JPH11304437A - Non-contact ductilometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively position the cameras to the reference lines of a plurality of specimens in a lot by fitting the positions of two reference lines of the photographed specimen to the reference positions in an image, and measuring the elongation of the specimen on the basis of the positions of the cameras and the positions of the reference lines in the image in accordance with the displacement of the reference lines. SOLUTION: The cameras 1, 2 photographing the reference lines R1 , R2 on a specimen S are supported by the moving stages 5, 6, and movable in parallel in the elongating direction of the specimen S. A partial surface image of the specimen S photographed by the cameras 1, 2 and including the reference lines R1 , R2 are taken in a processing part 13 through the image processing parts 11, 12, and the processed images are displayed in parallel on a display 14. The operating part 13 detects the reference line image in each image, and detects the deviating quantity of the reference line from that located on the reference position, that is, the displacement position of the reference lines R1 , R2 in accompany with the elongation of the specimen S, on the basis of the difference between the position of the center of gravity and the predetermined reference position in the image.

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 for measuring the elongation of a test piece subjected to a tensile test in a non-contact manner with the test piece. The present invention relates to a non-contact extensometer capable of improving test efficiency for a plurality of test pieces having a large number.

[0002]

2. Related Background Art A tensile test of various test pieces using a material testing machine is performed by applying a tensile load to the test pieces and measuring the tensile load and the elongation of the test pieces. 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 change in the distance between these marked lines. Is used to determine the elongation.

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]

By the way, test pieces to be subjected to this type of test are often provided as a lot in which a plurality of test pieces of the same shape are put together. By comprehensively evaluating, the test results are required.

However, in this case, each time a new test piece is mounted on the material testing machine, it is necessary to adjust the position of the camera with respect to the marked line attached to the test piece, and the initial setting process is very troublesome. There is a problem to say. In particular, the camera is configured to capture a surface image of the test piece including the reference line at a large imaging magnification to obtain a high-resolution image in order to compensate for sufficiently high measurement accuracy. For this reason, the view range of the camera is narrow, and it is undeniable that the initial setting itself of the camera position with respect to the marked line is troublesome.

The present invention has been made in view of such circumstances, and an object of the present invention is to adjust the position of a camera with respect to mark lines attached to a plurality of test pieces to be subjected to a tensile test in lot units. An object of the present invention is to provide a non-contact extensometer which can be efficiently executed and which can improve test efficiency.

[0007]

In order to achieve the above-mentioned object, a non-contact extensometer according to the present invention comprises two non-contact extensometers attached in parallel to a specimen at a predetermined distance in the direction of extension of the specimen. First and second cameras that respectively image the marked lines, and first and second moving stages that support these cameras movably in the direction in which the test piece extends, respectively, and are subjected to a tensile test. Detecting the elongation of the test piece in a non-contact manner with the test piece based on the image of the marked line imaged by each of the cameras, and in particular, prior to the start of the tensile test, the first and the second The moving stage is driven to adjust the position of each mark in the image captured by each camera to the reference position of the image (camera position initial setting means). The position of each of the cameras is stored (storage means), and the first and second moving stages are driven in accordance with the displacement of the marking line accompanying the elongation of the test piece due to the execution of the tensile test. The elongation of the test piece is measured based on the position of each camera and the position of the marked line in the image taken by each camera (measuring means). When the tensile test is completed, each of the stored The apparatus is characterized in that the first and second moving stages are driven in accordance with the position of the camera to return each camera to the initially set position (origin return means).

That is, according to the present invention, a marked line used for optical elongation measurement attached to a test piece is attached to substantially the same position of a plurality of test pieces belonging to the lot for each lot. Prior to the start of the tensile test, the camera position was initialized by adjusting the position of each marked line in the image captured by each camera to the reference position of the image, and the initial setting of this camera was performed. Remember the position. Then, while moving the camera while following the displacement of the marked line with the execution of the tensile test, the elongation of the test piece was measured from the position of the marked line image in the image, and when the tensile test was completed, Control means (origin return means) for returning the cameras to the stored initial setting positions is provided.

