JP2019032210A - Defect inspection method and defect inspection device - Google Patents

Abstract

To provide a defect inspection method and a defect inspection device that are capable of efficient and precise inspection.SOLUTION: An inspection object 101 is made of a material that is conductive in an axial direction A thereof. A wire 2a is wound such that a central axis of a coil 2 is along a circumferential direction C of the inspection object 100. The coil 2 has a fan shape covering a part of an outer peripheral surface 101x of the inspection object 101. Such fan-shaped coils 2 are arranged with a predetermined interval over the outer peripheral surface 101x, where a central angle of the fan-shaped coils 2 is adjusted such that the magnetic flux extending from one end of the fan-shaped coils 2 through the inspection object 100 to the other end of the fan-shaped coils 2 is dense in the vicinity of the outer peripheral surface. The fan-shaped coils 2 are arranged with the predetermined interval over the outer peripheral surface 101x and eddy current is generated in the outer peripheral surface 101x along the axial direction A of the inspection object 101. A value attributed to the eddy current is measured with the fan-shaped coil 2, and the presence or absence of defects in the outer peripheral surface 101 is inspected on the basis of the measurement result.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a defect inspection method and a defect inspection apparatus. More specifically, a defect for inspecting the presence or absence of a defect in the inspection object by measuring an value caused by an eddy current generated in the inspection object by electromagnetic induction by applying an AC voltage to a coil formed by winding a wire. The present invention relates to an inspection method and a defect inspection apparatus.

  Conventionally, the eddy current flaw detection test as described above is known as a method for inspecting the presence or absence of defects in an inspection object. In this test, when the distance (lift-off) between the coil (probe) and the inspection object is increased, the eddy current generated by electromagnetic induction is reduced, so that the detection sensitivity is significantly reduced. Therefore, for example, in the inspection of the inspection object covered with the covering material, it is difficult to accurately detect the defect.

  Further, for example, a cable inspection method described in Patent Document 1 is known. In this inspection method, an alternating voltage is directly applied to the strands with adjacent strands as a set, and a value related to the capacitance between the strands is measured. For this reason, if there is an insulation failure (short circuit) between the strands, there is a possibility that capacitance does not occur between the strands and the inspection accuracy is lowered. In addition, when the damage is large, current does not flow downstream from the damaged portion, so that the downstream inspection may be difficult. Furthermore, in order to obtain the damage result of the whole cable, the combination of the strands must be changed and measured many times, and improvement in workability has been desired. Moreover, if the strands are coated, an operation for exposing the strands is required, and the workability is further reduced.

JP 2013-167602 A

  In view of such a conventional situation, an object of the present invention is to provide a defect inspection method and a defect inspection apparatus capable of inspecting efficiently and with high accuracy.

  In order to achieve the above object, the defect inspection method according to the present invention is characterized in that an alternating voltage is applied to a coil formed by winding an element wire to measure a value caused by eddy current generated in an inspection object by electromagnetic induction. Thus, in the configuration for inspecting whether there is a defect in the inspection object, the inspection object is made of a material having conductivity in the axial direction, and the wire has a central axis of the coil of the inspection object. The coil is wound along a circumferential direction, and the coil has a fan shape covering a part of the outer peripheral surface of the inspection object, and the fan coil is disposed with a predetermined gap with respect to the outer peripheral surface. The center angle of the fan coil is adjusted so that the magnetic flux passing from the one end of the fan coil to the other end of the fan coil through the inspection object becomes dense near the outer peripheral surface, Predetermined against the outer peripheral surface A gap is provided, the AC voltage is applied to the fan-shaped coil to generate an eddy current along the axial direction of the inspection object on the outer peripheral surface by the electromagnetic induction, and the value resulting from the eddy current is The measurement is performed with a fan coil, and the presence or absence of a defect on the outer peripheral surface is inspected based on the measurement result.

  According to the above configuration, since the element wire is wound so that the central axis of the coil is along the circumferential direction of the inspection object, the axial direction is applied to the inspection object made of a material having conductivity in the axial direction. Eddy currents can be generated. The coil has a fan shape covering a part of the outer peripheral surface of the inspection object, and when the fan coil is disposed with a predetermined gap with respect to the outer peripheral surface of the inspection object, the coil is inspected from one end of the fan coil. The central angle of the fan coil is adjusted so that the magnetic flux passing through the object and going to the other end of the fan coil becomes dense near the outer peripheral surface. As a result, even if a predetermined gap (lift-off) is provided with respect to the outer peripheral surface of the inspection object, a vortex along the axial direction is formed on the outer peripheral surface of the inspection object by improving the magnetic flux density in the vicinity of the region to be inspected. The detection accuracy can be improved by increasing the current. Moreover, since the value resulting from the eddy current is measured with a predetermined gap (lift-off) with respect to the outer peripheral surface of the inspection object, the inspection can be performed at high speed and the inspection efficiency is high.

