Magnetostriction measuring device and magnetostriction measuring method

Abstract

A magnetostriction measurement device 100 for measuring magnetostriction of a steel plate 40 includes a measurement frame 16 on which the steel plate 40 to be subjected to magnetostriction measurement is placed. On a surface of the measurement frame 16 on which the steel plate 40 is placed, there is at least a portion where resistivity measured in accordance with JIS C2139-3-1: 2018 satisfies 10(1) 12(2) Ω⋅m or less.

Description

Magnetostriction measuring device and magnetostriction measuring method

[0001] The present invention relates to a magnetostriction measuring device and a magnetostriction measuring method.

[0002] Conventionally, there has been known a magnetostriction measuring device that measures the magnetostriction characteristics of a plate-shaped material by measuring the displacement of the other end of the plate-shaped material that is placed in an AC magnetic field and has one end fixed, and that has a substrate that comes into contact with the bottom surface of the plate-shaped material and is capable of vibrating in the direction in which the magnetostriction characteristics are measured (Patent Document 1).This magnetostriction measuring device is known to be able to reduce measurement errors due to friction between the plate-shaped material and the substrate.

[0003] Furthermore, with regard to a method for evaluating magnetostrictive members, it is known to adhere a strain gauge so that its longitudinal direction is parallel to the longitudinal direction of the magnetostrictive member and the <100> direction (Patent Document 2).

[0004] Patent No. 7295433 JP 2021-88471 A

[0005] However, the technology described in Patent Document 1 does not take into account the friction caused by static electricity between the plate-shaped material and the substrate when attempting to reduce measurement errors due to friction between the plate-shaped material and the substrate. This results in a problem of not being able to sufficiently reduce measurement errors. Furthermore, the current IEC standard for magnetostriction measurement (IEC 60404-17) mentions the flatness, friction-freeness, and cleanliness of the measurement frame. Specifically, it describes the use of grounding to suppress the effects of static electricity.

[0006] Similarly, the technique described in Patent Document 2 does not take into consideration the effect of static electricity on the measured magnetostriction value.

[0007] In view of the above problems, an object of the present disclosure is to provide a magnetostriction measurement device and a magnetostriction measurement method that are capable of suppressing measurement errors caused by static electricity.

[0008] The gist of the present disclosure is as follows.

[0009] (1) A measuring device for measuring magnetostriction of a steel plate, comprising: a mounting portion on which a steel plate to be measured for magnetostriction is mounted; and a resistivity measured in accordance with JIS C 2139-3-1:2018 on the surface of the mounting portion on which the steel plate is mounted is 10 １２ A magnetostriction measuring device in which there is at least a portion that satisfies Ω·m or less.

[0010] (2) A magnetostriction measuring device as described in (1) above, in which the resistivity ρ (Ω·m) of the surface of the mounting portion satisfies the following formula, where the measurement frequency of magnetostriction is f (Hz), the relative dielectric constant of the surface of the mounting portion is εr, and the dielectric constant of vacuum is ε0 (F / m).

[0011]

[0012] (3) The magnetostriction measuring device according to (1) or (2) above, wherein the mounting portion is grounded to a ground having a ground resistance of 1 MΩ or less.

[0013] (4) A magnetostriction measuring device described in any one of (1) to (3) above, wherein the mounting portion has a conductive coating formed on the surface of the mounting portion or a conductive sheet adhered to the surface.

[0014] (5) A method for measuring magnetostriction of a steel plate, wherein the resistivity measured in accordance with JIS C 2139-3-1:2018 on the surface of the mounting portion on which the steel plate is placed is 10 １２ A magnetostriction measurement method in which magnetostriction is measured so that there is at least a portion that satisfies Ω·m or less.

[0015] (6) The magnetostriction measurement method described in (5) above, wherein the resistivity ρ (Ω·m) of the surface of the mounting portion satisfies the following formula, where the measurement frequency of the magnetostriction is f (Hz), the relative dielectric constant of the surface of the mounting portion is εr, and the dielectric constant of vacuum is ε0 (F / m).

