JP7416356B2 - Non-destructive testing method and testing equipment - Google Patents

Description

The present invention relates to a non-destructive inspection method and an inspection device for inspecting whether or not steel materials buried in a concrete body are damaged from the outside without destroying the concrete body.

BACKGROUND ART Conventionally, non-destructive testing methods have been known for testing the presence or absence of fractures in steel provided within a concrete body. For example, the nondestructive testing method described in Japanese Patent No. 3734822 (Patent Document 1) involves moving a permanent magnet along the longitudinal direction of the reinforcing bars to be inspected buried in the concrete body. The steel material is magnetized, and the magnetic flux density leaking from the surface of the concrete body is measured by two magnetic sensors placed a certain distance apart in the longitudinal direction of the steel material. Furthermore, a method is used in which the difference between the two obtained measured values (differential approximation value: rate of change in magnetic flux density) is calculated, and where this difference exceeds a certain threshold, it is determined that there is a suspicion of rupture. However, this judgment method requires a considerable amount of practical experience in determining the above threshold value, and if the baseline (the straight line that serves as the reference for changes in the magnetic flux density waveform) is significantly tilted due to the magnetization conditions, a considerable amount of work will be required. There were problems such as it was sometimes difficult for even those with practical experience to make judgments.

To solve this problem, we compared the state of the rate of change of magnetic flux density with data obtained by mock-up measurements using a reinforced concrete structure simulated in advance (the fracture position of the reinforcing bars is known). In order to ensure accuracy, it is necessary to collect a large amount of data over a huge amount of time, which makes the inspection process difficult. There is a problem in terms of simplicity and speed.

In addition, since the presence or absence of a break is determined by comparing the pre-learning data with the data obtained through measurement, there is a problem that, for example, if a case that does not exist in the learning database occurs, an appropriate judgment cannot be made. There was also.

Patent No. 3734822

Therefore, the present invention has been made with the object of proposing a non-destructive testing method and a non-destructive testing device that quantitatively determine the presence or absence of damage to steel materials within a concrete body without destroying the concrete body.

The present invention employs the following configuration as a specific means for solving this problem.

"First invention of the present application"
In the non-destructive testing method of the first invention of the present application, the steel material to be tested is magnetized from the outside of the concrete body in which the steel material to be tested is buried using a magnet, and then the magnetic flux density of the concrete body is measured by a magnetic sensor. In the non-destructive testing method for detecting the presence or absence of damaged parts of the steel material to be inspected, the magnetized surface of the magnet is placed close to the surface of the concrete body and then moved as appropriate or without being moved. A magnetization step of magnetizing the steel material to be inspected along its longitudinal direction and then removing the magnet, and placing the magnetic sensor close to the surface of the concrete body and then moving or moving it as appropriate. a magnetic flux density measurement step of measuring the magnetic flux density of the steel material to be inspected, a calculation step of differentiating the magnetic flux density by two orders or more in the longitudinal direction of the steel material to be inspected to obtain a magnetic flux density differential waveform; a determination step of determining the presence or absence of damage in the steel material to be inspected based on the obtained magnetic flux density differential waveform , and the determination step includes determining whether the magnetic flux density differential waveform is a waveform with an even number order differential of the second order or higher. When this is the case, the presence or absence of damage in the steel material to be inspected is determined based on whether the waveform changing portion is a bipolar shape with approximately point symmetry, based on the "approximately point symmetrical bipolar shape determination method" described later. It is said that
The "approximately point-symmetrical bipolar determination method" is based on the ratio of the absolute value of the negative peak height "Pn" and the positive peak height "Ps" in the waveform change part of the magnetic flux density differential waveform. When |Pn|/|Ps|'' is in the range of 0.5 to 2, it is determined that the waveform changing portion is a bipolar waveform with substantially point symmetry.

Here, the above-mentioned steel materials to be inspected are not limited to round bars with a circular cross-sectional shape and deformed steel bars with protrusions on the surface, which are often used in general reinforced concrete structures, but also steel bars with a rectangular cross-sectional shape and other steel bars. It may be a polygonal steel bar or H-shaped steel. In addition, it may be a hollow steel pipe used for water flow or ventilation, and it may also be made of prestressed steel materials such as prestressed steel rods, prestressed steel wires, or prestressed steel stranded wires used in prestressed concrete construction methods, or these may be used inside. It may be a sheath pipe used through the pipe or a PC steel material inside the sheath pipe.

In addition, damage to steel refers to not only the state where the steel is completely broken, but also, for example, in the case of steel made of a bundle of many steel wires such as PC steel wire or PC stranded wire, damage to the steel material refers to the state where the steel material is completely broken. This also includes cases where a part of the pipe is broken.

When magnetizing the steel to be inspected in the above magnetization process, in order to place the magnetized surface of the magnet close to the surface of the concrete body, temporarily place the magnetized surface of the magnet at a predetermined position near the surface of the concrete body. The magnetized surface of the magnet does not necessarily need to be brought into contact with the surface of the concrete body, nor does it need to be stationary. Furthermore, if the magnet is small, the steel to be inspected may be magnetized by moving the magnetized surface of the magnet along the longitudinal direction of the steel to be inspected; if the magnet is large, the magnet By arranging the magnetization surface at one location along the longitudinal direction of the steel material to be inspected without moving the magnetization surface thereof, the steel material to be inspected may be magnetized over a wide range.

Here, the magnetized surface of a magnet refers to the surface of the magnet that is closest to the surface of the concrete body when magnetizing steel materials, and its shape is not limited to a single plane. or an electromagnet.

In addition, in the magnetic flux density measurement process, in order to place the magnetic sensor close to the surface of the concrete body, as in the case of the above magnet, it is necessary to temporarily bring the magnetic sensor close to a predetermined position near the surface of the concrete body. Often, there is no need for it to be in direct contact with the surface of the concrete body, and there is no need for it to be stationary.

However, in order to determine the magnetic flux density along the longitudinal direction of the steel material to be inspected, it is necessary to measure the magnetic flux density not only in the inspection range of the damaged part of the steel material to be inspected, but also in the surrounding area as necessary. To do this, it is sufficient to measure the magnetic flux density while moving one or more magnetic sensors as appropriate. For example, while moving the magnetic sensor near the surface of the concrete body along the longitudinal direction of the steel to be inspected. Magnetic flux density can be measured. Alternatively, the magnetic flux density of the steel to be inspected can be measured by moving it back and forth in a direction perpendicular to the longitudinal direction of the concrete body and gradually shifting it in the longitudinal direction of the steel to be inspected. The magnetic flux density along the direction can be calculated.

"Second invention of the present application"
In the non-destructive testing method of the second invention of the present application, the steel material to be tested is magnetized from the outside of the concrete body in which the steel material to be tested is buried using a magnet, and then the magnetic flux density of the concrete body is measured by a magnetic sensor. In the non-destructive testing method for detecting the presence or absence of damaged parts of the steel material to be inspected, the magnetized surface of the magnet is placed close to the surface of the concrete body and then moved as appropriate or without being moved. A magnetization step of magnetizing the steel material to be inspected along its longitudinal direction and then removing the magnet, and placing the magnetic sensor close to the surface of the concrete body and then moving or moving it as appropriate. a magnetic flux density measurement step of measuring the magnetic flux density of the steel material to be inspected, a calculation step of differentiating the magnetic flux density by two orders or more in the longitudinal direction of the steel material to be inspected to obtain a magnetic flux density differential waveform; a determination step of determining the presence or absence of damage in the steel material to be inspected based on the obtained magnetic flux density differential waveform , and the determination step includes determining whether the magnetic flux density differential waveform is a waveform with an odd order differential of the third or higher order. When this is the case, the presence or absence of damage to the steel material to be inspected is determined based on whether the waveform change part is a substantially line-symmetrical single-peaked shape based on the “approximately line-symmetrical unimodal determination method” described later. It is characterized by
The "approximately linearly symmetric single peak determination method" uses the position in the longitudinal direction of the steel material to be inspected that corresponds to the peak value in the waveform change part of the magnetic flux density differential waveform as a reference position, and When two points corresponding to approximately "1/2" of the peak value are approximately the same distance from the reference position, or in the longitudinal direction of the steel material to be inspected corresponding to the peak value at the waveform changing part. The position at is the reference position, and in the area surrounded by the peak value in the waveform change to the position approximately "1/2" of the peak value, the area on the negative side and the area on the positive side of the reference position are When they are substantially the same, it is determined that the waveform changing portion has a single peak shape that is substantially line symmetrical.

"Third invention of the present application"
In the non-destructive testing method according to the third invention of the present application, in the non-destructive testing method according to the first or second invention , at least one of the magnetic sensors is used , and the magnetic sensor is applied to the longitudinal direction of the steel material to be inspected. Obtain the magnetic flux density differential waveform by moving the steel material to be inspected in the longitudinal direction at at least two positions in a direction perpendicular to the direction and along the surface of the concrete body, and based on each of the magnetic flux density differential waveforms, The present invention is characterized by including an estimation step of estimating a damage position of the steel material to be inspected in the longitudinal direction and a damage position of the steel material to be inspected in a direction along the surface of the concrete body.

