KR100742546B1 - Method of and apparatus for measuring elongation of a test specimen - Google Patents

Abstract

A non-contact elongation measuring method and apparatus capable of obtaining accurate measurement values and automating without attaching a reference line, the method comprising: irradiating a laser beam of two sensor units including a laser projector and a CCD camera to a reference base line at two positions on a specimen; Photographing the laser reflected light in a speckle pattern including a plurality of fringes with a CCD camera, wherein the fringes at predetermined positions of the speckle pattern correspond to the indicated reference line positions at each of two positions on the CCD camera screen coordinates. Recognizing as a target, Determining the height information of the test piece by detecting the amount of pixel movement in the coordinates of the moving target fringe, such as the height of the test piece, Fringe of the speckle pattern photographed by the CCD camera It includes a phase change to a marker in position. The application of the tensile load on the test piece may be stopped by detecting the stoppage and scattering of the speckle pattern on the CCD camera immediately before breaking of the test piece.

Elongation measuring device, tensile strength tester, image processing part, test piece, laser light emitter, CCD camera, speckle pattern, sensor part

Description

Test piece elongation measuring method and apparatus {METHOD OF AND APPARATUS FOR MEASURING ELONGATION OF A TEST SPECIMEN}

1 is a schematic configuration diagram of a first height measuring apparatus according to a preferred embodiment of the present invention.

2 is a schematic structural diagram of a second elongation measuring apparatus according to another preferred embodiment of the present invention.

3 is a schematic configuration diagram of a third elongation measuring apparatus according to a more preferred embodiment of the present invention.

4 is a schematic configuration diagram of a modified height measuring apparatus according to a more preferred embodiment of the present invention.

5 is a schematic configuration diagram of a conventional height measuring apparatus for photographing a reference point with a television camera.

6 is an operation explanatory diagram of an image conversion apparatus.

Explanation of symbols on the main parts of the drawings

1. Tensile Stress Tester 2. Test Piece

13. Operation unit 18. Pulse motor

21. Image processor 23. Pulse motor controller

The present invention relates to a method and apparatus for measuring elongation of a specimen in a non-contact manner in which no baseline (or reference point) is attached to the test specimen, and in particular, a speckle pattern that appears in the reflected light of the laser beam irradiated onto the specimen. The present invention relates to a method and apparatus for measuring height using a fringe shift amount in a pattern).

A method used for measuring a test piece extension in a non-contact manner, comprising: attaching a baseline at two points in the direction of extension of a test piece, photographing each reference line with two television cameras, and recognizing each mark on a television screen with a computer. Calculating the amount of movement of the markers on the television screen moving along the elongation, controlling the position of the two television cameras so that each marker is always in a predetermined position appearing on the television screen, and before applying the tensile load to the specimen There is a method comprising the step of measuring the elongation rate based on the distance difference between two television cameras after fracture of the test piece.

In addition, the non-contact method of measuring the extension of the test piece without a baseline, irradiating a laser beam having a predetermined length increase in the direction of applying a tensile load to the surface of the test piece, the test piece as an electrical signal according to various clarity in the speckle pattern Non-contact elongation measurement comprising recognizing the reflected light in the zone according to the reference points of the two positions of and calculating the elongation of the test piece based on the relevant function of the electrical signal of the speckle pattern using the output of the image sensor Various methods and apparatus have been proposed and disclosed in, for example, Japanese Patent Application Laid-Open No. 59-52963, Japanese Patent Application Laid-Open No. 61-27681, Japanese Patent Application Laid-Open No. 7-4928.

However, the former method, i.e., using a television camera, includes a fatal flaw that requires the baseline to be attached to the specimen. That is, the method of attaching a reference line includes a method of marking on a test piece, a method of attaching a seal, a method of marking with ink, and a method of fixing the test piece with a binder at a reference position. However, the measurement method of attaching the baseline adversely affects the strength of the test piece, the peeling of the seal, the extension of the baseline makes the reference itself unclear, and the ink of the baseline also causes chemical changes in the test piece, so that the accuracy of the test and Prevent efficiency.

