JP2013221778A - Non-contact distortion measuring device and non-contact distortion measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact distortion measuring device and a non-contact distortion measuring method that secure a sufficient measurement range from an elastic deformation area to a plastic deformation area for one imaging part, and can highly accurately measure distortion at least in the elastic deformation area.SOLUTION: According to the present invention, in image data of a test piece 2 captured by an imaging part 3, two reference points Mand Min an imaging visual field 6 of the imaging part 3 are used as calculation data to calculate a predetermined physical quantity ε about distortion of the test piece 2. When at least one of two reference points Mand Mused as the calculation data arrives at a predetermined setting area or a value based on positions of areas of the two reference points arrives at a predetermined setting value, a reference point 23 to be used as the calculation data is switched over to two reference points Mand Mpresent in the imaging visual field 6 and the predetermined physical quantity ε is calculated from these switched-over two reference points Mand M.

Description

  The present invention relates to a non-contact type strain measuring apparatus and a non-contact type strain measuring method for measuring the strain of a test piece in a non-contact manner in a tensile test or the like.

  Conventionally, a non-contact strain measuring device disclosed in Patent Document 1 is known. This non-contact type distortion measuring apparatus includes an imaging unit such as a video camera, and an arithmetic unit that obtains distortion of the test piece from the image data of the test piece acquired by the imaging unit. In the non-contact distortion measuring apparatus, the imaging unit images a test piece with two marked marks. Then, the calculation unit detects the change amount of the interval between the marked marks from the image data obtained by the imaging unit, and obtains the distortion of the test piece between the marked marks based on the change amount of the interval.

  When accurately measuring the strain (see FIG. 12) in the elastic deformation region of the test piece with this non-contact strain measuring apparatus, an imaging unit with high resolution is used. In such an imaging unit with high resolution, the imaging field of view is narrowed, so that even if the distortion (elongation) generated in the test piece is small, the marked mark is out of the imaging field of view. For this reason, in the non-contact type strain measuring apparatus, the measurable strain range (the range of the horizontal axis in the nominal stress-nominal strain diagram: see FIG. 12) is narrow.

  Here, in order to widen the measurable distortion range, it is conceivable to use an imaging unit having a wide imaging field so that the mark mark is not easily removed from the imaging field even when the distortion of the test piece progresses. However, since the resolution of such an imaging part with a wide imaging field of view is low, the distortion in the elastic deformation region cannot be measured with high accuracy.

  Therefore, Patent Document 2 proposes a non-contact strain measuring apparatus that can measure strain in an elastic deformation region with high accuracy and can measure a wide range of strain including a plastic deformation region.

  This non-contact distortion measuring apparatus includes two imaging units, a calculation unit, and a selection unit. The calculation unit detects a displacement amount of the distance between the two marked marks from image data obtained by imaging the two marked marks attached to the surface of the test piece with the imaging unit. Subsequently, the calculation unit obtains the distortion between the two marked marks from the amount of displacement. The selection unit selects one of the image data from each imaging unit according to a preset criterion and supplies the selected image data to the calculation unit.

  Specifically, each imaging unit includes an imaging device and an optical system for forming an optical image (light image) of the test piece on the light receiving surface of the imaging device. One image pickup unit (first image pickup unit) has a higher resolution than the other image pickup unit (second image pickup unit). That is, the first imaging unit has a narrower imaging field of view than the second imaging unit. The selection unit first supplies the image data from the first imaging unit to the calculation unit, and calculates at a timing when at least one of the two marked marks on the test piece deviates from the imaging field of view of the first imaging unit due to the progress of distortion. The image data supplied to the image capturing unit is switched from image data from the first image capturing unit to image data from the second image capturing unit.

  In the non-contact strain measuring apparatus described above, first, the strain in the elastic deformation region is accurately measured by the image data acquired by the first imaging unit having a high resolution. In the non-contact distortion measuring apparatus, the imaging unit is switched as the distortion progresses, and a wide range of distortion is measured. That is, in the non-contact type strain measuring apparatus, in addition to the strain in the elastic deformation region, the strain in the plastic deformation region is also measured.

Japanese Patent Application Laid-Open No. 11-132731 JP 10-221025 A

  In the non-contact distortion measuring apparatus including the plurality of imaging units described above, optical adjustment between the plurality of imaging units (for example, the optical axis of the optical system of each imaging unit is matched, the optical system of each imaging unit is However, it is difficult to perform optical adjustment between the plurality of imaging units so that sufficient measurement accuracy can be obtained.

  Therefore, in view of the above problems, the present invention can measure at least the strain in the elastic deformation region with high accuracy while ensuring a sufficient measurement range from the elastic deformation region to the plastic deformation region with one imaging unit. It is an object of the present invention to provide a non-contact strain measuring apparatus and a non-contact strain measuring method.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, according to one aspect of the present invention, there is provided a non-contact type strain measuring apparatus that measures a predetermined physical quantity related to the strain of a test piece in a test piece having a plurality of test points provided on a surface thereof, in a non-contact manner. In the image data of the test piece acquired by the imaging unit and the test piece acquired by the imaging unit, the calculation is performed on two target areas that are one of a plurality of target points and within the imaging field of the imaging unit. A measurement value calculation unit that obtains the predetermined physical quantity by using it as data. Then, the measurement value calculation unit, when at least one of the two gage areas used as calculation data for obtaining the predetermined physical quantity reaches a predetermined setting area, or of the two gage areas When the value based on the position reaches a predetermined set value, the gauge area used as the calculation data is switched to two gauge areas in the imaging field of view.

  And in another aspect of the present invention, there is provided a non-contact type strain measuring method for measuring a predetermined physical quantity related to the strain of the test piece in a test piece having a plurality of test points provided on the surface thereof, wherein In the image data of the test piece acquired by the imaging unit that images the test piece, the calculation target is a target region including one or a plurality of target points and two target regions in the imaging field of view of the imaging unit. A first physical quantity derivation step for obtaining the predetermined physical quantity by using the two physical mark regions used as operation data for obtaining the predetermined physical quantity in the first physical quantity derivation step in the image data; The target area used as the calculation data when at least one of the two reaches a predetermined setting area or when a value based on the position of the two reference area reaches a predetermined setting value Switching the two gage area is within the imaging field of view, characterized in that these switching two gage region was and a second physical quantity deriving step of determining the predetermined physical quantity.

