JPH10177010A - Damage detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a structural material until its life expires by accurately evaluating a damage generated in the structural material of a non-magnetic body and predicting the remaining life of the structural material from the damage evaluation result. SOLUTION: In the method for detecting the surface defect of a body to be measured by applying a magnetic powder onto the surface of the non- magnetic body to be measured, the magnetic powder is applied to the surface of the body to be measured, a magnetic field or a high-frequency current is applied to the body to be measured by wiping off the magnetic material or in that state, thus magnetizing the magnetic powder. Then, a plurality of layers of the magnetic recording medium of a magnetic recording tape or a magnetic recording film are adhered on the surface of the body to be measured and a leakage magnetic flux disturbed by the surface defect of the body to be measured is recorded, and the plane shape and the depth of the surface defect of the body to be measured are evaluated. As a result, by measuring the leakage magnetic flux for generating the defect in the structure material around the defect, the presence or absence of a defect and its phase can be evaluated three-dimensionally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for damage detection for non-destructively inspecting a three-dimensional shape of a small crack generated in a non-magnetic structural material such as stainless steel in a power plant or the like.

[0002]

2. Description of the Related Art There are mainly the following examples of techniques for non-destructively detecting cracks or pits.

[0003] A known example of Japanese Patent Application Laid-Open No. 55-2920 is to detect a magnetic quantity of a magnetic substance remaining in a defect portion by infiltrating a liquid containing a magnetic substance powder into a surface opening defect of a non-magnetic material. . A known example in Japanese Patent Application Laid-Open No. 61-139743 is to input an image of the surface of a target structure using a TV camera, digitally input the image as a video signal, perform mathematical statistical processing based on image analysis, and detect damage. Method and apparatus. A known example in Japanese Patent Application Laid-Open No. 62-245960 is a method in which a target surface portion is subjected to a treatment such as polishing in advance, and after a certain period of use, a replica is observed at a position subjected to a preliminary treatment to evaluate damage.

A known example of Japanese Patent Application Laid-Open No. 63-292059 is a method and apparatus for detecting the presence or absence of a defect by applying an ultrasonic beam to an object and analyzing the reflected or diffracted ultrasonic signal. is there. JP-A 1-2480
Japanese Patent Application Laid-Open No. 49-288706 and Japanese Patent Application Laid-Open No. 5-288706 disclose that an electromagnetic coil is installed so as to face a conductor surface, and a voltage change of an IC circuit composed of the electromagnetic coil and a capacitor can be detected. And an apparatus and method for analyzing size.

[0005] A known example in Japanese Patent Application Laid-Open No. 2-213765 is an apparatus and a method for analyzing damage by detecting a change in magnetic properties due to cracks or pits. A known example in Japanese Patent Application Laid-Open No. 4-83153 is an apparatus and a method for detecting a damage or deterioration of a material from a potential difference between a reference electrode and the material as a method for detecting damage to the material in a water environment. A known example in Japanese Patent Application Laid-Open No. 5-504203 is a device and a technique for applying a shock signal to a structure and detecting the shock signal.

[0006]

It is effective to maximize the use of a structural material until the end of its life from the viewpoint of effective utilization of resources and cost reduction. In order to maximize the use of the structural material until the very end of its life, a technique is required that accurately evaluates the damage generated in the structural material and predicts the remaining life of the structural material from the damage evaluation. Since such damage evaluation in a power plant or the like is performed collectively at the time of a periodic inspection, quick damage evaluation is necessary in consideration of improvement in the operation rate of the plant. In particular, detecting cracks, which are minute defects immediately after the occurrence of corrosion, is effective in long-term operation planning of a plant.

In the invention of Japanese Patent Application Laid-Open No. 55-2920,
It is difficult to infiltrate a liquid containing a magnetic substance powder into minute surface opening defects or to evaluate the opening depth. In the invention of JP-A-4-83153, the presence or absence of deterioration or damage and the position Information is available, but no information about the size and depth of the damage. For this reason, it is impossible to periodically evaluate the damage, and it is difficult to apply the method to the estimation of the remaining life of the structural material.

