JPWO2019054158A1 - Non-destructive inspection equipment, non-destructive inspection system and non-destructive inspection method - Google Patents

Abstract

Improve the detection accuracy of the magnetic field generated from the outside of the measurement object and pass through the measurement object by the magnetic sensor, and improve the inspection accuracy of non-destructive inspection. In the non-destructive inspection device 1, one magnetic field application unit (3L), the magnetic sensor 21, and the other magnetic field application unit (3R) were arranged in this order, adjacent to the same arrangement and extending in the same direction as the same arrangement. The magnetic field application unit has a configuration in which a magnetic sensor detects the magnetic field from the measurement object in a state where magnetic circuits of opposite polarities are applied to the measurement object from these magnetic field application units to form a magnetic circuit. By arranging the magnets arranged in Halbach mainly on the magnetic sensor side as the magnetic field adjusting member, the magnetic field toward the magnetic sensor is reduced with respect to the magnetic field applied to the object to be measured.

Description

The present invention relates to non-destructive inspection using magnetism.

The scope of application of non-destructive inspection using magnetism is the diagnosis of breakage due to corrosion or deterioration of magnetic materials such as reinforcing bars, steel rods, and wires contained in non-magnetic materials such as concrete and rubber, especially roads and roads. Examples include fracture diagnosis of PC steel materials and reinforcing bars in railway bridge girders, bridge pedestals, and floor slabs.
An inspection device using the leakage flux method has been proposed as a non-destructive technique for determining breakage of reinforcing bars and PC steel materials inside concrete using conventional magnetism.
In the conventional magnetic non-destructive inspection system, in the magnetic measurement in the state where the magnetic circuit is formed on the object to be measured, the small magnetic field change generated at the fracture site of the object to be measured is buried in the large magnetic field generated by the magnet for generating the magnetic circuit. Therefore, it is difficult to make a determination, and a method of utilizing the residual magnetic field of the object to be measured by a two-step process in which "magnetization" and "measurement" are separated is adopted.
For example, in Patent Document 1, as a method based on two steps of "magnetization" and "measurement", after magnetizing with a permanent magnet, the magnet is removed and a pair of sensors spaced apart from each other in the longitudinal direction are scanned in the longitudinal direction of the reinforcing bar. However, a technique for determining a differential value from the difference between the measured values of the two sensors is described.

In this method using the residual magnetic flux of the object to be measured, the change in the magnetic field that occurs in the fracture surface of the object to be measured is small, so it is difficult to capture the change in the magnetic field that occurs at the fracture site when the object to be measured has a deep cover (burial depth). There was a problem.
On the other hand, if a magnetic circuit is formed on the reinforcing bar or PC steel material that is the object to be measured, a large magnetic field change is generated at the fracture site of the object to be measured as compared with the conventional method that uses the conventional residual magnetic flux. Therefore, even when the object to be measured is deeply fogged (buried depth), there is an effect that it is easy to catch the change in the magnetic field generated at the fractured part.
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 are arranged facing each other, and the magnetic field of the pair of magnets becomes zero due to balance. A technique for providing a magnetic sensor is described. In this technique, in a state where a magnetic circuit is formed on an object to be detected (reinforcing bar), an inspection is performed while moving the reinforcing bar in the longitudinal direction to determine a reinforcing bar breakage. The judgment principle is that the magnetic force on the side with the break becomes smaller and the equilibrium is lost. In the technique described in Patent Document 2, the position where the magnetic sensor is provided is limited, and the magnetic sensor ray in which a plurality of magnetic sensors are arranged cannot be installed.

Japanese Patent No. 3734822 Japanese Unexamined Patent Publication No. 2004-279372

However, in the device and method having a configuration in which "magnetic circuit formation" and "measurement" are performed at the same time, the magnetic field generated by the magnetic circuit generation magnet for forming the magnetic circuit on the object to be measured has a large magnetic field applied to the magnetic sensor. On the other hand, since the magnetic field generated at the break site of the measurement target has a small magnetic field applied to the magnetic sensor, the magnetic field component generated at the break site of the measurement target is buried in the magnetic field generated by the magnetic circuit generation magnet described above. There is a problem that it becomes difficult.
In the technique described in Patent Document 2 described above, according to the magnetic sensor arranged at a position other than the above "position where it becomes zero", the magnetic field component generated at the fractured portion of the object to be measured is generated in the magnetic field generated by the magnet for generating the magnetic circuit. There is still the problem that the judgment 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 and passed through the measurement object by the magnetic sensor, and inspects the non-destructive inspection. The challenge is to improve accuracy.