  In the non-contact type strain measuring apparatus and the non-contact type elongation measuring method having such a configuration, two in the imaging field used as calculation data for obtaining the predetermined physical quantity as the strain of the test piece progresses. When at least one of the mark areas reaches a predetermined setting area, or when a value based on the position of the two mark areas reaches a predetermined setting value, the mark used as the calculation data at that time By switching to two gauge points in the imaging field of view, a single imaging unit ensures a sufficient measurement range from the elastic deformation region to the plastic deformation region, and at least measures distortion in the elastic deformation region with high accuracy. can do. That is, while the strain generated in the test piece is small (at least between the elastic deformation regions), the strain of the test piece is obtained with high precision using the two predetermined gage regions in the imaging field of view as calculation data. Then, before the distortion of the test piece cannot be measured using these two gauge regions due to the progress of the distortion, the two gauge points used for the calculation data are switched to the gauge area present in the imaging field at that time. Thus, subsequent strain measurement (measurement of strain in the plastic deformation region) is also possible.

  Note that the test piece whose predetermined physical quantity is measured by the above-described non-contact type strain measuring device or non-contact type strain measuring method may have a plurality of randomly arranged marks on its surface, A plurality of mark points that are continuously arranged at predetermined intervals along the direction may be provided on the surface.

  In another aspect, the above-described non-contact distortion measuring apparatus is configured such that the position of the imaging unit is set so that the two target areas are within the imaging field of view as the two target areas move. You may further provide the drive part which controls these.

  According to this configuration, when the test piece is distorted (extends) so that the two reference points used as calculation data move in the same direction as the distortion progresses, the imaging field of view is adjusted in accordance with the progress of the distortion of the test piece. It is possible to follow the corresponding region of the test piece.

  As described above, according to the present invention, a single imaging unit can ensure a sufficient measurement range from the elastic deformation region to the plastic deformation region, and can measure at least the strain in the elastic deformation region with high accuracy. A mold strain measuring device and a non-contact strain measuring method can be provided.

It is a figure which shows the structure of the non-contact-type distortion measuring apparatus in 1st Embodiment. It is a figure which shows the positional relationship of a camera visual field and each mark according to progress of distortion of a test piece in 1st Embodiment. It is a figure for demonstrating the calculation method which calculates | requires the elongation rate of a test piece using two mark points. It is a flowchart which shows operation | movement of the non-contact-type strain elongation measuring apparatus in 1st Embodiment. It is a figure which shows the structure of the non-contact-type distortion measuring apparatus in 2nd Embodiment. It is a figure which shows the positional relationship of a camera visual field with each progression of a test piece, and each mark in 2nd Embodiment. It is a flowchart which shows operation | movement of the non-contact-type distortion measuring apparatus in 2nd Embodiment. It is a figure for demonstrating the measurement of the predetermined | prescribed physical quantity regarding distortion at the time of using the test piece by which the some mark was arrange | positioned at random. It is a figure which shows the positional relationship of a camera visual field with each progression of a test piece, and each mark in other embodiment. It is a figure for demonstrating the progress of the distortion of the test piece in other embodiment, and the switching of the selected reference point accompanying this. It is a figure for demonstrating the progress of the distortion of the test piece in other embodiment, and the switching of the selected reference point accompanying this. It is a nominal stress-nominal strain diagram.

  Hereinafter, a first embodiment according to the present invention will be described with reference to FIGS. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably.

  A non-contact strain measuring apparatus (hereinafter, also simply referred to as “strain measuring apparatus”) 1 according to the present embodiment measures a predetermined physical quantity related to the strain of the test piece 2 in a strength test such as a tensile test. In the present embodiment, the elongation ε of the test piece 2 is measured as the predetermined physical quantity.

  The predetermined physical quantity measured by the strain measuring device 1 is not limited to the elongation ε of the test piece 2. The predetermined physical quantity may be an amount related to the strain of the test piece 2, and may be, for example, the strain of the test piece 2 itself, the strain rate, the elongation at break, or the like.

  The test piece (measuring object, subject) 2 is a measuring object and may be any material. The test piece 2 is, for example, a metal material such as a rolled steel plate, a resin material such as rubber or plastic, and concrete.

  The distortion generated in the test piece 2 is given by applying a predetermined external force to the test piece 2. For example, in the tensile test, the test piece 2 is clamped at both ends 21 and 22 by a chuck (gripping tool) for fixing the test piece 2 in a known tensile tester (not shown). And the external force of the direction (tensile direction: the up-down direction in FIG. 1) which the said both ends 21 and 22 space apart is applied to the both ends 21 and 22 of the test piece 2 with the said tensile tester. That is, an external force in the tensile direction acts on the test piece 2. Thereby, distortion (elongation) occurs in the test piece 2. The external force acting on the test piece 2 in the direction in which both ends 21 and 22 of the test piece 2 are separated is given by pulling the lower end 22 of the test piece 2 downward while pulling the upper end 21 of the test piece 2 upward. .

  The test piece 2 includes a plurality of marks 23, 23,. Specifically, on the surface 24 of the test piece 2, a plurality of (for example, four in the example shown in FIG. 1) marks 23, 23,... Are continuously spaced at a predetermined interval along the pulling direction. Is provided. Each of the mark points 23 in the present embodiment is a so-called circular dot mark, but may have another shape (for example, a polygon such as a square or a cross).

  The plurality of marks 23, 23,... Are provided so as to be within the camera field of view (imaging field of view) of the camera device 3 in the pulling direction.

  The distortion measuring device 1 includes a camera device (imaging unit) 3, an image recording unit 4, and an image processing unit 5.

  The camera device (imaging unit) 3 shoots (images) the test piece 2 as a subject in order to monitor (observe and monitor) the test piece 2. For example, the camera device 3 includes a photographing optical system 31, an image sensor 32, and an image generation unit 33. This camera device 3 is arranged so that a plurality of marks 23, 23,... Provided on the test piece 2 clamped by the chuck of the tensile tester can be imaged. The camera device 3 may be a monochrome camera or a color camera. The camera device 3 may be a digital still camera that generates a still image, or may be a digital video camera that generates a moving image.

  The photographing optical system 31 is an optical system for forming an optical image (light image) of the test piece 2 on the light receiving surface of the image sensor 32.

