JP2004053496A - Magnetic material bent part rupture inspection method and inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic material bent part rupture inspection method and a magnetic material bent part rupture inspection device capable of detecting rupture at a bent part of a magnetic material at low cost by a nondestructive procedure. <P>SOLUTION: The rupture at the bent part Sc of a long cylindrical magnetic material S2 covered with a covering body C is inspected. A detection head 10 for detecting a magnetic flux change caused by excitation of an excitation core is provided near a pair of ends 11a, 11b of the excitation core. The pair of ends 11a, 11b of the excitation core are oriented along the longitudinal direction of the magnetic material, and the excitation core is excited and simultaneously moved in the far-and-near direction relative to the bent part Sc together with the detection head 10. The rupture is inspected from a detection result of the magnetic flux change by using the detection head 10 near the bent part Sc caused by the movement. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic material bending portion fracture inspection method and a magnetic material bending portion fracture inspection device. More specifically, the present invention relates to a magnetic material bent portion fracture inspection method and an inspection device for inspecting a fracture in a bent portion of a rod-shaped magnetic material such as a reinforcing bar covered with a covering body such as concrete.
[0002]
[Prior art]
At the corners of the reinforced concrete and at the bent portions of the reinforcing bars, stress tends to concentrate and fractures are likely to occur. However, a nondestructive inspection method for detecting breakage in such a bent portion has not been established.
[0003]
[Problems to be solved by the invention]
The present invention provides a magnetic material bending portion fracture inspection method and a magnetic material bending portion fracture inspection device capable of detecting a fracture at a bending portion of a magnetic material at low cost by a nondestructive technique in view of the conventional situation. It is in.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the feature of the magnetic material bending portion fracture inspection method according to the present invention is a method for inspecting a fracture in a bending portion of a rod-shaped magnetic material covered with a coating, and includes a pair of excitation cores. A detection head for detecting a change in magnetic flux due to excitation of the excitation core is provided near an end of the excitation core, a pair of ends of the excitation core are oriented along a longitudinal direction of the magnetic material, and the excitation core is excited. It is an object of the present invention to inspect the breakage based on a detection result of a magnetic flux change using the detection head in the vicinity of the bent portion caused by moving the magnetic head together with the detection head with respect to the bent portion.
[0005]
The above inspection method is effective when the rod-shaped magnetic material is a reinforcing bar and the coating is concrete.
[0006]
In the above-described inspection method, the inspection may be performed by moving the detection head from a plane portion to a corner portion of the reinforced concrete structure.
[0007]
Further, a pair of the detection heads having the excitation cores may be connected to each other, one of the detection heads may be arranged on a stirrup, and a difference between signals obtained from both heads may be obtained.
[0008]
A feature of the magnetic material bending portion inspection apparatus according to the present invention is an apparatus capable of performing any one of the inspection methods described above, wherein a change in magnetic flux due to excitation of the excitation core is provided near a pair of ends of the excitation core. It is another object of the present invention to provide a detection head for detecting a magnetic flux change caused by a relative relationship between the pair of ends and the rod-shaped magnetic material being different between the pair of ends.
[0009]
Further, a detection head position adjuster for adjusting a relative relationship between the detection head and the pair of end portions may be provided.
[0010]
In each of the above examples, it is preferable that the detection head has a single detection coil.
[0011]
【The invention's effect】
As described above, according to the feature of the present invention, even when the magnetic material is covered with the covering, the magnetic material can detect the breakage at the bent portion of the magnetic material at low cost by a nondestructive method. It has become possible to provide a bending portion fracture inspection method and a magnetic material bending portion fracture inspection device.
[0012]
Other objects, configurations and effects of the present invention will become apparent in the following embodiments.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail with reference to the accompanying drawings.
A first embodiment of the present invention will be described with reference to FIGS. In the embodiment described below, a reinforced concrete structure H constituting a pier or the like of a road bridge will be described as an inspection target.