The invention according to claim 1 for solving the above problems is a non-destructive inspection apparatus in which a magnetic material contained in a non-magnetic material is used as a measurement object.
One of the magnetic field application units, the magnetic sensor, and the other magnetic field application unit are arranged in this order, and the one magnetic field application unit and the said magnetic field application unit are applied to a measurement object adjacent to the same arrangement and extending in the same direction as the same arrangement. It has a configuration in which the magnetic sensor detects the magnetic field from the measurement target in a state where magnetic circuits 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 non-destructive inspection device in which the magnetic field directed toward 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 applied to the measurement object, and among the magnetic field components generated by the main magnet, the magnetic sensor has a magnetic sensor. The non-destructive inspection device according to claim 1, wherein a magnetic field adjusting member having an effect of reducing an oncoming magnetic field component is arranged between the main magnet and the magnetic sensor.

According to the third aspect of the present invention, the magnetic field adjusting member is a Halbach array magnet in which three or more magnets having different magnetic directions are combined, and the Halbach array magnet is a strong magnetic field side surface due to the effect of the Halbach array. The non-destructive inspection device according to claim 2, wherein is arranged so that the main magnet side faces the main magnet side and the weak magnetic field side surface faces the magnetic sensor side.

According to the fourth aspect of the present invention, the one magnetic field application unit and the other magnetic field application unit can be rearranged with respect to the magnetic sensor, and the poles of the magnetic circuit formed on the measurement object by the replacement. The non-destructive inspection apparatus according to any one of claims 1 to 3, wherein the orientation can be reversed.

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

The invention according to claim 6 is the magnetic sensor in a width direction parallel to a plane adjacent to the measurement object in the arrangement and orthogonal to a virtual line connecting the one magnetic field application unit and the other magnetic field application unit. The non-destructive inspection according to any one of claims 1 to 5, which has a slide mechanism capable of sliding the one magnetic field application unit and the other magnetic field application unit relative to each other. It is a device.

The invention according to claim 7 is the invention according to claim 2 or 3, wherein the magnetic field adjusting member and the main magnet having the same thickness dimension in the direction perpendicular to the plane adjacent to the measurement object in the arrangement. It is a non-destructive inspection device.

The invention according to claim 8 is the non-destructive inspection apparatus 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 arrangement including a line shape and a staggered arrangement. is there.

According to the invention of claim 9, the magnetic sensor is composed of a three-axis sensor capable of detecting magnetic field components in the three-axis directions orthogonal to each other or three one-axis sensors in which sensor axes are arranged in the three-axis directions. The non-destructive inspection apparatus according to any one of claims 1 to 8.

The invention according to claim 10 is the non-destructive inspection apparatus according to any one of claims 1 to 9, wherein the magnetic sensor is a tunnel type reluctance sensor (TMR sensor).

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

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

The invention according to claim 13 uses the non-destructive inspection device according to any one of claims 1 to 10 to make the measurement object face the magnetic sensor, and the magnetism of the measurement object. Obtaining surface data showing the two-dimensional magnetic field distribution on the measurement surface facing the sensor,
This is a non-destructive inspection method for determining an abnormality of the measurement object based on the surface data.

According to the present invention, since the magnetic field from the magnetic field application unit to the magnetic sensor is reduced, the detection accuracy of the magnetic field generated from the outside of the measurement object, that is, the magnetic field application unit and passing through the measurement object by the magnetic sensor. Can be improved and the inspection accuracy of non-destructive inspection can be improved.

It is an overall block diagram of the nondestructive inspection system which concerns on one Embodiment of this invention. It is an overall external view of the nondestructive inspection apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which showed the strength of the magnetic field by the residual magnetic flux. It is a schematic diagram which showed the strength of the magnetic field generated by a 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 influence of the magnetic magnetic field on a magnetic sensor with respect to a comparative example. It is a schematic diagram for demonstrating the magnetic field reduction effect to the sensor 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 the magnetic field line thereof. It is a schematic diagram which shows the magnet of the Halbach array and the magnetic field 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 an overall external view of the non-destructive inspection apparatus of another configuration example. It is a block diagram of the circuit used for creating surface data provided in the sensor unit which concerns on one Embodiment of this invention. It is a basic inspection flow of the processing of the nondestructive inspection apparatus and the nondestructive inspection method which concerns on one Embodiment of this invention.