  The image sensor 32 photoelectrically converts the optical image of the test piece 2 formed on the light receiving surface by the photographing optical system 31 and outputs a signal corresponding to the amount of light in the optical image (a signal sequence of signals received in units of pixels). It is a circuit that generates and outputs this signal to the image generation unit 33. For example, the image sensor 32 includes a plurality of pixels (photoelectric conversion elements) arranged in a two-dimensional array, and is a CCD type or CMOS type image sensor or the like.

  The image generation unit 33 performs a known image process such as a black level correction process, a pixel interpolation process, or a shading correction process on the signal obtained by the imaging element 32, for example, to thereby generate a digital image signal (test piece 2). Is generated and output.

  The image recording unit 4 records (accumulates and stores) the image signal output from the camera device 3 (specifically, the image generation unit 33). The image recording unit 4 is, for example, a hard disk or a memory.

  The image processing unit 5 is a circuit for obtaining the elongation rate of the test piece 2 from the image data of the test piece 2 acquired by the camera device 3. For example, a microcomputer having a microprocessor, a storage element, and peripheral circuits thereof Consists of. In this embodiment, the image processing unit 5 functionally includes a measurement value calculation unit 50.

  The measurement value calculation unit 50 functionally includes a selection point setting unit 51 and a calculation unit 52. The measured value calculation unit 50 uses the two test points 23 and 23 in the camera visual field 6 in the image data as the calculation data from the image data of the test piece 2 acquired by the camera device 3. A predetermined physical quantity (elongation rate ε in this embodiment) is obtained.

  The measurement value calculation unit 50 is functionally configured in the microcomputer by, for example, executing an elongation measurement program that calculates the elongation ε of the test piece 2 based on the image data acquired by the camera device 3.

  In the case where such an elongation measurement program is not stored in the microcomputer, for example, a flexible disk drive device or a CD-ROM drive device is recorded from a recording medium such as a flexible disk or a CD-ROM on which the program is recorded. The strain measurement apparatus 1 may be configured to be installed in the microcomputer via an external storage device such as the above. The strain measuring device 1 may be configured such that the elongation measuring program is downloaded from a server computer that manages the elongation measuring program via a communication network and a communication interface device (such as a network card).

  Moreover, although the distortion measuring apparatus 1 of this embodiment has obtained the image data of the test piece 2 from the camera apparatus 3 in substantially real time, it is not limited to such an aspect. For example, the strain measuring apparatus 1 is configured such that image data for measuring the elongation ε of the test piece 2 is input to the strain measuring apparatus 1 via an external storage device by a recording medium on which this data is recorded. May be. Further, the strain measuring apparatus 1 may be configured such that the data is input to the strain measuring apparatus 1 from a server computer that manages the data via a communication network and a communication interface apparatus.

The selection point setting unit 51 includes a plurality (four in the example of the present embodiment) of points in the camera field of view (imaging field of view) 6 of the camera device 3 in the image data of the test piece 2 recorded in the image recording unit 4. Are selected (extracted) from two predetermined marks 23, 23, and set as selected marks (first selected mark M ₁ , second selected mark M ₂ ). To do.

The selection point setting unit 51 is configured such that at least one of the first and second selection standard points M ₁ and M ₂ reaches a predetermined setting region 6a (or 6b) as the test piece 2 extends (distorts). Then, the two target points 23 and 23 existing in the camera visual field 6 at that time are selected again, and these are selected as new selected reference points (third selected reference point M ₃ and fourth selected reference point M _4). ).

The setting area 6a (or 6b) is an area set in the vicinity of both ends of the camera visual field 6 in the pulling direction of the test piece 2. Specifically, the setting area 6a (or 6b) is set to an area adjacent to the edge so as to include the edge of the camera field 6 in the pulling direction (the boundary line between the inside and the outside of the camera field 6). It is an area. Specifically, the setting area 6a (or 6b) is an area set inside or outside the edge so as to include the edge of the camera visual field 6 in the pulling direction. The setting area 6a of the present embodiment is set outside the edge so as to include the edge of the camera visual field 6 in the pulling direction. Therefore, when at least one of the first and second selected standard points M ₁ and M ₂ reaches the setting region 6a, the selected point setting unit 51 has two standard points that are present in the camera visual field 6 at that time. 23 and 23 are selected again, and these are set as new selected reference points (third selected reference point M ₃ , fourth selected reference point M ₄ ). That is, when at least one of the first and second selected reference points M ₁ and M ₂ deviates from the camera field of view 6 (when moved outside the camera field of view 6), the selected point setting unit 51 Then, the two reference points 23 and 23 existing in the camera visual field 6 are selected again, and these are set as the third selected reference point M ₃ and the fourth selected reference point M ₄ .

When the setting area 6b is set inside the edge so as to include the edge of the camera field of view 6 in the pulling direction, both the first and second selected reference points M ₁ and M ₂ are Even if it is within the camera field of view 6, two selected reference points are reset. That is, when the setting area 6b is set in the camera visual field 6, the selection point setting unit 51 selects the two reference points 23 and 23 (first and second selection reference points M ₁ and M ₂ ) previously selected. The selected reference point is switched to the third and fourth selected reference points M ₃ and M ₄ immediately before the camera field 6 deviates from the camera field of view. Specifically, the selection point setting unit 51, when at least one of the first and second selection standard marks M ₁ and M ₂ reaches the setting area 6b in the camera field of view 6, the camera field of view 6 at that time. The two marks 23 and 23 located inside and inside the _two selected marks M ₁ and M ₂ in the pulling direction (center side of the camera visual field 6) are selected again. Then, the selection point setting unit 51 sets these as new selection standard points (third selection standard point M ₃ and fourth selection standard point M ₄ ).

For example, in the example shown in FIGS. 2A to 2C, the selection point setting unit 51 includes the uppermost mark 23 in the camera visual field 6 and the lowermost mark 23. And select. Subsequently, the selected point setting unit 51, the upper gauge 23 and sets the first selection and gauge M _1, sets the lower gauge 23 and the second selection gauge M _2. In this way, by selecting the uppermost gauge point 23 and the lowermost gauge point 23 and increasing the interval between the two selected gauge points, the elongation rate ε (distortion) of the test piece 2 is accurately obtained. be able to. That is, the selection point setting unit 51 ensures the elongation ε (distortion) of the test piece 2 with high accuracy by ensuring a sufficient distance between the first selection standard point M ₁ and the second selection standard point M _2. Can be sought.

