JP2001174440A - Method and apparatus for diagnosing defect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for statically, non-destructively, simply, accurately diagnosing a defect or the remaining life of a work made of a magnetic material or a material made magnetic by working or by a magnetic material exposed, covered with a nonmagnetic material or embedded in the nonmagnetic material by using a magnetic sensor. SOLUTION: A method for obtaining an isomagnetic diagram comprises the steps of giving an external magnetic field to a work 20 made of a magnetic material exposed or covered with a nonmagnetic material or made magnetic by working, stopping the giving of the magnetic field, moving the magnetic sensor 10 along the surface of the work 20 in a state in which the field remains applied while the remains magnetism exists in the work 20, detecting the magnetic flux density of the work, and image analyzing the obtained detection signal. The method for diagnosing the fault of the work 20 comprises the step of diagnosing the fault from the diagram. An apparatus for obtaining the diagram image analyzes the magnetic flux density of the work. The apparatus for diagnosing the defect of the work 20 compares the obtained diagram with a previously stored reference isomagnetic diagram and diagnoses the defect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor that detects a magnetic field by utilizing a current magnetic field effect or an electromagnetic induction effect, and is covered with an exposed or nonmagnetic material or embedded in a nonmagnetic material. Defects of a workpiece made of a magnetic material or a material that becomes magnetic by processing,
Defects that detect and determine the degree of plastic deformation, the degree of fatigue, the degree of remaining life, etc. while an external magnetic field is applied by a coil or the like while the remanence exists or while the external magnetic field is applied. The present invention relates to a diagnostic method and an apparatus therefor.

[0002]

2. Description of the Related Art Non-destructive inspection techniques for metal materials currently being implemented or devised include techniques using ultrasonic waves or radiation, eddy currents, and the like simply as a technique for simply knowing the state of crack occurrence and its position. A method using a response such as a potential difference, magnetic hysteresis, or Barkhausen noise is generally known. Taking the fatigue fracture of metal materials as an example,
It is the initial microstructural change, the occurrence of microcracks,
It progresses in four steps: crack propagation and final fracture. Of these, the crack length is a factor that determines the degree of propagation, and the fracture toughness value of the material is a factor that determines the fracture. , Data has been relatively accumulated up to now, and the above-mentioned technique is also applied to crack detection at this stage,
However, there is no clear data on the factors that determine the process up to the occurrence of microcracks, and there are few techniques for quantitatively determining the occurrence of cracks.

As one of the few diagnostic techniques, SQ
Japanese Patent Application Laid-Open No. Hei 7-120558 has proposed a UID (superconducting quantum interference device, which detects a minute magnetic field using the Josephson effect occurring near absolute zero). JP-A-7-1
No. 20558, “Method of searching for a reinforcing bar using a SQUID sensor” discloses a technique relating to a method and an apparatus for measuring the position and depth of a reinforcing bar located deep in concrete using a SQUID sensor. This is a method to detect the presence or position of plasticization by detecting a small magnetic field caused by magnetic anisotropy induced by plastic deformation.However, it is necessary to cool the sensor to near absolute zero to bring it into a superconducting state. is there.

[0004]

This prior art has the following problems. a, In measurement by this technology, liquid helium is indispensable as a refrigerant in order to keep the sensor at extremely low temperature in principle,
Since the coolant and the heat insulating material are interposed between the sensor and the surface of the magnetic material, the distance between them must be at least about 6 mm. It is widely known that the magnetic flux density is inversely proportional to the cube of the distance from the magnetic moment, and the resolution of a micro magnetic sensor is significantly affected by the distance between the sensor and the magnetic material. Cannot be fully demonstrated. b. The magnetic field of the magnetic material is composed of a fine magnetic domain structure, and the longest length of these magnetic domains is several μm to several tens μm. At present, the SQUID sensor has a size of 1 mm in diameter and a very large magneto-sensitive area. At present, there is a limit to the accuracy of the present method, considering that the closer the magnetosensitive area is to the size of the magnetic domain structure, the higher the resolution and the higher the reliability.

