JP2017156210A - Strain measurement device and strain measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strain measurement device for measuring a distance of displacement of a measured body on the basis of capacitance of a capacitor which is formed by a first electrode and a second electrode.SOLUTION: In a strain measurement device, a first electrode has a tabular shape, and a facing surface of a second electrode, which faces the first electrode, is a curved surface whose distance from the first electrode becomes continuously longer from the center toward an outer periphery of the first electrode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a strain measuring device and a strain measuring method.

  For example, a strain measuring device that measures the strain on the surface of a measured object in order to inspect the remaining life of a metal weld or the like is known (for example, Patent Document 1).

JP2007-315853A

  In the above-mentioned Patent Document 1, a rod-shaped second electrode is inserted into a cylindrical first electrode, and the length of strain is determined based on the capacitance of a capacitor formed by the first electrode and the second electrode. A strain measuring device for measuring is disclosed. In the strain measuring apparatus of Patent Document 1, when any of the electrodes is displaced in a direction other than the direction in which the first electrode is inserted into the second electrode, the electric field concentrates on a part of each electrode. There is a possibility that the length of the strain cannot be accurately measured due to changes in the target characteristics.

  A main aspect of the present invention for solving the above-described problem is a strain measurement apparatus for measuring a displacement distance of a measurement object based on a capacitance of a capacitor formed by a first electrode and a second electrode, One electrode has a flat plate shape, and the opposing surface of the second electrode facing the first electrode is continuously spaced from the center of the first electrode toward the outer edge. This is a strain measuring device that exhibits a long curved surface shape.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, even when the first electrode or the second electrode is displaced in a direction other than the direction toward the respective electrodes, the length of strain is accurately measured without changing the electrical characteristics of the capacitor. be able to.

It is sectional drawing of the distortion measuring apparatus which concerns on this embodiment. It is a perspective view showing the 2nd electrode of a 1st embodiment concerning this embodiment. It is a perspective view which shows the 2nd electrode of 2nd Embodiment which concerns on this embodiment. It is sectional drawing explaining the curvature radius of the 2nd electrode which concerns on this embodiment. It is a flowchart which shows the measurement procedure of the distortion measuring device which concerns on this embodiment. It is sectional drawing of the conventional distortion measuring apparatus. It is a perspective view which shows the electrode of the conventional distortion measuring device.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings. 1 to 3, the same reference numerals are used for the same components. 1 to 6, the X axis is an axis along the longitudinal direction of the second electrode 13, the Y axis is an axis along the vertical direction with respect to the surface of the measurement object 100, and the Z axis is the X axis and It is an axis orthogonal to the Y axis.

=== Configuration ===
FIG. 1 is a cross-sectional view of a strain measuring apparatus 1 according to this embodiment. FIG. 2 is a perspective view showing the second electrode 13A of the first embodiment according to the present embodiment. FIG. 3 is a perspective view showing the second electrode 13B of the second embodiment according to this embodiment. Hereinafter, the configuration of the strain measuring apparatus 1 will be described with reference to FIGS. 1, 2 and 3.

  Under a high temperature environment (for example, 600 ° C.) in a power plant, the welded part 110 of the metal member is deteriorated by heat and causes distortion. The strain measuring device 1 is a device that measures the length of the strain. In the strain measuring apparatus 1, for example, a first electrode 11 and a second electrode 13, which will be described later, are arranged so as to straddle the welded portion 110, and the first electrode 11 and the second electrode 11 are arranged in accordance with the strain length of the welded portion 110. The distance between the electrodes 13 is changed, and the length of strain is measured based on the change.

  The strain measuring apparatus 1 includes, for example, a first electrode 11, a second electrode 13, a first insulating support 15, a second insulating support 16, a capacitance measuring unit 20, and a strain calculating unit 30. . The strain gauge 10 is composed of the first electrode 11, the second electrode 13, the first insulating support 15, and the second insulating support 16. For convenience of explanation, in the explanation of the second electrode 13, the second electrode 13A of the first embodiment and the second electrode 13B of the second embodiment will be explained.

<< First electrode >>
The 1st electrode 11 is an electrode which forms the capacitor | condenser 40 facing the 2nd electrode 13 mentioned later. The first electrode 11 is made of, for example, a metal material and has, for example, a flat plate shape. As the metal material used for the first electrode 11, for example, platinum, nickel base alloy, chromium base alloy, cobalt base alloy, or stainless steel containing chromium is used. That is, the first electrode 11 may be a metal material that is formed of a metal material that does not oxidize in a high-temperature environment and has little change in properties even when used for a long time. As a result, the first electrode 11 can avoid a change in the dielectric constant of the surface due to oxidation, which is likely to occur in a high temperature environment. Measurement error can be reduced.