[0016]

[0017] (7) The magnetostriction measuring method according to (5) or (6) above, wherein the placing portion is grounded to earth having a ground resistance of 1 MΩ or less.

[0018] According to the present disclosure, a magnetostriction measurement device and a magnetostriction measurement method are provided that are capable of suppressing measurement errors caused by static electricity.

[0019] 1 is a schematic diagram showing a magnetostriction measurement device according to an embodiment of the present disclosure, and is a diagram showing an example in which a conductive coating or a conductive sheet is provided on the surface of a measurement frame.

[0020] Hereinafter, several embodiments according to the present disclosure will be described with reference to the drawings. However, these descriptions are intended to merely exemplify preferred embodiments of the present disclosure and are not intended to limit the present disclosure to such specific embodiments. In the following description, similar components will be designated by the same reference numerals.

[0021] 1 is a schematic diagram showing a magnetostriction measurement device 100 according to an embodiment of the present disclosure. The magnetostriction measurement device 100 includes a table 10, a support member 12, a yoke 14, a measurement frame 16, an excitation coil 18, a support member 20, an end stop 22, a support member 24, and a laser vibrometer 26.

[0022] 1 is referred to as the X direction, the up-down direction in Fig. 1 as the Z direction, and the direction perpendicular to the X and Z directions (direction perpendicular to the paper surface of Fig. 1) as the Y direction. The X direction is the measurement direction, and the magnetostriction measuring device 100 measures magnetostriction in the X direction of the steel plate 40 to be measured.

[0023] The steel plate 40 to be measured is positioned so that it passes through the excitation coil 18. The yoke 14 is provided to form a closed magnetic circuit. The yoke 14 is mounted on the table 10 via the support member 12. The measurement frame 16 is a plate-shaped member formed from a non-conductive (non-magnetic) material. As an example, the measurement frame 16 is made of a material such as epoxy resin. Specific examples of materials include glass epoxy, which is made by layering glass fiber cloth and impregnating it with epoxy resin, a material in which antistatic carbon-containing fluororesin glass cloth adhesive tape is adhered to the glass fiber cloth, or conductive polycarbonate. The measurement frame 16 is fixed to and supported by the yoke 14. The steel plate 40 is placed on the measurement frame 16.

[0024] The excitation coil 18 is wound around the outside of the measurement frame 16 so that the measurement frame 16 is located inside. The excitation coil 18 is wound so that it forms a cylindrical shape with the winding axis extending in the X direction. When current is applied to the excitation coil 18, it generates a magnetic flux in the X direction that passes through the excitation coil 18.

[0025] The steel plate 40 to be measured is positioned so that it passes through the excitation coil 18 in the X direction. The steel plate 40 is placed on the measurement frame 16, with one end 40a (the right end in FIG. 1 ) in the X direction abutting against the end stop 22, thereby determining its position relative to the measurement frame 16. The end stop 22 is installed on the table 10 via a support member 20. The end stop 22 is at ground potential, earthing any charged electric charge to the ground. The other end 40b (the left end in FIG. 1 ) of the steel plate 40 is a free end. As a result, when the steel plate 40 expands and contracts due to magnetostriction, the one end 40a is used as a fixed end, and the portion of the steel plate 40 closer to the other end 40b than the fixed end displaces relative to the end stop 22 and the measurement frame 16. Note that the one end 40a may be fixed by a clamp.

[0026] The laser vibrometer 26 is placed on the table 10 via a support member 24. The laser vibrometer 26 irradiates a laser beam L in the X direction. The laser vibrometer 26 irradiates a reflector 42 with the laser beam L and detects the laser beam L reflected by the reflector 42 fixed to the steel plate 40, thereby generating a vibration waveform (magnetostriction waveform) representing the displacement of the reflector 42 in the X direction, i.e., the vibration of the steel plate 40, and outputs it as an output signal.

