JP2000258134A - Non-contact extensometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact extensometer provided with a function capable of easily and highly accurately measuring a distance between two reference lines attached to a test piece provided for a tension test. SOLUTION: This extensometer is provided with first and second cameras 1 and 2 for respectively picking up the images of the two reference lines attached to the test piece and first and second origin sensors 9 and 10 for respectively stipulating the movement origin positions of the respective cameras 1 and 2. In this case, a distance (z0) between the origin sensors 9 and 10 is measured and stored from a moving amount (x0, y0) from the movement origin position of the camera at the time of moving the respective cameras 1 and 2 so as to capture one of the reference lines at a screen center and the distance (z) between the reference lines is measured from the moving amount (x, y) at the time of respectively moving the respective cameras 1 and 2 following the displacement of the respective reference lines accompanying the elongation of the test piece and the distance (z0) between the origin sensors 9 and 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact elongation having a function of easily and accurately measuring a distance between two mark lines attached to a test piece to be subjected to a tensile test. About the total.

[0002]

2. Related Background Art A tensile test of various test pieces in a material testing machine is performed by measuring the tensile load and the elongation of the test piece while applying a tensile load to the test piece. In particular, recently, a non-contact extensometer that measures the elongation of the test piece without using a laser or a line sensor in a non-contact manner with the test piece has attracted attention. This type of non-contact extensometer basically detects two marked lines parallel to a test specimen at a predetermined distance in the direction of extension, and optically detects the two marked lines. The elongation is obtained from the change.

As one method of a non-contact extensometer, for example, as disclosed in Japanese Utility Model Publication No. Hei 6-31365, two cameras (optical heads) for imaging two marked lines attached to a test piece, respectively. Is provided so as to be able to translate in the direction of extension of the test piece, and while moving the cameras respectively in accordance with the change in the position of the mark associated with the extension of the test piece, the Some of them measure the elongation of the test piece according to the position. Incidentally, the non-contact extensometer disclosed in this publication controls the movement of the camera so that the position of the marked line in the image picked up by the camera always becomes the reference position of the image. To measure the elongation between the marked lines.

[0004]

In a tensile test of a test piece, when a strain measurement, a breaking elongation measurement, or the like is performed, a distance between two mark lines attached to the test piece (a distance between the initial mark lines). It is important that distance is measured prior to the start of the test. Conventionally, this kind of measurement of the initial mark-to-mark distance has been performed exclusively using a measuring jig such as a caliper, but the measurement is troublesome and there is a problem in terms of measurement accuracy.

The present invention has been made in view of such circumstances, and has a function of easily and accurately measuring the distance between mark lines attached to a test piece to be subjected to a tensile test, It is an object of the present invention to provide a non-contact extensometer capable of achieving high accuracy such as strain measurement and elongation at break.

[0006]

In order to achieve the above-mentioned object, a non-contact extensometer according to the present invention is provided so as to be movable in a direction in which a test piece extends, and is provided at a predetermined distance in the elongation direction. First and second cameras that respectively capture two marked lines parallel to the piece, and the first and second cameras provided at the movement origin positions of the first and second cameras, respectively. First and second origin sensors for detecting the return of the origin position of the camera, respectively, and one of the reference lines picked up by the first and second cameras is set at a predetermined reference position in the image. When respectively adjusted, the means for measuring and storing the distance between the movement origin positions from the movement amounts of the respective cameras from the movement origin positions respectively defined by the respective origin sensors, and elongation of the test piece. Accompanying said The first and second cameras are respectively moved in accordance with the displacement of the marked line to determine the moving amount of each camera, and the distance between the marked lines is calculated from the moving amount of each camera and the distance between the movement origin positions. And means for measuring

That is, the non-contact extensometer according to the present invention comprises a first and a second camera for defining the moving origin positions of the first and second cameras which respectively image the two marked lines attached to the test piece.
Between the origin sensors (between the movement origin positions of the cameras) based on the movement amounts xo and yo of the cameras when one of the mark lines is imaged at the image center of the first and second cameras. ) Is measured, for example, as [zo = yo−xo], and from the movement amount x, y of each camera when the camera is moved while following the displacement of the marked line accompanying the elongation of the test piece, The distance z between the two marked lines is, for example, [z
= Zo + xy].