  The first electrode 11 is supported by the measured object 100 via a first insulating support 15 described later. The flat surface 12 of the first electrode 11 is disposed so as to face a facing surface 14 of a second electrode 13 described later. A capacitor 40 is formed by the plane 12 and the facing surface 14. The capacitor 40 includes a distance between the plane 12 and the facing surface 14, a facing area where the plane 12 and the facing surface 14 face each other when the capacitor 40 is viewed in the −X direction, a dielectric constant, , Based on capacitance. That is, the strain measuring apparatus 1 measures the length of the strain according to the change because the distance changes and the capacitance changes accordingly when the measured object 100 changes in the direction along the X axis. .

<< Second electrode >>
The second electrode 13 is an electrode that forms the capacitor 40 facing the first electrode 11. The second electrode 13 is formed of, for example, a metal material and has, for example, a rod shape. As the metal material used for the second electrode 13, as in the first electrode 11, for example, platinum, a nickel base alloy, a chromium base alloy, a cobalt base alloy, or stainless steel containing chromium is used. The second electrode 13 is supported by the measured object 100 via a second insulating support 16 described later. The facing surface 14 of the second electrode 13 is disposed so as to face the flat surface 12 of the first electrode 11. The second electrode 13 is formed so that the facing surface 14 is opposed to the width of the flat surface 12 of the first electrode 11 in the Y direction and the Z direction. In other words, the second electrode 13 is formed such that the facing surface 14 is located inside the outer edge of the flat surface 12 when viewed in the + X direction. For example, the second electrode 13 can be used in any form of a second electrode 13A of the first embodiment and a second electrode 13B of the second embodiment described below.

  The second electrode 13A of the first embodiment will be described with reference to FIG. For example, the second electrode 13A has, at one end, a facing surface 14A that has a shape such that when viewed from the Z direction, the shape moves away from the plane 11 from the center of the plane 12 toward the Y direction. Specifically, for example, the facing surface 14A is formed to draw an arc when viewed from the Z direction, and is formed to draw a rectangle when viewed from the X direction and the Y direction. In other words, the distance between the facing surface 14A and the plane 12 of the first electrode 11 does not change in the direction along the Z-axis, and the distance from the center of the facing surface 14A increases in the direction along the Y-axis. It is formed so as to be continuously away from the flat surface 12 of one electrode 11. The curvature radius of the facing surface 14A is about 1 to 0.5 times the diameter of the measured object 100 (for example, a pipe), considering that each leg portion 50 is disposed so as to straddle the welded portion 110, or Or it is desirable to set so that either of 1-0.5 times the distance between installation of each leg part 50 may be satisfied. Specifically, as shown in FIG. 4, when the measured object 100 is used as a reference, when the measured object 100 is distorted around the welded portion 110, the opposing surface 14A of the second electrode 13A becomes the measured object. A distance R1 (about 0.5 times the diameter) from the center of each 100 to each leg 50 or a distance R2 (about 1.0 times the diameter) from the center of the measured object 100 to each leg 50 If it has a radius of curvature, the strain measuring apparatus 1 can measure the strain with high accuracy. Considering each leg as a reference, distortion occurs in the measured object 100 around the welded part 110, and therefore distortion occurs between each leg 50. Distance L1 (about 0.5 times the distance between each leg 50 installation) or distance L2 between each leg 50 (about 1.0 times the distance between each leg 50 installation). If it has a radius of curvature, the strain measuring apparatus 1 can measure the strain with high accuracy.

  That is, in the second electrode 13A of the first embodiment, the alignment is shifted in the + Y direction or the −Y direction with respect to the X axis (a state in which an angle is provided between the provisional line along the X axis and the second electrode 13). ) Has a shape that does not affect the capacitance of the capacitor 40A.

