JP5243828B2 - Eddy current flaw detection method and eddy current flaw detection sensor - Google Patents

Description

  The present invention relates to a non-contact type eddy current flaw detection method and an eddy current flaw detection sensor. More specifically, the present invention relates to an eddy current flaw detection method suitable for use in detecting damage such as cracks in a tubular inspection object comprising a magnetic member and a non-magnetic member. The present invention relates to a current flaw detection sensor.

  In an optical fiber composite ground wire (hereinafter referred to as OPGW), as time elapses from laying, cracks and through-holes in aluminum pipes that are members of OPGW due to, for example, strong wind vibration, corrosion, or freezing Or damage such as cracks may occur.

  As a conventional non-contact type eddy current flaw detection method for detecting damage of a tubular inspection object using eddy current by electromagnetic induction, for example, as shown in FIG. 12, the wiring of the excitation coil and the detection coil A flexible substrate 102 having wiring is wound around a pipe 108 and connectors 103a and 103b connected to both ends of these coils are attached to mounting members 107 fixed to flanges 106 at both ends of a bobbin 105 passing through the pipe 108. There is a fixed substrate 104b to be attached and an eddy current flaw detection coil element 101 fixed to the fixed substrate 104a to measure an electric signal to detect a pipe 108 (Patent Document 1).

Japanese Patent No. 3247666

  However, in the eddy current flaw detection method disclosed in Patent Document 1, the detection of damage occurring in the pipe 108 without special processing of the detection signal obtained using the eddy current flaw detection coil element 101 having the above-described configuration. Therefore, especially when the inspection object has a complicated structure such as OPGW, the detection signal obtained from the coil element 101 includes noise, and a measurement error is likely to occur. There is a problem that it may not be possible with sufficient accuracy.

  Therefore, the present invention provides a vortex capable of detecting damage in a tubular inspection object formed by bundling a magnetic member such as a steel wire and a nonmagnetic member such as an aluminum tube with high accuracy, for example, OPGW. An object is to provide a current flaw detection method.

In order to achieve this object, the eddy current flaw detection method according to claim 1 is characterized in that the detection signal is set so that the detection signal accompanying the damage of the nonmagnetic member is in the Y-axis direction on the two-dimensional coordinate axis of the X signal-Y signal. The output coil is set outside the optical fiber composite ground wire as a tubular inspection object made of a steel wire as a magnetic member and an aluminum tube as a non-magnetic member after setting to rotate around the origin. And measuring the electrical signal of the optical fiber composite ground wire using the electromagnetic induction phenomenon with the flaw detection frequency set to 70 kHz using the output coil and the detection coil, and the detection signal X obtained by the measurement is wound. Al constituting the optical fiber composite overhead ground wire on the basis of the variations of the Y signal and detects a damage of the steel wire constituting the optical fiber composite overhead ground wire on the basis of the variation of the signal It is designed to detect damage to the microtubules .

  Therefore, according to this eddy current flaw detection method, damage to the magnetic member constituting the inspection object is detected based on the variation of the X signal of the detection signal, and at the same time, the non-magnetic material constituting the inspection object based on the variation of the Y signal. Since damage to the body member is detected, it is possible to accurately detect damage to the magnetic member or damage to the non-magnetic member in the tubular inspection object composed of the magnetic member and the non-magnetic member. it can.

According to a second aspect of the present invention, in the eddy current flaw detection method according to the first aspect, the distance between the outer peripheral surface of the optical fiber composite ground wire and the inner peripheral surface of the output coil and the detection coil is less than 5 mm. ing.

The eddy current flaw sensor according to claim 3 is an eddy current flaw sensor for measuring an electric signal of an inspection object using an electromagnetic induction phenomenon , wherein the steel wire and the non-magnetic member are magnetic members. The outer peripheral surface of the optical fiber composite ground wire , the output coil and the detection coil have an output coil and a detection coil wound around the outside of the optical fiber composite ground wire as a tubular inspection object made of an aluminum tube. Ri spacing 5mm below der of the inner peripheral surface of the coil, and to perform the measurement flaw detection frequency as 70 kHz.