According to a preferred aspect of the present invention, in the camera position initial setting means, the positions of the first and second cameras are roughly adjusted to positions where the respective marked lines are respectively viewed. After the adjustment, the positions of the first and second cameras are finely adjusted according to the positions of the marked lines in the images respectively captured by the cameras so that the positions of the marked lines become the reference positions of the images. It is characterized by doing.

[0010]

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, wherein S is a test piece mounted on a material tester (not shown) and subjected to a tensile test, and R1 and R2 are the test pieces described above. S are two marked lines which are previously provided in parallel with each other in the extending direction at a predetermined distance. These marking lines R1,
R2 is a straight line mark drawn using a paint or the like at a distance of, for example, 50 mm on a 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 that is incorporated in a 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 second-order extensometer that images each of the marked 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 by first and second moving stages 5 and 6, respectively, and are provided so as to be able to move 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.

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, as described later, so that 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. Is taken into the arithmetic processing unit 13 consisting of
After predetermined image processing is performed, the images are displayed in parallel on the display 14 as shown in FIG. 2, for example. Specifically, as shown in FIG. 2, the arithmetic processing unit 1 is provided in two image display areas A and B set in parallel on the display 14.
An image (processed image) including each of the marked line images subjected to the image processing in 3 is displayed. Incidentally, here, since the display 14 is a horizontally long display screen, the extending direction of the test piece S is set in the horizontal direction, and the image display areas A and B are displayed so that the images are displayed side by side in the horizontal direction. Is set. While the raw images captured by the cameras 1 and 2 are directly displayed on a TV monitor (not shown), the mark lines R1 and R1 obtained by the arithmetic processing unit 13 are displayed.
A processed image including each of R2 may be displayed on the display 14.

As shown in FIG. 2, the display 14 displays a soft switch for manually operating the movement of the cameras 1 and 2 and a soft switch for instructing initial settings for the cameras 1 and 2. In addition to the operation area C, a graph display area D for graphically displaying the relationship between the load and the elongation measured by the tensile test is provided. 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, the arithmetic processing unit 13 changes the positions of the mark lines R1 and R2 due to the extension 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 the amount corresponding to the difference between the barycentric position of the mark image obtained from each image and the reference position of the screen. Thus, 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.

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 described. Two mark lines R1 attached to the test piece S will be described. , R2 gradually move upward along with the elongation of the test piece S due to the upward pulling of the test piece S as shown in FIG. Therefore, each mark R1, R
If the two cameras 1 and 2 that respectively capture the image 2 are translated in the upward direction along with the movement of each of the above marked lines R1 and R2, each of the marked lines R1 and R2 is always captured at the center of the image. The amount of elongation of the test piece S can be obtained from the moving distance of each of the cameras 1 and 2.

Specifically, the upper camera (first camera) 1
Movement amount a C _H of, when the lower camera (second camera) 2 for movement amounts and C _L, elongation amount E between the marked line of the test piece S is be determined as E = C _H -C _L it can.

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 that the marked lines R1 and R2 associated with the elongation of the test piece S. Can also be obtained for each position. Specifically, as shown in FIGS. 4A and 4B, displacement amounts L _H and L _L of the reference lines R1 and R2 from the reference position in the images captured by the cameras 1 and 2 are respectively obtained. . And it can also be determined these reference lines R1, R2 in the displacement amount L _H, the elongation amount E between the marked line of the test piece S as described above from L _L equivalently as E = _{L H} -L L. The displacement L
_H, L _L is the displacement of the marked line image detected on the image is obtained by multiplying a coefficient which depends on the pixel pitch and the imaging magnification and the like.

