JPH11295041A - Video type noncontact elongation/width meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noncontact elongation/width meter capable of accurately measuring both the elongation and the width of a test piece without increasing the cost. SOLUTION: Images of a plurality of marks M1 , M2 formed on the surface of a test piece S are picked up with a camera. From the images of the marks, the amount of movement of each of the marks is obtained, and the elongation of the test piece is measured. A width measuring jig 10 of simple structure has two plates 11, 12 on which marks m1 , m2 are formed. The plates 11, 12 come into contact with both sides of a parallel part of the test piece S and move in accordance with the change of width of the test piece. Images of the two mark m1 , m2 are picked up with the same camera for measuring elongation. From the images of the marks, the amount of movement of the marks is obtained and the width of the test piece is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video non-contact elongation / width meter capable of measuring the elongation and width of a test piece.

[0002]

2. Description of the Related Art A so-called video non-contact extensometer using a video camera is known as a non-contact extensometer for measuring the elongation of a test piece during a tensile test or the like.

[0003] In this video non-contact extensometer, two marks corresponding to two gauges are marked on the surface of a test piece prior to the start of a test, and these marks are used during the test by one video recorder. Each mark is recognized from a video signal obtained by photographing with a camera, the amount of movement of each mark is measured, and the elongation of the test piece between marks is calculated from the difference between the amounts of movement.

On the other hand, in a material test such as a tensile test,
The measurement of both the elongation and the width of a test piece in a single tensile test using a contact type width meter is also performed, and it is considered that the non-contact video type extensometer described above is used for measuring the elongation. Have been.

[0005]

However, the conventional contact-type width meter is heavy, so that when a thin test piece such as a plastic material is measured, the test piece may be adversely affected. Furthermore, since the contact type width gauge is a delicate device, it cannot be used for measurement in a high-temperature chamber, and the width gauge may be damaged by an impact when the test piece is broken.

On the other hand, when using a non-contact video extensometer to measure both the elongation and the width of a test specimen, it is necessary to use a contact width meter separately from the video extensometer, which increases costs. become.

Here, as one method for solving the above problem, a test piece is photographed with a camera, and the width of the test is directly measured from a change in the edge of the test piece on the photographed image. A non-contact width meter is also conceivable, but in this case, the color of the test piece, the surface pattern (background) of the test piece, lighting,
Since the edge profile is affected by the influence of the background color, focus, and the like, it is difficult to always ensure sufficient accuracy.

The present invention has been made in view of such circumstances, and a video non-contact elongation / width meter capable of accurately measuring both the elongation and the width of a test piece without increasing the cost. The purpose is to provide.

[0009]

According to the present invention, there is provided a video type non-contact elongation / width meter which takes an image of a plurality of marks attached to the surface of a test piece by a camera, and moves each mark from the image of the mark. An elongation measuring means for measuring the amount of elongation of the specimen and measuring the elongation of the specimen, and moving along with a change in the width of the specimen while making contact with both side surfaces of the parallel portion of the specimen.
Using a jig for measuring the width of the mark on each of the two plates, take an image of the two marks with the same camera as that used to measure elongation, and calculate the amount of movement of the mark from the image of the mark. And width measuring means for measuring the width of the test piece.

According to the present invention having the above-described structure, the width of the test piece is measured by photographing the mark placed on the plate in contact with the side surface of the test piece. Without receiving the mark, the mark can be accurately recognized, and sufficient accuracy for measuring the width of the test piece can be guaranteed. Moreover,
One camera can measure the elongation and width of the test piece. In addition to the non-contact video extensometer, the inexpensive jig consisting of two plates that contact both sides of the parallel part of the test piece is prepared, and the width of the test piece can be accurately measured without contact. can do.

[0011]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

On the surface of the test piece S, as shown in FIG.
Two marks M1, M2 are provided. This test piece S
In a state where both ends are gripped by grippers 21 and 22 such as a material testing machine, a tensile load is applied in a vertical direction in the figure. Each of the marks M1 and M2 has a shape in which a plurality of diamonds (squares) are arranged on a straight line perpendicular to the tensile direction, and is formed by stamp printing, for example.