[0014]
As shown in FIG. 1, a detection head 10 that performs inspection along a surface of a reinforced concrete structure H that is a test body includes an excitation core 11 and an excitation coil 12 that generate a magnetic flux for exciting a reinforcing bar S2, and a change in magnetic flux. A detection core 13 and a detection coil 14 for detecting the In the present embodiment, a substantially U-shaped excitation core 11 is used, and the excitation core 11 and the excitation coil 12 are located between both ends 11 a and 11 b of the excitation core 11.
[0015]
The excitation core 11, the detection core 13 and the detection coil 14 are connected via a spacer 15 as shown in FIG. A position adjusting plate 16 is provided at both ends 11a and 11b of the exciting core 11, and the exciting core 11 and the detecting core 13 and the detecting core 13 are detected by a position adjusting tool 17 composed of the adjusting plate 16 and the spacer 15. The relative position with respect to the coil 14 can be adjusted. In the inspection, the positional relationship between the two is adjusted by the position adjuster 17 so that the detection coil is in an equilibrium state. Specifically, when the detection head 10 is opened and a sine wave is applied to the excitation coil, the number of the position adjustment plates 16 is adjusted at two places so that the amplitude of the detection wave detected by the detection coil becomes zero. do it.
[0016]
FIG. 3 shows a block diagram of the inspection apparatus 1 according to the present invention. In the inspection apparatus 1, an alternating current generated by the oscillator 2 and amplified by the power amplifier 3 is applied to the excitation coil 12 to generate a magnetic flux. On the other hand, the change in magnetic flux captured by the detection coil 14 is amplified by the amplifier 5 connected to the detection coil 14, and then the noise is removed by the filter 6. Then, while performing synchronous detection by the lock-in amplifier 7 and decomposing the detected waveform into X and Y components orthogonal to each other, a Lissajous is obtained, and the Lissajous is displayed on the display 8.
[0017]
FIG. 4 shows the relationship between the reinforced concrete structure H, which is an example of the inspection target, and the detection head 10. The reinforced concrete structure H to be inspected in the present embodiment is formed by filling and covering concrete C in a reinforced structure composed of the main reinforcement S1 and the band reinforcement S2. The band S2, which is an example of the bar-shaped magnetic material, is bent near the corner of the reinforced concrete structure H, and stress is easily concentrated on the bent portion Sc, and it is easily broken as compared with other portions. In the present embodiment, the inspection of the bent portion Sc of the band S2 is mainly performed.
[0018]
As an inspection procedure, as shown by reference numeral 10a in FIG. 4, the detection head 10 is disposed on the upper surface of the reinforced concrete structure H, and the detection head 10 runs from the flat surface side to the corner portion side of the reinforced concrete structure H. In some cases, the detection head 10 is disposed on the side surface of the reinforced concrete structure H, and the detection head 10 runs from the lower side to the upper side, as indicated by reference numeral 10b. In an actual inspection, only one of the aspects indicated by reference numerals 10a and 10b may be performed, or both may be used in combination. Further, the traveling direction of the detection head 10 may be not only the case of approaching the corner of the reinforced concrete structure H but also the direction of moving away from the corner.
[0019]
In order to verify the usefulness of the inspection apparatus and the inspection method according to the present invention, the inventors dispose an acrylic plate C ′ as a cover on a sound reinforcing bar S2 shown in FIG. An experiment was performed for each of the cases where an acrylic plate C ′ was disposed as a covering on the upper part of the reinforcing bar S2. In general, when the coil is in an equilibrium state, a Lissajous is not drawn but is displayed as a point near the origin of the XY coordinate, whereas when the coil is in an unbalanced state, a curve (Lissajous) is drawn. In the embodiment, by displaying a Lissajous, data affected by the bent portion Sc from the inspection waveform is evaluated.
[0020]
FIGS. 7 and 8 illustrate the Lissajous displayed on the display 8 when the magnetic flux affected by the bent portion Sc of the stirrup S2 is detected from the Lissajous obtained as a result of the above experiment. Here, FIG. 7 shows the Lissajous when the cover thickness T of the acrylic plate is 20 mm, and FIG. 8 shows the Lissajous when the cover thickness T of the acrylic plate is 30 mm. In both figures, the Lissajous indicated by reference numeral fa is a Lissajous obtained when a healthy reinforcing bar is used, and the Lissajous indicated by reference numeral fb is a Lissajous obtained when a broken reinforcing bar is used. From these figures, it was confirmed that there was a difference in the shape of the Lissajous between the case of a healthy reinforcing bar and the case of a broken reinforcing bar.