[0008] JP-A-61-139743, JP-A-62-245960, JP-A-63-292959
JP, JP-A-1-248049, JP-A-63-1988
In the inventions disclosed in JP-A-292059, JP-A-5-288706, and JP-A-5-504203, the shape of the surface or planar damage can be detected, but the depth information is difficult to measure. In the prior art, the state in the depth direction is predicted from the surface state of the damage, but the damage may have a complicated shape depending on the object. Three-dimensional analysis of damage is necessary for accurate remaining life evaluation. In the invention disclosed in Japanese Patent Application Laid-Open No. Hei 2-213764, application to a magnetic material is easy to detect a change in magnetism, but application to other materials is difficult. No mention is made of cracks and corrosion marks.

In the above-mentioned known example, it is difficult to detect a minute defect in an opening which cannot be detected by a penetrant test or the like, or to measure in a depth direction. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a method for detecting minute damage of a non-magnetic material and further detecting the depth of the damage.

[0010]

In order to achieve the above object, a damage detection method according to the first invention of the present application is to apply a magnetic powder to a surface of a non-magnetic object to be measured and to apply a magnetic powder to the surface of the object to be measured. In the method for detecting a defect, a magnetic powder is applied to the surface of a measured object, and the applied magnetic material powder is wiped or in a state of being applied, and a magnetic field or a high-frequency current is applied to the measured object to apply the magnetic powder. Magnetizing the magnetic recording medium, bonding the magnetic recording medium to the surface of the object to be measured in a plurality of layers, recording the leakage magnetic flux disturbed by the defect on the surface of the object to be measured, and evaluating the planar shape and depth of the defect on the surface of the object to be measured. It is characterized by.

[0011] A damage detection method according to a second aspect of the present invention is a method for detecting a defect on the surface of a measured object by applying a magnetic powder to the surface of a non-magnetic measured object. The body powder is applied, and the applied magnetic body powder is wiped off or in a state of being applied, a magnetic field or a high-frequency current is applied to the measured object to magnetize the magnetic body powder, and using a single-layer magnetic recording medium. It is characterized by detecting the planar shape of the leakage magnetic flux disturbed by the defect on the surface of the measured object, and evaluating the depth of the defect on the surface of the measured object by scanning the magnetoelectric conversion element in the vicinity of the detected defect. And

[0012] A damage detection method according to a third invention of the present application is characterized in that the magnetic recording medium according to the first or second invention is a magnetic recording tape or a magnetic recording film.

[0013] A damage detection method according to a fourth invention of the present application is characterized in that the magnetic recording medium according to the third invention is configured by mixing a magnetic material powder with a thermosetting resin or an ultraviolet hard resin. Features.

In a fifth aspect of the present invention, the damage detection method according to the second aspect is characterized in that the magnetoelectric conversion element is one of a Hall element, a magnetic diode, a magnetoresistance element, and a superconducting quantum interference element. And

According to a sixth aspect of the present invention, there is provided the damage detection method according to any one of the first to fifth aspects, wherein a tensile stress is applied to the surface of the measured object before or after the magnetic powder is applied to the surface of the measured object. It is characterized in that it causes elastic deformation and enlarges a minute opening of a defective portion.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a leakage magnetic flux near a crack. When the crack 2 exists on the surface of the measured object 1, the leakage magnetic flux 3 tends to increase around the crack so as to surround the crack. Using this characteristic, crack detection and crack dimension measurement are performed. In a method of applying a magnetic field for generating the leakage magnetic flux 3, a method of directly generating a magnetic field with a coil or the like and applying a magnetic field to the DUT 1 or
There is a method in which a high-frequency current is caused to flow through the DUT 1 and a leakage magnetic flux 3 is generated from disturbance of the current around the crack 2. The former has a feature that the magnetic field is constant in the thickness direction, whereas the latter has a feature that propagation is slow inside the thickness and fast on the surface.

FIG. 2 shows this state. Therefore, the method of applying a magnetic field directly is suitable for evaluating defects that have reached the inside, and the method of applying a magnetic field using high-frequency current is suitable for measuring small cracks near the surface. ing.

FIG. 3 shows an example in which the leakage magnetic flux 3 is measured using the magnetoelectric conversion element 4. The surface direction of the DUT 1 is defined as an x direction,
Assuming that the vertical direction is the z direction, the leakage magnetic flux 3 is represented by a combination of a normal component 5 and a tangential component 6. In actuality, when used for damage detection of a structure, evaluation is performed using the normal component 5.

