JP5290020B2 - 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 aerial ground wire (hereinafter referred to as OPGW), with the passage of time since laying, for example, a crack in an aluminum pipe that is a member constituting OPGW due to fatigue, corrosion, or freezing due to strong wind vibration, Damage such as through holes or cracks may occur. Here, for example, in OPGW, the main cause of communication failure is damage to the aluminum tube. Since the aluminum tube is inside the stranded wire and the state cannot be grasped from the appearance, the location causing the failure in the OPGW New technology effective for prior identification and detection is desired.

  As a conventional non-contact type eddy current flaw detection method for detecting damage to a tubular inspection object composed of a magnetic member and a non-magnetic member by using eddy current due to electromagnetic induction, for example, as shown in FIG. Using an eddy current flaw detection sensor 100 having a cylindrical bobbin 101 provided with a through hole 101a in the axial direction, an output coil (excitation) is provided outside the tubular inspection object 104 in the circumferential direction of the inspection object 104. Measurement of an electrical signal of the inspection object 104 using an electromagnetic induction phenomenon using the output coil 102 and the detection coil 103 while winding a detection coil (also called a coil for detection) 102 and a detection coil (also called a detection coil) 103 And detecting the damage of the inspection object 104 based on the electric signal obtained by the measurement (Non-Patent Document 1).

Akira Ozaki: Applicability of Eddy Current Method to OPGW Aluminum Tube Diagnosis August.

  However, in the eddy current flaw detection method using the eddy current flaw detection sensor 100 of Non-Patent Document 1, damage in the axial direction of the inspection object 104 can be detected with very high accuracy. It is difficult to detect damage in the direction inclined with respect to the axial direction, specifically, in the direction inclined beyond the range of ± 30 degrees from the axial direction, and in particular, inclined by 90 degrees from the axial direction. There is a problem that damage in the direction, that is, the circumferential direction of the inspection object or a direction close to the circumferential direction cannot be detected.

  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 of the present invention is to provide a current flaw detection method and an eddy current flaw detection sensor.

  While examining the improvement of detection accuracy of damage in a tubular inspection object by a non-contact type eddy current flaw detection sensor, the present inventors have a shaft inclined with respect to the axial direction of the tubular inspection object. By providing a detection coil wound in the circumferential direction, in addition to detecting damage in the axial direction of the inspection object, it is also possible to detect damage in a direction inclined with respect to the axial direction including the circumferential direction. I found out.

The eddy current flaw detection method according to claim 1 is based on the above-mentioned new knowledge unique to the inventor, and the inspection object is formed outside the tubular inspection object composed of a magnetic member and a non-magnetic member. winding a plurality of detection coils in the circumferential direction of each of the plurality of axes of inclined and mutually in different directions with respect to the axial direction of the test object with wound around the output coils in the circumferential direction, one of the plurality of detection coils Electricity of an inspection object using an electromagnetic induction phenomenon (specifically, the nature of eddy current generated by electromagnetic induction) using an output coil and a plurality of detection coils. while moving the output coil and the plurality of detection coils after the zero-setting in undamaged position of the test object with respect to the signal in the axial direction of the inspection object performs measurement of the electrical signal, the electrical signal obtained by the measurement And to detect the damage of at least the non-magnetic member on the basis of the variation.

  It should be noted that the electromagnetic induction phenomenon used in the present invention, specifically, the nature of the eddy current generated by the electromagnetic induction, more specifically, the axis of the inspection object when an AC sine wave is applied to the output coil. When an electromotive force that cancels the magnetic field generated in the direction is generated in the detection coil, if there is a discontinuous part such as a scratch on the inspection object, the magnetic flux and eddy currents change to affect the electromotive force generated in the detection coil. Therefore, it is possible to detect damage to the inspection object by detecting this change in electromotive force in the detection coil. The frequency does not change between the output side and the detection side, but the amplitude and phase (that is, the phase angle) change depending on the presence or absence of scratches on the inspection object and the metal material of the inspection object.

The eddy current flaw detection sensor according to claim 2 is characterized in that an output coil and an inspection object wound around the inspection object on the outer side of a tubular inspection object made of a magnetic member and a non-magnetic member. A plurality of detection coils that are inclined with respect to the axial center direction and wound in the circumferential direction of each of a plurality of axes in different directions, and the plurality of detection coils are formed of a single wire, In the axial direction of the inspection object after zero setting is performed at the position where the inspection object is not damaged with respect to the electrical signal of the inspection object using the electromagnetic induction phenomenon using the output coil and the plurality of detection coils. The electric signal is measured while moving .