Then, when the test piece 2 extends and at least one of the first and second selected reference points M ₁ and M ₂ is out of the camera field, the selection point setting unit 51 is in the camera field 6 at that time. From the plurality (two in the present embodiment) of the mark points 23, 23,..., The mark point 23 located on the uppermost side and the mark point 23 located on the lowermost side are selected. Subsequently, the selected point setting unit 51, the two reference points 23, 23 were selected, and sets the upper gauge 23 to the third selection gauge M _3, the lower side of the gauge 23 set to fourth selection gauge M _4.

The calculation unit 52 obtains the elongation ε of the test piece 2 using the two selected standard points M ₁ and M ₂ (or M ₃ and M ₄ ) set by the selection point setting unit 51. That is, the calculation unit 52 uses the two selected standard points M ₁ and M ₂ (or M ₃ and M ₄ ) set by the selection point setting unit 51 as calculation data. Details will be described below. The arithmetic unit 52 of the present embodiment, two selection gauge M _1, M 2 _(or M _3, M ₄₎ using a seek elongation ε of the test piece 2, but is not limited thereto. The calculation unit converts a small area including each of the selected standard points M ₁ and M ₂ (or M ₃ and M ₄ ) into a first selected standard area and a second selected standard area (or a third selected standard area). In addition, the following processing may be performed as the fourth selected standard area).

Calculation unit 52, when the selection point setting unit 51 sets the first selection gauge M ₁ and the second selection gauge M _2, from the image data of the external force before the test piece 2, the first selection gauge An interval (reference length) L ₀ between M ₁ and the second selected reference point M ₂ is obtained (see FIG. 3A). This interval (distance) is based on, for example, the number of pixels between the optical image of the first selected standard point M _{1 and} the optical image of the second selected standard point M ₂ formed on the light receiving surface of the image sensor 32. Is required. Specifically, the arithmetic unit 52, the pixel distance between the first selected target point M ₁ of the center of gravity (center) position and the second selection gauge M ₂ centroid (center) position, existing between these gravity center position Find based on the number. Each mark 23 (dot pattern) is detected based on a difference in luminance in an optical image formed on the light receiving surface of the image sensor 32.

Next, the calculation unit 52 calculates the first selected reference point M ₁ (first) from the image data of the test piece 2 before the external force action and the image data of the test piece 2 in a state where distortion occurs after the external force action. Displacement amount (first displacement amount) ΔL _{1 of} the first selected reference point M ₁ ) and displacement amount (first position) of the second selected reference point M ₂ (centroid position of the _second selected reference point M ₂ ). 2 displacement amount) ΔL ₂ is obtained (see FIG. 3B). Then, the arithmetic unit 52, these reference length L _0, determine the elongation of the test piece 2 epsilon using equation (1) below from the first displacement amount [Delta] L _1, and a second displacement amount [Delta] L _2.

ε = (ΔL ₁ + ΔL ₂ ) / L ₀ (1)
This equation (1) is obtained as follows.

The distance between the first selected target point M ₁ in the image data of the external force before the test piece 2 and the second selected target point M ₂ a (interval) and L _0, the test in a state where distortion occurs after external force When the first selection gauge M ₁ in the piece 2 of the image data a distance between the second selection gauge M ₂ and L _10, the elongation epsilon, is given by the following equation (2).

ε = (L ₁₀ −L ₀ ) / L ₀ (2)
Here, when the first displacement amount before and after the external force action is ΔL ₁ and the second displacement amount is ΔL ₂ , the following equation (3) is established.

L ₁₀ = ΔL ₁ + L ₀ + ΔL ₂ (3)
The above equation (1) is derived from these equations (2) and (3).

It should be noted that ΔL ₁ and ΔL ₂ are positive values when the first selected reference point M ₁ and the second selected reference point M ₂ are displaced in directions away from each other in the camera visual field 6 of the camera device 3. Yes, ΔL ₁ and ΔL ₂ when displaced in the same direction in the camera shadow visual field 6 are calculated as a positive value when the displacement amount is large and a negative value when the displacement amount is small.

The calculation unit 52 of the present embodiment obtains the elongation ε using the above equation (1), but is not limited to this, and for example, obtains the elongation ε using the above equation (2). May be. In this case, the calculation unit 52 obtains distances L ₀ and L ₁₀ between the first selected standard point M ₁ and the second selected standard point M ₂ before and after the external force action, and calculates these L ₀ and L ₁₀ as described above. Substitute into equation (2).

In addition, when the selection point setting unit 51 newly sets a selected reference point (that is, when the third selection reference point M ₃ and the fourth selection reference point M ₄ are set), the calculation unit 52 is the same as above. a manner, the image data of the external force before the test piece 2, the third distance (reference length) with a selected gauge M ₃ and the fourth selection gauge M ₄ obtains the L ₂₀ (see FIG. 2 (C) ). Then, the selected point setting unit 51 determines the displacement of the _third selected reference point M ₃ from the image data of the test piece 2 before the external force action and the image data of the test piece 2 in a state where the distortion is generated after the external force action. An amount (third displacement amount) ΔL ₃ and a displacement amount (fourth displacement amount) ΔL _{4 of} the fourth selected reference point M ₄ are obtained. Then, the arithmetic unit 52, these reference length _{L 20,} third displacement [Delta] L _3, and obtains the elongation of the test piece 2 epsilon using equation (1) above from the fourth displacement [Delta] L _4. The reference length L ₂₀ is substituted for L ₀ in the above equation (1), and the third displacement amount ΔL ₃ and the fourth displacement amount ΔL ₄ are substituted for ΔL ₁ and ΔL ₂ in the above equation (1). To do.

  The calculation unit 52 outputs the elongation ε of the test piece 2 obtained as described above to an external output device (not shown) such as a display device such as a monitor or a printing device.

  Next, the operation of the distortion measuring apparatus 1 of the present embodiment will be described. FIG. 4 is a flowchart showing the operation of the distortion measuring apparatus 1 in the first embodiment.

  As preparation for the elongation rate determination, first, a plurality of gauge points 23, 23,... Are provided on the surface 24 of the test piece 2. The test piece 2 provided with the mark 23 is placed on a tensile tester or the like.