C) Since a special refrigerant is used, the size of the apparatus is increased, and the diagnostic work is also restricted accordingly. There is also a problem of cost push by using expensive refrigerant. Since the diagnosis is performed repeatedly at extremely low temperature and normal temperature, an expensive sensor is deteriorated and damaged by thermal fatigue, requiring frequent replacement of the sensor, which is uneconomical. d. Liquid helium used as a refrigerant is a finite resource and the area where it can be collected is limited. It is not preferable from the viewpoint of environmental protection to consume such resources for diagnosis. e, Conventional technology for determining plasticization of other steel materials As a conventional technology for determining plasticity of steel materials, a method of observing dislocations and slip lines accompanying plasticization by observing the structure of steel materials and an oxidation treatment of the steel surface ( (Etching) and visually observing the strain effect area. For this purpose, it is necessary to take a sample from a steel material and polish the surface, and in the case of observation by etching, it is necessary to perform oxidation treatment with a corrosive liquid. Therefore, it can be applied to diagnosis of small test pieces in a laboratory or the like, but is difficult to apply to large structures.

It is an object of the present invention to overcome the problems of the prior art,
To solve, defects in the magnetic material or the material that becomes magnetic by processing (exposed on the surface of the magnetic material or the material that becomes magnetic by processing) that are exposed or covered by or embedded in the nonmagnetic material It is an object of the present invention to provide a method and an apparatus for diagnosing cracks, scratches, etc. statically, nondestructively, easily, safely and with high accuracy.

[0007]

The present invention to achieve the above object is as follows. (1) An external magnetic field is applied to a workpiece made of a magnetic material or a material which becomes magnetic by processing, which is exposed or covered with a non-magnetic material or embedded in the non-magnetic material, and the application of the external magnetic field is stopped. While the residual magnetism is present in the work, or in a state where the external magnetic field is applied, a magnetic sensor that detects a magnetic field using a current magnetic field effect or an electromagnetic induction action is moved along the surface of the work. Detecting the magnetic flux density of the work at a predetermined pitch by the magnetic sensor, and inputting the output of the magnetic sensor to a computer, and the computer performs two-dimensional or three-dimensional shading or multiplication of the magnetic flux density of the work. A defect diagnosis method, comprising: a step of preparing a magnetic isomagnetic line for generating color magnetic lines. (2) The defect diagnosis method according to (1), further including a determining step of determining whether there is a defect in the workpiece from the isomagnetic diagram. (3) a step of preparing a reference isomagnetic map in advance using at least a work having no defect and storing the map in a database;
The defect diagnosis method according to (2), wherein in the determining step, the presence or absence of a defect in the workpiece is determined by comparing the isomagnetic diagram with the reference isomagnetic diagram. (4) the magnetic sensor is a semiconductor magnetic sensor;
(1) The defect diagnosis method according to (1). (5) The defect diagnosis method according to (4), wherein the semiconductor magnetic sensor is a Hall effect element. (6) A magnetic sensor that detects a magnetic field using a current magnetic field effect or an electromagnetic induction effect, and a magnetic material that is exposed or coated with a non-magnetic material or embedded in a non-magnetic material. Applying an external magnetic field to a work made of a borne material, an external magnetic field generating device for stopping the application, a driving device for moving the magnetic sensor along the surface of the work, and connected to the magnetic sensor,
A computer installed with an isomagnetic diagram creation program for creating two-dimensional or three-dimensional shading or multicolored isomagnetic lines of the magnetic flux density of the workpiece from the output of the magnetic flux density of the workpiece at a predetermined pitch detected by the magnetic sensor. And a defect diagnosis device comprising: (7) The computer has a determination program for comparing the isomagnetic diagram with at least a reference isomagnetic diagram created in advance using a work having no defect to determine whether there is a defect in the work. Is further installed,
(6) The defect diagnosis apparatus described in (6). (8) the magnetic sensor is a semiconductor magnetic sensor;
(6) The defect diagnosis apparatus according to (1). (9) The defect diagnosis device according to (8), wherein the semiconductor magnetic sensor is a Hall effect element.

