JP2016008960A - Nondestructive inspection method and nondestructive inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nondestructive inspection method which hardly receives influence of a non-inspection object such as a ferromagnetic material, and is capable of accurately detecting presence or absence of a fracture part of a steel bar, and a nondestructive inspection device thereof.SOLUTION: When measuring a magnetic flux density at an outer surface of a concrete body 1, a plurality of magnetic sensors 10 are arranged at a plurality of positions A, B, and C with different remote distances from a surface 3 of the concrete body, the plurality of magnetic sensors 10 are moved while maintaining respectively constant remote distances from the surface 3 of the concrete body, and the plurality of magnetic flux densities are measured along a longitudinal direction of a steel bar 2. The magnetic flux densities at two remote distances are appropriately selected from the detected plurality of magnetic densities, the difference between the two magnetic flux densities are obtained, a positive or negative change is determined. With this method, the presence or absence of a fracture part H of the steel bar is accurately detected.

Description

  The present invention relates to a nondestructive inspection method and a nondestructive inspection device for detecting whether or not a reinforcing bar provided in a reinforced concrete structure such as a bridge, a building, or a concrete pole is broken.

Conventionally, there has been known a non-destructive inspection method for detecting breakage of a reinforcing bar provided in a concrete body.
For example, in the nondestructive inspection method described in Japanese Patent No. 3734822 (Patent Document 1), the surface of the concrete body is moved along the longitudinal direction of the reinforcing bar to be inspected embedded in the concrete body. Then, the reinforcing bar is magnetized, the magnetic flux density leaking from the surface of the concrete body is measured by a magnetic sensor, and the differential value of the obtained measured value is calculated to detect the presence or absence of a broken part of the reinforcing bar.

  However, the nondestructive inspection method described in the above-mentioned Patent Document 1 is based on only the differential value of the magnetic flux density measured by a magnetic sensor whose separation distance from the concrete surface is a single magnetic sensor. In order to detect, for example, if the differential value of the magnetic flux density greatly fluctuates due to a ferromagnetic material other than the inspected reinforcing bar embedded in the concrete body or the influence of other environmental magnetic fields, etc. There was a problem that it was difficult to detect accurately. Further, in the non-destructive inspection method described in Patent Document 1, it is necessary to set a threshold value for comparison with a differential value of the measured magnetic flux density in advance, but if the setting threshold value is wrong, There was also a problem that accurate fracture detection could not be performed.

Japanese Patent No. 3734822

As described above, in the conventional nondestructive inspection method, there is a problem that the detection accuracy of the presence or absence of a broken portion of the reinforcing bar is reduced due to the influence of magnetism from other than the reinforcing bar to be inspected, or due to an erroneous setting of a threshold before the inspection. was there.
Therefore, the present invention can detect the presence or absence of a broken portion of a rebar very accurately without being affected by a ferromagnetic material other than the rebar to be inspected, an environmental magnetic field, and the like, and without requiring a threshold setting before the inspection. The object of the present invention is to provide a non-destructive inspection method and a non-destructive inspection apparatus capable of performing the above.

  According to the invention described in claim 1 of the present invention, the reinforcing bar provided in the concrete body is magnetized by a magnet from the outside of the concrete body, and then the magnetic flux density outside the concrete body is measured by a magnetic sensor. It is a non-destructive inspection method for detecting the presence or absence of a broken part of the reinforcing bar by measuring, and arranging the magnet close to the surface of the concrete body so that both magnetic poles are along the longitudinal direction of the reinforcing bar, The magnetic sensor is disposed at a plurality of positions where the separation step from the surface of the concrete body is different from the magnetization step of magnetizing the reinforcing bar by appropriately moving, and the separation distance from the surface of the concrete body. And a magnetic flux density measuring step of measuring the magnetic flux density along the longitudinal direction of the reinforcing bars at a plurality of the separation distances, By appropriately selecting the magnetic flux density at the two separation distances from the magnetic flux density at the plurality of separation distances measured in the density measurement step, and determining the difference between the two magnetic flux densities to determine the positive or negative change, or such It is a nondestructive inspection method characterized by including a break detecting step of detecting the presence or absence of a broken portion of the reinforcing bar by determining the intersection and relative position of change curves of both magnetic flux densities.

  Here, the reinforcing bar is not limited to a round steel having a round cross-sectional shape frequently used for a general reinforced concrete structure or a deformed steel bar having protrusions on its surface, but a rectangular cross-sectional shape, other polygonal steel, H It may be a shape steel. Moreover, the inside of the pipe used for water flow and ventilation may be a hollow steel pipe, and further, PC steel material such as PC steel rod, PC steel wire or PC steel twisted wire used for prestressed concrete method, or these inside It may be a sheath tube used through a PC steel material in the sheath tube.

When magnetizing the reinforcing bars in the magnetizing step, the magnet may be temporarily brought close to a predetermined position on the surface of the concrete body in order to place the magnet close to the surface of the concrete body. It is not necessary to abut on the surface, and it is not necessary to be stationary. Thereafter, the arranged magnet is moved as appropriate, and the reinforcing bar is magnetized, for example, by moving along the longitudinal direction of the reinforcing bar.
In addition, when using a large magnet having a length equal to or greater than the inspection target range in the longitudinal direction of the reinforcing bar, simply place the large magnet close to the surface of the concrete body. Since the entire inspection object range can be magnetized, it is not necessary to move the magnet.
The magnet may be either a permanent magnet or an electromagnet, and the shape may be any shape such as a rectangular parallelepiped, a U-shape or a U-shape.

  In the magnetic flux density measurement step, in order to dispose the magnetic sensor at a plurality of positions having different separation distances from the surface of the concrete body, for example, the plurality of magnetic sensors are arranged in a direction away from the surface of the concrete body at predetermined intervals. Just line up. As another arrangement method, one magnetic sensor may be sequentially arranged at predetermined intervals in a direction away from the surface of the concrete body. It should be noted that the plurality or one of the magnetic sensors arranged at the predetermined position as described above may be temporarily arranged at the predetermined position, and does not need to be stationary at the position.

Next, the magnetic flux density is measured by moving a plurality of or one magnetic sensor arranged at the predetermined position while maintaining a distance from the surface of the concrete body substantially constant. At this time, in order to move the magnetic sensor, for example, a plurality of or one magnetic sensor arranged at predetermined intervals in a direction away from the surface of the concrete body, the separation distance from the surface of the concrete body is substantially constant. In this state, the magnetic flux density may be measured while moving the space above the concrete body surface along the longitudinal direction of the reinforcing bar.
As another method, the magnetic sensor is moved in the longitudinal direction of the reinforcing bar little by little while reciprocating in the direction perpendicular to the longitudinal direction of the reinforcing bar in the space above the surface of the concrete body. By measuring the density and analyzing the measurement result, the magnetic flux density along the longitudinal direction of the reinforcing bar can be obtained.

In the rupture detection step, the magnetic flux density at the two separation distances is appropriately selected from the magnetic flux density along the longitudinal direction of the reinforcing bars at the plurality of separation distances, and a difference between the two magnetic flux densities is obtained to determine a positive / negative change. Thus, the presence or absence of a broken portion of the reinforcing bar is detected. For example, in the longitudinal direction of a reinforcing bar, the presence or absence of a broken part of the reinforcing bar is detected by finding a part where the difference between the two magnetic flux densities is zero and examining the positive / negative state of the difference between the two magnetic flux densities in the vicinity of the part. To do.
Further, the presence or absence of a broken portion of the reinforcing bar may be detected by determining the intersection point and the relative position of the change curves of both magnetic flux densities. For example, the change in the magnetic flux density along the longitudinal direction of the reinforcing bar is expressed as a change curve in a line graph, and an intersection where these change curves intersect is found, and the relative change of both change curves in the vicinity of the intersection is found. By checking the position, the presence or absence of a broken portion of the reinforcing bar is detected.
The detection of the presence or absence of a broken portion of the reinforcing bar in such a break detection step can be performed by information processing by a general electronic computer or the like, but the change curve of both magnetic flux densities is displayed on a monitor screen or the like, and the display content is displayed. Based on this, the inspector may determine whether or not there is a broken portion. Further, information processing by an electronic computer or the like and determination by an inspector may be performed together.

