JP2002277442A - Non-destructive inspection method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect cracks of materials to be inspected comprising a non- magnetic material. SOLUTION: The materials to be inspected comprising the non-magnetic material undergoes a magnetizing processing. The distribution of leakage flux density of the magnetized materials to be inspected is measured to estimate at least one of the direction in which damaged sites of the materials to be inspected spread based on the distribution pattern of the flux density peak value of the distribution of the leakage flux density, the degree of the damages of the damaged sites of the materials to be inspected based on the flux density peak value of the distribution of the leakage flux density and the lengths of the damaged sites of the materials to be inspected based on the distance between the flux density peak values of the distribution of the leakage flux density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-destructive inspection method and a non-destructive inspection device, and more particularly to a method for measuring a leakage magnetic flux density of a non-magnetic material from a test object to inspect a damaged portion of the test object. The present invention relates to a non-destructive inspection method and a non-destructive inspection device.

[0002]

2. Description of the Related Art Various methods have been proposed for detecting the position and size of cracks in ferromagnetic steel pipes or steel plates. For example, in Japanese Patent Application Laid-Open No. 06-294850, the leakage magnetic flux caused by the forced magnetization and the minute magnetic flux density change caused by the induced magnetization of the test object made of a ferromagnetic material are utilized by utilizing the hysteresis characteristic of the amorphous magnetic core. Methods for detecting and performing various nondestructive inspections have been proposed.

However, this nondestructive inspection method can detect the position of a crack when the object to be inspected is a ferromagnetic material, but cannot detect a crack when the object to be inspected is a nonmagnetic material. There was a problem that it was not possible.

The present invention has been made to solve the above problems, and provides a non-destructive inspection method and a non-destructive inspection device capable of detecting a crack even if the test object is a non-magnetic material. The purpose is to:

[0005]

In order to achieve the above object, a nondestructive inspection method according to a first aspect of the present invention is to provide a non-destructive inspection method, comprising: magnetizing a test object made of a non-magnetic material; The leakage magnetic flux density distribution is measured, and the direction of development of the damaged portion of the test object based on the distribution pattern of the magnetic flux density peak value of the leakage magnetic flux density distribution, and the inspection target based on the magnetic flux density peak value of the leakage magnetic flux density distribution At least one of a damage degree of the damaged part of the body and a damage length of the damaged part of the test object based on a distance between magnetic flux density peak values of the leakage magnetic flux density distribution is estimated. Further, the nondestructive inspection apparatus of the third invention comprises a magnetizing means for magnetizing a test object made of a nonmagnetic material,
A leakage magnetic flux density distribution measuring means for measuring a leakage magnetic flux density distribution of the inspection object magnetized by the magnetization processing means; and the inspection object based on a distribution pattern of magnetic flux density peak values of the leakage magnetic flux density distribution. Direction of the damaged portion, the degree of damage to the damaged portion of the test object based on the magnetic flux density peak value of the leakage magnetic flux density distribution and the distance between the magnetic flux density peak values of the leakage magnetic flux density distribution. Estimating means for estimating at least one of the damage lengths of the damaged part.

[0006] The damaged portion generated in the non-magnetic material has a characteristic that it becomes ferromagnetic by transformation into a martensite phase. According to the first and third aspects of the present invention, the damaged portion of the non-magnetic material transformed into martensite is magnetized by magnetization, and the peak value of the leakage magnetic flux density is distributed along the damaged portion. Based on the distribution pattern of the magnetic flux density peak values of the distribution, it is possible to estimate the propagation direction of the damaged portion of the test object. Further, since the degree of damage of the damaged portion of the test object made of a non-magnetic material is proportional to the magnetic flux density peak value of the leakage magnetic flux density distribution, the test object is determined based on the magnetic flux density peak value of the leakage magnetic flux density distribution. The degree of damage of the damaged part can be estimated. Further, since the damage length of the damaged portion of the test object made of a nonmagnetic material and the distance between the magnetic flux density peak values of the leakage magnetic flux density distribution are in a proportional relationship, the test object is inspected based on the distance between the magnetic flux density peak values. The length of injury of the body injury can be estimated.