"Fourth invention of the present application"
In the non-destructive testing method according to the fourth invention of the present application, in the non-destructive testing method according to the first or second invention , at least one of the magnetic sensors is used , and the magnetic sensor is applied to the surface of the concrete body. Obtain the magnetic flux density differential waveform by moving in the longitudinal direction of the steel material to be inspected in at least two positions vertically and at different distances from the surface, and based on the respective magnetic flux density differential waveforms, The present invention is characterized by including an estimation step of estimating the damage position of the steel material to be inspected in a direction perpendicular to the surface of the concrete body.

"Fifth invention of the present application"
In the non-destructive testing device of the fifth invention of the present application, a magnet magnetizes the steel material to be inspected from the outside of the concrete body in which the steel material to be inspected is buried, and then a magnetic sensor measures the magnetic flux density of the concrete body. A non-destructive testing device for detecting the presence or absence of damaged parts in the steel material to be inspected, wherein the magnetized surface is placed close to the surface of the concrete body and then moved as appropriate or without being moved. After the target steel material is magnetized along its longitudinal direction, the magnetized part including the magnet is removed, and the magnetic sensor is placed close to the surface of the concrete body and then moved appropriately, or by moving. a magnetic flux density measurement section that measures the magnetic flux density of the steel material to be inspected without causing the steel material to be inspected; a determination unit that determines the presence or absence of damage in the steel material to be inspected based on the magnetic flux density differential waveform obtained in When the waveform is a waveform, the presence or absence of damage to the steel material to be inspected is determined based on whether the waveform change part is a bipolar shape that is approximately point symmetrical based on the "approximately point symmetrical bipolar shape determination method" described later. It is characterized by
The "approximately point-symmetrical bipolar determination method" is based on the ratio of the absolute value of the negative peak height "Pn" and the positive peak height "Ps" in the waveform change part of the magnetic flux density differential waveform. When "|Pn|/|Ps|" is in the range of "0.5 to 2", it is determined that the waveform changing section is a substantially point-symmetrical bipolar type.

"Sixth invention of the present application"
In the nondestructive testing device of the sixth invention of the present application, a magnet magnetizes the steel material to be inspected from the outside of the concrete body in which the steel material to be inspected is buried, and then a magnetic sensor measures the magnetic flux density of the concrete body. A non-destructive testing device for detecting the presence or absence of damaged parts in the steel material to be inspected, wherein the magnetized surface is placed close to the surface of the concrete body and then moved as appropriate or without being moved. After the target steel material is magnetized along its longitudinal direction, the magnetized part including the magnet is removed, and the magnetic sensor is placed close to the surface of the concrete body and then moved appropriately, or by moving. a magnetic flux density measurement section that measures the magnetic flux density of the steel material to be inspected without causing the steel material to be inspected; a determination unit that determines the presence or absence of damage in the steel material to be inspected based on the magnetic flux density differential waveform obtained in If the waveform is a waveform, the presence or absence of damage to the steel material to be inspected is determined based on whether the waveform change part is a substantially line-symmetrical single-peaked shape based on the “approximately line-symmetrical unimodal determination method” described later. It is characterized by
The "approximately linearly symmetrical unimodal determination method" uses the position in the longitudinal direction of the steel material to be inspected that corresponds to the peak value in the waveform change part of the magnetic flux density differential waveform as a reference position, and When two points corresponding to approximately "1/2" of the peak value are approximately the same distance from the reference position, or in the longitudinal direction of the steel material to be inspected corresponding to the peak value at the waveform changing part. The position at is the reference position, and in the area surrounded by the peak value in the waveform changing part to approximately "1/2" of the peak value, the area on the negative side and the area on the positive side of the reference position are When they are substantially the same, it is determined that the waveform changing portion has a substantially line-symmetric single peak shape.

"Seventh invention of the present application"
In a non-destructive testing device according to a seventh invention of the present application, in the non-destructive testing device according to the fifth or sixth invention , the magnetic sensor is arranged perpendicularly to the longitudinal direction of the steel material to be inspected and of the concrete body. At least two or more magnetic sensors are arranged in a row at a predetermined interval in the direction along the surface, and damage in the longitudinal direction of the steel material to be inspected is determined based on the magnetic flux density differential waveform corresponding to each magnetic sensor. The present invention is characterized in that it includes an estimation unit that estimates the position and the damage position of the steel material to be inspected in the direction along the surface of the concrete body.

"Eighth invention of the present application"
In the non-destructive testing apparatus according to the eighth invention of the present application, in the non-destructive testing apparatus according to the fifth or sixth invention , the magnetic sensor is configured to detect a magnetic field in a direction perpendicular to the surface of the concrete body and from the surface. Magnetic sensors are provided at at least two positions with different distances, and the damage position of the steel material to be inspected in the direction perpendicular to the surface of the concrete body is estimated based on the magnetic flux density differential waveform corresponding to each of the magnetic sensors. It is characterized by having an estimation section.

Each invention of the present application provides the following effects.

(a) First invention of the present application The non-destructive testing method according to the first invention of the present application is such that after magnetizing a steel material to be inspected buried in a concrete body (magnetization process), leakage from the steel material to be inspected is detected. Measure the magnetic flux density (magnetic flux density measurement process), differentiate the magnetic flux density by two orders or more in the longitudinal direction of the steel material to be inspected to obtain a magnetic flux density differential waveform (calculation process), and calculate the magnetic flux density differential obtained in the above calculation process. Since the purpose is to determine the presence or absence of damage in the steel material to be inspected based on the waveform (judgment step), the presence or absence of damage in the steel material to be inspected is quantitatively determined based on the shape of the waveform in the magnetic flux density differential waveform. I'm struggling.

Therefore, for example, as in the past, the state of the rate of change in magnetic flux density (differential value of magnetic flux density) can be compared with data obtained by mock-up measurements, etc., to qualitatively determine the fracture (damage) of reinforcing bars (steel material to be inspected). Compared to those that inspect for the presence or absence of damage, it is possible to judge the presence or absence of damage more accurately and accurately, and there is no need to learn from large amounts of data, making it easier and faster to inspect for the presence or absence of damage. As a synergistic effect, it is possible to reduce the cost of damage inspection of steel materials to be inspected.

In addition, since the process of determining the presence or absence of damage in the steel material being inspected is clear, it is possible to handle cases extremely easily even in cases where there is no learning database, improving the versatility of damage inspection. do.

Furthermore, in the non-destructive testing method according to the first invention, when the magnetic flux density differential waveform is a waveform with an even order differential of the second order or higher, the above-mentioned "substantially point-symmetrical bipolar determination method" is used. Since the presence or absence of damage to the above-mentioned steel material to be inspected is determined based on whether or not the waveform change part is a bipolar shape with approximately point symmetry, the baseline in the magnetic flux density differential waveform (the change in the magnetic flux density differential waveform) is determined. The reference straight line) always coincides with the line of zero magnetic flux density differential value and becomes horizontal, and it can be more clearly determined whether the waveform changing part in the magnetic flux density differential waveform is a bipolar shape that is approximately point symmetrical. The accuracy of determining the presence or absence of damage in the steel material to be inspected is improved accordingly.

(b) Second invention of the present application In the non-destructive testing method according to the second invention of the present application, after magnetizing the steel material to be inspected buried in a concrete body (magnetization process), leakage from the steel material to be inspected is detected. Measure the magnetic flux density (magnetic flux density measurement process), differentiate the magnetic flux density by two orders or more in the longitudinal direction of the steel material to be inspected to obtain a magnetic flux density differential waveform (calculation process), and calculate the magnetic flux density differential obtained in the above calculation process. Since the purpose is to determine the presence or absence of damage in the steel material to be inspected based on the waveform (judgment step), the presence or absence of damage in the steel material to be inspected is quantitatively determined based on the shape of the waveform in the magnetic flux density differential waveform. I'm struggling.

Therefore, for example, as in the past, the state of the rate of change in magnetic flux density (differential value of magnetic flux density) can be compared with data obtained by mock-up measurements, etc., to qualitatively determine the fracture (damage) of reinforcing bars (steel material to be inspected). Compared to those that inspect for the presence or absence of damage, it is possible to judge the presence or absence of damage more accurately and accurately, and there is no need to learn from large amounts of data, making it easier and faster to inspect for the presence or absence of damage. As a synergistic effect, it is possible to reduce the cost of damage inspection of steel materials to be inspected.

In addition, since the process of determining the presence or absence of damage in the steel material being inspected is clear, it is possible to handle cases extremely easily even in cases where there is no learning database, improving the versatility of damage inspection. do.

Furthermore, in the non-destructive testing method according to the second invention, when the magnetic flux density differential waveform is a waveform due to an odd order differential of the third order or higher, the method is based on the above-mentioned "approximately axisymmetric unimodal determination method". Since the presence or absence of damage to the steel material to be inspected is determined based on whether or not the waveform change part is a single peak with approximately line symmetry, the baseline in the magnetic flux density differential waveform is always the same as the magnetic flux density. It becomes horizontal as it coincides with the line of zero differential value, and it is possible to more clearly judge whether or not the waveform changing part in the magnetic flux density differential waveform is a single peak with approximately line symmetry, and the steel material to be inspected is This will improve the accuracy of determining the presence or absence of damage.

