JP2011169727A - Material testing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material tester unnecessary for marking a test piece with a gauge mark or the like even in a case that the displacement of a test piece is measured using the image taken by a camera. <P>SOLUTION: The material tester is equipped with an input part 34 for indicating the coordinates in the image region of the test piece, which are obtained by photographing the test by a video camera 15, as a measuring point; a measuring point memory part 25 for storing the data of the measuring point inputted by the input part 34; and a moving quantity measuring part 28 for measuring the moving quantity of the test piece passing the measuring point, in a state that test force is added to the test piece using template matching and a displacement quantity operation part 29 for operating the displacement quantity of the test piece on the basis of the moving quantity of the test piece measured by the moving quantity measuring part 28. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a material testing machine that executes a material test by applying a test force to a test piece.

  Such a material testing machine has, for example, a configuration in which a pair of screw rods are rotatably supported on a table in synchronization with each other, and both end portions of the crosshead are supported on these screw rods via nuts. Then, the crosshead is moved along the pair of screw rods by rotating the pair of screw rods in synchronization with each other by the rotation of the motor. A jig such as a gripping tool is connected to the crosshead and the table. And it is comprised so that a test force may be applied with respect to a test piece by moving a crosshead in the state which hold | gripped both ends of the test piece with jigs, such as these pair of grips.

  In such a material testing machine, the test force acting on the test piece is detected by a load cell or the like. Moreover, the displacement amount of the distance between the gauge marks in the test piece is measured by a displacement measuring unit. Then, a material test is performed based on these test force and displacement data.

  As this displacement measuring unit, a material testing machine using a video camera is also used. In such a material testing machine, in order to measure the displacement of the test piece, the test piece is photographed by a video camera, and the displacement amount of the test piece is calculated from the photographed image. More specifically, a standard mark or standard line is formed in advance on the surface of the test piece photographed by the video camera, and the movement amount of the standard mark or standard line is recognized. And this mark and mark are formed by marking them on the surface of a test piece, or sticking the seal | sticker on which the mark or mark was printed to a test piece (patent document 1). reference).

Japanese Patent No. 3799419

  When the non-contact displacement measurement method using the video camera as described above is adopted, the accuracy of the distance between the gauge points and the gauge lines has a great influence on the result of the material test. At this time, as described above, when marking a standard mark or standard line on the surface of the test piece, it is difficult to control the size of the marker point or the thickness or linearity of the line. Moreover, when sticking the seal | sticker in which the mark and the mark were printed on the test piece, control of the distance between seals and control of parallelism become difficult.

  For this reason, the structure which recognizes the characteristic part in the image of the test piece image | photographed with the television camera, and recognizes the displacement of a test piece based on the movement distance of this characteristic part is also considered. However, when such a configuration is adopted, there is a problem that points that can be measured are limited.

  The present invention has been made to solve the above problems, and it is not necessary to mark a test mark or the like on the test piece even when measuring the displacement of the test piece using an image taken by a camera. Is to provide a simple material testing machine.

  The invention according to claim 1 is obtained by photographing the test piece with the camera in a material testing machine that measures the displacement of the test piece by photographing the test piece to which the test force is applied with the camera. Measurement point designating means for designating coordinates in the image area of the test piece as a measurement point, and movement amount for measuring the movement amount of the test piece passing through the measurement point by pattern matching in a state where power is added to the test piece. It is characterized by comprising measurement means and movement amount calculation means for calculating the displacement amount of the test piece based on the movement amount of the test piece measured by the movement amount measurement means.

  According to a second aspect of the present invention, in the first aspect of the invention, the measurement point designating unit designates a plurality of coordinates in the image area as measurement points.

  According to a third aspect of the present invention, in the second aspect of the present invention, the movement amount measuring unit measures the movement amount of the image by template matching that compares the image captured by the camera with the template.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the moving amount measuring means uses a frame image as a template for a plurality of frame images photographed over time by the camera. The operation of comparing the template with the image of the next frame is repeated.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the movement amount measuring unit moves the template for each pixel and compares the image captured by the camera with the template.

  According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the movement amount measuring unit compares the image captured by the camera with the template by moving the template in units of one pixel or less.

  According to a seventh aspect of the present invention, in the invention according to the fourth aspect, the displacement amount calculating means is based on a moving amount of an image between an image of the first captured frame and an image of the last captured frame. Calculate the displacement of the test piece.

  The invention according to claim 8 is the invention according to claim 4, wherein the displacement amount calculation means calculates the displacement amount of the test piece by integrating the movement amount in the images of a plurality of frames taken over time. To do.