According to a second aspect of the present invention, there is provided a non-destructive inspection method, wherein an inspection object made of a non-magnetic material is magnetized in a plurality of directions, and the leakage magnetic flux of the inspection object in the plurality of magnetized processing directions. The density distribution is measured, and the shape of the damaged portion of the test object based on the pattern of the leakage magnetic flux density distribution, the degree of damage of the damaged portion of the test object based on the peak value of the leakage magnetic flux density distribution And a damage length of a damaged portion of the inspection object based on a distance between magnetic flux density peak values of the respective leakage magnetic flux density distributions. Also, the fourth
A non-destructive inspection apparatus according to the invention comprises: a magnetizing means for magnetizing an object to be inspected made of a non-magnetic material from a plurality of directions; and Leakage magnetic flux density distribution measuring means for measuring each of the magnetic flux density distributions, the shape of the damaged portion of the test object based on the pattern of each magnetic flux density distribution, the magnetic flux density peak value of each magnetic flux density distribution Estimating means for estimating at least one of a damage degree of the damaged portion of the test object based on a distance between magnetic flux density peak values of the respective leakage magnetic flux density distributions based on a degree of damage of the damaged portion of the test object. It is comprised including. According to the second and fourth inventions, the leakage magnetic flux density distribution of the test object in each of a plurality of magnetization directions is measured, and the pattern of each leakage magnetic flux density distribution, the magnetic flux density peak value,
The shape of the damaged part of the test object, the degree of damage of the damaged part, and the length of the damage of the damaged part are estimated based on the distance between the magnetic flux density peak values. Of the damaged part, the degree of damage to the damaged part, and the length of damage to the damaged part.

According to the first or second invention, the object to be inspected is demagnetized before the magnetization of the object to be inspected. According to the third or fourth invention, the degaussing means for demagnetizing the object to be inspected is provided. By further providing, it is possible to eliminate the magnetization state in which the direction is not clear, so that the direction of the magnetization by the magnetization process can be clarified.

The measurement of the leakage magnetic flux density distribution of the first and second inventions and the measurement of the leakage magnetic flux density distribution by the leakage magnetic flux density distribution measuring means of the third and fourth inventions are performed by using a thin film flag gate sensor, Sensor and SQUID
(Superconducting quantum interferometer) or the like can be appropriately performed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the present embodiment will be described.

A fatigue test was carried out using a SUS304 steel plate under the following conditions, and the martensite phase distribution and the leakage magnetic flux density distribution were measured to investigate the relationship between the crack and the leakage magnetic flux density distribution.

In the fatigue test, a sinusoidal repetitive load having a stress range Δσ = constant, a repetition rate of 10 Hz and a stress ratio R = 0.1 was applied, and a crack was propagated from a slit having a length of 3.6 mm. The value of the range (total amplitude) Δσ of the stress to be applied is changed by several levels, and 2a = 3.9 to 15.1 mm (a
/W=0.1 to 0.4, W: width of test piece). The value of the stress intensity factor range ΔK at the end of the test is 18 to 3
The range was 7 MPam ^1/2 . The stress intensity factor range ΔK is one of parameters frequently used in fracture mechanics, and is an amount that uniquely defines a stress field near a crack tip, and is expressed as ΔK = FΔσ (πa) ^1/2. As described above, the parameter is represented by the correction coefficient F obtained from the theory of elasticity, a half of the crack length a and the applied stress range Δσ, and is a parameter indicating the degree of damage to the crack tip existing in the member.

[0013] The leakage magnetic flux density of the test object cracked in the fatigue test was measured by the following apparatus. As shown in FIG. 1, the measuring device includes a magnetic sensor detector 12 fixed to a tip 16A of a lift portion of a Z-axis stand 16. The magnetic sensor detector 12 is connected to the magnetic sensor main body 14 via a wiring. Magnetic sensor body 1
4 includes a DC power supply 24 and a digital voltmeter 2.
2 is connected, and the digital voltmeter 22 is connected to a personal computer 26. The XY table 18 is arranged so that the mounting table 18A is located below the magnetic sensor detector 12.
X-axis table 18B and Y-axis table 18
C is connected to the stage controller 20. The stage controller 20 is connected to a personal computer 26. In the test, one magnetic sensor was used.
A thin film flux gate magnetic sensor (FG sensor) having a measurement range of 10 to 10 ^-5 G is used.

