WO2019054158A1 - Nondestructive inspecting device, nondestructive inspecting system, and nondestructive inspecting method - Google Patents

Abstract

The objective of the present invention is to improve the accuracy of detection, by means of a magnetic sensor, of a magnetic field which is generated externally to an object being measured and which has passed through the object being measured, in order to improve the inspection accuracy of nondestructive inspection. A nondestructive inspecting device 1 has a configuration in which one magnetic application unit (3L), a magnetic sensor 21, and another magnetic application unit (3R) are arrayed in this order, magnetic fields having mutually opposite polarities are applied from the magnetic application units to an object being measured which is adjacent to said array and which extends in the same direction as the array, to form a magnetic circuit, and in this state a magnetic field from the object being measured is detected using the magnetic sensor. Each of the magnetic application units has magnets in mainly a Halbach array on the magnetic sensor side thereof as magnetic field adjusting members, as a result of which the magnetic field applied to the magnetic sensor is reduced with respect to the magnetic field applied to the object being measured.

Description

Nondestructive inspection device, nondestructive inspection system and nondestructive inspection method

The present invention relates to nondestructive inspection using magnetism.

The application range of nondestructive inspection using magnetism is diagnosis of fracture due to corrosion or deterioration of magnetic materials such as steel bars and wires, etc. which are enclosed in nonmagnetic materials such as concrete and rubber, especially road and Failure diagnosis of steel bars and reinforcing bars in bridge girder and bridge piers of railways and floor slabs can be mentioned.
As a technique for nondestructively determining breakage of reinforcing bars inside concrete and steel using a conventional magnet, an inspection apparatus based on the leakage flux method has been proposed.
In the conventional magnetic nondestructive inspection system, in the magnetic measurement in the state where the magnetic circuit is formed on the measurement object, the small magnetic field change generated at the fracture site of the measurement object is buried in the large magnetic field produced by the magnet for magnetic circuit generation. Because of this, it is difficult to judge the method, which uses the residual magnetic flux of the object to be measured in a two-step process in which “magnetization” and “measurement” are separated.
For example, in Patent Document 1, as a method by two steps of “magnetization” and “measurement”, after magnetizing with a permanent magnet, the magnet is removed, and a pair of sensors disposed apart in the longitudinal direction are scanned in the longitudinal direction of rebar There is also described a technique for determining and determining a derivative value from the difference between measurement values of two sensors.

In this method of utilizing the residual magnetic flux of the object to be measured, the change in the magnetic field generated on the fracture surface of the object to be measured is small, so it is difficult to catch the change in the magnetic field generated on the fracture site when the fog (embedding depth) of the object to be measured is deep There was a problem called.
On the other hand, if the magnetic circuit is formed on the reinforcing bar which is the measurement object, PC steel material, etc., a large magnetic field change is generated at the fracture site of the measurement object as compared with the conventional method using the residual flux. Since it can be made to do, even if the fog (embedding depth) of the measuring object is deep, there is an effect that it is easy to catch the change of the magnetic field generated at the fracture site.
For example, in Patent Document 2, as a magnetic measurement method in a state where a magnetic circuit is formed on an object to be measured, a pair of magnets having different polarities is disposed to face each other, and the magnetic field of the pair of magnets is zeroed by balance. Techniques for providing a magnetic sensor are described. In the same technology, in a state where a magnetic circuit is formed on a detection target (rebar), inspection is performed while moving in the longitudinal direction of the rebar to determine rebar breakage determination. The judgment principle is that the magnetic force on the side with breakage becomes smaller and the balance collapses. In the technology described in Patent Document 2, the position where the magnetic sensor is provided is limited, and it is impossible to install the magnetic sensor array in which a plurality of magnetic sensors are arranged.

Patent No. 3734822 JP 2004-279372 A

However, in the apparatus and method configured to simultaneously perform "magnetic circuit formation" and "measurement", the magnetic field generated by the magnetic circuit generation magnet for forming the magnetic circuit on the measurement object gives a large magnetic field to the magnetic sensor, On the other hand, since the magnetic field generated from the broken part of the measurement object to the magnetic sensor is small, the magnetic field component generated at the broken part of the measurement object is buried in the magnetic field generated by the aforementioned magnetic circuit generation magnet. There is a problem that becomes difficult.
In the technique described in Patent Document 2 mentioned above, according to the magnetic sensor disposed at a position other than the above “position to be zero”, the magnetic field component generated at the broken part of the measurement object in the magnetic field by the magnet for generating the magnetic circuit There is still a problem that the determination becomes difficult because it is buried.

The present invention has been made in view of the above problems in the prior art, and improves the detection accuracy of the magnetic field generated from the outside of the measurement object via the measurement object by the magnetic sensor, and performs nondestructive inspection inspection. The task is to improve the accuracy.