  In this case, the weak signal generated from the damaged part of the non-magnetic member inside the inspection object can be detected without being buried by the strong signal from the surrounding magnetic member. It is possible to more accurately detect damage to the non-magnetic member and the magnetic member.

Further, the eddy current testing method of claim 4, wherein the outer peripheral surface and the light of the optical fiber composite overhead ground wire as inspection object tubular made of an aluminum tube which is a non-magnetic member and the steel wire is a magnetic member By using an eddy current sensor characterized in that the distance between the output coil wound around the fiber composite ground wire and the inner peripheral surface of the detection coil is less than 5 mm, the wire is wound outside the fiber composite ground wire. perform the measurement of the electrical signal for the optical fiber composite overhead ground wire using electromagnetic induction phenomenon flaw detection frequency using the output coil and the detection coil as a 70kHz wound, light based on the variation of the detection signal obtained by the measurement It is made possible to detect the damage of the aluminum pipe constituting the fiber composite overhead ground wire without being affected by the signal from the steel wire .

Furthermore, the eddy current flaw detection sensor according to claim 5 is an eddy current flaw detection sensor that measures an electric signal of an inspection object using an electromagnetic induction phenomenon, and is a steel wire that is a magnetic member and a non-magnetic member. The outer peripheral surface of the optical fiber composite ground wire , the output coil and the detection coil have an output coil and a detection coil wound around the outside of the optical fiber composite ground wire as a tubular inspection object made of an aluminum tube. By measuring the electrical signal of the optical fiber composite ground wire using the electromagnetic induction phenomenon with a flaw detection frequency of 70 kHz using the output coil and the detection coil by setting the distance from the inner peripheral surface of the coil to less than 5 mm damage of the aluminum tube constituting the optical fiber composite overhead ground wire as a detectable without being influenced by the signal from the steel wire on the basis of the variations of the resulting detection signal There.

  According to this eddy current flaw detection method and eddy current flaw detection sensor, a weak signal generated from a damaged portion of a non-magnetic member inside the inspection object is detected without being buried by a strong signal from the surrounding magnetic member. Damage to the non-magnetic member and magnetic member of the inspection object can be detected more accurately.

  According to the present invention, damage to a magnetic member or damage to a nonmagnetic member in a tubular inspection object made up of a magnetic member and a nonmagnetic member can be accurately detected, such as OPGW. Since it is possible to detect damage in a tubular inspection object, which is an inspection object comprising a magnetic member and a non-magnetic member, with high accuracy, the reliability of inspection for occurrence of damage is improved. be able to.

  Furthermore, according to the present invention, it is possible to detect the damage of the inspection object more accurately by reducing the noise of the detection signal obtained by the measurement. Improvements can be made.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

  1 and 2 show an example of an embodiment of the eddy current flaw detection method of the present invention. In this eddy current flaw detection method, an output coil and a detection coil are wound around a tubular inspection object made of a magnetic member and a non-magnetic member, and an inspection using an electromagnetic induction phenomenon is performed using the output coil and the detection coil. The measurement of the electrical signal of the object is performed, the damage of the magnetic member constituting the inspection object is detected based on the fluctuation of the X signal of the detection signal obtained by the measurement, and the inspection object is detected based on the fluctuation of the Y signal Damage to the non-magnetic member constituting the object is detected.

  In the present embodiment, the eddy current flaw detection sensor 1 shown in FIGS. 1 and 2 is used in the measurement of an electric signal using an electromagnetic induction phenomenon. As shown in FIGS. 1 and 2, the eddy current flaw detection sensor 1 is mainly composed of a cylindrical bobbin 2, a connection terminal fixing substrate 5, and a substrate fixing member 7.

