JPH1026562A - Detecting method for stress using superconducting quantum interference device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detecting method in which a stress applied to an object to be inspected can be detected by a method wherein the object to be inspected is not magnetized so as to be moved relatively to a SQUID sensor and a change in the DC magnetic-force characteristic of the object to be inspected is measured. SOLUTION: A tensile stress is applied to the length direction (the first direction) of an object 1 to be inspected, and the object 1 is arranged on a stage 2 without being magnetized. After that, an arm part 7a at an X-Y recorder 7 is moved, the stage 2 is pulled to the first direction by using a weight 21, the object 1 to be inspected is moved relatively to a sensor 3 using a SQUID 5, and the distribution of a DC magnetic force is measured. Then, the object 1 to be inspected is turned by 90 deg. each around the first direction, and a scanning operation is performed in the same manner. After that, the value of the stress to be applied to the length direction of the object 1 to be inspected is changed, and a measurement is performed in the same manner at 90 deg. each. Then, an obtained DC magnetic force is referred to a magnetic field-to-stress conversion table, and the stress applied to the object 1 to be inspected is measured. Thereby, the fatigue and the falw of the object 1 to be inspected can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress detection method using a sensor using a superconducting quantum interference device generally called a SQUID.

[0002]

2. Description of the Related Art Conventional superconducting quantum interference devices (SQUI)
Non-destructive inspection methods using D) include, for example, JP-A-7-7
After magnetically magnetizing the inspection object disclosed in 7516, the sensor is scanned at a set distance from the inspection object, and a change in magnetic force of the inspection object is measured, whereby fatigue or defect of the inspection object is measured. There was a method to detect such.

[0003]

In a nondestructive inspection method using a sensor using a superconducting quantum interference device (SQUID) as described above, a method of inspecting a test object after magnetizing the test object is generally employed. However, when the inspection object is magnetized in this way, the sensor detects the DC magnetic field due to the magnetization, and the signal due to the fatigue or defect of the inspection object is compared with the background signal due to the DC magnetic field due to the magnetization. Therefore, there is a problem that it is difficult to detect a signal caused by fatigue or a defect. In particular, if a sensor using a superconducting quantum interference device (SQUID) is used to measure a DC magnetic field of an inspection target to detect a stress such as a residual stress applied to the inspection target,
This magnetic field is extinguished when magnetized, and there is a problem that it is very difficult or impossible to detect when the stress applied to the inspection object is particularly smaller than the yield stress. For the same reason, it was difficult to determine whether or not a stress higher than the yield stress was applied to the inspection target portion.

[0004]

In order to solve the above-mentioned problems, in the stress detecting method using the superconducting quantum interference device 5 according to the present invention, the inspection object 1 is arranged in a measurement area, and the inspection object 1 By scanning the sensor of the superconducting quantum interference device relative to the test object along a predetermined first direction defined in the test object 1 without magnetizing, the direct current of the test object is First to measure magnetic force characteristics
The measurement is performed, and the stress in the first direction applied to the inspection object is detected based on the result of the first measurement.

As described above, since the DC magnetic force characteristics are measured without magnetizing the inspection object, the measurement can be performed without disturbing the original magnetic force characteristics of the inspection object. Furthermore,
Since a large magnetic field is not applied to the object to be inspected, it is possible to detect even a relatively weak signal based on a change in physical properties due to the applied stress.
Thereby, even if the stress applied to the inspection object is relatively small, it can be detected. That is, it is possible to detect even weak fatigue and defects at an earlier stage, which has been impossible so far.