  Next, in the invention described in claim 2 of the present invention, the reinforcing bar provided in the concrete body is magnetized by a magnet from the outside of the concrete body, and then the magnetic flux density on the outside of the concrete body is changed. A nondestructive inspection method for detecting the presence or absence of a broken portion of the reinforcing bar by measuring with a magnetic sensor, wherein the magnet is brought close to the surface of the concrete body so that both magnetic poles are along the longitudinal direction of the reinforcing bar. The magnetic sensor is disposed at two positions where the separation step from the surface of the concrete body is different from the surface of the concrete body, and the magnetization step of magnetizing the rebar by moving the magnet appropriately and the distance from the surface of the concrete body is different from the surface of the concrete body A magnetic flux density measuring step of measuring the magnetic flux density along the longitudinal direction of the reinforcing bar at the two separation distances while moving the separation distance of For the magnetic flux density at the two separation distances measured in the magnetic flux density measurement step, the difference between the two magnetic flux densities is obtained to determine the positive or negative change, or the intersection and relative position of the change curves of the two magnetic flux densities It is a nondestructive inspection method characterized by including the fracture | rupture detection process which detects the presence or absence of the fracture | rupture part of the said reinforcing bar by discriminating.

  The nondestructive inspection method includes a plurality of positions having different separation distances from the surface of the concrete body in the nondestructive inspection method according to claim 1 in only two positions with respect to the arrangement position of the magnetic sensor in the magnetic flux density measurement step. It is limited to.

  Similarly, the invention described in claim 3 of the claim is the magnetic flux density measurement step, wherein a plurality of magnetic sensors are simultaneously arranged and moved to a plurality of positions having different separation distances from the surface of the concrete body, 3. The nondestructive inspection method according to claim 1, wherein magnetic flux densities along a longitudinal direction of the reinforcing bars at a plurality of the separation distances are simultaneously measured.

  Similarly, in the invention according to claim 4 of the claim, in the magnetic flux density measurement step, one magnetic sensor is sequentially arranged and moved to a plurality of positions having different separation distances from the surface of the concrete body. The nondestructive inspection method according to claim 1, wherein the magnetic flux density along the longitudinal direction of the reinforcing bars at a plurality of the separation distances is sequentially measured.

Next, in the invention described in claim 5 of the claims, the rebar provided in the concrete body is magnetized by a magnet from the outside of the concrete body, and then the magnetic field outside the concrete body is detected to detect the magnetic flux density. Is a non-destructive inspection device that detects the presence or absence of a broken portion of the reinforcing bar by arranging the two magnetic poles so as to be close to the surface of the concrete body along the longitudinal direction of the reinforcing bar, and appropriately moved A magnet for magnetizing the reinforcing bar;
A plurality of magnetic sensors arranged in a separation direction behind a proximity surface opposed to the surface of the concrete body, and moving the plurality of magnetic sensors simultaneously, Magnetic flux density calculation for calculating magnetic flux density along the longitudinal direction of the reinforcing bars at the plurality of separation distances from magnetic detection means for simultaneously detecting magnetism at different separation distances and the detection signals sent from the plurality of magnetic sensors And a magnetic flux density at two separation distances are appropriately selected from the magnetic flux density at the plurality of separation distances calculated by the magnetic flux density calculating means, and a difference between the two magnetic flux densities is obtained to determine a positive / negative change. Alternatively, the presence or absence of a broken portion of the reinforcing bar is detected by determining the intersection and the relative position of the change curves of both magnetic flux densities. Is a non-destructive inspection device, characterized in that it comprises a rupture detection means.

  Similarly, in the invention described in claim 6, the reinforcing bar provided in the concrete body is magnetized by a magnet from the outside of the concrete body, and then the magnetic field outside the concrete body is detected to calculate the magnetic flux density. A non-destructive inspection device for detecting the presence or absence of a broken portion of the reinforcing bar, wherein both magnetic poles are arranged close to the surface of the concrete body along the longitudinal direction of the reinforcing bar, and are appropriately moved to move the reinforcing bar And two magnetic sensors arranged in a separation direction behind a proximity surface facing and approaching the surface of the concrete body, and moving the two magnetic sensors simultaneously to From the magnetic detection means for simultaneously detecting magnetism at two different separation distances from the surface of the body and the detection signals sent from the two magnetic sensors, The magnetic flux density calculating means for calculating the magnetic flux density along the longitudinal direction of the reinforcing bar at two separation distances, and the magnetic flux density at the two separation distances calculated by the magnetic flux density calculating means, the difference between the two magnetic flux densities is obtained. And a break detecting means for detecting the presence / absence of a broken portion of the reinforcing bar by determining a positive / negative change or by determining an intersection and a relative position of the change curves of both magnetic flux densities. It is a nondestructive inspection device.

  In such a nondestructive inspection apparatus, a plurality of magnetic sensors in the magnetic detection means of the nondestructive inspection apparatus described in claim 5 are limited to only two magnetic sensors.

  Furthermore, in the invention described in claim 7 of the claims, a plurality of magnetic sensor rows each including a plurality of magnetic sensors arranged in the separation direction behind the proximity surface are provided as the magnetic detection means. The nondestructive inspection device according to claim 5 or 6, wherein the nondestructive inspection device is provided.

  A nondestructive inspection method according to claim 1 of the present invention, wherein magnetic flux densities along a longitudinal direction of a reinforcing bar at a plurality of different separation distances from the surface of a concrete body are measured, and magnetic flux densities at the plurality of separation distances are measured. From the above, according to the method of detecting the presence or absence of the broken portion of the reinforcing bar by appropriately selecting the magnetic flux density at the two separation distances, and determining the difference between the two magnetic flux densities and determining the change between positive and negative, Since the presence / absence of the fracture portion can be detected by the calculation process, the presence / absence of the fracture portion can be automatically and immediately detected using a general information processing device. In addition, since this method focuses on the positive / negative change in the difference between the two magnetic flux densities, it is not necessary to set a threshold value for comparison with the differential value of the magnetic flux density before the inspection, and the detection accuracy is reduced due to an erroneous setting of the threshold value. There is no invitation.

  Furthermore, according to the method for detecting the presence or absence of a broken portion of the reinforcing bar by determining the intersection and relative position of the change curves of the two magnetic flux densities, for example, the change in the longitudinal direction of the reinforcing bars of the two magnetic flux densities, respectively, It is possible to detect the presence or absence of a broken portion of the reinforcing bar by expressing it as a change curve of a line graph, finding an intersection where the two change curves intersect, and examining the relative position of both change curves in the vicinity of the intersection. In this case, by displaying both change curves on a monitor screen or the like, the inspector can easily and accurately determine the presence or absence of the fracture portion. In addition, when there is magnetism that hinders inspection, such as magnetism from other than the rebar to be inspected and environmental magnetic field, the influence of them appears in one or both of the change curves as a characteristic shape. Therefore, the inspector can easily notice the presence of the magnetic field that becomes an obstacle by comparing and observing both the change curves, and can prevent the detection accuracy of the broken portion of the rebar from being deteriorated due to an erroneous determination by the inspector. .

  Furthermore, in the nondestructive inspection method according to claim 1, the magnetic flux density along the longitudinal direction of the reinforcing bar at a plurality of different separation distances is measured, and two magnetic flux densities are appropriately selected from the magnetic flux densities at the plurality of separation distances. The presence or absence of a broken portion of the reinforcing bar is detected based on the both magnetic flux densities. Thus, by selecting two of the magnetic flux densities at a plurality of separation distances, two magnetic flux densities measured more accurately can be obtained. It can be selected, and the detection accuracy of the presence or absence of breakage of the reinforcing bar can be increased.