[0008] In a magnetic material, when there is no defect, the magnetic flux density of the small magnetic domain is small, the direction is irregular, and the magnetic flux density becomes 0 when it is summed. At the time of occurrence, a directionality occurs in the direction of the magnetic flux density of the minute magnetic domain around the defect, and the magnetic flux density locally increases. Therefore, by detecting the magnetic flux density, the presence or absence of the defect can be determined. For a material that becomes magnetic due to processing, the non-magnetic structure (eg, austenite) is transformed into a magnetic structure (eg, martensite) by external stress such as fatigue and processing, so that the portion becomes magnetic. Diagnosis is possible by using the phenomenon of carrying. This phenomenon can also be used for the diagnosis of magnetic materials or materials that are magnetic by processing, which are coated with or embedded in a non-magnetic material. When the workpiece is placed in an external magnetic field, the magnetic flux density is disturbed at a defect with plastic strain such as a crack, and even if the application of the external magnetic field is stopped, the magnetic flux density remains disturbed as long as the remanence exists. ing. The strength of the magnetic flux density is much larger than the strength of the magnetic flux density detected at the defective portion when no external magnetic field is applied. Therefore, by measuring the remanence of the external magnetic field and its distribution with a magnetic sensor,
Defects can be detected and diagnosed more easily than when no external magnetic field is used.

In the above-mentioned method (1), an external magnetic field is applied to a workpiece made of a magnetic material or a material which becomes magnetic by processing, which is exposed or covered with a non-magnetic material or embedded in the non-magnetic material. A magnetic sensor that detects the magnetic flux density or the residual magnetic flux density after the application is stopped using a current magnetic field effect or an electromagnetic induction effect,
The workpiece is moved in a non-contact manner and detected, and the obtained detection signal is input to a computer. By creating isomagnetic maps of the work from the input, non-contact, non-destructive, simple, safe, and accurate grasp of the state of the work without adding X-rays, ultrasonic waves, currents, etc. to the work I do. In the above method (2), X-rays, ultrasonic waves,
A non-contact, non-destructive, simple, safe and accurate determination of the state of a work without applying a current or the like to the work.

In the method (3), an isomagnetic diagram of the work is created, and the isomagnetic diagram is compared with a reference isomagnetic diagram created and stored in advance to determine whether there is any defect in the work. , The presence / absence of a defect in the work can be determined easily, safely and accurately without contact, non-destruction, and without applying X-rays, ultrasonic waves, electric current, etc. to the work. In the methods (4) and (5), the semiconductor magnetic sensor (Hall effect element) is detected by moving the workpiece in a non-contact manner with the work, and an isomagnetic diagram of the work is created from the obtained detection signal. When a Hall effect element is used as a semiconductor magnetic sensor, the magnetically sensitive area is extremely small,
Since it is almost the same size as the magnetic domain of the magnetic material of the work or the material that is magnetized by processing, the accuracy is extremely high, non-contact and non-destructive without applying X-ray, ultrasonic wave, current etc. to the work, Grasp the state of the work easily and safely.

[0011] In the apparatus of the above (6), an external magnetic field is applied to a workpiece made of a magnetic material or a material which becomes magnetic by processing, which is exposed or covered with a non-magnetic material or embedded in the non-magnetic material. The magnetic flux density or the residual magnetic flux density after the application is stopped is detected by moving the magnetic sensor that detects the magnetic field using the current magnetic field effect or the electromagnetic induction action to the workpiece in a non-contact manner. Create an isomagnetic map of. By creating an isomagnetic map of the work from the input, the state of the work can be accurately, non-contactly, non-destructively, easily, safely and accurately added to the work without applying X-rays, ultrasonic waves, currents, etc. Figure out. In the apparatus of the above (7), X-rays, ultrasonic waves, electric current, etc. are applied to the work by comparing the isomagnetic map with the reference isomagnetic map prepared in advance to determine whether there is a defect in the work. Non-contact, non-destructive, simple, safe and accurate determination of work defects without adding.

