reflected wave; a comparison unit that compares the detection signal with a threshold value based on the distance calculated by the distance calculation unit; A flaw detection device comprising:

2. The comparison unit converting a flaw component included in the detection signal based on an initial phase of a lift-off component included in the detection signal; The flaw detection device according to claim 1 , wherein the converted flaw component is compared with the threshold value.

3. the transmitter of the electromagnetic wave transmitter-receiver transmits the electromagnetic wave through the first excitation coil and the second excitation coil; The flaw detection device according to claim 1 or 2, wherein the receiving section of the electromagnetic wave transmitting and receiving section receives the reflected wave through the first excitation coil and the second excitation coil.

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