  For example, when the reinforcing bar in the concrete body is buried at a position very close to the surface of the concrete body, when the reinforcing bar is magnetized in the magnetization step, the degree of magnetization is too strong, and when measuring the magnetic flux density, The upper limit of the detection capability of the magnetic sensor may be exceeded and accurate measurement may not be possible. In such a case, two magnetic fluxes that can be measured accurately within the detection capability of the magnetic sensor by selecting two magnetic flux densities as far as possible from the concrete body surface among the magnetic flux densities at a plurality of different separation distances. Based on the density, it may be possible to detect the presence or absence of a broken portion of the reinforcing bar. This is because the magnetic flux density of magnetism generated from the reinforcing bar is larger as it is closer to the reinforcing bar, and decreases as the distance from the reinforcing bar is increased.

  In addition, when the reinforcing bar in the concrete body is buried deep in the concrete body, if the reinforcing bar is magnetized in the magnetizing step, the degree of magnetization becomes weak, and the increase / decrease width of the magnetic flux density obtained by measurement May become too small. In such a case, by selecting two magnetic flux densities that are as close as possible to the concrete body surface from among the magnetic flux densities at a plurality of different separation distances, it is based on the two magnetic flux densities that have a relatively large increase / decrease width of the measured value. In some cases, the presence or absence of a broken portion of the reinforcing bar can be detected more accurately.

  Next, according to the nondestructive inspection method described in claim 2, inspection can be performed more easily by limiting the arrangement position of the magnetic sensor in the magnetic flux density measurement step to the minimum two positions. , Can reduce the workload of the inspector.

  Furthermore, according to the nondestructive inspection method according to claim 3 of the present invention, in the magnetic flux density measurement step, a plurality of magnetic sensors are simultaneously arranged and moved at a plurality of positions having different separation distances from the surface of the concrete body. Since the magnetic flux density along the longitudinal direction of the reinforcing bars at the plurality of separation distances is measured simultaneously, the measurement of the magnetic flux density at the plurality of separation distances can be performed together in one measurement operation. , Can reduce the workload of the inspector.

  In addition, since the relative positional relationship of the plurality of magnetic sensors in the movement path can always be maintained constant by moving the plurality of magnetic sensors at the same time, measurement errors occur between the plurality of magnetic sensors. Can be prevented.

  Furthermore, by simultaneously measuring the magnetic flux density in the longitudinal direction of the reinforcing bar with a plurality of magnetic sensors, the difference between the two magnetic flux densities can be immediately obtained from the measurement result, or a change curve of the magnetic flux density can be created. it can. In other words, since it is possible to detect the presence or absence of a broken portion of the reinforcing bar almost simultaneously with the work of measuring the magnetic flux density by moving the magnetic sensor, for example, the concrete body surface in the vicinity where the broken portion of the reinforcing bar exists This is convenient because the marking operation can be performed simultaneously with the magnetic flux density measurement operation and the marking operation can be automated.

  Further, according to the nondestructive inspection method of the present invention, the magnetic sensor is sequentially arranged at a plurality of positions having different separation distances from the surface of the concrete body in the magnetic flux density measurement step. Since the magnetic flux density along the longitudinal direction of the reinforcing bar at a plurality of the separation distances is sequentially measured, the number of magnetic sensors used for the inspection can be reduced to one, which contributes to cost reduction. Can do.

  Next, according to the nondestructive inspection apparatus described in claim 5 of the present invention, the nondestructive inspection method described in claim 1 and claim 3 can be performed efficiently and reliably.

  Moreover, according to the nondestructive inspection apparatus described in claim 6 of the present invention, the nondestructive inspection method described in claim 2 and claim 3 can be performed efficiently and reliably.

  Furthermore, according to the non-destructive inspection apparatus according to claim 7 of the present invention, the magnetic detection means is arranged in the separation direction behind the proximate surface of the non-destructive inspection apparatus that is opposed to the surface of the concrete body. In addition, since a plurality of magnetic sensor arrays including a plurality of magnetic sensors are provided, there are magnetism generated from the reinforcing bar to be inspected and magnetism that becomes an obstacle to the inspection emitted from a ferromagnetic body other than the reinforcing bar to be inspected. Since the determination can be made more accurately and easily, the detection accuracy of the presence or absence of a broken portion of the inspection target reinforcing bar can be increased.

It is explanatory drawing which shows the magnetic state at the time of arrange | positioning close to the surface of a concrete body so that a magnet may be along the longitudinal direction of the reinforcing bar without a fracture | rupture part by which both magnetic poles were embed | buried in a concrete body. It is explanatory drawing which shows the magnetic state in case the reinforcing bar with the fracture | rupture part embed | buried in a concrete body is magnetized. It is a graph which shows the measurement result of the perpendicular component of the magnetic flux density in the three different separation distance from this reinforcing bar along the longitudinal direction of the reinforcing bar without a fracture | rupture part. It is a graph which shows the measurement result of the perpendicular component of the magnetic flux density in the three different separation distance from this reinforcing bar along the longitudinal direction of the reinforcing bar with a fracture part. It is explanatory drawing which shows the state which has arrange | positioned the magnet close | similar to the surface of a concrete body so that the magnetic pole may follow the longitudinal direction of the reinforcing bar with the fracture | rupture part with which the concrete body was embed | buried. It is a schematic block diagram at the time of arrange | positioning a nondestructive inspection apparatus close to the surface of a concrete body. It is a schematic block diagram at the time of seeing the nondestructive inspection apparatus of FIG. 6 from the left side. It is a schematic block diagram which shows another embodiment of a nondestructive inspection apparatus.

  Hereinafter, embodiments of a nondestructive inspection method and a nondestructive inspection apparatus according to the present invention will be described.

(1) Nondestructive inspection method The nondestructive inspection method of this invention is an inspection method for detecting the presence or absence of the fracture | rupture part of a reinforcing bar including a magnetization process, a magnetic flux density measurement process, and a fracture | rupture detection process. Hereinafter, each step will be described.

(1-1) Magnetization process In FIG. 1, 1 is a concrete body, and the concrete body 1 has a reinforcing bar 2 to be inspected embedded therein.
First, as shown in FIG. 1, the magnet 4 is brought close to the surface 3 of the concrete body 1, the magnetic poles thereof are arranged along the longitudinal direction of the reinforcing bar 2, and the N pole is placed on the left side of the figure and the S pole is placed on the right side of the figure. Then, the rebar 2 is magnetized under the influence of magnetism indicated by the magnetic lines 5 generated from the magnet 4, and a magnetic flux 2A in the direction indicated by the arrow is generated.

Since the magnet 4 in the present embodiment is a substantially rectangular parallelepiped permanent magnet made of a rare earth metal such as an Nd-based material, when both the magnetic poles are arranged along the longitudinal direction of the rebar 2, the magnetic flux M <b> 1 inside the magnet 5 is rebar. 2 is substantially parallel to the longitudinal direction.
The direction of both magnetic poles of the magnet 4 may be opposite to the present embodiment, with the S pole being the left and the N pole being the right. The magnet 4 may be exposed as it is, but is housed in a case having a function for facilitating movement while being close to the surface of the concrete body, or a unit such as a combination of a plurality of magnets. There may be.

  Thereafter, the magnet 4 is moved in the longitudinal direction of the reinforcing bar 2 (X direction in FIG. 1), and the entire inspection target range of the reinforcing bar 2 is magnetized. At that time, in order to sufficiently magnetize the reinforcing bar 2, the magnet 4 may be reciprocated a plurality of times in the X direction and the −X direction along the longitudinal direction of the reinforcing bar 2. Further, the moving trajectory of the magnet 4 does not necessarily have to be directly above the reinforcing bar 2 (that is, when the position of the magnet 4 in the Y direction and the position of the reinforcing bar 2 in the Y direction are the same).