  Therefore, according to the eddy current flaw detection method and the eddy current flaw detection sensor, at least the detection coil is wound in the circumferential direction of the axis inclined with respect to the axial center direction of the inspection object. In addition to detecting damage in the axial direction, it is also possible to detect damage in a direction inclined with respect to the axial direction.

Further, according to the eddy current flaw detection method and the eddy current flaw detection sensor, it is possible to more reliably detect damage in all directions of the inspection object.

  According to the present invention, in addition to detecting damage in the axial direction of the inspection object, it is also possible to detect damage in a direction inclined with respect to the axial direction. It is possible to detect damage in an inspection object, which is an inspection object made up of a magnetic member and a non-magnetic member, with high accuracy, and to improve the reliability of inspection for the presence or absence of damage.

It is a front view of an example of an embodiment of an eddy current flaw detection sensor of the present invention. It is a bottom view of the eddy current flaw detection sensor of the embodiment. It is a side view of the eddy current flaw detection sensor of an embodiment. It is a bottom view of the state which wound the coil in the groove | channel of each bobbin of the eddy current flaw detection sensor of embodiment. It is a bottom view of an example of other embodiments of the eddy current flaw detection sensor of the present invention. It is a side view of an example of further another embodiment of the eddy current flaw detection sensor of the present invention. It is sectional drawing of OPGW used as a test subject in an Example. It is a figure which shows the detection result of the damage by the conventional sensor of an Example. It is a figure which shows the detection result of the damage by the coreless sensor of an Example. It is a figure which shows the detection result of the damage by the ferrite core sensor of an Example. It is a figure which shows the locus | trajectory of the electric signal of the eddy current of OPGW which has the linear crack of the axial center direction in the aluminum tube detected by the ferrite core sensor of an Example. It is a figure which shows the X or Y signal of the eddy current of OPGW which has the linear crack of an axial center direction in the aluminum tube detected by the ferrite core sensor of an Example. (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 electrical signal of the eddy current of OPGW which has the linear crack of the circumferential direction in the aluminum tube detected by the ferrite core sensor of an Example. It is a figure which shows the X or Y signal of the eddy current of OPGW which has the circumferential linear crack in the aluminum tube detected by the ferrite core sensor of an Example. (A) is a figure which shows Y signal. (B) is a diagram showing an X signal. It is a figure which shows the conventional eddy current flaw detection sensor.

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

  1 to 4 show an example of an embodiment of an eddy current flaw detection method and an eddy current flaw detection sensor according to the present invention. In this eddy current flaw detection method, the output coil 4 is wound in the circumferential direction of the inspection object 10 around the tubular inspection object 10 made of a magnetic member and a non-magnetic member, and the axis of the inspection object 10 is centered. The detection coil 5 is wound in the circumferential direction of the axis perpendicular to the direction, and the output signal 4 and the detection coil 5 are used to measure the electrical signal of the inspection object 10 using the electromagnetic induction phenomenon. The damage of at least the non-magnetic member is detected based on the fluctuation of the electric signal obtained by the measurement.

  In addition, the eddy current flaw detection sensor 1 of the present embodiment includes an output coil 4 wound around the inspection object 10 in the circumferential direction outside the tubular inspection object 10 composed of a magnetic member and a nonmagnetic member. And a detection coil 5 wound in the circumferential direction of an axis perpendicular to the axial direction of the inspection object 10, and using these output coil 4 and detection coil 5, an electromagnetic induction phenomenon is used. The electrical signal of the inspection object 10 is measured. The eddy current flaw detection sensor 1 according to the present embodiment includes a connection terminal fixing substrate 6 and a substrate fixing member 7.

  The measurement principle of the eddy current flaw detection method of the present invention uses an electromagnetic induction phenomenon (specifically, the nature of the eddy current generated by electromagnetic induction), and an output coil through alternating current is brought close to the inspection object. In this method, an eddy current is generated and a change in voltage is read from an electric signal (hereinafter also referred to as a detection signal) to inspect the inspection object for scratches.