  The second electrode 13B of the second embodiment will be described with reference to FIG. The second electrode 13 </ b> B has a spherical shape at one end, and has a facing surface 14 </ b> B that faces the first electrode 11. Specifically, the facing surface 14B is formed to draw an arc when viewed from any direction orthogonal to the X axis. In other words, the facing surface 14B moves away from the plane 12 of the first electrode 11 as it moves away from the center point of the facing surface 14B (the point closest to the first electrode 11 on the facing surface 14B) on the plane 12 including the Y axis and the Z axis. It is formed so as to continuously move away. The curvature radius of the facing surface 14B is about 1 to 0.5 times the diameter of the measured object 100 (for example, a pipe), considering that each leg portion 50 is disposed so as to straddle the welded portion 110, or Or it is desirable to set so that either of 1-0.5 times the distance between installation of each leg part 50 may be satisfied. Specifically, as shown in FIG. 4, when the measured object 100 is based on the measured object 100, when the measured object 100 is distorted around the welded portion 110, the opposing surface 14 </ b> B of the second electrode 13 </ b> B is A distance R1 (about 0.5 times the diameter) from the center of each 100 to each leg 50 or a distance R2 (about 1.0 times the diameter) from the center of the measured object 100 to each leg 50 If it has a radius of curvature, the strain measuring apparatus 1 can measure the strain with high accuracy. Considering each leg as a reference, distortion occurs in the measured object 100 around the welded part 110, and therefore distortion occurs between each leg 50. Distance L1 (about 0.5 times the distance between each leg 50 installation) or distance L2 between each leg 50 (about 1.0 times the distance between each leg 50 installation). If it has a radius of curvature, the strain measuring apparatus 1 can measure the strain with high accuracy.

  That is, the second electrode 13B of the second embodiment has a shape that does not affect the capacitance of the capacitor 40B due to misalignment in the Y direction, the Z direction, and the torsional direction with respect to the X axis.

  As described above, in the conventional strain measuring apparatus 200, for example, when the position of at least one of the electrodes changes in a direction other than the direction in which the rod-shaped electrode 220 is inserted, as shown in FIGS. Inside, a part of the rod-shaped electrode 220 is arranged so that a part thereof is close and partly away, and the electric field is concentrated on a part between the respective electrodes. This solves the problem of being unable to measure the thickness.

<< first insulating support >>
The first insulating support 15 is a member that electrically insulates the first electrode 11 from the measurement target 100 and supports the first electrode 11 on the measurement target 100 via the attachment member 50. The first insulating support 15 covers at least the outer edge portion of the first electrode 11 in the hollow, and is fixed so that the plane 12 of the first electrode 11 is along the YZ plane. The hollow of the first insulating support 15 is a hole having a size that fits a cross section cut along the YZ plane of the second electrode 13 so that, for example, one end of the second electrode 13 is inserted. That is, the first insulating support 15 is configured to serve as a bearing for the second electrode 13. Therefore, since the second electrode 13 is covered at one end with the first insulating support 15, the risk of baking is reduced even in a high temperature environment.

  The first insulating support 15 is made of, for example, a ceramic material and has, for example, a hollow cylindrical shape. This is because the ceramic material can ensure electrical insulation even in a high temperature environment (for example, 600 ° C.). For example, if the purity of the ceramic material is 90% or more, the electrical insulation is maintained at room temperature, and the purity is particularly preferably 99% or more. More preferably, if the purity of the ceramic material is 99.7% or higher, an insulation resistance of about 40 MΩ can be realized even in a high temperature environment of, for example, 600 ° C. The ceramic material is preferably alumina, for example. This is because alumina having a purity of 99.7% exhibits an insulation resistance of 40 MΩ even under a high temperature environment of 600 ° C.

  In the above description, the first insulating support 15 is assumed to have a cylindrical shape. However, the present invention is not limited to this. For example, a prismatic shape may be used as long as it has a hollow through which the second electrode 13 is inserted. The hollow of the first insulating support 15 may have a guide portion so that the second electrode 13 is guided by the first electrode 11. In this case, for example, the guide portion is formed by providing a groove (not shown) in a part of the hollow, and formed by providing a convex part (not shown) that fits in the groove in a part of the second electrode 13. .

<< second insulating support >>
The second insulating support 16 is a member that electrically insulates the second electrode 13 from the measurement target 100 and supports the second electrode 13 on the measurement target 100 via the attachment member 50. The second insulating support 16 is a member that covers the outer periphery of the other end of the second electrode 13. The second insulating support 16 is made of, for example, a ceramic material and has, for example, a quadrangular prism shape. The ceramic material is the same as that of the first insulating support 15, and the description thereof is omitted.