Next, the influence of the shape of the defect on the leakage magnetic flux is shown in FIGS. 4 shows the relationship between the magnetic flux density and the distance of the detector from the surface, FIG. 5 shows the relationship between the magnetic flux density and the defect depth, and FIG. 6 shows the relationship between the magnetic flux density and the defect length. From FIG. 4, if the distance between the electromagnetic transducer 4 and the DUT 1 is kept constant,
The magnetic flux density changes according to the defect depth. FIG. 5 shows that when the defect depth is constant and the defect length is different, the magnetic flux density changes according to the defect length. From these results, it is impossible to determine whether the magnetic flux density measured by the magnetoelectric conversion element 4 depends on the length of the defect or the depth. FIG. 6 shows the relationship between the magnetic flux density and the aspect ratio. The aspect ratio is the ratio of a / c when the defect length is 2a and the defect depth is c. It can be seen that the magnetic flux density has a one-to-one correspondence with the aspect ratio. Therefore, the defect aspect ratio can be obtained from the measured magnetic flux density, and the defect depth and defect length can be evaluated from the aspect ratio.

When the DUT 1 is a ferromagnetic material, the above-mentioned phenomena are easily observed by applying a magnetic field to the DUT 1, and a technique using these is established as a magnetic particle flaw detection test. Technology. On the other hand, the present invention detects damage to a material other than a ferromagnetic material as a measured object.

FIG. 7 is a flowchart showing an example of the detection procedure according to the present invention. In the case of a defect of a closed type or a crack having a small opening, even if the magnetic powder is applied to the surface of the measurement object, the magnetic powder does not penetrate into the inside of the defect. FIGS. 8 and 9 are schematic diagrams of a solution to this problem.

FIG. 8 shows an object to be measured of the object 1 to be elastically deformed in a direction in which a crack of the object 1 is opened when the end of the object 1 is released in terms of stress. The heated magnetic powder 7 flows on the surface of the sample, and the cooling water 8 flows on the opposite side of the object to be measured. A thermal stress is generated in the DUT 1 due to a temperature difference between the surface and the inner surface, and a tensile stress is generated on the surface and a compressive stress is generated on the inner surface. The crack 2 is temporarily opened by the tensile stress on the surface of the measured object 1. The magnetic powder flows into the opening. After pouring the magnetic powder, the magnetic fluid 7 and the cooling liquid 8 whose surfaces are heated are removed to remove stress. Excess magnetic powder 7 adhering to the surface of the DUT 1 is removed with alcohol or the like.

FIG. 9 shows that, in place of the thermal stress shown in FIG. 8, a tensile stress is generated on the surface of the DUT 1 by applying a mechanical deformation such as a bending elastic deformation in which both ends of the DUT are clamped and bent. The crack is temporarily opened, and the magnetic powder 9 is poured. After pouring the magnetic powder 9, the stress is removed,
Return to the original shape. Thereafter, excess magnetic substance powder 9 is removed with alcohol or the like.

As a method of mechanically elastically deforming the object 1 to be measured, there is an elastic deformation due to magnetostriction and the like in addition to the above-mentioned tool. When the end of the measured object is constrained by stress, the surface of the measured object is cooled and the back surface on the opposite side is heated in a manner opposite to the method of FIG. And a defect is temporarily opened.

Next, when a magnetic field is applied to the DUT 1 on which the magnetic powder is applied as described above, the magnetic powder penetrating the crack 2 is magnetized.
The leakage magnetic flux 3 shown in FIG.

The method of detecting the leakage magnetic flux 3 generated as described above is mainly classified into three methods: a method using the magnetoelectric conversion element 10, a method using the magnetic recording medium 11, and a method using the current detector 12. .