  According to the first aspect of the present invention, a mark or the like is marked on the test piece by designating an arbitrary coordinate in the image area of the test piece obtained by photographing the test piece with a camera as a measurement point. Therefore, the displacement can be accurately measured, and a highly accurate material test can be executed.

  According to the second aspect of the invention, since a plurality of coordinates in the image area are designated as measurement points, the displacement amount of the plurality of points can be calculated simultaneously, and the test piece is recognized as a surface and the displacement Can be certified.

  According to the invention described in claim 3, since the moving amount of the image is measured by template matching, the moving amount of the image can be measured accurately and easily.

  According to a fourth aspect of the present invention, the moving amount measuring means uses an image of a certain frame as a template for an image of a plurality of frames taken with time by the camera, and an image of the template and the next frame. Is repeated, the displacement of the test piece can be continuously recognized over time.

  According to the fifth aspect of the present invention, since the template is moved pixel by pixel and the image photographed by the camera is compared with the template, the amount of movement of the image can be measured in a short time. .

  According to the invention described in claim 6, since the template is moved in units of 1 pixel or less and the image photographed by the camera is compared with the template, the amount of movement of the image can be measured with high accuracy. It becomes.

  According to the invention described in claim 7, the displacement amount calculation means measures the movement amount of the test piece based on the movement amount of the image between the first photographed frame image and the last photographed frame image. Therefore, the displacement amount of the test piece can be accurately calculated without causing an error over time.

  According to the invention described in claim 8, the displacement amount calculation means starts the material test by measuring the amount of movement of the test piece by integrating the amount of movement in the images of a plurality of frames taken over time. Even when the image immediately after being moved exceeds the image processing range by the moving amount measuring means, the displacement amount of the test piece can be calculated.

1 is a schematic diagram of a material testing machine according to the present invention. 3 is a block diagram schematically showing a configuration of an arithmetic control unit 23. FIG. It is a schematic diagram which shows the relationship between the image of the test piece 10, and several measurement points P1, P2, P3, P4, P5, P6. It is explanatory drawing which shows a pattern matching typically. It is explanatory drawing which shows the operation | movement of template matching typically. It is a schematic diagram which shows the movement locus | trajectory 41 which is a measurement result of the moving amount | distance of the test piece 10. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a material testing machine according to the present invention.

  This material testing machine is movable along a table 16, a pair of screw rods 11, 12 that are erected on the table 16 so as to be vertically oriented, and these screw rods 11, 12. A cross head 13 and a load mechanism 30 for applying a load to the test piece 10 by moving the cross head 13 are provided.

  The cross head 13 is connected to the pair of screw rods 11 and 12 via nuts (not shown). Worm speed reducers 32 and 33 in the load mechanism 30 are connected to lower ends of the screw rods 11 and 12. The worm speed reducers 32 and 33 are connected to a servo motor 31 that is a drive source of the load mechanism 30, and the rotation of the servo motor 31 is transferred to the pair of screw rods 11 and 12 via the worm speed reducers 32 and 33. It is configured to be transmitted. As the pair of screw rods 11 and 12 rotate in synchronization with the rotation of the servo motor 31, the crosshead 13 moves up and down along these screw rods 11 and 12.

  The crosshead 13 is provided with an upper gripping tool 21 for gripping the upper end portion of the test piece 10. On the other hand, the table 16 is provided with a lower gripping tool 22 for gripping the lower end portion of the test piece 10. When performing a tensile test, the test force (tensile load) is applied to the test piece 10 by raising the cross head 13 in a state where both ends of the test piece 10 are held by the upper gripping tool 21 and the lower gripping tool 22. ).

  At this time, the test force acting on the test piece 10 is detected by the load cell 14 and input to the arithmetic control unit 23. Further, the test piece 10 is illuminated by the illumination device 17, and an image of the test piece 10 is measured by the video camera 15. The displacement amount of the distance between the test marks on the test piece 10 is calculated by the calculation control unit 23 based on the video of the test piece 10 taken by the video camera 15.

  The arithmetic control unit 23 includes a computer, a sequencer, and peripheral devices thereof, and takes in data from the load cell 14 and the video camera 15 and executes data processing. The servo motor 31 is feedback controlled by the arithmetic control unit 23. The arithmetic control unit 23 is connected to an input unit 34 for inputting data such as measurement points described later and a display unit 35 for displaying a photographed image by the video camera 15.

  FIG. 2 is a block diagram schematically showing the configuration of the arithmetic control unit 23 described above.