The invention according to claim 1 for solving the above problems is a nondestructive inspection device in which a magnetic material contained in a nonmagnetic material is an object to be measured,
These are arranged in the order of one magnetic field application unit, magnetic sensor, and the other magnetic field application unit, and the one magnetic field application unit and the one magnetic field application unit for the measurement object adjacent to the array and extending in the same direction. The magnetic sensor is configured to detect a magnetic field from the same measurement object in a state where magnetic fields of opposite polarities are applied from the other magnetic field application unit to form a magnetic circuit,
Each of the magnetic field application units is a nondestructive inspection device in which the magnetic field directed to the magnetic sensor is reduced with respect to the magnetic field applied to the measurement object.

In the invention according to claim 2, each of the magnetic field application units has a main magnet for generating a magnetic field to be applied to the measurement object, and the magnetic sensor among the magnetic field components generated by the main magnet The nondestructive inspection device according to claim 1, further comprising a magnetic field adjusting member having an effect of reducing a magnetic field component to be directed between the main magnet and the magnetic sensor.

The invention according to claim 3 is that the magnetic field adjustment member is a Halbach-arrayed magnet in which three or more magnets having different magnetic directions are combined, and the Halbach-arrayed magnet has a strong magnetic field side due to the effect of Halbach-array. 3. The nondestructive inspection device according to claim 2, wherein the magnetic sensor is disposed so that the side of the weak magnetic field faces the side of the magnetic sensor.

In the invention according to claim 4, in the one magnetic field application unit and the other magnetic field application unit, replacement of the arrangement with respect to the magnetic sensor is enabled, and a pole of a magnetic circuit formed on the object to be measured by the replacement. The nondestructive inspection device according to any one of claims 1 to 3, wherein the direction is made reversible.

The invention according to claim 5 is the non-destructive according to any one of claims 1 to 4, wherein the one magnetic field application unit, the magnetic sensor, and the other magnetic field application unit are arranged on a straight line. It is an inspection device.

In the invention according to claim 6, the magnetic sensor is parallel to a surface adjacent to the measurement object of the array and in the width direction orthogonal to an imaginary line connecting the one magnetic field application unit and the other magnetic field application unit. The nondestructive inspection according to any one of claims 1 to 5, further comprising a slide mechanism capable of sliding relative to the one magnetic field application unit and the other magnetic field application unit. It is an apparatus.

The thickness dimension of the magnetic field adjustment member and the main magnet in the direction perpendicular to the surface adjacent to the measurement object of the array according to the invention of claim 7 is the same as that of claim 2 or 3. It is a nondestructive inspection device.

The invention according to claim 8 is the nondestructive inspection device according to any one of claims 1 to 7, wherein the magnetic sensor is composed of a plurality of magnetic sensors arranged in a predetermined array including a linear array and a staggered array. is there.

In the invention according to claim 9, the magnetic sensor is constituted by a three-axis sensor capable of detecting magnetic field components in three axial directions orthogonal to each other or three single-axis sensors in which sensor axes are respectively arranged in the three axial directions. It is the nondestructive inspection device according to any one of claims 1 to 8.

The invention according to claim 10 is the nondestructive inspection device according to any one of claims 1 to 9, wherein the magnetic sensor is a tunnel type magnetoresistive sensor (TMR sensor).

The invention according to claim 11 comprises the nondestructive inspection device according to any one of claims 1 to 10, and an information processing device,
The information processing apparatus is a nondestructive inspection system that determines an abnormality of the measurement object based on measurement information received from the nondestructive inspection apparatus.

In the invention according to claim 12, the nondestructive inspection device outputs, to the information processing device, surface data indicating a two-dimensional magnetic field distribution on a measurement surface of the measurement object facing the magnetic sensor,
The non-destructive inspection system according to claim 11, wherein the information processing apparatus determines an abnormality of the measurement object based on the surface data.

The invention according to claim 13 uses the nondestructive inspection device according to any one of claims 1 to 10 to make the object to be measured face the magnetic sensor, and the magnetism of the object to be measured Obtain surface data indicating a two-dimensional magnetic field distribution on the measurement surface facing the sensor,
It is a nondestructive inspection method which judges abnormalities of the measurement subject based on the surface data.

According to the present invention, since the magnetic field from the magnetic field application unit toward the magnetic sensor is reduced, the detection accuracy of the magnetic sensor generated from the outside of the measurement object, that is, from the magnetic field application unit and passing through the measurement object Can improve the inspection accuracy of the nondestructive inspection.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram of the nondestructive inspection system which concerns on one Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a whole external view of the nondestructive inspection apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which showed the intensity | strength of the magnetic field by a residual magnetic flux. It is a schematic diagram showing the intensity of the magnetic field generated by the magnetic circuit. It is a schematic diagram of the measurement state by the nondestructive inspection apparatus which concerns on one Embodiment of this invention. It is a schematic diagram for demonstrating the mode of the influence of the magnet magnetic field to a magnetic sensor in a comparative example. It is a schematic diagram for demonstrating the magnetic field reduction effect to the sensor area | region in the nondestructive inspection apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows the combination magnet which concerns on a comparative example, and its magnetic force line. It is a schematic diagram which shows the magnet of Halbach array, and its magnetic force line. It is a schematic diagram of the left magnet unit (left magnetic field application unit) which concerns on one Embodiment of this invention. It is a schematic diagram of the right magnet unit (right magnetic field application unit) which concerns on one Embodiment of this invention. It is a whole external view of the nondestructive inspection device of another example of composition. It is a block diagram of a circuit used for surface data creation with which a sensor unit concerning one embodiment of the present invention is equipped. It is a basic inspection flow of processing of a nondestructive inspection device concerning one embodiment of the present invention, and a nondestructive inspection method.