Further, as in a preferred embodiment of the present invention,
The test object performs a second measurement relative to the sensor relative to the sensor by a set angle around the first direction and performs the first measurement at each of a plurality of set rotation measurement positions, and at least 45 degrees or more. The stress in the first direction may be detected by obtaining a DC magnetic force characteristic distribution of the inspection object at the plurality of set rotation measurement positions having the rotation phase relationship. By performing such a second measurement, the magnetic field of the inspection object represented by the three-dimensional vector quantity can be measured in more detail. In a preferred embodiment, the stress applied to the object can be measured based on at least the measurement result of the first measurement and a prepared magnetic field stress conversion table. That is, under the set conditions, if the magnetic field of the test object corresponding to the stress applied in advance is measured, under the same conditions, if the DC magnetic force characteristic can be measured, the stress applied to the test object is measured. be able to.

Further, as disclosed in a preferred embodiment of the present invention, a change in the direction of the magnetic moment of the test object is measured based on at least the measurement result of the first and second measurements. This makes it possible to determine that the stress exceeds the yield stress value. In the present invention, as one example of a method of determining whether or not the stress applied to the inspection object exceeds the yield stress value, there is the following determination method. That is, a first direction magnetic moment amount, which is the first direction magnetic moment amount, is estimated from at least the DC magnetic force characteristic distribution in the first measurement, and the first direction magnetic moment amount is dominant. It is determined that the stress value at which the magnetic force characteristic distribution is substantially a sine function exceeds the yield stress value. Another example of determining the yield stress value is as follows. That is, a stress value at which a difference equal to or more than a predetermined value is not recognized between the DC magnetic force characteristic distributions between the DC magnetic force characteristic distributions measured for each of the plurality of set rotation measurement values having a different rotation phase and a different rotation phase. The yield stress value is used. Other features and advantages of the present invention will become apparent in the following description of the embodiments with reference to the drawings.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a method for detecting a stress using a superconducting quantum interference device (SQUID) according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a non-destructive inspection device for implementing a stress detection method according to the present invention. An apparatus for performing a nondestructive inspection according to the present invention generally includes a stage 2 on which an inspection object 1 is mounted, a sensor system A including a SQUID 5, and an XY recording the magnetic field detected by the sensor system A. It has a recorder 7. The sensor system A includes SQUID 5, its peripheral circuit 6,
The sensor 3 is magnetically connected to the ID 5.

Next, each part of the nondestructive inspection apparatus will be described in detail. In the present invention, any object to be inspected 1 can be an object to be inspected as long as it is a material that is slightly magnetized. In the present embodiment, the inspection object uses stainless steel. The inspection object 1 is arranged on the stage 2 without passing through the magnetizing process. Further, any of the steps in the present invention does not include the magnetizing step.

[0010] The stage 2 on which the object to be inspected is mounted is preferably made of a non-magnetic material such as wood or resin. The shape of the stage 2 is a rectangle having an upper surface 2a which is a plane on which the inspection object is placed. Further, the stage 2 is provided with four wheels 2b so as to be able to move along the direction defined by X in FIG. Also,
One end of the stage 2 is connected to a cable 9 via a pulley 20.
It is connected to the weight 21 by b. The other end of stage 2
It is connected to the arm 7a of the XY recorder 7 by a cable 9a. Although not shown, it is preferable to provide straight rail grooves for the four wheels.

Next, the sensor system A having the SQUID 5 will be described. In this specification, the SQUID indicates a portion surrounded by a broken line 5 in FIG. The SQUID 5 is magnetically coupled to the sensor 3, and the cryostat 4 houses the SQUID 5, the sensor 3, and the peripheral circuit 6 of the SQUID 5. The cryostat 4 is fixed to the floor by a support (not shown). As described above, in the present embodiment, the inspection target 1 is configured to move relative to the fixed sensor 3, but the sensor 3 is configured to move relative to the fixed inspection target 1. It is also possible to configure.

