JP4031958B2 - Magnetic material bending portion fracture inspection method and inspection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic material bent portion break inspection method and a magnetic material bent portion break inspection apparatus. More specifically, the present invention relates to a magnetic material bending portion breakage inspection method and an inspection apparatus for inspecting a breakage in a bending portion of a rod-like magnetic material such as a reinforcing bar covered with a covering such as concrete.
[0002]
[Prior art]
Stresses are likely to concentrate at the corners of reinforced concrete and bent portions of reinforced concrete, and breakage tends 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 bent portion break inspection method and a magnetic material bent portion break inspection apparatus capable of detecting a break in a bent portion of a magnetic material at a low cost by a nondestructive method in view of the conventional situation. There is.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the magnetic material bent portion fracture inspection method according to the present invention is characterized by a method for inspecting a fracture in a bent portion of a rod-shaped magnetic material covered with a covering, wherein the bent portion is The rod-shaped magnetic material is bent in the vicinity of the corner of the covering, and a detection head for detecting a change in magnetic flux due to excitation of the excitation core is provided in the vicinity of a pair of ends of the excitation core, and the magnetic A pair of end portions of the exciting core are oriented along the longitudinal direction of the material, and the bar-like magnetism intersects with the planar portion of the covering body where the detecting head moves together with the detecting head while exciting the exciting core. The rupture is inspected based on the detection result of the magnetic flux change using the detection head in the vicinity of the bent portion by moving the detection head beyond the position of the material to the release side of the corner. It lies in the fact.
[0005]
The inspection method is effective when the bar-shaped magnetic material is a reinforcing bar and the covering is concrete.
[0006]
Moreover, in the said inspection method, you may test | inspect by moving the said detection head toward the corner | angular part from the plane part of a reinforced concrete structure.
[0007]
Furthermore, a pair of the detection heads having the excitation core may be connected, and one detection head may be disposed on the streak so as to obtain a difference between signals obtained from both heads.
[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, in which a change in magnetic flux due to excitation of the excitation core is detected in the vicinity of a pair of end portions of the excitation core. A detection head for detection is provided, and the detection head detects a change in magnetic flux caused by a relative relationship between the pair of end portions and the rod-shaped magnetic material being different between the pair of end portions.
[0009]
Moreover, you may make it have a detection head position adjustment tool which adjusts the relative relationship between the said detection head and a pair of said edge part.
[0010]
In each of the above examples, it is desirable 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 covered with a covering, a magnetic material capable of detecting a fracture at a bent portion of the magnetic material at a low cost by a non-destructive technique. It has become possible to provide a bending portion breakage inspection method and a magnetic material bending portion breakage inspection apparatus.
[0012]
Other objects, configurations, and effects of the present invention will become apparent from the embodiments described below.
[0013]
DETAILED DESCRIPTION OF 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 that constitutes a pier of a road bridge and the like will be described as an example to be inspected.