  The arithmetic control unit 23 includes a measurement point storage unit 25 that stores data of measurement points input by the input unit 34, and an image recording unit 26 that temporarily stores an image captured by the video camera 15 for each frame. An image comparison unit 27 that compares the images recorded in the image recording unit 26 between each frame using pattern matching, which will be described later, and a movement that measures the movement amount of the test piece 10 from the comparison result in the image comparison unit 27 An amount measurement unit 28 and a displacement amount calculation unit 29 that calculates the displacement amount of the test piece 10 based on the movement amount measured by the movement amount measurement unit 28 are provided.

  Next, an operation when the material test is executed by the material test described above will be described. When conducting a material test, first specify the measurement points. This measurement point is a point at which the displacement in the test piece 10 should be measured. When specifying this measurement point, the video camera 15 shown in FIG. 1 captures an image of the test piece 10 and displays this image on the display unit 35. Then, the operator uses the input unit 34 to designate a measurement point where the displacement is to be measured in the image of the test piece 10.

  FIG. 3 is a schematic diagram showing a relationship between an image of the test piece 10 and a plurality of measurement points P1, P2, P3, P4, P5, and P6 (when these are collectively referred to as “measurement point P”). .

  As shown in this figure, a plurality of measurement points P are designated. Thereby, when the surface of the test piece 10 is regarded as a surface, it is possible to collectively measure the movement amount of each part. The coordinate position of the measurement point P is stored in the measurement point storage unit 25 shown in FIG.

  When the specification of the measurement point P is completed, the crosshead 13 is raised by driving the servo motor 31 of the load mechanism 30 shown in FIG. At this time, the test force acting on the test piece 10 is detected by the load cell 14 and input to the arithmetic control unit 23. At this time, the test piece 10 is illuminated obliquely from above by the illumination device 17, and an image of the test piece 10 is taken by the video camera 15 in a state where fine irregularities and the like on the surface of the test piece 10 are raised. The And the pattern and the characteristic part of the test piece 10 are recognized, and the moving amount | distance of the test piece 10 which passes under the measurement point P is measured by pattern matching.

  FIG. 4 is an explanatory diagram schematically showing pattern matching.

  In the material testing machine according to the present invention, as this pattern matching, template matching for comparing an image photographed by the video camera 15 with a template is used. That is, as shown in FIG. 4, a template 50 that can be arranged within a calculation range 51 in which image processing can be executed is set out of the entire image 52 of the current frame captured by the video camera 15. . This template 50 is selected from an image one frame before the current image. Then, by moving the template 50, the position where the template 50 and the image in the calculation range 51 are most approximated is obtained, thereby measuring the movement amount of the test piece 10 from the image one frame before to the current image. To do. That is, the movement of the test piece 10 is repeated by repeating the operation of comparing the image of a certain frame with the image of the next frame using the image of a certain frame as a template with respect to the images of a plurality of frames taken over time by the video camera 15. The amount will be measured.

  FIG. 5 is an explanatory diagram schematically showing the template matching operation. Note that a large number of rectangular areas in FIG. 5 represent an image of one pixel.

  In the embodiment shown in FIG. 5A, by moving the template 50 for each pixel in the image captured by the video camera 15 and scanning within the calculation range 51, the image of the template 50 and the calculation are calculated. Similarity and dissimilarity with images in the range 51 are calculated by the image comparison unit 27 shown in FIG. 2, and the position of the template 50 that is most similar to both is recognized. Then, by repeating this operation for each frame photographed by the video camera 15, the amount of movement of the image photographed by the video camera 15 with time, that is, the amount of movement of the test piece 10 with time is measured. The measurement of the movement amount is executed by the movement amount measurement unit 28 shown in FIG.

  Note that, for the above-described calculation of similarity and dissimilarity, known methods such as SSD (Sum of Squared Difference), SAD (Sum of Absolute Difference), and NCC (Normalized Cross Correction) are used. Then, after completion of scanning with the template 50, two-dimensional correction is performed by executing a peak detection process by a cross correlation method or a least square method to obtain position information of one pixel or less.

  In this embodiment, since the template 50 is moved pixel by pixel and the image within the calculation range 51 photographed by the video camera 15 is compared with the template 50, pattern matching can be performed quickly, and the image Can be measured in a short time.

  In the embodiment shown in FIG. 5B, the template 50 is scanned within the calculation range 51 by moving the template 50 in units of 1 pixel or less in the image photographed by the video camera 15 and scanning. The image comparison unit 27 shown in FIG. 2 calculates the similarity and dissimilarity with the image in the calculation range 51, and recognizes the position of the template that is most similar to both. In this case, it is not necessary to perform two-dimensional correction after the completion of scanning as in the embodiment shown in FIG.