At this time, the test piece 2 of the present embodiment, the distance between both ends gauge marks 23, 23 in the pulling direction of the test piece 2 (first selection gauge M ₁ and the second selected target point M ₂₎ Is set so that the strain (elongation ε) of the entire elastic deformation region in the nominal stress-nominal strain diagram (see FIG. 12) can be measured.

  When the tensile test is started, photographing of the test piece 2 by the camera device 3 is started, and image data (image signal) is recorded (accumulated) in the image recording unit 4 (step S11). In addition, the imaging | photography with the camera apparatus 3 is started before the external force action to the test piece 2. FIG.

Subsequently, the selection point setting unit 51 includes a plurality of reference points 23, 23 in the camera visual field 6 in the image data recorded in the image recording unit 4 (specifically, image data before an external force is applied to the test piece 2). ... the a in either of two reference points 23, 23 big most interval selection (extraction) that sets them to the first selection gauge M ₁ and the second selection reference points M ₂ (step S12) . When these first selection gauge M ₁ and the second selection gauge M ₂ is set, the arithmetic unit 52, image data recorded in the image recording section 4 (more specifically, the image data before the external force acting from the latest image data after external force), the spacing L ₀ between the first reference points M ₁ in the test piece 2 before the external force acts and the second reference points M _2, the first displacement of the front and rear external force An amount ΔL ₁ and a second displacement amount ΔL ₂ are obtained. And the calculating part 52 calculates | requires elongation rate (epsilon) of the test piece 2 using these and said Formula (1) (step S13), and outputs the calculated elongation rate (epsilon). As described above, in the strain measuring apparatus 1 according to the present embodiment, first, by selecting the first selected standard point M ₁ and the second selected standard point M ₂ having a large interval before the external force is applied to the test piece 2. The strain (elongation ε) in the elastic deformation region in the nominal stress-nominal strain diagram can be measured with high accuracy.

The selection point setting unit 51 determines whether one of the first and second selection standard points M ₁ and M ₂ has reached the setting area 6a, that is, the first and second selection standard points M ₁ and M _2. It is determined whether or not both are within the camera visual field 6 (step S14). Selecting point setting unit 51 determines that the first at least one of the selected reference points M ₁ and the second selection reference points M ₂ and elongation test piece 2 is out of the camera view 6 (reaching the set region 6a) Then (step S14: Yes), the two benchmarks 23 and 23 used as calculation data for obtaining the elongation rate ε are changed from the first and second selected benchmarks M ₁ and M ₂ to the third and fourth selected markers. Switching to points M ₃ and M ₄ (resetting) (step S15). Specifically, the selection point setting unit 51 uses the first and second selection standard points M ₁ and M _{2 in the} latest image data recorded in the image recording unit 4 (or taken by the camera device 3). When at least one of them deviates from the camera visual field 6 (arrives at the setting area 6a), an image before the application of external force to the test piece 2 from among the plurality of marks 23, 23,. Two gage points 23 and 23 that are included in the camera field of view 6 in the data and have the largest interval in the camera field of view 6 in the latest image data are selected, and these are selected as the third and fourth selected gage points M ₃ and M ₃ . Set to ₄ .

Subsequently, when the third and fourth selected reference points M ₃ and M ₄ are newly set by the selection point setting unit 51, the calculation unit 52 sets the image data recorded in the image recording unit 4 (in detail, An interval L ₂₀ between the third reference point M ₃ and the fourth reference point M ₄ in the test piece 2 before the external force action, from the image data before the external force action and the latest image data after the external force action, The third displacement amount ΔL ₃ and the fourth displacement amount ΔL ₄ before and after the external force action are obtained. And the calculating part 52 calculates | requires elongation rate (epsilon) of the test piece 2 using these and said Formula (1) (step S16), and outputs the calculated elongation rate (epsilon).

On the other hand, in step S14, the selection point setting unit 51 determines that both the first and second selection standard points M ₁ and M ₂ are present in the camera field of view 6 (not reaching the setting area 6a). Then (step S14: No), the distortion measuring apparatus 1 performs steps S11 to S11 until at least one of the first and second selected reference points M ₁ and M ₂ deviates from the camera visual field 6 (reaches the setting region 6a). Repeat S14.

According to the strain measuring apparatus 1 described above, at least one of the _two standard points M ₁ and M ₂ used as calculation data for obtaining the elongation percentage ε as the strain of the test piece 2 progresses is from the imaging field 6. When it deviates (when it reaches the predetermined setting area 6a), the target point used as the calculation data is switched to the two reference points M ₃ and M ₄ existing in the imaging field of view 6 at that time. While securing a sufficient measurement range from the elastic deformation region to the plastic deformation region by the imaging unit, at least strain (elongation ε) in the elastic deformation region can be measured with high accuracy. That is, while the distortion generated in the test piece 2 is small (at least during the elastic deformation region), the predetermined two reference points M ₁ and M ₂ in the imaging visual field 6 are used as calculation data to accurately calculate the distortion of the test piece 2. If the distortion is progressed and at least one of these two standard points M ₁ and M ₂ deviates from the imaging field of view 6 (when reaching the predetermined setting area 6a), the two standard points used for the calculation data are determined. By switching to the reference points M ₃ and M ₄ existing in the imaging visual field 6 at that time, it becomes possible to measure strain thereafter (measurement of strain in the plastic deformation region).

  Next, a second embodiment of the present invention will be described with reference to FIG. 5 to FIG. 6C, but the same reference numerals are used for the same configurations as in the first embodiment, and a detailed description is omitted. Only the different configurations will be described in detail.

  The distortion measuring apparatus 1A of the present embodiment is different from the distortion measuring apparatus 1 of the first embodiment in that a camera driving unit (driving unit) 60 is provided.

The camera drive unit 60 includes a camera device drive mechanism 62 and a drive mechanism control unit 65. The camera driving unit 60 moves the camera along with the movement of the two selected reference points (first and second selected reference points M ₁ and M ₂ , and third and fourth selected reference points M ₃ and M ₄ ). The position of the camera device 3 so that the two reference points (first and second selected reference points M ₁ and M ₂ , or third and fourth selected reference points M ₃ and M ₄ ) are within the field of view 6. To control.