[0027] More specifically, the reflector 42 that reflects the laser light L from the laser vibrometer 26 may include two reflectors, a reflector 42a and a reflector 42b. In this case, the reflector 42a is fixed to the steel plate 40 and displaces in response to expansion and contraction of the steel plate 40 due to magnetostriction. The reflector 42b is independent of the steel plate 40 and does not displace even when the steel plate 40 expands and contracts. The reflector 42b is fixed directly or indirectly to the table 10 so that the reflector 42b does not displace in the X direction even when the steel plate 40 displaces (vibrates) in the X direction. The reflector 42b may be fixed to, for example, the yoke 14. The laser vibrometer 26 is a laser Doppler vibrometer that irradiates each of the reflectors 42a and 42b with laser light L and detects the reflected light (reflected laser light) from each of the reflectors 42a and 42b. That is, the reflected light from the reflectors 42a and 42b is input to the laser vibrometer 26 as a differential signal. Then, the laser vibrometer 26 generates a vibration waveform (magnetostriction waveform) representing the vibration of the steel plate 40 based on this differential signal, and outputs it as an output signal.

[0028] Here, with an AC magnetic field applied by the excitation coil 18, the vibration of the steel sheet 40 measured by the laser vibrometer 26 (the magnetostriction waveform generated by the laser vibrometer 26) represents the magnetostriction characteristics of the steel sheet 40. In other words, the laser vibrometer 26 is capable of measuring the magnetostriction characteristics of the steel sheet 40.

[0029] As a result of extensive investigation, the present inventors have noticed that, when measuring the magnetostriction of a steel sheet 40, differences in the measured values ​​occur between measurements of multiple steel sheets 40. The present inventors have also noticed a phenomenon in which the value measured at the start of the magnetostriction measurement becomes smaller at the end of continuous measurements several hours later. Furthermore, the present inventors have noticed that differences occur between the values ​​measured in summer and winter, with the measured values ​​being smaller in winter.

[0030] In order to reduce the variance in magnetostriction measurements, it is necessary to suppress the force that inhibits the expansion and contraction of the steel sheet 40 due to magnetostriction. One possible cause of this inhibition is the frictional force acting between the steel sheet 40 and the measurement frame 16. In order to eliminate the influence of this frictional force, dust particles and other particles present between the measurement frame 16 and the steel sheet 40 were cleaned and measurements were performed. This temporarily stabilized the measurements, but the decrease in the measurements did not disappear over the course of several hours as the steel sheet 40 was sequentially moved in and out of the measurement frame 16 and measurements were performed.

[0031] For this reason, the inventors believed that the force of attraction of the steel sheet 40 to the measurement frame 16 due to static electricity was affecting the expansion and contraction of the steel sheet 40 due to magnetostriction, and intentionally generated static electricity in the measurement frame 16 and the steel sheet 40 due to friction that occurred when the steel sheet 40 was placed in and removed from the measurement frame 16. When the magnetostriction was then measured, the measured value was significantly reduced. From this, the inventors discovered that the attractive force due to static electricity suppresses the expansion and contraction of the steel sheet 40, and that static electricity is the cause of the variation in the measured magnetostriction values.

[0032] Therefore, the inventors have thoroughly investigated the material of the measurement frame 16 that contacts the steel sheet 40 so as to prevent static electricity from being generated between the steel sheet 40 and the mounting portion that contacts the steel sheet 40, i.e., the measurement frame 16. Since static electricity is believed to be the cause of the variability in magnetostriction measurements, the material of the surface of the measurement frame 16 on which the steel sheet 40 to be measured is mounted was changed to a material that is less likely to accumulate charge, i.e., a material through which electricity flows more easily. Then, the magnetostriction characteristics of the steel sheet 40 were measured each time the surface material of the measurement frame 16 was changed. As a result, the inventors have found that changing the surface material of the measurement frame 16 from a conventional material (e.g., a fluororesin-impregnated glass cloth film) to a material with a lower resistivity reduces the variability in the magnetostriction measurements.