(c) Third invention of the present application In the non-destructive testing method according to the third invention of the present application, in addition to the effects described in (a) or (b) above , the following unique effects can be obtained. That is, in the present invention, at least one magnetic sensor is used , and the magnetic sensor is installed at at least two positions in a direction perpendicular to the longitudinal direction of the steel material to be inspected and along the surface of the concrete body, respectively. The magnetic flux density differential waveform is obtained by moving the steel material in the longitudinal direction, and based on the magnetic flux density differential waveform, the damage position in the longitudinal direction of the steel material to be inspected and the inspection object in the direction along the surface of the concrete body are determined. By estimating the damaged position of each steel material, it is possible to accurately detect the damaged part of the steel material to be inspected within the concrete body in two dimensions, and the accuracy and reliability of determining damage to the steel material to be inspected is significantly improved. .

In addition, in this third invention, only one magnetic sensor is used, and it is sequentially applied to the inspection object at a plurality of positions in a direction perpendicular to the longitudinal direction of the steel material to be inspected and along the surface of the concrete body. Alternatively, a plurality of magnetic flux density differential waveforms may be obtained by moving the steel material in the longitudinal direction. Alternatively, for example, a plurality of magnetic sensors may be moved orthogonally to the longitudinal direction of the steel material to be inspected, It is also possible to arrange them at a plurality of positions in the direction along the surface of the concrete body, and to acquire magnetic flux density differential waveforms with each of the magnetic sensors.

(d) Fourth invention of the present application In the non-destructive testing method according to the fourth invention of the present application, in addition to the effects described in (a) or (b) above , the following unique effects can be obtained. That is, in the present invention, at least one of the magnetic sensors is used , and the magnetic sensor is placed in at least two positions perpendicular to the surface of the concrete body and at different distances from the surface of the steel material to be inspected. By moving the concrete object in the longitudinal direction to obtain magnetic flux density differential waveforms and estimating the damage position of the steel material to be inspected in the direction perpendicular to the surface of the concrete body based on the respective magnetic flux density differential waveforms, The buried depth of the damaged portion of the steel material from the surface of the concrete body can be accurately known, and further improvement in the accuracy and reliability of determining damage to the steel material to be inspected can be expected.

In addition, in this fourth invention, only one magnetic sensor is used, and the magnetic sensor is sequentially installed at a plurality of positions perpendicular to the surface of the concrete body and at different distances from the surface. The magnetic flux density differential waveform may be obtained by moving the steel material to be inspected in the longitudinal direction. Alternatively, for example, a plurality of magnetic sensors may be moved in the direction perpendicular to the surface of the concrete body. , and may be arranged at a plurality of positions at different distances from the surface, and the magnetic flux density differential waveforms may be respectively acquired by the respective magnetic sensors.

(e) Fifth invention of the present application In the non-destructive testing device according to the fifth invention of the present application, after magnetizing the steel material to be inspected buried in the concrete body (magnetized part), leakage from the steel material to be inspected is caused. Measure the magnetic flux density (magnetic flux density measurement section), differentiate the magnetic flux density by two orders or more in the longitudinal direction of the steel material to be inspected to obtain a magnetic flux density differential waveform (calculation section), and perform the above inspection based on this magnetic flux density differential waveform. Since the presence or absence of damage to the steel material to be inspected is determined (judgment unit), the presence or absence of damage to the steel material to be inspected can be quantitatively determined based on the shape of the waveform in the magnetic flux density differential waveform.

Therefore, for example, as in the past, the state of the change rate of magnetic flux density (differential value of magnetic flux density) can be compared with data obtained by mock-up measurements, etc., to qualitatively determine the fracture (damage) of reinforcing bars (steel material to be inspected). Compared to those that inspect for the presence or absence of damage, it is possible to judge the presence or absence of damage more accurately and accurately, and there is no need to learn from large amounts of data, making it easier and faster to inspect for the presence or absence of damage. As a synergistic effect, it is possible to reduce the cost of damage inspection of steel materials to be inspected.

In addition, since the process of determining the presence or absence of damage in the steel material being inspected is clear, it is possible to handle cases extremely easily even in cases where there is no learning database, improving the versatility of damage inspection. do.

Furthermore, in the non-destructive testing apparatus according to the fifth invention, when the magnetic flux density differential waveform is a waveform based on an even-numbered differential of the second order or higher, the non-destructive testing device according to the fifth invention uses Since the presence or absence of damage to the steel material to be inspected is determined based on whether or not the waveform changing part is a bipolar shape with approximately point symmetry, the baseline in the magnetic flux density differential waveform is always zero in the magnetic flux density differential value. It is possible to more clearly judge whether or not the above-mentioned waveform changing part in the magnetic flux density differential waveform is a bipolar shape that is approximately point symmetrical, and the presence or absence of damage in the steel material to be inspected can be determined more clearly. Judgment accuracy will be improved.

(f) Sixth invention of the present application In the sixth invention of the present application, after magnetizing the steel material to be inspected buried in the concrete body (magnetized part), the magnetic flux density leaking from the steel material to be inspected is measured ( The magnetic flux density is differentiated by the second order or more in the longitudinal direction of the steel material to be inspected to obtain a magnetic flux density differential waveform (calculation section), and based on this magnetic flux density differential waveform, the presence or absence of damage in the steel material to be inspected is determined. (determination section), it is possible to quantitatively determine the presence or absence of damage in the steel material to be inspected based on the shape of the waveform in the magnetic flux density differential waveform.

Therefore, for example, as in the past, the state of the rate of change in magnetic flux density (differential value of magnetic flux density) can be compared with data obtained by mock-up measurements, etc., to qualitatively determine the fracture (damage) of reinforcing bars (steel material to be inspected). Compared to those that inspect for the presence or absence of damage, it is possible to judge the presence or absence of damage more accurately and accurately, and there is no need to learn from large amounts of data, making it easier and faster to inspect for the presence or absence of damage. As a synergistic effect, it is possible to reduce the cost of damage inspection of steel materials to be inspected.

In addition, since the process of determining the presence or absence of damage in the steel material being inspected is clear, it is possible to handle cases extremely easily even in cases where there is no learning database, improving the versatility of damage inspection. do.

Furthermore, in the non-destructive testing apparatus according to the sixth invention, when the magnetic flux density differential waveform is a waveform of an odd-order differential of the third order or higher, the above-mentioned "approximately line-symmetric single-peak determination method" is used. Since the presence or absence of damage to the steel material to be inspected is determined based on whether or not the waveform change part is a single peak with approximately line symmetry, the baseline in the magnetic flux density differential waveform is always the same as the magnetic flux density. It becomes horizontal as it coincides with the line of zero differential value, and it is possible to more clearly judge whether or not the waveform change part in the magnetic flux density differential waveform is a single peak shape with approximately line symmetry, and the steel material to be inspected is the same. This will improve the accuracy of determining the presence or absence of damage.

(g) Seventh invention of the present application In the seventh invention of the present application, in addition to the effects described in (e) or (f) above, the following unique effects can be obtained. That is, in the present invention, the magnetic sensor includes at least two magnetic sensors arranged in a row at a predetermined interval in a direction perpendicular to the longitudinal direction of the steel material to be inspected and along the surface of the concrete body, Based on the magnetic flux density differential waveform corresponding to each of the magnetic sensors, a damage position in the longitudinal direction of the steel material to be inspected and a damage position of the steel material to be inspected in a direction along the surface of the concrete body are estimated, respectively. Therefore, the damaged portion of the steel material to be inspected within the concrete body can be accurately detected two-dimensionally, and the accuracy and reliability of determining damage to the steel material to be inspected are significantly improved.

(h) Eighth invention of the present application In the eighth invention of the present application, in addition to the effects described in (e) or (f) above, the following unique effects can be obtained. That is, in this invention, the magnetic sensors are provided at at least two positions in a direction perpendicular to the surface of the concrete body and at different distances from the surface, and the magnetic flux corresponding to each magnetic sensor is By estimating the damage position of the steel material to be inspected in the direction perpendicular to the surface of the concrete body based on the density differential waveform, it is possible to accurately know the burial depth of the damaged portion of the steel material to be inspected from the surface of the concrete body. As a result, further improvement in the accuracy and reliability of damage determination of the steel material to be inspected can be expected.