Representative examples of the magnetoelectric conversion element 10 include a Hall element, a magnetic diode, an electric resistance element, and a superconducting quantum interference element. FIG. 10 shows an example of the result of measurement using the magnetoelectric conversion element. Assume that the measured object 1 has a corrosion pit 13, a crack 2, and a general corrosion mark 14 on the surface. Magnetoelectric conversion element 1 along the surface shape of DUT 1
By scanning 0, a leakage magnetic flux 3 as shown in FIG. 3 is measured. Based on the measured leakage magnetic flux, the aspect ratio is obtained from FIG. 6, and the defect length and the defect depth are obtained from FIGS. FIGS. 11 to 13 show examples of the measurement results of the corrosion pit 13, the crack 2, and the overall corrosion trace 14 in FIG. FIG.
1. As shown in FIG. 13, the open defects such as the corrosion pit 13 and the entire surface corrosion mark 14 have weak adhesion of the magnetic powder 9 and partly fall off when the extra magnetic powder 9 is washed. Therefore, it is difficult to evaluate the detailed shape of the bottom of the defect,
It is possible to measure the aspect ratio required for fracture mechanics evaluation and the maximum corrosion depth required for electrochemical evaluation. On the other hand, crack 2 of the closed defect shown in FIG.
Means that the magnetic substance powder 9 penetrates into the inside by capillary action,
In addition, since it is not removed by cleaning, it is possible to evaluate a defect shape in more detail than an opened defect.

Automatic measuring device 20 using magnetoelectric transducer 10
14 is shown in FIG. The automatic measuring instrument is connected to the fixture 1 via a universal joint 28 for fixing the measuring instrument itself to the DUT 1 and can move vertically with respect to the DUT 1. Z-axis guide 22
And the guide shaft is composed of guide portions 22a and 22b which are brought into contact with and separated from each other by a nut rotated by a motor 29. The measuring device 20 is vertically connected to the Z-axis guide 22 and is fixed in parallel with the measured object 1.
And a Y-axis guide 23 that can move in parallel in one direction, and is fixed to the Y-axis guide 23 so as to be perpendicular to the Y-axis guide 23 and parallel to the measured object 1. An X-axis guide 24 that can move in one direction parallel to the object 1 to be measured, and a horizontal moving device 2 that can move on the X-axis guide 24 in parallel to the surface 1 to be measured.
5 and the horizontal moving device 25,
Element 10 capable of measuring the leakage magnetic flux of
A cable 26 for controlling the automatic measuring device 20 or transferring a measurement result or the automatic measuring device 20 via the cable 26
And a control device 27 for storing and processing the control or measurement results.

An X-axis guide 24, a Y-axis guide 23, and a Z-axis guide 22 are provided. Becomes possible. Also, the fixing jig 21
By attaching a ball type slide 28 whose angle can be changed freely between the Z-axis guide 22 and the Z-axis guide 22, a displacement gauge 29 is attached to the Z-axis guide 22, so that a T-shaped joint or a three-dimensional It becomes possible to detect a defect such as a wing having a complicated shape. In addition, the Z-axis movement motor 29, the Y-axis movement motor 30, and the X-axis movement motor 31 are attached and controlled by the control device 27 to enable automatic measurement. The result of measuring the leakage magnetic flux 3 of the DUT 1 using the magnetoelectric conversion element 10 stores the position of the DUT 1 and the intensity of the leakage magnetic flux 3 at that position. The detection by the magneto-electric conversion element is performed as described above, but in this detection method, in order to reliably detect the presence or absence of a defect, the magneto-electric conversion element is scanned along the surface of the measured object with a narrow scanning path interval. There is a need.

Therefore, in the present invention, the leakage magnetic flux is basically measured using a magnetic recording medium. FIG. 15 shows a flow of a detection method using a magnetic recording medium such as a magnetic recording tape or a magnetic film. The magnetic recording medium is denoted by reference numeral 41 in FIG.
In FIG. 17, this is indicated by reference numeral 42, and in FIG. Since the tape or film, which is a magnetic recording medium, can only record the leakage magnetic flux 3 in a two-dimensional manner, that is, in a two-dimensional manner, it is possible to evaluate the presence or absence and size of a defect on the surface, but in the depth direction, that is, three-dimensionally Can not.