The sensor 3 has a pickup coil 3 at the bottom.
a magnetic flux transformer having a pickup coil 3
The shape of a may be what is generally called a secondary gradiometer as shown in FIG.
A planar gradiometer as shown in FIG.
In the secondary gradiometer of FIG. 3A, four loops are formed, and as shown in the figure, the current in the two loops flows in the opposite direction to the current flowing in the other two loops. And the top loop and the middle 2
The interval between two loops and the interval between the bottom loop and the two loops in the middle are h. The sensor 3 having any form has directionality and detects an element in this direction of the magnetic field. In this specification, this direction is called a sensing direction, and is a direction perpendicular to the plane including the loop. Although the sensor 3 is housed in the cryostat 4 in the present embodiment, it may be a superconductor or a normal conductor. Further, the pickup coil 3a may be configured to extend outside the cryostat. On the opposite side of the pickup coil 3a,
An input coil 3b is provided at a portion facing the ID5, and the input coil 3b is magnetically connected to the SQUID5.

Next, SQUID 5 will be described with reference to FIG. The input coil 3b described above is located adjacent to a superconducting loop 5a having two Josephson coupling portions 5b. The peripheral circuit 6 of the SQUID 5 has a battery 6a, a potentiometer 6b for adjusting the voltage of the battery 6a, a transformer 6c, and a capacitor 6d, and further includes an amplifier 6e, a phase detector 6f, a transmitter 6g, and a modulation feedback coil 6h. Provided. That is, a linearization circuit is connected to the SQUID 5, and a periodic output having a cycle of the magnetic flux quantum outputted from the superconducting loop 5a is converted into a simple increasing output by the linearization circuit.
The output value from the output port 6i is transmitted to the X-
It is sent to the Y recorder 7.

The XY recorder 7 is preferably arranged at a distance from the sensor system A so that the electromagnetic field from a motor or the like incorporated in the XY recorder 7 has little effect on the sensor 3. The Y axis of the XY recorder 7 corresponds to the detected magnetic force, and the X axis is the pickup coil 3a.
Corresponding to the inspection object 1. The XY recorder 7 is provided with an arm 7a movable in the X-axis direction, and one end of the stage 2 is mechanically connected to the arm 7a via a cable 9a. Since the stage 2 is urged by the weight 21 in the X-axis direction, the X-
When the arm 7a of the Y recorder 7 moves in the X-axis direction,
The stage 2 is pulled by the cable 9b and moves by the same distance. By directly and mechanically connecting the XY recorder 7 and the stage 2 in this manner, the stage 2
There is no need to provide a stepping motor, a potentiometer, or the like to move the device in a state where the position of the inspection target can be recognized. The fact that there is no need to equip the stage 2 with a motor means that the SQ is very sensitive to noise.
This is important in using UIDs. Further, in this configuration, the displacement of the recording paper in the X-axis direction is the relative displacement between the actual inspection object and the pickup coil 3a, and there is an advantage that the inspection result can be easily interpreted.

Next, the stress detecting method according to the present invention will be described. First, a predetermined tensile stress is applied to the inspection object 1. The values of stress actually performed in the experiment will be described later as experimental results. In this embodiment, the inspection object 1 has a rectangular shape and a longitudinal direction is defined. This longitudinal direction is called a first direction, and a tensile stress is applied along the longitudinal direction. Next, the inspection object 1 is arranged on the stage 2 without magnetizing the inspection object 1. Thereafter, the weight 21 pulls the stage 2 by moving the arm 7 a of the XY recorder 7, and the inspection object 1 moves with respect to the sensor 3. At this time, the inspection object 1 is arranged on the stage 2 so that the sensor 3 moves along the longitudinal direction of the inspection object 1, that is, along the first direction. Is desirable.
The sensing direction of the pickup coil 3a of the sensor 3 is oriented so as to extend in a direction perpendicular to the upper surface 2a of the stage 2. In this manner, data obtained by scanning the sensor 3 once in the longitudinal direction of the inspection object 1 is sent to the XY recorder 7 via the wire 8 and is recorded as needed. The above measurement process is called first measurement. The vertical axis indicates the sensor output corresponding to the DC magnetic force obtained in this way, and the horizontal axis indicates the position of the sensor 3 with respect to the inspection object.

