JP3071925B2 - Non-contact type elongation measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type elongation measuring method for measuring elongation in a tensile test of a material strength test without contacting a test piece.

[0002]

2. Description of the Related Art In a material strength test such as a tensile test and a creep test, it is often necessary to measure the elongation of a test piece. In this case, two reference points on the test piece are measured by an extensometer. The elongation of the test piece is measured by measuring the change in length between them. A typical extensometer using a strain gauge or a differential transformer as a detector is typical.

[0003]

However, in the strain gauge type extensometer, since the gauge intervals are determined for each detector, a detector is prepared for each required gauge interval. However, there is a disadvantage that it cannot cope with a large length change exceeding the gauge length due to its structure. Also, in the differential transformer type extensometer, it is usually necessary to prepare a detector for each gauge interval.

On the other hand, although a differential transformer type extensometer that solves this problem has been developed, its usability cannot be said to be good. Further, as a drawback of both the strain gauge type and the differential transformer type extensometer, it is necessary to attach or contact the detector with the test piece, so that the setting is troublesome, and the test piece may be a thin plate or a thin wire. In this case, there is a major drawback that the detector is difficult to attach.

[0005] In addition, several types of extensometers have been devised, but most of them have a type in which a detector is brought into contact with a test piece, and are different from strain gauge type or differential transformer type extensometers. It is hard to say that the mounting workability is excellent. On the other hand, there is an optical extensometer as an extensometer with improved mounting workability. The optical extensometer detects a reference point marked on a test piece by an optical system, and detects the amount of elongation of the test piece by tracking its movement.

Although this method is excellent in that it does not contact the test piece, it has sufficient accuracy when writing or attaching a mark to the test piece or when measuring minute elongation. There are many unsatisfactory parts such as no. In this regard, the present invention has been made in view of the above-mentioned conventional problems, and in addition to improving the measurement workability, the test method of the present invention has been used even under test conditions where measurement cannot be performed or sufficient measurement cannot be obtained by the conventional method. It is intended to provide a non-contact type elongation measuring method capable of measuring the amount of elongation.

[0007]

The above object can be attained by adopting the following novel characteristic construction method of the present invention. That is, the first feature of the present invention is that in a tensile test in a material strength test, at least two non-contact type feed amount detectors capable of measuring a moving amount of an object in a non-contact manner using a laser beam. Provided, the feed amount of each of the non-contact feed amount detectors determined on the surface of the test piece before tension is detected until the post-tension of the reference point, and the elongation amount of the test piece is obtained from the difference in the feed amount. This is a non-contact type elongation measuring method.

[0008] A second feature of the present invention is that in a tensile test in a material strength test, at least two stages that can move in parallel in the elongation direction of a test piece are installed, and a laser beam is used for the stage. A non-contact type feed amount detector capable of measuring the amount of movement of an object in a non-contact manner is mounted, and a tension is applied to a reference point for each of the non-contact type feed amount detectors set on the surface of the test piece before tension. The feed amount is detected, and the detected signal is fed back to the control unit of the stage, and the stage is moved so that the feed amount detection value of the reference point by the non-contact type feed amount detector becomes zero. A non-contact type elongation measuring method in which the amount of elongation of the test piece is obtained from the difference in the amount of movement of the stage.

A third feature of the present invention is that the difference in the amount of movement of the stage in the second feature is determined by comparing the control amount of the stage control unit or by measuring the fluctuation of the stage relative distance by a suitable means. This is a contact elongation measurement method.

[0010]

According to the present invention, the above measures are taken, so that the reference point on the surface of the test piece before tension is determined for each of the two or more non-contact feed amount detectors, The amount of movement of the test piece is detected, and the elongation of the test piece is determined from the difference.

Alternatively, for each of the non-contact feed amount detectors mounted on two or more stages that can move in parallel in the direction of extension of the test piece, a reference point on the surface of the test piece before tension is determined, The movement amount of each point during the tension is measured, and a measured value signal of the movement amount is fed back to the control unit of the stage, and the respective stages are followed so that the movement amount measured value of the gauge point becomes zero. The test piece is moved in parallel, and the elongation amount of the test piece is obtained from the difference in the movement amount of the stage.

[0012]

【Example】

(First Embodiment) A first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a front view of an elongation measuring device used in the elongation measuring method of the present embodiment.

In the figure, α is an elongation measuring device, β is a test piece,
1, 2 are the upper and lower grips of the test piece β, 3a,
3b is a non-contact type feed amount detector using a laser beam;
D is the end of the test piece, B and C are the marks, 4 is the frame, 5 is the parallel guide rod, 6 is the slider, and 7 is the non-contact type feed amount detector 3a, 3b standing upright in parallel with the parallel guide rod 5. It is a mounting column.