However, there is a limit to the amount of elongation E between the marked lines that can be obtained in this way, and the marked lines R1 and R2 are
If it deviates from the field of view of 2, it cannot be measured naturally. Therefore, the arithmetic processing unit 13 monitors the display position of the mark image displayed in each of the image display areas A and B. Then, when the position reaches the limit of a predetermined imaging range of each image, each of the cameras 1 and 2 catches the mark lines R1 and R2 at their reference positions by driving the pulse motors 7 and 8. Thus, the camera position is moved. Then, while adding the movement amounts C _H and C _L of the cameras 1 and 2 at this time, as described above, the displacement amounts L _H and L _L of the marking lines R1 and R2 obtained from the positions of the marking lines images in each image as described above. based on E the elongation amount E between marked lines _{= (L H + C H)} - has become a obtained as _{(L L} + C _L).

Next, a description will be given of a process of detecting a marked line image in an image captured by each of the cameras 1 and 2. The detection of the position of the marked line image in the image captured by each of the cameras 1 and 2 is performed, for example, as shown in FIG.
As shown in (b), the concept is obtained by obtaining the position of the center of gravity of the image signal component based on the distribution of the image signal level in the direction of extension of the test piece S.

More specifically, an image signal captured including the reference line R is focused on, for example, the level N of a noise component depending on the surface state of the test piece S. Extract only image signal components. Then, the position of the center of gravity of the distribution of the image signal in the extension direction in the extracted image signal area is evaluated as the position of the mark image. That is, the distribution of the image signal component (for example, the luminance signal level) in the extension direction of the test piece S is obtained, and the barycenter position G of the mark image is obtained from the distribution of the image signal component.
More specifically, each position m in the elongation direction of the test piece S (m = 1,
2,3, when the level of the image signal is a A _m in ...),
The distribution of the image signal is shown as a sequence of A ₁ , A ₂ , A ₃ ,. Since the center of gravity G of the distribution of the image signal is represented as the center of gravity of the area represented by the signal sequence A ₁ , A ₂ , A ₃ ,..., G = Σ (m · A _m ) / ΣA _m (M = 1, 2, 3,...). The center of gravity G of the distribution of the image signal obtained in this way reflects the distribution shape itself, and is hardly affected by the elongation of the reference line R and the level change of the image signal accompanying this. , Can be regarded as the reference position of the reference line R itself.

When the image signal is binarized at a predetermined level, as shown in FIGS. 5 (a) and 5 (b),
It cannot be denied that the width of the reference line R shown as a binarized signal changes depending on the binarization level. In particular, since the level change of the image signal is greatly affected by the degree of elongation like the edge portion of the marking line R, the width of the marking line R greatly changes depending on the level of the set binarization threshold.
In addition, when the level of the image signal greatly changes due to noise, it cannot be denied that the level is affected by the noise.

In this regard, if the center of gravity G is obtained from the distribution of the image signal (image signal level A) as described above, an error factor accompanying the binarization does not enter, so that the reference line R (reference line image) Can be simply and highly accurately evaluated as the position of the center of gravity. In particular, as shown in FIG. 5 (b), the mark R
Is widened and the level A of the image signal is low, the position (center of gravity) of the reference line R can be accurately detected. As described above, the test piece S
The noise component is removed in accordance with the level N of the noise component corresponding to the surface state of the test piece S, and attention is paid only to the image signal component in the image signal area exceeding the level N. Without being affected, the position of the center of gravity G of the marked line image can be detected, and the position of the marked line R (marked line image) can be accurately obtained.

The detection of the position of the center of gravity based on the distribution of the image signals described above is more preferably performed, for example, as shown in FIG.
The projection component (sum of the image signal) of the image signal at each position in the direction orthogonal to the direction of extension of the test piece S is obtained, and the center of gravity G is obtained from the distribution of the projection component in the extension direction.
What should I do? Thus, the area region including the marked line image, it means that the center of gravity is determined in a three-dimensional space of said image signal component in said area region, blurring at the edge portion R _E of the marked line R Even when the edge itself becomes unclear due to fluctuation or fluctuation, there is an advantage that the position (center of gravity) of the reference line R can be accurately obtained without being influenced by the edge. .