A jig 10 for measuring the width is mounted on the test piece S. As shown in FIG. 3, the width measuring jig 10 includes a rectangular back plate 11 and a front plate 12 (both are aluminum plates and 1 mm thick).

On one end of the back plate 11, a plurality of rhombic (square) marks (black) m1 linearly arranged in the vertical direction (the tensile direction of the test piece S) are formed by stamp printing or the like. At the position adjacent to the mark m1, two tops 11a and 11 for contact with the test piece S are provided.
a is provided on a straight line parallel to the mark m1. On the other end side of the back plate 11, two slide bars 11b, 11b, which are members extending in the lateral direction (the width direction of the test piece S) and are parallel to each other, are provided. One end of each of the slide bars 11b is fixed to the back plate 11 via a support base 11c, and a nut 11d for locking a compression coil spring 13, which will be described later, is screwed into the other end.

The front plate 12 is a member arranged on the front side of the back plate 11, and is vertically
b and 12b are provided. Each of the support members 12b,
12b are slidably mounted on slide bars 11b, 11b of the back plate 11, respectively.
The front plate 12 can be moved in a horizontal direction (width direction of the test piece S) with respect to the back plate 11. A compression coil spring 13 for pressing the entire front plate 12 toward the side surface of the test piece S is sandwiched between the upper and lower support members 12b, 12b and the nuts 11d, 11d.

At the center of the front plate 12, a mark (black) consisting of a plurality of diamonds (squares) linearly arranged along a direction parallel to the mark m1 of the back plate 11.
m2 is formed by stamp printing or the like, and the end of the front plate 12 (the end on the test piece S side)
A top 12a for contact with the test piece S is provided. The top 12a is composed of two tops 11 of the back plate 11.
It is located at a position on a perpendicular to a straight line passing through the center position between a and 11a, that is, at the vertex of an isosceles triangle having the base between the two tops 11a and 11a.

The tops 11a and 12a provided on the back plate 11 and the front plate 12 are plastic molded products.
It is rotatable around 1e and 12e. In addition, V-grooves are formed on the outer peripheral surface of each of the tops 11a and 12a so as to correspond to test pieces S having various thicknesses.

The mark m1 on the back plate 11
Is formed on the surface of an aluminum plate 11 'having the same thickness as that of the front plate 12 and fixed to the front surface of the back plate 11 in order to match the position of the front plate 12 with the mark m2 forming surface (front surface). ing.

In the width measuring jig 10 having the above structure, the nuts 11d, 11d are placed with the test piece S placed between the two pieces 11a, 11a of the back plate 11 and the pieces 12a of the front plate 12. Screw in each top 11
a, 11a, and 12a are brought into contact with the side surface of the test piece S, and then the compression coil spring 1 is formed by the nuts 11d and 11d.
By adjusting the tightening amount of No. 3, the front plate 12 can be set on the test piece S by a procedure of pressing the front plate 12 against the test piece S with an appropriate force. Then, in such a set state, when the test is started and the width of the test piece S changes,
The marks m1, m on each of the plates 11, 12 according to the change
2 moves, and the width of the test piece S after the change from the movement amount is
It can be obtained by a method described later.

In the present embodiment, an image of the test piece S on which the two marks M1, M2 for elongation measurement and the jig 10 for width measurement are mounted is taken by the video camera 1. The photographing signal from the video camera 1 is digitized by the A / D converter 2, and then is captured by the arithmetic processing unit 3 every moment.

The arithmetic processing unit 3 is actually composed mainly of a computer and its peripheral devices and operates based on an installed program. FIG. 1 shows a block diagram for each function based on the program. I have. That is, the arithmetic processing device 3 is mainly configured by the mark position detection unit 31 and the arithmetic unit 32, and the arithmetic processing device 3 stores the measurement results of the elongation / width of the test piece S and the r value. A display device 4 for displaying is connected.