  More specifically, the electric signal is typically a vector type eddy current flaw detector generally having two synchronous detectors whose phases are different from each other by 90 degrees, and one synchronous detector (synchronous detector X The electrical signal (referred to as X signal) that is the synchronous detection output by the other synchronous detector (referred to as synchronous detector Y) and the electrical signal (referred to as the Y signal) as the synchronous detection output from the other synchronous detector (referred to as synchronous detector Y). . In actual measurement, in order to capture a weak change in eddy current, a signal that cancels out such that the electrical signal becomes zero is added at a position where there is no flaw.

The X signal and Y signal of eddy current are X and Y components of amplitude and are defined by Equation 1.
(Equation 1) X signal [V] = amplitude [V] × cos θ, Y signal [V] = amplitude [V] × sin θ
Here, θ represents a phase angle [degree].

  The principle of the above-mentioned eddy current flaw detection method is general and well known (for example, the Japan Nondestructive Inspection Association, Hiroshi Hoshikawa: Nondestructive Inspection Technology Series Eddy Current Flaw Test 1 , Pp.41-49, March 2007.) A more detailed explanation is omitted here.

  Here, the measurement principle of the eddy current flaw detection method of the present invention is different from the so-called direct contact method used for detecting a surface crack. The direct contact method is a method for detecting minute surface defects while moving the sensor while the tip of the core of the eddy current sensor in which a coil is wound around the core is in contact with the object to be inspected. In this eddy current flaw detection method, an inspection object is inserted into a cylindrical air-core coil and detected without contact. In addition, according to the eddy current flaw detection method of the present invention which is a non-contact method, it is possible to detect damage to the non-magnetic member inside the inspection object.

  The parallel bobbin 2 is formed in a cylindrical shape having a through hole 2a that penetrates the tubular inspection object 10 at the axial center position. That is, the direction of the axis of the parallel bobbin 2 is parallel to the direction of the axis of the inspection object 10. The diameter of the through hole 2a is adjusted in accordance with the outer diameter of the tubular inspection object 10 on which the eddy current flaw detection sensor 1 measures an electric signal. The parallel bobbin 2 is formed of a nonconductive material such as a synthetic resin such as polyacetal.

  The parallel bobbin 2 has an annular groove 2b that goes around in the circumferential direction on the outer peripheral surface of the peripheral wall. The output coil 4 (not shown in FIGS. 1 and 2) is wound around the groove 2b. Since the output coil 4 is wound around the circumferential groove 2 b of the parallel bobbin 2, the output coil 4 is wound around the outer side of the inspection object 10 in the circumferential direction. Further, the output coil 4 and the inspection object 10 are not in contact with each other.

  Further, the eddy current flaw detection sensor 1 includes two orthogonal bobbins 3A and 3B in which the directions of the respective axes are orthogonal to the direction of the axis of the parallel bobbin 2, that is, the direction of the axis of the inspection object 10. Specifically, in this embodiment, the eddy current flaw detection sensor 1 has a first orthogonal bobbin 3A and a second orthogonal bobbin 3B, and the axes of the orthogonal bobbins 3A and 3B are positioned on a straight line. And arranged so as to face each other with the parallel bobbin 2 interposed therebetween, and is attached to a recess 2c provided on the outer peripheral side of the peripheral wall of the parallel bobbin 2. In the present embodiment, as described above, the directions of the axial centers of the two orthogonal bobbins 3A and 3B positioned on a straight line are orthogonal to the direction of the axial center of the parallel bobbin 2.

  Both orthogonal bobbins 3A and 3B respectively have annular grooves 3b that make one turn in the circumferential direction on the outer peripheral surface of the peripheral wall. A detection coil 5 (not shown in FIGS. 2 and 3) is wound around the grooves 3b of the orthogonal bobbins 3A and 3B. A single conducting wire is wound over the grooves 3b of the two orthogonal bobbins 3A and 3B to form the detection coil 5.

  Furthermore, in this embodiment, the through-hole 3a is formed in the axial center position of both orthogonal bobbin 3A, 3B, respectively, and the cylindrical core 15 is fitted by the said through-hole 3a. The core 15 is made of a magnetic material such as ferrite or soft iron. The shape of the core 15 is not limited to a columnar shape, and may be a cylindrical shape.