[0021]
Considering these differences, in the healthy reinforcing bar shown in FIG. 5, even if the one end 11b of the core moves further to the release side, the magnetic flux lines indicated by the reference symbol M pass through the strip bar S2, so that the unbalanced output is maintained. Is done. On the other hand, in the fractured reinforcing steel shown in FIG. 6, since the leakage magnetic flux is generated from the fractured portion D, the unbalanced output also disappears before the one end 11b is largely released. The difference in Lissajous is considered to be due to the difference in the nature of these unbalanced outputs.
[0022]
Next, a second embodiment of the present invention will be described with reference to FIGS. In the following embodiments, the same members and the like as those in the above embodiment are denoted by the same reference numerals.
[0023]
As shown in FIG. 9, the present embodiment is different from the above embodiment in that the detection core 21 and the detection coil 22 are wound around the outer peripheral surface of the end portion of the substantially U-shaped magnetizing core 11. In the present embodiment, the diameter of the detection coil 22 can be longer than the gap between the magnetic attraction cores 11. Therefore, the spatial detection area is expanded, the detection sensitivity is improved, and it is possible to cope with a test body having a larger cover thickness.
[0024]
As shown in FIGS. 9 and 10, both ends 11 a and 11 b of the induction core 11 and the detection core 21 are connected via a spacer 23. Further, the detection core 22 is connected to the outer peripheral surface side of the spacer 23, and the detection core 22 is wound along the outer peripheral surface of the detection core 22. Further, in the same manner as in the above embodiment, the detection coil 21 and the spacer 23 constitute the detection coil position adjuster 24. In the inspection, as in the first embodiment, the detection coil is adjusted by the position adjuster 24. The relative position is adjusted so that the outputs of the terminals 23 are in an equilibrium state.
[0025]
Next, a third embodiment of the present invention will be described with reference to FIGS. The present embodiment is different from the first embodiment in that the detection head 30 includes two detection coils 31 and 32. In the present embodiment, as shown in FIG. 11, a first detection coil 31 and a second detection coil 32 are provided at both ends 11a and 11b of the magnetic induction core 11, and these first and second coils 31 and 32 are provided. By detecting the unbalance of the belt rebars, the broken portion D of the belt reinforcing bar 32 is detected.
[0026]
FIG. 12 shows a bridge circuit 37 constituted by the first and second detection coils 31 and 32. The bridge circuit 37 includes first and second detection coils 31 and 32, variable resistors 33 and 34, a detector 35, and an AC power supply 36. In the inspection, the variable resistors 33 and 34 are appropriately adjusted so that no output is generated when the excitation core 11 is released. On the other hand, when the magnetic flux from the corner Sc of the test object is captured, the balance of the bridge 37 is lost, and a voltage corresponding to the change in impedance is output from the detector 35 to the amplifier 5, and the output signal is output. The broken portion D is detected according to the properties of.
[0027]
FIGS. 13A and 13B show detection waveforms obtained by experiments performed by the inventors to confirm the usefulness of the present embodiment. FIG. 13A shows a sound reinforcing bar, and FIG. It is a detection waveform at the time of using a fractured reinforcing bar as a test piece. In the experiment, as shown in FIG. 11, an acrylic plate C ′ having a thickness of 50 mm was disposed on the upper part of the band S2, and the detection head 30 was scanned on the upper surface thereof toward the bent portion Sc of the band S2.
[0028]
Comparing the detected waveforms in FIGS. 7A and 7B, it can be seen that the maximum amplitude P1 (end signal) of the test waveform in the case of a healthy reinforcing bar is larger than the maximum amplitude P2 of the broken reinforcing bar. Therefore, it was confirmed that the breakage of the rebar can be detected from the maximum amplitude values P1 and P2 of the detected waveform. In addition, it was confirmed that the broken portion D in the stirrup S2 can be detected irrespective of the presence of the main streak S1.