1 is a functional block diagram of a non-destructive testing method and testing device according to a first embodiment of the present invention; FIG. FIG. 3 is a schematic explanatory diagram of leakage magnetism from magnetized reinforcing bars at a site where there is a damaged part. FIG. 3 is a schematic explanatory diagram of leakage magnetism from magnetized reinforcing bars in a region where there is no damaged part. FIG. 3 is a schematic explanatory diagram of a magnetic flux density measurement process in non-destructive testing. It is a magnetic flux density waveform diagram based on the actually measured value of magnetic flux density in the site|part with a damaged part. 6 is a first-order differential waveform diagram based on the first-order differential value of the magnetic flux density in FIG. 5. FIG. 6 is a second-order differential waveform diagram based on the second-order differential value of the magnetic flux density in FIG. 5. FIG. 6 is a third-order differential waveform diagram based on the third-order differential value of the magnetic flux density in FIG. 5. FIG. FIG. 3 is an explanatory diagram of a first determination method for a single peak waveform in a third-order differential waveform diagram. FIG. 7 is an explanatory diagram of a second determination method for a single peak waveform in a third-order differential waveform diagram. Ru. It is a magnetic flux density waveform diagram based on the actually measured value of the magnetic flux density in the site|part without a damaged part. 12 is a first-order differential waveform diagram based on the first-order differential value of the magnetic flux density in FIG. 11. FIG. 12 is a second-order differential waveform diagram based on the second-order differential value of the magnetic flux density in FIG. 11. FIG. FIG. 2 is a second-order differential waveform diagram at an abnormal part other than a damaged part of the steel material to be inspected. FIG. 2 is a functional block diagram of a non-destructive testing method and testing device according to a second embodiment of the present invention. FIG. 3 is an explanatory diagram of the configuration near a magnetic flux density measurement unit in non-destructive testing. It is a magnetic flux density waveform diagram based on the actually measured value of magnetic flux density in the site|part with a damaged part. 18 is a first-order differential waveform diagram based on the first-order differential value of the magnetic flux density in FIG. 17. FIG. 18 is a second-order differential waveform diagram based on the second-order differential value of the magnetic flux density in FIG. 17. FIG. FIG. 3 is a functional block diagram of a non-destructive testing method and testing device according to a third embodiment of the present invention. FIG. 3 is an explanatory diagram of the configuration near a magnetic flux density measurement unit in non-destructive testing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A non-destructive testing method and testing device according to the present invention will be described below based on embodiments.

A: First Embodiment First, the basic idea of the non-destructive testing method and non-destructive testing device according to the present invention will be explained, and then a specific explanation will be provided based on examples.

A-1: Basic idea of the non-destructive testing method and non-destructive testing device according to the present invention A-1-a: Regarding steel materials to be tested Here, the steel materials to be tested to which the non-destructive testing method and non-destructive testing device are applicable Assuming that there is a reinforcing bar 2 buried in the concrete body 1, it is determined whether there is a damaged part (specifically, a "broken part") in the longitudinal direction of the reinforcing bar 2. This allows inspection to be performed based on the magnetic flux density waveform obtained from the outside.

A-1-b: Basic concept of fracture inspection of reinforcing bars 2 (a) Regarding magnetization of reinforcing bars 2 Magnetization of the reinforcing bars 2 buried in the concrete body 1 is performed using a conventionally well-known process (for example, Patent Document 1 (see). That is, after the magnet 3 (see FIG. 1) is placed close to the surface 1a of the concrete body 1, it is magnetized along the longitudinal direction of the reinforcing bar 2 by appropriately moving it or without moving it. By this magnetizing operation, the reinforcing bar 2 is magnetized under the influence of the magnetism of the magnet 3, and a magnetic flux is generated along the longitudinal direction of the reinforcing bar 2 in a direction from the south pole side to the north pole side. After magnetization, the magnet 3 is removed from the concrete body surface 1a.

The magnet 3 is a rectangular parallelepiped permanent magnet made of a rare earth metal such as Nd-based metal, but is not limited to this. For example, it may be an electromagnet instead of a permanent magnet, and the shape is not limited to a rectangular parallelepiped. It may be letter-shaped or U-shaped.

(b) Measurement of residual magnetic flux density using a magnetic sensor Magnetism leaking to the outside from the reinforcing bars 2 can be measured by placing a magnetic sensor 4 close to the surface 1a of the concrete body, as shown in FIGS. 2 and 3. By moving the reinforcing bar 2 in the longitudinal direction, an electric signal corresponding to the size of the reinforcing bar 2 is obtained. The measured value of the magnetic flux density measured by the magnetic sensor 4 is graphically processed in a calculation unit 22 (see FIG. 1), which will be described later, to form a magnetic flux density waveform diagram (see FIGS. 5 and 11).

(B-1) Measurement of magnetic flux density in a portion with a fracture portion FIG. 2 shows the state of residual magnetism in the reinforcing bar 2 with a fracture portion 2A. In this fractured portion 2A, one end 2B side becomes a north pole, the other end 2C opposite thereto becomes a south pole, and the magnetic flux in the reinforcing bar 2 is interrupted at this fractured portion 2A. Then, on the one end 2B side of the reinforcing bar 2, a line of magnetic force 10b is generated from the N pole near the broken part 2A toward the rear side (left side in the figure), and as a result, the above-mentioned broken line 10b is generated on the one end 2B side. A magnetic flux 12 is generated in the direction toward the portion 2A. Further, on the other end 2C side, a portion close to the broken portion 2A becomes an S pole, and a magnetic flux 13 in a direction away from the broken portion 2A is generated on the far 2C side. Furthermore, in the broken portion 2A, lines of magnetic force 10a are generated that go from the north pole on the one end 2B side to the south pole on the other end 2C side.

Furthermore, as shown in FIG. 2, on the one end 2B side, the magnetic flux 16 directed upward in the Z-axis direction (direction perpendicular to the surface of the concrete body 1) is applied to the N-pole portion, while the magnetic flux 16 is directed upward to the S-pole portion. A magnetic flux 14 is generated downward in the Z-axis direction. Further, on the other end 2C side, a magnetic flux 15 directed upward in the Z-axis direction is generated at the N-pole portion, and a magnetic flux 17 directed downward in the Z-axis direction is generated at the S-pole portion.

The magnetic flux density of the reinforcing bar 2 with this broken part 2A was measured, and the Z-axis direction component was shown as a waveform diagram in relation to the measurement position in the longitudinal direction of the reinforcing bar 2, as shown in the magnetic flux density waveform diagram in FIG. It is.

(B-2) Measurement of magnetic flux density in a portion where a magnetized end exists FIG. 3 shows the state of residual magnetic flux in a reinforcing bar 2 where a magnetized end exists, although there is no broken part. In this portion, the magnetic flux 18 in the direction from the south pole side to the north pole side of the reinforcing bar 2 is not interrupted on the way. In this case, a magnetic flux 19 directed upward in the Z-axis direction is produced in the N-pole region, and a magnetic flux 20 directed downward in the Z-axis direction is produced in the S-pole region. The magnetic flux density waveform diagram shown in FIG. 11 is a waveform diagram showing the Z-axis direction component of the magnetic flux density measured in relation to the measurement position in the longitudinal direction of the reinforcing bar 2.

(Ro-3) Consideration of the magnetic flux density waveform diagrams shown in FIGS. 5 and 11. Both the magnetic flux density waveform diagrams shown in FIG. 5 and the magnetic flux density waveform diagram shown in FIG. 11 have waveforms that rise to the right. This is due to the fact that in the magnetization step, the magnet 3 was magnetized by moving from the left side in the figure to the right side in the figure, with the N pole facing the left side in the figure and the S pole facing the right side in the figure. Therefore, for example, if the magnetic poles are magnetized in the opposite direction to that described above, the magnetic flux density waveform diagrams will both have a downward-sloping waveform (not shown). In addition, in the magnetic flux density waveform diagram in Figure 5, the part corresponding to the fracture part changes from the positive side to the negative side as an S-shaped waveform, and in the magnetic flux density waveform diagram in Figure 11, the part corresponding to the magnetized end changes to the positive side. Each is represented as a single peak waveform.

(c) Acquisition of first-order differential waveform diagram of magnetic flux density The magnetic flux density value obtained by measurement was differentiated in the longitudinal direction of the reinforcing bar 2, and the peak of magnetic flux density was highlighted under the horizontal baseline. , are first-order differential waveform diagrams shown by solid lines in FIGS. 6 and 12, respectively. The baseline in this first-order differential waveform diagram can be obtained by first-order differentiating the magnetic flux density waveform diagram, which has a baseline represented by a straight line with a constant slope (for example, "aX+b"), as shown in FIG. , is a horizontal straight line with a constant value of its slope (i.e., "a" above), and is apparently recognized as a straight line with a constant bias value "a" relative to the zero line. . Therefore, in the peak waveform shown in this first-order differential waveform diagram, it is difficult to clearly recognize the characteristics of the peak waveform due to the influence of this bias value. Therefore, in the present invention, the first-order differential waveform diagram is It is not used for detection.

FIG. 6 is a first-order differential waveform diagram when the reinforcing bar 2 has a broken part, and FIG. 12 is a first-order differential waveform diagram when the reinforcing bar 2 has a magnetized end instead of a broken part. 6 and 12, in addition to waveform diagrams shown by solid lines, waveform diagrams shown by broken lines that are line symmetrical with respect to the zero level are shown. The waveform shown by this solid line is the waveform obtained when the magnetic flux density value is differentiated along the longitudinal direction of the reinforcing bar 2 from the low position side to the high position side (from the left side to the right side in the figure), The waveform shown by the broken line is the waveform obtained when the magnetic flux density value is differentiated along the longitudinal direction of the reinforcing bar 2 from the high position side to the low position side (from the right side to the left side in the figure).

(d) Obtaining second-order differential waveform diagrams The first-order differential value of the magnetic flux density is differentiated in the longitudinal direction of the reinforcing bars 2 (second-order differential), and this is shown as a waveform diagram in FIGS. 7 and 13. FIG. 4 is a second-order differential waveform diagram shown respectively. Note that FIG. 7 is a second-order differential waveform diagram when the reinforcing bar 2 has a broken part, and FIG. 13 is a second-order differential waveform diagram when the reinforcing bar 2 has no broken part but has a magnetized end. . The baseline in each of these second-order differential waveform diagrams is a straight line that coincides with the zero line by further differentiating the baseline, which is expressed as a horizontal straight line with a constant value in the first-order differential waveform diagram, and is a straight line that coincides with the zero line. The part corresponding to is highlighted as having the maximum and minimum values.