  The eddy current flaw detection sensor 1 performs eddy current flaw detection with an output coil 4 and a detection coil 5. For this reason, the positional relationship between the output coil 4 and the detection coil 5, that is, the positional relationship between the groove 2b and the groove 3b is such that the two coils 4 and 5 can operate as an output coil and a detection coil as eddy current flaw sensors. Set within the range.

  In the eddy current flaw detection sensor 1 of the present invention, the distance between the outer peripheral surface of the inspection object 10 and the output coil 4 when wound around the groove 2b, and the outer peripheral surface of the inspection object 10 and the groove 3b are wound. The distance between the detection coil 5 and the detection coil 5 when it is rotated is preferably narrow. Specifically, for example, the distance between the outer peripheral surface of the inspection object 10 and the coils 4 and 5 is preferably less than 10 mm, more preferably less than 5 mm. The interval between the outer peripheral surface and the output coil 4 is most preferably less than 2 mm. However, in the present invention, the inspection object 10 is not in contact with the output coil 4 and the detection coil 5.

  In the present embodiment, the connection terminal fixing substrate 6 is formed in a rectangular plate shape shorter than the length of the parallel bobbin 2 in the axial direction, and is arranged so that the longitudinal direction is parallel to the axial direction of the parallel bobbin 2. .

  The substrate fixing member 7 is attached to each of the positions close to the both end portions of the parallel bobbin 2. The substrate fixing member 7 is composed of two Ω-shaped members, and an Ω-shaped concave portion 7 a is formed in a semicircular curved surface, and the semicircular curved surface of the concave portion 7 a is formed in accordance with the shape of the outer peripheral surface of the parallel bobbin 2. Is done. Then, the substrate fixing member 7 is attached to the outer peripheral surface of the parallel bobbin 2 so that the parallel bobbin 2 is sandwiched between a pair of Ω-shaped members.

  The substrate fixing member 7 also has through holes 7c at both end portions 7b of the Ω-shaped recess 7a. And the recessed part 7a of the board | substrate fixing member 7 which makes a pair faces each other, the parallel bobbin 2 is pinched | interposed, and the edge part 7b is tightened with the volt | bolt 8a and the nut 8b which penetrate both the through-holes 7c of the opposite edge part 7b. Thus, the substrate fixing member 7 is fixed to the parallel bobbin 2.

  The connection terminal fixing substrate 6 has through holes 6c on both sides in the longitudinal direction of the rectangle. Then, the connection terminal fixing substrate 6 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 6 c. That is, when the two board fixing members 7 face each other and the parallel bobbin 2 is sandwiched, the positions of the through holes 7c of the end portions 7b of the opposing board fixing members 7 and the through holes 6c of the connection terminal fixing board 6 are aligned. Then, the connecting terminal fixing substrate 6 is sandwiched between the two substrate fixing members 7, and the opposing substrate fixing member 7 and the connecting terminal fixing substrate 6 are bundled and fixed.

  A connection terminal 9 a that is electrically connected to both ends of the output coil 4 and a connection terminal 9 b that is electrically connected to both ends of the detection coil 5 are attached to the connection terminal fixing substrate 6. Then, in order to electrically connect the output coil 4 and the connection terminal 9a, and the detection coil 5 and the connection terminal 9b, the connection terminal fixing substrate 6 is further connected with two terminals for connecting both ends of the output coil 4. A pair of connection holes 6a and two sets of connection holes 6b for connecting both ends of the detection coil 5 are provided, and between the connection hole 6a and the connection terminal 9a, and between the connection hole 6b and the connection terminal 9b. A lead 6d is provided between the two.

  A connection terminal 9a electrically connected to both ends of the output coil 4 is used to set the display angle of the X signal and the Y signal (specifically, center on the origin on the two-dimensional coordinate axis of the X signal-Y signal). This is a function to rotate and display a predetermined angle (also called a set angle of a phase shifter). A cable (not shown) on the output side from a single frequency type eddy current flaw detector capable of being connected is connected and connected. An AC voltage is supplied to the output coil 4 via the terminal 9a.