Next, the stage 2 and the inspection object 1 are returned to the initial position with respect to the sensor 3 by returning the arm 7a of the XY recorder 7 to the initial position. Inspection object 1
Is rotated 90 degrees around the first direction, and the sensor 3 is moved again with respect to the inspection object 1. Thus, the process of rotating the inspection object relative to the sensor by the set angle and measuring the DC magnetic force distribution is referred to as a second measurement. The inspection object 1 is further rotated by 90 degrees around the first direction, and the same scanning is performed. The inspection object 1 is further rotated by 90 degrees around the first direction, and the same scanning is performed. Next, the same measurement was performed by changing the value of the stress applied in the longitudinal direction of the inspection object 1 to 9 times.
Perform every 0 degrees. Here, the inspection object 1 is rotated by 90 degrees to perform a plurality of measurements, but it is important that the component of the magnetic field, which is a vector quantity, be detected. This goal can be achieved. The DC magnetic force characteristic distribution corresponding to each tensile stress value obtained in this way is recorded and used later as a magnetic field stress conversion table. That is, the inspection object 1 and the sensor 3 will be described later.
If the conditions such as the interval, generally called lift-off, are the same, the stress applied to this can be estimated by measuring the magnetic field of the inspection object later.

As will be apparent from the experimental results described later, there is a change in the DC magnetic force characteristic distribution in accordance with the magnitude of the stress applied to the inspection object. That is, when the stress applied to the inspection object is zero, the magnetic field is very weak and substantially zero. When a weak stress equal to or lower than the yield stress is applied, a magnetic moment is generated in a direction perpendicular to the first direction, which is the longitudinal direction, and the amount of the magnetic moment in this direction is dominant. However, when a stress exceeding the yield stress is applied, the amount of magnetic moment in the direction of the stress, for example, the first direction becomes dominant. If the amount of magnetic moment in the direction perpendicular to the first direction is dominant, for example, FIG.
As shown by the DC magnetic force characteristic distribution in (b), the sensor output has a maximum value near the center of the inspection object.
When the stress is further increased from this stress, the maximum value becomes smaller and gradually changes to a DC magnetic force characteristic distribution of a substantially sine function represented by FIG. As described above, the amount of magnetic moment in the first direction is dominant in the stress in which a substantially sinusoidal DC magnetic force characteristic distribution having a peak in the region near both ends of the inspection object is obtained. Therefore, in order to measure the yield stress of the test object by using the DC magnetic force, the stress on the test object is increased, and the longitudinal direction is the direction in which the stress is applied from the region where the magnetic moment perpendicular to the longitudinal direction is dominant. This can be done by measuring the transition region when transitioning to the region where the magnetic moment along the longitudinal direction is dominant.

That is, a test object having the same magnetic characteristics as the test object used in the experiment according to the present invention is provided, and as a result of measuring the direct current magnetic force characteristic distribution, it is found that the test object has a characteristic along the stressed direction. Observing that the magnetic moment is dominant indicates that the test object has been subjected to a stress higher than the yield stress. Conversely, if it is observed that the magnetic moment in the direction perpendicular to the direction in which the stress is applied is dominant, it is presumed that the test object has been subjected to a stress equal to or lower than the yield stress. Further, another method for measuring the yield stress will be described. As can be understood by comparing FIG. 5A with FIG. 5E, in addition to the fact that the DC magnetic force characteristic distribution differs depending on the stress,
It can be seen that the difference in the magnetic force characteristic distribution at different angles decreases as the stress increases. That is, FIG.
In (b), the magnetic force characteristic distribution at 0 degree and 18
The difference in the magnetic force characteristic distribution at 0 degrees or the interval between the two curves is very large, but this width is relatively small in FIG. 5C and very small in FIG. 5E. The stress value at which a difference equal to or more than a predetermined value is not recognized between the DC magnetic force characteristic distributions measured at a plurality of set rotation measurement positions having a maximum rotation phase difference of 90 degrees is referred to as a yield stress value. It is possible to judge. In addition, as will become clear from the experimental results described later, since the amount of martensite precipitation increases with applied stress above a certain tensile stress, the amount of martensite precipitation is estimated by measuring DC magnetic force characteristics. It is possible.