[0033] Furthermore, the electrostatic attraction force of the measurement frame 16 acts on the surface of the measurement frame 16 that comes into contact with the steel plate 40. As a result of extensive research, the inventors have found that the effect of reducing the variation in magnetostriction measurement values ​​by changing the material of the surface of the measurement frame 16 is not limited to when the material of the measurement frame 16 itself is changed, i.e., when the material of the measurement frame 16 is homogeneous throughout its entirety, but can also be obtained when a conductive coating is applied to the surface of the measurement frame 16 or when a conductive sheet is adhered to the surface of the measurement frame 16. Figure 2 is a schematic diagram showing a magnetostriction measurement device 100 according to an embodiment of the present disclosure, illustrating an example in which a conductive coating 16a or a conductive sheet 16b is provided on the surface of the measurement frame 16.

[0034] Specifically, the inventors have conducted extensive research and found that the resistivity of the surface of the measurement frame 16 is 10 １２ There is a portion on the surface of the measurement frame 16 where the resistivity is 10 １２ The presence of a portion satisfying the resistivity of Ω·m or less makes it difficult for static electricity to accumulate in the measurement frame 16. Therefore, it is possible to suppress the influence of static electricity on the measurement accuracy of magnetostriction, and it is possible to effectively suppress the variation in the measurement value. ９ Ω·m or less, and more preferably 10 ６When the conductive coating 16a is applied to the surface of the measurement frame 16, or when the conductive sheet 16b is attached to the surface of the measurement frame 16, the resistivity of the surface of the measurement frame 16 with the conductive coating 16a or the conductive sheet 16b is 10 １２ In other words, when the conductive coating 16a or the conductive sheet 16b is provided on the surface of the measurement frame 16, the resistivity of the surface of the measurement frame 16 is 10 Ω·m or less before the conductive coating 16a or the conductive sheet 16b is provided. １２ It is not necessary for there to be any portion that satisfies the resistivity of Ω·m or less. The lower limit of the resistance value is preferably 0 Ω·m or more, but there are restrictions depending on the material. For example, even with conductive MC nylon, which has high conductivity, the resistivity is 1 to 10 ２ Ω·m. Therefore, the lower limit of the resistance value is set to 1 Ω·m. When the conductive sheet 16b has an adhesive layer, the conductive sheet 16b may be attached to the measurement frame 16 and adhered to the measurement frame 16 by the adhesive layer.

[0035] The method for measuring the surface resistivity of the measurement frame 16 complies with JIS C 2139-3-1:2018. For the measurement, a rectangular parallelepiped test piece measuring 100.0 mm or more in length, 100.0 mm or more in width, and 1.0 mm ± 0.1 mm in thickness is taken from the measurement frame 16. The top surface of this test piece is the top surface of the measurement frame 16, i.e., the surface that comes into contact with the steel plate 40. If it is difficult to take a test piece of the above thickness, the thickness of the sample actually used may be used as the test piece. If a conductive coating 16a is applied to the surface (top surface) of the measurement frame 16 or a conductive sheet 16b is adhered to the surface (top surface) of the measurement frame 16, the test piece is taken including the conductive coating 16a or conductive sheet 16b.

[0036] Furthermore, as a result of extensive investigation, the inventors have concluded that even if the measurement frame 16 becomes charged during magnetostriction measurement, variability in magnetostriction measurement can be reduced by removing the static electricity so that it does not affect the magnetostriction measurement. From this perspective, the inventors have found that variability in measured magnetostriction can be reduced by specifying the magnitude relationship between the resistivity ρ (Ω m) of the surface of the measurement frame 16 and the measurement frequency f (Hz) of magnetostriction.

[0037] Since the cause of the variation in the magnetostriction measurement values ​​is static electricity due to friction between the measurement frame 16 and the steel plate 40, the higher the measurement frequency f (Hz) of magnetostriction, the greater the amount of friction generated per unit time, and the greater the amount of charge in the measurement frame 16.