In addition to the waveform diagrams shown by solid lines, FIGS. 7 and 13 also show waveform diagrams shown by broken lines that are approximately line symmetrical with respect to the zero level. The relationship between the waveform shown by the solid line and the waveform shown by the broken line is related to the differential direction with respect to the longitudinal direction of the reinforcing bar 2 at the time of second-order differentiation, as explained in the section on obtaining the first-order differential waveform diagram, and below. will be explained based on a waveform diagram shown by a solid line.

By the way, even if the peak waveforms have the same maximum value and minimum value, the peak waveform in the second-order differential waveform diagram of FIG. 7 and the peak waveform in the second-order differential waveform diagram of FIG. 13 cannot be clearly distinguished. can. That is, by second-order differentiating the magnetic flux density value obtained by measurement, as shown in FIGS. 7 and 13, the baseline coincides with the zero line, and in the parts corresponding to the fractured part and the magnetized end, An S-shaped waveform across the baseline is acquired.

Here, when comparing the second-order differential waveform diagram of FIG. 7 with the second-order differential waveform diagram of FIG. 13, in the second-order differential waveform diagram of FIG. 7, the negative side peak height "Pn" and the positive side peak height The ratio of absolute values "|Pn|/|Ps|" is "approximately 1" between "Ps" and the maximum value and minimum value are centered at the point where the waveform crosses the zero line. There is a relationship of almost point symmetry. In addition, in this embodiment, if the above ratio "|Pn|/|Ps|" is in the range of "0.5 to 2", it is determined that the reinforcing bar 2 is suspected of breaking, and in this case, , the closer the above ratio is to "1", the higher the possibility that the reinforcing bar 2 will break.

On the other hand, in the second-order differential waveform diagram of FIG. 13, the ratio of the absolute value between the negative side peak height "Pn" and the positive side peak height "Ps" is "|Pn|/| Since Ps|'' exceeds 2, the maximum and minimum values are not in a substantially point-symmetrical relationship. Therefore, it is determined that there is no possibility of the reinforcing bar 2 breaking.

The difference between the peak waveforms of this bipolar type can be clearly recognized, and if the peak waveform portions are approximately point symmetrical, it is a "broken part", and if they are not approximately point symmetrical, it is accurately determined to be a "magnetized end". Therefore, the second-order differential waveform diagram can be used as a quantitative index for determining the presence or absence of a fracture in the reinforcing bar 2.

Note that FIG. 14 shows a second-order differential waveform diagram. This second-order differential waveform diagram is a second-order differential waveform diagram obtained by second-order differentiating the magnetic flux density value measured at the overlapping part where the ends of the reinforcing bars 2 overlap in the longitudinal direction. . This second-order differential waveform diagram is obtained by further differentiating the first-order differential value in the longitudinal direction of the reinforcing bars 2 from the lower position side to the higher position side (from the left side to the right side in the figure). The overall shape corresponds to the second-order differential waveform diagram shown by the broken line in FIG. 7, that is, the second-order differential waveform diagram obtained by differentiating from the high position side to the low position side (from the right side to the left side in the figure) It is shaped like this.

That is, both the second-order differential waveform diagram in FIG. 7 and the second-order differential waveform diagram in FIG. If the above-mentioned overlapping part is a broken part, the second-order differential waveform diagram in FIG. 14 will be the same as the waveform diagram shown by the solid line diagram in FIG. 7. However, this is not the waveform diagram shown by the solid line in FIG. 7, but the waveform diagram shown by the broken line in FIG. , there is a substantially line-symmetrical relationship across the zero line).

Therefore, even if the second-order differential waveform diagram in FIG. 14 is similar to the second-order differential waveform diagram shown by the solid line in the second-order differential waveform diagram in FIG. 7, it can be easily determined that these two are not the same. Therefore, for example, an erroneous determination that a fracture exists at the peak portion of the second-order differential waveform diagram in FIG. 14 can be reliably avoided.

(E) Acquisition of third-order differential waveform diagram The second-order differential value of the above magnetic flux density is further differentiated in the longitudinal direction of the reinforcing bar 2 (third-order differential), and this is shown as a waveform diagram as shown in Fig. 8. It is a third-order differential waveform diagram. This third-order differential waveform diagram has a single-peak peak waveform, similar to the first-order differential waveform diagram shown in FIG. 6, but the direction of the peak waveform is on the positive side, unlike the first-order differential waveform diagram. It has a convex single peak shape. In order to use this third-order differential waveform diagram as a quantitative index for detecting the fractured part of the reinforcing bar 2, it is necessary to determine whether the unimodal peak waveform part is approximately axisymmetric. The following two methods will be explained here as determination methods.

(H-1) First Judgment Method As shown in FIG. ). Then, from the reference position of the two points (a) and (b) corresponding to approximately "1/2" (B(X0)/2) of the peak value (B(X0)) in the third-order differential waveform diagram, respectively. When the spacings ("XO-a", "XO+b") are substantially the same (a≈b), it is determined that the waveform changing portion is a substantially line-symmetric single peak shape.

(E-2) Second Judgment Method As shown in FIG. 10, the second judgment method uses the position in the longitudinal direction of the reinforcing bar 2 corresponding to the peak value in the third-order differential waveform diagram as the reference position (XO). . Then, in the area surrounded by the peak value (B(X0)) in the third-order differential waveform diagram to the position approximately "1/2" (B(X0)/2) of the peak value, the negative value is lower than the reference position. When the area on the side (S1) and the area on the positive side (S2) are approximately the same (S1≈S2), it is determined that the waveform changing portion is approximately axisymmetric and single-peaked.

(f) Relationship between multiple-order differential waveform diagrams As described above, the differential rank and the shape of the peak waveform part in the differential waveform diagram are uniquely determined by the differential rank, whereas in the first-order differential waveform diagram, It is unimodal, bipolar in the second-order differential waveform diagram, unimodal in the third-order differential waveform, bipolar in the fourth-order differential waveform, unimodal in the fifth-order differential waveform, and so on. That is, the shape characteristics (i.e., unimodal peak waveform) and contents of the first-order differential waveform diagram are inherited by the odd-numbered differential waveform diagrams of the third and higher orders, and the shape characteristics ( In other words, the bipolar peak waveform) and the contents are inherited by the even-numbered differential waveform diagrams of the 4th and higher floors (although the swing amplitude of the magnetic flux density on both the positive and negative sides and the waveform width in the longitudinal direction of the reinforcing bar 2 change). .

Therefore, in inspecting the presence or absence of a fracture in the reinforcing bar 2, not only the above-mentioned second-order differential waveform diagram and third-order differential waveform diagram, but also higher-order differential waveform diagrams can be used as appropriate; It is arbitrary which rank of differential waveform diagram is used in the non-destructive testing.

A-2: Embodiment FIG. 1 shows the specific contents of the non-destructive testing device Z as a functional block diagram.
This non-destructive testing device Z is configured to include a device main body Za, which will be described below, and a magnetizing section 25 (constituting a magnetizing step in the non-destructive testing method) including a magnet 3. The device main body Za also includes a magnetic sensor 4 and a distance sensor 8 disposed on the surface 1a of the concrete body 1, and a magnetic flux density measuring section 21 (non-destructive) that measures the magnetic flux density from the magnetized reinforcing bars 2. a first-order differential section 22a that receives a magnetic flux density measurement value from the magnetic flux density measurement section 21 and obtains a first-order differential waveform of the magnetic flux density measurement value; and a second-order differential waveform. an arithmetic unit 22 (constituting the arithmetic process in the non-destructive testing method), which includes a plurality of differentiators, such as a second-order differentiator 22b that calculates a 3rd-order differential waveform diagram, a 3rd-order differentiator 22c that calculates a 3rd-order differential waveform diagram, etc.; A determination unit 23 (constituting the determination step in the non-destructive testing method) receives a differential waveform diagram from an arbitrary differentiation unit of the calculation unit 22 and determines the presence or absence of a fracture in the reinforcing bar 2; A display unit 24 is provided that receives and displays information related to determination.

In addition, in FIG. 1, a functional block diagram of the non-destructive testing device Z is shown in solid lines, and at the same time, functional blocks in the non-destructive testing method are shown in a form corresponding to each component of the non-destructive testing device Z. , indicated by a broken line.

The actual diagnostic work of this non-destructive testing apparatus Z will be explained in detail, although some parts overlap with those already described.

First, the magnet 3 is placed close to or in contact with the surface 1a of the concrete body 1, and then the magnet 3 is attached to the reinforcing bar 2 buried in the concrete body 1 by moving it appropriately or without moving it. Magnetize along the longitudinal direction. After magnetization is completed, the magnet 3 is removed from the surface 1a of the concrete body 1. Due to this magnetization work, magnetic flux is generated in the reinforcing bar 2 due to residual magnetism.

In the magnetic flux density measuring section 21, the magnetic flux density of the reinforcing bar 2 is measured by the magnetic sensor 4, the moving distance of the magnetic sensor 4 is measured by the distance sensor 8, and the detection signals (electrical signal) and the detection signal (electrical signal) of the distance sensor 8 are input to the calculation unit 22 as information regarding magnetic flux density.