In the elongation measuring device α, the specification procedure of this embodiment is as follows. When the lower grip 2 is fixed and the upper grip 1 is pulled upward together with the slider 6, the gap between the reference points B and C is set. In measuring the amount of elongation, the measurement is performed according to a specific embodiment described below. When the upper grip 1 is pulled upward at the speed v, if the test piece β extends uniformly, the movement amount of each point from 0 to t ₁ second is as follows.

[0015]

(Equation 1)

Accordingly, if the amount of elongation between the reference points B and C from 0 to t ₁ seconds is ΔL ₁ , the following equation is obtained.

(Equation 2)

Next, non-contact type feed amount detectors 3a and 3b, which are previously mounted with the initial positions of the reference points B and C as specific points, respectively.
At the reference points B, after the upper grip 1 is not pulled upward,
Each feed amount of C is measured, and an elongation value is estimated from a difference between the measured values. When the upper gripper 1 is pulled up at the speed of v, the moving speeds after t seconds observed by the non-contact type feed amount detectors 3a and 3b are represented by the following formulas as vB and vC, respectively.

[0018]

(Equation 3)

That is, the reference points B and C measured by the non-contact feed amount detectors 3a and 3b from 0 to t1 seconds.
When the feed amounts of X and X are respectively X _B1 and X _C1 , the following expression is obtained.

(Equation 4)

Therefore, the difference Δx1 in the feed amount from 0 to t1 seconds is expressed by the following equation.

(Equation 5)

In the equation (1), the numerator vt1 is represented by the denominator L +
When it is sufficiently smaller than 2a, the following terms in {} can be ignored, and the following equation is obtained.

(Equation 6)

That is, when the test piece β extends uniformly and the amount of elongation is small, the amount of elongation can be measured by the measuring method according to the present embodiment. When the proof stress is obtained in an actual material strength test, the test piece β is considered to be uniformly deformed, and the amount of elongation is extremely small. Therefore, the elongation measuring method according to this embodiment is effective.

However, in equation (1), the numerator v
If t1 is not sufficiently small compared to the denominator L + 2a, the second and subsequent terms in {} cannot be ignored, and accurate elongation measurement cannot be performed in this embodiment. To solve this, the present inventor has created an elongation amount measuring method shown in the following second embodiment.

(Second Embodiment) A second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 is a front view of an elongation measuring device used in the elongation measuring method according to the present embodiment. In the figure, α ′ is an elongation measuring device, 3a ′ and 3b ′ are non-contact type feed amount measuring unit detectors, and 8a and 8b are independently movable in parallel with the test piece β tension direction and each of the non-contact type feed amounts Measuring device detector 3
This is a stage on which a 'and 3b' are mounted.

Reference numeral 9 denotes a stage control unit, 10 denotes a main body of a feed amount measuring instrument, 11 denotes a computer, and 12 and 13 denote mounting columns on which the stages 8a and 8b are mounted in parallel with the parallel guide rod 5 so as to be vertically slidable. , 14 are horizontal support rods whose base ends are cantilevered to the stage 8a and non-contact type feed meter side detectors 3a 'are fixed to the ends. The same members as those in the first embodiment are denoted by the same reference numerals.

In the elongation measuring apparatus α ', the specification procedure of this embodiment is executed according to a specific embodiment described below. Thus, the non-contact feed amount measuring device detector 3
a 'and 3b' are set so as to detect the feed amounts of two different measurement points B and C on the test piece β, and the measurement value signals from the non-contact type feed amount measuring unit detectors 3a 'and 3b' are used. Is processed by the feed amount detector main body 10 and input to the computer 11.

The computer 11 outputs a drive signal to the stage controller 9 so that the measured value signal detected by the non-contact type feed amount measuring device detectors 3a 'and 3b' becomes 0, 8b is moved. In such a system, when the test piece β is pulled, the two reference points B and C for detecting the feed amount by the non-contact feed amount measuring device detectors 3a 'and 3b' move, respectively. The stages 8a and 8b on which the non-contact feed amount measuring device detectors 3a 'and 3b' are mounted also move following the reference points B and C, respectively.

Since the stages 8 a and 8 b are controlled by the stage controller 9, the amount of movement can be detected as a control amount of the stage controller 9. Therefore, the amount of movement of the stages 8a and 8b is
The computer 11 issues an operation command as a control amount to the two reference points B and C on the test piece β from the difference in the commanded control amount.
The amount of elongation between them can be compared and calculated.

(Third Embodiment) A third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 is a front view of an elongation measuring device used in the elongation measuring method according to the present embodiment. In the figure, α ″ is an elongation measuring device, 15 is a laser displacement meter, and 14 ′ and 16 are horizontal supports. The same members as those in the second embodiment shown in FIG.

