JP2000258131A - Non-contact extensometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact extensometer capable of highly accurately and efficiently measuring the breaking elongation of a test piece. SOLUTION: Prior to the start of a breaking elongation test to the test piece, after measuring a distance between reference lines attached to the test piece as an initial inter-reference-line distance L0 (step S1), the breaking elongation test to the test piece is executed (step S2). Then, when the test piece is broken, a tester main body is driven without removing the test piece from the tester main body and the broken surfaces of the broken respective test pieces are abutted to each other (steps S4 and S5). In such a manner, in the state of abutting the broken surfaces with each other, the distance between the reference lines is measured as a broken surface abutted inter-reference-line distance L (step S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact extensometer which can measure the elongation at break of a test piece with high accuracy and efficiency.

[0002]

2. Related Background Art A tensile test of a test piece is performed by measuring the elongation of the test piece while applying a tensile load to the test piece by a tester body supporting both ends of the test piece. In particular, recently, two marked lines parallel to each other at a predetermined distance Lo in the direction of extension of the test piece are imaged by a camera, and the positional displacement of each marked line is obtained from the image. Non-contact measurement of the elongation of the test piece is also performed.

One of the tensile tests is a breaking elongation test. This elongation at break test is performed by breaking a test piece by applying a tensile load, and obtaining the elongation percentage of the test piece when the test piece is broken. Incidentally, the amount of elongation when the test piece was broken was determined by abutting the broken surfaces of the broken test piece against each other, and in this state, applying a predetermined distance Lo in parallel in the elongation direction of the test piece beforehand.
By measuring the distance L between the book marks, it is obtained as [L-Lo]. The elongation at break K (%) of the test piece is obtained as K (%) = [(L−Lo) / Lo] × 100 (%).

[0004] Specifically, a pair of broken test pieces are removed from the tester main body, and these broken test pieces are aligned so that their center lines coincide with each other, and their cut surfaces are abutted with each other. After the surface is fixed with cellophane tape or the like, the distance L between the marked lines is measured using calipers or the like. Then, the elongation at break K is calculated from the distance Lo between the gauge lines measured in advance.

[0005]

However, as described above, it takes time and effort to match the fractured surfaces of a pair of fractured test pieces while keeping their center lines coincident, and it is difficult to accurately match the fractured surfaces. It is. In particular, the fracture surface is likely to be irregular due to the fracture situation, and it is difficult to match the center lines themselves. Because of this,
High precision measurement could not be expected.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a non-contact extensometer capable of measuring the elongation at break of a test piece with high accuracy and efficiently. It is in.

[0007]

In order to achieve the above-mentioned object, a non-contact extensometer according to the present invention comprises a tester main body for supporting both ends of a test piece and applying a tensile load to the test piece; A camera that respectively captures two marked lines attached to the test piece in parallel with each other at a predetermined distance in the direction of extension of the test piece, and the camera uses the camera before the start of a tensile test on the test piece. The distance between the marked lines is measured from the position of each marked line image in the captured image (initial marked line distance measuring means). Thereafter, a tensile test is performed on the test piece. When the test piece breaks, the tester main body is driven to a position where the fracture surfaces of the fractured test pieces abut against each other, and the fracture surfaces are collated (fracture surface collation means).
And measuring the distance between the marked lines from the position of each marked line image in the image captured by the camera in a state where the fractured surfaces are matched with each other (fracture surface matched mark line distance measuring means). Features.

That is, the non-contact extensometer according to the present invention has a structure in which, when a test piece is broken by applying a tensile load, the test piece does not need to be removed from the tester main body until the fracture surfaces abut each other. The tester body is driven to rupture the test pieces, and in this state, the distance between the marked lines is measured from the image taken by the camera as the distance between the broken butted marks. Incidentally, the abutting of the fractured surfaces of the broken test pieces is performed, for example, while detecting the load generated between both ends of the test pieces.