  The camera device drive mechanism 62 includes a guide member 63 and a drive mechanism (not shown). The guide member 63 extends in the pulling direction (vertical direction in the example of FIG. 5) of the test piece 2, and can guide the camera device 3 in the pulling direction. The drive mechanism moves the camera device 3 attached to the guide member 63 in the pulling direction based on an instruction signal from the drive mechanism control unit 65 (up and down movement in the example of FIG. 5).

  The drive mechanism control unit 65 uses the latest image data of the test piece 2 recorded in the image recording unit 4 (or picked up by the camera device 3), according to the distortion (elongation) of the test piece 2. A movement amount (movement speed) is obtained and output as an instruction signal to the drive mechanism.

Specifically, the drive mechanism controller 65, in the pulling direction, and an intermediate position in the pulling direction of the intermediate position and the camera view 6 of the first selection gauge M ₁ and the second selected target point M ₂ are identical Thus, the movement amount (movement speed) in the pulling direction of the camera device 3 is obtained and output. Then, the drive mechanism control unit 65 converts the two reference points 23 and 23 selected by the selection point setting unit 51 as calculation data from the first and second selection reference points M ₁ and M ₂ to the third and fourth points. When switched to a selective gauge M _3, M _4, so that the intermediate position in the pulling direction of the intermediate position and the camera view 6 of the third selection gauge M ₃ and the fourth selection gauge M ₄ are identical, The amount of movement (movement speed) in the pulling direction of the camera device 3 is obtained and output. That is, the drive mechanism controller 65, in the pulling direction, the distance of the first selection gauge M ₁ and the second selected target point M ₂ exceeds camera view 6 (see FIG. 6 (C)), the The moving amount (moving speed) of the camera device 3 in the pulling direction so that the intermediate position of the selected selected point M ₃ and the fourth selected moving point M ₄ coincides with the intermediate position of the camera visual field 6 in the pulling direction. Ask for.

  Next, the operation of the distortion measuring apparatus 1A of the present embodiment will be described. FIG. 7 is a flowchart showing the operation of the strain measuring apparatus 1A in the second embodiment.

  As preparation for the elongation rate determination, first, a plurality of gauge points 23, 23,... Are provided on the surface 24 of the test piece 2. The test piece 2 provided with the mark 23 is placed on a tensile tester or the like.

  When the tensile test is started, photographing of the test piece 2 by the camera device 3 is started, and image data (image signal) is recorded (accumulated) in the image recording unit 4 (step S21). In addition, the imaging | photography with the camera apparatus 3 is started before the external force action to the test piece 2. FIG. In the tensile test in the present embodiment, only the upper end 21 is pulled upward while the position of the lower end 22 of the test piece 2 is fixed.

Subsequently, the selection point setting unit 51 includes a plurality of reference points 23, 23 in the camera visual field 6 in the image data recorded in the image recording unit 4 (specifically, image data before an external force is applied to the test piece 2). .. Are selected (extracted) from the two mark points 23 and 23 having the largest intervals. The selection point setting unit 51 sets these first selection gauge _{M 1} and the second with a selected reference points _{M 2} (step S22). When the first selected reference point M ₁ and the second selected reference point M ₂ are set, the drive mechanism control unit 65 sets the first selected point M ₁ and the second selected point in the latest image data of the test piece 2. from the selection point M ₂ Prefecture, the amount of movement of the camera device 3 (moving speed) determined (step S23), and outputs an instruction signal to the driving mechanism. Thereby, the camera apparatus 3 (camera visual field 6) moves according to distortion (elongation) of the test piece 2 (refer FIG. 6 (A)-FIG. 6 (B)). That is, when the test piece 2 is distorted (extends) so that the two selected reference points M ₁ and M ₂ move in the same direction as the distortion progresses, the camera field of view is adjusted in accordance with the progress of the distortion of the test piece 2. 6 can follow the corresponding area of the test piece 2.

On the other hand, the calculation unit 52 obtains the reference length L ₀ , the first displacement amount ΔL _1, and the second displacement amount ΔL ₂ from the image data recorded in the image recording unit 4 (see FIG. 6B). The calculation unit 52 obtains the elongation rate ε of the test piece 2 using these and the above equation (1) (step S24), and outputs the obtained elongation rate ε.

The selection point setting unit 51 determines whether the first and second selected reference points M ₁ and M ₂ are in the camera field of view 6 (step S25). Selecting point setting unit 51, when at least one of the first selected reference points M ₁ and the second selection gauge M ₂ is determined to have deviated from the camera field of view 6 (step S25: No), the two reference points for selecting The first and second selected reference points M ₁ and M ₂ are switched to the third and fourth selected reference points M ₃ and M ₄ (step S26: see FIG. 6C).

When the two reference points selected by the selection point setting unit 51 are switched to the third and fourth selection reference points M ₃ and M ₄ , the drive mechanism control unit 65 sets the first reference point in the latest image data of the test piece 2. 3 selection point M ₃ and the fourth selection point M ₄ Prefecture, the amount of movement of the camera device 3 (moving speed) determined (step S27), and outputs an instruction signal to the driving mechanism.

Subsequently, the calculation unit 52 selects the third selection before the external force action from the image data recorded in the image recording unit 4 (specifically, the image data before the external force action and the latest image data after the external force action). The distance L ₂₀ between the gauge point M ₃ and the fourth selected gauge point M _4, and the third displacement amount ΔL ₃ and the fourth displacement amount ΔL ₄ before and after the external force action are obtained (see FIG. 6C). The calculation unit 52 obtains the elongation rate ε of the test piece 2 using these and the above equation (1) (step S28), and outputs the obtained elongation rate ε.

On the other hand, when the selection point setting unit 51 determines in step S25 that the first and second selection standard points M ₁ and M ₂ are in the camera field of view 6 (step S25: Yes), the distortion measuring apparatus 1A Steps S21 to S25 are repeated until at least one of the first and second selected reference points M ₁ and M ₂ is out of the camera field of view 6.

Also with the strain measuring apparatus 1A described above, at least one of the _two reference points M ₁ and M ₂ used as calculation data for obtaining the elongation rate ε as the strain of the test piece 2 progresses deviates from the imaging field 6. In this case, by switching the reference point used as the calculation data to the two reference points M ₃ and M ₄ existing in the imaging visual field 6 at that time, one imaging unit can change the elastic deformation region to the plastic deformation region. While ensuring a sufficient measurement range, strain (elongation ε) in at least the elastic deformation region can be measured with high accuracy.