  The said structure WHEREIN: The said fan-shaped coil is good to be wound by the fan-shaped core which consists of magnetic materials. Accordingly, leakage of magnetic flux from the coil can be suppressed, and magnetic flux passing from the one end of the fan coil to the other end of the fan coil can be increased (concentrated). The current further increases, and the inspection accuracy can be improved.

  In addition, a pair of the fan-shaped coils are provided at an appropriate interval in the axial direction of the inspection object, the pair of fan-shaped coils are relatively moved in the axial direction, and the presence or absence of the defect is inspected by an output difference between the pair of fan-shaped coils. Good. Thereby, noise (backlash noise) generated due to a change in the gap (lift-off) between the coil and the inspection object can be suppressed, and the inspection accuracy can be further improved.

  A plurality of the fan-shaped coils may be arranged along the circumferential direction of the inspection object. Thereby, for example, the entire circumference of the inspection object can be inspected with a single scan with high accuracy, and the inspection efficiency is further improved.

  In any one of the above configurations, the inspection object may be a single strand made of a fiber-reinforced composite material having conductivity, and the inspection object may be a plurality of fibers made of a fiber-reinforced composite material having conductivity. You may be comprised with the strand of a book. In this case, the one strand may be covered with a covering material, and the gap may include the thickness of the covering material. The plurality of strands may be covered with a covering material, and the gap may include the thickness of the covering material.

  In order to achieve the above object, the defect inspection apparatus according to the present invention is characterized in that an AC voltage is applied to a coil formed by winding an element wire to measure a value caused by an eddy current generated in an inspection object by electromagnetic induction. Thus, in the configuration for inspecting whether there is a defect in the inspection object, the inspection object is made of a material having conductivity in the axial direction, and the wire has a central axis of the coil of the inspection object. The coil is wound along a circumferential direction, and the coil has a fan shape covering a part of the outer peripheral surface of the inspection object, and the fan coil is disposed with a predetermined gap with respect to the outer peripheral surface. In addition, the central angle of the fan coil is adjusted so that the magnetic flux passing from the one end of the fan coil to the other end of the fan coil through the inspection object becomes dense near the outer periphery, With a predetermined gap AC application means for applying the AC voltage to the fan-shaped coil and generating an eddy current along the axial direction of the inspection object by the electromagnetic induction on the outer peripheral surface; and a value due to the eddy current in the fan-shaped And determining means for measuring with a coil and determining the presence or absence of a defect on the outer peripheral surface based on the measurement result.

  The said structure WHEREIN: The said fan-shaped coil is good to be wound by the fan-shaped core which consists of magnetic materials.

  In addition, a pair of the fan-shaped coils may be provided at appropriate intervals along the axial direction of the inspection object, and the determination means may inspect for the presence / absence of the defect based on an output difference between the pair of fan-shaped coils.

  It is preferable to further include a jig for holding the fan coil at a predetermined position with respect to the center of the inspection object. In this case, the jig may hold a plurality of the fan-shaped coils along the circumferential direction of the inspection object.

  In order to achieve the above object, another feature of the defect inspection method according to the present invention is that an AC voltage is applied to a coil formed by winding a wire, and a value caused by eddy current generated in an inspection object by electromagnetic induction is set. In the method for inspecting whether there is a defect in the inspection object by measuring, the inspection object is made of a material having conductivity in a certain direction, and the strand is formed on the surface of the inspection object. In order to generate an eddy current along the direction of the coil, a magnetic flux from one end to the other end of the coil is wound so as to pass through the inspection object, and the magnetic flux is dense in the vicinity of the surface. A coil is disposed with a predetermined gap with respect to the surface, and the AC voltage is applied to the coil to generate an eddy current along the fixed direction on the surface by the electromagnetic induction, resulting from the eddy current. The value Measured in Le is to inspect the presence or absence of a defect of the surface based on the measurement result.

  In order to achieve the above object, another feature of the defect inspection apparatus according to the present invention is that a value resulting from an eddy current generated in an inspection object by electromagnetic induction by applying an AC voltage to a coil formed by winding a wire is used. In the configuration in which the inspection object is inspected for defects by measuring, the inspection object is made of a material having conductivity in a certain direction, and the strands are formed on the surface of the inspection object. In order to generate an eddy current along the direction of the coil, the coil is wound so that a magnetic flux from one end to the other end of the coil passes through the inspection object, and the coil is dense in the vicinity of the surface. AC application means disposed at a predetermined gap with respect to the surface and applying the AC voltage to the coil to generate an eddy current in the fixed direction by the electromagnetic induction, and the eddy current Caused by current The value to be measured by the coils is to have a judging means for judging presence or absence of a defect of the surface based on the measurement result.