Basically, the non-contact extensometer according to the present invention, which is provided with the above-described functions, is characterized in that the arithmetic processing section 13 starts the tensile test prior to the start of the tensile test. And a function for initializing the positions of the cameras 1 and 2 (camera position initializing means) and a function for storing the initial setting positions (camera position storing means). Marking line R1, accompanying the elongation of test piece S by execution
Function for returning the positions of the cameras 1 and 2 moved following the displacement of R2 to the initial position (origin) (origin return means)
It is in the point with. Here, the origin refers to the initial center of gravity position of the image taken by the cameras 1 and 2 of the reference lines R1 and R2 attached to the first test piece S in the lot.

Explaining these characteristic functions, the camera position initial setting means and the camera position storage means are realized by, for example, the processing procedures shown in FIGS. The origin return means is realized by, for example, the processing procedure shown in FIG. In these processing procedures, while processing the images of the surface image of the test piece S captured by the cameras 1 and 2,
The operation is performed by driving the pulse motors 7 and 8 via the reference numerals 5 and 16, respectively, thereby moving the cameras 1 and 2 up and down to adjust their positions (camera positions).

That is, the initial setting processing shown in FIGS. 7 to 11 is executed before the tensile test is started after the first test piece S is mounted on the material testing machine. This process
First, various error detection processes are executed and started after confirming that no error has occurred [step S
1]. When occurrence of an error is detected, a recovery process for the error is executed as a matter of course.

If it is confirmed that there is no error, then it is determined whether or not the first camera (upper camera) 1 has captured the mark R1 in its field of view [step S2]. This determination is made to determine whether or not a mark image whose level is significantly different from the image signal level corresponding to the surface portion of the test piece S serving as the background is detected in the image captured by the camera 1. It is done by things. However, when a mark is detected from the image captured by the camera 1, it is similarly determined whether or not the second camera (lower camera) 2 has captured the mark R2 in its field of view. [Step S3]. Incidentally, even when the camera 1 does not view the mark R1 in the field of view,
Similarly, it is determined whether or not the second camera 2 is capturing the mark R2 [Step S4].

When it is confirmed that the cameras 1 and 2 respectively capture the marking lines R1 and R2 in their respective fields of view in the determination processing of the steps S2 and S3, 2 It is determined that the positions of the first and second cameras 1 and 2 are roughly adjusted (coarsely adjusted) with respect to the two marked lines R1 and R2. In this case, the center of gravity G of the mark image is obtained from the images obtained by the cameras 1 and 2 as described above, and the center of gravity G of the mark image and the reference position of the image are determined. Are obtained [Step S5]. Then, based on the distance on each image, the imaging reference position (camera position) of the cameras 1 and 2
And the actual shift amount between the center of gravity of the image of each of the marked lines R1 and R2 is calculated as the camera movement amount so as to capture the marked lines R1 and R2 at the reference positions of the images captured by the cameras 1 and 2, respectively. [Step S6].

The pulse motors 7, 8 are respectively driven via the position control units 15, 16 in accordance with the camera movement amounts obtained in this manner, so that the center of gravity G of the mark image becomes the image reference position. , In other words, each mark R
The positions of the cameras 1 and 2 are adjusted so that the images of R1 and R2 are respectively captured at the reference positions of the images [Step S
7]. By such position control, each of the cameras 1 and 2 is initially set to the positions of the marking lines R1 and R2 attached to the test piece S (the center of gravity of the marking line substantially overlaps the reference position). Is stored as the origin position in each of the test pieces of the lot including the test piece S in the tensile test [Step S8]. Are stored as the origin positions in the tensile test, respectively (step S8).

When the lower camera 2 does not catch the mark R2 in spite of the fact that the upper camera 1 catches the mark R1, the following processing is performed as shown in FIG. A rough adjustment process is performed on the lower camera 2. In this process, the lower camera 2 is first moved gradually downward (step S11), and before the lower camera 2 reaches its lower limit end, the mark R
It is determined whether or not No. 2 is detected [Steps S12, S1
3]. When the camera 2 moves downward, the marking line R2
Is detected, it is determined that the coarse adjustment for the lower camera 2 has been completed, and the process returns to the fine adjustment process from step S5 shown in FIG. 7 described above. On the other hand, if the mark R2 is not detected by the lower camera 2 despite reaching the lower limit, this is determined as an error [Step S12]. Then, the error recovery process [Step S1
4], the following start position return processing of the lower camera 2 [Step S15] is executed.