In the measurement of the distance between the torn marking lines, the distance between the two marking lines in a state where the fractured surfaces of the broken test pieces are butted against each other is detected from an image taken by the camera. From the position of each marked line, or the distance between the marked lines detected after the test piece breaks with the execution of the tensile test as described in claim 2, and one of the broken test pieces. It is determined from the displacement distance of the marked line attached to the one test piece when the fractured surfaces are moved to a position where they come into contact with each other.

[0010] In a preferred aspect of the present invention, as each of the cameras, first and second cameras supported movably in the extending direction of the test piece are used as the cameras. The line-to-line distance measuring means may be the first
The position of each mark is obtained from each position of the second camera and the position of each mark image in an image captured by each of the cameras.

Further, according to the present invention, the initial distance between the reference lines Lo measured by the initial distance between the reference lines and the distance between the reference marks between the fractured surfaces are measured by the initial distance between the reference lines. It is characterized in that it comprises means for calculating the elongation at break of the test piece according to the distance L between the fracture surface butting marks.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A non-contact extensometer according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a non-contact extensometer according to this embodiment, where S is a test piece whose both ends are respectively attached to a not-shown test machine main body and subjected to a tensile test, and R1, R
2 indicates a predetermined distance Lo in the elongation direction of the test piece S in advance.
Are two marked lines parallel to each other. Each of these marked lines R1 and R2 is, for example, 50 parallel to the parallel portion of the test piece S.
It consists of straight line marks drawn using paint or the like at a distance of mm. When a plurality of test pieces S are supplied in lots and subjected to a tensile test, the mark lines R1 and R2 are respectively attached to substantially the same positions of these test pieces S.

A non-contact extensometer, which is incorporated in the tester main body and measures the elongation of the test piece S in a non-contact manner with the test piece S, is a high-magnification second exfoliator for imaging the mark lines R1 and R2. First and second cameras 1, 2 and each of these cameras 1, 2,
The light sources 3 and 4 are attached to the sides of the camera 2 and illuminate the imaging area (each marked portion of the test piece S) by the cameras 1 and 2. These cameras 1 and 2 are supported on first and second moving stages 5 and 6 respectively, and the test piece S
Are provided so as to be able to move in parallel along the direction of extension of. Incidentally, each of the stages 5, 6 meshes with a feed screw 7a, 8a driven by a pulse motor 7, 8, and moves in the extension direction of the test piece S under the rotation control of the pulse motor 7, 8 (up and down). Movement) to adjust the position.

Each of the cameras 1 and 2 incorporates, for example, a CCD image sensor (area sensor) as an image sensor, and captures a partial surface image of the test piece S including each of the reference lines R1 and R2, for example. It is configured to obtain a high-resolution image signal by performing close-up imaging (macro imaging) at approximately the same magnification. The imaging of the surface image including the reference lines R1 and R2 by the cameras 1 and 2 is performed in a focused state, whereby a clear image is always obtained.

As described above, partial surface images (images) of the test piece S including the reference lines R1 and R2 captured by the cameras 1 and 2 are sent to the CPU via the image processing units 11 and 12. , And is subjected to predetermined image processing to detect the position of the marked line image in each of the images. The positions of the marked lines detected in the respective images are displayed in parallel on the display 14, for example. At this time, while the raw images captured by the cameras 1 and 2 are directly displayed on a TV monitor (not shown), the mark line R calculated by the arithmetic processing unit 13 is displayed.
1 and R2 are displayed on the display 14.
It may be displayed above.

The display 14 has a soft switch for manually operating the movement of each of the cameras 1 and 2, a soft switch for instructing initial settings and the like for the cameras 1 and 2, An operation area for displaying soft switches and the like for controlling the operation of the main body is provided. Further, the display 14 is provided with a graph display area for graphically displaying the relationship between the load measured by the tensile test and the elongation. Using such a display screen of the display 14 as an interface, setting input of various conditions and the like for a tensile test and further, initial setting processing for an extensometer and the like are performed.