  The bobbin 2 is formed in a cylindrical shape having a through hole 2a at the axial center position. The diameter of the through hole 2a is adjusted in accordance with the outer diameter of a tubular inspection object (not shown) on which the eddy current flaw detection sensor 1 measures an electric signal. The bobbin 2 is formed of a nonconductive material such as a synthetic resin such as polyacetal.

  Further, the bobbin 2 has two annular grooves 2d that make one turn in the circumferential direction on the peripheral wall near the center in the axial direction. Then, by forming the two grooves 2d and 2d, the partition 2b between the two grooves 2d and 2d is formed near the center in the axial direction of the bobbin 2, and the flange portions 2c are both end portions in the axial direction of the bobbin 2. Formed.

  An output coil (not shown) is wound around one groove 2d and a detection coil (not shown) is wound around the other groove 2d. Note that a flexible wiring board (also referred to as Flexible PWB) may be used as these coils or as an integrated body of these coils and bobbins.

  The eddy current flaw detection sensor 1 performs eddy current flaw detection using an output coil and a detection coil wound around the groove 2d with the partition 2b interposed therebetween. Therefore, the distance between the two grooves 2d and 2d and the width of the partition 2b are set within a range in which the two coils can operate as an output coil and a detection coil as an eddy current flaw detection sensor.

  Here, in the eddy current flaw detection sensor 1 of the present invention, the interval between the outer peripheral surface of the inspection object and the inner peripheral surface of these coils when the output coil and the detection coil are wound around the groove 2d is less than 10 mm. Is preferable, more preferably less than 5 mm, and most preferably less than 2 mm.

  Note that when the output coil and the detection coil are wound around the groove 2d of the bobbin 2, the inner peripheral surface of the coil coincides with the bottom surface of the groove 2d. Therefore, when the diameter of the through-hole 2a of the bobbin 2 is matched with the outer diameter of the inspection object, the distance between the outer peripheral surface of the inspection object and the inner peripheral surface of the output coil and the detection coil is the bobbin 2 at the bottom 2e of the groove 2d. It is determined by the thickness of the peripheral wall.

  In the present embodiment, the connection terminal fixing substrate 5 is formed in a rectangular plate shape that is shorter than the axial length of the bobbin 2, and is arranged with the longitudinal direction aligned with the axial direction of the bobbin 2.

  The two board fixing members 7 are attached to the flange portions 2c at both end portions of the bobbin 2 as a set, with the flange portions 2c sandwiched from both sides in the direction perpendicular to the axial direction of the bobbin 2. Therefore, the substrate fixing member 7 is an Ω type, and an Ω type concave portion 7a is formed in a semicircular curved surface, and the semicircular curved surface of the concave portion 7a is a shape of the peripheral surface of the flange portion 2c (specifically, the flange portion). 2c radius).

  The substrate fixing member 7 also has through holes 7c at both end portions 7b of the Ω-shaped recess 7a. Then, the concave portions 7a of the two board fixing members 7 face each other to sandwich the flange portion 2c, and the end portion 7b is tightened by the bolt 8a and the nut 8b that penetrate both through holes 7c of the opposite end portions 7b. Thus, the substrate fixing member 7 is fixed to the flange portion 2c.

  The connection terminal fixing substrate 5 has through holes 5c on both sides in the longitudinal direction of the rectangle. Then, the connection terminal fixing substrate 5 is fixed to the end portion of the substrate fixing member 7 with a bolt 8 a that fastens the end portion 7 b of the substrate fixing member 7 passing through the through hole 5 c. That is, when the board fixing member 7 faces each other and the flange portion 2c is sandwiched, the positions of the through holes 7c of the end 7b of the board fixing member 7 facing each other and the through holes 5c of the connection terminal fixing board 5 are matched to each other. 7, the connection terminal fixing substrate 5 is sandwiched between them, and the substrate fixing member 7 and the connection terminal fixing substrate 5 facing each other are bundled and fixed.