In the arithmetic section 22, any one of the differentiating sections 22a to 22n is selected (in this embodiment, the second-order differentiating section 22b is selected), and the selected second-order differentiating section 22b performs the above-mentioned Based on the input information from the magnetic flux density measurement unit 21, a second-order differential value and a second-order differential waveform diagram (see FIG. 7) are obtained. The information shown in this second-order differential waveform diagram is input to the determination section 23, which will be described below.

The determination unit 23 receives the second-order differential waveform diagram from the calculation unit 22 and determines whether there is a fracture in the reinforcing bar 2 or not, and if so, at what position in the longitudinal direction of the reinforcing bar 2. Determine if there is. That is, here, in the second-order differential waveform diagram (see FIG. 7), when the maximum point and the minimum point in the bipolar waveform changing part are approximately point symmetrical, it is assumed that the reinforcing bar 2 has a broken part. On the other hand, when the point is not approximately symmetrical, it is determined that, for example, a magnetized end exists. Also, it is determined at which position in the longitudinal direction of the reinforcing bar 2 this fractured portion exists based on the second-order differential waveform diagram (i.e., based on the value of "position X" on the horizontal axis in FIG. 7). do.

The result of the determination made by the determination section 23 is displayed on the display section 24, and a buzzer or the like is used to call attention to it as necessary. With this, the work of determining the presence or absence of a broken portion is completed.

In the above embodiment, the magnetic flux density measuring section 21 is equipped with the distance sensor 8 together with the magnetic sensor 4. However, for example, in the case where the apparatus main body Za is equipped with a high-precision positioning mechanism in advance, Even if the distance sensor 8 is not provided, by using the positioning mechanism, the magnetic flux density measuring section 21 can measure the magnetic flux density in relation to the position of the reinforcing bar 2 in the longitudinal direction.

B: Second Embodiment The non-destructive testing apparatus Z according to the second embodiment of the present invention obtains a second-order differential waveform diagram based on the magnetic flux density value obtained by measurement, and calculates the second-order differential waveform diagram. Determining the presence or absence of a fracture in the reinforcing bar 2 from the information shown in the figure is the same as in the case of the non-destructive testing device Z according to the first embodiment, but in addition to this, Estimating the position of the fractured portion of No. 2 in the X-axis direction (longitudinal direction of the reinforcing bars 2) and Y-axis direction (direction perpendicular to the longitudinal direction of the reinforcing bars 2 and parallel to the surface of the concrete body 1) of the concrete body 1. It was designed to do so. This will be explained in detail below.

B-1: Configuration of non-destructive testing device Z FIG. 15 shows a functional block diagram of the non-destructive testing device Z. This non-destructive testing apparatus Z is configured to include a main body Za of the apparatus and a magnetizing section 30 (constituting a magnetizing step in a non-destructive testing method), which will be described below. The device main body Za also includes three magnetic sensors 4 to 6 and a distance sensor 8 arranged on the surface 1a of the concrete body 1, and detects the magnetic flux density from the reinforcing bars 2 magnetized by the magnetization section 30. A magnetic flux density measuring section 31 (constituting the magnetic flux density measuring step in the non-destructive testing method) measures the magnetic flux density, and receives a magnetic flux density measurement value from the magnetic flux density measuring section 31 and generates a first-order differential waveform of the magnetic flux density measurement value. A calculation unit 32 including a plurality of differentiation units, such as a first-order differentiation unit 32a for obtaining a second-order differential waveform, a second-order differentiation unit 32b for obtaining a second-order differential waveform, and a third-order differentiation unit 32c for obtaining a third-order differential waveform diagram (computation in a non-destructive testing method). a determination unit 33 (constituting a determination process in the non-destructive testing method) that receives a differential waveform diagram from an arbitrary differentiation unit of the calculation unit 32 and determines the presence or absence of a fracture in the reinforcing bar 2; , an estimation unit 34 that receives information from the calculation unit 32 and estimates the position of the fractured part of the reinforcing bar 2 in two directions, the X-axis direction and the Y-axis direction, of the concrete body 1, and the determination unit 33. The apparatus includes a display section 35 that receives information regarding the determination and information regarding the position of the fracture portion from the estimation section 34 and displays the information.

(a) Magnetized part 30
The magnetization section 30 is configured to include a magnet 3, and magnetizes the reinforcing bar 2. As shown in FIG. 15, the magnet 3 is arranged close to the surface 1a of the concrete body 1. After that, the reinforcing bars 2 buried in the concrete body 1 are magnetized along the longitudinal direction by moving the reinforcing bars 2 as appropriate or without moving them. By this magnetizing operation, magnetic flux is generated in the reinforcing bar 2 due to residual magnetism. After magnetization, the magnet 3 is removed from the concrete body surface 1a.

(b) Magnetic flux density measuring section 31
As shown in FIGS. 15 and 16, the magnetic flux density measurement unit 31 measures the surface 1a of the concrete body 1 in a direction (Y) perpendicular to the longitudinal direction of the reinforcing bars 2 and parallel to the surface 1a of the concrete body 1. Three magnetic sensors 4 to 6 are arranged at predetermined intervals (50 mm in this embodiment) in the axial direction, and a distance sensor 8 is also provided. In this case, among the three magnetic sensors 4 to 6, the magnetic sensor 5 located at the center in the arrangement direction is connected to the reinforcing steel in the direction along the surface 1a of the concrete body 1 (i.e., the Y-axis direction). 2 (in other words, so that the magnetic sensor 5 is located directly above (FIG. 15) or directly below (FIG. 16) the reinforcing bar 2 in the Z-axis direction). ing. The position of the magnetic sensor 5 with respect to the reinforcing bar 2 in the Y-axis direction is confirmed by an appropriate position confirmation means.

Therefore, in FIG. 15, when the position of the central magnetic sensor 5 in the Y-axis direction is set to "0", the magnetic sensor 4 is "50 mm" in the Y-axis direction with respect to the magnetic sensor 5, and 6 will be spaced apart by "-50 mm" in the Y-axis direction. In this embodiment, the position of the broken part 2A of the reinforcing bar 2 in the X-axis direction is measured by the distance sensor 8 (see FIG. 17), and the position in the Y-axis direction is measured by the magnetic sensor 5 as described above. It is known that it is located directly above (FIG. 15) or directly below (FIG. 16) the reinforcing bar 2.

(C) Measurement of magnetic flux density by each of the magnetic sensors 4 to 6 The magnetic sensors 4 to 6 are integrally scanned along the surface 1a of the concrete body 1 in the longitudinal direction of the reinforcing bar 2. , respectively measure the magnetic flux density. The magnetic flux density values measured by each of these magnetic sensors 4 to 6 are graphically processed and displayed as a magnetic flux density differential waveform diagram as shown in FIG. In this case, the respective magnetic flux density differential waveform diagrams corresponding to the magnetic sensors 4 to 6 are both curves sloping downward to the right, and have an S-shaped waveform in the portion corresponding to the fracture portion 2A of the reinforcing bar 2. It has become.

In this embodiment, three magnetic sensors 4 to 6 are arranged in the magnetic flux density measuring section 31 to obtain three magnetic flux density values in one scan, but in other embodiments For example, it is also possible to prepare one magnetic sensor, scan it at three positions in the Y-axis direction, and finally obtain three magnetic flux density values at different scan positions.

(d) Obtaining the first-order differential waveform diagram in the calculation section 32 The first-order differentiation section 32a of the calculation section 32 receives the magnetic flux density values obtained by each of the magnetic sensors 4 to 6 of the magnetic flux density measurement section 31, and receives the By differentiating in the longitudinal direction of the reinforcing bar 2, three first-order differential waveforms are obtained, as shown in the first-order differential waveform diagram of FIG. In each of these first-order differential waveforms, the portion corresponding to the fracture portion is a single peak waveform toward the negative electrode side, and the peak value corresponds to the distance between the reinforcing bar 2 and each of the magnetic sensors 4 to 6. The waveform corresponding to the magnetic sensor 5 located directly above (FIG. 15) or directly below (FIG. 16) the reinforcing bar 2 in the Z-axis direction is the largest.

(E) Acquisition of second-order differential waveform diagram in calculation section 32 In the second-order differentiation section 32b, the first-order differential value for each magnetic sensor 4 to 6 obtained in the first-order differentiation section 32a is further calculated by the reinforcing steel 2. By differentiating in the longitudinal direction of Obtain three second-order differential waveforms.

As shown in the second-order differential waveform diagram of FIG. 19, the peak values of the second-order differential waveforms differ depending on the distance between the reinforcing bar 2 and each of the magnetic sensors 4 to 6. However, each of these second-order differential waveforms is a bipolar shape that changes from the negative side to the positive side in its peak waveform portion. In this embodiment, as will be described later, the presence or absence of a fracture is determined based on whether or not the peak waveform portion of the second-order differential waveform is approximately point symmetrical. The second-order differential waveform corresponding to the magnetic sensor 5 having the maximum peak value is adopted.