[0038] On the other hand, the amount of charge on the measurement frame 16 decreases over time if there is no further charging. Specifically, the charge Q generated on the measurement frame 16 due to charging λ decays according to the following charge decay formula (1):

[0039]

[0040] In equation (1), t is the elapsed time (seconds), Q is the charge (charge amount) after the elapsed time t (seconds), εr is the relative permittivity of the surface of the measurement frame 16, and ε0 (F / m) is the permittivity of a vacuum. Also, ρ is the resistivity (Ω·m) of the measurement frame 16, measured using the method described above. The relative permittivity εr of the surface of the measurement frame 16 is the relative permittivity of the measurement frame 16 itself if the material of the measurement frame 16 is homogeneous throughout its entire surface. Furthermore, if a conductive coating is applied to the surface of the measurement frame 16 or if a conductive sheet is adhered to the surface of the measurement frame 16, the relative permittivity εr is the relative permittivity of the conductive coating or conductive sheet. The relative permittivity is measured according to the null method of JIS C 2138-2007. For measurement, a 60 mm x 60 mm flat plate sample is cut out as a test piece, and measurement is performed using, for example, an LCR meter IM3536 manufactured by Hioki E.E. Corporation. The overall dielectric constant ε can be calculated from this, so to calculate the relative dielectric constant εr, the measured dielectric constant ε can be divided by the dielectric constant ε0 of a vacuum. The dielectric constant ε0 of a vacuum is ε0 = 8.8542 × 10 －１２ Fm －１Let's say.

[0041] The inventors calculated the charge Q generated in the measurement frame 16 according to equation (1). λ decays, and the charge Q becomes the charge Q λ It was found that if the measurement period T of magnetostriction is longer than the relaxation time t1 (half-life), which is half of the relaxation time t1, the charge accumulated in the measurement frame 16 is sufficiently discharged during the measurement period T, the effect of static electricity on the magnetostriction measurement is suppressed, and the variance in the measured magnetostriction values ​​is further reduced.

[0042] The relaxation time t1 is calculated based on the formula (1), Q = Q λ / 2 is substituted and the result is obtained from the following equation (2).

[0043]

[0044] The measurement period T (seconds) of magnetostriction is the reciprocal of the measurement frequency f (Hz). Therefore, if the measurement frequency f satisfies the following formula (3), even if static electricity temporarily accumulates in the measurement frame 16 due to friction during magnetostriction measurement, further static electricity will not accumulate and the accumulated static electricity will be discharged. This makes it possible to suppress the effect of static electricity on measurement accuracy and more effectively suppress the variation in the measured magnetostriction values.

[0045]

[0046] Since the higher the resistivity ρ, the more difficult it is for electricity to flow, the greater the resistivity ρ, and therefore the longer the relaxation time t1. Therefore, by lowering the measurement frequency f as the resistivity ρ of the measurement frame 16 increases, the effect of static electricity on measurement accuracy can be suppressed, and the variance in the measured magnetostriction values ​​can be reduced.

[0047] To eliminate static electricity accumulated in the measurement frame 16, the measurement frame 16 is connected to earth. Preferably, the earth resistance of the earth is 1 MΩ or less. This allows static electricity accumulated in the measurement frame 16 to be discharged via the earth, and the measurement frame 16 is more effectively neutralized. If the earth resistance is greater than 1 MΩ, static electricity is not sufficiently neutralized, and the effect of grounding is not realized.

[0048] As described above, the effect of reducing the variation in magnetostriction measurement values ​​by changing the surface material of the measurement frame 16 is not limited to when the material of the measurement frame 16 is homogeneous throughout its entire area, but can also be achieved when a conductive coating is applied to the surface of the measurement frame 16 or when a conductive sheet is adhered to the surface of the measurement frame 16. Therefore, the measurement frame 16 may have a conductive coating formed on its surface or a conductive sheet adhered to its surface. In this case, the measurement frame 16 itself may be made of an insulator.

[0049] As described above, the magnetostriction measurement method according to this embodiment is as follows: (1) A measurement method for measuring magnetostriction of a steel sheet, wherein the resistivity measured in accordance with JIS C 2139-3-1:2018 on the surface of a mounting portion on which the steel sheet is mounted is 10 １２ (2) A magnetostriction measurement method in which magnetostriction is measured so that there is at least a portion that satisfies the dielectric constant ρ (Ω-m) or less. When the measurement frequency of magnetostriction is f (Hz), the relative dielectric constant of the surface of the mounting portion is εr, and the dielectric constant of vacuum is ε0 (F / m), the resistivity ρ (Ω-m) of the surface of the mounting portion satisfies the following formula: (3) The placing portion is grounded to a ground having a ground resistance of 1 MΩ or less.