[0008]

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 mounted on a material testing machine main body (not shown) and subjected to a tensile test, and R1 and R2 are test pieces S
Are two marked lines which are previously provided in parallel with a predetermined distance in the direction of extension. These marking lines R1 and R2 are linear marks drawn using paint or the like at a distance of, for example, 50 mm on the parallel portion of the test piece S. 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 main body of the material testing machine and measures the elongation of the test piece S in a non-contact manner with the test piece S is a high-magnification high-magnification device which images the mark lines R1 and R2. A first and a second camera 1, 2; and a light source 3, which is mounted on the side of each of the cameras 1 and 2 and illuminates an imaging area (each marked line portion of the test piece S) by the cameras 1 and 2. 4 is provided. Each of these cameras 1, 2 has a first and a second
Are supported by the movable stages 5 and 6, respectively, and are provided so as to be movable in parallel in the extending direction of the test piece S. 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.

The cameras 1 and 2 incorporate, for example, a CCD image sensor (area sensor) as an image sensor, and capture a partial surface image of the test piece S including 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.

Thus, first and second origin sensors 9 and 10 for detecting the return of the stages 5 and 6 to the origin positions are provided at the origin positions of the stages 5 and 6, respectively. I have. Each of these origin sensors 9 and 10 is, for example, a photocoupler (not shown) incorporated in a slit having a U-shape as shown in FIG. When the pieces 5a, 6a are positioned in the slits, they are optically detected to determine the presence of the sensing pieces 5a, 6a, and thus the stages 5, 6 to the position where the origin sensors 9, 10 are attached. This is to detect positioning.

The positions of the moving origins of the stages 5, 6 defined by these origin sensors 9, 10 and, consequently, the cameras 1, 2 mounted on the stages 5, 6 respectively.
Is initially set in advance according to the specifications of the tester main body and the like. The distance between the mounting positions of these origin sensors 9 and 10 (the distance between the moving origin positions) is, as described later, the distance between the cameras 1 and 2 when one of the marked lines is imaged by the cameras 1 and 2 respectively. It is measured with high accuracy based on the movement amount, and is stored in the memory 17 described later.
The measurement of the distance between the movement origin positions and the storage of the measured distance in the memory 17 are executed when the origin sensors 9 and 10 are attached or when the attachment positions are adjusted.

As described above, partial surface images (images) of the test piece S including the marked lines R1 and R2 captured by the cameras 1 and 2 are output to the CPs via the image processing units 11 and 12, respectively.
The image data is taken into the arithmetic processing unit 13 made of U, subjected to predetermined image processing, and displayed on the display 14. The display 14 is configured to display, in, for example, two image display areas set side by side in parallel, images (processed images) each including each of the marked line images subjected to the image processing by the arithmetic processing unit 13. . In addition, while the raw images captured by the cameras 1 and 2 are directly displayed on a TV monitor (not shown), the processed images including the reference lines R1 and R2 obtained by the arithmetic processing unit 13 are displayed. May be displayed on the display 14.

The display 14 displays, for example, a soft switch for manually operating the movement of the cameras 1 and 2 (stages 5 and 6) and a soft switch for instructing initial settings and the like for the cameras 1 and 2. And 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.

On the other hand, the arithmetic processing unit 13 shown in FIG.
Has a function of detecting a mark image in an image captured by each of the cameras 1 and 2 according to a software application for elongation measurement prepared in advance and obtaining a center of gravity of the mark image as described later. ing. The reference line is positioned at the reference position from the difference (distance on the image) between the barycenter position of the reference line image obtained in each image and a preset reference position (eg, image center) in each image. The amount of deviation of the marked lines from the state in which they were moved, and thus the displacement positions of the marked lines R1 and R2 due to the elongation of the test piece S are detected. Incidentally, this calculation is based on, for example, the imaging magnification of the cameras 1 and 2 and the CC.
The distance (unit distance) between pixels in the image is determined in advance according to the pixel array pitch of the D image sensor, and the unit distance is multiplied by the difference (distance on the image). It should be noted that the image signals obtained by the cameras 1 and 2 are enlarged while appropriately performing an interpolation operation, and the displacement positions of the reference lines R1 and R2 are detected from the enlarged image to obtain the measurement accuracy. Can also be increased.

When the mark image deviates from the images picked up by the cameras 1 and 2, respectively, in other words, the position of the mark lines R1 and R2 is determined by the elongation of the test piece. Each camera 1 and 2
When the limit of the imaging range is reached, the position controllers 15 and 16 are activated. Then, according to 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, the position control unit 15,
Under the control of 16, the pulse motors 7 and 8 are respectively driven to move the cameras 1 and 2 in the moving directions of the marking lines R1 and R2 accompanying the elongation of the test piece S, respectively. The movement of each of the cameras 1 and 2 by the position controllers 15 and 16 is performed 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 position of each of the cameras 1 and 2 is controlled so that the reference lines R1 and R2 are captured at the reference position in the captured image. Specifically, the pulse motors 7 and 8 are driven to move the cameras 1 and 2 by an amount corresponding to the difference between the barycenter position of the mark image obtained from each image and the reference position of the screen. Accordingly, the positions of the cameras 1 and 2 are changed following the movement of the reference lines R1 and R2 accompanying the elongation of the test piece S.