An embodiment of the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention.

The whole block diagram of the nondestructive inspection system concerning one embodiment of the present invention is shown in FIG.
As shown in FIG. 1, the nondestructive inspection system 10 according to the present embodiment comprises a nondestructive inspection device 1 and a cloud computer 9, and the nondestructive inspection device 1 according to the present embodiment mainly comprises four blocks. The sensor unit 2 which bears the center is a block for measuring the magnetism, and has a plurality of magnetic sensors 21 mounted thereon. The magnetic sensor 21 may be a single-axis sensor that detects a magnetic field component in one axial direction from the measurement object direction, but is more preferably a three-axis sensor that can obtain a three-dimensional magnetic field distribution around the magnetic sensor. The magnetic sensor 21 is known to be a Hall sensor as a semiconductor sensor, an MR sensor as a magnetoresistive sensor, an MI sensor, a TMR sensor (tunnel type magnetoresistive sensor), etc. However, a more sensitive TMR sensor (tunnel type magnetic sensor) It is preferable to apply a resistance sensor). A TMR sensor (tunnel type magnetoresistive sensor) is an element whose resistance value changes due to magnetism, and by combining a resistance bridge circuit, magnetism can be converted into voltage and output.

The voltage generated by the magnetic sensor 21 is converted into a digital value by the A / D unit 22, and measurement data is transmitted to the outside through the mobile communication unit unit 23. The sensor unit 2 is provided with a display unit 25 and an operation unit 26 in addition to the CPU 24 for overall control. The transmitted data is subjected to a determination algorithm by the cloud computer 9 which is an example of the information processing apparatus of the present system, and the state determination of the measurement object is performed.

In the present embodiment, one magnetic field application unit and the other magnetic field application unit correspond to the left magnet unit 3L and the right magnet unit 3R. There is no special distinction between left and right, and the names are based on the left and right on the drawing.
The left magnet unit 3L and the right magnet unit 3R are basically symmetrical in the left-right direction, and are composed of the main magnets 31L, 31R and the magnetic field adjustment members 32L, 32R, respectively.
The polarities of the left and right main magnets 31L, 31R are opposite to each other, and the lower surface of the main magnets 31L, 31R, which is the opposing surface of the object to be measured, has N poles on one side and S poles on the other. As the magnetic field adjustment members 32L and 32R, a combination of a Halbach arrangement and a magnet is employed.

The sensor unit 2 and the left and right magnet units 3L and 3R are connected by the support mechanism 4 and held.
The support mechanism 4 not only holds the sensor unit 2 and the left and right magnet units 3L and 3R, but also has a mechanism for causing the sensor unit 2 and the left and right magnet units 3L and 3R to slide relative to each other. Enable magnetic measurement of

The whole external view of the nondestructive inspection apparatus 1 of this embodiment is shown in FIG.
As shown in FIG. 2, the sensor unit 2 is disposed at the center of the support mechanism 4, and the sensor unit 2 can slide in the width direction X. The left and right magnet units 3 </ b> L and 3 </ b> R are disposed at both ends of the central portion of the support mechanism 4 in the Y direction. Further, the support mechanism 4 is provided with a grip 41 so that the whole nondestructive inspection apparatus 1 can be stably held when carrying the whole of the nondestructive inspection apparatus 1 or when it is applied to an object to be measured.

The schematic diagram which compared the intensity | strength of the magnetic field by a residual magnetic flux and the magnetic field generate | occur | produced by a magnetic circuit to FIG. 3A and B is shown.
FIG. 3A simulates the state after magnetization in a two-step procedure in which the conventional magnetization and measurement are performed separately. The measurement object 8 assumes a reinforcing steel bar or PC steel material which is a magnetic material, and assumes a state in which a break of about 1 cm in gap is generated at the central portion (not shown non-magnetic material (concrete)) .same as below).
The object to be measured 8 is in the state of a weak bar magnet which is magnetized by magnetization. In FIGS. 3A and 3B, the left end portion is magnetized to the N pole and the right end portion side to the S pole, and a leftward magnetic loop leakage magnetic field from the N extreme portion to the S extreme portion is generated in the gap portion of the fracture portion. However, in the method of separately performing the conventional magnetization and measurement in FIG. 3A, it is left to the residual magnetic characteristics of the object to be measured 8, and in the case of a general iron material which is not a magnet material, it emits only a very weak magnetism, The magnetic flux density of the leaked magnetic field is also small.