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

FIG. 1 shows an overall configuration diagram of a non-destructive inspection system according to an embodiment of the present invention.
As shown in FIG. 1, the non-destructive inspection system 10 of the present embodiment includes a non-destructive inspection device 1 and a cloud computer 9, and the non-destructive inspection device 1 of the present embodiment is mainly composed of four blocks. The sensor unit 2 that plays a central role is a block for magnetic measurement, and is equipped with a plurality of magnetic sensors 21. The magnetic sensor 21 may be a 1-axis sensor that detects a magnetic field component in the 1-axis direction from the direction of the object to be measured, but a 3-axis sensor that can obtain a three-dimensional magnetic field distribution around the magnetic sensor is more preferable. Known magnetic sensors 21 include Hall elements, which are semiconductor sensors, MR sensors, MI sensors, and TMR sensors (tunnel-type magnetic resistance sensors), which are magnetic resistance sensors, but more sensitive TMR sensors (tunnel-type magnetometers). It is preferable to apply a resistance sensor). A TMR sensor (tunnel type reluctance sensor) is an element whose resistance value changes depending on magnetism, and by assembling 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 the measurement data is transmitted to the outside via 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 that controls the entire sensor unit 2. The transmitted data is subjected to a determination algorithm by a cloud computer 9 which is an example of the information processing device of this system, and the state of the measurement object is determined.

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 particular distinction between left and right, and the name depends on the left and right on the drawing.
The left magnet unit 3L and the right magnet unit 3R have basically symmetrical structures, and are composed of main magnets 31L and 31R and magnetic field adjusting members 32L and 32R, respectively.
The polarities of the left and right main magnets 31L and 31R are opposite, and the lower surface of the main magnets 31L and 31R, which are facing surfaces of the object to be measured, has an north pole on one side and an south pole on the other side. As the magnetic field adjusting members 32L and 32R, those in which magnets are combined in a Halbach array are adopted.

The sensor unit 2 and the left and right magnet units 3L and 3R are connected and held by the support mechanism 4.
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 relatively sliding the sensor unit 2 and the left and right magnet units 3L and 3R at different relative positions. Enables magnetic measurement of.

FIG. 2 shows an overall external view of the non-destructive inspection device 1 of the present embodiment.
As shown in FIG. 2, the sensor unit 2 is arranged 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 3L and 3R are arranged at both ends in the Y direction at the center of the support mechanism 4. Further, the support mechanism 4 is provided with a grip 41 so that the entire non-destructive inspection device 1 can be stably held when the entire non-destructive inspection device 1 is carried or the object to be measured is touched.

3A and 3B show a schematic diagram comparing the intensities of the magnetic field due to the residual magnetic flux and the magnetic field generated by the magnetic circuit.
FIG. 3A imitates the state after magnetism in the conventional two-step procedure in which magnetization and measurement are performed separately. The object to be measured 8 is assumed to be a reinforced steel rod or a PC steel material which is a magnetic material, and a state in which a gap of about 1 cm is broken in the central portion is assumed (the surrounding non-magnetic material (concrete) is not shown). .same as below).
The object to be measured 8 is in a weak bar magnet state that is magnetized by magnetism. In FIGS. 3A and 3B, the left end portion is magnetized to the N pole and the right end portion is magnetized to the S pole, and a left-pointing magnetic loop-shaped leakage magnetic field is generated from the N extreme portion to the S extreme portion at the gap portion of the fractured portion. However, in the conventional method of performing measurement separately from magnetism 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 that is not a magnet material, only very weak magnetism is emitted and generated. The magnetic flux density of the leaked magnetic field is also small.

FIG. 3B imitates a state in which a magnetic circuit according to the measurement principle of the present invention is formed.
Similarly, the object to be measured 8 is assumed to be a reinforced steel rod or a PC steel material, and a state in which a break of about 1 cm is generated in the central portion is assumed. The object 8 to be measured is in a state in which a magnetic circuit is formed inside the object 8 to be measured by the magnetism of the magnet units 3L and 3R arranged above the left and right ends. The magnetism emitted from the north pole of the right magnet unit 3R gathers at the measurement object 8 which is a magnetic material, passes through the inside thereof, and then flows to the south pole of the left magnet unit 3L. Similar to FIG. 3A, a leftward magnetic loop-shaped leakage magnetic field is generated from the N extreme portion to the S extreme portion at the gap portion of the fractured portion in the middle. However, since the amount of magnetic flux flowing in the object 8 to be measured by the magnetic circuit is larger than the amount of magnetic flux due to the residual magnetic flux, the magnetic flux density of the breaking gap portion is also large, and as a result, the magnetic loop-shaped leakage magnetic field in which the breaking gap portion is generated occurs. Will also be strong.