  According to the feature of the defect inspection method and the defect inspection apparatus according to the present invention, it is possible to inspect efficiently and with high accuracy.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

It is the schematic which shows the defect inspection method which concerns on 1st embodiment of this invention. It is sectional drawing of the high strength fiber composite material cable used as the test object in 1st embodiment. 1 is a block diagram of a defect inspection apparatus according to the present invention. It is a bridge circuit diagram. It is a longitudinal cross-sectional view of the coil and cable which show an inspection state typically. It is a figure which shows magnetic flux distribution typically. It is a figure explaining an example of an inspection method. It is a figure which shows an example of a jig | tool. It is a graph which shows the simulation result of the magnetic flux distribution by the coil with a core. It is a figure which shows the conditions of a simulation experiment. It is a figure which shows an example of the measurement signal of the reference | standard test body corresponding to a normal product. It is a figure which shows an example of the measurement signal of the reference | standard test body corresponding to a damaged article. It is a figure which shows an example of the coil in 2nd embodiment of this invention. It is a figure which shows an example of the other coil in 2nd embodiment of this invention. It is a figure which shows an example of the coil in other embodiment of this invention. It is a figure which shows another example of the coil in other embodiment of this invention. FIG. 10 is a diagram corresponding to FIG. 9 illustrating a simulation result of magnetic flux distribution by a coil without a core. It is a figure which shows an example of the Lissajous waveform corresponding to FIG. 11A. It is a figure which shows an example of the Lissajous waveform corresponding to FIG. 11B. It is a figure which shows an example of the other test target object of this invention.

Next, the first embodiment of the present invention will be described in more detail with reference to FIGS.
The inspection object in the first embodiment of the present invention is a fiber reinforced composite material cable (hereinafter simply referred to as “cable”) including a strand 101 made of a fiber reinforced composite material having conductivity in the axial direction. For example, as shown in FIG. 2, the cable 100 of the present embodiment is configured as a stranded wire by arranging six strands 101 around a central strand 101 in a substantially point-symmetric manner and twisting them together. The outer periphery is covered with a covering material 102 made of a resin material such as vinyl chloride.

  The strand 101 is composed of several tens of thousands of carbon fibers 101a each having a size of about several μm, and is consolidated (impregnated) with a resin 101b such as thermoplastic resin. The thickness (wall thickness) of the covering material 102 is, for example, about 1 mm for the cable 100 having an outer diameter of φ8 mm and about 2-3 mm for the cable 100 having an outer diameter of φ12 mm. This thickness becomes a part G1 of the gap G between the outer peripheral surface 101x of the strand 101 as the inspection object and the coil 2 described later. Examples of the fiber reinforced composite material include carbon fiber reinforced plastic (CFRP). In the present embodiment, the cable includes some flexible things such as a wire and a rope.

  As shown in FIG. 1, a defect inspection apparatus 1 for a cable 100 according to a first embodiment of the present invention generally includes a coil 2 formed by winding a wire 2 a and electromagnetic induction by applying an AC voltage to the coil 2. An eddy current flaw detector 3 having an oscillator 31 as an AC applying means for generating an eddy current E along the axial direction A of the strand 101 on the outer peripheral surface 101x, and measuring a value caused by the eddy current E with the coil 2. The signal processing device 4 is provided as determination means for determining the presence or absence of damage D such as breakage of the strand 101 based on the measurement result of the eddy current flaw detector 3.

  As shown in FIG. 1, the coil 2 is a fan-shaped coil that covers a part of the outer peripheral surface of the cable 100 (the outer peripheral surface 101 x of the plurality of strands 101), and the central axis of the fan-shaped coil 2 is the cable 100 ( This is a self-inductive coil composed of a strand 2a (winding) wound along the circumferential direction of a plurality of strands 101). This coil performs excitation for generating an alternating magnetic field (magnetic field) by alternating current and detection of a change in eddy current (induced current) with the same coil.

  The fan-shaped coil 2 in the present embodiment includes a pair of first and second coils 21 and 22 that are arranged at appropriate intervals in the axial direction A of the strand 101 (cable 100). When an alternating voltage is applied to the first and second coils 21 and 22, as shown in FIG. 5, the strand 2a is turned so that the directions of the eddy currents E generated on the outer peripheral surface 101x of the strand 101 are opposite to each other. By winding, an output difference is detected, and the presence or absence of breakage (damage) D of the strand 101 is inspected by the output difference. As described above, by adopting the differential method using the paired first and second coils 21 and 22, it is possible to detect a local change such as the fold D of the strand 101 with high accuracy. In addition, it is possible to cancel a gradual change such as twisting of a stranded wire as in the present embodiment, and it is also possible to cancel a backlash signal of the fan-shaped coil 2, so that the detection accuracy is further improved.