(1-2) Magnetic flux density measurement step After the magnet 4 is removed, magnetic sensors are arranged at a plurality of positions having different separation distances from the concrete body surface 3, and the magnetic sensors are separated from the concrete body surface 3 by approximately the separation distance. The magnetic flux density is measured along the longitudinal direction of the reinforcing bars at a plurality of the separation distances while being kept constant.
For example, as shown in FIG. 2, a total of three magnetic sensors, one each, are arranged at the left end position of the space portion indicated by broken lines A, B, and C having different separation distances from the concrete body surface 3. The magnetic flux density along the longitudinal direction of the reinforcing bar can be measured by simultaneously moving the magnetic sensors along the broken lines A, B, and C in the right direction from the left end position in the figure. In addition, with one magnetic sensor to be used, the magnetic flux density along the longitudinal direction of the reinforcing bar is measured by sequentially arranging the magnetic sensors at the left end positions indicated by broken lines A, B, and C and moving along the broken lines. You may do it.

The measurement results of the magnetic flux density along the longitudinal direction of the reinforcing bar measured by this method are shown in FIGS.
FIG. 3 is a graph showing changes in the vertical component (component in the Z direction) of the magnetic flux density at three different separation distances from the reinforcing bar along the longitudinal direction (X direction) of the reinforcing bar without a fracture portion.
More specifically, the reinforcing bar to be measured is a deformed steel bar having a diameter of 16 mm embedded in the concrete body substantially parallel to the surface of the concrete body, has no fracture portion, and has a core cover thickness of 100 mm. The change curves E1, E2, and E3 of the graph are the longitudinal direction of the reinforcing bar at each position where the separation distance from the concrete surface is 25 mm, 50 mm, and 75 mm (separation distance from the center of the reinforcing bar is 125 mm, 150 mm, and 175 mm, respectively) The change of increase / decrease in the vertical component of the magnetic flux density along is shown. Further, the horizontal axis of the graph of FIG. 3 represents the position of the reinforcing bar in the X direction (unit: mm), and the vertical axis represents the vertical component (unit: μT) of the magnetic flux density at the position.

  The change curves E1, E2, and E3 are all gently rising to the right, but the slope of the change curve E1 having the smallest separation distance from the concrete body surface (and the reinforcing bar) is the largest, and the separation distance is the largest. The slope of the change curve E3 is the smallest. This is because the magnetic flux density of magnetism generated from the reinforcing bar is larger as it is closer to the reinforcing bar, and decreases as the distance from the reinforcing bar is increased.

  In addition, the fact that each of the change curves has a shape that rises to the right is related to the method of magnetization of the reinforcing bars. That is, in the present embodiment, as shown in FIG. 1, the magnet 4 is arranged along the longitudinal direction of the reinforcing bar 2 with the south pole in the drawing right and the north pole in the drawing left. By magnetizing the reinforcing bar 2 by moving it from the left to the right in the figure, the portion on the left side of the reinforcing bar 2 is strongly influenced by the N pole of the magnet 4 and the vertical component of the magnetic flux density is downward (- On the other hand, the portion closer to the right side of the reinforcing bar 2 is strongly influenced by the south pole of the magnet 4 and the vertical component of the magnetic flux density appears upward (Z direction).

Therefore, unlike the present embodiment, when the rebar is magnetized with the relative positions of the two magnetic poles of the magnet 4 reversed from the present embodiment, the change curve indicating the vertical component of the magnetic flux density has a downward-sloping shape. .
In this embodiment, the magnetic flux density generated from the reinforcing bar is measured with the vertical component (Z-direction component) as the measurement target, but the measurement target is the horizontal component (X-direction or Y-direction component). It is also possible to detect the presence or absence of a fractured part based on the value.

Next, FIG. 4 is a graph showing an increase / decrease change in the vertical component (component in the Z direction) of the magnetic flux density at three different separation distances from the reinforcing bar along the longitudinal direction (X direction) of the reinforcing bar having the fracture portion. It is.
More specifically, the reinforcing bar to be measured is a deformed steel bar with a diameter of 16 mm embedded in the concrete body substantially parallel to the surface of the concrete body, and there is a fracture at the location corresponding to the position of about 0 mm on the horizontal axis of the graph. The core cover thickness of concrete is 100 mm. The change curves F1, F2, and F3 of the graph are the longitudinal direction of the reinforcing bar at each position where the separation distance from the concrete body surface is 25 mm, 50 mm, and 75 mm (separation distance from the center of the reinforcing bar is 125 mm, 150 mm, and 175 mm, respectively) The change of increase / decrease in the vertical component of the magnetic flux density along is shown. The horizontal axis of the graph in FIG. 4 represents the position (unit: mm) of the reinforcing bar in the X direction, and the vertical axis represents the vertical component (unit: μT) of the magnetic flux density at the position.

  The change curves F1, F2, and F3 all have an upward convex portion on the left side (negative side) from the 0 mm position (the position of the fracture portion H) on the horizontal axis of the graph, and downward on the right side (positive side). Is a so-called S-shaped curve having a convex shape portion, and the change curve F1 having the smallest separation distance from the concrete body surface (and the reinforcing bar) has the largest upward and downward convex shape portions, The change curve F3 having the largest separation distance has the smallest upward and downward convex portions. This is because the magnetic flux density of magnetism generated from the reinforcing bar is larger as it is closer to the reinforcing bar, and decreases as the distance from the reinforcing bar is increased.

The reason why these change curves F1, F2, and F3 are the S-shaped curves will be described with reference to FIGS.
As shown in FIG. 5, the magnet 4 with the N pole on the left and the S pole on the right is placed on the concrete body surface 3 so as to be along the longitudinal direction of the reinforcing bar 2 having the fracture portion H embedded in the concrete body 1. When the reinforcing bars 2 are arranged close to each other and then moved in the X direction to magnetize the reinforcing bar 2, the parts other than the breaking part H of the reinforcing bar 2 are magnetized, but the breaking part H is not magnetized. Here, as shown in FIG. 2, a magnetic flux 2AN in the X direction is generated in the reinforcing bar 2N located on the negative side in the X direction with the fracture portion H as the origin position, and the reinforcing bar 2P located on the positive side in the X direction Similarly, a magnetic flux 2AP in the X direction is generated.

  FIG. 2 shows the lines of magnetic force generated from the reinforcing bar 2N and the reinforcing bar 2P after the magnet 4 is removed from the concrete body surface 3. FIG. Magnetic field lines 51 are generated from the reinforcing bar 2N, and magnetic field lines 52 are generated from the reinforcing bar 2P. In this case, a magnetic flux 5N1 in the −Z direction is generated above the concrete body surface 3 above the left end portion of the reinforcing bar 2N, while a magnetic flux 5N2 opposite to the magnetic flux 5N1 is generated above the right end portion of the reinforcing bar 2N. Further, a magnetic flux 5P1 in the -Z direction is generated above the left end of the reinforcing bar 2P, while a magnetic flux 5P2 opposite to the magnetic flux 5P1 is generated above the right end of the reinforcing bar 2P.

Therefore, when the vertical component of the magnetic flux density above the concrete body surface 3 along the entire reinforcing bar 2 including the reinforcing bars 2N and 2P is measured, as shown in FIG. An S-shaped curve having an upward convex portion on the left side (negative side) and a downward convex portion on the right side (positive side) is obtained.
Unlike the present embodiment, when the rebar is magnetized with the relative positions of both magnetic poles of the magnet 4 reversed from that of the present embodiment, the horizontal axis of the graph is opposite to the change curves of FIG. A change curve having a downward convex portion on the left side of the 0 mm position and an upward convex portion on the right side.

(1-3) Breakage detection step (1-3-1) A step of detecting the presence or absence of a broken portion of the reinforcing bar will be described. That is, the magnetic flux density at two separation distances is appropriately selected from the magnetic flux density along the longitudinal direction of the reinforcing bar at a plurality of different separation distances from the concrete body surface measured in the magnetic flux density measurement step, and both the magnetic fluxes are applied. This is a step of detecting the presence or absence of a broken portion of a reinforcing bar by determining a difference in density by determining a difference in density.