On the other hand, the latter method, that is, the conventional method of measuring the elongation using the speckle pattern, converting the reflected light obtained by irradiating a portion of the test piece with a laser beam and measuring it with an image sensor or the like to obtain an electrical signal matching the speckle pattern Determining the amount of movement of the speckle pattern based on the correlation function of the signal before and after the test piece extension. That is, since the speckle pattern recognized by the image sensor is converted into an electrical signal and used, it is difficult to obtain high measurement accuracy unless a precise optical component and a modulation element are used.

Furthermore, in the conventional stretching measurement using the speckle pattern, the step of storing the speckle pattern in the stretching direction of the test piece before deformation (whole dot pattern) as an electrical signal, and the correlation of the speckle pattern during deformation related to the electrical signal The step of determining the function continuously determines the amount of movement of the speckle pattern. Therefore, if the specimen and the laser beam are placed relatively laterally during the measurement, the speckle pattern as the reference itself becomes inaccurate, causing a problem of losing reliability in all measured values. In particular, if a tensile load is given to the specimen during the measurement and a fine lateral error cannot be avoided, this problem becomes severe during the measurement.

In addition, as a general problem of the conventional elongation measurement, since the elongation point is broken based on the distance between the reference lines and the final distance between the reference lines at the time of rupture of the test piece before the tensile load is applied, until the tear occurs in the test piece Tensile load is applied. However, depending on the material, the specimen may break into pieces when it is ruptured, which poses a risk, which may interfere with work efficiency, since the operator should avoid the specimen in a safe place after installing it in the elongation measuring device.

Accordingly, the first object of the present invention is to obtain accurate measurement values without setting a reference point to the test piece, without using a precise optical device or a modulation element, and to allow the lateral movement of the test piece to be neglected and to be automated. In addition to the non-contact elongation measuring method, an elongation measuring apparatus that achieves the above-described method is provided.

A second object of the present invention is to provide an elongation measuring apparatus which achieves the above-described method, as well as the above-mentioned elongation measuring method which utilizes an image processing apparatus and computes and controls by using a conventional television camera as it is.

A third object of the present invention is to measure the state immediately before breaking of the test piece, and to measure the elongation that achieves the above-described method, as well as the elongation measuring method for determining the elongation measurement value which is substantially equivalent to the breaking time without breaking the test piece. Provide the device.

The first object of the present invention is achieved by a non-contact first elongation measuring method while applying a tensile load to a test piece, and in two sensor sections having a laser projector and a CCD camera integrally set at two positions along the elongation direction on each test piece. Irradiating the laser to the indicated reference position, photographing the laser reflected light with each CCD camera in a speckle pattern constituting each of the plurality of fringes, and the fringe at the speckle pattern predetermined position on the CCD camera screen coordinates. Recognizing as a target according to each prescribed reference position at a position, detecting a shift amount in pixels on a target fringe coordinate within each speckle pattern moving in accordance with the elongation of the test piece, and the target fringe always at a predetermined position on the screen. The two sensor sections along the direction of extension of the test piece Performing tracking control, and determining the height information of the test piece in consideration of the distance between the two sensor units, each movement detection amount, or each pixel moving amount of the target fringe.

According to the first method of the present invention, the laser beam is irradiated to two reference position reference line positions along the extension direction of the test piece set in the tensile stress tester, and the speckle pattern is photographed with each of the plurality of fringes with a CCD camera. And a pair of sensor units having a laser projector and a CCD camera, detecting a movement amount of the target fringe moving in accordance with the extension of the test piece on the pixel unit of the photographed image, and controlling the pair of sensor drivers by the detection signal. The target fringe is positioned at a predetermined position of the cloak pattern, and includes a pair of sensor driving units which move the pair of sensor units along each guide and move the sensor unit along a guide that matches the supportable input signal. Control unit for recognizing a fringe at a predetermined position of the photographed speckle pattern as a target fringe according to the instruction reference line position And an arithmetic unit for determining the specimen extension information based on the distance between the two sensor units, the respective movement detection signal amount, or the pixel unit movement amount of the target fringe. have.