  As shown in FIGS. 1 and 5, in the present embodiment, the strands 2a of the first and second coils 21 and 22 are fan-shaped (also called horseshoe-shaped or U-shaped) made of a magnetic material such as ferrite, for example. It is wound around the core 2b. For example, in the case of a ferrite core, the relative permeability (μr) is 1000 times larger than that of air (μr≈1), so that leakage from the middle part of the core is suppressed, and the strand 101 is connected from one end 2x of the fan coil 2. It is possible to increase (concentrate) the magnetic flux that passes and travels toward the other end 2y of the fan coil 2. Further, since the total magnetic flux is increased by using the core 2b made of a magnetic material, the generated eddy current is increased, the detection signal is increased, and the inspection accuracy is improved. In the present embodiment, the central angle of the coil 2 (core 2b) is 180 °.

  The first and second coils 21 and 22 are held at predetermined positions with respect to the center of the cable 100 by a jig 10 as shown in FIGS. The jig 10 includes an openable / closable main body 11 in which the first and second coils 21 and 22 are embedded, and a concave portion 12 in which the cable 100 is fitted and held (clamped) in the center of the main body 11. Thereby, the extreme fluctuation | variation of the liftoff of the 1st, 2nd coils 21 and 22 and the strand 101 is suppressed, and relative positional relationship (the circumferential direction and radial direction) is made constant. The jig 10 also functions as a scanning unit that holds the first and second coils 21 and 22 so as to be movable relative to the cable 100 in the axial direction A of the strand 101. Note that the predetermined gap G in the present embodiment includes the thickness (wall thickness) G1 of the covering material 102 and the gap G2 between the coil 2 and the cable 100, which is the lift-off distance.

As shown in FIG. 3, the eddy current flaw detector 3 generally includes an oscillator 31 as an AC application unit, a power amplifier 32, a bridge circuit 33, an amplifier 34, a synchronous detector 35, a phase shifter 36, and a filter 37. As shown in FIG. 4, the bridge circuit 33 includes a fixed resistor 33a (resistance Z ₁ ), a variable resistor 33b (resistance Z ₂ ), a first coil 21 (impedance Z ₃ ), and a second coil 23 (impedance Z _4). ).

  The AC output from the oscillator 31 is applied to the fixed resistor 33a, the variable resistor 33b, and the self-inductive first and second coils 21 and 22 of the bridge circuit 33 via the power amplifier 32. And impedance difference (DELTA) Z (Z3-Z4) of the 1st, 2nd coils 21 and 22 is output as voltage change (DELTA) V.

  The unbalanced output between the first and second coils 21 and 22 is amplified by the amplifier 34, sent to the synchronous detectors 35a and 35b, and detected together with the outputs of the phase shifters 36a and 36b. Then, the eddy current signal is taken into the signal processing device 4 via the filters 37 a and 37 b and an A / D converter (not shown), and the measurement result is displayed on the display 5. The signal processing device 4 is configured by a personal computer (PC) connected to the eddy current flaw detector 3, for example. In the present embodiment, a recorder 7 is connected to the eddy current flaw detector 3 via a rejection means 6.

  By the way, the impedance Z of the coil 2 (first and second coils 21 and 22) is represented by the following expression in the complex number display.

Since ω = 2πf, 1 / ωC becomes extremely small when the frequency f is high, and can be ignored when the object is a conductor such as a metal material. Here, the carbon fiber 101a constituting the strand 101, which is the inspection object of the present embodiment, has a conductivity as small as 1/10 ⁴ in the strand direction (axial direction) compared to metal, but the electromagnetic induction phenomenon. As a result, an induced current (eddy current) is generated in the axial direction A. On the other hand, the conductivity in the direction orthogonal to the axial direction A (circumferential direction C) is as small as 1/10 ⁸ compared to metal, and almost no induced current (eddy current) flows in the circumferential direction C. That is, the strand 101 is a conductor having conductivity in the axial direction A. Therefore, in the present invention, the impedance change only needs to take into account the resistance R and reactance ωL of the strand (winding) 2a in Equation 1 above.