  Further, a wiring (not shown) from the eddy current flaw detector is connected to the connection terminal 9b that is electrically connected to both ends of the detection coil 5, and is induced in the inspection object 10 by the AC voltage supplied to the output coil 4. Then, the induced voltage detected by the detection coil 5 is input as a detection signal (X signal and Y signal) to the eddy current flaw detector via the connection terminal 9b. In addition, as an eddy current flaw detector in the present invention, a device used for general eddy current flaw detection can be used. Further, the detection signal is specifically a voltage (a general eddy current flaw detector itself is well known, so a more detailed explanation is omitted here. For example, the Japan Nondestructive Inspection Association, edited by Hiroshi Hoshikawa : Non-destructive inspection technology series. See Eddy current test 1, pp.41-49, March 2007.)

  In detection work using the present invention, a weak signal generated from a damaged portion of a nonmagnetic member inside the inspection object 10 is not buried by a strong signal from a surrounding magnetic member. In order to be able to detect them separately, a test piece in which damage is given in advance to the non-magnetic member of the inspection object 10 is inserted into the through-hole 2a of the parallel bobbin 2 of the eddy current flaw detection sensor 1 so that no damage occurs. After the signals are balanced with each other (that is, after zero setting is performed for each combination of the sensor and the inspection object), the eddy current flaw detection sensor 1 is moved along the axial direction of the inspection object to accompany the damage. Get an electrical signal.

  Specifically, first, a display angle (that is, phase shift) that should be rotated around the origin so that a detection signal accompanying damage to the nonmagnetic member is substantially in the Y-axis direction on the two-dimensional coordinate axis of the X signal-Y signal. The set angle of the container). If the device does not have a phase shifter display function, the base of the triangle (amplitude [V] × cos θ, θ: phase angle [degree]) is obtained using the amplitude and phase angle obtained as the detection signal of the damaged portion. The angle θ is 90 degrees (that is, the Y axis) where the X signal value (unit is V) and the height (amplitude [V] × sin θ, θ: phase angle [degree]) is the Y signal value (unit is V). The display angle to be rotated is obtained by subtracting from (the angle).

  Next, the display angle to be rotated (that is, the set angle of the phase shifter) determined as described above is set, and the tubular inspection object is inserted into the through-hole 2a of the parallel bobbin 2 of the eddy current flaw detection sensor 1. AC is supplied to the output coil 4 while moving the eddy current flaw detection sensor 1 in the axial direction of the inspection object 10 after balancing (ie, setting 0 point) at an undamaged position in a state where the object 10 is penetrated. An induction voltage induced in the inspection object 10 by the voltage is detected by the detection coil 5.

  Since the phase angle of the magnetic member such as steel and the non-magnetic member such as aluminum is shifted by about 90 degrees, the present invention induces the inspection object 10 by the AC voltage supplied to the output coil 4. Then, based on the variation of the X signal of the induced voltage detected by the detection coil 5, the damage of the magnetic member constituting the inspection object 10 is detected and the inspection object 10 is configured based on the variation of the Y signal. Detects damage to the magnetic member.

  Specifically, regarding the electric signal obtained by the measurement using the eddy current flaw detection sensor 1, when 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.

  According to the eddy current flaw detection method and eddy current flaw detection sensor of the present invention configured as described above, in addition to detecting damage in the axial direction of the inspection object, damage in a direction inclined with respect to the axial direction Can be detected with high accuracy, for example, in a tubular inspection object such as OPGW, and it is possible to detect damage in the inspection object consisting of a magnetic member and a non-magnetic member, The reliability of inspection for occurrence of damage can be improved.

  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 (that is, the set angle of the phase shifter) provided in the eddy current flaw detector, the damage of the magnetic member is evaluated by the Y signal, and the damage of the non-magnetic member is evaluated by the X signal. Also good.

In addition, in the case where damage to the magnetic member is not subject to detection / evaluation and only damage to the non-magnetic member is to be subject to detection / evaluation, only the amplitude is used instead of the X signal value or the Y signal value. You may make it evaluate. The amplitude is defined by Equation 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.
(Equation 2) Amplitude [V] = {(X signal value [V]) ² + (Y signal value [V]) ² } ^1/2

  In the present embodiment, the through holes 3a are formed at the axial center positions of the two orthogonal bobbins 3A and 3B, and the core 15 made of a magnetic material is fitted into the through holes 3a. It is not an essential requirement in the present invention to fit the magnetic core 15 to 3A and 3B. Although it can be expected to improve the detection capability of the detection coil wound around this by fitting a magnetic core to the orthogonal bobbin, the detection coil detects the induction voltage even if the core is not fitted. Is possible.