For example, as the object to be measured 8, two deformed steel bars having a length of 1 m and a diameter of 16 mm are opposed to each other in the longitudinal direction with a gap of about 1 mm assuming a fractured portion, and a magnet unit 3L assuming a cover 300 mm position. Place the 3R. As the magnet units 3L and 3R, a 52 mm × 52 mm × 25 mm neodymium magnet in which 52 mm × 52 mm × 25 mm low carbon steel is contact-integrated as a yoke material is applied to the magnet units 3L and 3R. A magnetic circuit is formed by arranging the deformed steel rods at positions 25 cm to the left and right in the longitudinal direction (Y direction) 300 mm above the broken portion. In this case, a magnetic flux density of about 16 mT is generated in the central portion of the cross section of the gap portion of the fractured portion 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 to obtain the state as shown in FIG. However, the value is only about 2 mT of magnetic flux density.

The method of forming the magnetic circuit in this way can generate a large leakage flux at the fractured portion as compared with the method using the residual magnetic flux.
Therefore, in the present invention, the non-destructive inspection of the deep-covered measurement object 8 is enabled by using the method of forming a magnetic circuit on the measurement object 8. For example, in a device using a conventional leakage flux method in which magnetism and measurement are performed in two steps, the leakage flux is weak, so that the cover depth at which the measurement object 8 can be determined to break is limited to about 200 mm. On the other hand, in the method of forming the magnetic circuit of the present invention, since the leakage flux is strong, it is possible to detect breakage even in a fog exceeding 200 mm.
It is also known that PC steel materials, which generally require higher tension, have smaller residual magnetic properties than crude iron materials such as reinforced steel rods, and PC steel materials that are often placed in deep fracture positions. For the fracture determination, a method of performing the fracture determination while forming the magnetic circuit of the present invention is preferable.

FIG. 4 shows a schematic diagram of the measurement state of the non-destructive inspection device 1 of the present embodiment.
FIG. 4 is a schematic view in which the sensor unit 2 is arranged in the center and the magnet units 3L and 3R are arranged on the left and right, and they are installed adjacent to the measurement object 8 to form a magnetic circuit. .. That is, the magnet unit 3L, the magnetic sensor 21, and the magnet unit 3R are arranged in this order, and the magnet unit 3L, with respect to the measurement object 8 adjacent to the same arrangement and extending in the same direction (Y direction) as the same arrangement. A magnetic circuit is formed by applying magnetic fields of opposite polarities from 3R, and the magnetic sensor 21 detects the magnetic field from the object 8 to be measured in this state. The direction extending in the Y direction of the object to be measured is not limited to the longitudinal direction of the object, and faces the left and right magnet units 3L and 3R even when the width direction of the strip or the like is the Y direction. If it is long enough, it can be measured.
In the example shown in FIG. 4, the main reinforcing bar (PC steel material) is arranged below the sensor unit 2, the magnet units 3L, and 3R as the rod-shaped magnetic material which is the measurement object 8, and one magnet unit (3R) is generated. A magnetic circuit is formed in which magnetism flows into the other magnet unit (3L) even though it passes through the main reinforcing bar.

If the main reinforcing bar of the object to be measured 8 has a fractured portion below the sensor unit 2, end faces of S pole and N pole are generated at the fractured portion, and a loop-shaped magnetic field is generated around the fractured portion.
The magnetic sensor 21 of the sensor unit 2 detects the disturbance of the magnetic loop that occurs at the breakage portion of the main reinforcing bar in the vertical direction (Z direction) for a 1-axis sensor, and in the vertical, horizontal, and front-back directions (X, Y, Z directions) for a 3-axis sensor. ) Detects the magnetic field component. Although not shown, when the main reinforcing bar is not broken, the magnetic loop is not disturbed at the broken portion, so that the magnetic sensor 21 does not detect the disturbance. When a 3-axis sensor is applied as the magnetic sensor 21, a 3-axis sensor capable of detecting magnetic field components in the 3-axis directions orthogonal to each other is preferable, but three 1-axis sensors in which sensor axes are arranged in the same 3-axis direction are preferable. It may be composed of a composite of sensors.
In FIG. 4, the crossed reinforcing bars (stirlap) 7 are arranged in parallel with the main reinforcing bar (8), but since they are arranged in parallel with the magnetic circuit, a large magnetic field turbulence that hinders the measurement occurs. There is no.