  Here, since the strand 2a is wound around the core 2b so that the central axis of the coil 2 (first and second coils 21, 22) is along the circumferential direction C of the cable 100, FIG. As shown, the portion 2 a 1 located on the cable 100 side of the wire 2 a wound around the core 2 b is disposed along the axial direction A of the strand 101. Thereby, the eddy current E can be generated along the axial direction A on the outer peripheral surface 101 x of the strand 101.

  Further, when the coil 2 is arranged on the cable 100 including the strand 101 composed of the carbon fiber 101a and an alternating current is passed, the magnetic flux F (indicated by a broken line in the drawing) is generated from the other end 2y of the core 2b (coil 2). It flows in a concentrated manner inside the core 2b without leaking between the one end 2x (core intermediate portion). The magnetic flux F leaks from one end 2x of the core 2b to the space, but concentrates on the magnetic path M having the shortest distance from the one end 2x to the other end 2y of the core 2b. Therefore, although the magnetic field is increased in the magnetic path M, the apparent magnetic resistance is increased, so that a part of the magnetic flux is curved and spreads, and the magnetic flux (magnetic field) acts on the entire cable 100.

  The eddy current E generated by the magnetic flux F generates a magnetic flux in a direction that cancels the change in the magnetic flux F. Therefore, for example, even if the magnetic path M with the shortest distance is positioned so as to pass (cross) the strand 101 at the center of the cable 100, the magnetic flux generated by the eddy current E generated on the outer peripheral surface 101x is caused at the center of the cable 100. It is presumed that the magnetic flux (magnetic field) is canceled and becomes smaller.

  Thus, the inventors conducted a magnetic flux density distribution simulation experiment on the relationship between the shape of the coil 2 (core 2b) and the spread of the magnetic flux F. The result is shown in FIG. In this simulation, as shown in FIG. 10, the cable 100 having a diameter d = φ12 mm is used as an object, and the distance separated toward the cable 100 with respect to the axial center 2n of the coil 2 (core 2b) is defined as the coil. It was set as the distance (mm) from the surface.

  As shown in FIG. 9, when the central angle θ1 = 180 ° of the coil 2 (core 2b1), the magnetic flux density increased at a point where the distance L from the coil surface was about 4.9 mm (strength). When the central angle θ2 = 120 ° (core 2b2), the same distance L is about 0.9 mm (strength), and when the central angle θ3 = 90 ° (core 2b3), the same distance L is about 0 mm ( Strength increased at each point. Thus, by adjusting the central angle θ of the coil 2, the magnetic flux passing from the one end 2 x of the coil 2 through the strand 101 to the other end 2 y according to the gap G (lift-off distance) such as the thickness of the covering material 102. F can increase the magnetic flux density (intensify the magnetic field) in the vicinity of the outer peripheral surface 101x of the strand 101.

  In particular, in the case of the strand 101 made of the fiber-reinforced composite material to be inspected in the present embodiment, the fold D of the strand 101 first occurs on the outer peripheral surface 101x of the strand 101 located on the outside. As described above, since the magnetic flux can be made dense (intensify the magnetic field) in the vicinity of the outer peripheral surface 101x of the strand 101, the center of the coil 2 can be selected according to the cable diameter, the thickness of the covering material 102, etc. (gap G). By adjusting the angle θ, the initial state of the fold D of the strand 101 can be detected. Moreover, since the magnetic flux in the vicinity of the outer peripheral surface 101x of the strand 101 is made dense in the strand 101 having a lower conductivity than that of the metal, the eddy current E can be increased and the inspection accuracy is good.

Here, the inspection method of the cable 100 according to the present invention will be described.
First, the strand 101 passes through the strand 101 from one end 2x of the coil 2 in consideration of the thickness G1 of the covering material 102 of the cable 100 to be inspected and the gap G including the gap G2 (contact state) between the coil 2 and the cable 100. Then, the central angle θ of the coil 2 (core 2b) is determined (adjusted) so that the magnetic flux F toward the other end 2y of the coil 2 becomes dense near the outer peripheral surface 101x of the strand 101. Next, a normal product (only a healthy part) and a damaged product (with a damaged part D) are prepared using the same type as the cable 100 as a reference test body, and the test frequency, phase, gain, filter, Determine inspection conditions such as flaw detection speed. The phase is adjusted so that the backlash signal and the flaw signal appear in the X direction or the Y direction. Further, the damaged product is a product in which part or all of the strand 101 in the cable 100 is broken.