Next, a description will be given of an experiment conducted using the above-described stress detection method and the results thereof. In this experiment, stainless steel SUS304 (JIS standard) was used. Table 1 shows the chemical composition of SUS304.

[0020]

[Table 1]

SUS304 is converted to JIS-Z2201 (19
80) A No. 4 test piece was processed based on the “metallic material tensile test piece”. This No. 4 test piece has cylindrical symmetry, and the processed shape is shown in FIG. The values of L1 and L2 shown in FIG. 4 are 180 mm and 60 mm, respectively, the values of R1 and R2 are 20 mm and 14 mm, respectively, and R3 is 15 m
m or more. The tensile test of the material was performed using a tensile tester (not shown) according to JIS Z2241 (199).
3) The test was performed based on the “metallic material tensile test method”. The tensile stress was changed in the range of 0.6 to 61.8 kg / mm ² . After the tensile test, a parallel portion was cut out using a wheel made of SiC and used as an inspection object. At the time of measurement, the sample was cut while spraying cooling water on the sample to prevent heat. Also,
Ultrasonic cleaning was performed in acetone for 30 minutes to remove impurities on the surface.

A tensile stress shown in Table 2 was applied to the above No. 4 test piece.

[0023]

[Table 2]

A SQUID sensor obtained as a result of moving the SUQUID sensor 3 along the first direction B, which is a longitudinal direction, relative to the test object 1 obtained by cutting out a parallel portion from the test piece. The output from the system is shown in FIG. The vertical axis in FIG. 5 indicates the detected magnetic force, and the horizontal axis indicates the position of the sensor 3 with respect to the inspection target 1.
As shown in FIG. 5, the outputs shown in FIGS. 5A to 5E have tensile stresses of 0 kg / mm ² and 3.2 K, respectively.
g / mm ² , 35 kg / mm ² , 47.8 kg / mm ² ,
It corresponds to 61.8 kg / mm ² . “A” and “b” shown in FIG. 5 indicate positions corresponding to both ends of the inspection object. Also, for example, FIG. 5B shows four curves, which are used to move the inspection object in the longitudinal direction (first direction).
It is the curve obtained as a result of measuring the direct current magnetism after rotating 90 degrees around.

The tensile test shown in FIG. 5A is not performed.
(0Kg / mm^Two) Substantially the sensor output for the inspection object
No change was observed. The tension response shown in FIG.
Force (3.2Kg / mm^TwoThe sensor output corresponding to
The largest convex output curve was shown at the center of the inspection object.
Further, as shown in FIG.
Rotate the inspection object at 90 degree intervals
At the 90 and 270 degrees, the sensor output
The force could hardly be measured. 180 degrees to this
In the position, an output curve completely opposite to the 0 degree position was obtained. Obedience
Therefore, in the inspection object used in this experiment,
Estimate that the perpendicular magnetic moment is dominant
It is. Magnetic moment perpendicular to this longitudinal direction
Is 5.0 × 10^-Tenwb · mm. Follow
Therefore, the difference between the magnetic force characteristic distributions of 0 degrees and 180 degrees is about 1.
0x10^-9wb · mm. Further increase tensile stress
Then, as shown in FIG. 5C, the size of the convex portion in the middle portion is large.
The size becomes smaller. As explained below,
Stress (35Kg / mm ^Two) Is the yield stress
The magnetic characteristic of 0 degree at this time.
The difference between the cloth and the magnetic property distribution at 180 degrees is shown in FIG.
3.2 kg / mm^TwoCompare with the difference when
It is about 30%.