  In the above description, the second insulating support 16 is described as having a quadrangular prism shape, but the present invention is not limited to this. For example, a prismatic shape may be used as long as the second electrode 13 is supported.

<< Capacitance measurement section >>
The capacitance measuring unit 20 is a device that measures the capacitance of the capacitor 40 formed by the first electrode 11 and the second electrode 13, for example. The capacitance measuring unit 20 is configured by, for example, a charge amplifier or an LCR meter. The capacitance measuring unit 20 is connected to the capacitor 40 and measures the capacitance based on a signal output from the capacitor 40. The capacitance measuring unit 20 outputs information indicating the capacitance to the strain calculating unit 30 described later.

<< Strain calculation section >>
The strain calculation unit 30 is a device that calculates the length of strain based on information indicating the capacitance output from the capacitance measurement unit 20, for example. The strain calculation unit 30 includes, for example, a ROM, a RAM, and a CPU. The strain calculation unit 30 has a function of outputting information indicating the length of strain to a display unit (not shown), for example.

=== Measurement procedure ===
Hereinafter, the measurement procedure of the strain measuring apparatus 1 will be described with reference to FIG. In the following, the main body that executes S100 is an operator, the main body that executes S101 is the capacitor 40, and the main body that executes S102 and S103 is the capacitance measuring unit 20, and executes S104. The subject to perform is the strain calculation unit 30. Further, the strain measuring apparatus 1 includes a storage unit (not shown) in which programs for executing the capacitance measuring unit 20 and the strain calculating unit 30 are stored. For example, the functions of the capacitance measuring unit 20 and the strain calculating unit 30 are executed based on the execution result of the program of the strain measuring device 1.

  First, an operator arrange | positions the 1st electrode 11 and the 2nd electrode 13 of the strain gauge 10 so that the welding part 110 of a measuring object may be straddled (S100). The capacitance of the capacitor 40 changes according to the displacement in the direction along the temporary line connecting the first electrode 11 and the second electrode 13. The capacitor 40 outputs a signal to the capacitance measuring unit 20 (S101). The capacitance measuring unit 20 measures the capacitance based on the signal input from the capacitor 40 (S102). The capacitance measuring unit 20 outputs information indicating the capacitance to the strain calculating unit 30 (S103). The strain calculation unit 30 calculates the length of the strain based on the information indicating the capacitance (S104).

  In the above measurement procedure, after the strain gauge 10 is installed, the second electrode 13 is displaced from the first electrode 11 in a direction other than the direction along the temporary line connecting the first electrode 11 and the second electrode 13. May occur. That is, the alignment may be shifted between the first electrode 11 and the second electrode 13. However, when the opposing surfaces (14A, 14B) of the second electrodes (13A, 13B) are the circular surfaces of the first embodiment or the spherical surfaces of the second embodiment, the first is not affected by the misalignment. The distance between the flat surface 12 of the electrode 11 and the opposing surfaces (14A, 14B) of the second electrodes (13A, 13B) does not change. Therefore, the electrical characteristics do not change locally between the first electrode 11 and the second electrode 13, and the capacitance of the capacitor 40 does not shift. Therefore, when the first electrode and the second electrode have a flat plate shape, the strain length is more accurate than any of the strain gauges when the first electrode has a cylindrical shape and the second electrode has a rod shape. Can be measured.

  As described above, the strain measuring apparatus 1 according to the present embodiment measures the displacement distance of the measured object 100 based on the capacitance of the capacitor 40 formed by the first electrode 11 and the second electrode 13. The first electrode 11 has a flat plate shape, and the opposing surface 14 of the second electrode 13 that opposes the first electrode 11 has a first distance between the first electrode 11 and the first electrode 11. It is characterized by exhibiting a curved surface shape that becomes continuously longer from the center of the electrode 11 toward the outer edge. According to this embodiment, the strain length can be accurately measured without being affected by the alignment change of the strain gauge 10.

  Further, the strain measuring apparatus 1 according to the present embodiment is based on a capacitance measuring unit 20 that measures the capacitance of the capacitor 40 and information indicating the capacitance output from the capacitance measuring unit 20. And a strain calculating unit 30 that calculates the displacement distance of the DUT 100. According to the present embodiment, since the strain length measured by the strain gauge 10 can be handled as digital data, information management is facilitated.