  A signal is measured with a reference specimen under the set inspection conditions, and a threshold value (absolute value or pp value) is set from the measurement data. For example, a signal level that is larger than the maximum value of the measurement data of the normal product illustrated in FIG. 11A and smaller than the flaw signal of the damaged product illustrated in FIG. Set. Then, for example, as shown in FIG. 7, the first and second coils 21 and 22 are inserted (clamped) by the jig 10 with a gap G with respect to the outer peripheral surface 101x of the strand 101. The bridge of the first and second coils 21 and 22 is balanced. Then, an AC voltage is applied to the fan-shaped coil 2 to generate an eddy current E along the axial direction A on the outer peripheral surface 101x of the strand 101 by electromagnetic induction, and the jig 10 is moved (scanned) in the axial direction A. The signal is measured, and it is determined that a fold D exists when the threshold value is exceeded.

Next, a second embodiment of the present invention will be described. In the following embodiments, the same reference numerals are given to the same members as those in the first embodiment.
In the first embodiment, the coil 2 is a fan coil that has a fan shape covering a part of the outer peripheral surface 101 x (cable 100) of the strand 101. However, as long as the coil 2 can be arranged with a predetermined gap G so that the magnetic flux F is dense in the vicinity of the outer peripheral surface 101x of the strand 101 (near the surface of the inspection object), it is not limited to a fan-shaped coil. .

  In the example shown in FIG. 12, the core 2 b ′ has a substantially U shape in cross section, and the end portions 2 x ′ and 2 y ′ protrude toward the cable 100 and face each other. The strand 2a is formed from one end 2x ′ of the coil to the other end 2y ′ in order to generate an eddy current E along the axial direction (constant direction) on the outer peripheral surface 101x (surface) of the strand 101 (inspection object). The magnetic flux F is wound so that it passes through the strand 101. Then, the coil 2 'is arranged with a predetermined gap G (the thickness G1 of the covering material 102 and the space G3) with respect to the outer peripheral surface 101x of the strand 101 so that the magnetic flux F is dense in the vicinity of the outer peripheral surface 101x. As a result, by applying an alternating voltage to the coil 2b ', it is possible to detect the break D of the strand 101 as in the above embodiment.

  Furthermore, it is not limited to a substantially U-shaped cross-sectional view, and for example, a rectangular coil 2 ″ as shown in FIG. 13 can be similarly inspected. According to the simulation result shown in FIG. 9, the distance L from the coil surface is The magnetic flux density increased at a point of about 0 mm (strength). In addition, according to this 2nd embodiment, it can test | inspect not only the test object like the cable 100 but the thing which consists of a material which has electroconductivity in a fixed direction, for example, a flat form. The element wire 2a causes the magnetic flux F from the one end 2x to the other end 2y of the coil 2 to pass through the inspection object 101 in order to generate an eddy current E along a certain direction on the outer peripheral surface 101x of the inspection object 101. It is good that it is wound to do.

Finally, reference is made to the possibilities of yet another embodiment of the invention.
In the first embodiment, the coil 2 (first and second coils 21 and 22) has one self-inductive coil having a central angle θ of 180 °. However, the number of coils 2 (first and second coils 21 and 22) is not limited to one, and two or more (a plurality) may be used. For example, as shown in FIG. 14, the self-inductive coils 2 and 2 having a central angle θ of 180 ° may be arranged symmetrically with a gap with respect to the cable 100. Thereby, the strand 101 of the cable 100 part (location where lift-off is small) where each coil 2 and 2 is close to itself can be inspected, and the entire circumference of the cable 100 can be inspected by one scan, and the inspection efficiency is improved. Of course, the present invention is not limited to a pair, and for example, four self-inductive coils 2 having a central angle θ of 90 ° can be arranged substantially point-symmetrically with respect to the center of the cable 100.

  Furthermore, in the example of FIG. 14, a pair of coils 2 are arranged in the same circumferential direction C. However, the present invention is not limited to this, and each coil 2 can be arranged by shifting the circumferential position at different positions in the axial direction A. . For example, as shown in FIG. 15, the coil 2 having a central angle θ of 120 ° may be arranged at a different position in the axial direction A of the cable 100 and shifted in the circumferential direction C. Also in this example, since the entire circumference of the cable 100 can be covered by the three coils 2, the fold D of each strand 101 can be detected by one scan.

  In addition, if the coil 2 can be held so as to be relatively movable in the axial direction A of the cable 100 (strand 101) and the extreme variation in lift-off between the coil 2 and the strand 101 can be suppressed, the aspect of the jig 10 is The present invention is not limited to the first embodiment. With the jig 10 of the first embodiment, even if the cable 100 is incorporated in the apparatus, measurement (maintenance inspection) can be performed without removing the cable 100 from the apparatus. On the other hand, if the inspection is performed at the time of manufacturing the cable 100, for example, it is possible to move the cable 100 with the coil 2 (the jig 10) fixed and the cable 100 being inserted. It is conceivable to use a donut-shaped coil 2 that covers the surface. However, in the donut-shaped coil, it becomes an endless solenoid, and the magnetic flux F hardly leaks outside the coil, so that the eddy current E is extremely reduced and the inspection becomes difficult. That is, the coil 2 needs to have at least a gap (gap) between the one end 2x and the other end 2y.