Next, a method of measuring the leakage magnetic flux density of the test object will be described according to the procedure shown in the block diagram of FIG.

First, in step 100, a test object 28, which is a non-magnetic material, is subjected to degaussing processing. This process is performed to prevent the influence of spontaneous magnetization because the direction of the magnetization of the test object due to spontaneous magnetization is not clear.However, it is not always necessary to perform degaussing process. It is also possible to proceed to the procedure described below. The degaussing process can be performed by applying an alternating magnetic field whose strength gradually decreases to the object to be inspected and canceling the magnetization of the member.

Next, in step 102, a magnetization process is performed in a direction in which a crack generated in the inspection object 28 (hereinafter referred to as "X-axis direction"). As shown in FIG.
Two 0.4T permanent magnets with the same direction of the N pole
This can be performed by magnetizing the test object 28 so as to sandwich the test object 28 in the X-axis direction, and generating a magnetic field in a known direction from the test object. The magnetizing process can also be performed by applying a magnetic field that causes the test object to be in a magnetically saturated state in the X-axis direction.

Next, in step 106, the distribution of the magnetic flux leakage from the device under test 28 is measured. The measurement of the leakage magnetic flux density distribution is performed as follows. As shown in FIG.
Is mounted on the XY stage mounting table 18A of the nondestructive inspection apparatus 10, and the Z-axis stand 16 is adjusted to keep the distance (lift-off value) between the inspection object 28 and the magnetic sensor detector 12 constant. Then, by controlling the XY table 18 with the personal computer 26, the test object 28 is moved, the magnetic sensor detector 12 scans the test object 28, and measures the leakage magnetic flux density distribution from the test object 28. .
Note that the above-described lift-off value is set in consideration of the amount of magnetization of the object to be inspected, but may be any value as long as it does not exceed the measurement limit of the magnetic sensor to be used.

The measurement results obtained by the above measurement are shown below.

[Measurement result 1] Stress amplitude Δσ = 200MP
a, 2a = 14.1 mm (a / W = 0.4), ΔK =
FIG. 5 shows the measurement results of the martensite phase distribution and the leakage magnetic flux density distribution in the SUS304 flat plate damaged by 33.0 MPam ^1/2 . 5A is a distribution of a martensite phase in the vicinity of a crack, FIG. 5B is a leakage magnetic flux density distribution at a lift-off value of 1.5 mm from a test object during the X-axis direction magnetization processing, and FIG. 7 shows a leakage magnetic flux density distribution at a lift-off value of 2.5 mm from a test object during a Z-axis direction magnetization process.

[Measurement result 2] Stress amplitude Δσ = 242MP
a, 2a = 10.6 mm (a / W = 0.29), ΔK
FIG. 6 shows the measurement results of the martensite phase distribution and the leakage magnetic flux density distribution in the SUS304 flat plate damaged at = 33.0 MPam ^1/2 . (A) of FIG.
Martensite phase distribution near cracks, (B) shows leakage magnetic flux density distribution at a lift-off value of 1.5 mm from the test object during X-axis magnetization, and (C) shows leakage magnetic flux density during Z-axis magnetization. 5 shows a leakage magnetic flux density distribution at a lift-off value of 2.5 mm from a test object.

[Measurement result 3] Stress amplitude Δσ = 200MP
a, 2a = 10.3 mm (a / W = 0.29), ΔK
FIG. 7 shows the measurement results of the distribution of the martensite phase and the distribution of the leakage magnetic flux in the SUS304 plate damaged at = 24.5 MPam ^1/2 . (A) of FIG.
Martensitic phase distribution near cracks, (B) shows leakage magnetic flux density distribution at 1.5 mm lift-off value from test object during X-axis magnetization, and (C) shows leakage magnetic flux density during Z-axis magnetization. 4 shows a leakage magnetic flux density distribution at a lift-off value of 2.5 mm from a test object.