The second object of the present invention can also be achieved by a non-contact second tensile measurement method during the application of the tensile load on the test piece. Irradiating the indicated reference line positions of the two positions set according to each other, including photographing the laser reflected light with a speckle pattern composed of a plurality of fringes with each CCD camera, and placing the fringe at a predetermined position of the speckle pattern. Recognizing the target as a target according to each indicated reference line position of the position, converting the image into a marker at predetermined positions of two television camera screens, respectively, and pixels of the marker of the television screen moving in line with the specimen extension Detecting the unit movement amount, the marker always being positioned at a predetermined position on the television screen Controlling the movements of the two sensor units along the direction of extension of the test piece with the detection signal at every movement, and the distance between the two sensor parts, the amount of movement detection signal of each mark or the unit of pixel movement of the mark of the television. Determining the height information.

According to a second method of the present invention, a laser beam is irradiated to two reference positions according to an extension direction of a test piece set in a tensile stress tester, and a speckle pattern composed of a plurality of fringes of laser reflected light is photographed by a CCD camera. And a pair of sensor units having a laser projector and a CCD camera, and a pair of image conversion devices are disposed along the sensor unit, and the target fringe photographed by the CCD camera of the sensor unit is photographed at a predetermined position on the television camera screen. And a pair of sensor actuators moving and supporting a pair of sensor units along each guide and moving the sensor units along the guides in accordance with an input signal, and the pixels of the television screen such that the mark is at a predetermined position on the television screen. Detects the amount of movement of the marker moving in accordance with the elongation of the specimen on the unit. A control unit for controlling the pair of sensor driving units and recognizing the marks photographed by the television cameras 25 and 26 as reference lines corresponding to the indicated reference line positions, the distance between the two sensor units, the amount of each marker moving detection signal or the television. A second elongation measuring device for a test piece is achieved, comprising a calculating section for determining the elongation information of the test piece by the pixel-based movement amount of the mark.

A third object of the present invention is achieved by the third method carried out in the first or second measurement method, which detects a stop or phase distortion on a speckle pattern that appears immediately before the break of the application of the test piece. The applied tension should be stopped.

The third method of the present invention is achieved with a third apparatus implemented in the first or second apparatus, and detects the image stop and the image scattering, which are represented by the speckle pattern of the CCD camera, immediately before the test specimen is broken. It further includes a load control device for outputting a tensile load stop signal.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The present invention measures the elongation of the test piece (2) set in the tensile stress tester (1), the tensile stress tester (1) is to protect the end of the test piece (2) with chucks (3 and 4), A tensile load pulling one or both of the chucks (3 and 4) is applied to the specimen (2).

1 is a schematic diagram of a preferred embodiment of an elongation measuring device used to achieve the method according to the invention. The measuring device 5 comprises a pair of sensor parts 8 and 9 having an integrated laser projector 6a or 6b and a CCD camera 7a or 7b, respectively, and the sensor parts 8 and 9 in the tensile direction of the test piece 2. ) A pair of sensor drivers which move each of them vertically, a controller 12 which outputs a drive signal to the sensor drivers 10 and 11 based on the information of the sensors 8 and 9 and the test piece 2 based on various data. An arithmetic unit 13 that calculates decompression information such as an elongation rate and an elongation amount is included, and the control unit 12 and the arithmetic unit 13 are integrated into a central processing unit 14 (hereinafter referred to as a computer).

The sensor sections 8 and 9 are supported by guide rods 15 and 16 of the corresponding sensor driving sections 10 and 11, respectively, wherein the sensor section 8 is adapted to direct the laser beam of the laser projector 6a. It irradiates to one indication reference line position (A) of a test piece, and laser-reflected light is image | photographed with the speckle pattern containing a some fringe with CCD camera 7a. In the same way, the sensor unit 9 irradiates the laser beam of the laser projector 6b to another prescribed reference line position B of the test piece, and photographs the laser reflected light in a speckle pattern with the CCD camera 7b.

The sensor driving units 10 and 11 are provided with a pair of drive rods, for example, a pair of guide rods 15 and 16 for supporting the sensor units 8 and 9 and corresponding pulse motors 17 and 18. And the sensor sections 8 and 9 are moved vertically along the guide rods 15 and 16 by the signal of the control section 12 to be described later. In the illustrated embodiment, the guide rods 15 and 16 are composed of feed screw rods that rotate with the pulse motors 17 and 18 so that the rotation of the guide rods 15 and 16 causes the sensor unit 8 to be rotated. And 9) to move vertically.