For the evaluation in the depth direction, in the present invention, the magnetic recording medium is stacked in several layers and the information in each layer is superimposed to measure in the depth direction. Instead of overlapping, as shown in FIG. 18, a method is used in which the magneto-electric conversion element 10 and the magnetic recording medium 11 are used together. In this combined method, the defect size of the surface of the measured object 1 is reduced from the magnetic recording medium 11. Direct measurement is performed, the intensity of the leakage magnetic flux 3 is measured from the magnetoelectric conversion element 10, and the depth of the defect is measured.

When measuring the magnetic recording medium alone, the types of the magnetic recording medium include a magnetic recording tape such as a magnetic recording tape and a curable film. The magnetic recording tape is a technique that can easily measure a magnetic field when a strong leakage magnetic flux is generated, but recording is difficult in a weak leakage magnetic field. On the other hand, the curable film increases the sensitivity by facilitating the movement of the magnetic powder by mixing the magnetic powder into a thermosetting solvent, for example, and measures the magnetic field on the surface of the DUT 1. Thereafter, by applying heat or ultraviolet light as it is, the solvent is cured to form a film, and the magnetic powder in the solvent is fixed to enable high-sensitivity detection, but the measurement requires more labor than magnetic recording tape. . A major feature of the magnetic recording medium is that the distribution of the leakage magnetic flux 3 of the DUT 1 can be preserved as it is.

FIG. 16 shows a measurement example when the magnetic recording tape 41 is used as the magnetic recording medium. After applying the magnetic powder 9 to the DUT 1, excess magnetic powder 9 is removed with alcohol or the like as necessary. Assuming that a crack 2 and a corrosion pit 40 having a crack exist on the surface of the DUT 1, the magnetic field is disturbed around these defects. A magnetic recording tape 41 is adhered thereon, and the same magnetic recording tape 41 is further laminated on the previously adhered magnetic recording tape 41 in order to measure in the depth direction. After leaving for a certain period of time, the magnetic recording tape 41 is removed, and the leakage magnetic flux 3 recorded on the magnetic recording tape 41 is read into a processing device such as a personal computer.

FIG. 17 shows a measurement example when the curable film 43 is used. A curable solvent 42 is provided on the surface of the DUT 1
And the magnetic powder 9 are mixed and applied. In order to measure the distribution of the leakage magnetic flux 3 in the depth direction, the curable film 43 is used.
Is applied in a sufficient thickness. After applying the curable film 43, a curing agent, for example, heat, ultraviolet light or the like is applied to cure the curable film 43. After curing, the curable film 43 is removed, and the magnetic flux leakage 3 recorded on the curable film 43 is read. As described above, the planar shape and the depth of the leakage magnetic flux can be known from the recording result of the leakage magnetic flux detected by laminating the magnetic tape or the film on the measured object.

FIG. 18 shows a measurement example in the case where the leakage magnetic flux 3 is measured in a combined manner by combining the magnetic recording medium 11 and the magnetoelectric conversion element 10. By adhering the magnetic recording tape 41 or the magnetic hardening type film 43 and recording the leakage magnetic flux on these magnetic recording media, the planar distribution of the leakage magnetic flux can be known. Then, in order to know the depth of the defect, the intensity of the leakage magnetic flux 3 is measured by scanning the magnetoelectric conversion element 10 near the distribution of the leakage magnetic flux of the measured object. After the measurement of the leakage magnetic flux 3 by the magnetoelectric conversion element 10, the magnetic recording tape 4
1 or the curable film 43 is removed and the magnetic recording tape 4
1 or the magnetic flux leakage 3 recorded on the curable film 43 is read and stored.

FIG. 19 shows a measurement example of the magnetic field distribution. What is recorded on the magnetic recording tape 41 or the curable film 43 is a leakage magnetic flux, and the leakage magnetic flux 3 appears in a direction perpendicular to the magnetic field 44. In the case of the magnetic recording tape 41, information on the laminated magnetic recording tapes 41 is stacked, and in the case of the curable film 43, defects are identified from the distribution and strength of the leakage magnetic flux 3. The leakage magnetic flux pattern corresponding to the defect shape is simulated by electromagnetic field analysis, or a database of the measurement results is used to identify the pattern on the surface of the magnetic recording tape 41 or the curable film 43, and the depth direction of the defect is determined. It will be possible to obtain information.