  The non-contact type strain measuring device and the non-contact type elongation measuring method of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. It is.

The specific timing for switching the two reference points 23 and 23 selected by the selection point setting unit 51 of the measurement value calculation unit 50 is not limited. For example, the selection point setting unit 51 of the first and second embodiments described above has a predetermined at least one of the two selected reference points 23 and 23 (first and second selected reference points M ₁ and M ₂ ). At the timing when the setting area 6a (or 6b) is reached, the two target points 23 and 23 existing in the camera visual field 6 at that time are selected again, and these are selected as new selected reference points (third selected reference point M). ₃ , the fourth selected reference point M ₄ ), but is not limited to this. When the value based on the positions of the two selected reference point areas 23 and 23 (first and second selected reference points M ₁ and M ₂ ) reaches a predetermined set value, the selection point setting unit At the time, the two target points 23 and 23 existing in the camera visual field 6 are selected again, and these are set as new selected reference points (third selected reference point M ₃ and fourth selected reference point M ₄ ). May be.

For example, specifically, the selection point setting unit obtains the elongation ε of the test piece 2 from the two selected benchmarks 23 and 23 (first and second selected benchmarks M ₁ and M ₂ ). The third and fourth selected reference points M ₃ and M ₄ may be set at the timing when the elongation rate ε reaches a predetermined set value. Specifically, when the upper limit value (general value) of the elastic deformation region in the nominal stress-nominal strain diagram is, for example, 0.8%, the selection point setting unit displays the first and second selection standard points M ₁ and M _2. When the elongation rate ε calculated by the calculation unit 52 based on the position of exceeds 1%, the two gauge points 23 and 23 existing in the camera visual field 6 at that time are selected again, and these are newly selected. gauge may be set to (third selection gauge M _3, fourth selection gauge M _4). In this case, the initial positions of the first and second marks M ₁ and M ₂ (positions before the external force acts in the tensile direction on the test piece 2) are applied to the test piece 2 and the elongation ε is 1 %, It is set to be within the camera field of view 6.

  In the strain measuring apparatuses 1 and 1A of the first and second embodiments, the surface 24 of the test piece 2 is regularly (in the examples of the first and second embodiments, continuous with a predetermined interval along the tensile direction). The elongation percentage ε of the test piece 2 is obtained by using the dot marks (marks) 23, 23,... Arranged in the target), but the arrangement of the plurality of marks 23, 23,. It is not limited to arrangement.

  For example, as shown in FIGS. 8 (A) to 8 (C), a plurality of reference points 23a, 23a,... May be randomly arranged (provided) on the surface 24 of the test piece 2. The plurality of randomly assigned marks 23a, 23a,... Are formed, for example, by spraying spray-type paint or the like on the surface 24 of the test piece 2.

In this case, for example, the calculation unit obtains the elongation rate ε of the test piece 2 using the two gauge regions 123 and 123. This mark area 123 is a minute area set so as to include one or a plurality of mark points 23a. For example, specifically, in the case of the strain measuring apparatus 1 of the first embodiment, the two point areas are located at a position where the selection point setting unit 51 enters a predetermined distance from the end of the camera visual field 6 in the pulling direction. 123 and 123 are set. Subsequently, the calculation unit 52 obtains the elongation rate ε of the test piece 2 using the two gauge points 123 and 123. Specifically, the selection point setting unit 51 sets the two reference point areas 123 and 123 as first and second selection reference point areas M ₁ and M ₂ (see FIG. 8A). Subsequently, the calculation unit 52 obtains L ₀ , ΔL ₁ , and ΔL ₂ from the image data recorded in the image recording unit 4 using the first and second selected reference point regions M ₁ and M ₂ (FIG. 8). (See (B)), by substituting these into the above equation (1), the elongation ε of the test piece 2 in the elastic deformation region is obtained. Then, the two reference points selected by the selection point setting unit 51 are switched according to the distortion of the test piece 2. That is, two gage areas 123 and 123 are newly set at positions inside the camera visual field 6 by a predetermined distance in the pulling direction, and these are designated as the third and fourth selected gage areas M _3. , and _{M 4.} When the new selected standard areas (third and fourth selected standard areas M ₃ , M ₄ ) are set, the calculation unit 52 re-sets the third and third re-set values from the image data before the action of the external force. A point area 123 corresponding to the fourth selected point areas M ₃ and M ₄ is obtained. Subsequently, the calculation unit 52 obtains L ₂₀ , ΔL ₃ , and ΔL ₄ (see FIG. 8C), and substitutes them into the above equation (1), whereby the test piece 2 in the plastic deformation region is obtained. Obtain the elongation ε.

  Detection (identification) of the same target area 123 in the image data before the external force action recorded in the image recording unit 4 and the image data after the external force action is performed by pattern matching or the like in the image data before and after the external force action. .

  Further, in the tensile test of the first embodiment, the test piece 2 is pulled upward while the lower end is pulled downward, but the position of one end 21 (or 22) of the test piece 2 is determined. Only the other end 22 (or 21) may be pulled in a state where is fixed.

In this case, the camera device 3 is not limited to the configuration in which the camera device 3 moves as the distortion of the test piece 2 proceeds as in the second embodiment. For example, when the selected point set by the selection point setting unit is switched, either one of the two initially selected points may be selected again. That is, the selection point setting unit 51 is pulled into the camera field of view (measurement region) 6 by pulling only one end of the test piece 2 as in the example shown in FIGS. 9 (A) to 9 (C). If only the first selection gauge M ₁ is out of, when re-selecting two reference points 23, 23, the second selection gauge M ₂ again (continued) selecting (fourth selection of with a gauge M _4), it may be configured to select a new third selection gauge M _3.

  Moreover, in the distortion measuring apparatuses 1 and 1A of the first and second embodiments, the selected target is switched only once, but may be performed twice or more. In this case, it is preferable that six or more marks 23, 23,... Are provided on the surface 24 of the test piece 2.