The control unit 12 stores a predetermined fringe in the speckle pattern photographed by the CCD cameras 7a and 7b in the sensor units 8 and 9 as a target fringe at a predetermined position on the coordinate system based on the pixels on the screen. When the target fringe moves on the screen, respectively, the control unit 12 detects the quantity in units of pixels and sends the detected value to the respective pulse motors 17 and 18 of the sensor driving units 10 and 11 as pulse signals. Tracking control of 9) is performed so that each target fringe is at a predetermined position on the screen.

For this purpose, the control unit 12 is input from the central processing unit 19 performing the task of the measuring device, the input and output unit 20 for inputting and outputting the state information of the tension tester 1, the sensor unit 8 and 9 Indicative baseline position (A) of wound portions 11 and 22 and test piece 2 performing binarization to A / D convert the video signal of the speckle pattern and exclude intermediate tones that create a more distinct speckle pattern And B) storing the fringe with the appropriate area from the speckle pattern as the target fringe corresponding to the target fringe, detecting the target fringe shift amount moving along the extension of the test piece 2 such as the coordinate shift amount corresponding to the pixel of the video screen, and detecting the detected signal. Pulse motor control units 23 and 24 which are sent to the pulse motors 17 and 18 of the sensor drive units 10 and 11 are provided.

The calculating section 13 calculates the elongation and elongation of the test piece based on various criteria between the start of the application of the tensile load and the break of the test piece (2). For example, the elongation δ of the test piece 2 is determined according to the following equation:

Where L ₀ represents the distance between the sensor parts 8 and 9 before the start of application of the tensile load, and L represents the distance between the sensor parts 8 and 9 when the test piece 2 is broken.

Further, the operating unit 13 calculates the elongation rate (or elongation amount) based on the movement amount of the target fringe in view of the relationship between the movement amount of each target fringe and the movement amount of the sensor units 8 and 9, or the sensor units 8 and 9 The elongation rate (or elongation amount) based on the pulse signal is calculated in view of the relationship between the pulse signal and the movement amount.

Therefore, the apparatus shown in FIG. 1 recognizes the indicated reference line position at two positions of the test piece 2 as the target fringe at a predetermined position in the speckle pattern, and moves the target fringe on the coordinates in the video screen of the speckle pattern. As a result, the movement of the instruction reference line positions A and B, which move along the extension of the test piece 2, is determined, the amount of pixel-by-pixel movement of the video screen is detected, and the position tracking control of the sensor units 8 and 9 is detected by the detection signal. Each target fringe at a predetermined position in the above-described screen, and the relationship between the distance or movement amount between the sensor portions 8 and 9, the pulse signal amount or the number of pixels to which the target fringe moves before the start of tensioning and the break of the test piece. Measure your height with.

Fig. 2 shows a second elongation measuring method used to achieve the present method, as well as a second elongation measuring method for achieving the second object of the present invention. Prior to describing this embodiment, conventional measuring means are described in which a reference point mark attached to a test piece by a television camera is photographed.

5 illustrates an embodiment. In this apparatus, the reference point markers A 'and B' are added to two specific positions of the test piece 2, and the reference point markers A 'and B' at both positions are two television cameras 25 and 26. The film is photographed separately, and the scarring for calculating the pixel unit shift amount of the marking is performed by the scarring portions 21 'and 22' of the control portion 12 'for the marks in each camera screen during the tensile test. And the amount of movement calculated by the pulse motor control units 23 'and 24' corresponding to the pulse motors 17 'and 18' of the camera drivers 10 'and 11' of the television cameras 25 and 26. And reference point markers A 'and B' are positioned at each center of the television screen to measure the elongation of the test piece 2 based on the distance between the television cameras. do.

Elongation measuring devices using television cameras contain the disadvantages described before, because the reference point markings (A and B) must be attached to the specimen (2).

The present invention shown in FIG. 2 is used in a second stretch measuring method and method by applying the present invention described above with reference to FIG. 1 to a measuring apparatus on a television camera system without the attachment of reference point marks A 'and B'. Control unit 12 ', wound portions 21' and 22 ', pulse motor control units 23' and 24 ', which are used as conventional measuring means of a television camera system, The apparatus 14, etc., and the calculating part 13 'are utilized as it is.