When the stress is further increased, as shown in FIG. 5 (e), the absolute value of the output takes the maximum value in the region near the end of the test object, and the absolute value of the output takes the minimum value in the central portion. Was. Also, it can be seen that the directions of the magnetic moments are opposite at both ends of the inspection target portion. Therefore, in the test object used in this experiment, when the stress is large, it is presumed that the magnetic moment parallel to the longitudinal direction which is the stress applying direction is dominant. The maximum value of the magnetic moment parallel to the longitudinal direction was 4.6 × 10 ⁻¹⁰ wb · mm. The curve obtained by simulating the sensor output value when it is assumed that a magnetic moment perpendicular to the longitudinal direction exists in the inspection object using Coulomb's law and the curve obtained in FIG. It was confirmed that the curves obtained corresponded very accurately. Also, the curve obtained by simulating the sensor output value when it is assumed that a magnetic moment parallel to the longitudinal direction of the test object exists and the curve obtained in FIG. It was confirmed that. Therefore, the magnetic moment when no stress is applied is zero, and when a stress equal to or lower than the yield stress is applied, a magnetic moment is generated in a direction perpendicular to the direction in which the stress is applied, and the applied stress is It is considered that the vertical component of the magnetic moment becomes smaller and the component in the direction in which the stress is applied becomes larger as the value is increased, and when the stress exceeds the yield stress, the magnetic moment in the vertical direction becomes dominant.

In general, as a method for detecting the yield stress of a test piece, there is a method in which the test piece is pulled at a constant strain rate, and the stress at this time is recorded to judge from the shape of a tensile stress curve obtained. . In the tensile stress curve obtained by pulling the test piece of SUS304 having the above shape at a constant strain rate, a linear portion corresponding to an elastically deformed portion and a deformation curve portion corresponding to a plastically deformed portion were detected. The stress that changes from elastic deformation to plastic deformation is generally defined as yield stress. When the yield stress is measured by this method, the yield stress of the test piece used is about 35 kg / mm ^2.
Met. Summarizing these observations, the following can be said. (1) In the sample before the tensile test, the sensor output could not be measured. (2) When the sample was pulled with a stress of 3.2 kg / mm ² , a magnetic moment was generated in the direction perpendicular to the longitudinal direction, which is the direction in which the stress was applied. (3) As the tensile stress increases, the sensor output, which is considered to be caused by a magnetic moment perpendicular to the longitudinal direction, which is the direction in which the stress is applied, decreases. (4) When the tensile stress exceeds the yield stress, a magnetic moment in a direction parallel to the stress application direction is generated instead of a magnetic moment in a direction perpendicular to the stress application direction. (5) As the tensile stress further increased, the sensor output considered to be caused by the magnetic moment in the direction parallel to the longitudinal direction as the stress applying direction increased. Therefore, the direction of the magnetic moment changed around the vicinity of the yield stress, and it was speculated that this might suggest that the SUS304 material has a different magnetic field generation mechanism between the elastic deformation region and the plastic deformation region.

Therefore, a change in the crystal structure corresponding to the magnitude of the tensile stress of the material was examined. When the amount of martensite precipitation was measured by an X-point analyzer, it was observed that the amount of martensite precipitation increased with an increase in tensile stress when the amount of martensite precipitation exceeded a certain tensile stress. If described in further detail, about 4% in the sample of tensile stress 52.2 kg / mm ^2, it was measured also tensile samples approximately 13% martensite precipitation amount of stress 61.8Kg · mm ^2. At a stress lower than this, the amount of martensite precipitation was below the detection limit (about 1%), and measurement was not possible. Therefore, in the SUS304 material, it is considered that a permanent strain is generated from the yield stress replacing the elastic deformation region to the plastic deformation region, and at the same time, a phase transfer from the austenite phase to the martensite phase occurs. In the present embodiment, the DC magnetic force was measured by applying a tensile stress to the sample. The characteristics change, and by measuring the DC magnetic field without going through the process of magnetizing the test object, it becomes possible to measure changes in magnetic characteristics that could not be measured by the conventional technology. .