[0050] The present disclosure will be specifically described below using examples. Note that the conditions in the examples are examples adopted to confirm the feasibility and effects of the present disclosure, and the present disclosure is not limited to the conditions in the examples. Various conditions may be adopted in the present disclosure as long as they do not deviate from the gist of the disclosure and the purpose is achieved.

[0051] Twelve types (Test Nos. 1 to 15) of mounting portions (measurement frames 16) were fabricated as shown in Table 1 below. Test No. 1 was a conventional measurement frame 16, and the material of the measurement frame 16 (fluorine resin-impregnated glass cloth film) was uniform throughout the entire measurement frame 16. Test Nos. 2, 4, 6, 8, 10, and 11 were cases in which the material of the measurement frame 16 itself was changed from the conventional product, and the material of the measurement frame 16 was uniform throughout. Test Nos. 3, 5, 7, 9, 12, 13, 14, and 15 were cases in which the material of the measurement frame 16 itself was the same as the conventional product, and a conductive coating was applied to the surface of the measurement frame 16.

[0052]

[0053] The material of the measurement frame 16 in Test Nos. 2, 4, 6, 8, 10, and 11 was adjusted by changing the carbon content relative to natural rubber.

[0054] The material of the conductive coating of the measurement frame 16 in Test Nos. 3, 5, 7, 9, 12, 13, 14, and 15 was a conductive fluororesin, and the conductivity was adjusted by adjusting the amount of carbon and titanium oxide contained in the fluororesin and the amount of coating.

[0055] The measured values ​​of the resistivity and dielectric constant of the measurement frame 16 in Test Nos. 1, 2, 4, 6, 8, 10, and 11 were as shown in Table 1. The measured values ​​of the resistivity and dielectric constant of the conductive coating in Test Nos. 3, 5, 7, 9, 12, 13, 14, and 15 were as shown in Table 1. The resistivity was measured as described above in accordance with JIS C 2139-3-1:2018. The resistivity of Test Nos. 3, 5, 7, 9, 12, 13, 14, and 15 with the conductive coating was measured by collecting test pieces including the conductive coating after the conductive coating was applied to the measurement frame 16 and measuring the resistivity using the measurement method in accordance with JIS C 2139-3-1:2018. The dielectric constant of the conductive coating was measured using the measurement method in accordance with the null method of JIS C 2138-2007.

[0056] In Test Nos. 1 to 9, the measurement frame 16 was not grounded, and in Test Nos. 10 to 15, the measurement frame 16 was grounded. The ground resistance in Test No. 10 was 10 MΩ, and the ground resistance in Test Nos. 11, 12, 13, 14, and 15 was 1 MΩ.

[0057] The measurement frequency for magnetostriction in Test Nos. 1 to 3 and 8 to 15 was 50 Hz, and the measurement frequency for magnetostriction in Test Nos. 4 to 7 was 100 Hz.

[0058] For each of Test Nos. 1 to 15, the magnetostriction was measured 10 times and the standard deviation σ of the amplitude λpp of the magnetostrictive vibration was calculated. The amplitude λpp is the peak-to-peak value of the amplitude of the magnetostrictive waveform. As shown in Table 1, the standard deviation σ of the amplitude λpp of the magnetostrictive vibration was calculated for the surface of the measurement frame 16 when the resistivity was 10１２ The standard deviation σ of the amplitude λpp in Test Nos. 2 to 15, which had a portion satisfying the resistivity of Ω·m or less, was 0.12 or less. １５ The standard deviation σ of the amplitude λpp in Test No. 1, which had a portion where Ω·m existed, was 0.15, which was larger than those in Test Nos. 2 to 15.