[0014]
As shown in FIG. 1, a detection head 10 that performs inspection along the surface of a reinforced concrete structure H that is a test body includes an excitation core 11 and an excitation coil 12 that generate magnetic flux for exciting the reinforcing bar S2, and changes in magnetic flux. The detection core 13 and the detection coil 14 are detected. In this embodiment, a substantially U-shaped excitation core 11 is used, and the excitation core 11 and the excitation coil 12 are positioned between both end portions 11a and 11b 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. Position adjustment plates 16 are provided at both end portions 11a and 11b of the excitation core 11, and the excitation core 11, the detection core 13 and the detection are detected by a position adjustment tool 17 including the adjustment plate 16 and the spacer 15. The relative position with respect to the coil 14 can be adjusted. At the time of 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 position adjustment plates 16 is adjusted at two locations 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 this inspection device 1, an alternating current generated by an oscillator 2 and amplified by a power amplifier 3 is applied to an exciting coil 12 to generate a magnetic flux. On the other hand, the magnetic flux change 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, synchronous detection is performed by the lock-in amplifier 7 and a Lissajous is obtained by decomposing the detected waveform into X and Y components orthogonal to each other, 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 object, 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 a main reinforcement S1 and a band S2. The band S2 which is an example of the rod-shaped magnetic material is bent in the vicinity of the corner of the reinforced concrete structure H, and stress tends to concentrate on the bent portion Sc, and it is more likely to break than 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 arranged on the upper surface of the reinforced concrete structure H, and the detection head 10 is caused to travel from the flat surface side to the corner side of the reinforced concrete structure. 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 actual inspection, only one of the modes indicated by the symbols 10a and 10b may be performed, or both of them may be used in combination. Further, the traveling direction of the detection head 10 is not limited to the case where the detection head 10 is brought closer to the corner of the reinforced concrete structure H, but may be a direction 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 have placed an acrylic plate C ′ as a covering on the upper part of the healthy reinforcing bar S2 shown in FIG. 5 and the fracture shown in FIG. An experiment was performed for each of the cases where the 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, the Lissajous is not drawn but displayed as a point in the vicinity of the XY coordinate origin, whereas when the coil is in an unbalanced state, a curve (Lissajous) is drawn. In the embodiment, Lissajous is displayed to evaluate data that is affected by the bent portion Sc from the inspection waveform.
[0020]
7 and 8 depict the Lissajous displayed on the display 8 when the magnetic flux affected by the bent portion Sc of the band S2 is detected among the Lissajous obtained as a result of the above experiment. 7 is a Lissajous case when the cover thickness T of the acrylic plate is 20 mm, and FIG. 8 is a Lissajous case when the cover thickness T of the acrylic plate is 30 mm. In both figures, the Lissajous indicated by the symbol fa is a Lissajous obtained when a healthy reinforcing bar is used, and the Lissajous indicated by the symbol fb is a Lissajous obtained when a fractured reinforcing bar is used. From these two figures, it was confirmed that there was a difference in the shape of the Lissajous between the case of healthy reinforcing bars and the case of fractured reinforcing bars.
[0021]
Considering these differences, in the healthy reinforcing bar of FIG. 5, even if the one end 11b of the core moves further to the release side, the magnetic flux lines of the magnetic flux indicated by the symbol M pass through the band S2, so that the unbalanced output is maintained. Is done. On the other hand, in the broken reinforcing bar shown in FIG. 6, a leakage magnetic flux is generated from the broken portion D, so that the unbalanced output disappears before the one end 11b is largely released. The difference in Lissajous is considered to be due to the difference in properties of these unbalanced outputs.
[0022]
Next, a second embodiment of the present invention will be described with reference to FIGS. In the following embodiments, members similar to those in the above embodiments are denoted by the same reference numerals.
[0023]
As shown in FIG. 9, the present embodiment is different from the above-described 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 magnetic induction core 11. In the present embodiment, the diameter of the detection coil 22 can be made longer than the gap between the magnetic induction cores 11. Therefore, the spatial detection area is expanded, the detection sensitivity is improved, and a specimen having a larger cover thickness can be dealt with.
[0024]
As shown in FIGS. 9 and 10, both end portions 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. Similarly to the above embodiment, the detection core 21 and the spacer 23 constitute the detection coil position adjuster 24. In the inspection, the position adjuster 24 is used to detect the detection coil as in the first embodiment. The relative position is adjusted so that the output of 23 is 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 in that the detection head 30 includes two detection coils 31 and 32. As shown in FIG. 11, the present embodiment includes a first detection coil 31 and a second detection coil 32 at both ends 11 a and 11 b of the induction core 11, and the first and second coils 31 and 32. By detecting this unbalance, the broken portion D of the band 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 source 36. In the inspection, the variable resistors 33 and 34 are appropriately adjusted so that no output is generated when the exciting core 11 is released. On the other hand, when the magnetic flux from the corner portion Sc of the specimen is captured, the balance of the bridge 37 is lost, and a voltage corresponding to the impedance change is output from the detector 35 to the amplifier 5, and the output signal The rupture part D is detected by the property.