In the elongation measuring device α ″, the specification procedure of the present embodiment is the same as that of the specific embodiment described below, and in the second embodiment, the non-contact type feed amount measuring device detector 3a ′ is used. , 3
A horizontal support whose base end is cantilevered to the stage 8b is obtained by reversely calculating the movement amount of the stages 8a and 8b on which the b 'is mounted, that is, the distance between the two reference points B and C from the control amount of the stage control unit 9. The measurement is directly performed by the laser displacement meter 15 installed on the tip of the rod 16.

Since the precision of feed of the normal stages 8a and 8b is not so good, in the elongation measuring and measuring apparatus α ″, the distance between the stages 8a and 8b The accuracy is improved by irradiating the laser to the penetrating projecting end 14a and measuring.
Needless to say, the distance between the stages 8a and 8b can be measured by a measuring technique such as an electronic micrometer in addition to the laser displacement meter 15 shown in FIG.

In the embodiment of the present invention, non-contact type feed amount measuring devices 3a, 3b, 3a 'and 3b' are used for measurement, but the non-contact type feed amount measuring devices 3a, 3b and 3 are used.
Tests a 'and 3b' are used for the feeding and monitoring or control of products / materials in the production line, whereas in the embodiment of the present invention, they are deformed simultaneously with the movement. That the target points B and C on the piece β are to be measured;
Also, the fact that the difference of the measured values is used as a set of two or more units is fundamentally different in terms of usage. Also, in the conventional optical extensometer, the feed amount measuring device for measuring the feed amount was a non-contact type, but the feed amount is measured without any marking on the surface of the test piece β. In this respect, the present invention is different from the conventional optical extensometer.

[0033]

As described above, according to the present invention, since the movement distance between the reference points on the test piece is measured following by using the non-contact type feed amount measuring device, it is a difficult point of the conventional optical extensometer. It is completely free from the trouble of marking and the restriction on the shape of the test piece, and the measurement accuracy is improved. Further, in the first embodiment, a mechanism for tracking a reference point is not required, so that the mechanism is greatly simplified.

Further, if the non-contact extensometer according to the method of the present invention is used for a material strength test such as a creep test, it is possible to measure the elongation amount with good workability and high accuracy on a wide range of test pieces. is there. Further, the present invention provides excellent effects such that a great effect can be expected when used not only for elongation measurement in a tensile or creep test but also for displacement measurement in a bending test or the like.

[Brief description of the drawings]

FIG. 1 is a front view of an elongation measuring device provided for an elongation measuring method according to a first embodiment of the present invention.

FIG. 2 is a front view of an elongation measuring device used in the elongation measuring method according to the second embodiment.

FIG. 3 is a front view of an elongation measuring device used in the elongation measuring method according to the third embodiment.

[Explanation of symbols]

 α, α ', α "... elongation measuring device β ... test piece A, D ... test piece end B, C ... mark 1 ... upper gripping tool 2 ... lower gripping tool 3a, 3b, 3a', 3b '... non- Contact type feed amount detector 4 ... Frame 5 ... Parallel guide rod 6 ... Slider 7,12,13 ... Mounting column 8a, 8b ... Stage 9 ... Stage control unit 10 ... Feed amount measuring unit 11 ... Computers 14,14 ' 16 Horizontal support 15 Laser displacement meter

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B 21/00-21/32 G01B 11/00-11/30

Claims (3)

(57) [Claims] (1) In a tensile test in a material strength test,
At least two non-contact type feed amount detectors that can measure the amount of movement of an object in a non-contact manner using laser light are provided on the test piece.
Laser light instead of writing or attaching gauge marks
Utilizing the feed amount detector for each test piece surface before pulling
A non-contact type elongation measuring method, comprising determining a reference point, detecting a feed amount of the reference point after tension, and obtaining an elongation amount of the test piece from a difference in the feed amount. (2) In a tensile test in a material strength test,
At least two stages that can move in parallel in the direction of extension of the test piece are installed, and a non-contact type feed amount detector that can measure the amount of movement of the object in a non-contact manner using laser light is mounted on the stage. , Write a mark on the test piece
Using laser light instead of mounting
A reference point is defined on the surface of the test piece before tension for each amount detector, the feed amount of the reference point during tension is detected, and the detected signal is fed back to the control unit of the stage, and the non-contact type Non-contact type elongation characterized by moving the stage so that the feed amount detection value of the reference point by the feed amount detector becomes zero, and obtaining the amount of elongation of the test piece from the difference in the amount of movement of the stage. Measurement method 3. The non-contact type elongation measurement according to claim 2, wherein the difference in the amount of movement of the stage is obtained by a control amount comparison operation of a stage control unit or by measurement of fluctuation of an appropriate means of the stage relative distance. Method