Image data digitized by the A / D converter 2 from the video camera 1 is supplied to the mark position detecting unit 31 of the arithmetic processing unit 3 every moment.

The mark position detecting section 31 recognizes each position of two marks M1 and M2 for elongation measurement and each position of two marks m1 and m2 for width measurement from the supplied image data.

As shown in FIG. 4, the recognition of the mark position is performed by setting data areas DM1, DM2 and Dm1, Dm2 for the marks M1, M2 and m1, m2 on the photographed image, respectively, and measuring the elongation. For the marks M1 and M2, the image data in the data areas DM1 and DM2 are integrated in the direction (x direction) orthogonal to the direction of extension of the test piece S, and a one-dimensional profile in the direction of extension of the test piece S is obtained. Is created, and the positions of the two marks M1, M2 attached to the test piece S are recognized from the one-dimensional profiles PM1, PM2. For the width measurement marks m1 and m2, the image data in the data areas Dm1 and Dm2 are integrated in the elongation direction (y direction) of the test piece S to obtain a one-dimensional profile in the width direction of the test piece S. Is created, and the test piece S is obtained from the one-dimensional profiles Pm1 and Pm2.
Is performed by recognizing the respective positions of the two marks m1 and m2 attached to.

Then, the mark detecting section 31 sends the position data on the marks M1, M2 and the position data on the marks m1, m2 obtained through the above processing to the calculating section 32 every moment.

The calculating section 32 uses the position data on the marks M1 and M2 from the mark detecting section 31 to calculate each of the marks M1 and M2.
The elongation of the test piece S is calculated every moment by calculating the movement amount (g1, g2) of 1, M2, and each mark m1, m2 is obtained using the position data on the marks m1, m2 from the mark detection section 31.
The width of the test piece S is calculated every moment by calculating the movement amount (w1, w2) of m2. Further, using the calculation results (elongation and width of the test piece S), an r value (Rankford value) used as a specific value related to the press formability of the thin steel sheet is obtained.

The specific methods of elongation / width calculation and r-value calculation performed by the operation unit 32 will be described below.

First, the distance between the elongation measurement marks M1 and M2 attached to the test piece S is G0, and the width W0 of the test piece S is G0.
(Value obtained by caliper).

Assuming that the moving amount of the mark M1 and the moving amount of the mark M2 when the test piece S slightly extends from the start of the test are g1 and g2, respectively.
The distance G between the two marks M1 and M2 is as follows: G = G0 + g1-g2 (1) Also, assuming that the moving amount of the mark m1 at the time when the width of the test piece S is deformed is w1 and the moving amount of the mark m2 is w2, the width W of the deformed test piece S is W = W0−w1 + w2. .. (2). In these equations (1) and (2), the movement amounts (g1, g2) of the marks M1, M2 obtained from the position data of the marks and the movement amounts of the marks m1, m2, respectively. (W1, w2
), The elongation and width of the test piece S can be obtained.

On the other hand, the r value is

[0031]

(Equation 1)

Is determined by This equation (3) is obtained by using the above equations (1) and (2).

[0033]

(Equation 2)

In this embodiment, the r value is calculated using the equation (4). Next, in the present embodiment, the reason why the marks M1, M2 for elongation measurement and the marks m1, m2 for width measurement have a shape in which a large number of diamonds are arranged in a straight line will be described below.

First, when a simple linear mark as shown in FIG. 5A is used, a profile obtained by integrating the mark in the direction in which the mark extends is shown in FIG. 5B.
And the number of data points used in the interpolation calculation when determining the edge portion of the mark is reduced.

On the other hand, when a mark having a shape in which a large number of diamonds (squares) are arranged in a straight line is used as in this embodiment (FIG. 6 (A)), the mark is moved in the direction in which the diamonds are arranged. Since the profile obtained by integration is an isosceles triangle as shown in FIG. 6B, the number of data points used for the interpolation calculation of the edge portion increases, and the edge can be recognized with high accuracy.