  In each of the above embodiments, the coil 2 is configured by winding the wire 2a around the core 2b made of ferrite. However, the core 2b is not limited to a ferrite core, and may be another magnetic material. According to the experiments by the inventors, even when the core 2b is omitted, as shown in FIG. 16, the magnetic flux F passing from the one end 2x of the coil 2 through the strand 101 to the other end 2y of the coil 2 is It has been found that the inspection is possible by adjusting the central angle θ of the coil 2 so as to be dense in the vicinity of the outer peripheral surface 101x. However, when these results are compared, the magnetic flux density decreases more gradually when the core 2b is provided and the distance L increases. Also in this respect, the first embodiment is superior in terms of accuracy because the magnetic flux increases and the eddy current increases when the core 2b is used.

  In each of the above embodiments, the flaw signal and the noise signal are separated (in the X direction and the Y direction) and inspected. However, since the eddy current E is generated in the axial direction (constant direction) of the strand 101 (inspection object), the flaw signal S1 and the noise signal S2 have different directions. Therefore, the Lissajous waveform as shown in FIG. It is also possible to detect (determine) the presence or absence of a defect.

  In each of the above embodiments, the cable 100 is configured by twisting the six strands 101 around the central strand 101 and twisting them together, and the outer periphery of the twisted wire is made of resin such as vinyl chloride. It was configured to be covered with a covering material 102 made of a material. However, the inspection object is not limited to this. For example, as shown in FIGS. 18 (a) and 18 (c), even a cable 100 composed of one strand 101 or 19 strands 101 can be inspected.

  Moreover, as shown in FIG. 18, the thing without the covering material 102 may be sufficient. As described above, if there is a gap G between the outer peripheral surface 101x of the strand 101 and the coil 2, the inspection is possible. It is not always necessary to keep the coil 2 and the outer peripheral surface 101x of the strand 101 in close contact, and inspection can be performed at high speed in a non-contact state. In the above embodiment, the carbon fiber reinforced plastic (CFRP) has been described as an example of the fiber reinforced composite material. However, the present invention is not limited to this, and for example, a fiber reinforced fiber having the above-described electrical characteristics such as silicon carbide fiber. It may be a composite material (fiber material).

  In each of the above embodiments, the inspection apparatus 1 is composed of the eddy current flaw detection apparatus 3, the signal treatment apparatus 4 (personal computer) as a determination means, and the display 5. However, the present invention is not limited to this mode. For example, the inspection apparatus 1 can be configured by an eddy current flaw detector including the determination unit 4 and the display unit 5. In each of the above embodiments, a self-inductive differential method is employed, but the present invention is not limited to this. However, the differential method is superior in terms of detection accuracy. In each of the above embodiments, the voltage change is output as the impedance difference, but the value related to the eddy current is not limited to this.

1: defect inspection device, 2: coil, 2a: wire, 2b: core, 2x: one end, 2y: other end, 3: eddy current flaw detector, 4: signal treatment device (determination means), 5: display means, 6: Rejecting means, 7: Recorder, 10: Jig, 21: First coil, 22: Second coil, 31: Oscillator (AC applying means), 32: Power amplifier, 33: Bridge circuit, 33a: Fixed Resistor, 33b: Variable resistor, 34: Amplifier, 35: Synchronous detector, 36: Phase shifter, 37: Filter, 100: High-strength fiber composite cable, 101: Strand, 101a: Carbon fiber, 101b: Resin , 101x: outer peripheral surface, 102: coating material, A: axial direction, C: circumferential direction, D: damage (folding), E: eddy current, F: magnetic flux, G: gap, M: shortest magnetic path

Claims (15)