For example, in FIG. 4, as described above, the magnetic flux density at three different separation distances from the reinforcing bars in the longitudinal direction along the longitudinal direction of the reinforcing bars having a broken portion at a portion corresponding to the position of about 0 mm on the horizontal axis of the graph. Three change curves (F1, F2, F3) showing increase / decrease changes in the components are shown. From these, change curve F1 and change curve F3 are selected as an example, and both magnetic fluxes represented by these change curves are selected. The density difference is determined.
That is, from the measured value of magnetic flux density (hereinafter referred to as “F1 value”) when the separation distance from the concrete body surface shown by the change curve F1 is 25 mm (the separation distance from the center of the reinforcing bar is 125 mm), the change curve F3 is shown. The difference is obtained by subtracting the measured value of magnetic flux density (hereinafter referred to as “F3 value”) when the distance from the concrete body surface is 75 mm (the distance from the center of the reinforcing bar is 175 mm).
Then, the difference (F1 value−F3 value) becomes a numerical value (negative number) smaller than 0 within the range of about −900 mm on the horizontal axis of the graph in FIG. 4, and the difference becomes 0 at about −900 mm, exceeding about −900 mm. If the range is less than 0 mm, the difference will be larger than 0 (positive number), and if it is about 0 mm, the difference will be 0 again. If the range is more than about 0 mm and less than about 900 mm, the difference will be less than 0 (negative number) and about 900 mm. The difference becomes 0 again, and in the range exceeding about 900 mm, the difference becomes a numerical value (positive number) larger than 0.

As described above, the difference (F1 value−F3 value) is zero at three positions of about −900 mm, about 0 mm, and about 900 mm on the horizontal axis of FIG. 4, which corresponds to these three positions of the reinforcing bar. Regarding the portion, there is no breakage in the portions corresponding to about −900 mm and about 900 mm, and only the portion corresponding to about 0 mm has breakage.
Therefore, paying attention to the difference between the left and right sides of the three positions (F1 value−F3 value), the difference on the left side (negative direction side) is a negative number at the positions of about −900 mm and about 900 mm where the reinforcing bars are not broken. The difference on the right side (positive direction side) is a positive number. On the other hand, at a position of about 0 mm where the reinforcing bar is broken, the difference on the left side is a positive number, and the difference on the right side is a negative number, which is characteristic in this respect.
From the above, it can be seen that the presence or absence of a broken portion of a reinforcing bar can be detected by determining the positive and negative changes in the magnetic flux density at two different separation distances from the concrete body surface by determining the difference between the two magnetic flux densities.

Next, the case where the reinforcing bar has no fracture portion will be described. FIG. 3 shows three change curves (E1, E2, E3) showing changes in the vertical component of the magnetic flux density at three different separation distances from the reinforcing bar along the longitudinal direction of the reinforcing bar having no fracture portion. However, from these, a change curve E1 and a change curve E3 are selected as an example, and a difference between both magnetic flux densities represented by the both change curves is obtained.
That is, from the measured value of magnetic flux density when the separation distance from the concrete body surface indicated by the change curve E1 is 25 mm (hereinafter referred to as “E1 value”), the separation distance from the concrete body surface indicated by the change curve E3 is 75 mm. The difference is obtained by subtracting the measured value of the magnetic flux density (hereinafter referred to as “E3 value”). Then, the difference (E1 value−E3 value) is a value (negative number) smaller than 0 within the range of about 0 mm on the horizontal axis of the graph in FIG. 3, the difference is 0 at about 0 mm, and the difference is 0 at a range exceeding about 0 mm. Larger value (positive number).

  This is because the difference (F1) on the left side (negative direction side) of the position where the rebar does not break despite the difference between the two magnetic flux densities represented by the change curves F1 and F3 in FIG. 4 being zero. (Value−F3 value) is a negative number, which is consistent with the fact that the difference on the right side (positive side) is a positive number. Therefore, it can be seen that the presence or absence of a broken portion of the reinforcing bar can be detected by determining the positive and negative changes of the magnetic flux density at two different distances from the concrete body surface by obtaining the difference between the two magnetic flux densities.

As described above, according to the method for detecting the presence or absence of the broken portion of the reinforcing bar by determining the positive / negative change by obtaining the difference between the two magnetic flux densities at the two separation distances, the fracture portion can be detected by a relatively simple calculation process. Since the presence / absence can be detected, it is possible to automatically and immediately detect the presence / absence of a fracture using a general information processing device.
In addition, since this method focuses on the positive / negative change in the difference between the two magnetic flux densities, it is not necessary to set a threshold value for comparison with the differential value of the magnetic flux density before the inspection, and the detection accuracy is reduced due to an erroneous setting of the threshold value. Can be prevented.

(1-3-2) Next, another process for detecting the presence or absence of a broken portion of the reinforcing bar will be described. That is, the magnetic flux density at two separation distances is appropriately selected from the magnetic flux density along the longitudinal direction of the reinforcing bar at a plurality of different separation distances from the concrete body surface measured in the magnetic flux density measurement step, and both the magnetic fluxes are applied. This is a step of detecting the presence or absence of a broken portion of the reinforcing bar by determining the intersection and the relative position of the density change curve.

  For example, as shown in FIG. 4, as shown in FIG. 4, as an example, the separation from the surface of the concrete body from three change curves indicating the vertical components of the magnetic flux density at three different separation distances from the reinforcing bar where the fracture occurs. When the distance is 25 mm (the separation distance from the center of the reinforcing bar is 125 mm), the change curve F1 indicating the vertical component of the magnetic flux density along the longitudinal direction of the reinforcing bar, and the separation distance is 75 mm (the separation distance from the center of the reinforcing bar is 175 mm), a change curve F3 indicating a vertical component of the magnetic flux density along the longitudinal direction of the reinforcing bar is selected, and an intersection point and a relative position where the two change curves intersect are determined.

First, intersections where the change curve F1 and the change curve F3 intersect exist at three positions of about −900 mm, about 0 mm, and about 900 mm on the horizontal axis of the graph of FIG. 4.
The relative positions of the change curves F1 and F3 on both the left and right sides of these intersections are such that the change curve F1 is at a low position (a position where the magnetic flux density is small) and the change curve F3 is high within a range of about −900 mm on the horizontal axis of the graph. At the position (the position where the magnetic flux density is large), both change curves intersect at about -900 mm, and the change curve F1 is at the high position and the change curve F3 is at the low position in the range of more than about -900 mm and less than about 0 mm. The change curve crosses again at about 0 mm, the change curve F1 is in the low position and the change curve F3 is in the high position in the range of more than about 0 mm and less than about 900 mm, and both change curves cross again at about 900 mm. In a range exceeding about 900 mm, the change curve F1 is at the high position and the change curve F3 is at the low position.

As described above, the change curves F1 and F3 intersect at three positions of about −900 mm, about 0 mm, and about 900 mm on the horizontal axis of FIG. 4, but the portions corresponding to these three positions of the reinforcing bar are as follows. There are no breaks in the portions corresponding to about -900 mm and about 900 mm, and only the portions corresponding to about 0 mm have breaks.
Therefore, paying attention to the relative positions of the change curves F1 and F3 on the left and right sides of the three positions, both the change curve F1 on the left side (the negative direction side) at positions of about −900 mm and about 900 mm where the reinforcing bars are not broken. Is at the low position, the change curve F3 is at the high position, and on the right side (positive direction side), the change curve F1 is at the high position and the change curve F3 is at the low position. On the other hand, at a position of about 0 mm where the rebar is broken, the change curve F1 is at the high position and the change curve F3 is at the low position on the left side, and the change curve F1 is at the low position on the right side and the change curve F3 is at the high position. And is characteristic in this respect.