That is, the height measuring method converts the speckle pattern photographed by the CCD cameras 7a and 7b of the sensor units 8 and 9 of the apparatus shown in FIG. 1 into markers at predetermined positions of the two respective television screens. The amount of movement of the mark on each television screen in pixel units moving in accordance with the elongation of the test piece 2 is detected, and the pulse motors 17 and 18 of the sensor drive units 10 and 11 are controlled by the detection pulse signal, and the sensor unit The tracking control of (8 and 9) is carried out so that the mark is always located at the predetermined position of each television screen, and the movement amount and distance of the two sensor units (8 and 9), the movement detection signal amount of the mark, or the pixel unit movement amount of the mark. The elongation of the test piece 2 is measured based on it.

For this purpose, the apparatus shown in Fig. 2 is characterized in that the outputs of the CCD cameras 7a and 7b of the sensor sections 8 and 9 are wound 21 'and of the control section 12' for operating a program designed for a television screen. Pulse motors of the pulse motor controllers 23 'and 24', which are designed for television screens, connected to the image converting apparatuses 27 and 28, 17 and 18). However, the image converting apparatuses 27 and 28, which are sent to the television camera screen via the image converting apparatus with the reference marks shown in Fig. 6, display the speckle pattern on the photographing screen of the CCD camera.

Thus, by applying the apparatus shown in Fig. 2, the speckle pattern used at the indicated reference line position photographed by the CCD cameras 7a and 7b of the sensor units 8 and 9 is phase-shifted to the marks in the two television screens, and the sensor The sections 8 and 9 are positioned along the elongation of the test piece 2 using conventional programs for television screens.

However, the inventors have found through many experiments that the speckle pattern of the test piece (2) subjected to the tensile load is once stopped and the pattern is scattered just before the fracture of the test piece. The new idea came to be that measurements can be made to obtain substantially equivalent stretch measurements. That is, the elongation measuring method has the characteristic of detecting the stoppage and scattering of the speckle pattern just before the breaking of the test piece (2) and stopping the tensile load in the tensile stress tester (1).

3 and 4 show a schematic configuration of the apparatus used in the measuring method, and the apparatus shown in FIG. 3 differs from the apparatus shown in FIG. 1 by adding a load control unit 29 to the speckle pattern just before breaking. Except for detecting the stop and distortion and stopping the tensile load in the tensile stress tester (1) has the same configuration, the device shown in Figure 4 and the device shown in Figure 2 in addition to the load control unit 29 It has the same configuration except that In the illustrated embodiment, the load control unit 29 is coupled to the central computing device 14.

The inventors have found through many experiments that the speckle pattern of the test piece (2) subjected to tensile load is once stopped and the pattern is scattered just before the fracture of the test piece. When the phenomenon is found, the tensile load is stopped and the elongation value is immediately measured. The new idea came to the idea that measurements can yield substantially equivalent elongation measurements. That is, the elongation measuring method has the characteristic of detecting the stoppage and scattering of the speckle pattern just before the breaking of the test piece (2) and stopping the tensile load in the tensile stress tester (1).

Claims (6)