According to FIGS. 5 (B), 6 (B) and 7 (B) showing the leakage magnetic flux density distribution during the X-axis direction magnetizing treatment obtained from the measurement results 1, 2 and 3, When the magnetizing treatment is performed in the axial direction, peaks of the positive and negative leakage magnetic flux densities appear along the crack, and it can be confirmed that the minimum value or the maximum value of the leakage magnetic flux density appears near both ends of the crack. . this is,
The martensitic phase induced in the vicinity of the crack (FIG. 5A)
6 (A) and FIG. 7 (A)).
(B), FIG. 6 (B), and FIG. 7 (B), as shown in the respective lower figures, it is like a single magnet having both N pole and S pole in the generation region. This indicates that the wake area formed around the crack is a stronger magnetic material than the surrounding fabric structure, and that the tendency becomes more pronounced as approaching the crack tip.

FIG. 5 shows the leakage magnetic flux density distribution at the time of the magnetizing treatment in the Z-axis direction obtained from the measurement results 1, 2 and 3.
According to (C), FIG. 6 (C), and FIG. 7 (C), when the magnetization process is performed in the Z-axis direction, peaks of the leakage magnetic flux density appear near both sides of the crack tip. As in the case where the magnetizing process is performed in the X-axis direction, FIG.
This is considered to be because the martensite region is like a magnet as shown in the lower diagram of each of FIG. 7C and FIG. 7C.

From the above measurement results, it is possible to estimate the crack propagation direction of the test object based on the distribution pattern of the peak value of the measured leakage magnetic flux density. For example, when the leakage magnetic flux density distribution as shown in FIG. 5A is obtained by the measurement, it is estimated that a crack extending in the X-axis direction is generated along the peak value of the leakage magnetic flux density. be able to.

Next, the temperature was 273 K, the lift-off value when magnetized in the X-axis direction was 1.5 mm, and the lift-off value when magnetized in the Z-axis direction was 2.5 mm. , The applied stress amplitude Δσ, and ΔK level were changed, and the other conditions were the same as those in the above fatigue test.
A fatigue test was performed on a 304 plate, and the above procedure 100 to 100 was performed.
106, the leakage magnetic flux density distribution was measured.

When the magnetizing treatment is performed in the X-axis direction, the minimum value of the leakage magnetic flux density peak obtained by the measurement is represented by B _zmin ,
Assuming that the maximum value is B _zmax and the distance between the peaks is 2 LA, the relationship between the peak values B _zmin and B _{zmax of the} leakage magnetic flux density and the degree of damage ΔK received by the member is shown in FIG.
FIG. 9 shows the relationship between A and the actual crack length 2a.

When the peak values of the leakage magnetic flux densities obtained by the measurement when the magnetization treatment is performed in the Z-axis direction are B _zmax 1 and B _zmax 2 and the distance between the peaks is 2 LB, FIG. 10 shows the relationship between the peak values B _zmax 1 and B _zmax 2 of the density and ΔK, and FIG. 11 shows the relationship between the distance 2LB between the peaks and the actual crack length 2a.

As shown in FIGS. 8 and 10, B _zmin ,
Between B _zmax and the load was [Delta] K, B _{zm ax} 1, a linear relationship is established between the B _zmax 2 and the load was [Delta] K, also with respect to different same [Delta] K value against the crack length substantially the same value of B _zmin, B _zmax and B _zmax 1, B _zmax 2 is obtained Te.
That is, it is understood that the peak value of the measured leakage magnetic flux density depends on the ΔK value. Therefore, B _zmin and B
_zmax, it is possible to estimate the received degree of damage of the member by measuring B _zmax 1 and B _zmax 2.

Further, as shown in FIGS. 9 and 11, a linear relationship is established in the relationship between the peak distance of the leakage magnetic flux density and the actual crack length. By measuring, the actual crack length can be estimated.

Further, as shown in FIG. 5, FIG. 6, and FIG. 7, since the shape of the magnetic flux density distribution measured depending on the direction of the magnetization process differs even for the same crack, the magnetic flux density distribution The propagation direction of the crack that has entered the member can also be estimated from the shape.

Next, an embodiment of the present invention will be described with reference to the drawings.

The non-destructive inspection apparatus of the present embodiment has the same configuration as that of the measuring apparatus shown in FIG. 1, and a description thereof will be omitted. The storage unit (not shown) of the personal computer 26 stores the data obtained by the above-described measurement.
Crack growth direction data for estimating the direction of crack propagation from the distribution of magnetic flux peak values in the leakage magnetic flux density distribution, crack degree data in which the relationship between the magnetic flux peak value of the leakage magnetic flux density and the degree of the crack is associated, and the magnetic flux of the leakage magnetic flux density Crack length data in which the relationship between the distance between peak values and the length of the crack is associated is stored.