[0029]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In this embodiment, a pair of detection heads 20 of the second embodiment shown in FIG. 9 are used as shown in FIG. The right side view of the detection head 20 in FIG. 9 is indicated by reference numerals 20a and 20b in FIG. 14, and these are arranged such that the ends 11a and 11b in FIG. 9 are parallel between the pair of detection heads 20a and 20b. Then, it is fixed to the connecting plate 25 formed of resin or the like.
[0030]
The pair 20a and 20b move the surface of H toward the near side in FIG. 14 and inspect Sc. One of the first detection heads 20a moves along the stirrup S2 to detect both signals of the main streak S1 and the stirrup S2. On the other hand, the other second detection head 20b detects only the signal of the main muscle S1. In FIG. 15, an amplifier 5, a filter 6, and a lock-in amplifier 7 are respectively provided in parallel with a pair of detection coils 22 a and 22 b, and a difference between the detection coils 22 a and 22 b is displayed on the display 8. You. This makes it possible to more accurately detect the presence or absence of the broken portion D based on the difference signal of only the stirrup S2 from which the influence of the main streak S1 is removed.
[0031]
FIG. 16 shows an inspection result having the same meaning as in FIGS. 16A shows a waveform detected by the first detection head 20a of the healthy part, FIG. 16B shows a waveform detected by the second detection head 20b of only the main muscle, and FIG. 16C shows a difference between (a) and (b). On the other hand, FIG. 16D shows a waveform detected by the first detection head 20a at the broken portion, FIG. 16E shows a waveform detected by the second detection head 20b having only the main muscle, and FIG. 16F shows a difference between (d) and (e). . The comparison between FIGS. 16C and 16F revealed that the characteristic waveforms of the sound portion and the broken portion can be easily identified.
[0032]
Finally, reference is made to the possibilities of further embodiments of the invention. Of course, the above embodiments and the following embodiments can be implemented in combination with each other.
[0033]
In each of the above embodiments, a reinforced concrete structure was used as an inspection target. However, the coating is not necessarily limited to a synthetic resin or concrete, but may be any as long as it can transmit magnetic flux. Further, the rod-shaped magnetic material is not limited to the rebar.
[0034]
In each of the above embodiments, the case where the break in the bent portion of the belt reinforcing bar is detected has been described, but it is also possible to detect the break in the flat portion of the reinforcing bar at the same time.
[0035]
In each of the above embodiments, the detection cores 13, 21 and the detection coils 14, 22, 31, 32 are used for the detection heads 10, 20, 30. However, as the detection head, for example, a magnetic detection element such as a Hall element can be used. However, the configuration using the coil is superior in that the area of the magnetic detection surface can be easily expanded and a deep cover thickness can be accommodated.
[0036]
The shape of the excitation core 11 may have at least a pair of ends facing the same side. Various modifications are possible for other shapes.
[0037]
It should be noted that reference numerals written in the claims are merely for convenience of comparison with the drawings, and the present invention is not limited to the configuration of the attached drawings by the writing.
[Brief description of the drawings]
FIG. 1 is a cutaway sectional view of a detection head according to a first embodiment of the present invention.
FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a block diagram of an inspection device.
FIG. 4 is a sectional view showing a relationship between a broken portion of a reinforcing bar and a detection head.
FIG. 5 is a diagram illustrating a magnetic flux path during inspection of a healthy reinforcing bar.
FIG. 6 is a diagram showing a magnetic flux path at the time of inspecting a broken reinforcing bar.
FIG. 7 is a Lissajous at the time of rebar inspection when the cover thickness T of an acrylic plate is 20 mm.
FIG. 8 is a Lissajous at the time of rebar inspection when the cover thickness T of the acrylic plate is 30 mm.
FIG. 9 is a cutaway sectional view of a detection head according to a second embodiment of the present invention.
FIG. 10 is a plan view of a detection head according to a second embodiment of the present invention.
FIG. 11 is a diagram illustrating a relationship between a detection head and a damaged portion of a reinforcing bar according to the third embodiment of the present invention.
FIG. 12 illustrates a bridge circuit.