The arithmetic processing unit 13 detects a mark image in each of the images captured by the cameras 1 and 2 according to a software application for elongation measurement prepared in advance, and detects the center of gravity of the mark image. It has a function to find the position. Then, based on the difference (distance on the image) between the barycentric position of the mark image obtained in each image and a preset reference position (eg, image center) in each image, the mark is positioned at the reference position. The amount of deviation from the state in which the test piece S was moved, and the amount of displacement of each of the marked lines R1 and R2 due to the elongation of the test piece S, are detected.

Incidentally, the displacement amount of each of the reference lines R1 and R2 is:
For example, a distance (unit distance) between one pixel in the image is determined in advance according to an imaging magnification of the cameras 1 and 2 and a pixel array pitch of the CCD image sensor, and the unit distance is determined on the image. It is calculated by multiplying the difference (distance on the image) between the barycentric position of the marked line image and the reference position. At this time, the cameras 1 and 2
By subjecting the image signals obtained respectively to the enlargement processing while appropriately performing an interpolation operation, and detecting the displacement positions of the marking lines R1 and R2 from the enlarged image, the measurement accuracy can be increased. It is possible.

When the marked line image deviates from the images picked up by the cameras 1 and 2, respectively, the arithmetic processing unit 13 puts the marked lines R1 and R1 along with the extension of the test piece S. When the position of R2 is displaced and reaches the limit of the imaging range of each of the cameras 1 and 2, the position controllers 15 and 16 are activated. The pulse motors 7 and 8 are controlled under the control of the position controllers 15 and 16 in accordance with the difference (distance on the image) between the barycentric position of the mark image obtained from the image and the reference position at that time. Are driven, and the cameras 1 and 2 are respectively moved in the moving directions of the marked lines R1 and R2 accompanying the elongation of the test piece S. The movement of each of the cameras 1 and 2 by the position controllers 15 and 16 is performed, for example, such that the center of gravity of the mark image in the image captured by each of the cameras 1 and 2 becomes the reference position in each of the images. That is, the cameras 1 and 2 are positioned so as to capture the marking lines R1 and R2 at the reference position in the captured image.
2 is controlled. Specifically, the position control units 15 and 16 drive the pulse motors 7 and 8 by an amount corresponding to the difference between the barycentric position of the mark image obtained from each image and the reference position of the screen. Camera 1
2 is moved, whereby the positions of the cameras 1 and 2 are changed following the movement of the marking lines R1 and R2 accompanying the elongation of the test piece S.

Here, the measurement of the elongation of the test piece S by detecting the position of the mark image in the images captured by the cameras 1 and 2 will be briefly described.
The two marked lines R1 and R2 attached to the test piece S indicate that the test piece S is pulled upward by pulling the test piece S as shown in FIG.
As it grows, it gradually moves upward. Therefore, the two cameras 1 and 2 that respectively image the respective marking lines R1 and R2 are translated upward in accordance with the movement of the marking lines R1 and R2.
If each mark R1, R2 is always captured at the center of the image, the distance L between the marks P1, P2 of the cameras 1, 2 from the marks R1, R2 and the movement distance of each camera 1, 2 can be calculated. Test piece S
It is possible to determine the amount of elongation.

Specifically, the upper camera (first camera) 1
Is P1 and the position of the lower camera (second camera) 2 is P2, the distance L between the marked lines R1 and R2 can be obtained as L = P1-P2. The moving amount of the upper camera (first camera) 1 is C _H , and the lower camera (second camera) is
When the amount of movement of No. 2 is C _L , the elongation E between the marked lines of the test piece S can be obtained as E = C _H −C _L.