In the above devices (8) and (9), when the Hall effect element is used as the semiconductor magnetic sensor, the magnetically sensitive area is extremely small, and is almost the same as the magnetic domain of a magnetic material of a work or a material which is magnetized by processing. Because of the size,
The accuracy of the work is extremely high, and the state of the work is grasped simply and safely without contact and non-destruction without applying X-rays, ultrasonic waves, electric current, etc. to the work.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the magnitude of the magnetic flux density of a work defect when no external magnetic field is applied is 10 ^-1 to 1.
0 is about ² G, the magnitude of the magnetic flux density remaining in defects near when stopping the application of subsequent external magnetic field is applied an external magnetic field is about 3 × 10 ² G. Magnetic sensors that can detect a magnetic field of that magnitude with high accuracy include a magnetic sensor that detects a magnetic field using the "current magnetic field effect" and a magnetic sensor that detects a magnetic field using "electromagnetic induction". is there. Magnetic sensors that detect a magnetic field using the “current magneto-electric field effect” include a Hall effect element and a magnetoresistive element (MRE element). The element material of the Hall effect element is a compound semiconductor (eg, InAs, InSb, GaAs).
s, GaSb, etc.). In the MRE element, a compound semiconductor (eg, InSb, GaAs) is used as an element material.
) And a ferromagnetic metal (eg, Ni
-Fe, Ni-Co, etc.). Among them, MRE using Hall effect element and compound semiconductor
The element is a semiconductor magnetic sensor. Magnetic sensors that detect a magnetic field using the “electromagnetic induction effect” include a magnetic-impedance effect sensor (MI sensor) that detects a magnetic field using the “magnetic-impedance effect” and a “magnetic-inductance effect”. There is a flux gate sensor that detects a magnetic field using the flux gate sensor. The element material of the MI sensor is an amorphous magnetic material (FeCoSiB, FeCoB, CoS
iB).

Of the above magnetic sensors, the Hall effect element, the MRE sensor, and the MI sensor are particularly suitable for use in the present invention because they can cope with the size of a minute work magnetic domain in detection. The details of the magnetic field detection of the Hall effect element will be described later, but when an external magnetic field acts on the element when current is flowing through the element, electrons move in a direction orthogonal to the current flow due to Lorentz force and accumulate at the end of the element. This is performed by detecting the charge as a voltage. A total of four terminals are required, two terminals for energization and two terminals for voltage detection. The magnetic field of the MRE sensor is detected by measuring a change in the inclination angle of the magnetization vector (current flowing direction) due to the magnetic field as a change in the resistance value and measuring the voltage. Two terminals are required for voltage detection. In the magnetic field detection of the MI sensor, a skin effect appears when a high-frequency current is directly applied to the soft magnetic material, and the resistance R, the inductance L, and the impedance Z are changed by the external magnetic field H. This is performed by grasping as a frequency change. Hereinafter, a semiconductor magnetic sensor, particularly a Hall effect element will be described as an example of the magnetic sensor. However, the magnetic sensor used in the present invention is not limited to the Hall effect element,
A sensor or MI sensor may be used.

Next, the principle of detecting the magnetic flux density of the semiconductor magnetic sensor used in the present invention will be described with reference to FIGS. The Hall effect element as a semiconductor magnetic sensor is a compound semiconductor having a general appearance as shown in FIG. 2 and made of, for example, In, Ga, As, and is a sensor that detects an external magnetic field with high accuracy using the Hall effect. The magnetic sensing area is extremely small, about 50 μm × 50 μm, and almost coincides with the size of magnetic domains of a magnetic material or a material which is magnetically formed by processing. Therefore, the magnetic flux density of each magnetic domain can be directly observed, and the error is very small. High-precision diagnosis is possible. The magnetic field to be diagnosed is as small as 0.0001 T or less, but the sensitivity of the Hall effect element is 33.9.
It is excellent in mV / T (300K), and can detect to a nanovolt unit through a high-precision digital voltmeter.