FIG. 3B simulates the formation of a magnetic circuit according to the measurement principle of the present invention.
Similarly, assuming that the measurement object 8 is a reinforcing steel bar or PC steel, it is assumed that a break of about 1 cm in gap is generated at the central portion. The measurement object 8 is in a state in which a magnetic circuit is formed inside the measurement object 8 by the magnetism of the magnet units 3L and 3R arranged above the left and right ends. The magnetism emitted from the N pole of the right magnet unit 3R gathers at the measurement object 8 which is a magnetic body and passes through the inside, and then flows to the S pole of the left magnet unit 3L. As in FIG. 3A, a leftward magnetic loop-like leaked magnetic field is generated from the N extreme part to the S extreme part at the gap part in the middle of the broken part. However, since the amount of magnetic flux flowing into the measuring object 8 by the magnetic circuit is larger than the amount of magnetic flux due to the residual magnetic flux, the magnetic flux density of the break gap also increases, resulting in a magnetic loop leakage magnetic field resulting in the break gap. Will also be strong.

For example, two reinforcing bar deformed steel rods with a length of 1 m and a diameter of 16 mm as the measurement object 8 are separated by about 1 mm with a gap of about 10 mm assuming the fracture site and facing each other in the longitudinal direction. Arrange 3R. As each magnet unit 3L, 3R, one in which a low carbon steel of 52 mm × 52 mm × 25 mm as a yoke material is brought into contact with one surface of a 52 mm × 52 mm × 25 mm neodymium magnet is applied, and magnet units 3L, 3 R A magnetic circuit is formed by disposing 300 mm above the position of 25 cm on each side in the longitudinal direction (Y direction) from the fracture site of the deformed steel bar. In this case, a magnetic flux density of about 16 mT is generated at the central part of the gap cross section of the fractured part in the state shown in FIG. 3B in which the magnetic circuit is formed. When the magnet units 3L and 3R are removed from this state and the state as shown in FIG. 3A is obtained, a constant magnetic flux density is obtained at the center of the gap section of the broken portion of the deformed steel bar due to the residual magnetic characteristics of the deformed steel bar. Remains, but the value only produces a flux density of around 2 mT.

Thus, the method of forming the magnetic circuit can generate a large leakage flux at the fracture site as compared with the method of utilizing the residual magnetic flux.
Therefore, in the present invention, the nondestructive inspection of the deep fog measurement object 8 is enabled by using the method of forming the magnetic circuit on the measurement object 8. For example, in a device utilizing the conventional magnetic flux leakage flux method which performs magnetization and measurement in two steps, since the leaked magnetic flux is weak, the cover depth at which breakage of the object to be measured 8 can be determined is about 200 mm. On the other hand, in the method of forming the magnetic circuit of the present invention, since the leakage magnetic flux is strong, breakage can be detected even when the fog exceeds 200 mm.
It is also known that PC steels that require high tension generally have smaller residual magnetic properties than crude irons such as rebar steel rods, and PC steels that are often placed in deep-cover positions For the determination of breakage, a method of determining the breakage while forming the magnetic circuit of the present invention is preferable.

The schematic diagram of the measurement state of the nondestructive inspection apparatus 1 of this embodiment is shown in FIG.
FIG. 4 is a schematic view in which the sensor unit 2 is disposed at the center, and the magnet units 3L and 3R are disposed at the left and right, and shows that they are disposed adjacent to the measurement object 8 to form a magnetic circuit. . That is, these are arranged in the order of the magnet unit 3L, the magnetic sensor 21, and the magnet unit 3R, and the magnet unit 3L is placed on the measurement object 8 adjacent to the array and extending in the same direction (Y direction). A magnetic circuit is formed by applying magnetic fields of opposite polarities to each other from 3R, and in this state, the magnetic sensor 21 detects the magnetic field from the object to be measured 8. The direction in which the object to be measured extends in the Y direction is not limited to the longitudinal direction of the object, and the magnet units 3L and 3R oppose the left and right magnet units even when the width direction of the strip is Y direction. It is measurable if it is long.
In the example shown in FIG. 4, a main rebar (PC steel) is disposed below the sensor unit 2 and the magnet units 3L and 3R as rod-like magnetic materials which are the measurement object 8, and one magnet unit (3R) is generated A magnetic circuit is formed in which the magnetism flows into the other magnet unit (3L) through the main rebar.

If the main rebar of the measuring object 8 has a broken part below the sensor unit 2, the end faces of the S pole and the N pole are generated at the broken part, and a looped magnetic field is generated around the broken part.
If the magnetic sensor 21 of the sensor unit 2 is a disturbance of the magnetic loop generated at the broken portion of the main rebar, it is vertical direction (Z direction) in the case of a single axis sensor, vertical direction in the case of a three axis sensor, left and right, front and back direction (XYZ direction The magnetic field component of) is detected. Although not shown, when the main rebar is not broken, the magnetic sensor 21 does not detect the disturbance because the disturbance of the magnetic loop occurring at the broken part does not occur. When a three-axis sensor is applied as the magnetic sensor 21, a three-axis sensor capable of detecting magnetic field components in three axis directions orthogonal to each other is preferable, but three single axes in which sensor axes are respectively arranged in the three axis directions It may be configured by a combination of sensors.
In FIG. 4, the crossing rebar (starlap) 7 is arranged in parallel with the main rebar (8), but since it is arranged in parallel with the magnetic circuit, a large disturbance of the magnetic field occurs to the extent that it interferes with the measurement. There is no.