In the method of measuring elongation in a non-contact manner while applying a tensile load to the test piece (2), Indication reference line position in which the laser beams from the two sensor sections 8 and 9 having the laser projector 6a or 6b and the CCD camera 7a or 7b respectively are located at two positions set in accordance with the stretching direction of the test piece 2. Irradiating (A and B) respectively; Photographing the laser reflected light as each speckle pattern including a plurality of fringes with the CCD camera (7a or 7b); Recognizing the fringe at a predetermined position of the speckle pattern as a target corresponding to the respective reference reference line positions (A and B) at two positions on the CCD camera screen coordinates; Detecting a pixel-by-pixel shift amount of the coordinates of the target fringe in each speckle pattern moving in accordance with the extension of the test piece; Performing tracking control of the two sensor units (8 and 9) along the extension direction of the test piece (2) with a detection signal every movement so that the target fringe is always at a predetermined position of the screen; And Determining the elongation information for the test piece (2) in consideration of the distance between the two sensor parts (8 and 9), the amount of each movement detection signal or the amount of pixel movement of each target fringe. Non-contact stretch measurement method. In the method of measuring elongation in a non-contact manner while applying a tensile load to the test piece (2), Indication reference line positions A of two positions in which the laser beams of the two sensor sections 8 and 9 each having a laser projector 6a or 6b and a CCD camera 7a or 7b are respectively set along the stretching direction of the test piece 2. And B), respectively; Photographing the laser reflected light as each speckle pattern including a plurality of fringes with the CCD camera (7a or 7b); Recognizing a fringe at a predetermined position of the speckle pattern as a target corresponding to the indicated reference line positions (A and B) at each of the two positions; Image converting each of the target fringes into markers at predetermined positions of two television camera screens; Detecting the amount of pixel movement of the mark of the television screen moving in accordance with the elongation of the test piece (2); Controlling the movement of the two sensor parts (8 and 9) along the stretching direction of the test piece (2) with the detection signal every movement so that the mark is always at the predetermined position of the television screen; And Determining the extension information of the test piece 2 in consideration of the distance between the two sensor units 8 and 9, the amount of each marker movement detection signal or the amount of pixel movement of each television image marker. Non-contact type elongation measurement method. The method according to claim 1 or 2, Non-contact type elongation measuring method characterized in that the tension load on the test piece is stopped by detecting a stop or distortion of the speckle pattern image appearing immediately before the rupture of the test piece. In the test piece elongation measuring device, The laser beams are irradiated to the reference reference lines A and B at two positions in the extending direction of the test piece 2, which are integral with the laser projector 6a or 6b and the CCD camera 7a or 7b, respectively. And a pair of sensor units 8 and 9 which respectively photograph laser reflected light with each speckle pattern including a plurality of fringes with the CCD camera 7a or 7b; A pair of sensor driving units (10 and 11) movably supporting the pair of sensor units (8 and 9) along each guide and moving the sensor units (8 and 9) along the guide in accordance with an input signal; The fringes at predetermined positions of the speckle pattern photographed by the CCD cameras 7a and 7b of the sensor units 8 and 9 are respectively recognized as target fringes corresponding to the instruction reference lines A and B, and And detecting the target fringe movement amount moving in accordance with the extension of the test piece in pixel units of the photographed image, and detecting the target fringes at the predetermined positions of the speckle pattern, respectively, by the detection signals 10 and 11. A control unit 12 for controlling a); And And an arithmetic unit 13 for determining the extension information for the test piece 2 in consideration of the distance between the two sensor units 8 and 9, the respective movement detection signal amount or the pixel unit movement amount of the target fringe. Test piece elongation apparatus. In the test piece elongation measuring device, The laser beams are irradiated to the reference reference lines A and B at two positions in the extending direction of the test piece 2, which are integral with the laser projector 6a or 6b and the CCD camera 7a or 7b, respectively. A pair of sensor units 8 and 9 which respectively photograph laser reflected light with respective speckle patterns including a plurality of fringes with the CCD cameras 7a and 7b; A pair of sensor driving units (10 and 11) movably supporting the pair of sensor units (8 and 9) along each guide and moving the sensor units (8 and 9) along the guide in accordance with an input signal; The target fringes photographed by the CCD cameras 7a and 7b of the sensor units 8 and 9 are respectively photographed with markers at predetermined positions on the television camera screen, and correspondingly with the sensor units 8 and 9 respectively. A pair of image conversion apparatuses 27 and 28 arranged; The amount of marker movement which the markers photographed by the television cameras 25 and 26 are respectively recognized as reference lines corresponding to the indicated reference line positions A and B, respectively, and move in accordance with the test piece elongation on a pixel-by-pixel basis of the television screen. A control unit (12) for detecting the control unit and controlling the pair of sensor driving units (10 and 11) with a detection signal so that the mark is at the predetermined position of the television screen; And And an arithmetic unit 13 for determining the extension information for the test piece 2 in consideration of the distance between the two sensor units 8 and 9, the amount of each marker movement detection signal or the amount of pixel movement of the television image marker. Specimen elongation measuring device, characterized in that. The method according to claim 4 or 5, And a load control device (29) for detecting stops and distortions on the speckle pattern of the CCD camera immediately before breaking the specimen and outputting a tensile load stop signal for the specimen. .

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