A thin plate-like conductor (width a, thickness t) as shown in FIG. 3 is placed vertically in a uniform magnetic field of magnetic flux density B, and x
The current I flows in the direction. The charge carrying the current is, for example, an electron (N
Type), the electrons move in the −x direction, assuming that no electrons enter or exit from the y direction. For an electron moving at velocity v, the Lorentz force F =
(−ev) × B acts in the −y direction, electrons accumulate at the conductor end in the −y direction, positive charges accumulate at the conductor end in the y direction, and an electric field E _y = E in the y direction between the conductor ends. _H (<0) occurs.
In the steady state, the electrons move only in the −x direction, and the force due to the magnetic flux density B due to the electric field E _H is balanced, so that E _H = vB. On the other hand, between the current density i and the electron velocity v, i = −ne
Since there is a relation of v, I = iS = −nevS. Since the cross-sectional area of the conductor plate is S = at, E _H = − (IB) / (neS) <0. Therefore, the potential generated by the Hall effect (Hall voltage)
V _{H is, V H = -E H a =} (IB) / (net)> 0. This potential is detected by a sensor.

FIGS. 1 and 10 schematically show a defect diagnosis apparatus according to an embodiment of the present invention. In the figure, reference numeral 10 denotes a magnetic sensor (for example, a semiconductor magnetic sensor) that detects a magnetic field using a current magnetic field effect or an electromagnetic induction effect, and more specifically,
For example, a Hall effect element shown in FIG. 2 is shown. In the figure, reference numeral 20 denotes a work (which may be a welded part of the work) made of a nonmagnetic material or a magnetic material by processing. Reference numerals 30a and 30b denote driving devices (for example, servo motors) that move the magnetic sensor 10 along the surface of the work 20. The driving device is a magnetic sensor 10
In order to move the magnetic sensor 10 three-dimensionally, a motor that moves the magnetic sensor 10 in a direction orthogonal to the work surface may be provided. A DC power supply 80 supplies a direct current to the motor. Reference numeral 90 denotes a Helmholtz coil as an external magnetic field generator for forming a magnetic field.

In the defect diagnosis method according to the embodiment of the present invention, a work 20 made of a magnetic material or a material which becomes magnetic by processing, which is exposed or coated with a non-magnetic material or embedded in a non-magnetic material, is inspected by a defect diagnosis apparatus. 1 and a magnetic field is applied by the coil 90.
To stop the application of the magnetic field by turning off the current to the workpiece 20
While the residual magnetism is present, the magnetic sensor 10 (for example, a semiconductor Hall sensor) is detected along the surface of the workpiece 20 in a non-contact manner to detect the magnetic field.
0a, 30b to automatically move and scan, and at each measurement point (a large number of points located at intervals of, for example, about 50 μm on the scanning line), the work (magnetic material or material that becomes magnetic by processing) at that position. The magnetic flux density is detected by the magnetic sensor 10 and output as a potential difference (Hall voltage). It is measured by a digital voltmeter 60, input to a computer 70, calibrated in advance, and
Is converted into a magnetic flux density from the VB (voltage-magnetic flux density) calibration curve of the Hall effect element stored in the magnetic field. At the same time, the outputs of the encoders provided in the motors of the driving devices 30a and 30b are input to the computer as the coordinates of the diagnostic position-magnetic flux density (X, Y, B). The processing up to this point is performed by the computer 70.

The data of the coordinates of the diagnosis position and the magnetic flux density are developed into a matrix (see FIG. 7) by image analysis software input to the computer 70 in advance, and an isomagnetic diagram of the work is created. (Figure 6
reference). The diagnosis is performed by scanning the magnetic sensor 10 shown in FIG. 1 with the motors 30a and 30b at a preset pitch (for example, about 50 μm) in a preset range for each work 20. In a state where the work 20 is set vertically to the ground, for example, as shown in FIGS.
From the start point in the vertical and horizontal directions to the horizontal movement motor 30a in the horizontal direction until the magnetic flux density is detected at each of the pitch-separated measurement points until the end point (end point) in the horizontal direction is reached. When it reaches the end (end point) in the horizontal direction, it returns to the other end (start point). At this time, it is moved vertically by one pitch by the vertical movement motor 30b.
This operation is repeated up to the vertical end point of the diagnosis range of the work to scan the work surface. The sensor output obtained by the scanning is input to the computer 70, and an isomagnetic diagram is created.