FIGS. 5 and 6 show schematic diagrams for explaining the influence of the magnetic field of the magnet on the magnetic sensor 21 for explaining the measurement principle of the present invention.
FIG. 5 shows the configuration of the comparative example, and normal main magnets 31L and 31R are disposed on the left and right of the magnetic sensor 21. As shown in FIG. The bottom main surface side of the left main magnet 31L is an S pole, and the top surface side is an N pole. Inside the magnet, a magnetic flux is generated from the bottom surface side toward the top surface side. At the outside of the magnet, the magnetism emitted from the top surface of the N pole returns to the S pole of the bottom surface in a loop. An upward magnetic field is generated at the bottom of the magnet. The right main magnet 31R is reverse to the above, and the bottom side is N pole and the top side is S pole, and inside the magnet, magnetic flux is generated from the top side toward the bottom side. Outside the magnet, the magnetism emitted from the bottom of the north pole returns to the top south pole so as to form a loop. A downward magnetic field is generated at the bottom of the magnet.

In the case of the comparative example shown in FIG. 5, the external magnetic field generated around the left and right main magnets 31L, 31R is also exposed to the strong magnetic field in the downward direction at the position near the left main magnet 31L. At a position near the magnet 31R, it is exposed to a strong magnetic field in the upward direction. In the nondestructive inspection device 1 of the present embodiment, it is not preferable that the magnetic sensor 21 be directly exposed to the magnetic field of the magnet as described above because it is necessary to capture minute changes in the magnetic field generated at the fracture site of the measurement object. Therefore, they are configured as shown in FIG.

The schematic diagram for demonstrating the magnetic field reduction effect to the sensor area | region in FIG. 6 in the nondestructive inspection apparatus 1 of this embodiment is shown. Similar to the comparative example of FIG. 5, the normal main magnets 31L and 31R are disposed on the left and right of the magnetic sensor 21, and the magnetic field adjustment members 32L and 32R are disposed between the left and right main magnets 31L and 31R and the magnetic sensor 21. It is done. On the outside of the left main magnet 31L, the magnetism emitted from the upper surface of the N pole returns to the S pole of the bottom so as to draw a loop, but on the side where the magnetic field adjusting member 32L is disposed, the magnetic field adjusting member 32L becomes a wall, The magnetic sensor 21 is prevented from being exposed to strong magnetism. Similarly, outside the right main magnet 31R, the magnetism emitted from the bottom of the N pole returns to the S pole of the upper surface so as to draw a loop, but on the side where the magnetic field adjusting member 32R is disposed, the magnetic field adjusting member 32R is on the wall Thus, the magnetic sensor 21 is prevented from being exposed to strong magnetism.

As described above, the magnetic sensor 21 is prevented from being directly exposed to the magnetic field of the magnet by the effects of the magnetic field adjustment members 32L and 32R, and the minute change in the magnetic field generated at the fracture site of the measurement object is accurately performed by the magnetic sensor 21. It becomes possible to capture.

FIGS. 7A and 7B show schematic diagrams for explaining the effect of the Halbach array magnet.
As is well known, in general, the faces of the N pole and the S pole of the magnet face each other, and the amount of magnetic flux generated at the pole face of the magnet is the same except for the direction of the magnetism. FIG. 7A shows a comparative example, in which the magnets are arranged side by side simply by alternately switching the upper and lower polarities alternately, and the strengths of the magnetic fields generated on the upper surface side and the lower surface side are the same.
FIG. 7B is a schematic view of the case where the magnets are arranged in the Halbach arrangement. As shown in FIG. 7B, five magnets are arranged side by side while turning the direction of magnetization at 90 degrees from top to bottom, left to right, bottom to top, right to left, top to bottom, and magnetization from the left. As a result, since a magnetic circuit is formed inside the magnet on the lower surface side of the Halbach array of assembled magnets, only a slight magnetic force is generated outside the magnet. On the other hand, since a large portion of the S pole and the N pole is formed on the upper surface side of the Halbach array magnet, a strong magnetic field loop is generated outside the magnet. When the magnets are arranged in the Halbach arrangement as described above, the magnetic field is concentrated on one side, and a large magnetic force can be extracted. Generally, the effective use of the Halbach array magnet is to utilize the magnetic force on this large side, but in the present embodiment, the surface on the small magnetic field side is directed to the sensor side to utilize it as the magnetic shield effect.