In a state where the positions of the cameras 1 and 2 are fixed, changes in the positions of the marked lines in the images picked up by the cameras 1 and 2 indicate the marked lines R1 and R2 associated with the extension of the test piece S. Can also be obtained for each position. Specifically, the displacement amounts D _H and D _L of the mark lines R1 and R2 are obtained from the displacement amounts of the mark lines images from the reference position in the images captured by the cameras 1 and 2, respectively. Then, as described above, the elongation amount E between the reference lines R1 and R2 of the test piece S is obtained from the displacement amounts D _H and D _{L of} these reference lines R1 and R2.
Can be obtained as E = D _H −D _L. In this case, the mark lines R1, R
The distance L between two fixed upper and lower cameras 1, 2
L = (P1 + D _H ) − (P2 + D
_L ). Note that the displacement amounts D _H and D _L are obtained by multiplying the displacement amount of the marked line image detected on the image by a coefficient depending on the pixel pitch, the imaging magnification, and the like, as described above.

However, there is a limit to the amount of elongation E between the marked lines R1 and R2 which can be obtained in this way. If the marked lines R1 and R2 deviate from the field of view of the cameras 1 and 2, it is natural that Measurement becomes impossible. Therefore, in this case, when the position of the mark image in each image reaches a predetermined limit of the imaging range, each of the cameras 1 and 2 is moved to its reference position by driving the pulse motors 7 and 8. Mark R
1, the camera position is moved so as to capture R2, and while adding the movement amounts C _H and C _L of the cameras 1 and 2 at that time, the marker obtained from the position of the marking line image in each image as described above. displacement D _H lines R1, R2, D _L the elongation of E between the marked lines on the basis of _{E = (L H + C H} ) - (L L + C L) may be so determined as. Furthermore, for the distance L between the marked lines R1, R2 L = (P1 + D H + C H) - (P2 + D L + C L) may be so determined as.

Basically, the non-contact extensometer for detecting the elongation E of the test piece S and the distance L between the reference lines R1 and R2 as described above is characterized by the following features. Thus, it has a function of executing a breaking elongation test. That is, in the elongation at break test, first, in the arithmetic processing section 13, according to the images respectively taken by the cameras 1 and 2 before the start of the tensile test and the positions of the cameras 1 and 2, FIG. As shown in FIG. 3, a function for measuring the distance Lo between the reference lines R1 and R2 as an initial reference line distance (initial reference line distance measuring means), and thereafter, with the execution of the tensile test, the test piece S When the test machine body is broken as shown in b), the test machine body is operated in a direction opposite to the direction in which the tensile load is applied by, for example, manually operating the test machine body, and the test machine body is divided into two as shown in FIG. A function of bringing the separated test pieces S1 and S2 closer to each other and butting their fracture surfaces against each other (fracture surface matching means), and images taken by the cameras 1 and 2 in a state where these fracture surfaces are butted. , And each camera 1 2, the function of measuring the distance L between the reference lines R1 and R2 as the distance between the fracture surface matching target lines (means for measuring the distance between the fracture surface matching target lines).

If necessary, prior to the start of the test, after measuring the distance Lo between the marked lines R1 and R2 attached to the test piece S in advance, a tensile load is applied to the test piece S, and if the test piece S breaks, For example, the test piece S is displaced in a direction opposite to the tensile load direction without detaching the test piece S from the tester main body, and its fracture surfaces are abutted against each other. It is characterized in that a distance L between the two is measured. Then, the elongation at break K of the test piece S is calculated according to the measured distance L between the initial marked lines and the measured distance L between the butt cross-sections.

In FIG. 3, reference numerals 21 and 22 denote chucks provided on the tester main body to support both ends of the test piece S, respectively. Each of these chucks is attached to an upper crosshead and a lower crosshead, and is configured to apply a load to the test piece S as the crosshead moves up and down. Incidentally, the tensile test is performed by applying a tensile load to the test piece S by moving the upper crosshead upward while the position of the lower crosshead is fixed. Butting of each of the fractured test pieces is performed by lowering the upper crosshead. For example, when a load is generated between both ends of the test piece S supported by the chucks, the fracture is performed. Is detected as a matched state.