(f) Determination of presence or absence of a fracture in the determination section 33 The determination section 33 uses the second-order differential waveform obtained by the second-order differentiation section 32b of the calculation section 32 to determine whether or not there is a fracture in the reinforcing bar 2. Determine whether or not. In that case, among the three second-order differential waveforms obtained by the second-order differential section 32b, the second-order differential waveform corresponding to the magnetic sensor 5 having the maximum peak value and most suitable as an index for determining the fracture portion is selected. adopt. Then, the ratio "|Pn|/|Ps|" of the absolute value of the minimum value "Pn" on the negative side and the maximum value "Ps" on the positive side in the bipolar peak waveform part of this second-order differential waveform is "approximately 1". '', and since the local maximum value and the local minimum value are approximately symmetrical with respect to the point where the waveform crosses the zero line, it is determined that there is a fracture in the reinforcing bar 2.

That is, by using the second-order differential waveform as an index for determining the presence or absence of a fracture in the reinforcing bar 2, the determination of the presence or absence of a fracture can be quantified, thereby making the determination of a fracture more accurate and It can be done quickly.

(G) Estimating the position of the fractured part The estimation unit 34 estimates the position of the fractured part in the concrete body 1 in two axial directions (X-axis direction and Y-axis direction).
First, regarding the two bipolar peaks "Pn" and "Ps" (see Figure 19) of the second derivative, the peak height "Pn (μT/cm 2 )" of the peak "Pn" and the peak height "Pn (μT/cm ² )" of the peak "Ps" are calculated. The peak height Ps (μT/cm ² ), the average peak height “(|Pn|+|Ps|)/2=Pm”, the peak ratio “|Pn|/|Ps|=Pj”, and the peak “ The peak position "Xn (mm)" of "Pn", the peak position "Xs (mm)" of peak "Ps", the peak width "|Xn-Xs|=Xj", and the peak position average "(Xn+Xs)/2"=Xm'' were determined and shown in Table 1.

(T-a) Estimating the position of the fractured part in the X-axis direction First, the position "X ₀ " of the fractured part in the reinforcing bar 2 in the X-axis direction (i.e., the longitudinal direction of the reinforcing bar 2) is estimated. It is determined as the average value of the three magnetic sensors 4 to 6 of "peak position average (Xn+Xs)/2=Xm" in Table 1 above. That is, here it is estimated that "X ₀ =206 mm".

(T-b) Estimating the position of the fractured part in the Y-axis direction Next, the position of the fractured part in the reinforcing bar 2 in the Y-axis direction (i.e., the horizontal distance from the magnetic sensor 5 at the center in the arrangement direction) "Y ₀ ”, which is determined as the sensor position of the maximum value of the three magnetic sensors 4 to 6 above in “average peak height (|Pn|+|Ps|)/2=Pm” in Table 1. . Here, since the peak height average "34.1" corresponding to the magnetic sensor 5 is the maximum value among the three magnetic sensors, the position "Y ₀ = 0" of the magnetic sensor 5 in the Y-axis direction is the fracture point. is estimated as the position in the Y-axis direction.

C: Third Embodiment As will be described later, the nondestructive testing device Z according to the third embodiment differs only in the configuration related to estimating the position of the fractured part of the reinforcing bar 2, and the other configurations are the same as in the third embodiment. This is the same as the case of the non-destructive testing apparatus Z in the second embodiment.

C-1: Functional Block Diagram FIG. 20 shows a functional block diagram of the non-destructive testing apparatus Z according to the third embodiment. This functional block diagram has the same basic configuration as the functional block diagram of the non-destructive testing device Z according to the second embodiment, and the difference is that in the second embodiment, the magnetic flux density measuring section 31 In this embodiment, the magnetic flux density measuring section 31 is equipped with four magnetic sensors 4 to 7, whereas the magnetic flux density measuring section 31 is equipped with three magnetic sensors 4 to 6.

As shown in FIG. 20, among these four magnetic sensors, three magnetic sensors 4 to 6 are arranged in a row at a predetermined interval (50 mm) in the Y-axis direction perpendicular to the longitudinal direction of the reinforcing bar 2. , another magnetic sensor 7 is installed directly above (in the Z-axis direction) the magnetic sensor 5 located at the center of the three magnetic sensors 4 to 6 at an interval of 50 mm.

Then, the three magnetic sensors 4 to 6 arranged in the Y-axis direction estimate the position of the fractured part of the reinforcing bar 2 in two directions, the X-axis direction and the Y-axis direction, while the magnetic sensors 4 to 6 arranged in the Z-axis direction The position of the fractured portion in the Z-axis direction is estimated by the sensor 5 and the magnetic sensor 7.

C-2: Estimating the position of the fractured part When estimating the position of the fractured part of the reinforcing bar 2, various information is collected as shown in Tables 2 and 3 based on the detection values of the magnetic sensors 4 to 7. be obtained.

(B) Acquisition of Table 2 First, three magnetic sensors 4 to 6 and one magnetic sensor 7 are used to calculate the two bipolar peaks “Pn” and “Ps” (see FIG. 19) of the second-order differential, respectively. The peak height “Pn (μT/cm ² )” of the peak “Pn”, the peak height Ps (μT/cm ² ) of the peak “Ps”, and the peak height average “(|Pn|+|Ps|)” /2=Pm", the peak ratio "|Pn|/|Ps|=Pj", the peak position "Xn (mm)" of the peak "Pn", and the peak position "Xs (mm)" of the peak "Ps". , the peak width "|Xn-Xs|=Xj", and the peak position average "(Xn+Xs)/2=Xm" are determined. This is shown in Table 2 (Table 2-1 and Table 2-2).

(b) Estimating the position of the fractured part in the X-axis direction First, the position "X ₀ " of the fractured part in the reinforcing bar 2 in the X-axis direction (i.e., the longitudinal direction of the reinforcing bar 2) is estimated. It is obtained as the average value of the three magnetic sensors 4 to 6 of "peak position average (Xn+Xs)/2=Xm" in 3-2. That is, here it is estimated that "X ₀ =206 mm".

(c) Estimation of the position of the broken part in the Y-axis direction Next, the position of the broken part in the reinforcing bar 2 in the Y-axis direction (i.e., the horizontal distance from the magnetic sensor 5 at the center in the arrangement direction) "Y ₀ " Although this is an estimate, this is determined as the sensor position of the maximum value of the above three magnetic sensors 4 to 6 of "average peak height (|Pn|+|Ps|)/2=Pm" in Table 2-1. . Here, since the peak height average "34.1" corresponding to the magnetic sensor 5 is the maximum value among the three magnetic sensors, the position "Y ₀ = 0" of the magnetic sensor 5 in the Y-axis direction is the fracture point. is estimated as the position in the Y-axis direction.

(d) Estimating the position of the fractured part in the Z-axis direction Furthermore, the position of the fractured part in the reinforcing bar 2 in the Z-axis direction (distance from the central magnetic sensor 5) "Z ₀ " is determined from Table 3. Determined by calculation.

That is, among the three magnetic sensors 4 to 6, the magnetic sensor 5 whose average peak height is the maximum value is used as a reference, and the magnetic flux density is inversely proportional to the cube of the distance. 7 (that is, the magnetic sensor on the side far from the reinforcing bar 2), the position _Z0 calculated by the ratio to the peak height average value "Pm (z=-50)" is set as the estimated position in the Z-axis direction.
In this embodiment, Z ₀ =105 mm.

Z ₀ = |Z|× ³ √p/(1- ³ √p) ...Formula 1
p=Pm(z)/Pm(0)...Formula 2

Note that the above estimation formulas (Formula 1 and Formula 2) are calculated as follows.
Because magnetic flux density is inversely proportional to the cube of distance,
Formula (a) Pm(0)=B/Z ₀ ³
Formula (b) Pm(z)=B/(Z ₀ + |Z|) ³
Here, if we eliminate B using equations (a) and (b), we get
Formula (c) Pm(z)/Pm(0)=Z ₀ ³ /(Z ₀ + |Z|) ³ =p
Taking the cube root of the above formula (c), we get
Formula (d) Z ₀ / (Z ₀ + | Z |) = ³ √p
Formula (e) Z ₀ = |Z|× ³ √p/(1- ³ √p)
becomes.

The measurement of the magnetic flux density using four magnetic sensors can be performed, for example, by using a single magnetic sensor, scanning it sequentially at the positions of the four magnetic sensors 4 to 7, and finally measuring the magnetic flux density at the four magnetic sensors 4 to 7. Magnetic flux density values can also be obtained.

The effects, etc. of each component other than those described above are the same as in the case of the non-destructive testing device Z according to the second embodiment, so the relevant explanations in the second embodiment will be referred to and the explanations herein will be made as follows. The explanation will be omitted.

The non-destructive testing method and testing device according to the present invention can be used for non-destructive testing to detect the presence or absence of damaged parts of steel materials buried in concrete bodies, such as bridges, buildings, or concrete poles.