5 and 6 show a schematic diagram for explaining the influence of the magnetic magnetic field on the magnetic sensor 21 for explaining the measurement principle of the present invention.
FIG. 5 shows the configuration of a comparative example, in which ordinary main magnets 31L and 31R are arranged on the left and right sides of the magnetic sensor 21. The left main magnet 31L has an S pole on the bottom surface side and an N pole on the top surface side, and magnetic flux is generated inside the magnet from the bottom surface side toward the top surface side. On the outside of the magnet, the magnetism emitted from the upper surface of the N pole returns to the S pole on the bottom surface in a loop. An upward magnetic field is generated on the bottom surface of the magnet. On the contrary, the right main magnet 31R has an N pole on the bottom surface side and an S pole on the top surface side, and magnetic flux is generated inside the magnet from the top surface side toward the bottom surface side. On the outside of the magnet, the magnetism emitted from the bottom surface of the north pole returns to the south pole on the top surface in a loop. A downward magnetic field is generated on the bottom surface of the magnet.

In the case of the comparative example shown in FIG. 5, the external magnetic fields generated around the left and right main magnets 31L and 31R are exposed to the magnetic sensor 21 as well as a strong downward magnetic field at a position close to the left main magnet 31L, and the right main magnet. At a position close to the magnet 31R, it is exposed to a strong magnetic field in the upward direction. In the non-destructive inspection device 1 of the present embodiment, it is necessary to capture a minute magnetic field change generated at the fractured portion of the object to be measured, so that it is not preferable that the magnetic sensor 21 is exposed to the direct magnetic field of the magnet in this way. Therefore, it is configured as shown in FIG.

FIG. 6 shows a schematic diagram for explaining the magnetic field reduction effect on the sensor region in the non-destructive inspection device 1 of the present embodiment. Similar to the comparative example of FIG. 5, normal main magnets 31L and 31R are arranged on the left and right sides of the magnetic sensor 21, and magnetic field adjusting members 32L and 32R are arranged between the left and right main magnets 31L and 31R and the magnetic sensor 21. Has been 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 on the bottom surface in a loop, but on the side where the magnetic field adjusting member 32L is arranged, the magnetic field adjusting member 32L becomes a wall. It prevents the magnetic sensor 21 from being exposed to strong magnetism. Similarly, on the outside of the right main magnet 31R, the magnetism emitted from the bottom surface of the N pole returns to the S pole on the upper surface in a loop, but on the side where the magnetic field adjusting member 32R is arranged, the magnetic field adjusting member 32R is on the wall. This prevents the magnetic sensor 21 from being exposed to strong magnetism.

In this way, the effect of the magnetic field adjusting members 32L and 32R eliminates the exposure of the magnetic sensor 21 to the direct magnetic field of the magnet, and the magnetic sensor 21 accurately detects minute changes in the magnetic field that occur at the fractured part of the object to be measured. It becomes possible to catch.

7A and 7B show a schematic diagram for explaining the effect of the Halbach array magnet.
As is well known, usually magnets have north and south poles facing each other, and the amount of magnetic flux generated on both pole surfaces of the magnet is the same except for the direction of magnetism. FIG. 7A shows a comparative example, in which magnets are arranged side by side while simply alternating the upper and lower polarities, and the strength of the magnetic field generated on the upper surface side and the lower surface side is the same.
FIG. 7B is a schematic view when magnets are arranged in a Halbach array. As shown in FIG. 7B, five magnets are arranged side by side while rotating the magnetization direction from left to top and bottom, left and right, bottom and top, right and left, and top and bottom by 90 degrees. As a result, a magnetic circuit is formed inside the magnet on the lower surface side of the Halbach array magnet, so that a small amount of magnetic force is generated outside the magnet. On the other hand, since the upper surface side of the Halbach array magnets is composed of large portions of S pole and N pole, a strong magnetic field loop is generated outside the magnet. When the magnets are arranged in a Halbach array in this way, the magnetic field is concentrated on one side and a large magnetic force can be extracted. Generally, the effective utilization of the Halbach array magnet is to utilize the magnetic force on the large side, but in the present embodiment, the surface on the small magnetic field side is directed toward the sensor side to utilize it as a magnetic shielding effect.