Next, a non-destructive inspection method using the non-destructive inspection device of the present embodiment will be described.

In the same manner as in the above procedures 100 to 106,
The test object 28, which is a non-magnetic material, is subjected to a demagnetization process and a magnetization process, and the leakage magnetic flux density distribution is measured.

Next, in step 108, a damaged portion of the inspection object is evaluated.

From the above test results, it has been confirmed that the vicinity of the crack portion of the non-magnetic material has become ferromagnetic due to martensitic transformation, and based on the distribution pattern of the peak value of the measured leakage magnetic flux density. Thus, it is possible to estimate the direction of crack propagation in the test object.

From the above test results, it is known that the peak value of the magnetic flux density in the leakage magnetic flux density distribution is proportional to the degree of damage to the device under test. Thus, the degree of damage to the test object can be estimated from the measured magnetic flux density peak value of the leakage magnetic flux density distribution.

Further, from the above test results, the peak values of the magnetic flux density of the leakage magnetic flux density distribution appear near both sides of the crack tip,
It is known that the distance between the peak values of the magnetic flux density and the crack length of the test object are in a proportional relationship. Therefore, the length of the crack in the test object can be estimated from the distance between the measured magnetic flux density peak values of the leakage magnetic flux density distribution.

Next, in step 110, a non-destructive detection method is established based on the above-described evaluation of the damaged portion of the inspection object.

The storage section of the personal computer 26 stores the leakage magnetic flux density distribution data of the test object 28 measured according to the above procedure. When an instruction for estimating any one of the crack shape, crack degree, and crack length of the inspection object is input from an input unit (not shown) of the personal computer 26, the crack estimation processing shown in FIG. 13 is performed.

In step 120, it is determined whether or not the input instruction is a process for estimating the crack growth direction of the test object. If the input instruction is a process for estimating the crack growth direction of the test object, the pattern of the leakage magnetic flux density distribution data is analyzed in step 122 by using the crack shape data stored in the storage unit. The crack growth direction is estimated, and the crack growth direction of the test object estimated in step 124 is displayed on the display unit 26A of the personal computer 26, followed by terminating the present process.

If the input instruction is not the process of estimating the crack growth direction of the object to be inspected, it is determined in step 130 whether or not the input instruction is the process of estimating the degree of crack of the object to be inspected. When the input instruction is a process of estimating the degree of cracking of the test object, the magnetic flux peak value of the leakage magnetic flux density distribution stored in the storage unit is extracted in step 132, and the magnetic flux peak value and the magnetic flux peak value are extracted in step 134. The degree of crack is estimated based on the degree-of-crack data stored in the storage unit, the degree of crack of the inspected object estimated in step 136 is displayed on the display unit 26A of the personal computer 26, and the process ends.

If the input instruction is not a process of estimating the degree of cracking of the object to be inspected, it is determined in step 140 whether the input instruction is a process of estimating the crack length of the object to be inspected. If the input instruction is a process for estimating the crack length of the test object, the distance between the magnetic flux peak values is calculated in step 142 based on the leakage magnetic flux density distribution data stored in the storage unit. Then, the crack length of the test object is estimated based on the distance between the magnetic flux peak values calculated in step 144 and the crack length data stored in the storage unit, and the crack length of the test object estimated in step 146 is determined. The length is displayed on the display unit 26A of the personal computer 26, and the process ends.

If the input instruction is not the process of estimating the crack length of the object to be inspected, an error is displayed in step 150 and the process is terminated.

According to this estimation processing, the direction, extent and length of the crack propagation in the test object can be automatically estimated based on the distribution of the measured magnetic flux peak value of the leakage magnetic flux density.

As described above, according to the present embodiment, the test object made of a non-magnetic material is magnetized, and the leakage magnetic flux density distribution of the magnetized test object is measured. The direction of crack propagation in the test object can be estimated based on the pattern of the leakage magnetic flux density distribution obtained, and the degree of cracking of the test object based on the magnetic flux density peak value of the leakage magnetic flux density distribution obtained by measurement Can be estimated, and the length of the crack in the test object can be estimated based on the distance between the magnetic flux density peak values of the leakage magnetic flux density distribution obtained by the measurement.