1...Concrete body 2...Reinforcement bars (steel material to be inspected)
3...Magnet 4-7...Magnetic sensor 8...Distance sensor 21...Magnetic flux density measuring section 22...Calculating section 23...Judging section 24...Display section 25...Magnetizing section 30...Magnetizing section 31...Magnetic flux density measurement section 32...Calculation section 33...Judgment section 34...Estimation section 35...Display section Z...Non-destructive testing device Za...Device main body

Claims (8)

The presence or absence of damaged parts of the steel material to be inspected is detected by magnetizing the steel material to be inspected from the outside of the concrete body in which the steel material to be inspected is buried using a magnet, and then measuring the magnetic flux density of the concrete body using a magnetic sensor. In the non-destructive testing method,
After arranging the magnetized surface of the magnet close to the surface of the concrete body, the steel material to be inspected is magnetized along its longitudinal direction by moving it appropriately or without moving it, and then removing the magnet. magnetization process,
A magnetic flux density measuring step of measuring the magnetic flux density of the steel material to be inspected by or without moving the magnetic sensor as appropriate after arranging it close to the surface of the concrete body;
a calculation step of calculating a magnetic flux density differential waveform by differentiating the magnetic flux density by two orders or more with respect to the longitudinal direction of the steel material to be inspected;
a determination step of determining the presence or absence of damage in the steel material to be inspected based on the magnetic flux density differential waveform obtained in the calculation step;
including ,
In the determination step, when the magnetic flux density differential waveform is a waveform with an even order differential of the second order or higher, the waveform changing portion is determined to be a bipolar shape with approximately point symmetry based on the "determination method for approximately point symmetrical bipolar shape" described later. A non-destructive testing method characterized in that the presence or absence of damage to the steel material to be inspected is determined based on whether or not the steel material to be inspected is damaged.

"Determination method for nearly point-symmetric bipolar forms"
In the waveform changing part of the above magnetic flux density differential waveform, the ratio of the absolute value of the negative side peak height “Pn” and the positive side peak height “Ps” “|Pn|/|Ps|” is “0.5 to 2'', it is determined that the waveform changing section is a substantially point-symmetrical bipolar type. The presence or absence of damaged parts of the steel material to be inspected is detected by magnetizing the steel material to be inspected from the outside of the concrete body in which the steel material to be inspected is buried using a magnet, and then measuring the magnetic flux density of the concrete body using a magnetic sensor. In the non-destructive testing method,
After arranging the magnetized surface of the magnet close to the surface of the concrete body, the steel material to be inspected is magnetized along its longitudinal direction by moving it appropriately or without moving it, and then removing the magnet. magnetization process,
A magnetic flux density measuring step of measuring the magnetic flux density of the steel material to be inspected by or without moving the magnetic sensor as appropriate after arranging it close to the surface of the concrete body;
a calculation step of calculating a magnetic flux density differential waveform by differentiating the magnetic flux density by two orders or more with respect to the longitudinal direction of the steel material to be inspected;
a determination step of determining the presence or absence of damage in the steel material to be inspected based on the magnetic flux density differential waveform obtained in the calculation step;
including,
In the above determination step, when the magnetic flux density differential waveform is a waveform with an odd order differential of the third order or higher, the waveform changing part is a substantially line symmetric single peak based on the "approximately line symmetric single peak determination method" described later. A non-destructive testing method characterized by determining the presence or absence of damage in the steel material to be inspected based on whether or not the steel material has a peak shape.

"Method for determining unimodal shapes with approximately line symmetry"
The position in the longitudinal direction of the steel material to be inspected corresponding to the peak value in the waveform change part of the magnetic flux density differential waveform is set as a reference position, and two points each correspond to approximately "1/2" of the peak value in the waveform change part. When the distance from the above reference position is approximately the same,
Alternatively, the position in the longitudinal direction of the steel material to be inspected corresponding to the peak value in the waveform changing part is set as a reference position, and is surrounded by the position from the peak value in the waveform changing part to approximately "1/2" of the peak value. In the area, when the area on the negative side and the area on the positive side of the reference position are approximately the same, it is determined that the waveform changing portion is approximately axisymmetric and single-peaked.
In the non-destructive testing method according to claim 1 or 2 ,
Using at least one of the magnetic sensors , the magnetic sensor is placed in the longitudinal direction of the steel material to be inspected at at least two positions in a direction perpendicular to the longitudinal direction of the steel material to be inspected and along the surface of the concrete body. The magnetic flux density differential waveform is obtained by moving the magnetic flux density differential waveform, and based on the magnetic flux density differential waveform, the damage position of the steel material to be inspected in the longitudinal direction and the damage position of the steel material to be inspected in the direction along the surface of the concrete body are determined. A non-destructive testing method characterized by including an estimation step of estimating each of the following. In the non-destructive testing method of claim 1 or 2
Using at least one magnetic sensor , the magnetic sensor is moved in the longitudinal direction of the steel material to be inspected in a direction perpendicular to the surface of the concrete body and at least two positions different in distance from the surface. to obtain the above magnetic flux density differential waveform,
A non-destructive inspection method comprising the step of estimating a damage position of the steel material to be inspected in a direction perpendicular to the surface of the concrete body based on each of the magnetic flux density differential waveforms. The presence or absence of damaged parts of the steel material to be inspected is detected by magnetizing the steel material to be inspected from the outside of the concrete body in which the steel material to be inspected is buried using a magnet, and then measuring the magnetic flux density of the concrete body using a magnetic sensor. A non-destructive inspection device,
After the magnetization surface is placed close to the surface of the concrete body, the steel material to be inspected is magnetized along the longitudinal direction of the steel material by moving it appropriately or without moving it, and then removed. A magnetic part,
A magnetic flux density measurement unit that measures the magnetic flux density of the steel material to be inspected by arranging the magnetic sensor close to the surface of the concrete body and then moving it appropriately or without moving it;
a calculation unit that calculates a magnetic flux density differential waveform by differentiating the magnetic flux density by two or more orders in the longitudinal direction of the steel material to be inspected;
a determination unit that determines the presence or absence of damage in the steel material to be inspected based on the magnetic flux density differential waveform obtained by the calculation unit;
In addition to providing
When the magnetic flux density differential waveform is a waveform with an even-order differential of the second order or higher, the determination unit determines that the waveform changing portion is a bipolar waveform that is approximately point symmetric based on the “approximately point symmetrical bipolar determination method” described later. A non-destructive inspection apparatus characterized in that the presence or absence of damage to the steel material to be inspected is determined based on whether or not the steel material to be inspected is damaged.

"Determination method for nearly point-symmetric bipolar forms"
In the waveform changing part of the above magnetic flux density differential waveform, the ratio of the absolute value of the negative side peak height “Pn” and the positive side peak height “Ps” “|Pn|/|Ps|” is “0.5 to 2'', it is determined that the waveform changing section is a substantially point-symmetrical bipolar type. The presence or absence of damaged parts of the steel material to be inspected is detected by magnetizing the steel material to be inspected from the outside of the concrete body in which the steel material to be inspected is buried using a magnet, and then measuring the magnetic flux density of the concrete body using a magnetic sensor. A non-destructive testing device,
After the magnetization surface is placed close to the surface of the concrete body, the steel material to be inspected is magnetized along the longitudinal direction of the steel material by moving it appropriately or without moving it, and then removed. A magnetic part,
A magnetic flux density measurement unit that measures the magnetic flux density of the steel material to be inspected by arranging the magnetic sensor close to the surface of the concrete body and then moving it appropriately or without moving it;
a calculation unit that calculates a magnetic flux density differential waveform by differentiating the magnetic flux density by two or more orders in the longitudinal direction of the steel material to be inspected;
a determination unit that determines the presence or absence of damage in the steel material to be inspected based on the magnetic flux density differential waveform obtained by the calculation unit;
In addition to providing
When the magnetic flux density differential waveform is a waveform with an odd-order differential of the third order or higher, the determination unit determines that the waveform changing portion is a substantially line-symmetric single-peak shape based on the “approximately line-symmetric single-peak determination method” described later. A non-destructive inspection device characterized in that the presence or absence of damage to the steel material to be inspected is determined based on whether or not the steel material to be inspected has a peak shape .

" Method for determining unimodal shapes with approximately line symmetry"
The position in the longitudinal direction of the steel material to be inspected corresponding to the peak value in the waveform change part of the magnetic flux density differential waveform is set as a reference position, and two points each correspond to approximately "1/2" of the peak value in the waveform change part. When the distance from the above reference position is approximately the same,
Alternatively, the position in the longitudinal direction of the steel material to be inspected corresponding to the peak value in the waveform changing part is set as a reference position, and is surrounded by the position from the peak value in the waveform changing part to approximately "1/2" of the peak value. In the area, when the area on the negative side and the area on the positive side of the reference position are approximately the same, it is determined that the waveform changing portion is approximately axisymmetric and single-peaked. The non-destructive testing device according to claim 5 or 6 ,
The magnetic sensor includes at least two magnetic sensors arranged in a row at a predetermined interval in a direction perpendicular to the longitudinal direction of the steel material to be inspected and along the surface of the concrete body,
Based on the magnetic flux density differential waveform corresponding to each of the magnetic sensors, a damage position in the longitudinal direction of the steel material to be inspected and a damage position of the steel material to be inspected in a direction along the surface of the concrete body are estimated, respectively. A non-destructive inspection device characterized by comprising an estimator. The non-destructive testing device according to claim 5 or 6 ,
As the magnetic sensor, magnetic sensors are provided at at least two positions in a direction perpendicular to the surface of the concrete body and at different distances from the surface,
A non-destructive inspection characterized by comprising an estimation unit that estimates a damage position of the steel material to be inspected in a direction perpendicular to the surface of the concrete body based on the magnetic flux density differential waveform corresponding to each of the magnetic sensors. Device.

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