FIGS. 8A and 8B show examples of effective combination arrangements of the main magnet and the Halbach magnet.
The magnet units 3L and 3R used in the present embodiment have a left-right symmetric configuration with a left-right pair. The magnet units 3L and 3R are roughly divided into main magnets 31L and 31R, Halbach magnets (32L and 32R), a yoke 33, and a spacer 34. The main magnets 31L and 31R are for forming a magnetic circuit on an object to be measured, and thus are realized using four neodymium magnets of approximately 50 mm square and 25 mm thickness, for example. The Halbach magnet (32L, 32R) is configured by combining three neodymium magnets, and is disposed so that the side of the strong magnetic field faces the main magnet and the side of the weak magnetic field faces outward facing the magnetic sensor 21. Specifically, in the case of the left magnet unit 3L (FIG. 8A), the main magnet 31L is disposed such that the N pole side is the bottom surface. The middle magnet of Halbach magnet (32L) has the N pole facing the main magnet, and the upper and lower magnets of Halbach magnet (32L) are arranged with the N pole side facing the middle magnet of Halbach magnet (32L) Ru. On the other hand, in the case of the right magnet unit 3R (FIG. 8A), the N pole and the S pole are replaced.
By arranging the Halbach magnets (32L, 32R) in this manner, the magnetic fields of the main magnets 31L, 31R are suppressed by the magnetic fields of the Halbach magnets (32L, 32R), and the magnetic force directed to the magnetic sensor 21 is reduced. That is, the magnetic field directed to the magnetic sensor 21 is reduced while the magnetic field applied to the measurement object 8 is intensified. Therefore, in the nondestructive inspection device 1, the magnetic field directed to the magnetic sensor 21 is reduced with respect to the magnetic field applied to the measurement object 8. Therefore, the magnetic sensor 21 can accurately detect the magnetic field component from the measurement object 8 without embedding it in the magnetic field directed from the magnet units 3L and 3R to the magnetic sensor 21.

The yoke 33 is provided for the effect of enhancing the magnetic force in the downward direction of the main magnets 31L and 31R and for adsorbing a plurality of magnets to stably fix each of them. Further, since the spacers 34 can not be disposed adjacent to each other because the repulsive forces of the respective magnets are too strong, they are used as spacing members for disposing the magnets at a predetermined distance apart. The magnet units 3L and 3R have the same thickness dimensions of the magnetic field adjustment members 32L and 32R and the main magnets 31L and 31R in the Z direction, and a sufficient size between the main magnets 31L and 31R and the magnetic sensor 21. The magnetic field adjusting members 32L and 32R are arranged in a space effective manner.
In order to form a magnetic circuit as strong as possible, neodymium magnets are preferably adopted as the main magnets 31L, 31R, and Halbach magnets (32L, 32R) for adjusting the magnetic field of the strong main magnets are also neodymium magnets. It is preferable to adopt the same, but the same effect can be obtained with an inexpensive ferrite magnet.

FIG. 9 shows another configuration example of the nondestructive inspection device.
In the configuration example shown in FIG. 2, a slide mechanism is provided to move the magnetic sensors 21 of the sensor unit 2 in the width direction (X direction) as a one-dimensional array in the Y direction. In the configuration example shown in FIG. 9, the slide mechanism is eliminated, and the magnetic sensor 21 is two-dimensionally arranged on the XY plane in the sensor unit 2. By arranging the magnetic sensors 21 in a two-dimensional manner, it is not necessary to perform measurement a plurality of times while changing the sensor position in the width direction (X direction) appropriately using a slide mechanism. Plane data indicating a two-dimensional magnetic field distribution on the measurement plane (XY plane) facing the sensor 21 can be obtained.

In the nondestructive inspection device 1 shown in FIG. 2 or 9, replacement of the arrangement of the magnetic sensor 21 with one magnetic field application unit (3L) and the other magnetic field application unit (3R) is made possible. It is preferable to implement a configuration in which the pole direction of the magnetic circuit formed on the measurement object is reversible. As a result, without changing the relative arrangement of the object to be measured and the magnetic sensor 21, the pole directions of the magnetic circuit can be made opposite to each other, and two plane data can be acquired. When the nondestructive inspection device 1 is inverted as a whole, the sensor unit 2 is also inverted, so the relative arrangement between the object to be measured and the magnetic sensor 21 changes, and variations in the sensor characteristics of the elements of the magnetic sensor 21 occur. This is because the amount of change is superimposed on the surface data.
The structure to make it reversible may simply remove the two magnet units 3L and 3R from the support mechanism 4 once, replace them, and reattach them to the support mechanism 4. In addition, two magnet units 3L, such as a mechanism in which a sub-frame supporting two magnet units 3L, 3R is provided independently, and the same sub-frame is rotatably connected to a main frame supporting the sensor unit 2 etc. You may comprise the mechanism which can be reversed without removing 3R from the support mechanism 4. FIG.
Although FIG. 9 shows an example in which the sensors are arranged in a square lattice, the method of two-dimensional arrangement of the sensors may be a checkerboard arrangement or the like, and is not limited to the square lattice arrangement.

FIG. 10 shows a block diagram of a circuit used to generate surface data provided in the sensor unit 2.
As shown in FIG. 10, the one-line portion 2a of the circuit is provided with a plurality of magnetic sensors 21 arranged in the one-line portion 2a shown also in FIGS. 2 and 9, and each magnetic sensor 21 amplifies a signal. There is an amplifier 21a, an A / D unit 22 that digitizes a signal, and a line data unit 2b that rearranges data of one row of magnetic sensors 21 into a line. In addition, how to arrange several magnetic sensor 21 is linear form, zigzag arrangement, etc. is arbitrary.
In the device configuration shown in FIG. 2, there is a single line portion 2a and a slide mechanism for moving the sensor unit 2 in the X direction, and another line at a place where the sensing position by the one line portion 2a is changed by the slide mechanism. Get data Line data at multiple sensing positions are collected sequentially and converted to surface data in the surface data unit 2c. Further, in the apparatus configuration shown in FIG. 9, there is a required number of one-line portions 2a that can be acquired at one time without movement, and surface data can be acquired at one time. The surface data generated by the surface data unit 2 c is transmitted to the cloud computer 9 as described above, processed by the cloud computer 9, and state determination such as presence or absence of breakage of the measurement object 8 is performed.