In the present embodiment, the magnetizing process is performed in two directions, the X-axis direction and the Z-axis direction, and the leakage magnetic flux density distribution in each case is measured to evaluate the damaged portion. It is also possible to evaluate the damaged portion from the measurement result of the leakage magnetic flux density distribution when the magnetization process is performed from one direction.

In this embodiment, the leakage magnetic flux density was measured without placing a shield on the object to be inspected. However, when stainless steel was placed on a member having a crack,
That is, even when a shield is placed between the damaged portion and the magnetic sensor detection section 12, a change in the leakage magnetic flux density can be detected. Therefore, damage such as a crack generated inside without being shown on the surface can also be detected by measuring the leakage magnetic flux density from the test object.

In this embodiment, the XY table is horizontally moved to measure the leakage magnetic flux density distribution of the test object. As shown in FIG. 12, the magnetic sensor detector 12 is manually scanned to detect the leakage magnetic flux density. Density can also be measured.
According to this method, as shown in FIG. 12B, the measurement of the leakage magnetic flux density of a member having a curved surface such as a steel pipe can be easily performed.

[0050]

As described above, according to the first and third aspects of the present invention, the damaged portion generated in the non-magnetic material has the property that it becomes ferromagnetic by transformation into the martensite phase, The damaged portion of the non-magnetic material that has undergone site transformation is magnetized by magnetization, and the magnetic flux density peak value of the leakage magnetic flux density is distributed along the damaged portion. The direction of development of the damaged portion of the test object can be estimated. Further, since the degree of damage of the damaged portion of the test object made of a non-magnetic material is proportional to the magnetic flux density peak value of the leakage magnetic flux density distribution, the test object is determined based on the magnetic flux density peak value of the leakage magnetic flux density distribution. The degree of damage of the damaged part can be estimated. Further, since the length of the damaged portion of the test object made of a non-magnetic material and the distance between the magnetic flux density peak values of the leakage magnetic flux density distribution are in a proportional relationship, the distance between the magnetic flux density peak values is determined based on the distance between the magnetic flux density peak values. The effect is obtained that the damage length of the damaged part of the test object can be estimated.

According to the second and fourth aspects of the present invention, the leakage magnetic flux density distribution of the test object in each of a plurality of magnetization directions is measured, and the pattern of each leakage magnetic flux density distribution, the magnetic flux density peak value,
Since the shape of the damaged portion of the test object, the damage degree of the damaged portion, and the damage length of the damaged portion are estimated based on the distance between the magnetic flux density peak values, the shape of the damaged portion of the test object can be more accurately estimated. Thus, it is possible to estimate the degree of damage to the damaged portion and the damage length of the damaged portion.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a nondestructive inspection apparatus according to the present embodiment.

FIG. 2 is a diagram schematically illustrating a non-destructive inspection procedure according to the present embodiment.

FIG. 3 is a diagram illustrating an example of a method of performing a magnetization process in an X-axis direction.

FIG. 4 is a diagram illustrating an example of a method of performing a magnetization process in a Z-axis direction.

5A is a distribution diagram showing a martensite phase distribution, and FIG. 5B is a distribution diagram showing a leakage magnetic flux density distribution when magnetized in the X-axis direction. FIG. () Is a distribution diagram showing a leakage magnetic flux density distribution when a magnetization process is performed in the Z-axis direction.

6A is a distribution diagram showing a martensite phase distribution, and FIG. 6B is a distribution diagram showing a leakage magnetic flux density distribution when magnetized in the X-axis direction. () Is a distribution diagram showing a leakage magnetic flux density distribution when a magnetization process is performed in the Z-axis direction.

7A is a distribution diagram showing a martensite phase distribution, and FIG. 7B is a distribution diagram showing a leakage magnetic flux density distribution when magnetized in the X-axis direction. FIG. () Is a distribution diagram showing a leakage magnetic flux density distribution when a magnetization process is performed in the Z-axis direction.

FIG. 8: Leakage magnetic flux density when magnetized in the X-axis direction
Peak value B_zmin, B _zmaxAnd the degree of damage ΔK received by the member
5 is a graph showing the relationship of FIG.

FIG. 9 is a graph showing the relationship between the peak-to-peak distance 2LA and the actual crack length 2a when magnetized in the X-axis direction.