[0027]
FIG. 13 depicts a detected waveform obtained by an experiment conducted by the inventors in order to confirm the usefulness of the present embodiment. FIG. 13 (a) shows a healthy rebar, and FIG. It is a detection waveform at the time of using a broken rebar 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 part Sc of the band S2.
[0028]
Comparing the detected waveforms in FIGS. 4A and 4B, it can be seen that the maximum amplitude P1 (end signal) of the inspection 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 reinforcing bars can be detected from the maximum amplitude values P1 and P2 of the detected waveform. It was also confirmed that the breakage portion D in the band S2 can be detected regardless of the presence of the main bar S1.
[0029]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In this embodiment, the detection head 20 of the second embodiment shown in FIG. 9 is used as a pair 20a and 20b 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 so that the end portions 11a and 11b in FIG. 9 are parallel between the pair of detection heads 20a and 20b. And fixed to the connecting plate 25 formed of resin or the like.
[0030]
The pair of 20a and 20b moves the surface of H to the front side in FIG. 14 and inspects Sc. One first detection head 20a moves along the band S2 to detect signals of both the main muscle S1 and the band 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 provided in parallel for each of the pair of detection coils 22 a and 22 b, and the difference between the detection coils 22 a and 22 b is displayed on the display 8. The Thereby, it becomes possible to detect the presence or absence of the rupture portion D with higher accuracy from the difference signal of only the band S2 from which the influence of the main muscle S1 has been removed.
[0031]
FIG. 16 shows the test results having the same purpose as in FIGS. FIG. 16A shows a detection waveform by the first detection head 20a in the healthy part, FIG. 16B shows a detection waveform by the second detection head 20b having only the main muscle, and FIG. 16C shows a difference between (a) and (b). On the other hand, FIG. 16 (d) shows a detection waveform by the first detection head 20a at the fracture portion, (e) shows a detection waveform by the second detection head 20b with only the main muscle, and (f) shows a difference between (d) and (e). . Comparison of FIGS. 16C and 16F reveals that the characteristic waveforms of the healthy part and the fractured part 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 combined with each other.
[0033]
In each said embodiment, the reinforced concrete structure was used as a test object. However, the covering is not necessarily limited to synthetic resin or concrete, but may be any material that can transmit magnetic flux. Further, the rod-shaped magnetic material is not limited to the reinforcing bar.
[0034]
In each of the above-described embodiments, the case where the fracture at the bent portion of the band reinforcing bar is detected has been described. However, the fracture at the flat portion of the reinforcing bar can also be detected at the same time.
[0035]
In the above embodiments, the detection cores 13 and 21 and the detection coils 14, 22, 31, and 32 are used for the detection heads 10, 20, and 30. However, as this 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 it can easily expand the area of the magnetic detection surface and can cope with a deep cover thickness.
[0036]
The shape of the exciting core 11 only needs to have at least a pair of end portions facing the same side. Various modifications are possible for other shapes.
[0037]
In addition, the code | symbol entered in the term of the claim is only for the convenience of contrast with drawing, and this invention is not limited to the structure of an accompanying drawing by this entry.
[Brief description of the drawings]
FIG. 1 is a cutaway sectional view of a detection head in a first embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA of FIG.
FIG. 3 is a block diagram of an inspection apparatus.
FIG. 4 is a cross-sectional view showing a relationship between a broken portion of a reinforcing bar and a detection head.
FIG. 5 is a diagram showing a magnetic flux path at the time of inspection of a healthy reinforcing bar.
FIG. 6 is a diagram showing a magnetic flux path at the time of inspection of a broken reinforcing bar.
FIG. 7 is a Lissajous at the time of rebar inspection when the cover thickness of the acrylic plate is T = 20 mm.