More specifically, as shown in FIG. 4, a test piece S is first mounted on a tester main body, and in this state, the cameras 1 and 2 use the respective mark lines R 1 and R 2. R2 is imaged, and the distance Lo between the reference lines R1 and R2 is measured as an initial distance between the reference lines from the mark image [Step S1]. Thereafter, the tester main body is operated to apply a tensile load to the test piece S (step S2). The application of the tensile load to the test piece S is performed, for example, by raising the upper crosshead while the lower crosshead is fixed. Thus, the test piece S is pulled while monitoring the load applied to the test piece S. At this time, it goes without saying that the position detection is performed following the displacement of the marked lines R1 and R2 accompanying the elongation of the test piece S.

When the elongation of the test piece S reaches the limit and the test piece S breaks, the load applied to the test piece S suddenly becomes zero (0). The breakage of the test piece S is detected by sequentially determining such a change in load [Step S3]. In other words, a tensile load is continuously applied to the test piece S until the load applied to the test piece S becomes zero (0).

When the test piece S breaks, the break is detected, the driving of the tester main body is stopped immediately, and the application of the tensile load is stopped. However, the upper test piece separated by the break has its tensile inertia. Under the force, it is displaced upward from its break position as shown in FIG. However, this upward displacement can be suppressed to a certain range by using a brake mechanism or the like. Then, this time, the upper crosshead is lowered by manually operating the tester body or the like [Step S4], that is, the test pieces S are displaced in a direction opposite to the above-mentioned tensile load direction, so that the fractured surfaces abut each other. You. The matching of the fractured surfaces is performed while detecting the load applied to both ends of the test piece S. When a certain load is detected, it is determined that the load is caused by the comparison of the fractured surfaces and executed. [Step S5].
After lowering the upper crosshead visually until the fractured surfaces approach each other, gradually lowering the upper crosshead while monitoring the generation of the load without applying an excessive load on the fractured surface. Preferably.

When the fractured surfaces of the test pieces S abut each other as shown in FIG. 3C, the distance L between the reference lines R1 and R2 is then determined using the cameras 1 and 2. Is measured again, and the measured value is obtained as the distance between the broken surface butted mark lines [Step S6]. Then, the breaking elongation rate K is calculated based on the distance L between the fractured surface butting lines determined in this way and the initial distance Lo between the standard lines determined before the start of the test as described above.

When calculating the distance L between the torn marking lines, the distance Lc between the marking lines R1 and R2 in a state where the test piece S is broken as shown in FIG. 3B is measured. Then, the upper crosshead is lowered from above, and the cut surfaces are abutted against each other as shown in FIG. 3 (c). At this time, since the position of the lower crosshead remains fixed and the position of the lower mark R2 does not change, only the lowering amount Ld of the upper mark R1 accompanying the lowering of the upper crosshead is measured. It is also possible to determine the distance L between the fractured surface butting marks by setting = Lc-Ld.

In this way, the tester main body is operated in the direction opposite to the direction in which the tensile load is applied, so that the fracture surfaces of the test pieces S are butted against each other, and the distance L between the fracture surface butted marks is measured. According to 2
Since the separated test pieces S (S1, S2) are not removed from the tester main body, the fracture surfaces of the two test pieces S1, S2 separated by breaking can be accurately butted. Moreover, since the center lines can be accurately matched and the fractured surfaces can be abutted, it is possible to effectively prevent entry of an error factor due to a shift of the center line or the like. Further, since the distance L between the fractured surface butting marks can be obtained by using the same measuring system as the measuring system for the initial distance L between marks, the effect that the test accuracy can be improved also in this respect can be obtained. Can be

Further, according to the present apparatus having the above-described functions, after the broken test pieces S1 and S2 are removed from the tester main body, the cut surfaces are abutted with each other and fixedly integrated with a cellophane tape or the like. Work is unnecessary,
The time and labor required for the operation can be greatly reduced, and effects such as improvement in operation efficiency can be achieved. Furthermore, the work of butting the fracture surface can be performed by effectively utilizing the load measurement function basically provided in the tester main body and the vertical drive mechanism of the crosshead, so that the device configuration becomes complicated. There are effects such as no fear.