A workpiece 20 made of a magnetic material or a material which becomes magnetic by processing, which is exposed or coated with or embedded in a non-magnetic material.
In addition, if there is a micro-crack or a micro-crack occurs, the isomagnetic lines due to the residual magnetism around the micro-cracks become denser than other parts, or the equi-magnetic line interval becomes dense (the gradient becomes large). The crack site can be easily grasped on the isomagnetic diagram. The presence or absence of cracks, the size, by comparing the isomagnetic map obtained in this way with a reference isomagnetic map prepared in advance and stored without a defect visually or on a computer,
By determining the degree of progress, the remaining life of the work to be diagnosed can be predicted. For the actual structural material, prepare the reference work in various states such as coating material, thickness, etc., about the unloaded state and the state where the load is applied step by step with the test machine, that is, the crack propagation process up to the fracture First, microscopic microstructural changes (microslip), microcracks, crack growth, and final fracture are collected from the isomagnetic maps at each stage, and the applied stress and the number of applied cycles are created as parameters.

The experimental results will be described below. The work 20 used in the experiment is a flat plate, and the shape is as shown in FIG. The material is stainless steel (SUS304), which is magnetized by processing. The work 20 is a base material 20
b (when the base material 20b is exposed) and a case where the base material 20b is coated with a coating material 20a that is a non-magnetic material.

The experiment was performed for the following three types (,,). SUS304 central arc sample tensile test A circular hole with a diameter of 5 mm is provided at the center of the width direction of a work with a width of 40 mm, (a) elongation percentage is 0%, (b) elongation percentage is 1.9%, (c)
A strain having an elongation rate of 10.12% and (d) an elongation rate of 15.6% is applied by tension, and in each state, a magnetic field is forcibly applied by the coil 90, and the application of the magnetic field is stopped.
Zero residual magnetism was measured. The results are shown in FIG. FIG.
As can be seen from the diagram, the hole constitutes a kind of defect, and the portion where the plastic strain is generated by tension (the portion inclined 45 ° around the center of the hole with respect to the tensile direction) has a portion where the residual magnetic flux density is large. It can be seen that the method is effective for detecting a defect in which plastic strain has occurred, and is also effective for detecting a defect in a material which becomes magnetic by processing. In the drawing, r is red, y is yellow, g is green, and b is blue.
lue) and p indicate purple. The same applies to FIG. 12 and FIG.

SUS304 Plane Bending Fatigue Test A work having a width of 25 mm is repeatedly subjected to plane bending with a stress σa = 280 MPa, and (a) before the fatigue test (number of repetitions =
0), (b) no painting after the occurrence of plane bending fatigue cracks, and (c) a state where the fatigue cracks have been painted, the coil 90 is forcibly applied with a magnetic field to apply the magnetic field. After stopping, the residual magnetism of the work 20 was measured. The result is shown in FIG. As can be seen from FIG. 12, a portion where the residual magnetic flux density is large is seen in the portion where the crack has occurred,
It can be seen that the method is effective for detecting cracks, and is also effective for detecting cracks in the base metal inside even if the coating is applied.

SUS304 Tensile Fatigue Test of Notched Both Ends 7.5 mm Depth, 5 mm Width on Both Sides of 30 mm Width Workpiece
Unpainted SUS3 with R-shaped notch
A tensile stress of σ _max = 280 MPa was repeatedly applied to the test piece No. 04, and the test piece was removed from the fatigue tester at (a) 0 cycles, (b) 20,000 cycles, (c) 60,000 cycles, and (d) 61,300 cycles. The apparatus was set in the apparatus, a magnetic field was forcibly applied by the coil 90, the application of the magnetic field was stopped, and the residual magnetism of the work 20 was measured. Figure 1 shows the results
3 is shown. As can be seen from FIG. 13, a crack was generated at the tip of the notch at 60000 cycles, and
It can be seen that the crack has developed in 0 cycle. In this way, it is possible to measure the generation and propagation of cracks.