13A and 13B are diagrams showing detected waveforms, where FIG. 13A is a diagram corresponding to a case of a healthy reinforcing bar, and FIG. 13B is a diagram corresponding to a case of a broken bar.
FIG. 14 is a diagram illustrating a relationship between a detection head and a damaged portion of a reinforcing bar according to a fourth embodiment of the present invention.
FIG. 15 is a block diagram of the inspection apparatus of FIG.
FIGS. 16A and 16B are diagrams showing detected waveforms, wherein FIG. 16A shows a detected waveform of a healthy portion by a first detecting head, FIG. 16B shows a detected waveform of a second detecting head having only a main muscle, and FIG. (b), the waveform (d) detected by the first detection head at the broken portion, (e) the waveform detected by the second detection head having only the main muscle, and (f) the difference between (d) and (e).
[Explanation of symbols]
1: rebar fracture inspection device, 2: oscillator, 3: power amplifier, 5: amplifier, 6: filter, 7: lock-in amplifier, 8: display, 10: detection head, 11: excitation core, 11a, 11b: end Part, 12: excitation coil, 13: detection core, 14: detection coil, 15: spacer, 16: position adjustment plate, 17: position adjustment tool, 20: detection head, 20a: first detection head, 20b: second Detection head, 21: detection core, 22, 22a, 22b: detection coil, 23: spacer, 24: position adjuster, 25: connecting plate, 30: detection head, 31, 32: detection coil, 33, 34: variable resistance , 35: detector, 36: AC power supply, 37: bridge circuit, C: concrete (coating), C ': acrylic plate, D: broken part, H: reinforced concrete structure, S1: main reinforcement, S2 : Band, Sc: bent portion, T: cover thickness, M: line of magnetic force

Claims (8)

A method for inspecting a fracture in a bent portion (Sc) of a rod-shaped magnetic material (S2) covered with a coating (C), the method comprising the steps of: 11a, 11b), a detection head (10, 20, 30) for detecting a change in magnetic flux due to excitation of the excitation core (11) is provided, and a pair of the excitation cores (11) is arranged along the longitudinal direction of the magnetic material. The end portions (11a, 11b) are oriented, and while the excitation core (11) is excited, the end portions (11a, 11b) are moved together with the detection heads (10, 20, 30) toward and away from the bent portion (Sc). Sc) A magnetic material bending portion fracture inspection method for inspecting the fracture based on a detection result of a magnetic flux change using the detection head (10, 20, 30) in the vicinity. The method of claim 1, wherein the rod-shaped magnetic material (S2) is a reinforcing bar, and the coating (C) is concrete. 3. The method according to claim 2, wherein the detecting head (10, 20, 30) is moved from a plane portion to a corner portion of the reinforced concrete structure (H). The method according to any one of claims 1 to 3, wherein the detection head (10, 20, 30) has a single detection coil (14, 22). A pair of the detection heads (20, 20a, 20b) having the excitation core (11) are connected, and one of the detection heads (20a) is arranged on the stirrup (S2). 5. The method according to claim 1, wherein a difference between the obtained signals is obtained. A magnetic material bending portion fracture inspection apparatus used in the magnetic material bending portion fracture inspection method according to any one of claims 1 to 3, wherein the excitation core (11) is provided near the pair of ends (11a, 11b) of the excitation core (11). A detection head (10, 20, 30) for detecting a change in magnetic flux due to excitation of the core (11) is provided, and the relative relationship between the pair of ends (11a, 11b) and the rod-shaped magnetic material (S2) is determined by the pair. A magnetic material bending portion breakage inspection apparatus for detecting a change in magnetic flux due to a difference between ends (11a, 11b) of the magnetic material by the detection heads (10, 20, 30). The magnetic device according to claim 5, further comprising a detection head position adjuster (17, 24) for adjusting a relative relationship between the detection head (10, 20, 30) and the pair of end portions (11a, 11b). Material bending part breakage inspection device. The magnetic material bending portion fracture inspection apparatus according to claim 6 or 7, wherein the detection head (10, 20, 30) has a single detection coil (14, 22).

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