In this embodiment, both the marks M1, M2 for elongation measurement and the marks m1, m2 for width measurement are rhombic, but the marks M1, M2 for measurement are as follows.
Even when a normal mark such as a linear mark is employed, the accuracy in elongation measurement can be guaranteed.

FIG. 7 is an explanatory diagram of another embodiment of the present invention. In this embodiment, as shown in FIG. 7 (A), two video cameras 1
01 and 102 are arranged, and the upper mark M1 (for elongation measurement) is photographed by the video camera 101 thereon (FIG. 7).
(B)), the lower mark M2 on the lower video camera 102
And two marks m1 and m2 for width measurement (Fig. 7
(C)) is characterized in that the two marks M1 and M2 for elongation measurement are photographed by individual cameras in this way, regardless of the distance between the marks at the start of the measurement. The field of view can be set, whereby the field of view of each camera can be narrowed, and a video signal with high resolution can be obtained.

Further, since the field of view of each camera can be set regardless of the distance between marks at the start of measurement,
Even if the distance between marks is long, by installing each camera in accordance with it, it is possible to measure the elongation and width of a long test piece such as a wire rod without widening the field of view of each camera.

[0040]

As described above, according to the present invention,
Images of a plurality of marks attached to the surface of the test piece are taken by a camera, the amount of movement of each mark is obtained from the image of the mark, the elongation of the test piece is measured, and both sides of the parallel portion of the test piece are measured. Using the width measurement jigs marked on each of the two plates that move with the change in the width of the test piece, and compare the images of the two marks with those for measuring the elongation. Since the width of the test piece is measured by photographing with a camera and calculating the moving amount of the mark from the image of the mark, both the elongation and the width of the test piece can be measured in a non-contact manner. Moreover, since the width of the test piece is measured by photographing the mark on the plate that contacts the side surface of the test piece, the mark can be accurately recognized without being affected by the color, lighting, etc. of the test piece. And sufficient accuracy can be guaranteed for the width measurement of the test piece.

Further, according to the present invention, in addition to the non-contact video extensometer, an inexpensive jig consisting of two plates that are in contact with both sides of the parallel portion of the test piece only needs to be facilitated. Can be minimized. Furthermore, since the jig used for width measurement has a simple structure in which two plates are combined, measurement can be performed in a high-temperature chamber, and there is no possibility of damage due to the impact of a fracture of the test piece. Moreover, since the width of the test piece is measured from an image taken by a camera using such a width measuring jig, there is also an advantage that the width measurement is not affected by noise.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a front view of a test piece used in the embodiment.

FIG. 3 is a front view (A) and a side view (B) of a width measuring jig used in the embodiment of the present invention.

FIG. 4 is a diagram showing an image photographed and a profile of a mark together in the embodiment of the present invention.

FIG. 5 shows a linear mark and its profile.

FIG. 6 is a diagram showing marks in which rhombuses are arranged linearly and their profiles.

FIG. 7 is an explanatory diagram of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video camera 2 A / D converter 3 Arithmetic processing unit 31 Mark position detecting unit 32 Arithmetic unit 4 Display unit 10 Width measurement jig 11 Back plate 11a frame 12 Front plate 12a frame S Test piece M1, M2 mark (extension measurement) M1 and m2 marks (for width measurement)

Claims (1)

[Claims] 1. An elongation measuring means for photographing images of a plurality of marks attached to the surface of a test piece by a camera, obtaining the amount of movement of each mark from the image of the mark, and measuring the elongation of the test piece; Each of the test pieces comes into contact with both side surfaces of the parallel portion and moves with a change in the width of the test piece.
Using a jig for measuring the width of the mark on each of the two plates, take an image of the two marks with the same camera as that used to measure elongation, and calculate the amount of movement of the mark from the image of the mark. Video non-contact elongation, characterized by comprising a width measuring means for measuring the width of the test piece
Width gauge.