After the start position return processing has been performed, the lower camera 2 is gradually moved upward (step S16). It is sequentially determined whether or not 2 has reached the upper limit of the movement (steps S17, S18), and it is determined whether or not the lower camera 2 detects the mark R2 (step S19). If the lower camera 2 is moved upward to detect the mark R2, it is determined that the coarse adjustment for the lower camera 2 has been completed, and the process returns to the fine adjustment process from step S5 shown in FIG. .

By performing the rough adjustment for the lower camera 2 according to such a processing procedure, the marking line R2 is captured not only by the upper camera 1 but also by the lower camera 2. When contact with the upper camera 1 is detected during the upward movement of the lower camera 2 [Step S17], or when it is detected that the lower camera 2 has reached the upper limit of the movement [Step S18]. ], Some abnormality (error)
As a result, the series of initial setting processing described above is stopped.

On the other hand, after it is determined in step S2 shown in FIG. 7 that the upper camera 1 has not captured the mark R1, it is confirmed in step S4 that the lower camera 2 has captured the mark R2. In such a case, the rough adjustment process shown in FIG. 9 is executed. This process is basically the same as the coarse adjustment process for the lower camera 2 shown in FIG. 8, and is executed by changing the direction of movement of the camera 1.

More specifically, while gradually moving the upper camera 1 upward (step S21), it is determined whether or not the upper camera 1 detects the mark R1 before the upper camera 1 reaches its upper end. Judge [Steps S22, S23]. When the marker line R1 is detected, it is determined that the coarse adjustment for the upper camera 1 has been completed, and the process returns to the fine adjustment process from step S5 shown in FIG. On the other hand, the mark R1
Is not detected, an error recovery process [Step S
24], the start position return process of the upper camera 1 [Step S25] is executed.

After the start position return processing of the upper camera 1 is performed, it is determined whether or not the mark R1 is detected while the upper camera 1 is gradually moved upward [step S26]. [Step S29]. At this time, the 2
It is sequentially determined whether the two cameras do not touch each other, or further, reaches the lower limit of the movement [Steps S27 and S28]. When these abnormalities are detected, the series of processing is stopped.

When the mark R1 is detected by the downward movement of the upper camera 1, it is determined that the coarse adjustment for the upper camera 1 has been completed, and the fine adjustment from step S5 shown in FIG. Return to processing. That is, by performing the coarse adjustment on the upper camera 1 according to the above-described processing procedure, the mark line R1 is captured not only by the lower camera 2 but also by the upper camera 1.

In the determination process shown in FIG. 7, when it is determined that neither the upper camera 1 nor the lower camera 2 is capturing the marking lines R1 and R2, the processing procedure shown in FIGS. 10 and 11 is executed. Is done. This processing is also basically performed in the same manner as the coarse adjustment processing shown in FIGS. 8 and 9 described above. In this case, while first moving the lower camera 2 downward [step S31], the lower end It is determined whether or not the marking line R2 is caught before reaching [Steps S32 and S33]. When the lower camera 2 catches the mark R2 by this processing procedure, the process shifts to the above-described coarse adjustment processing of the upper camera 1 shown in FIG.

However, if the lower line 2 does not detect the mark R2 even though the lower camera 2 has reached its lower limit, an error recovery process for this is waited (step S34), and the lower camera 2 is once started. It returns to the position [Step S35]. Then, while moving the upper camera 1 upward (step S36), it is determined whether or not the marking line R1 can be captured before reaching the upper end thereof (steps S37, S38). Then, when the upper camera 1 catches the mark line R1 by this processing procedure, the processing shifts to the above-described coarse adjustment processing of the lower camera 2 shown in FIG.

On the other hand, if the mark R1 is not detected even though the upper camera 1 has reached its upper limit,
Wait for an error recovery process for this [Step S3
9] Then, as shown in FIG. 11, the upper camera 1 is temporarily returned to its start position [Step S41].