  In the present embodiment, the two orthogonal bobbins 3A and 3B are arranged so as to face each other with the parallel bobbin 2 interposed therebetween, that is, with the inspection object 10 interposed therebetween. The bobbins 3 </ b> A and 3 </ b> B need only be arranged side by side in the circumferential direction of the inspection object 10, and do not have to be in a positional relationship facing each other across the inspection object 10.

  Further, in the present embodiment, both the first orthogonal bobbin 3A and the second orthogonal bobbin 3B are arranged so that the axis direction is orthogonal to the axial direction of the parallel bobbin 2, that is, the axial direction of the inspection object 10. However, the present invention is not limited thereto, and the axial direction of one or both of the two orthogonal bobbins 3A and 3B and the detection coils wound around these bobbins is the axial direction of the inspection object 10. You may make it shift | deviate from the orthogonal direction (FIG. 5. In addition, in FIG. 5-7, the connection terminal fixed board | substrate 6 and the board | substrate fixing member 7 are not illustrated). Even when only one bobbin around which the detection coil is wound is provided, the axial direction of the bobbin need not be orthogonal to the axial direction of the inspection object 10. Further, in the embodiment shown in FIG. 5, the axial center direction of the detection coil 5 wound around the orthogonal bobbin 3B is inclined along the axial center direction of the inspection object 10. The inclination is not limited to this, and may be inclined along the circumferential direction of the inspection object 10 as shown in FIG. Still further, the inclination of the detection coil in the axial direction does not have to be along the axial direction or the circumferential direction of the inspection object 10, and any direction with respect to the axial direction of the inspection object 10. As long as it is inclined in the direction.

  Moreover, in this embodiment, in addition to the parallel bobbin 2 having the groove 2b around which the output coil 4 to be wound around the axial center of the tubular inspection object 10 is wound, Two bobbins each having a groove 3b around which a detection coil 5 to be wound in the circumferential direction of an axis perpendicular to the axial direction is disposed, and are arranged opposite to each other with the parallel bobbin 2 in between. The first orthogonal bobbin 3A and the second orthogonal bobbin 3B are provided. However, the present invention is not limited to this, and the number of bobbins around which the detection coil 5 is wound may be one or three or more. When three or more bobbins around which the detection coil 5 is wound are provided, the axial direction of these bobbins and the detection coil wound around the bobbin is inclined with respect to the axial direction of the inspection object 10. It is desirable to make all the angles different. By making all the inclination angles in the axial direction of the detection coil different, damage in all directions of the inspection object 10 can be detected. When three or more bobbins around which the detection coil is wound are provided, it is desirable that these bobbins are arranged in the circumferential direction of the inspection object 10.

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

FIG. 8 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 OPGW 10 used in this example is OPGW-60 (60 represents a nominal area of 60 mm ² as a lightning protection ground wire) as the line type standard, and the total of the eight aluminum-clad steel wires 14 in FIG. The total outer diameter is 11.4 mm, and the outer diameter of the aluminum tube 11a is 5 mm.

  The optical fiber housing aluminum tube 11 includes an aluminum tube 11a as 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 actual OPGW maintenance and inspection, damage to the aluminum tube 11a in the central portion that cannot be clearly seen from the outside is particularly problematic. Therefore, according to the present invention, detection of damage to the aluminum tube 11a of the OPGW 10 can be performed. Being able to do it properly is very beneficial for actual OPGW maintenance.

  In this example, the flaw detection performance was compared by the difference in the inclination angle of the linear crack formed in the OPGW 10 with respect to the axial center direction of the OPGW 10. Specifically, the aluminum tube 11a inside the OPGW 10 cut to a length of about 1 m is taken out as a test material, and the aluminum tube 11a is taken in the tube axis direction (synonymous with the axial direction) or 10 degrees with respect to the tube axis direction. A linear crack in a direction inclined at any angle of 45 °, 70 °, or 90 ° is artificially formed and then returned to the inside of the OPGW 10 to create an OPGW 10 having a linear crack inside as damage. did. The direction inclined 90 degrees with respect to the tube axis direction is the circumferential direction of the aluminum tube 11a.