  A connection terminal 6a electrically connected to both ends of the output coil and a connection terminal 6b electrically connected to both ends of the detection coil are attached to the connection terminal fixing substrate 5. Then, in order to electrically connect the output coil and the connection terminal 6a, and the detection coil and the connection terminal 6b, the connection terminal fixing substrate 5 further includes a pair of two for connecting both ends of the output coil. A pair of connection holes 5b for connecting both ends of the connection hole 5a and the detection coil are provided, and between the connection hole 5a and the connection terminal 6a, and between the connection hole 5b and the connection terminal 6b. A lead 5d is provided.

  The connection terminal 6a that is electrically connected to both ends of the output coil is set with a display angle of the X signal and the Y signal (specifically, predetermined on the origin center on the two-dimensional coordinate axis of the X signal-Y signal). The output side cable from a commercially available single frequency type eddy current flaw detector capable of rotating the angle of the phaser (also referred to as a set angle of the phase shifter) is connected and output via the connection terminal 6a. An AC voltage is supplied to the coil. In addition, a wiring from the eddy current flaw detector is connected to the connection terminal 6b that is electrically connected to both ends of the detection coil, and is induced in the inspection object by the AC voltage supplied to the output coil and detected by the detection coil. The induced voltage is input to the eddy current flaw detector through the connection terminal 6b. The detection signal is specifically a voltage.

  In order to be able to detect the weak signal generated from the damaged part of the non-magnetic member inside the inspection object separately without being buried by the strong signal from the surrounding magnetic member, A test piece in which a non-magnetic member is previously damaged is inserted into the through-hole 2a of the bobbin 2 of the eddy current flaw detection sensor 1, balanced at a position where there is no damage (that is, set to 0 point), and then the test piece axial direction The detection signal (X signal and Y signal) accompanying the damage is obtained by moving the eddy current flaw detection sensor 1 along the line.

  On the two-dimensional coordinate axis of the X signal-Y signal, the display angle (set angle of the phase shifter) to be rotated around the origin is obtained so that the detection signal accompanying the damage of the nonmagnetic member is substantially in the Y axis direction. Keep it. If the device does not have a phaser display function, the base of the triangle is set to the value of the X signal (unit is V) and the height is set to the Y signal using the X signal and Y signal obtained as the detection signal of the damaged portion. The display angle to be rotated is obtained by subtracting the angle (the unit is V) from 90 degrees (Y-axis angle).

  Next, after setting the display angle to be rotated (set angle of the phase shifter) obtained in the previous section, the tubular inspection object is passed through the through hole 2a of the bobbin 2 of the eddy current flaw detection sensor 1. After balancing (ie, setting 0 point) at a position without damage, the eddy current flaw detection sensor 1 is induced in the inspection object by the AC voltage supplied to the output coil while moving in the axial direction of the inspection object. The induced voltage is detected by a detection coil.

  In the present invention, the output coil and the detection coil are wound around the outside of the tubular inspection object, and the X signal of the induced voltage detected by the detection coil is induced in the inspection object by the AC voltage supplied to the output coil. The damage of the magnetic member that constitutes the inspection object is detected based on the fluctuation of the Y, and the damage of the non-magnetic member that constitutes the inspection object is detected based on the fluctuation of the Y signal.

  Specifically, regarding the detection signal obtained by the measurement using the eddy current flaw detection sensor 1, if a change is observed in the X signal, it is determined that a magnetic member such as a steel pipe is damaged, and the Y signal In the case where fluctuation is observed, it is determined that the nonmagnetic member such as an aluminum tube is damaged.

  Note that the degree of variation of the X signal for determining that the inspection object is damaged is not limited to a specific standard, and may be set appropriately by the operator. Specifically, for example, when the voltage of the eddy current detected by the detection coil fluctuates more than 20% of the AC voltage supplied to the output coil, it is determined that the inspection object is damaged. Can be considered.

  Here, the eddy current flaw detection sensor 1 itself of the present embodiment does not measure the measurement position. Therefore, when the sensor is moved at a predetermined speed, when the detection signal data is recorded, the elapsed time from the start of measurement is recorded and the elapsed time from the start of measurement and the moving distance from the inspection start position By making these correspond, it is possible to specify the position of damage occurring on the inspection object.