FIG. 10 shows peak values B _zmin and B _zmax of the leakage magnetic flux density when the magnetizing process is performed in the Z-axis direction and the damage degree Δ of the member.
6 is a graph showing the relationship of K.

FIG. 11 is a graph showing the relationship between the peak-to-peak distance 2LA and the actual crack length 2a when magnetizing in the Z-axis direction.

FIG. 12 is a schematic explanatory view of another embodiment of the present invention.

FIG. 13 is a flowchart of a crack estimation process according to the present embodiment.

[Description of Signs] 12 Magnetic sensor detector 14 Magnetic sensor main body 16 Z-axis stand 18 XY table 20 Stage controller 22 Digital voltmeter 24 DC power supply 26 Personal computer 28 Inspection object

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toru Shimizu 1-3 Term Kagurazaka, Shinjuku-ku, Tokyo F-term in the Tokyo University of Science (reference) 2F063 AA11 AA43 BB05 BB10 BC05 DA01 DA05 DB01 DB05 DD02 GA52 LA17 LA29 MA05 ZA01 ZA03 2G053 AA11 AA14 AB22 BA02 BA15 BB12 BB13 BC20 CA18 CB28 DA01 DB24

Claims (8)

[Claims] 1. A test object made of a non-magnetic material is magnetized, a leakage magnetic flux density distribution of the test object magnetized is measured, and a distribution pattern of a magnetic flux density peak value of the leakage magnetic flux density distribution is obtained. The direction of damage of the damaged portion of the test object based on the direction of damage of the damaged portion of the test object based on the magnetic flux density peak value of the leakage magnetic flux density distribution, and the distance between the magnetic flux density peak values of the leakage magnetic flux density distribution A non-destructive inspection method for estimating at least one of a damage length of a damaged portion of the inspection object based on the inspection result. 2. A test object made of a non-magnetic material is magnetized from a plurality of directions, and a leakage magnetic flux density distribution of the test object in a plurality of magnetized directions is measured. The direction of development of the damaged part of the test object based on the distribution pattern of the magnetic flux density peak value of the leakage magnetic flux density distribution, the degree of damage to the damaged part of the test object based on the peak value of each of the leakage magnetic flux density distributions, and A non-destructive inspection method for estimating at least one of a damage length of a damaged portion of the inspection object based on a distance between magnetic flux density peak values of the respective leakage magnetic flux density distributions. 3. The nondestructive inspection method according to claim 1, wherein a degaussing process is performed before the subject is magnetized. 4. The nondestructive inspection method according to claim 1, wherein the measurement of the leakage magnetic flux density distribution is performed by a magnetic sensor. 5. A magnetizing means for magnetizing a test object made of a nonmagnetic material, and a leakage magnetic flux density for measuring a leakage magnetic flux density distribution of the test object magnetized by the magnetizing processing means. Distribution measuring means, the shape of the damaged part of the test object based on the distribution pattern of the magnetic flux density peak value of the leakage magnetic flux density distribution, and the shape of the damaged part of the test object based on the magnetic flux density peak value of the leakage magnetic flux density distribution. Estimating means for estimating at least one of a damage length and a damage length of a damaged portion of the test object based on a damage degree and a distance between magnetic flux density peak values of the leakage magnetic flux density distribution. 6. A magnetizing means for magnetizing a test object made of a non-magnetic material from a plurality of directions, and a leakage magnetic flux density distribution of the test object in a plurality of magnetizing directions by the magnetizing processing means. Magnetic flux density distribution measuring means for measuring each of: a shape of a damaged portion of the test object based on a distribution pattern of a magnetic flux density peak value of each of the magnetic flux density distributions; and a magnetic flux density peak of each of the magnetic flux density distributions Estimating means for estimating at least one of a degree of damage to a damaged portion of the test object based on a value and a damage length of a damaged portion of the test object based on a distance between magnetic flux density peak values of the respective leakage magnetic flux density distributions. And a non-destructive inspection device comprising: 7. The nondestructive inspection apparatus according to claim 5, further comprising: a degaussing means for degaussing the object to be inspected. 8. The non-destructive inspection apparatus according to claim 5, wherein said leakage magnetic flux density distribution measuring means is a magnetic sensor.