[Another Embodiment] In the above embodiment, the SKU
Although the ID having a method of being driven by a DC current generally called dcSQUID was transferred to the ID, it is possible to detect the DC magnetic field of the inspection object even if the Josephson junction is called rfSQUID using one AC current. Therefore, this may be used.

In the first embodiment, the SUS3
Although the 04 sample was processed into a sample having cylindrical symmetry, and a parallel portion was cut out to obtain an inspection object, the figure inspection object may be in a shape having cylindrical symmetry. This is arranged in the measurement area, and without passing through the process of magnetizing, the SUQUID sensor is moved relative to the inspection object in the axial direction and the circumferential direction of the inspection object, thereby making the DC of the inspection object small. Magnetic force characteristics may be measured, and the stress applied to the inspection object may be detected based on the result of the measurement.

[Brief description of the drawings]

FIG. 1 is a schematic view of a non-destructive inspection device used in the present invention.

FIG. 2 is a block diagram of a circuit showing a SQUID and peripheral circuits;

FIG. 3 is a perspective view showing a pickup coil portion of the sensor system.

FIG. 4 is a plan view showing a processed shape of a test piece.

FIG. 5 is a graph showing the output from the SQUID of the stress detection method according to the present invention when the tensile stress is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection object 2 Non-magnetizable stage 3 Sensor 4 Cryostat 5 SQUID 6 SQUID peripheral circuit 7 XY recorder 20 Pulley 21 Weight

Claims (7)

[Claims] An object to be inspected is arranged in a measurement area, and a sensor of a superconducting quantum interference device is arranged along a first direction defined in the object without magnetizing the object to be inspected. Performing a first measurement to measure a DC magnetic characteristic distribution of the inspection object by scanning relatively to the inspection object, and performing the first measurement added to the inspection object based on a result of the first measurement. A stress detection method using a superconducting quantum interference device that detects stress in one direction. 2. The test object according to claim 1,
Performing a second measurement relative to the first direction by a set angle and performing the first measurement at each of a plurality of set rotation measurement positions, wherein the plurality of set rotations having a rotation phase relationship of at least 45 degrees or more; 2. The stress in the first direction is obtained by obtaining a DC magnetic force characteristic distribution of the inspection object at a measurement position.
Of stress detection using superconducting quantum interference device according to the method. 3. At least a measurement result of the first measurement,
2. A stress detecting method using a superconducting quantum interference device according to claim 1, wherein the stress applied to the object is measured based on a magnetic field stress conversion table prepared in advance. 4. A method for detecting that the stress value exceeds a yield stress value by measuring a change in a direction of a magnetic moment of a test object at a plurality of stress values based on at least the measurement result of the first measurement. A stress detection method using the superconducting quantum interference device according to claim 1. 5. A first direction magnetic moment amount, which is the first direction magnetic moment amount, is estimated from at least the DC magnetic force characteristic distribution in the first measurement, and the first direction magnetic moment amount is dominant. 5. The stress detection method using a superconducting quantum interference device according to claim 1, wherein it is determined that the stress value at which the DC magnetic characteristic distribution is substantially a sine function exceeds the yield stress value. 6. A difference of a predetermined value or more between the DC magnetic force characteristic distributions between the DC magnetic force characteristic distributions measured for each of the plurality of set rotation measurement values having different rotation phases by a set angle or more is not recognized. 3. The method for detecting stress using a superconducting quantum interference device according to claim 2, wherein the stress value exceeds the yield stress value. 7. An inspection object having a cylindrical symmetry in which an axial direction and a circumferential direction perpendicular to the axial direction are defined, is arranged in a measurement region, and the inspection object is not magnetized without magnetizing the inspection object. The DC magnetic force characteristic of the test object is measured by moving the sensor of the superconducting interference element relative to the test object in the axial direction and the circumferential direction of the object, and the test object is based on the measurement result. A stress detection method using a superconducting quantum interference device that detects a stress applied to a substrate.