FIG. 11 shows a basic inspection flow of the processing of the nondestructive inspection device of the present embodiment and the nondestructive inspection method. This is the case where the nondestructive inspection device 1 shown in FIG. 2 is used.
(Step S1) The nondestructive inspection device 1 is installed so that the magnetic sensor 21 faces the surface of the measurement object 8 in proximity to the surface, and a magnetic field is applied from the magnet units 3L and 3R to make a magnetic circuit on the measurement object 8 Form
(Step S2) The magnetic sensor 21 detects the magnetic flux from the measurement object 8 in the magnetic circuit formation state in step S1.
(Step S3) The sensor unit 2 is shifted in the width direction (X direction) without changing the position of the nondestructive inspection device 1.
(Step S4) It is determined whether measurement at all shift positions is completed, and if it is not completed, the process returns to step S2. If it has been completed, the process proceeds to step S4.
(Step S5) From the data sampled at all shift positions, the magnetic field distribution of the entire measurement surface is created. The data at this time is plane data of one axis in the case of a single-axis sensor, and plane data of three axes in the case of a three-axis sensor.
(Step S6) The generated surface data is analyzed to determine whether or not the magnetic field is disturbed due to breakage or corrosion of the object to be measured, and if there is any disturbance in the magnetic field, it is estimated as an abnormal site such as breakage or corrosion. This completes the series of measurements.
When the nondestructive inspection device 1 shown in FIG. 9 is used, there is no circulation process of steps S2, S3 and S4, and surface data is acquired at one time.

Based on the created surface data, the abnormality determination is performed by the processing of the cloud computer 9.
When the measurement object is normal and continuity is maintained, no large local magnetic field change occurs. Conversely, when breakage or corrosion occurs in the object to be measured and the continuity is lost, a local rapid magnetic field change occurs in the site. As an example of the abnormality determination, there is a determination method based on the difference value between the magnetic field strength value at the coordinate of interest and the magnetic field strength value around it. For example, the difference between the magnetic field strength values of all or arbitrary coordinates on the surface data and the magnetic field strength values of the four coordinates before and after it is calculated, and the inclination obtained by dividing this by the magnetic field strength value of the coordinates of interest is calculated The presence or absence of abnormality is determined based on whether the absolute value of the slope exceeds a predetermined value. That is,
Forward inclination = | (value of target coordinates-value of previous coordinates) / value of target coordinates) |
Backward tilt = | (value of target coordinates-value of back coordinates) / value of target coordinates) |
Left tilt = | (value of the target coordinate-value of the left coordinate) / value of the target coordinate) |
Right inclination = | (value of target coordinates-value of right coordinates) / value of target coordinates) |
As one of the four values, if it exceeds a predetermined threshold (for example, 0.3), it is determined that there is an abnormality near the coordinate of interest. It is preferable that the determination is performed on all the magnetic field strength values in the three axial directions in the case of the single axis sensor, and in the case of the three axial sensors, in the case of the three axis sensor. At this time, it is preferable that the predetermined threshold be set in accordance with the detection pitch and the axial direction of the magnetic field component.
Note that the information processing apparatus that determines the abnormality of the measurement object based on the surface data is not limited to the cloud computer 9, but may be a computer connected one-to-one to the nondestructive inspection apparatus or integrated with the nondestructive inspection apparatus There is no limitation on the hardware configuration, such as a computer mounted on a computer. Processing in one station of the cloud computer 9 is advantageous in terms of information accumulation, uniform processing, use, and the like.

As described above, the effect of blocking the magnetic force of the main magnet applied to the magnetic sensor is obtained by arranging the Halbach magnet with the side of the strong magnetic field facing the main magnet and the side of the weak magnetic field facing the magnetic sensor. Can be generated. As a result, since the magnetic field from the magnetic field application unit toward the magnetic sensor is reduced, the detection accuracy of the magnetic sensor generated from the outside of the measurement object, that is, from the magnetic field application unit and passing through the measurement object is improved. The inspection accuracy of nondestructive inspection can be improved.