Thereafter, while gradually moving the lower camera 2 upward (step S42), it is determined whether or not the marker R2 is detected by the lower camera 2 (step S43). At this time, it is sequentially determined whether the two cameras do not touch each other or whether the two cameras have reached the upper limit of the movement [Steps S43 and S44]. If these abnormalities are detected, the series of processing is stopped. . When the lower camera 2 catches the mark R2 by this processing procedure, the process shifts to the above-described coarse adjustment processing of the upper camera 1 shown in FIG.

By executing the processing shown in FIGS. 8 to 11 as described above, when the upper camera 1 or the lower camera 2 does not catch the marking lines R1 and R2, the cameras 1 and 2 are changed according to the situation at that time. The camera position is roughly adjusted so that the cameras 2 are controlled to move so that the cameras 1 and 2 respectively capture the marked lines R1 and R2. Then, in a state where the cameras 1 and 2 respectively capture the marking lines R1 and R2, the above-described step S shown in FIG.
The processing shown in steps S5 to S7 is executed to perform alignment with respect to each of the marking lines R1 and R2, and the position is stored as the origin position.

When the setting of the initial positions for the cameras 1 and 2 is completed as described above, a tensile test is performed on the test piece S according to the processing procedure shown in FIG.
This process is executed in a state where the test piece S is mounted on the material testing machine, after waiting for a test start instruction. Then, while applying a tensile load to the test piece S under test conditions set in advance, the tensile load at that time and the elongation of the test piece S by the non-contact extensometer configured as described above, specifically, This is executed while measuring the elongation between the two marked lines R1 and R2 at a predetermined cycle, respectively (step S52).

Incidentally, such a tensile test is repeatedly executed until, for example, the breakage of the test piece S due to the pulling is detected [Step S53]. In addition, when it is confirmed that the test piece S has been elongated to the preset amount of elongation, the tensile test may be terminated at that time. If the test piece S breaks and the tensile test is completed, the broken test piece S is removed from the material testing machine. If the tensile test is completed before breaking, the tensile load at that time is released and the test piece S
Is removed.

Thereafter, the material testing machine is subjected to a tensile test for the next test piece S. At this time, in the non-contact extensometer according to the present invention, the cameras 1, 2 stored as described above are used. According to the default location information,
Each of the cameras 1 and 2 is caused to return to the initial setting position at the origin (step S54). By returning the cameras 1 and 2 to the origin, the marking lines R1 and R attached to the next test piece S of the same lot which is next mounted on the material testing machine.
The cameras 1 and 2 are aligned with respect to 2, respectively.

That is, in the non-contact extensometer according to the present invention, when a plurality of test specimens S of the same specification grouped as one test unit are repeatedly subjected to the tensile test in order, each of the test specimens S is attached. Noting that the marked lines R1 and R2 are substantially the same position, the positions of the cameras 1 and 2 aligned with the test piece S first mounted on the material testing machine are stored as the initially set origin. , One test piece S
Each time the tensile test for
By returning 2 to the initialization origin, the cameras 1 and 2 can be efficiently positioned with respect to the marked lines R1 and R2 of the test piece S to be mounted next on the material testing machine. I have. Therefore, the time and effort required for aligning the cameras 1 and 2 with respect to the plurality of test pieces S which are repeatedly executed in order can be greatly simplified, and the work efficiency can be improved.

Further, a test piece S to be temporarily mounted on a material testing machine
Even if there is some deviation in the mounting position of, or even if there is some deviation in the positions of the marking lines R1 and R2 attached to the test piece S, the cameras 1 and 2 are returned to the origin as described above. The marking lines R1 and R2 can be reliably captured by the cameras 1 and 2, and the deviation can be corrected easily and accurately. Therefore, every time the test piece S is mounted on the material testing machine,
Compared with the case where the position adjustment of the cameras 1 and 2 is performed, there is a great practical effect that the setting process can be performed easily and efficiently.