The first feature of the present invention in the non-contact extensometer configured as described above is that, as described above, the distance between the mounting positions of the origin sensors 9 and 10 (the distance between the moving origin positions) zo. Is measured in advance with high accuracy, and the measured distance zo is stored in the memory 17. Then, the cameras 1 and 2 are caused to follow the distance zo and the displacement amount of the mark lines R1 and R2 displaced with the elongation of the test piece, for example, such that the mark lines R1 and R2 are centered on the screen. In the case of moving the cameras 1 and 2, the second feature point is to measure the distance (elongation) between the reference lines R1 and R2 from the movement amounts x and y of the cameras 1 and 2.

That is, the measurement of the distance zo between the movement origin positions is performed by measuring the distance zo applied to the test piece S as shown in FIG.
Each of the cameras 1 and 2 is moved so that one of the marked lines, for example, the marked line R1 mounted on the tester main body and positioned on the upper side is positioned at the center of the screen (a reference position on the screen). The movement amounts xo and yo from the movement origin positions of the cameras 1 and 2 (where the origin sensors 9 and 10 are attached) are obtained. Then, the distance zo between the movement origin positions is calculated as zo = yo−xo from these movement amounts xo and yo,
The measurement distance zo is stored in the memory 17.

More specifically, as shown in FIG. 4, after the test piece S is mounted on the main body of the tester, the upper camera 1 is first moved [Step S1].
A reference line R1 attached to the test piece S is captured at a reference position for a predetermined time in an image to be captured, for example, at the center of the screen [Step S2]. Then, the movement amount xo from the movement origin position defined as the attachment position of the origin sensor 9 of the camera 1 at this time is obtained [Step S3]. The movement amount xo of the camera 1 is obtained as the movement amount (number of rotations) of the camera 1 by the pulse motor 7 or the like.

After the movement amount xo of the camera 1 is obtained in this way, the camera 1 is retracted to an upper position [Step S4]. Then, the lower camera 2 is moved [Step S5], and the mark R1 is captured at the center of the screen in the image captured by the camera 1 [Step S6]. Then, the movement amount yo from the movement origin position defined as the mounting position of the origin sensor 10 of the camera 1 at this time is obtained [Step S7].

When the cameras 1 and 2 respectively capture the mark R1 at the center of the screen, the cameras 1 and 2
When the movement amounts xo and yo from the origin sensors 9 and 10 are obtained, the distance between the origin sensors 9 and 10 according to the movement amounts xo and yo, that is, each camera 1,
The distance zo between the movement origin positions is calculated as zo = yo-xo [Step S8], and the measured distance zo is stored in the memory 17 [Step S9]. That is, the cameras 1 and 2 are moved so that the cameras 1 and 2 respectively capture one of the two marked lines R1 and R2 attached to the test piece S, and the amount of movement of these cameras 1 and 2 If xo and yo are obtained, the distance zo between the movement origin positions can be obtained with high accuracy as a difference between these movement amounts xo and yo.

When the distance zo between the origins of movement is determined as described above, the elongation of the test piece S in the tensile test is measured using the distance zo between the origins of movement as follows. (Second feature point). This elongation measurement is performed by following the displacement of the two marked lines R1 and R2 accompanying the elongation of the test piece S as shown in FIG. 5 and capturing the marked line marks R1 and R2 at the center of the screen. Then, the cameras 1 and 2 are moved, and the movement amounts x and y of the cameras 1 and 2 are measured and executed.

More specifically, as shown in FIG. 6, after the test piece S is mounted on the tester main body, first, the upper camera 1 is moved [Step S 11], and the center of the screen is set. The line R1 is captured [Step S1
2]. In addition, the camera 2 below is moved to [Step S1
3] The mark line R2 is captured at the center of the screen [Step S14]. With the above processing, the initial setting for the tensile test is completed.

Thereafter, the tester main body is driven to apply a tensile load to the test piece S to start the test [Step S15]. During the execution of the tensile test, the cameras 1 and 2 are respectively moved so as to follow the displacement of the marking lines R1 and R2 accompanying the elongation of the test piece S and to capture the marking lines R1 and R2 at the center of the screen. Move [Step S
16]. At this time, the movement amount x of the camera 1 and the camera 2
Are measured respectively [Steps S17, S1
8]. Then, the movement amounts x and y of these cameras 1 and 2,
The distance z between the movement origin positions stored in the memory 17
Based on o, the distance z between the reference lines R1 and R2 is calculated as z = zo + xy (step S19). Such a mark R
The measurement of the distance z between R1 and R2 is repeatedly executed until the end of the test is determined [Step S20].