  According to the eddy current flaw detection method of the present invention configured as described above, damage to the magnetic member constituting the inspection object is detected based on the variation of the X signal of the detection signal, and based on the variation of the Y signal. Since damage to the non-magnetic member constituting the inspection object is detected, damage to the magnetic member or damage to the non-magnetic member in the tubular inspection object comprising the magnetic member and the non-magnetic member Can be accurately detected.

  In addition, although the above-mentioned form is an example of the suitable form of this invention, it is not limited to this, A various deformation | transformation implementation is possible in the range which does not deviate from the summary of this invention. For example, by changing the display angle (setting angle of the phase shifter) provided in a commercially available eddy current flaw detector, the damage of the magnetic member can be evaluated with the Y signal, and the damage of the nonmagnetic member can be evaluated with the X signal. In the case where it is sufficient to detect and evaluate only the damage of the non-magnetic member without damage to the body member, the present invention also includes the evaluation based on only the amplitude instead of the X signal or Y signal.

Here, the amplitude is defined by Equation 1.
(Equation 1) Amplitude (V) = {(X signal value (V)) ² + (Y signal value (V)) ² } ^1/2

  That is, the amplitude indicates the distance from the origin in the X signal-Y signal diagram. When the X signal is 0, the amplitude indicates the height of the Y signal.

  An embodiment in which the eddy current flaw detection method of the present invention is applied to detection of actual OPGW damage will be described with reference to FIGS.

  FIG. 3 shows a cross section of the OPGW used as the inspection object in this example. The OPGW 10 includes an optical fiber housing aluminum tube 11 at the center and eight aluminum-clad steel wires 14 surrounding the optical fiber housing aluminum tube 11.

  The optical fiber housing aluminum tube 11 includes an aluminum tube 11a that is an outer peripheral wall, three optical fiber units 12 disposed inside the aluminum tube 11a, and the aluminum tube 11a of the three optical fiber units 12 inside. It consists of a grooved aluminum spacer 13 having three grooves 13a for fixing the position.

  The optical fiber unit 12 of this embodiment is a bundle of a central optical fiber and six surrounding optical fibers. The aluminum-clad steel wire 14 is obtained by coating aluminum around a steel wire.

  As described above, the OPGW 10 used as the inspection object in the present embodiment is composed of the magnetic member and the non-magnetic member, and is suitable for applying the present invention. In the actual maintenance and inspection of the OPGW, damage to the aluminum tube 11a at the center that cannot be clearly seen from the outside becomes a particular problem. Therefore, according to the present invention, the damage to the aluminum tube 11a of the OPGW is detected. Being able to do it properly is very beneficial for actual OPGW maintenance.

  In this example, damage was detected using the eddy current flaw detection sensor 1 shown in FIGS. In this example, the flaw detection frequency was 70 kHz, and the low-pass filter was 10 Hz. The setting of the display angle to be rotated on the two-dimensional coordinate axis of the X signal-Y signal (setting of the phase shifter) was 40 degrees.

Further, OPGW10 used in this example (OPGW-60 as the line type standard. 60 represents an area of 60 mm ² as a lightning protection ground wire, and is a total of the eight aluminum-clad steel wires 14 in FIG. The diameter of the through hole 2a of the bobbin 2 of the eddy current flaw detection sensor 1 was adjusted in accordance with the outer diameter of the OPGW 10.

  In this example, (1) the presence or absence of a difference in flaw detection performance due to a difference in damage mode was confirmed, and (2) the presence or absence of a difference in flaw detection performance due to a difference in sensor specifications was confirmed.