FIGS. 20 and 21 show examples of an automatic measuring device 50 for performing automatic measurement using the magnetic recording medium 11 without adhering the magnetic recording medium to the object to be measured as described above. FIG. 20 is a side view of the automatic measuring device 50, and FIG.
0 is a front view. The automatic measuring device 50 is an automatic measuring device 50.
Supplies a roller 51 for moving the device under test 1, a driving motor 52 for driving the roller 51, a magnetic field applying device 53 for applying a magnetic field to the device 1 to be measured, and a current to the magnetic field applying device 53 , A spray nozzle 55 for applying the magnetic powder 9, a tank 56 for storing the magnetic powder 9, a magnetic recording medium 11 for measuring leakage magnetic flux, and a magnetic recording medium 11. A supply roll 57 to be supplied, a take-up roll 57 for winding the supplied magnetic recording medium 11, a pressure roll 59 for pressing the magnetic recording medium 11 against the sample 1 to be measured, and a magnetic field applying device 5
3 to eliminate the influence of the magnetic field from
And a magnetic shielding plate 60 attached to the magnetic recording medium 11 side. By having the moving roller 51, it is possible to move the surface of the plate-shaped material 1 to be measured. Also,
A rail is attached to the object to be measured, and the moving roller 51 moves on the rail, thereby enabling movement on a curved surface or the like. Further, by attaching the drive device control antenna 61 to the drive motor 52, remote control becomes possible. In addition, the magnetic recording medium 11 is attached to the supply roll 57 and wound up by the take-up roll 58, whereby continuous measurement following the moving roller 51 becomes possible. Further, by heating the roller on the winding side of the pressure roll 59, it becomes possible to use a thermosetting magnetic recording film.

Next, an example of measuring the current induced by the leakage magnetic flux due to the defect using the current detector 12 is shown in FIG.
Shown in As a typical example of the current detector 12, the current detector 12 including a coil 70 and an ammeter 71 is considered. When the coil 70 is brought closer to the leakage magnetic flux 3 generated near the crack 2,
The current induced by the leakage magnetic flux 3 flows through the coil 70. The amount of current is detected by the ammeter 71, and the defect on the DUT 1 is evaluated. FIG. 23 shows an example of a result of measuring a defect using the current detector 12.

By mounting the current detector 12 instead of the magneto-electric transducer 10 of the automatic measuring device 20 using the magneto-electric transducer described above, automatic measurement becomes possible.

[0040]

As described above, according to the present invention,
By measuring the leakage magnetic flux generated around the defect as a defect of the structural material, it is possible to three-dimensionally evaluate the presence or absence of the defect and its shape.

[Brief description of the drawings]

FIG. 1 is a schematic view of a leakage magnetic flux in the vicinity of a crack of a measured object.

FIG. 2 is a schematic diagram of a magnetic field distribution in a thickness direction of an object to be measured.

FIG. 3 is a diagram showing an example of measurement of leakage magnetic flux in the vicinity of a crack of an object to be measured.

FIG. 4 is a graph showing a relationship between a magnetic flux density and a distance between a surface and a detector.

FIG. 5 is a graph showing a relationship between a magnetic flux density and a defect depth.

FIG. 6 is a graph showing a relationship between a magnetic flux density and an aspect ratio.

FIG. 7 is a flowchart showing one embodiment of a damage detection method according to the present invention.

FIG. 8 is a view showing an example of a method for applying a magnetic substance powder in the first embodiment according to the present invention.

FIG. 9 is a view showing another example of the method of applying a magnetic substance powder in the first embodiment according to the present invention.

FIG. 10 is a diagram showing a measurement example of a defect of a measured object by a magnetoelectric conversion element.

FIG. 11 is a diagram showing an example of measuring corrosion pits of a measurement object by using a magnetoelectric conversion element.

FIG. 12 is a diagram showing an example of measuring a crack of a measured object by a magnetoelectric conversion element.

FIG. 13 is a diagram showing an example of measuring the entire surface corrosion mark of a measured object by using a magnetoelectric conversion element.

FIG. 14 is a diagram showing an embodiment of a damage detection device using a magnetoelectric conversion element.

FIG. 15 is a diagram showing a leakage magnetic flux measurement flow using a magnetic recording medium according to the present invention.