The present invention is not limited to the above embodiment. For example, it is of course possible to apply a tensile load to the test piece S by lowering the lower crosshead side, and if the width of displacement of the reference lines R1, R2 falls within the visual field range of the cameras 1, 2, the camera 1, Marking line R with 2 fixed
It is also possible to detect the position of 1, R2. Here, two cameras 1 and 2 are used to detect two marker lines R1 and R2, respectively. However, one camera (line sensor) is used to detect the positions of the marker lines R1 and R2. Can be detected, and the distance between the marked lines can be measured. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0035]

As described above, according to the present invention, the distance between the marked lines attached to the test piece is measured before the elongation test of the test piece, and then the tensile load is applied to the test piece. The elongation at break test is performed by adding. Then, when the test piece breaks, the test piece is driven without removing the test piece from the test machine main body, and the broken surfaces are abutted against each other. In this state, the distance between the marked lines is measured, so that the deviation is measured. Practically significant effects such as the fact that the fracture elongation rate of the test piece can be measured efficiently and with high accuracy by accurately abutting the fractured surfaces without inviting them can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a non-contact extensometer according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a detection operation of a mark line attached to a test piece in the non-contact extensometer shown in FIG.

FIG. 3 is a diagram schematically showing a characteristic form of a breaking elongation test of the present invention.

FIG. 4 is a diagram showing a schematic processing procedure of a breaking elongation test characteristic of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st camera 2 2nd camera 11,12 Image processing part 13 Operation processing part 14 Display 15,16 Position control part S Test piece R1, R2 Marking line

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2F065 AA17 AA22 AA65 BB13 BB15 BB28 CC00 DD04 DD06 EE00 FF04 FF42 FF67 GG13 JJ03 JJ05 JJ09 JJ26 NN20 PP02 PP11 PP22 QQ21 QQ23 QQ25 QQ27 QQ13 Q02A01 SS02 DA02 SS EA02 EB07

Claims (4)

[Claims] 1. A tester main body which supports both ends of a test piece and applies a tensile load to the test piece, and a tester main body which is attached in parallel to the test piece at a predetermined distance in a direction in which the test piece extends. A camera for imaging each of the mark lines, and an initial mark for measuring a distance between the mark lines from a position of each of the mark images in an image taken by the camera prior to the start of a tensile test on the test piece. Line distance measuring means, After the test piece is fractured along with the execution of the tensile test, a fracture surface butting means for driving the testing machine body to a position where the fracture surfaces of the fractured test specimen abut each other, In the state where each of the fracture surfaces is abutted against each other, a fracture surface abutment reference distance measurement that measures a distance between the reference lines from a position of the reference line image in an image captured by the camera. Noncontact extensometer, characterized by comprising a stage. 2. The method according to claim 1, wherein the measuring unit measures a distance between the reference lines detected after the test piece breaks during execution of the tensile test and one of the broken test pieces. The distance between the fracture surface butting mark lines is obtained from a displacement distance of a marking line attached to the one test piece when the fracture surfaces are moved to a position where the fracture surfaces meet each other. The described non-contact extensometer. 3. The camera according to claim 1, wherein the camera comprises first and second cameras supported so as to be movable in a direction in which the test piece extends. 2. The position of each of the marked lines is obtained from each of the positions of the marked lines and the position of each of the marked lines in an image captured by each of the cameras.
Non-contact extensometer described in 1. 4. The non-contact extensometer according to claim 1, wherein the initial inter-marker distance measured by the initial inter-marker distance measuring means is measured by the fractured surface matching inter-marker distance measuring means. According to the distance between the fractured surface butting line,
A non-contact extensometer comprising means for calculating the elongation at break of the test piece.