(1) Confirmation of presence or absence of difference in flaw detection performance due to difference in damage mode First, in order to confirm whether or not there is a difference in flaw detection performance of the eddy current flaw detection method of the present invention due to a difference in damage mode, the aluminum tube 11a of OPGW 10 is used. These damages were detected by artificially providing through-holes and axial cracks, or causing cracks by freezing due to actual natural phenomena. In addition, it measured using OPGW10 which confirmed that there was no damage other than the damage of the detection target of the aluminum pipe 11a.

  First, it measured using OPGW10 which has a through-hole (diameter 3mm) as damage to the aluminum tube 11a. A predetermined flaw detection frequency of 70 kHz, a low-pass filter of 10 Hz, a display angle to be rotated (phaser setting) of 40 degrees, and the OPGW 10 is passed through the through-hole 2a of the bobbin 2 and is not damaged. , The eddy current flaw detection sensor 1 is moved in the axial direction of the OPGW 10 and passed through the damaged portion, and is detected by the detection coil on the display screen of a commercially available eddy current flaw detection device ( Alternatively, the result shown in FIG. 4 was obtained as the locus of the detection signal displayed on the PC screen via the same device. In FIG. 4, the horizontal axis represents the value of the X signal of the detection signal (unit: V), and the vertical axis represents the value of the Y signal (unit: V). Both the horizontal axis and the vertical axis indicate 2V.

  In addition, the data displayed on the display screen of a commercially available eddy current flaw detector (or on the PC screen via the same device) is displayed with the horizontal axis as the time axis and the vertical axis as the Y signal value. The result shown in FIG. 5A was obtained, and the result shown in FIG. 5B was obtained by displaying the horizontal axis as the time axis and the vertical axis as the value of the X signal. In both FIG. 5A and FIG. 5B, the vertical axis represents 1 V on a scale, and the horizontal axis represents 0.5 sec on a scale.

  From the results shown in FIG. 4 and FIG. 5, it is determined that the non-magnetic aluminum tube 11a is damaged because the fluctuation of the Y signal value is large. On the other hand, the fluctuation of the X signal value is large. Therefore, it was judged that the steel wire, which is a magnetic material, was not damaged.

  In addition, measurement was performed using an OPGW10 (OPGW-60 as the line type standard) having an axial crack (width 2 mm × length 10 mm) as damage to the aluminum tube 11a, and the locus of the detection signal of the eddy current is illustrated. The results shown in FIG. 6 were obtained, and the results shown in FIG. 7 were obtained for the fluctuations in the values of the X and Y signals over time. Furthermore, measurement was performed using OPGW10 (OPGW-60 as the standard of the line type) having a frozen crack (crack length: 0.9 mm) as damage to the aluminum tube 11a, and the result of the detection signal locus shown in FIG. The results shown in FIG. 9 were obtained for fluctuations in the values of the X and Y signals with time. 6 and 8, the scale represents 2V on both the horizontal axis and the vertical axis. In both FIG. 7 and FIG. 9, the vertical axis represents 1V and the horizontal axis represents 0.5 sec.

  From the results shown in FIGS. 7 and 9, in any case, it is determined that the non-magnetic aluminum tube 11a is damaged because the fluctuation in the value of the Y signal is large. Since the fluctuation of the value cannot be said to be large, it was judged that the steel wire, which is a magnetic material, was not damaged.

  From these results, according to the eddy current flaw detection method of the present invention, regardless of the type of damage, even if the damage is as small as less than 1 mm, the detection of damage is accurately and accurately performed. It has been confirmed that it is possible to do this.

(2) Confirmation of difference in flaw detection performance due to difference in sensor specifications Next, in order to confirm whether there is a difference in flaw detection performance of the eddy current flaw detection method of the present invention due to difference in sensor specifications, the outer circumference of the inspection object The distance between the surface and the inner peripheral surface of the output coil and the detection coil, that is, the thickness of the peripheral wall of the bobbin 2 at the bottom 2e of the groove 2d is changed in three steps of 1.6 mm, 4.3 mm, and 9.3 mm. As a species standard, OPGW-60) aluminum tube 11a was artificially provided with a through hole or an axial crack, or damage caused by freezing due to an actual natural phenomenon was detected. In addition, it measured using OPGW10 which confirmed that there was no damage other than the damage of the detection target of the aluminum pipe 11a.