FIG. 8 is a Lissajous at the time of rebar inspection when the cover thickness of the acrylic plate is T = 30 mm.
FIG. 9 is a cutaway sectional view of a detection head in a second embodiment of the present invention.
FIG. 10 is a plan view of a detection head in a second embodiment of the present invention.
FIG. 11 is a diagram showing a relationship between a detection head and a damaged portion of a reinforcing bar in the third embodiment of the present invention.
FIG. 12 is a diagram illustrating a bridge circuit.
13A and 13B are diagrams showing detection waveforms, where FIG. 13A corresponds to a case of a healthy reinforcing bar, and FIG. 13B corresponds to a case of a broken reinforcing bar.
FIG. 14 is a diagram showing a relationship between a detection head and a damaged portion of a reinforcing bar in the fourth embodiment of the present invention.
15 is a block diagram of the inspection apparatus in FIG.
16A and 16B are diagrams showing detection waveforms, in which FIG. 16A shows a detection waveform by the first detection head of the healthy part, FIG. 16B shows a detection waveform by the second detection head of the main muscle only, and FIG. The difference of b), (d) is the detection waveform by the first detection head of the fracture portion, (e) is the detection waveform by the second detection head of the main muscle only, and (f) is the difference of (d) and (e).
[Explanation of symbols]
1: Reinforcing bar breakage 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 adjustment tool, 25: Connecting plate, 30: Detection head, 31, 32: Detection coil, 33, 34: Variable resistance 35: Detector, 36: AC power source, 37: Bridge circuit, C: Concrete (covered body), C ': Acrylic plate, D: Broken part, H: Reinforced concrete structure, S1: Main reinforcement, S2 : Band reinforcement, Sc: Bending part, T: Cover thickness, M: Magnetic field line

Claims (8)

A magnetic material bending portion break inspection method for inspecting a break in a bending portion of a rod-shaped magnetic material covered with a covering,
The bent portion is formed by bending the rod-shaped magnetic material in the vicinity of the corner portion of the covering, and a detection head for detecting a change in magnetic flux due to excitation of the excitation core is provided in the vicinity of a pair of end portions of the excitation core. Provided, orienting a pair of end portions of the exciting core along the longitudinal direction of the magnetic material, and intersecting the planar portion of the covering body in which the detecting head moves together with the detecting head while exciting the exciting core. Bending of the magnetic material for inspecting the breakage based on the detection result of magnetic flux change using the detection head in the vicinity of the bent portion by moving the detection head beyond the position of the bar-shaped magnetic material in the direction to the release side of the corner Partial break inspection method.   The method for inspecting a bent portion of a magnetic material according to claim 1, wherein the bar-shaped magnetic material is a reinforcing bar and the covering is concrete.   4. The magnetic material bending portion fracture inspection method according to claim 3, wherein the detection head is moved from a flat portion to a corner portion of the reinforced concrete structure.   The magnetic material bending portion fracture inspection method according to claim 1, wherein the detection head has a single detection coil.   The pair of the detection heads having the excitation core are connected, one detection head is arranged on a streak, and a difference between signals obtained from both heads is obtained. The method for inspecting a bent portion of a magnetic material according to the description.   It is a magnetic material bending part breakage inspection apparatus used for the magnetic material bending part breakage inspection method in any one of Claims 1-3, Comprising: The change of the magnetic flux by excitation of this excitation core is carried out near a pair of edge part in an excitation core. A magnetic material bending portion fracture inspection device that includes a detection head for detecting, and detects a change in magnetic flux caused by a difference in relative relationship between the pair of end portions and the rod-shaped magnetic material between the pair of end portions.   The magnetic material bending portion fracture inspection apparatus according to claim 6, further comprising a detection head position adjuster that adjusts a relative relationship between the detection head and the pair of end portions.   The magnetic material bent portion fracture inspection apparatus according to claim 6 or 7, wherein the detection head has a single detection coil.

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