FIG. 16 is a diagram showing an example of a leakage magnetic flux measurement using a magnetic recording tape as the magnetic recording medium.

FIG. 17 is a diagram showing an example of leakage magnetic flux measurement using a curable film as the magnetic recording medium.

FIG. 18 is a diagram showing an example of leakage magnetic flux measurement in which a magnetic recording medium and a magnetoelectric conversion element are combined according to the present invention.

FIG. 19 is a diagram showing an example of a measurement result using a magnetic recording medium.

FIG. 20 is a side view of an embodiment of a damage detection device using a magnetic recording medium according to the present invention.

FIG. 21 is a front view of one embodiment of a damage detection device using a magnetic recording medium according to the present invention.

FIG. 22 is a diagram showing another embodiment of the damage detection device of the present invention.

FIG. 23 is a diagram showing an example of a measurement result obtained by a current detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Measurement object 2 ... Crack 3 ... Leakage magnetic flux 4 ... Magnetoelectric conversion element 5 ... Normal component of leak magnetic flux 6 ... Tangential component of leak magnetic flux 7 ... Heat magnetic powder 8 ... Cooling water 9 ... Magnetic powder 10 ... Magnetoelectric conversion element 11 ... Magnetic recording medium 12 ... Current detector 13 ... Corrosion pit 14 ... Corrosion mark 20 ... Automatic measuring device using magnetoelectric conversion element 21 ... Fixing jig 22 ... Z axis guide 23 ... Y axis guide 24 ... X-axis guide 25 Horizontal movement device 26 Cable 27 Control device 28 Ball type slide 29 Displacement meter 30 Z-axis movement motor 31 Y-axis movement motor 30 X-axis movement motor 40 Crack Corrosion pit 41: Magnetic recording tape 42: Curable medium 43: Curable film 44: Magnetic field 50: Automatic measuring device using magnetic recording medium 51: Moving roller 52: Driving motor 53: Magnetic field application Location 54 ... Battery 55 ... spray nozzles 56 ... magnetic savings tank 57 ... supply roll 58 ... take-up roll 59 ... crimping rolls 60 ... magnetic shielding plate 61 ... drive control antenna 70 ... coil 71 ... ammeter

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masahiro Otaka 502 Kandachicho, Tsuchiura-shi, Ibaraki Pref.

Claims (6)

[Claims] 1. A method for detecting a defect on a surface of a measured object by applying a magnetic powder to a surface of a non-magnetic measured object,
A magnetic powder is applied to the surface of the measured object, and a magnetic field or a high-frequency current is applied to the measured object to wipe the applied magnetic material powder or leave the applied magnetic powder, and the magnetic material is magnetized, A plurality of layers on the surface of the object to be measured, recording the leakage magnetic flux disturbed by the defect on the surface of the object to be measured, and evaluating the planar shape and depth of the defect on the surface of the object to be measured. . 2. A method for detecting a defect on a surface of a measured object by applying a magnetic substance powder to a surface of a non-magnetic measured object,
A magnetic substance powder is applied to the surface of the object to be measured, and the applied magnetic substance powder is wiped off or in a state of being applied, a magnetic field or a high-frequency current is applied to the object to be magnetized to magnetize the magnetic substance powder, thereby forming one layer. The depth of the defect on the surface of the object to be measured is detected by detecting the planar shape of the leakage magnetic flux disturbed by the defect on the surface of the object to be measured using a magnetic recording medium, and scanning the vicinity of the detected defect with a magnetoelectric transducer. A damage detection method characterized by evaluating the following. 3. The damage detection method according to claim 1, wherein the magnetic recording medium is a magnetic recording tape or a magnetic recording film. 4. The damage detection method according to claim 3, wherein the magnetic recording medium is formed by mixing a magnetic material powder with a thermosetting resin or an ultraviolet hard resin. 5. The damage detection method according to claim 2, wherein said magnetoelectric conversion element is any one of a Hall element, a magnetic diode, a magnetoresistance element, and a superconducting quantum interference element. 6. Before or after the application of the magnetic substance powder to the surface of the measured object, a tensile stress is generated on the surface of the measured object to cause elastic deformation, thereby enlarging a minute opening of a defective portion. The damage detection method according to any one of claims 1 to 5, wherein: