JP4910135B2 - Strain measuring method and strain measuring apparatus - Google Patents

Description

  The present invention relates to a strain measuring method and a strain measuring apparatus, and more particularly to a strain measuring method and a strain measuring apparatus that can measure a minute strain with high accuracy.

  Conventionally, when it is necessary to measure the strain of a material that is an object, the strain is measured by mounting a resistance strain meter on the object.

  When a resistance strain gauge is used, it is difficult to perform multipoint measurement of a minute area because the subject needs an area for mounting the resistance strain gauge.

  Therefore, recently, a strain measuring apparatus has been proposed in which an indentation pair is formed at a predetermined position on the surface of a subject and a variation in the interval between the indentation pairs is measured using laser light interference (for example, Patent Document 1). reference.). That is, in this strain measuring apparatus, since it is only necessary to form an indentation on the subject, the area occupied by the indentation on the surface of the subject can be reduced, and the strain in a minute region can be measured.

Alternatively, a plurality of small-diameter holes or scribing lines are provided on the surface of the subject at predetermined intervals, and distortion is caused by fluctuations in the distance between adjacent small diameters or fluctuations in the distance between adjacent markings. A measurement method for measuring is also known (see, for example, Patent Document 2). The distance between the small diameters or the distance between the marking lines was measured by imaging the arrangement surface of the small diameter or marking lines with an appropriate imaging device, and performing image analysis to measure the distance dimensions. Strain is measured by analyzing the distance dimension.
Japanese Patent Laid-Open No. 06-235618 Japanese Patent Laid-Open No. 10-170234

  However, when the strain is measured using the distance between two indentations formed on the surface of the subject, at least two indentations separated by a predetermined distance are necessary. However, there was a problem that a small local strain could not be measured.

  Moreover, in strain measurement using a pair of indentations, only strain in the direction along the straight line connecting the indentation pairs can be measured, and strain in a direction different from the straight line cannot be evaluated. In order to accurately measure the strain generated in the subject, it is necessary to provide at least three indentations and evaluate the strain from three pairs of indentations. Comparison for providing indentations for measurement on the surface of the subject There was a problem that a large area was required.

  Furthermore, in the strain measurement using the indentation pair, only the strain in the surface direction of the subject surface can be evaluated, and the strain in the thickness direction of the subject cannot be evaluated.

  In view of such a current situation, the present inventors not only enable measurement of strain in a finer region, but also allow measurement of strain in the thickness direction of the subject as well as strain in the surface direction of the surface of the subject. Research and development have been conducted to arrive at the present invention.

  In the measurement method for measuring strain generated in the subject according to the present invention, the step of measuring the shape of the concave depression generated in the subject at the first timing and the second after a predetermined time from the first timing. Measuring the shape of the dent at the timing, and calculating the strain from the amount of change in shape from the shape of the dent at the first timing to the shape of the dent at the second timing.

Furthermore, the following points are also characteristic. That is,
(1) The depression is an indentation formed on the subject.
(2) The method includes a step of forming an indentation on the subject and a step of performing a residual stress removing process for removing a residual stress generated on the subject with the formation of the indentation after the formation of the indentation. (3) The indentation has a polygonal pyramid surface as a depression of a polygonal pyramid shape, and the strain is calculated based on the movement amount of the apex of the polygonal cone surface in the indentation.
(4) each vertex of pyramid surfaces, that you have an apex which is determined from the shape of the recess on the virtual formed by replacing the imaginary plane containing the pin section respectively pin section.

  The strain measuring device of the present invention is a strain measuring device for measuring strain generated in a subject using a polygonal cone-shaped recess formed in the subject, and the shape of the recess before and after the strain is generated in the subject. Each of the depression shape measuring means, and an arithmetic means for calculating strain from the amount of change in the shape of the depression measured by the depression shape measuring means. In the depression shape measuring means, a polygonal pyramid shaped depression is provided. The position of the vertex of the polygonal pyramid surface is measured, and the calculation means calculates the strain from the amount of change in the position of the vertex.

  Further, in the depression shape measuring means, the polygonal pyramid surface is replaced with a virtual plane including each polygonal pyramid surface, the depression shape is virtualized using the virtual plane, and the vertex of the polygonal pyramid plane is calculated from the virtual depression shape. It is also characterized in that the position of the apex of the polygonal pyramid surface is measured by specifying the position.

  According to the first aspect of the present invention, in the measurement method for measuring the strain generated in the subject, the step of measuring the shape of the concave depression generated in the subject at the first timing, and the first timing A step of measuring the shape of the dent at a second timing after a predetermined time, and a step of calculating strain from the amount of change in shape from the shape of the dent at the first timing to the shape of the dent at the second timing. It is possible to measure strain generated in a subject from one depression, enable measurement of strain in a minute region, and measurement of strain in the thickness direction of the subject. be able to.

  According to the invention described in claim 2, in the strain measuring method according to claim 1, by forming the depression into an indentation formed in the subject, the shape of the depression before the deformation occurs can be made substantially constant, Since the range of the shape change after the deformation can be easily assumed, the measurement of the hollow shape can be made more efficient.

  According to a third aspect of the present invention, in the strain measuring method according to the second aspect, the step of forming an indentation in the subject, and after the formation of the indentation, the residual stress generated in the subject with the formation of the indentation is measured. And the step of performing the residual stress removing process to remove the influence of the formation of the indentation on the measurement result of the strain.

  According to a fourth aspect of the present invention, in the strain measuring method according to the second or third aspect, the indentation has a polygonal pyramid surface as a polygonal pyramid-shaped depression, and the amount of movement of the apex of the polygonal pyramid surface in the indentation By calculating the strain based on this, it is possible to calculate the deformation amount of the shape deformation in the recess very easily, and the output of the strain measurement result can be speeded up.

  According to a fifth aspect of the present invention, in the strain measuring method according to the fourth aspect, each vertex of the polygonal pyramid surface is a virtual depression formed by replacing the polygonal pyramid surface with a virtual plane including the polygonal pyramid surface. By using the vertex determined from the shape, the vertex of the polygonal pyramid surface can be accurately specified, and the measurement error can be reduced and the measurement accuracy can be improved.

According to invention of Claim 6 , it is a distortion | strain measuring apparatus which measures the distortion which arose in the subject using the polygonal cone-shaped dent formed in the subject, Comprising: The shape of a dent before and after a strain | distortion arises in a subject Each of the depression shape measuring means, and an arithmetic means for calculating strain from the amount of change in the shape of the depression measured by the depression shape measuring means. In the depression shape measuring means, a polygonal pyramid shaped depression is provided. By measuring the position of the vertex of the polygonal pyramid surface and calculating the strain from the amount of change in the position of the vertex in the computing means, it is possible to provide a strain measuring apparatus that can measure the strain generated in the subject from one depression. . In particular, this strain measuring apparatus can measure strain in the thickness direction of the subject.

According to the seventh aspect of the present invention, in the strain measuring device according to the sixth aspect, in the depression shape measuring means, the polygonal pyramid surface is replaced with a virtual plane including the polygonal pyramid surface, and the depression is measured using the virtual plane. By imagining the shape and measuring the position of the vertex of the polygonal cone surface by specifying the position of the vertex of the polygonal cone surface from the virtual shape of the depression, the vertex of the polygonal cone surface can be accurately identified, It is possible to provide a strain measuring apparatus that can improve measurement accuracy by reducing measurement error.

  In the strain measuring method and the strain measuring apparatus of the present invention, the amount of change in the shape change of the recess caused by the deformation generated in the subject is measured using a single concave recess provided in the subject. Is used to measure strain generated in the subject.

  By using a single depression in this way, it is possible to perform strain measurement in a space-saving manner compared to conventional strain measurement using an indentation pair using two indentations, and in addition, a linear direction connecting the indentation pair In addition to measuring one-dimensional strain, three-dimensional strain and shear strain can be measured.

  The subject is not limited to a metal body, and may be a synthetic resin material such as plastic, a crystal material such as a semiconductor substrate, or wood as long as the shape of the concave can be maintained. Further, it may be a ceramic material as long as brittle fracture does not occur.

  The concave depression can use a scratch or the like generated during the processing of the subject, but can most easily be an indentation formed by pressing an indenter against the subject. When using an indentation, the subject needs to have plastic deformability so that an indentation can be formed.

  In this way, when an indentation is used as a depression, the shape before deformation of the subject can be a constant shape and the range of shape change after deformation can be assumed. The efficiency of measurement can be improved.

  In particular, when the specimen is a metal body, the residual stress is removed by annealing the specimen after the impression is formed on the specimen, and the residual stress generated in the specimen due to the formation of the impression is removed. It is desirable to keep it. By performing the residual stress removal process, the effect of residual stress due to the formation of indentations affects the deformation of the object, and the deformation state is different from the deformation state when there is no residual stress. Strain can be measured more accurately.

  A confocal microscope can be used for the measurement of the depression shape. In addition, it is not limited to the case where a hollow shape is measured using a confocal microscope, You may measure a hollow shape using the surface shape measuring device which used the ultrasonic wave and the laser. In addition, if the shape of the subject is large, fill the indentation with a resin material or the like, mold the indentation shape, transfer the indentation shape, and perform measurement using the transferred indentation shape. Also good.

  When measuring strain generated in a subject, as shown in the flowchart of FIG. 1, first, the shape of a recess provided in the subject is measured at a predetermined first timing with a confocal microscope or the like. (Step S1).

  Next, the shape of the previous depression is measured again with a confocal microscope or the like at a second timing after a predetermined time from the first timing (step S2).

  Next, the distortion in the depression when the shape of the depression at the first timing is changed to the shape of the depression at the second timing is calculated (step S3). The calculation of the strain in the depression can be performed, for example, by introducing a strain parameter for evaluating the strain and specifying the strain parameter using an analysis means such as a finite element method, or the first timing as described later. It can also be performed by calculating based on an appropriate calculation formula from the amount of change from the shape of the recess in the shape to the shape of the recess at the second timing.

  Next, the strain of the subject is calculated from the strain of the depression using a predetermined conversion formula (step S4).

  Thus, by calculating the strain generated in the subject based on the strain generated in the depression, the strain generated in the subject from a single depression can be calculated.

  In particular, when a reference side that does not change due to distortion generated in the subject is set in advance in the subject and the position of the reference side is unchanged at the first timing and the second timing, the distortion generated in the depression As well as rotation can be measured.

  Furthermore, when the depression shape is a polygonal pyramid shape, the depression can be composed of a plurality of polygonal pyramid surfaces, and distortion and rotation can be determined by evaluating the deformation amount of the shape deformation in the depression by the amount of movement of the apex of the polygonal pyramid surface. Can be evaluated very easily.

  Here, the displacement of an arbitrary point (x, y, z) in the subject is approximated by a linear function as shown by the following equation.

For example, when the indentation B formed on the subject A has a triangular pyramid shape as shown in FIG. 2, the four apexes (x ₁ , y ₁ , z ₁ ), (x ₂ , y ₂ , z ₂ ) of the indentation B are shown. ), (X ₃ , y ₃ , z ₃ ), (x ₄ , y ₄ , z ₄ ) are expressed by the following equations. 2A is a plan view of the indentation B formed on the subject A, and FIG. 2B is a cross-sectional view taken along the line XX of FIG.

From these equations, U _x is expressed as follows.

Similarly, _Uy is expressed as:

Similarly, U _z is expressed as:

From Equations 6 to 8, a _{0 to} a ₃ , b _{0 to} b ₃ , and c _{0 to} c ₃ are obtained by the following equations, respectively.

  Therefore, the following equation can be obtained.

  Therefore, the displacement of the indentation B having a triangular pyramid shape can be expressed by the following equation.

  Therefore, the displacement gradient tensor can be expressed by the following equation.

これにより、三角錐形状の圧痕Ｂのひずみε_ij及び回転ｗ_ijは次式で求めることができる。

Accordingly, the strain ε _ij and the rotation w _ij of the triangular pyramid-shaped indentation B can be obtained by the following equations.

While using the strain ε _ij and the rotation w _ij of the indentation B thus obtained, the strain and rotation generated in the subject A can be calculated from a predetermined conversion formula.

Specifically, for example, when the indentation is distorted by a load acting on the surface of the subject, the indentation strain in the load direction is ε _in-1 , and the indentation strain in the direction perpendicular to the load direction is ε _in-1 . _in-2 , where the strain of the indentation in the thickness direction of the subject is ε _in-3 , the strain of the subject in the load direction ε ₁ , the strain of the subject in the direction perpendicular to the load direction ε ₂ , the subject in the thickness direction Ε ₃ can be calculated by the following equation when the subject is elastically deformed.

  Further, when the subject is plastically deformed, it can be calculated by the following equation.

  Thus, when measuring strain using the apex provided in the indentation B, the indentation B is preferably a polygonal inferior shape, in particular, by making it a triangular pyramid shape as shown in FIG. Strain can be calculated with the least amount of calculation. The indentation B is not limited to a triangular pyramid shape, and may be a quadrangular pyramid shape or a pentagonal pyramid shape.

  In particular, since the indentation B is provided with an apex inside the indentation, and the strain in the thickness direction of the subject can be calculated using the position of the apex, the indentation is preferably conical.

  Furthermore, in the indenter for forming the indentation, a plurality of apexes may be provided inside the indentation B ′ as shown in FIG. 3 by using a partial cone-shaped indenter having a flat surface at the tip. In this way, the strain and / or rotation in the thickness direction of the subject A can be calculated more accurately by using a plurality of vertices provided inside the indentation B ′. 3A is a plan view of the indentation B ′ formed on the subject A, and FIG. 3B is a YY cross-sectional view of FIG. 3A.

  FIG. 4 is a schematic diagram of a strain measuring apparatus according to the present embodiment. The strain measuring apparatus according to the present embodiment is configured to measure strain generated in a metal feeding pipe 10 to which a pressurized high-temperature liquid is fed. Measuring.

  The feeding pipe 10 is formed with an indentation b for strain measurement at a predetermined position. In particular, after forming the indentation b on the feeding pipe 10, the feeding pipe 10 is subjected to an annealing process to obtain an indentation b. The residual stress generated in the supply pipe 10 due to the formation of is removed. In the present embodiment, the indentation b has a triangular pyramid shape, and is provided on the upper surface of the supply pipe 10 at a predetermined interval.

  The strain measuring device includes a scanning eutectic spot laser microscope 11 which is a depression shape measuring means for measuring the shape of a depression of the indentation b provided in the supply pipe 10, and an indentation measured by the scanning eutectic point laser microscope 11. and an arithmetic unit 12 composed of a personal computer, which is an arithmetic means for calculating strain from the shape of the depression b. For convenience of explanation, the “scanning eutectic point laser microscope” will be simply referred to as “microscope” in the following.

  In this embodiment, the microscope 11 is mounted in a suspended state on a support rod 13 provided in parallel with the feed pipe 10, and the objective lens of the microscope 11 is opposed to the indentation b of the feed pipe 10. That is, the rear end portion of the microscope 11 is provided with a suspending portion 14 that is attached to the support rod 13 in a suspended state, and is attached to the support rod 13 in a suspended state via the suspending portion.

  The support rod 13 is preferably made of a material with small fluctuations in expansion or contraction due to temperature fluctuations. In this embodiment, the supply pipe 10 itself is provided in a temperature-controlled environment, so that it depends on the temperature. Steel H steel is used because the support rod 13 is not easily deformed.

  Rolling rollers 15 and 15 that are even in contact with the upper flat surface of the support rod 13 are rotatably mounted on the suspension 14, and the suspension roller 14 is rotated by rotating the rolling roller 15 with a drive motor (not shown). Is movable along the longitudinal direction of the support rod 13, and the microscope 11 is movable along the suspended portion.

  Further, the hanging part 14 is provided with a positioning sensor 16 for detecting a positioning mark (not shown) provided on the support rod 13, and the movement of the microscope 11 is stopped by the detection of the mark by the positioning sensor 16. The indentation b is measured with the microscope 11.

  The positioning sensor 16 may be an optical sensor or a magnetic sensor, and an appropriate sensor may be used. For example, when an optical sensor is used as the positioning sensor 16, a reflective material can be used for the mark, and the reflected light from the mark is detected by the positioning sensor 16. When a magnetic sensor is used as the positioning sensor 16, a magnet can be used as the mark, and the magnetism due to the mark is detected by the positioning sensor 16.

The computing unit 12 constituted by a personal computer stores a strain measurement program for measuring strain generated in the supply pipe 10, and by executing this strain measurement program, the strain is measured as described later. Yes.

  In particular, the calculation unit 12 controls not only the microscope 11 but also the suspension 14 and the positioning sensor 16 based on the strain measurement program, and automatically performs strain measurement.

  Hereinafter, strain measurement by the strain measurement program will be described based on the flowchart of FIG.

  Note that the storage unit of the calculation unit 12 stores in advance the shape of each indentation b immediately after the use of the supply pipe 10 is started as the first timing, and is stored in advance for convenience of explanation. The shape of the indentation b is referred to as “initial shape”. Here, the data stored as the initial shape is coordinate data of four vertices in the indentation b having a triangular pyramid shape, and is detected by the microscope 11.

  When the calculation unit 12 detects that the preset strain measurement timing has been reached (step T1), it moves the microscope 11 onto the indentation b to be measured first (step T2). This timing is the second timing. The end of movement is determined by detecting a predetermined mark by the positioning sensor 16 (step T3).

  When the microscope 11 is placed at a predetermined position on the indentation b, the calculation unit 12 measures the indentation b with the microscope 11 (step T4).

  The image data of the indentation b measured by the microscope 11 is input to the calculation unit 12 (step T5), and the calculation unit 12 uses the input image data to form three indentations b having a triangular pyramid shape. It is assumed that the triangular pyramid surface equation and the bottom surface equation are specified by the least square method or the like, and the indentation b is formed on the virtual plane specified by these plane equations (step T6).

  Next, the computing unit 12 virtually imagines the shape of the indentation b from the equation of each plane that is the virtual plane information at step T6 (step T7), and the triangle that constitutes the indentation b from the virtual shape information of the indentation b. The position of the apex of the cone surface is specified (step T8).

  Here, the virtual shape of the indentation b in step T7 is an equation of each side specified by the intersection of the planes from the equation of each plane, and the equation of the six sides of the indentation b of the triangular pyramid shape is obtained. It is to identify. By specifying these six side equations, the shape of the indentation b is specified.

  The specification of the position of the apex of the triangular pyramid surface in step T8 specifies the coordinate data of the apex of the triangular pyramid surface using the equations of the three sides that intersect each other among the equations of the six sides. That is.

  In this way, by obtaining the coordinate data of the apex of the indentation b having a triangular pyramid shape using a virtual plane, the coordinate data of the apex directly from the image data of the indentation b measured by the microscope 11 is obtained. Therefore, the measurement error can be reduced and the measurement accuracy can be improved.

  The calculation unit 12 calculates the distortion and rotation of the indentation b from the coordinate data of the four apexes of the identified indentation b and the coordinate data of the apex of the initial shape based on the above-described calculation formula (step T9). Here, the rotation can be calculated by using the support rod 13 as a reference side with respect to the supply pipe 10. In the present embodiment, the support rod 13 is used as a reference side, but a reference side may be provided in the feed pipe 10 itself.

  After calculating the strain and rotation of the indentation b, the calculation unit 12 performs conversion using a predetermined conversion formula to calculate the strain and rotation generated in the supply pipe 10 that is the subject (step T10). The calculated strain and rotation are stored in a storage means such as a memory, and the measurement of the strain and rotation for one indentation b is completed.

  After measuring the strain and rotation for a given indentation b, the calculation unit 12 determines whether the measurement of strain and rotation for all the indentations b has been completed (step T11), and if there is an unmeasured indentation b, the calculation is performed. The unit 12 returns to step T2 to move the microscope 11 onto the indentation b to be measured next. On the other hand, when the measurement of strain and rotation for all the indentations b has been completed, the calculation unit 12 moves the microscope 11 to a predetermined standby position and is in a standby state (step T12).

It is a flowchart explaining how to measure strain according to the present invention. (A) is a top view of an indentation, (b) is XX sectional drawing of (a). (A) is a top view of the indentation of a modification example, (b) is YY sectional drawing of (a). It is explanatory drawing of the distortion measuring apparatus which concerns on embodiment of this invention. It is a flowchart explaining operation | movement of the distortion | strain measuring apparatus which concerns on embodiment of this invention.

Explanation of symbols

b Indentation
10 Supply piping
11 Scanning eutectic point laser microscope
12 Calculation unit
13 Supporting cage
14 Suspended lower part
15 Rolling roller
16 Positioning sensor

Claims (7)

A measurement method for measuring strain generated in a subject,
Measuring the shape of the concave depression generated in the subject at a first timing;
Measuring the shape of the depression at a second timing after a predetermined time from the first timing;
A strain measurement method comprising: calculating the strain from a change amount of a shape change from the shape of the recess at the first timing to the shape of the recess at the second timing.   The strain measurement method according to claim 1, wherein the recess is an indent formed in the subject. Forming the indentation in the subject;
The strain measuring method according to claim 2, further comprising a step of performing a residual stress removing process for removing a residual stress generated in the subject with the formation of the indentation after the formation of the indentation. The indentation has a polygonal cone surface as a polygonal cone-shaped depression,
The strain measurement method according to claim 2 or 3, wherein the strain is calculated based on a movement amount of a vertex of the polygonal pyramid surface in the indentation.   5. Each vertex of the polygonal pyramid surface is a vertex determined from the shape of a virtual depression formed by replacing the polygonal pyramid surface with a virtual plane including the polygonal pyramid surface, respectively. Strain measurement method. A strain measuring device that measures strain generated in the subject using a polygonal cone-shaped depression formed in the subject,
Indentation shape measuring means for measuring the shape of the indentation before and after distortion occurs in the subject,
Arithmetic means for calculating the strain from the amount of change in shape in the shape of the depression measured by the depression shape measuring means;
With
The strain measuring device wherein the depression shape measuring means measures the position of the apex of the polygonal pyramid surface in the polygonal pyramid shaped depression, and the computing means calculates the strain from the amount of change in the position of the apex. In the hollow shape measuring means,
Replacing each of the polygonal pyramid surfaces with virtual planes including the polygonal pyramidal surfaces,
Using this virtual plane, virtualize the shape of the depression,
The strain measuring device according to claim 6, wherein the position of the apex of the polygonal pyramid surface is measured by specifying the position of the apex of the polygonal pyramid surface from the virtual shape of the depression.

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