8A and 8B show an example of an effective combination arrangement of the main magnet and the Halbach magnet.
The magnet units 3L and 3R used in this embodiment are paired left and right and have a symmetrical configuration. The magnet units 3L and 3R are roughly divided into main magnets 31L and 31R, Halbach magnets (32L and 32R), yoke 33 and spacer 34. The main magnets 31L and 31R are for forming a magnetic circuit on the object to be measured, and therefore, they are realized by using four neodymium magnets having a thickness of about 50 mm square and a thickness of 25 mm, for example. The Halbach magnets (32L, 32R) are configured by combining three neodymium magnets, and are arranged so that the side surface of the strong magnetic field faces the main magnet side and the side surface of the weak magnetic field faces the outside facing the magnetic sensor 21. Specifically, in the case of the left magnet unit 3L (FIG. 8A), the main magnet 31L is arranged so that the north pole side is the bottom surface. The middle magnet of the Halbach magnet (32L) is arranged so that the north pole faces the main magnet side, and the upper and lower magnets of the Halbach magnet (32L) face the north magnet side of the Halbach magnet (32L). Magnet. On the other hand, in the case of the right magnet unit 3R (FIG. 8A), the north pole and the south pole are interchanged.
By arranging the Halbach magnets (32L, 32R) in this way, the magnetic fields of the main magnets 31L and 31R are suppressed by the magnetic fields of the Halbach magnets (32L, 32R), and the magnetic force toward the magnetic sensor 21 is reduced. That is, the magnetic field toward the magnetic sensor 21 is reduced while the magnetic field applied to the measurement object 8 is strengthened. Therefore, in the non-destructive inspection device 1, the magnetic field toward the magnetic sensor 21 is reduced with respect to the magnetic field applied to the measurement object 8. Therefore, the magnetic field component from the object to be measured 8 can be accurately detected by the magnetic sensor 21 without being buried in the magnetic field from the magnet units 3L and 3R toward the magnetic sensor 21.

The yoke 33 is provided for the effect of increasing the downward magnetic force of the main magnets 31L and 31R and for attracting a plurality of magnets and stably fixing each of them. Further, since the spacer 34 cannot be arranged adjacent to each other because the repulsive force of each magnet is too strong, the spacer 34 is used as an interval holding member for arranging the magnets at a certain distance. The magnet units 3L and 3R have the same thickness dimensions of the magnetic field adjusting members 32L and 32R in the Z direction and the main magnets 31L and 31R, and are sufficiently large between the main magnets 31L and 31R and the magnetic sensor 21. While arranging the magnetic field adjusting members 32L and 32R of the above, the space is effectively configured.
In order to form a magnetic circuit as strong as possible, it is preferable to use neodymium magnets as the main magnets 31L and 31R, and the Halbach magnets (32L and 32R) for adjusting the magnetic field of the strong main magnets are also neodymium magnets. Is preferable, but the same effect can be obtained with an inexpensive ferrite magnet.

FIG. 9 shows another configuration example of the non-destructive inspection device.
In the configuration example shown in FIG. 2, the magnetic sensor 21 of the sensor unit 2 is arranged in a one-dimensional arrangement in the Y direction and has a structure provided with a slide mechanism for moving the magnetic sensor 21 in the width direction (X direction). In the configuration example shown in FIG. 9, the slide mechanism is abolished, and the magnetic sensor 21 is two-dimensionally arranged on the XY surface in the sensor unit 2. By arranging the magnetic sensor 21 in two dimensions, it is not necessary to perform multiple measurements while appropriately changing the sensor position in the width direction (X direction) using the slide mechanism, and the magnetism of the object 8 to be measured can be measured once. Surface data showing a two-dimensional magnetic field distribution on the measurement surface (XY surface) facing the sensor 21 can be obtained.