  From the above, for each magnetic flux density at two different separation distances from the concrete body surface, the position of the intersection of both change curves indicating the increase and decrease in the longitudinal direction of both magnetic flux densities and both changes in the vicinity of the intersection It can be seen that the presence or absence of a broken portion of the reinforcing bar can be detected by determining the relative position of the curve.

  Next, the case where the reinforcing bar has no fracture portion will be described. FIG. 3 shows three change curves (E1, E2, E3) showing changes in the vertical component of the magnetic flux density at three different separation distances from the reinforcing bar along the longitudinal direction of the reinforcing bar having no fracture portion. However, from these, a change curve E1 and a change curve E3 are selected as an example, and an intersection point and a relative position where both the change curves intersect are determined.

First, the intersection where the change curve F1 and the change curve F3 intersect exists at a position of about 0 mm on the horizontal axis of the graph of FIG.
The relative positions of the change curves F1 and F3 on the left and right sides of the intersection point are such that the change curve E1 is at a low position (position where the magnetic flux density is small) and the change curve E3 is at a high position (less than about 0 mm on the horizontal axis of the graph). The change curve intersects at about 0 mm, and the change curve E1 is at a high position and the change curve E3 is at a low position in a range exceeding about 0 mm.

This is because the relative positions of the change curves F1 and F3 in the vicinity of this position are on the left side (in the negative direction) at the position where the rebar does not break despite the change curves F1 and F3 intersecting in FIG. The change curve F1 is in the low position and the change curve F3 is in the high position, and the change curve F1 is in the high position and the change curve F3 is in the low position on the right side (positive side). . Therefore,
Therefore, for the magnetic flux density at two different separation distances from the concrete body surface, the position of the intersection where both the change curves indicating the increase / decrease change in the longitudinal direction of both magnetic flux densities intersect, and both change curves in the vicinity of the intersection It can be seen that the presence or absence of a broken portion of the reinforcing bar can be detected by discriminating the relative position.

  As described above, according to the method for detecting the presence or absence of a broken portion of the reinforcing bar by determining the intersection and relative position of the change curves of both magnetic flux densities at two separation distances, both change curves can be displayed on a monitor screen or the like. Thus, the inspector can easily and accurately determine the presence or absence of the fracture portion. In addition, when there is magnetism that hinders inspection, such as magnetism from other than the rebar to be inspected and environmental magnetic field, the influence of them appears in one or both of the change curves as a characteristic shape. Therefore, the inspector can easily notice the presence of the magnetic field that becomes an obstacle by comparing and observing both the change curves, and can prevent the detection accuracy of the broken portion of the rebar from being deteriorated due to an erroneous determination by the inspector. .

(1-4) Effect of Invention of Nondestructive Inspection Method In the nondestructive inspection method of this embodiment, in the rupture detection step, a difference between both magnetic flux densities at two separation distances (for example, the F1 value−F3 value) is calculated. According to the method for detecting the presence or absence of the fracture portion H of the reinforcing bar 2 by determining the positive and negative changes, the presence or absence of the fracture portion H can be automatically and immediately detected by a relatively simple calculation process.

Similarly, in the broken portion detection step, the presence or absence of the broken portion H of the reinforcing bar 2 is determined by determining the intersection and the relative position of the change curves of both magnetic flux densities at two separation distances (for example, the change curves F1 and F3 in FIG. 4). According to the detection method, the inspector can easily and accurately determine the presence or absence of the fracture portion H by observing the relative position of both change curves at the intersection of both change curves and the vicinity thereof.
In addition, when there is magnetism that hinders inspection from other than the reinforcing bar to be inspected, the influence appears as a characteristic shape in one or both of the change curves. By observing the change curve, it is possible to easily notice the presence of the magnetism that becomes an obstacle, and it is possible to prevent the detection accuracy of the broken portion H of the reinforcing bar 2 from being lowered.

  Moreover, in the nondestructive inspection method of this embodiment, for example, as shown in FIG. 2, in the longitudinal direction of the reinforcing bar 2 at each position indicated by broken lines A, B, and C having different separation distances from the concrete body surface 3. The magnetic flux density is measured, and two magnetic flux densities are appropriately selected from the magnetic flux densities at these three separation distances, and the presence or absence of the fracture portion H of the reinforcing bar 2 (2N and 2P) is detected based on both magnetic flux densities. Thus, by selecting two of the magnetic flux densities at three separation distances, two magnetic flux densities measured more accurately can be selected, and the detection accuracy of the presence or absence of breakage H of the reinforcing bar 2 can be improved. it can.

  For example, when the reinforcing bar 2 in the concrete body 1 is buried at a position very close to the concrete body surface 3, if the reinforcing bar 2 is magnetized in the magnetizing step, the degree of magnetization is too strong and the magnetic flux density is reduced. When measuring, the upper limit of the detection capability of the magnetic sensor may be exceeded and accurate measurement may not be possible. In such a case, by selecting the magnetic flux density at the two separation distances of the broken line B and the broken line C far from the concrete body surface 3 among the magnetic flux density at the three separation distances indicated by the broken lines A, B, and C, In some cases, the fracture portion H of the reinforcing bar 2 can be detected based on two magnetic flux densities that can be accurately measured within the range of the detection capability of the magnetic sensor.

  Further, when the reinforcing bar 2 in the concrete body 1 is buried deep in the concrete body 1, if the reinforcing bar is magnetized in the magnetizing step, the degree of magnetization becomes weak, and the magnetic flux obtained by measurement. The increase / decrease width of the density may become too small. In such a case, by selecting the magnetic flux density at the two separation distances of the broken line A and the broken line B near the concrete body surface 3 among the magnetic flux density at the three separation distances indicated by the broken lines A, B, and C, In some cases, the fracture portion H of the reinforcing bar 2 can be detected more accurately based on two magnetic flux densities in which the increase / decrease width of the measured value is relatively large.

  Further, according to the nondestructive inspection method of the present embodiment, as shown in FIG. 2, three magnetic sensors (not shown) are shown along the broken lines A, B, and C having different separation distances from the concrete body surface 3. The magnetic flux density at the three separation distances is measured at the same time, so that the measurement of the magnetic flux density at the three separation distances can be performed in a single measurement operation. Can reduce the workload.

  Furthermore, by moving the three magnetic sensors at the same time, the relative positional relationship of the magnetic sensors in the movement path can always be maintained constant, thus preventing measurement errors between the magnetic sensors. it can.

  Further, by simultaneously measuring the magnetic flux density in the longitudinal direction of the reinforcing bar 2 with three magnetic sensors, a difference between the two magnetic flux densities can be immediately obtained from the measurement result, or a change curve of the magnetic flux density can be created. it can. That is, since the presence or absence of the fracture portion H of the reinforcing bar 2 can be detected substantially simultaneously with the operation of moving the magnetic sensor and measuring the magnetic flux density, for example, the vicinity where the fracture portion H of the reinforcing bar 2 exists This is convenient because the marking work can be performed simultaneously with the magnetic flux density measurement work and the marking work can be automated.

(2) Non-destructive inspection apparatus (2-1) Overall configuration The non-destructive inspection apparatus 6 is an apparatus that can reliably and efficiently implement the above-described non-destructive inspection method, as shown in FIGS. Further, it is composed of a magnet 4, a main body portion 7 and a monitor portion 16. The main body portion 7 includes three magnetic sensors 10 as magnetic detection means, a magnetic flux density calculation means 12 and a breakage detection means 14.

An outline of the case where the nondestructive inspection is performed using the nondestructive inspection apparatus 6 is as follows.
First, the magnet 4 is used in the magnetizing step of the nondestructive inspection method. In the magnetizing step, the magnet 4 is placed on the surface of the concrete body so that both magnetic poles are along the longitudinal direction of the reinforcing bar. It arrange | positions close | similar to 3 and it moves suitably, and the rebar 2 is magnetized.