As described above, according to the non-contact extensometer having the function of measuring the distance zo between the movement origin positions and the distance z between the reference lines R1 and R2,
In addition, since the distance zo between the moving origin positions can be obtained with high accuracy, the measurement accuracy can be greatly increased.
In addition, the distance between the movement origin positions zo of the cameras 1 and 2 is measured by effectively utilizing the cameras 1 and 2 which are the measuring means, in other words, by using the same measuring system as the measuring system of the amount of elongation. No error factor due to the difference is mixed.

Also, with a simple configuration of providing the origin sensors 9 and 10 for defining the origin positions of the cameras 1 and 2, it is possible to measure the distance zo between the origin positions with high accuracy and to obtain the mark R
There are many practical effects such as realizing highly accurate measurement of the distance z between R1 and R2. Since the measurement of the distance zo between the moving origin positions described above only needs to be performed once when the positions of the origin sensors 9 and 10 are set, there is no possibility that the test efficiency is impaired by this.
(Because it can be automated), there is an effect that the labor is hardly required.

The two mark lines R1, R attached to the test piece S
In the case of measuring the initial distance between the marked lines 2, for example, prior to the start of the test, the cameras 1 and 2 use the marked lines R 1 and R 2.
When the initial adjustment is performed so that each of the cameras 1 and 2 is captured at the center of the screen, the movement amounts x and y from the movement origin positions of the cameras 1 and 2 may be obtained. Marking line R
When calculating the distance z between R 1 and R 2, for example, without moving the cameras 1 and 2, each of the markers 1 and 2 is calculated based on the displacement amount of each mark image in the screen imaged by each of the cameras 1 and 2. It is also possible to obtain the displacement amounts x and y of the lines R1 and R2, and calculate from the displacement amounts x and y as described above. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0028]

As described above, according to the present invention, there are provided origin sensors for respectively defining the moving origins of the cameras for imaging the two marked lines attached to the test piece, respectively. Since the distance is measured in advance by using the measurement system by the camera and stored, the distance between the marked lines can be measured simply and with high accuracy without any need for labor. In addition, a great effect in practical use can be obtained, for example, the measurement of elongation in a tensile test can be performed with high accuracy.

[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 showing an example of an origin sensor incorporated in the non-contact extensometer shown in FIG.

FIG. 3 is a diagram showing an outline of distance measurement between origin sensors (between camera origin positions), which is a first characteristic point of the present invention.

FIG. 4 is a view showing a processing procedure for measuring a distance zo between movement origin positions shown in FIG. 3;

FIG. 5 is a diagram showing an outline of measurement of a distance between marked lines, which is a second feature point of the present invention.

FIG. 6 is a view showing a processing procedure of a reference line distance measurement shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st camera 2 2nd camera 5 1st moving table 6 2nd moving table 7,8 Pulse motor 9,10 Origin sensor 11,12 Image processing part 13 Operation processing part 14 Display 15,16 Position control part S Test piece R1, R2 Marked line

Continuation of the front page F term (reference) 2F065 AA02 AA07 AA09 AA17 BB13 BB27 CC00 DD00 DD06 FF04 FF67 GG04 GG13 HH12 JJ03 JJ05 JJ26 PP02 PP22 QQ23 QQ24 QQ25 SS01 SS02 SS13 TT00 2G061 AA01 EB07 EA02

Claims (1)

[Claims] 1. A non-contact extensometer for optically detecting the elongation of a test piece subjected to a tensile test in a non-contact manner with the test piece, wherein the non-contact extensometer is provided so as to be movable in the elongation direction of the test piece. First and second cameras that respectively image two marked lines parallel to the test piece at a predetermined distance in the elongation direction, and at a movement origin position of the first and second cameras. A first and a second origin sensor respectively provided for detecting a return of the origin position of the first and second cameras, and one of the reference lines imaged by the first and second cameras is When adjusted to a preset reference position in an image, the distance between the movement origin positions is measured and stored based on the movement amount of each camera from the movement origin position defined by each of the origin sensors. Means; The first and second cameras are respectively moved by following the displacement of each of the marked lines accompanying the elongation of the test piece to determine the amount of movement of each camera, and the distance between the amount of movement of each camera and the movement origin position And a means for measuring the distance between the reference lines from (a) to (c).