Regardless of the above embodiments, each of the magnetic field application units only needs to reduce the magnetic field directed to the magnetic sensor with respect to the magnetic field applied to the measurement object, the low value represented by SS400 as a magnetic field adjustment member The method of arranging a magnetic shield made of carbon steel and the method of arranging a small magnet for repelling magnetism also have certain effects. However, the magnetic shielding method has the disadvantage that the shield absorbs even the components of the magnetic circuit, and the method of arranging the repelling magnet makes it difficult to optimize the strength setting and the arrangement of the repelling magnet. The method of arrange | positioning a Halbach magnet as an adjustment member is preferable.
In addition, each of the magnetic field application units may be arranged with only the Halbach magnet in the magnetic field application unit, as long as the magnetic field directed to the magnetic sensor is reduced with respect to the magnetic field applied to the measurement object. Also in this case, if the side of the weak magnetic field in FIG. 7B of the Halbach magnet is made to face the magnetic sensor side, the magnetic field directed to the magnetic sensor is reduced with respect to the magnetic field applied from the Halbach magnet to the measurement object. However, in order to make the magnetic field applied to the object to be measured stronger, it is preferable to arrange the main magnet in addition to the Halbach magnet as in the above embodiment.

INDUSTRIAL APPLICABILITY The present invention can be used for a nondestructive inspection device such as a reinforcing bar embedded in concrete, a nondestructive inspection system, and a nondestructive inspection method.

DESCRIPTION OF SYMBOLS 1 Nondestructive inspection device 2 Sensor unit 3L, 3R Magnet unit 4 Support mechanism 8 Measurement object 9 Cloud computer (information processing device)
DESCRIPTION OF SYMBOLS 10 Nondestructive inspection system 21 Magnetic sensor 31L, 31R Main magnet 32L, 32R Magnetic field adjustment member 33 Yoke 34 Spacer 41 Grip

Claims (13)

1. A nondestructive inspection apparatus in which a magnetic material contained in a nonmagnetic material is an object to be measured,
   These are arranged in the order of one magnetic field application unit, magnetic sensor, and the other magnetic field application unit, and the one magnetic field application unit and the one magnetic field application unit for the measurement object adjacent to the array and extending in the same direction. The magnetic sensor is configured to detect a magnetic field from the same measurement object in a state where magnetic fields of opposite polarities are applied from the other magnetic field application unit to form a magnetic circuit,
   Each of the said magnetic field application units is a nondestructive inspection apparatus with which the magnetic field which goes to the said magnetic sensor is reduced with respect to the magnetic field applied to the said measuring object.
2. Each of the magnetic field application units has a main magnet for generating a magnetic field to be applied to the measurement object, and among the magnetic field components generated by the main magnet, the effect of reducing the magnetic field component toward the magnetic sensor is obtained. The nondestructive inspection device according to claim 1, having a configuration in which a magnetic field adjustment member is disposed between the main magnet and the magnetic sensor.
3. The magnetic field adjustment member is a Halbach-arrayed magnet in which three or more magnets having different magnetic directions are combined, and the Halbach-arrayed magnet causes the side of the strong magnetic field due to the Halbach-array effect to face the main magnet The nondestructive inspection device according to claim 2, wherein the weak magnetic field side is disposed to face the magnetic sensor side.
4. The one magnetic field application unit and the other magnetic field application unit can be interchanged in arrangement with respect to the magnetic sensor, and the pole direction of the magnetic circuit formed on the object to be measured can be reversed by the interchange. The nondestructive inspection device according to any one of claims 1 to 3.
5. The nondestructive inspection device according to any one of claims 1 to 4, wherein the one magnetic field application unit, the magnetic sensor, and the other magnetic field application unit are disposed on a straight line.
6. The magnetic sensor and the one magnetic field application unit in a width direction perpendicular to a virtual line connecting the one magnetic field application unit and the other magnetic field application unit in parallel with a surface adjacent to the measurement object of the array. The nondestructive inspection device according to any one of claims 1 to 5, further comprising: a slide mechanism capable of sliding relative to the other magnetic field application unit.
7. The nondestructive inspection apparatus according to claim 2 or 3, wherein the thickness dimensions of the magnetic field adjustment member and the main magnet in the direction perpendicular to the surface adjacent to the measurement object of the array are the same.
8. The nondestructive inspection device according to any one of claims 1 to 7, wherein the magnetic sensor comprises a plurality of magnetic sensors arranged in a predetermined array including a linear array and a staggered array.
9. The magnetic sensor is constituted by a three-axis sensor capable of detecting magnetic field components in three axial directions orthogonal to each other or three one-axis sensors in which sensor axes are arranged in the respective three axial directions. The nondestructive inspection device according to any one of 8.
10. The nondestructive inspection device according to any one of claims 1 to 9, wherein the magnetic sensor is a tunnel type magnetoresistive sensor (TMR sensor).
11. A nondestructive inspection device according to any one of claims 1 to 10, and an information processing device,
    The nondestructive inspection system, wherein the information processing device determines an abnormality of the measurement object based on measurement information received from the nondestructive inspection device.
12. The nondestructive inspection device outputs, to the information processing device, surface data indicating a two-dimensional magnetic field distribution on a measurement surface of the measurement object facing the magnetic sensor,
    The non-destructive inspection system according to claim 11, wherein the information processing apparatus determines an abnormality of the measurement object based on the surface data.
13. The nondestructive inspection device according to any one of claims 1 to 10, the measurement object is made to face the magnetic sensor, and 2 on the measurement surface of the measurement object facing the magnetic sensor Get surface data showing the dimensional magnetic field distribution,
    The nondestructive inspection method which determines abnormality of the said measurement object based on the said surface data.

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