  Next, the three magnetic sensors 10 and the magnetic flux density calculating means 12 as magnetic detecting means are used in the magnetic flux density measuring step of the nondestructive inspection method. In such a magnetic flux density measurement process, the three magnetic sensors 10 are arranged at three positions that are different from the concrete body surface 3 respectively, and the distance from the concrete body surface 3 is maintained substantially constant as it is. Simultaneously move to detect magnetism. Further, the magnetic flux density calculation means 12 calculates the magnetic flux density along the longitudinal direction of the reinforcing bar 2 at three separation distances from the detection signals sent from the three magnetic sensors 10.

  Further, the break detecting means 14 is used in the break detecting step of the non-destructive inspection method. In the rupture detection step, the magnetic flux density at the two separation distances is appropriately selected by the rupture detection means 14 from the magnetic flux density at the three separation distances calculated by the magnetic flux density calculation means 12, and the difference between the two magnetic flux densities is calculated. The presence / absence of the broken portion H of the reinforcing bar 2 is detected by determining positive and negative changes or determining the intersection and relative position of the change curves of both magnetic flux densities.

  Hereinafter, main components of the nondestructive inspection apparatus 6 will be described.

(2-2) Magnet The magnet 4 magnetizes the rebar 2 to be inspected embedded in the concrete body 1. For example, as shown in FIG. 5, the magnet 4 has both magnetic poles in the longitudinal direction of the rebar 2. It arrange | positions close to the concrete body surface 3 so that it may follow, and the rebar 2 is magnetized by moving along the longitudinal direction of the rebar 2.
The magnet 4 of this embodiment is a substantially rectangular parallelepiped permanent magnet made of a rare earth metal such as Nd, and is housed in a rectangular parallelepiped casing (not shown) with a handle for easy handling. It has been. The magnet 4 may be an electromagnet instead of a permanent magnet as in the present embodiment, and the shape is not limited to a rectangular parallelepiped, and may be any shape such as a U shape or a U shape. Furthermore, it is not in a form housed in a housing as in this embodiment, but may be in a bare state as it is, or may be a unit obtained by combining a plurality of magnets.

(2-3) Magnetic detection means The three magnetic sensors 10 as magnetic detection means are installed in the main body 7 and are used as the bottom surface of the casing of the main body 7 as shown in FIGS. In some cases, they are lined up in the separation direction (directly upward in FIG. 6) behind the proximity surface 9 that faces the concrete body surface 3 close to the surface (upward in FIG. 6).
In addition, a total of four wheels 8 are rotatably attached to the main body portion 7 one by one on the front and rear portions on both sides of the housing, and the wheels 8 are moved while being in contact with the concrete body surface 3. The three magnetic sensors 10 in the main body 7 can be moved in a state where the separation distance from the concrete body surface 3 is maintained substantially constant.

Therefore, according to this magnetic detection means, for example, as shown in FIG. 6, the main body portion 7 is moved along the longitudinal direction of the reinforcing bars 2 (2N, 2P) while moving on the concrete body surface 3 with three pieces. By activating the magnetic sensor 10, the magnetism at three different separation distances from the concrete body surface 3 can be detected simultaneously.
As the magnetic sensor 10, a highly sensitive MI sensor, flux gate type sensor, Hall element, superconducting quantum interference element, or the like can be employed.

(2-4) Magnetic flux density calculation means Next, the magnetic flux density calculation means 12 is installed in the main body 7, and the three separation distances are detected from the magnetic detection signals sent from the three magnetic sensors 10. The vertical component of the magnetic flux density along the longitudinal direction of the reinforcing bar 2 is calculated and obtained.
In this embodiment, the vertical component of the magnetic flux density is calculated, but another direction component of the magnetic flux density, for example, a horizontal component may be calculated.
Further, the calculated magnetic flux density may be stored in the storage unit 13.

Here, in order to accurately calculate the magnetic flux density, the correspondence between the measured value of the magnetic flux density and the measurement position needs to be accurate. Therefore, it is desirable to provide the distance sensor 11 in the main body 7 and measure the moving distance of the main body 7 simultaneously with the measurement of the magnetic flux density. In the nondestructive inspection device 6 of the present embodiment, a distance sensor 11 that measures a moving distance based on the number of rotations of four wheels 8 attached to the main body 7 is employed.
For example, when the main body 7 has a high-precision positioning mechanism, the position of the main body 7 and the magnetic flux density at that position can be directly matched without the distance sensor 11.

(2-5) Breakage Detection Unit Next, the breakage detection unit 14 appropriately selects the magnetic flux density at the two separation distances from the magnetic flux density at the three separation distances calculated by the magnetic flux density calculation unit 12. The presence / absence of the fracture portion H of the reinforcing bar 2 is detected by determining the difference between positive and negative by obtaining the difference in magnetic flux density. Moreover, the presence or absence of the fracture | rupture part H of the reinforcing bar 2 can also be detected by creating a change curve of both magnetic flux densities and determining the intersection and relative position of both change curves.

Information such as the presence / absence of the broken portion H and the position thereof detected by these methods is stored in the storage means 13 and also transmitted to the reception means 18 of the monitor unit 16 located away from the main body part 7 by the transmission means 15. It is sent by electricity. The monitor unit 16 can display a change curve of a graph created based on the received inspection result and the measured magnetic flux density on the display unit 17 including a liquid crystal panel.
Further, if a camera (not shown) is attached to the main body unit 7 and the captured image data is transmitted to the monitor unit 16, the condition of the concrete body at the site can be confirmed at a place other than the inspection site. It is.

(2-6) Other Embodiments of Non-Destructive Inspection Device The non-destructive inspection device shown in FIG. 8 includes nine magnetic sensors 10 as magnetic detection means. Among the nine magnetic sensors 10, the magnetic sensor array composed of three “A, B, C” has the same arrangement as the embodiment in which the three magnetic sensors are arranged in series. , Bl, Cl ”and a magnetic sensor array composed of“ Ar, Br, Cr ”are added at positions that are substantially symmetrical in the casing width direction of the main body 7 (left-right direction in FIG. 8). It has become a form.
In addition, among the magnetic sensors 10, the three magnetic sensors “A, Al, Ar” adjacent to each other in the housing width direction of the main body 7 have substantially the same separation distance from the proximity surface 9 and are adjacent in the same manner. The three magnetic sensors “B, Bl, Br” and “C, Cl, Cr” also have substantially the same distance from the proximity surface 9.

Thus, in addition to the central magnetic sensor array (A, B, C), a new magnetic sensor array (Al, Bl, Cl, Ar, Br, or both) is provided on either the left side or the right side of the main body 7. , Cr) so that it is possible to more accurately and easily discriminate between the magnetism emitted from the reinforcing bar 2 and the magnetism that is an obstacle to the examination emitted from a ferromagnetic material other than the reinforcing bar to be inspected. Become.
For example, when a reinforcing bar (not shown; a reinforcing bar extending in the left-right direction in FIG. 8, hereinafter referred to as “orthogonal reinforcing bar”) that is substantially orthogonal to the reinforcing bar 2 to be inspected is embedded in the vicinity of the reinforcing bar 2. Because of the influence of magnetism from the orthogonal reinforcing bars, it may be difficult to detect the broken portion of the reinforcing bars 2 only with the measurement results of the magnetic sensor array (A, B, C) arranged just above the reinforcing bars 2. is there. However, by providing a magnetic sensor array on the left or right side of the main body 7, it is possible to accurately detect the presence or absence of the broken portion H of the reinforcing bar 2 even when there is an orthogonal reinforcing bar, taking into account the influence. It becomes.