The embodiment of the present invention has been described above. In the present invention, the material that is exposed or coated is not only a magnetic material, but also austenitic stainless steel or high Mn that is magnetic when processed.
It is also applicable to the diagnosis of deterioration of non-magnetic materials such as steel, the detection of work-induced martensitic transformation and the change of structure. INDUSTRIAL APPLICABILITY The diagnostic apparatus of the present invention can be applied to the determination of deterioration on-site (on-site) of a steel structure such as a bridge or a structural material having a load during operation (for example, a component of an operating manufacturing facility). The device in that case does not need to be the same as that of FIG. 1, and a basic configuration example includes a magnetic sensor (for example, a Hall effect element), a magnetic sensor driving device (motor), an external magnetic field generating device, and a computer. Applications of this technology include non-magnetic paint, plating, and CVD (chemical vapor deposition).
osition), reinforced fiber (magnetic metal) such as FRP, coated electric wire, reinforcing steel embedded in concrete, and the like.

[0026]

According to the method of the first aspect, an external magnetic field of a workpiece made of a magnetic material or a material which is magnetically processed by a process, which is exposed or coated with or embedded in a non-magnetic material, is formed. The applied magnetic flux density or the residual magnetic flux density after the application is stopped is detected in a non-contact manner with the work using a magnetic sensor that detects the magnetic field using the current magnetic field effect or electromagnetic induction, and the detected magnetic flux density is used. Can create magnetic diagrams. With this, X-ray,
It is possible to diagnose a defect state of a magnetic material in a non-contact, non-destructive, simple, safe, and accurate manner without adding ultrasonic waves, electric current, and the like. According to the method of claim 2, the isomagnetic map is created,
By diagnosing the presence or absence of defects in the work, X
It is possible to diagnose the presence or absence of a defect in a magnetic material simply, safely and accurately without contact, non-destruction, without adding wires, ultrasonic waves, electric current and the like.

According to the third aspect of the present invention, a contour map is prepared, and the contour map is compared with a reference contour map prepared in advance and stored in a database. By diagnosing the presence / absence, it is possible to diagnose the presence / absence of a defect in the magnetic material in a non-contact, non-destructive, simple, safe, and accurate manner without adding X-rays, ultrasonic waves, electric current, etc. to the work. Claim 4,
According to the method 5 described above, since the Hall effect element is used, the magnetically sensitive area is extremely small, and is almost the same size as the magnetic domain of the magnetic material of the work or the material which is magnetized by processing. Create diagrams. This makes it possible to easily and safely diagnose a defect state or the like of the work with high accuracy without applying X-rays, ultrasonic waves, electric current, etc. to the work without contact.

According to the apparatus of the sixth aspect, an external magnetic field is applied to a workpiece made of a magnetic material or a material which becomes magnetic by processing, which is exposed or coated with or embedded in a non-magnetic material. The magnetic flux density or the residual magnetic flux density after the application is stopped is detected by moving the magnetic sensor that detects the magnetic field using the current magnetic field effect or the electromagnetic induction action to the workpiece in a non-contact manner, and from the detected magnetic flux density of the workpiece. Can create magnetic diagrams. This makes it possible to diagnose a defect state or the like of the work in a non-contact, non-destructive, simple, safe, and highly accurate manner without applying X-rays, ultrasonic waves, electric current, etc. to the work. According to the apparatus of claim 7, by comparing the isomagnetic diagram with the reference isomagnetic diagram previously created and stored, X-rays, ultrasonic waves, currents, etc. are not added to the workpiece, Non-contact, non-destructive, simple, safe and extremely accurate diagnosis of work defects can be performed. According to the device of the eighth and ninth aspects, since the Hall effect element is used, the magneto-sensitive area is extremely small, and the size is almost the same as the magnetic domain of the magnetic material of the work or the material which is magnetized by processing. Can create high isomagnetic maps. This makes it possible to diagnose a defect state or the like of a work in a non-contact, non-destructive, simple, safe, and extremely accurate manner without applying X-rays, ultrasonic waves, electric current, and the like to the work. The present invention is more effective even when the coating material is intact, that is, when there is no problem in appearance, but when the internal magnetic material portion is cracked.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a defect diagnosis apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a Hall effect element.

FIG. 3 is a perspective view of a Hall effect element showing a Hall effect.