  Further, the opposing surface 14A of the second electrode 13A of the strain measuring apparatus 1 according to the present embodiment is such that the distance from the flat surface 12 of the first electrode 11 increases as the distance from the center increases along one direction. It is a physical surface. According to the present embodiment, even if the second electrode 13A of the strain gauge 10 and the temporary line along the X axis are in an angled state, the length of the strain can be measured accurately.

  In addition, the opposing surface 14B of the second electrode 13B of the strain measuring apparatus 1 according to the present embodiment is characterized by having a spherical shape. According to the present embodiment, even when the second electrode 13B of the strain gauge 10 is displaced in the Y direction, the Z direction, and the torsional direction with respect to the X axis, the strain length can be accurately measured. .

  In the strain measuring apparatus 1 according to the present embodiment, the second electrode 13 is a rod-shaped electrode, and the opposing surface 14 of the second electrode 13 is provided at one end of the second electrode 13. Features. According to the present embodiment, measurement can be performed across the welded portion 110 or the like in accordance with the width of the welded portion 110 or the like that is likely to cause distortion between the first electrode 11 and the second electrode 13.

  Moreover, the strain measuring apparatus 1 according to the present embodiment accommodates the first electrode 11 and one end of the second electrode 13 so that the first electrode 11 and the second electrode 13 face each other, and the first electrode 11 is A first insulating support 15 that is supported by the measured object 100; and a second insulating support 16 that accommodates the other end of the second electrode 13 and supports the second electrode 13 to the measured object 100. It is characterized by. According to the present embodiment, it is possible to prevent the second electrode 13 from being exposed and seized in a high temperature environment.

  Further, the strain measuring apparatus 1 according to the present embodiment is characterized in that the first electrode 11 is made of platinum and the second electrode 13 is made of platinum. According to this embodiment, it can prevent that the 1st electrode 11 and the 2nd electrode 13 corrode in a high temperature environment.

  Further, the strain measuring apparatus 1 according to the present embodiment is characterized in that the first insulating support 15 is made of ceramic. According to this embodiment, a heat resistance effect and an insulation effect can be given to the first electrode 11.

  The strain measuring apparatus 1 according to the present embodiment is characterized in that the second insulating support 16 is made of ceramic. According to the present embodiment, a heat resistance effect and an insulation effect can be given to the second electrode 13.

  In addition, said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Strain measuring device 11 1st electrode 13 2nd electrode 13A 2nd electrode 13B 2nd electrode 14 Opposite surface 14A Opposite surface 14B Opposite surface 15 1st insulation support body 16 2nd insulation support body 20 Capacitance measurement part 30 Strain calculation Part 40 Capacitor 100 DUT

Claims (10)

A strain measuring device for measuring a displacement distance of a measured object based on a capacitance of a capacitor formed by a first electrode and a second electrode,
The first electrode has a flat plate shape,
The facing surface of the second electrode facing the first electrode has a curved surface shape in which the distance from the first electrode continuously increases from the center of the first electrode toward the outer edge. A strain measuring device. A capacitance measuring unit for measuring the capacitance of the capacitor;
Based on information indicating the capacitance output from the capacitance measuring unit, a strain calculating unit that calculates the displacement distance of the measured object;
The strain measuring device according to claim 1, further comprising: The facing surface of the second electrode is a surface having a certain curvature such that the distance from the flat plate surface of the first electrode increases as the distance from the center increases in one direction. Item 3. The strain measuring device according to Item 1 or Item 2. The strain measuring device according to claim 1, wherein the facing surface of the second electrode has a spherical shape. The second electrode is a rod-shaped electrode,
The strain measuring apparatus according to any one of claims 1 to 4, wherein the opposing surface of the second electrode is provided at one end of the second electrode. A first insulating support for accommodating the first electrode and one end of the second electrode so that the first electrode and the second electrode face each other, and supporting the first electrode on the object to be measured; ,
A second insulating support that accommodates the other end of the second electrode and supports the second electrode on the object to be measured;
The strain measurement apparatus according to claim 5, further comprising: The first electrode is formed of platinum;
The strain measuring device according to any one of claims 1 to 6, wherein the second electrode is formed of platinum. The strain measuring apparatus according to claim 6 or 7, wherein the first insulating support is made of ceramic. The strain measuring apparatus according to claim 8, wherein the second insulating support is made of ceramic. A strain measurement method for measuring a displacement distance of the measurement object using the strain measurement device according to claim 1,
Measuring the capacitance of the capacitor,
A strain measurement method, comprising: calculating a displacement distance of the measured object based on information indicating the capacitance.

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