For example, in FIG. 8, the magnetic sensor A and the magnetic sensor Al or Ar have a separation distance from the reinforcing bar 2, and the magnetic sensor A is small and the magnetic sensor Al or Ar is large. As for the vertical component, the measured value by the magnetic sensor A is larger than the measured value by the magnetic sensor Al or Ar.
On the other hand, since the separation distance between the orthogonal reinforcing bar and the magnetic sensor A and the separation distance between the orthogonal reinforcing bar and the magnetic sensor Al or Ar are substantially the same, the vertical component of the magnetic flux density emitted from the orthogonal reinforcing bar is the magnetic sensor. The measured value by A and the measured values by the magnetic sensors Al and Ar are approximately the same size.
Therefore, by comparing the measured values of the magnetic flux density of a plurality of magnetic sensors (for example, A, Al, Ar) belonging to different magnetic sensor arrays, it is possible to estimate the magnitude of the magnetic flux density emitted from the orthogonal reinforcing bar, In consideration of the influence of the magnetic flux density of the orthogonal reinforcing bars, the presence or absence of the fracture portion H of the reinforcing bars 2 can be accurately detected.

  As described above, the nondestructive inspection apparatus according to the present embodiment has three magnetic sensor rows each including three magnetic sensors 10, and includes nine magnetic sensors 10 in total. It is possible to discriminate between the generated magnetism and the magnetism that is an obstacle to the inspection emitted from other than the inspection target reinforcing bar. Therefore, even when a large number of ferromagnetic materials other than the inspection target reinforcing bars are embedded in the concrete body 1, it is possible to detect the presence or absence of the broken portion H of the reinforcing bars 2 with high accuracy.

  As long as the effects of the present invention are exhibited, the plurality of magnetic sensor rows do not necessarily have to be arranged substantially symmetrically in the housing width direction of the main body 7 (the left-right direction in FIG. 8). The number of magnetic sensors belonging to each magnetic sensor row may be different. Further, the plurality of magnetic sensors adjacent to each other in the housing width direction may not have substantially the same distance from the proximity surface 9.

  The nondestructive inspection method and the nondestructive inspection apparatus of the present invention can be used for nondestructive inspection for detecting the presence or absence of breakage of a reinforcing bar provided in a concrete body such as a bridge, a building, or a concrete pole.

1 .. Concrete body 2 .. Reinforcing bar 2 .. Magnetic flux generated in magnetized rebar 3 .. Concrete body surface 4 .. Magnet 5 .. Magnetic field line 6 .. Non-destructive inspection device 7. ..Proximity surface (bottom case surface)
10 .. Magnetic sensor 11 .. Distance sensor 12 .. Magnetic flux density calculation means 13 .. Storage means 14 .. Breakage detection means 15 .. Transmission means 16 .. Monitor section 17 .. Display means 18.・ Rupture

Claims (7)

A nondestructive inspection method for detecting the presence or absence of a broken portion of the reinforcing bar by magnetizing a reinforcing bar provided in the concrete body with a magnet from the outside of the concrete body and then measuring the magnetic flux density on the outside of the concrete body with a magnetic sensor Because
A magnetizing step of placing the magnet close to the surface of the concrete body so that both magnetic poles are along the longitudinal direction of the reinforcing bar, and magnetizing the reinforcing bar by appropriately moving the magnet,
The magnetic sensors are arranged at a plurality of positions having different separation distances from the surface of the concrete body, the magnetic sensors are moved in a state where the separation distances from the surface of the concrete body are maintained substantially constant, A magnetic flux density measuring step for measuring a magnetic flux density along a longitudinal direction of the reinforcing bar at a separation distance;
By appropriately selecting the magnetic flux density at the two separation distances from the magnetic flux density at the plurality of separation distances measured in the magnetic flux density measurement step, determining the difference between the two magnetic flux densities, and determining the positive / negative change, or A nondestructive inspection method comprising a break detecting step of detecting the presence or absence of a broken portion of the reinforcing bar by determining an intersection and a relative position of the change curves of both magnetic flux densities. A nondestructive inspection method for detecting the presence or absence of a broken portion of the reinforcing bar by magnetizing a reinforcing bar provided in the concrete body with a magnet from the outside of the concrete body and then measuring the magnetic flux density on the outside of the concrete body with a magnetic sensor Because
A magnetizing step of placing the magnet close to the surface of the concrete body so that both magnetic poles are along the longitudinal direction of the reinforcing bar, and magnetizing the reinforcing bar by appropriately moving the magnet,
The magnetic sensors are arranged at two positions having different separation distances from the surface of the concrete body, and the magnetic sensors are moved while maintaining the separation distance from the surface of the concrete body substantially constant. A magnetic flux density measuring step for measuring a magnetic flux density along a longitudinal direction of the reinforcing bar at a separation distance;
For the magnetic flux density at the two separation distances measured in the magnetic flux density measurement step, the difference between the two magnetic flux densities is obtained to determine the positive or negative change, or the intersection and relative position of the change curves of the two magnetic flux densities A non-destructive inspection method comprising a break detecting step of detecting the presence or absence of a broken portion of the reinforcing bar by determining   In the magnetic flux density measurement step, a plurality of magnetic sensors are simultaneously arranged and moved at a plurality of positions having different separation distances from the surface of the concrete body, and the magnetic flux along the longitudinal direction of the reinforcing bars at the plurality of separation distances. The nondestructive inspection method according to claim 1, wherein the density is measured simultaneously.   In the magnetic flux density measurement step, one magnetic sensor is sequentially arranged and moved at a plurality of positions having different separation distances from the surface of the concrete body, and the longitudinal direction of the reinforcing bars at the plurality of separation distances is moved. 3. The nondestructive inspection method according to claim 1, wherein the magnetic flux density is measured sequentially. Non-destructive detection of the presence or absence of a broken portion of the reinforcing bar by magnetizing the reinforcing bar provided in the concrete body with a magnet from the outside of the concrete body, and then detecting the magnetism outside the concrete body and calculating the magnetic flux density An inspection device,
A magnet that magnetizes the rebar by moving both poles close to the surface of the concrete body along the longitudinal direction of the rebar, and moving the rebar appropriately.
A plurality of magnetic sensors arranged in a separation direction behind a proximity surface opposed to the surface of the concrete body, and moving the plurality of magnetic sensors simultaneously, Magnetic detection means for simultaneously detecting magnetism at different separation distances;
Magnetic flux density calculating means for calculating magnetic flux density along the longitudinal direction of the reinforcing bars at the plurality of separation distances from detection signals sent from the plurality of magnetic sensors,
By appropriately selecting the magnetic flux density at two separation distances from the magnetic flux density at the plurality of separation distances calculated by the magnetic flux density calculating means, and determining the difference between the two magnetic flux densities to determine the positive or negative change, or A nondestructive inspection apparatus comprising a breakage detecting means for detecting the presence or absence of a broken portion of the reinforcing bar by determining an intersection and a relative position of the change curves of both magnetic flux densities. Non-destructive detection of the presence or absence of a broken portion of the reinforcing bar by magnetizing the reinforcing bar provided in the concrete body with a magnet from the outside of the concrete body, and then detecting the magnetism outside the concrete body and calculating the magnetic flux density An inspection device,
A magnet that magnetizes the rebar by moving both poles close to the surface of the concrete body along the longitudinal direction of the rebar, and moving the rebar appropriately.
Two magnetic sensors arranged in a separation direction behind a proximity surface facing the surface of the concrete body close to each other are provided, and the two magnetic sensors are moved simultaneously so that 2 from the surface of the concrete body Magnetic detection means for simultaneously detecting magnetism at two different separation distances;
Magnetic flux density calculating means for calculating a magnetic flux density along the longitudinal direction of the reinforcing bar at the two separation distances from detection signals sent from the two magnetic sensors;
For the magnetic flux density at the two separation distances calculated by the magnetic flux density calculating means, the difference between the two magnetic flux densities is obtained to determine the positive or negative change, or the intersection and relative position of the change curves of the two magnetic flux densities A non-destructive inspection apparatus, comprising: a break detecting means for detecting the presence or absence of a broken portion of the reinforcing bar by discriminating between the two.   7. The non-magnetic sensor according to claim 5, wherein a plurality of magnetic sensor arrays each including a plurality of magnetic sensors arranged in the separation direction at the rear of the proximity surface are provided as the magnetic detection means. Destructive inspection equipment.