A defect inspection method for inspecting the presence or absence of a defect in the inspection object by applying an alternating voltage to a coil formed by winding an element wire and measuring a value caused by eddy current generated in the inspection object by electromagnetic induction. And
The inspection object is made of a material having conductivity in its axial direction,
The strand is wound so that the central axis of the coil is along the circumferential direction of the inspection object,
The coil has a fan shape covering a part of the outer peripheral surface of the inspection object,
When the fan-shaped coil is disposed with a predetermined gap with respect to the outer peripheral surface, the magnetic flux passing from the one end of the fan coil to the other end of the fan-shaped coil through the inspection object is densely adjacent to the outer peripheral surface. Adjust the central angle of the fan coil so that
The fan coil is arranged with a predetermined gap with respect to the outer peripheral surface,
Applying the AC voltage to the fan-shaped coil to cause an eddy current along the axial direction of the inspection object on the outer peripheral surface by the electromagnetic induction,
Measure the value due to the eddy current with the fan coil,
A defect inspection method for inspecting the presence or absence of a defect on the outer peripheral surface based on the measurement result. The defect inspection method according to claim 1, wherein the fan coil is wound around a fan-shaped core made of a magnetic material. A pair of the fan-shaped coils are provided at an appropriate interval in the axial direction of the inspection object, the pair of fan-shaped coils are relatively moved in the axial direction, and the presence / absence of the defect is inspected based on an output difference between the pair of fan-shaped coils. Item 3. The defect inspection method according to Item 1 or 2. The defect inspection method according to claim 1, wherein a plurality of the fan-shaped coils are arranged along a circumferential direction of the inspection object. The defect inspection method according to claim 1, wherein the inspection object is a single strand made of a fiber-reinforced composite material having conductivity. The defect inspection method according to claim 1, wherein the inspection object is a plurality of strands made of a conductive fiber-reinforced composite material. The defect inspection method according to claim 5, wherein the one strand is covered with a covering material, and the gap includes a thickness of the covering material. The defect inspection method according to claim 6, wherein the plurality of strands are covered with a covering material, and the gap includes a thickness of the covering material. A defect inspection apparatus that inspects the presence or absence of defects in the inspection object by applying an alternating voltage to a coil formed by winding a wire and measuring a value caused by eddy current generated in the inspection object by electromagnetic induction. And
The inspection object is made of a material having conductivity in its axial direction,
The strand is wound so that the central axis of the coil is along the circumferential direction of the inspection object,
The coil has a fan shape covering a part of the outer peripheral surface of the inspection object, and when the fan coil is arranged with a predetermined gap with respect to the outer peripheral surface, the inspection object starts from one end of the fan coil. The central angle of the fan-shaped coil is adjusted so that the magnetic flux passing through the other end of the fan-shaped coil becomes dense near the outer peripheral surface, and is arranged with a predetermined gap with respect to the outer peripheral surface,
AC applying means for applying the AC voltage to the fan-shaped coil and generating an eddy current along the axial direction of the inspection object by the electromagnetic induction on the outer peripheral surface;
A defect inspection apparatus comprising: a determination unit that measures a value caused by the eddy current with the fan coil and determines the presence or absence of a defect on the outer peripheral surface based on the measurement result. The defect inspection apparatus according to claim 9, wherein the fan-shaped coil is wound around a fan-shaped core made of a magnetic material. The said fan-shaped coil is provided with a pair at appropriate intervals along the axial direction of the said test object, The said determination means test | inspects the presence or absence of the said defect with the output difference of a pair of said fan-shaped coil. Defect inspection apparatus as described. The defect inspection apparatus according to claim 9, further comprising a jig that holds the fan-shaped coil at a predetermined position with respect to a center of the inspection object. The defect inspection apparatus according to claim 12, wherein the jig holds a plurality of the fan coils along a circumferential direction of the inspection object. A defect inspection method for inspecting the presence or absence of a defect in the inspection object by applying an alternating voltage to a coil formed by winding an element wire and measuring a value caused by eddy current generated in the inspection object by electromagnetic induction. And
The inspection object is made of a material having conductivity in a certain direction,
The strand is wound so that a magnetic flux from one end of the coil to the other end passes through the inspection object in order to generate an eddy current along the predetermined direction on the surface of the inspection object. ,
The coil is arranged with a predetermined gap with respect to the surface so that the magnetic flux is dense near the surface,
Applying the alternating voltage to the coil to cause an eddy current along the fixed direction on the surface by the electromagnetic induction;
Measure the value due to the eddy current with the coil,
A defect inspection method for inspecting the presence or absence of defects on the surface based on the measurement result. A defect inspection apparatus that inspects the presence or absence of defects in the inspection object by applying an alternating voltage to a coil formed by winding a wire and measuring a value caused by eddy current generated in the inspection object by electromagnetic induction. And
The inspection object is made of a material having conductivity in a certain direction,
The strand is wound so that a magnetic flux from one end of the coil to the other end passes through the inspection object in order to generate an eddy current along the predetermined direction on the surface of the inspection object. ,
The coil is arranged with a predetermined gap with respect to the surface so that the magnetic flux is dense near the surface,
AC applying means for applying the AC voltage to the coil to generate an eddy current in the fixed direction by the electromagnetic induction on the surface;
A defect inspection apparatus comprising: a determination unit that measures a value caused by the eddy current with the coil and determines the presence or absence of a defect on the surface based on the measurement result.

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