[0059] The measurement frames 16 of Test Nos. 1 to 5 did not satisfy formula (3). On the other hand, the measurement frames 16 of Test Nos. 6 to 15 satisfied formula (3). As a result of satisfying formula (3), the measurement frames 16 of Test Nos. 6 to 15 had smaller standard deviations σ of the amplitude λpp than Test Nos. 2 to 5.

[0060] In Test Nos. 3, 5, 7, 9, and 12, the conductive coating was uniformly formed on the surface of the measurement frame 16. Therefore, it is believed that the resistivity of the test piece after the conductive coating was applied was the same regardless of the position of the measurement frame 16 from which the test piece was cut. On the other hand, in Test Nos. 13 to 15, the conductive coating was formed non-uniformly on the surface of the measurement frame 16. Test pieces were then taken from such measurement frames 16, and test pieces with conductively coated areas of 5%, 20%, and 50% were respectively taken and measured. That is, in Test No. 13, the conductive coating was applied to 50% of the entire surface of the test piece. In addition, in Test No. 14, the conductive coating was applied to 20% of the entire surface of the test piece, and in Test No. 15, the conductive coating was applied to 5% of the entire surface of the test piece. As a result of the measurements, it was found that the resistivity at which conductivity was maintained was 10%. １２ Even if the number of surfaces with a resistivity of Ω·m or less decreased, the standard deviation σ of magnetostriction was maintained at a low value as long as such surfaces existed. １２ It was found that it is sufficient if even a portion that satisfies Ω·m or less exists.

[0061] As described above, according to this embodiment, the resistivity of the surface of the measurement frame 16 on which the steel plate 40 to be measured is placed is 10 １２The presence of a portion satisfying Ω·m or less makes it difficult for static electricity to accumulate in the measurement frame 16. Therefore, it is possible to suppress the effect of static electricity on the measurement accuracy of magnetostriction, and to effectively suppress the variation in the measurement values.

[0062] REFERENCE SIGNS LIST 10 table 12, 20, 24 support member 14 yoke 16 measurement frame 16a conductive coating 16b conductive sheet 18 excitation coil 22 end stop 26 laser vibrometer 40 steel plate 40a, 40b end portion 42, 42a, 42b reflector 100 magnetostriction measuring device

Claims

1. A measuring device for measuring magnetostriction of steel plate, comprising a mounting portion on which the steel plate to be measured for magnetostriction is placed, and the resistivity measured in accordance with JIS C 2139-3-1:2018 on the surface of the mounting portion on which the steel plate is placed is 10 １２ A magnetostriction measuring device in which there is at least a portion that satisfies Ω·m or less.

2. A magnetostriction measuring device as described in claim 1, wherein the resistivity ρ (Ω·m) of the surface of the mounting portion satisfies the following formula, where f (Hz) is the measurement frequency of magnetostriction, εr is the relative dielectric constant of the surface of the mounting portion, and ε0 (F / m) is the dielectric constant of vacuum.

3. The magnetostriction measuring device according to claim 1 or 2, wherein the mounting portion is grounded to a ground having a ground resistance of 1 MΩ or less.

4. A magnetostriction measuring device according to claim 1 or 2, wherein the mounting portion has a conductive coating formed on the surface of the mounting portion or a conductive sheet adhered to the surface.

5. A method for measuring magnetostriction of a steel plate, in which the resistivity measured in accordance with JIS C 2139-3-1:2018 on the surface of the mounting part on which the steel plate is placed is 10 １２ A magnetostriction measurement method in which magnetostriction is measured so that there is at least a portion that satisfies Ω·m or less.

6. A magnetostriction measurement method according to claim 5, wherein the resistivity ρ (Ω·m) of the surface of the mounting portion satisfies the following formula, where f (Hz) is the measurement frequency of magnetostriction, εr is the relative dielectric constant of the surface of the mounting portion, and ε0 (F / m) is the dielectric constant of a vacuum.

7. The magnetostriction measuring method according to claim 5 or 6, wherein the mounting portion is grounded to a ground having a ground resistance of 1 MΩ or less.

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