The present invention is not limited to the above embodiment. Here, the case where the elongation is measured while applying a tensile load upward to the test piece S mounted on the material testing machine has been described as an example, but the same applies to the case where a tensile load is applied downward. be able to.
Also, as for the detection processing of the marked line image in the images captured by the cameras 1 and 2, a conventionally proposed method such as a binarization processing can be appropriately used. Camera 1,
Various methods can also be used for the second moving means. In short, the present invention can be variously modified and implemented without departing from the gist thereof.

[0051]

As described above, according to the present invention, the camera which captures the marked line attached to the test piece is initially set to its origin position according to the marked line prior to the start of the tensile test. When the pull test ends, the camera is provided with a function of returning the camera to an initial position according to the stored origin position. Therefore, in the case where a plurality of test pieces provided as a unit of one lot are repeatedly tested in order, the time required for the camera initial setting process is greatly simplified, and the test efficiency is greatly improved. The following effects can be obtained. In particular, simply providing a simple function of storing the initially set origin position and returning the camera position to the origin in accordance with the stored origin position has the effects of simplifying and effectively improving the processing efficiency. Can be done.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an example of a display screen on the non-contact extensometer according to the embodiment.

FIG. 3 is a diagram showing a positional relationship between movement of a marked line due to elongation of a test piece and a camera for imaging the marked line.

FIG. 4 is a view for explaining the principle of detecting the position of a marked line on an image in the non-contact extensometer according to the present invention.

FIG. 5 is a diagram showing the principle of detecting the position (center of gravity) of a mark image in an image, which is a characteristic processing function of the present invention.

FIG. 6 is a schematic diagram for explaining the effect of detecting the center of gravity of a mark using projection of an image signal in a specific image processing area.

FIG. 7 is a diagram showing an initial setting processing procedure of camera alignment with respect to a marked line attached to a test piece.

FIG. 8 is a diagram illustrating a rough adjustment processing procedure of a lower camera position, which is attached to the initialization processing procedure illustrated in FIG. 7;

FIG. 9 is a diagram showing a rough adjustment processing procedure of an upper camera position accompanying the initialization processing procedure shown in FIG. 7;

FIG. 10 is a diagram showing a part of a rough adjustment processing procedure of each camera position of the lower camera and the upper camera, which is attached to the initialization processing procedure shown in FIG. 7;

FIG. 11 is a diagram showing a remaining procedure of the coarse adjustment processing procedure shown in FIG. 10;

FIG. 12 is a diagram showing a procedure of executing a tensile test and returning the camera to the origin.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st camera 2 2nd camera 3,4 Light source 5 1st moving table 6 2nd moving table 7,8 Pulse motor 11,12 Image processing part 13 Arithmetic processing part 14 Display 15,16 Position control part S Test piece R1, R2 Marked line

Claims (2)

[Claims] 1. A non-contact extensometer for optically detecting the elongation of a test piece to be subjected to a tensile test in a non-contact manner with the test piece, wherein the extensometer is provided at a predetermined distance in the elongation direction of the test piece. First and second cameras that respectively image two marked lines parallel to the test piece, and first and second movements that support these cameras movably in the direction of extension of the test piece, respectively. A stage, and a camera that drives the first and second moving stages prior to the start of a tensile test to adjust the position of each mark image in the image captured by each camera to a reference position of the image. Position initial setting means; means for storing the initially set positions of the respective cameras; and the first and second positions corresponding to the position displacement of the marked line accompanying the elongation of the test piece due to the execution of the tensile test. Moving While driving the image, measuring means for measuring the elongation of the test piece from the position of each camera and the position of the mark image in the image captured by each camera, when the tensile test is completed, Means for driving the first and second moving stages in accordance with the stored positions of the cameras to return the cameras to the initially set positions. 2. The method according to claim 1, wherein the first and second cameras roughly adjust the positions of the first and second cameras to view the respective reference lines, and then adjust the position of each of the markers in an image captured by each of the cameras. The non-contact extensometer according to claim 1, wherein the position of each mark is adjusted to a reference position of the image according to the position of the line.