The selected point setting unit 51 in the strain measuring apparatuses 1 and 1A of the first and second embodiments places the newly selected reference points M ₃ and M ₄ in the camera visual field 6 before the external force is applied to the test piece 2. Although the target point 23 is selected, it may be selected from the target point 23 that has entered the camera visual field 6 after the external force action. However, in the case where the reference point 23 that has entered the camera visual field 6 after the external force action is set as the new selected reference point M ₃ and / or M ₄ , the selection point setting unit 51 of the first and second embodiments is used. In addition, the accuracy of the elongation rate ε of the test piece 2 to be obtained is lower than in the case where the gauge points 23 and 23 existing in the camera visual field 6 before the action of the external force are newly selected gauge points M ₃ and M _4. . This is due to the following reason.

When the gauge points 23 and 23 existing in the camera visual field 6 before the external force action are newly selected gauge points M ₃ and M ₄ (see FIG. 10A), calculation is performed in the same manner as in the first embodiment. part 52, the third and fourth selection gauge _M 3, _{M 4} the amount of displacement [Delta] L _3, [Delta] L ₄ and the third and fourth selection gauge _M 3, _{M 4} the reference length [Delta] L obtained by actual measurement ₂₀ (refer FIG. 10 (B)), the elongation rate (epsilon) of the test piece 2 is calculated | required.

Selection contrast, when the selection point setting unit and gauge 23 a new selection gauge M ₄ coming into camera view 6 after external force (see FIG. 11 (A)), calculation unit 52, newly initial position of the selected target point as a standard point M _4: after estimating P (external force before the position of the test piece 2 position P in FIG. 11 (a)), the fourth on the basis of the initial position P obtaining estimated displacement amount [Delta] L _4a of selected gauge _{M 4,} and third and fourth selection gauge _M 3, _{M 4} the estimated reference length [Delta] L _20a (see FIG. 11 (B)). Subsequently, the calculation unit 52 measures the actually measured displacement amount ΔL _{3 of the third} selected reference point M ₃ , the estimated displacement amount ΔL _{4a of} the fourth selected reference point M ₄ , and the third and fourth selections. The estimated elongation rate ε of the test piece 2 is obtained from the estimated reference length ΔL _{20a of the} reference points M ₃ and M ₄ (see FIG. 11B). This initial position P can be obtained by using the elongation ε of the test piece 2 at the time of switching the selected reference point obtained using the first and second selected reference points M ₁ and M _2. . Incidentally, FIG. 11 (A) and 11 in the example shown (B), the gauge 23 which is selected in a new selection gauge M _4, which has entered the camera view 6 after external force, is selected to the newly selected target point M ₃ gauge 23 is what was before the external force acting on the camera view 6. For more information, selecting point setting unit 51, when switching the selection gauge, the second selection reference points M ₂ resets the third selection gauge M _3, coming into the camera field of view 6 after external force setting the gage 23 to the fourth selection gauge M _4.

As described above, when the standard point 23 that has entered the camera visual field 6 after the external force is used as the new selected standard point M ₄ , the displacement amount ΔL _4a of the selected standard point used for obtaining the elongation ε and the reference length since [Delta] L _20a is an estimated value, compared to the elongation obtained by actual measurement epsilon (i.e., in the above example, to select a gauge 23 included before an external force acting on the camera view 6 as the selected gauge M ₄₎ The accuracy of the calculated elongation rate ε is lowered.

In the example shown in FIGS. 11A and 11B, one of the two newly selected selection points M ₃ and M ₄ is a point 23 that has entered the camera visual field 6 after the action of an external force. The other is the mark 23 in the camera visual field 6 before the external force action, but is not limited to this. Both of the two newly selected reference points M ₃ and M ₄ may be the reference points 23 and 23 that have entered the camera visual field 6 after the action of an external force.

1, 1A distortion measuring device 2 test piece 3 camera device (imaging part)
6 Camera field of view (imaging field of view)
6a, 6b Setting area 23, 23a Test point 24 Test piece surface 50 Measurement value calculation unit 51 Selection point setting unit 52 Calculation unit 123 Target point area L ₀ , L ₂₀ Reference length M ₁ First selection standard point M ₂ 2 selected reference point M ₃ third selected reference point M ₄ fourth selected reference point ΔL ₁ first selected reference point displacement amount ΔL ₂ second selected reference point displacement amount ΔL ₃ third selected reference point Point displacement amount ΔL ₄ Fourth selected gauge point displacement amount ε Elongation rate

Claims (5)

A non-contact type strain measuring device that measures a predetermined physical quantity related to the strain of the test piece in a test piece provided with a plurality of marks on the surface in a non-contact manner,
An imaging unit for imaging the test piece;
In the image data of the test piece acquired by the imaging unit, the predetermined target region is obtained by using, as calculation data, a target region including one or a plurality of target points and in the imaging field of view of the imaging unit. A measurement value calculation unit for obtaining a physical quantity of
The measurement value calculation unit is configured when at least one of the two gauge areas used as calculation data for obtaining the predetermined physical quantity reaches a predetermined setting area, or at the position of the two gauge areas. A non-contact strain measuring apparatus, wherein when a value based on a predetermined set value is reached, a target area used as the calculation data is switched to two reference areas in the imaging field of view.   The non-contact type strain measuring apparatus according to claim 1, wherein the test piece includes a plurality of randomly arranged marks on the surface.   The non-contact strain measuring apparatus according to claim 1, wherein the test piece has a plurality of marks on the surface continuously arranged at predetermined intervals along the tensile direction.   4. The apparatus according to claim 1, further comprising a drive unit that controls a position of the imaging unit so that the two marking regions enter the imaging field of view as the two marking regions move. The non-contact type distortion measuring device according to any one of the above. A non-contact type strain measurement method for measuring a predetermined physical quantity related to a strain of a test piece in a test piece provided with a plurality of test marks on a surface in a non-contact manner,
In the image data of the test piece acquired by the imaging unit that images the test piece, arithmetic data is obtained for the two target points in the imaging field of view of the imaging unit that are one or a plurality of target points. A first physical quantity derivation step for obtaining the predetermined physical quantity by using as:
In the image data, when at least one of the two gauge points used as calculation data for obtaining the predetermined physical quantity in the first physical quantity derivation step reaches a predetermined setting area, or the two When a value based on the position of the target area reaches a predetermined set value, the target area used as the calculation data is switched to two target areas existing in the imaging field of view, and the two changed targets And a second physical quantity derivation step for obtaining the predetermined physical quantity from a point region.

Images