In the non-destructive inspection device 1 shown in FIG. 2 or 9, one magnetic field application unit (3L) and the other magnetic field application unit (3R) can be rearranged with respect to the magnetic sensor 21, and by the same replacement. It is preferable to carry out a configuration in which the polar direction of the magnetic circuit formed on the object to be measured can be reversed. As a result, the polar directions of the magnetic circuits are opposite to each other and two surface data can be acquired without changing the relative arrangement of the measurement object and the magnetic sensor 21. When the non-destructive inspection device 1 is inverted as a whole, the sensor unit 2 is also inverted, so that the relative arrangement between the measurement object and the magnetic sensor 21 changes, and the sensor characteristics of each element of the magnetic sensor 21 vary. This is because the amount of change is superimposed on the surface data.
The reversible structure may simply be such that the two magnet units 3L and 3R are once removed from the support mechanism 4, replaced, and reattached to the support mechanism 4. Further, two magnet units 3L, such as a mechanism in which subframes supporting the two magnet units 3L and 3R are independently provided and the subframes are rotatably connected to the main frame on which the sensor unit 2 and the like are supported. A mechanism that can reverse the 3R without removing it from the support mechanism 4 may be configured.
Although FIG. 9 shows an example in which the sensors are arranged in a square grid pattern, the two-dimensional arrangement method of the sensors may be a checkered pattern arrangement or the like, and is not limited to the square grid arrangement.

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

FIG. 11 shows the basic inspection flow of the processing of the non-destructive inspection apparatus and the non-destructive inspection method of the present embodiment. This is the case where the non-destructive inspection device 1 shown in FIG. 2 is used.
(Step S1) The non-destructive inspection device 1 is installed so that the magnetic sensor 21 faces the surface of the measurement object 8 and is close to the surface, and a magnetic field is applied from the magnet units 3L and 3R to the magnetic circuit on the measurement object 8. To form.
(Step S2) The magnetic flux from the measurement object 8 is detected by the magnetic sensor 21 in the state of forming the magnetic circuit in step S1.
(Step S3) The sensor unit 2 is shifted in the width direction (X direction) without changing the position of the non-destructive inspection device 1.
(Step S4) It is determined whether or not the measurement at all the shift positions is completed, and if not, the process returns to step S2. If it is completed, the process proceeds to step S4.
(Step S5) The magnetic field distribution of the entire measurement surface is created from the data collected at all shift positions. The data at this time is 1-axis surface data for a 1-axis sensor and 3-axis direction surface data for a 3-axis sensor.
(Step S6) The created surface data is analyzed for magnetic field turbulence that is considered to be caused by breakage or corrosion of the object to be measured, and if there is magnetic field turbulence, it is estimated to be an abnormal part such as breakage or corrosion. This completes a series of measurements.
When the non-destructive inspection device 1 shown in FIG. 9 is used, the surface data is acquired at once without the circulation processing in steps S2, S3, and S4.

Based on the created surface data, the abnormality determination is performed by the processing of the cloud computer 9.
When the object to be measured is normal and continuous, no large local magnetic field change occurs. On the contrary, when the object to be measured is broken or corroded and its continuity is impaired, a local sudden change in the magnetic field occurs at 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 of 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, after, and left and right is taken, and the slope is calculated by dividing this by the magnetic field strength values of the coordinates of interest. , The presence or absence of an abnormality is determined by whether or not the absolute value of the slope exceeds a certain value. That is,
Forward tilt = | (value of attention coordinate-value of front coordinate) / value of attention coordinate) |
Backward tilt = | (value of attention coordinate-value of back coordinate) / value of attention coordinate) |
Left tilt = | (value of attention coordinate-value of left coordinate) / value of attention coordinate) |
Rightward tilt = | (value of attention coordinate-value of right coordinate) / value of attention coordinate) |
Therefore, if any one of these four values exceeds a predetermined threshold value (for example, 0.3), it is determined that there is an abnormality in the vicinity of the coordinate of interest. For the 1-axis sensor, it is preferable to perform the judgment only for the magnetic field strength value in the 1-axis direction, and for the 3-axis sensor, it is preferable to perform the judgment for all the magnetic field strength values in the 3-axis direction. At this time, it is preferable to set a predetermined threshold value according to the detection pitch and the axial direction of the magnetic field component.
The information processing device that determines the abnormality of the measurement object based on the surface data is not limited to the cloud computer 9, but is a computer that is connected one-to-one to the non-destructive inspection device or is integrated with the non-destructive inspection device. It doesn't matter what the hardware configuration is, such as the computer installed in the computer. When processing is performed by one station of the cloud computer 9, it is advantageous in terms of information accumulation, uniform processing, use, and the like.