First, measurement was performed using an OPGW 10 having an axial crack (width 2 mm × length 10 mm) as damage to the aluminum tube 11a, and the result shown in FIG. 10 was obtained. In FIG. 10, the horizontal axis represents the distance (unit: mm) between the outer peripheral surface of the inspection object and the inner peripheral surface of the output coil and detector coil, and the vertical axis represents the amplitude (unit: V). Moreover, the test piece which has the following specifications was used as each test piece.
Test piece 1: Line type A, axial crack of width 0.2 mm × length 5 mm Test piece 2: Line type B, axial crack of width 0.2 mm × length 5 mm Test piece 3: Line type A, Axial crack with width 0.2 mm x length 15 mm Test piece 4: Line type B, axial crack with width 0.2 mm x length 15 mm The manufacturer differs between line type A and line type B.

Here, the amplitude is defined by Equation 2.
(Expression 2) Amplitude (V) = {(X signal value (V)) ² + (Y signal value (V)) ² } ^1/2

  That is, the amplitude indicates the distance from the origin in the X signal-Y signal diagrams (FIGS. 4, 6, and 8). When the X signal is 0 (the case of FIGS. 5 and 7), the amplitude indicates the height of the Y signal.

Further, measurement was performed using OPGW10 having frozen cracks (three types of crack lengths of 0.9 mm, 3.4 mm, and 4.6 mm) as damage to the aluminum tube 11a, and the results shown in FIG. 11 were obtained. In FIG. 11 as well, the horizontal axis is the interval (unit: mm) between the outer peripheral surface of the inspection object and the inner peripheral surface of the output coil and detector coil, and the vertical axis is the amplitude (unit: V). Moreover, the test piece which has the following specifications was used as each test piece.
Specimen 5: Freeze cracking with line type B, penetrating part length 0.9 mm Specimen 6: Freezing crack with line type A, penetrating part length 4.6 mm Specimen 7: Freezing crack with line type C, penetrating part length 3.4 mm In addition, the manufacturer is different between line type A and line type B,
Line type B and line type C have the same manufacturer but different lots.

  From these results, in the eddy current flaw detection method of the present invention, the detection signal resulting from the damage tends to be more prominent as the distance between the outer peripheral surface of the inspection object and the inner peripheral surface of the output coil and the detection coil is smaller. Yes, the distance between the outer peripheral surface of the inspection object and the inner peripheral surfaces of the output coil and the detection coil is preferably less than 10 mm, more preferably less than 5 mm, and most preferably less than 2 mm. It was confirmed that there was.

  In this embodiment, the OPGW 10 having the cross section shown in FIG. 3 is used as the inspection object, but the cross sectional configuration of the OPGW suitable for application of the eddy current flaw detection method of the present invention is not limited to this. Furthermore, the inspection object suitable for application of the present invention is not limited to OPGW.

It is a side view which shows an example of the eddy current flaw detection sensor used for implementation of this invention. It is a front view which shows an example of the eddy current flaw detection sensor used for implementation of this invention. It is sectional drawing of OPGW used as a test subject in an Example. It is a figure which shows the locus | trajectory of the detection signal of the eddy current of OPGW which has a through-hole in an aluminum tube. It is a figure which shows the X or Y signal of the eddy current of OPGW which has a through-hole in an aluminum tube. (A) is a figure which shows Y signal. (B) is a diagram showing an X signal. It is a figure which shows the locus | trajectory of the detection signal of the eddy current of OPGW which has a crack in an aluminum tube. It is a figure which shows the X or Y signal of the eddy current of OPGW which has a crack in an aluminum tube. (A) is a figure which shows Y signal. (B) is a diagram showing an X signal. It is a figure which shows the locus | trajectory of the detection signal of the eddy current of OPGW which has a freeze crack in an aluminum pipe. It is a figure which shows the X or Y signal of the eddy current of OPGW which has a freeze crack in an aluminum pipe. (A) is a figure which shows Y signal. (B) is a diagram showing an X signal. It is a figure explaining the fluctuation | variation of the amplitude accompanying the change of the space | interval of the test subject outer peripheral surface and coil inner peripheral surface in the detection of the damage of OPGW which has a crack in an aluminum pipe. It is a figure explaining the fluctuation | variation of the amplitude accompanying the change of the space | interval of the test subject outer peripheral surface and coil inner peripheral surface in the detection of the damage of OPGW which has a freeze crack in an aluminum pipe. It is a perspective view which shows the conventional eddy current flaw detection sensor.