  The width of the linear crack was about 0.2 mm to 2 mm and the length was about 5 mm to 50 mm. In addition, one damage was artificially formed for each aluminum tube 11a, and measurement was performed using the OPGW 10 that was confirmed to be free of damage other than the artificially formed damage to the detection target.

  In this embodiment, the core 15 is inserted into the through holes 3a of the orthogonal bobbins 3A and 3B around which the detection coil 5 is wound in the eddy current flaw detection sensor 1 of the present invention shown in FIGS. A sensor in which a cylindrical ferrite is inserted as a core 15 in the through hole 3a (hereinafter referred to as a ferrite core sensor), As a comparative example with the sensor according to the present invention, damage to the aluminum tube 11a for each OPGW 10 was detected under the same conditions for each of the conventional eddy current flaw detection sensors (hereinafter referred to as conventional sensors) shown in FIG. The diameter of the through hole 2a (or 101a) of the parallel bobbin 2 (or 101) of the eddy current flaw detection sensor 1 (or 100) was 13 mm in accordance with the entire outer diameter of the OPGW 10.

  Furthermore, in the present embodiment, a single frequency eddy current flaw detector manufactured by Uni Denshi Kogyo Co., Ltd. is used as an eddy current flaw detector which is electrically connected to the eddy current flaw detector 1 via the connection terminals 9a and 9b and performs measurement for damage detection. Using the apparatus [EddyStation SW2], the measurement / data display software attached to the apparatus operating on a computer (PC) was used.

  In the measurement, first, the OPGW 10 is inserted into the through hole 2a (or 101a) of the eddy current flaw detection sensor 1 (or 100) to balance the electric signal (that is, zero setting) at a position where there is no damage, and then the OPGW 10 The eddy current flaw detection sensor 1 (or 100) was moved along the axial direction, and detection signals (X signal and Y signal) accompanying damage were obtained.

  Then, a change in the detection signal displayed on the computer monitor via the eddy current flaw detector (specifically, when there is damage, a convex shape or peak shape appears) is visually observed, and as a result Are classified into three types: i) detectable, ii) difficult to determine, and iii) undetectable. Note that it was difficult to determine whether it was difficult to determine whether the obtained signal was due to a defect or noise.

  In this example, the measurement frequency was 70 kHz. In addition, the voltage ratio, that is, the gain of the amplifier was basically 30 dB, and when it was not detectable at 30 dB, the dB value was sequentially increased to 40, 50, 60 to a detectable level and measured.

  And damage was detected using the conventional sensor, and the result shown in FIG. 9 was obtained. In FIGS. 9 to 11, the above-mentioned i) detectability is represented by the symbol ◯, ii) difficulty of determination is represented by the symbol Δ, and iii) undetectable is represented by the symbol x. From this result, in the case of the conventional sensor, the damage in the tube axis direction of the inspection object 10 and the direction inclined at an angle of 10 degrees with respect to the tube axis direction can be detected even if the width is narrow, It was confirmed that damage in the direction that is largely inclined with respect to the tube axis direction of the inspection object 10 and in the circumferential direction cannot be detected.

  Further, damage was detected using a coreless sensor, and the result shown in FIG. 10 was obtained. From this result, in the case of the sensor without the core, in addition to the damage in the tube axis direction of the inspection object 10 and the direction close to the tube axis direction as in the case of the conventional sensor, in addition to the tube axis direction of the inspection object 10 It was confirmed that the damage in the tilting direction and the circumferential direction can be generally detected even if the width is narrow. Note that damage in a direction inclined at an angle of 45 degrees with respect to the tube axis direction could not be detected. It should be noted that two orthogonal bobbins 3A and 3B cannot be detected by the eddy current flaw detection sensor 1 shown in FIGS. 1 to 4 in a direction inclined at an angle of 45 degrees with respect to the tube axis direction. Can be eliminated by disposing one of the axial centers so as to deviate from the direction orthogonal to the axial direction of the parallel bobbin 2 (see FIGS. 5 and 6).

  Furthermore, damage was detected using a ferrite core sensor, and the results shown in FIG. 11 were obtained. From this result, in the case of the ferrite core sensor, it is possible to detect almost any damage regardless of the direction from the axial center direction to the circumferential direction of the inspection object 10 as in the case of the coreless sensor. It was confirmed that it was possible to detect damage that was narrower than when a sensor was used.