FIG. 4 is a side view showing a positional relationship between a Hall effect element and a work at the time of measurement.

FIG. 5 is a perspective view of the Hall effect element showing a movement of the Hall effect element at the time of measurement.

FIG. 6 is a schematic flowchart from the measurement to the creation of the isomagnetic diagram.

FIG. 7 is a schematic diagram of a recording state of a magnetic flux density and a measurement position in a computer.

FIG. 8 is a plan view showing a work used for measurement in the example.

FIG. 9 is a plan view of a work showing a measurement site of the work used in the example.

FIG. 10 is a sectional view of a measurement experiment apparatus according to the method of the present invention.

FIG. 11 is an isomagnetic diagram obtained in a measurement experiment of an example of the method of the present invention.

FIG. 12 is an isomagnetic diagram obtained in another measurement experiment of the method of the present invention.

FIG. 13 is an isomagnetic diagram obtained in still another measurement experiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Defect diagnosis apparatus 10 Magnetic sensor 20 Exposed or coated with non-magnetic material or embedded in non-magnetic material, magnetic material or material (work) which becomes magnetic by processing 20a Non-magnetic coating material 20b Magnetic material or Material that takes on magnetism by processing 30a Horizontal movement motor 30b Vertical movement motor 60 Digital voltmeter 70 Computer 80 DC power supply 90 Helmholtz coil (magnetic field applying means)

Continued on the front page F term (reference) 2G017 AA07 AC09 AD51 AD53 AD55 BA18 2G053 AA11 AA14 AB04 AB11 BA02 BB11 CA04 CA05 CB21 CB22 CB27

Claims (9)

[Claims] 1. An external magnetic field is applied to a work made of a magnetic material or a material which becomes magnetic by processing, which is exposed or covered with a non-magnetic material or embedded in a non-magnetic material. A magnetic sensor that detects a magnetic field along the surface of the work by using a current magnetic field effect or an electromagnetic induction action while the work is stopped and the residual magnetism is present on the work or while the external magnetic field is applied. And detecting the magnetic flux density of the work at a predetermined pitch by the magnetic sensor; and inputting the output of the magnetic sensor to a computer, and the computer performs two-dimensional or three-dimensional shading of the magnetic flux density of the work. Alternatively, a defect diagnosis method comprising: an isomagnetic diagram creating step of creating multicolored isomagnetic lines. 2. The defect diagnosis method according to claim 1, further comprising a determining step of determining whether or not the workpiece has a defect from the isomagnetic diagram. 3. A step of previously preparing a reference isomagnetic map using at least a work having no defect and storing it in a database, and comparing the isomagnetic map with the reference isomagnetic map in the determination step. The defect diagnosis method according to claim 2, wherein the presence or absence of a defect of the workpiece is determined by using the method. 4. The defect diagnosis method according to claim 1, wherein said magnetic sensor is a semiconductor magnetic sensor. 5. The defect diagnosis method according to claim 4, wherein said semiconductor magnetic sensor is a Hall effect element. 6. A magnetic sensor for detecting a magnetic field using a current magnetic field effect or an electromagnetic induction effect, and a magnetic material or a processing, which is exposed or coated with a non-magnetic material or embedded in a non-magnetic material. An external magnetic field generator that applies and stops application of an external magnetic field to a work made of a magnetic material, a driving device that moves the magnetic sensor along the surface of the work, and the magnetic sensor is connected to the magnetic sensor. A computer installed with a magnetic field diagram creating program for creating two-dimensional or three-dimensional shading or multicolored isomagnetic lines of the magnetic flux density of the work from the detected output of the magnetic flux density of the work at the predetermined pitch. Defect diagnosis device. 7. The computer determines whether there is a defect in the work by comparing the isomagnetic map with at least a reference isomagnetic map prepared in advance using a work having no defect. 7. The defect diagnosis apparatus according to claim 6, further comprising a determination program installed. 8. The defect diagnosis apparatus according to claim 6, wherein said magnetic sensor is a semiconductor magnetic sensor. 9. The defect diagnosis apparatus according to claim 8, wherein said semiconductor magnetic sensor is a Hall effect element.