  In this embodiment, since the template 50 is moved in units of 1 pixel or less and the image in the calculation range 51 photographed by the video camera 15 is compared with the template 50, the time required for pattern matching becomes long. Therefore, it is possible to measure the moving amount of the image with high accuracy.

  FIG. 6 is a schematic diagram showing a movement locus 41 which is a measurement result of the movement amount of the test piece 10 measured over time in this way.

  As shown in this figure, when the movement of the test piece 10 is within the calculation range 51, the test is performed on the basis of the amount of movement between the first captured frame image and the last captured frame image. The displacement amount of the piece 10 is calculated. This displacement amount calculation is executed by a displacement amount calculation unit 29 shown in FIG. As described above, when the displacement amount is calculated based on the movement amount between the first frame image (image immediately after the start of the test) and the last frame image (current image), Therefore, it is possible to accurately measure the moving amount of the test piece without causing an error.

  If the first frame image (the image immediately after the start of the test) exceeds the calculation range of the last frame image (the current image), the above-described method is used to calculate the displacement amount of the test piece 10. It cannot be calculated. For this reason, in such a case, the movement amount for each frame may be integrated. That is, the displacement amount of the test piece 10 is calculated by integrating the movement amount in a plurality of frames of images taken with time. Thereby, even when the image immediately after starting the material test moves beyond the calculation range 51 that is the image processing range, the movement amount of the test piece 10 can be calculated.

  The measurement of the movement amount of the test piece 10 and the calculation of the displacement amount as described above are executed for each of the measurement points P1, P2, P3, P4, P5, and P6. Thereby, since the displacement amount of several points can be calculated simultaneously, it becomes possible to recognize the test piece 10 as a surface and to recognize the displacement.

  In the material testing machine according to the present invention, an arbitrary plurality of points in the image of the test piece 10 are designated as measurement points P1, P2, P3, P4, P5, and P6, and these measurement points P1, P2, P3, and P4 are designated. Since the displacement of the test piece 10 is measured by measuring the amount of movement of the test piece that passes below P5 and P6 by pattern matching, without marking a test mark or the like on the test piece 10, It becomes possible to measure the displacement accurately.

DESCRIPTION OF SYMBOLS 10 Test piece 11 Screw rod 12 Screw rod 13 Crosshead 14 Load cell 15 Video camera 17 Illuminating device 21 Upper gripper 22 Lower gripper 23 Arithmetic control unit 25 Measurement point storage unit 26 Image storage unit 27 Image comparison unit 28 Movement amount measurement unit 29 Displacement calculation section 34 Input section 35 Display section P Measurement point

Claims (8)

In a material testing machine that measures the amount of displacement of a test piece by photographing the test piece to which a test force has been added with a camera,
Measurement point designating means for designating coordinates in an image area of a test piece obtained by photographing the test piece with the camera as measurement points;
In a state where a test force is applied to the test piece, a movement amount measuring means for measuring the movement amount of the test piece passing through the measurement point by pattern matching,
Based on the movement amount of the test piece measured by the movement amount measurement means, the movement amount calculation means for calculating the displacement amount of the test piece;
A material testing machine characterized by comprising: The material testing machine according to claim 1,
The measurement point designating unit designates a plurality of coordinates in the image area as measurement points. The material testing machine according to claim 2,
The movement amount measuring means is a material testing machine that measures the movement amount of an image by template matching for comparing an image photographed by the camera with a template. The material testing machine according to claim 3,
The movement amount measuring means is a material testing machine that repeats an operation of comparing an image of a certain frame with an image of a next frame, using the image of a certain frame as a template, with respect to a plurality of frames of images taken with time by the camera. The material testing machine according to claim 4, wherein
The movement amount measuring means is a material testing machine that moves the template for each pixel and compares the image taken by the camera with the template. The material testing machine according to claim 4, wherein
The movement amount measuring means is a material testing machine that moves the template by a unit of 1 pixel or less and compares an image photographed by a camera with the template. The material testing machine according to claim 4, wherein
The displacement amount calculating means is a material testing machine that calculates the displacement amount of the test piece based on the moving amount of the image between the first frame image and the last frame image. The material testing machine according to claim 4, wherein
The displacement amount calculating means is a material testing machine that calculates a displacement amount of a test piece by integrating a moving amount in images of a plurality of frames taken over time.

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