  In the case of damage detection using a ferrite core sensor, the result shown in FIG. 12 is obtained as a locus of a detection signal when a linear crack having a width of 1 mm and a length of 10 mm is detected in the tube axis direction of the OPGW 10. The result shown in FIG. 14 was obtained as the locus of the detection signal when a linear crack having a width of 1 mm was detected in the circumferential direction of OPGW10. The locus of the detection signal is a locus of a change in voltage value on the two-dimensional coordinate plane of the X signal-Y signal detected by the detection coil of the sensor and displayed on the computer monitor via the eddy current flaw detector. 12 and 14, the horizontal axis represents the value of the X signal (unit is V), and the vertical axis represents the value of the Y signal (unit is V). The scale on both the horizontal and vertical axes is 2 [V].

  Further, the data displayed on the computer monitor via the eddy current flaw detector is displayed with the horizontal axis as the time axis and the vertical axis as the value of the Y signal, thereby detecting damage in the tube axis direction of the OPGW 10. The result shown in FIG. 13A was obtained, and the result shown in FIG. 15A was obtained for detection of damage in the circumferential direction. In addition, by displaying the horizontal axis as the time axis and the vertical axis as the value of the X signal, the result shown in FIG. 13B for the detection of damage in the tube axis direction of the OPGW 10 is obtained, and the damage in the circumferential direction is obtained. As a result, the result shown in FIG. 15B was obtained. 13 and 15, the vertical axis is 1 [V], and the horizontal axis is 0.5 [sec].

  From the results shown in FIGS. 13 and 15, 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 14 that is a magnetic body was not damaged.

  From these results, according to the eddy current flaw detection method and the eddy current flaw detection sensor of the present invention, not only damage in the axial direction of the inspection object but also damage in a direction inclined with respect to the axial direction, Furthermore, it was confirmed that the damage can be detected accurately and accurately even if the damage is in the circumferential direction of the axis of the inspection object.

  In this embodiment, the OPGW 10 having the cross section shown in FIG. 8 is used as the inspection object. However, the cross sectional configuration of the OPGW suitable for application of the eddy current flaw detection method and eddy current flaw detection sensor of the present invention is not limited thereto. In other words, the inspection object suitable for application of the present invention is not limited to OPGW.

DESCRIPTION OF SYMBOLS 1 Eddy current flaw detection sensor 2 Parallel bobbin 2a Through hole 2b Groove 2c Recess 3A 1st orthogonal bobbin 3B Second orthogonal bobbin 3a Through hole 3b Groove 4 Output coil 5 Detection coil 6 Connection terminal fixed board 6a Connection hole 6b Connection hole 6c Through hole 6d Lead 7 Substrate fixing member 7a Recess 7b End 7c Through hole 8a Bolt 8b Nut 9a Connection terminal 9b Connection terminal 10 Inspection object (OPGW)
11 Optical fiber housing aluminum tube 11a Aluminum tube 12 Optical fiber unit 13 Grooved aluminum spacer 13a Groove 14 Aluminum covered steel wire

Claims (2)

An output coil is wound in the circumferential direction of the inspection object on the outside of a tubular inspection object made of a magnetic member and a non-magnetic member, and is inclined with respect to the axial direction of the inspection object and mutually different directions winding a plurality of detection coils in a plurality of axes each circumferential direction, a plurality of detection coils so as to form in one of the conductors, electromagnetic of using a plurality of detection coil and the output coil After zero setting is performed at a position where the inspection object is not damaged with respect to the electrical signal of the inspection object using the induction phenomenon, the output coil and the plurality of detection coils are moved in the axial direction of the inspection object. is allowed while measurement of the electrical signal, an eddy current flaw detection method characterized by detecting damage to at least said non-magnetic member on the basis of the variation of the electric signal obtained by the measurement An output coil wound in a circumferential direction of the inspection object and an axial direction of the inspection object are inclined with respect to each other outside a tubular inspection object made of a magnetic member and a non-magnetic member. A plurality of detection coils wound in the circumferential direction of each of a plurality of axes in different directions, the plurality of detection coils being formed by a single conductor, and the output coil and the plurality of detection coils. The electric signal for the inspection object using the electromagnetic induction phenomenon used is moved in the axial direction of the inspection object after zeroing is performed at a position where the inspection object is not damaged. An eddy current flaw detection sensor characterized by

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