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

Notwithstanding the above embodiment, each of the magnetic field application units needs to reduce the magnetic field toward the magnetic sensor with respect to the magnetic field applied to the object to be measured. Therefore, as a magnetic field adjusting member, a low value represented by SS400 is required. The method of arranging a magnetic shield made of carbon steel and the method of arranging a small magnet that repels magnetism also have a certain effect. However, the magnetic shield method has an adverse effect that the shield absorbs even the components of the magnetic circuit, and the method of arranging the repulsive magnets makes it difficult to set the strength of the repulsive magnets and optimize the arrangement. Therefore, the magnetic field of the above embodiment A method of arranging a Halbach magnet as an adjusting member is preferable.
Further, in each of the magnetic field application units, only the Halbach magnet may be arranged in the magnetic field application unit because the magnetic field toward the magnetic sensor may be reduced with respect to the magnetic field applied to the object to be measured. In this case as well, if the weak magnetic field side surface of FIG. 7B of the Halbach magnet is opposed to 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 object to be measured. 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.

The present invention can be used for non-destructive inspection devices such as reinforcing bars buried in concrete, non-destructive inspection systems, and non-destructive inspection methods.

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

Claims (13)

A non-destructive inspection device that uses a magnetic material contained in a non-magnetic material as a measurement object.
One of the magnetic field application units, the magnetic sensor, and the other magnetic field application unit are arranged in this order, and the one magnetic field application unit and the said magnetic field application unit are applied to a measurement object adjacent to the same arrangement and extending in the same direction as the same arrangement. It has a configuration in which the magnetic sensor detects the magnetic field from the measurement target in a state where magnetic circuits 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 non-destructive inspection device in which the magnetic field directed toward the magnetic sensor is reduced with respect to the magnetic field applied to the measurement object. Each of the magnetic field application units has a main magnet for generating a magnetic field 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 can be obtained. The non-destructive inspection device according to claim 1, wherein the magnetic field adjusting member having a magnetic field adjusting member is arranged between the main magnet and the magnetic sensor. The magnetic field adjusting member is a Halbach array magnet in which three or more magnets having different magnetic directions are combined, and the Halbach array magnet has a strong magnetic field side surface facing the main magnet side due to the effect of the Halbach array. The non-destructive inspection device according to claim 2, wherein the side surface of the weak magnetic field is arranged so as to face the magnetic sensor side. A claim that the arrangement of the one magnetic field application unit and the other magnetic field application unit can be exchanged with respect to the magnetic sensor, and the polar orientation of the magnetic circuit formed on the measurement object can be reversed by the exchange. The non-destructive inspection apparatus according to any one of items 1 to 3. The non-destructive 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 arranged on a straight line. The magnetic sensor and the one magnetic field application unit in the width direction parallel to the surface of the arrangement adjacent to the measurement object and orthogonal to the virtual line connecting the one magnetic field application unit and the other magnetic field application unit. The non-destructive inspection device according to any one of claims 1 to 5, further comprising a slide mechanism capable of relatively sliding the other magnetic field application unit. The non-destructive inspection apparatus according to claim 2 or 3, wherein the magnetic field adjusting member and the main magnet having the same thickness dimension in the direction perpendicular to the plane adjacent to the object to be measured in the array. The non-destructive 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 arrangement including a line-shaped and staggered arrangement. Claims 1 to claim that the magnetic sensor is composed of a 3-axis sensor capable of detecting magnetic field components in the 3-axis directions orthogonal to each other or three 1-axis sensors in which sensor axes are arranged in the same 3-axis direction. The non-destructive inspection apparatus according to any one of 8. The non-destructive inspection device according to any one of claims 1 to 9, wherein the magnetic sensor is a tunnel type magnetoresistive sensor (TMR sensor). The non-destructive inspection device according to any one of claims 1 to 10 and an information processing device are provided.
The information processing device is a non-destructive inspection system that determines an abnormality of the measurement object based on measurement information received from the non-destructive inspection device. The non-destructive inspection device outputs surface data indicating a two-dimensional magnetic field distribution on the measurement surface of the measurement object facing the magnetic sensor to the information processing device.
The non-destructive inspection system according to claim 11, wherein the information processing device determines an abnormality of the measurement object based on the surface data. Using the non-destructive inspection device according to any one of claims 1 to 10, the measurement object is made to face the magnetic sensor, and the measurement surface of the measurement object faces the magnetic sensor. Obtaining surface data showing the dimensional magnetic field distribution,
A non-destructive inspection method for determining an abnormality of the measurement object based on the surface data.

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