Explanation of symbols

1 Eddy current flaw detection sensor 2 Bobbin 5 Connection terminal fixing board 7 Board fixing member

Claims (5)

It is a magnetic member after setting the detection signal to rotate around the origin so that the detection signal accompanying damage to the non-magnetic member is in the Y-axis direction on the two-dimensional coordinate axis of the X signal-Y signal. An output coil and a detection coil are wound around an optical fiber composite overhead ground wire as a tubular inspection object made of a steel wire and an aluminum tube which is a nonmagnetic member , and flaw detection is performed using the output coil and the detection coil. An electrical signal is measured for the optical fiber composite ground wire with a frequency of 70 kHz and utilizing an electromagnetic induction phenomenon, and the optical fiber composite ground wire is configured based on the variation of the X signal of the detection signal obtained by the measurement. vortex and detects a damage of the aluminum tube constituting the optical fiber composite overhead ground wire on the basis of the variations of the Y signal and detects a damage of the steel wire to Nagaresagu scratch method. 2. The eddy current flaw detection method according to claim 1, wherein a distance between an outer peripheral surface of the optical fiber composite ground wire and an inner peripheral surface of the output coil and the detection coil is less than 5 mm. A multi-coil sensors for measuring the electrical signal of test object using electromagnetic induction phenomenon, as the inspection object tubular made of an aluminum tube which is a non-magnetic member and the steel wire is a magnetic member An output coil and a detection coil that are wound around the outside of the optical fiber composite ground wire , and an interval between the outer peripheral surface of the optical fiber composite ground wire and the inner peripheral surface of the output coil and the detection coil is 5 mm. der is, eddy current sensor, characterized in that to make measurements flaw detection frequency as 70kHz below. An outer peripheral surface of an optical fiber composite ground wire as a tubular inspection object made of a steel wire as a magnetic member and an aluminum tube as a non-magnetic member , and an output coil wound around the optical fiber composite ground wire And using the eddy current sensor characterized in that the distance between the detection coil and the inner peripheral surface is less than 5 mm, the output coil and the detection coil wound around the optical fiber composite ground wire The flaw detection frequency is set to 70 kHz and an electric signal is measured for the optical fiber composite ground wire using an electromagnetic induction phenomenon, and the optical fiber composite ground wire is configured based on a fluctuation of a detection signal obtained by the measurement. An eddy current flaw detection method which makes it possible to detect damage to the aluminum tube without being affected by a signal from the steel wire . A multi-coil sensors for measuring the electrical signal of test object using electromagnetic induction phenomenon, as the inspection object tubular made of an aluminum tube which is a non-magnetic member and the steel wire is a magnetic member And an output coil and a detection coil wound around the outside of the optical fiber composite ground wire , and the distance between the outer peripheral surface of the optical fiber composite ground wire and the inner peripheral surface of the output coil and the detection coil is 5 mm. By making the value less than, the fluctuation of the detection signal obtained by the measurement of the electrical signal about the optical fiber composite ground wire using the electromagnetic induction phenomenon in which the flaw detection frequency using the output coil and the detection coil is 70 kHz is reduced. characterized by a detectable without being influenced damage the aluminum tube constituting the optical fiber composite overhead ground wire to the signal from the steel wire based Current flaw detection sensor.