JPH05196459A - Non contact type elongation measuring method - Google Patents

Abstract

PURPOSE:To eliminate troublesome gauge marking and unavailability of measurement due to special shapes by follow-up measuring the moving distance of specific point of a specimen with an aid of a non contact type feed rate measuring device when elongation measurement is performed in the tensile test of material strength test. CONSTITUTION:In the tensile test of material strength test, at least two noncontact type feed rate detectors 3a and 3b that are of noncontact type and can measure various objects with different feed rates are installed. The detectors 3a and 3b are set respectively as to coincide with the gauge marks B and C indicated on the surface of a specimen beta in advance before it is elongated, and then the moving amounts are detected respectively after the specimen betais elongated. The difference of moving amount is calculated to find out the elongation amount of the specimen beta.

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 performing elongation measurement in a tensile test of a material strength test in a non-contact manner with 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, an extensometer is used to measure two reference points on the test piece. The change in length between them is measured to measure the elongation of the test piece. As a conventional extensometer, a strain gauge or a differential transformer is typically used as a detector.

[0003]

However, in the strain gauge type extensometer, since the gauge interval is determined for each detector, a detector is prepared for each required gauge interval. However, it has a drawback that it must be dealt with, and because of its structure, it cannot cope with a large length change exceeding the gauge length. 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, it cannot be said to be easy to use. Further, as a drawback of both the strain gauge type and the differential transformer type extensometer, it is necessary to attach the detector to the test piece or to bring it into contact with the test piece, which makes setting difficult, and the test piece may be a thin plate or a thin wire. If so, there is a big drawback that the detector is difficult to mount.

Other types of extensometers have been devised, but most of them are of a type in which a detector is brought into contact with a test piece, which is more than the strain gauge type or differential transformer type extensometer. 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 the extension amount of the test piece by capturing the reference point marked on the test piece with an optical system and tracking the movement.

This method is excellent in that it does not come into contact with the test piece, but sufficient accuracy is obtained when it is necessary to write or attach a reference point to the test piece, or when minute elongation is measured. There are many dissatisfactions such as none. Here, in view of the above-mentioned conventional problems, the present invention improves the measurement workability, and even under the test conditions that cannot be measured by the conventional method or sufficient measurement cannot be obtained, It is intended to provide a non-contact type elongation measuring method capable of measuring the amount of elongation.

[0007]

The above-mentioned problems can be solved by adopting the novel characteristic construction methods enumerated below by 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 the amount of movement of an object in a non-contact manner are provided, and the pre-tension test is performed. A non-contact type elongation measurement that detects the amount of movement of each of the reference points for each of the non-contact type feed amount detectors set on one surface until after tension, and obtains the amount of elongation of the test piece from the difference in the amount of movement. Is the way.

A second feature of the present invention is that, in a tensile test in a material strength test, at least two stages that are movable in parallel in the direction of elongation of the test piece are installed, and the stage is equipped with a non-contact type Along with each non-contact type feed amount detector that can measure the amount of movement, each measuring the amount of movement during tension of the gauge for each of the non-contact type feed amount detectors set on the surface of the test piece before pulling, The movement amount measurement value signal is fed back to the control unit of the stage, and the stage is moved so that the movement amount measurement value of the gauge point by the non-contact type feed amount detector becomes zero, and the movement of the stage. It is a non-contact type elongation measuring method in which the amount of elongation of the test piece is obtained from the difference in amount.

A third feature of the present invention is that the difference in the amount of movement of the stage in the second feature is based on the control amount comparison calculation of the stage controller or the variation measurement of the appropriate means of the relative stage distance. It is a contact type elongation measuring method.

[0010]

The present invention has taken the above-mentioned means. Therefore, for each of two or more non-contact type feed amount detectors, a gauge point on the surface of the test piece before tension is determined, and after the gauge point is tensioned. The amount of movement of each test piece is detected, and the amount of elongation of the test piece is determined from the difference.

Alternatively, for each non-contact type feed amount detector mounted on two or more stages which can move in parallel in the elongation direction of the test piece, a reference point on the surface of the test piece before pulling is determined and the reference point is set. The movement amount of each point during tension is measured, and the measured value signal of the movement amount is fed back to the control unit of the stage, and the respective stages are tracked so that the movement amount measurement value of the gauge point becomes zero. By moving in parallel, the elongation amount of the test piece is obtained from the difference in the moving 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 this 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 laser light, A,
D is the end of the test piece, B and C are reference points, 4 is a frame, 5 is a parallel guide rod, 6 is a slider, and 7 is a non-contact type feed amount detector 3a, 3b which stands upright on the parallel guide rod 5. It is a mounting post.

In the elongation measuring apparatus 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 distance between the reference points B and C is increased. In measuring the amount of elongation, it is carried out according to the specific embodiment described below. When the upper grip 1 is pulled upward at the speed v, and the test piece β is uniformly stretched, the movement amount of each point from 0 to t ₁ seconds is as follows.

[0015]

[Equation 1]

Therefore, when 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, in the non-contact type feed amount detectors 3a and 3b, which are mounted in advance with the initial positions of the gauge marks B and C as specific points, the gauge marks B and C after the upper grip 1 is pulled upward. Each movement amount of C is measured, and the elongation value based on the difference between the measured values is estimated. When the upper grip 1 is pulled up at a speed of v, the moving speeds after t seconds observed by the non-contact type feed amount detectors 3a and 3b are v _B and v _C , respectively, and the following formula is obtained.

[0018]

[Equation 3]

That is, the reference points B and C measured by the non-contact type feed amount detectors 3a and 3b from 0 to t ₁ seconds.
Let x _B1 and x _C1 be the amounts of movement of, respectively.

[Equation 4]

Therefore, the difference Δx _{1 in} the moving amount from 0 to t ₁ seconds is expressed by the following equation.

[Equation 5]

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

[Equation 6]

That is, when the test piece β is uniformly elongated and the elongation amount is small, the elongation amount can be measured by the measuring method according to this embodiment. When obtaining the proof stress in the 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 the present embodiment is effective.

However, in the equation (1), the denominator v
If t ₁ cannot be said to be sufficiently smaller than the molecule L + 2a, the second and subsequent terms in {} cannot be ignored, and accurate elongation measurement cannot be performed in this embodiment. As a solution to this, the present inventor has created an elongation 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 of this embodiment. In the figure, α'is an elongation measuring device, 3a 'and 3b' are non-contact type feed amount measuring device detection units, 8a and 8b are independently movable in parallel with the test piece β pulling direction, and the non-contact type feed amount respectively. Measuring instrument detector 3
This is a stage on which a'and 3b 'are mounted.

Reference numeral 9 is a stage controller, 10 is a feed amount measuring device main body, 11 is a computer, and 12 and 13 are mounting columns in which the stages 8a and 8b are mounted parallel to the parallel guide rod 5 so as to be vertically slidable. , 14 are horizontal supports whose base ends are cantilevered to the stage 8a and whose non-contact type feed meter side detector 3a 'is fixed to the front ends. The same members as those in the first embodiment are designated by the same reference numerals.

In the elongation measuring apparatus α ', the specification procedure of this embodiment is executed according to the concrete embodiment described below. Then, the non-contact type feed amount measuring device detector 3
a 'and 3b' are set so as to detect the feed amounts of two different reference points B and C on the test piece β, and the measurement value signals from the non-contact type feed amount measuring device detectors 3a 'and 3b'. 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 signals detected by the non-contact type feed amount measuring device detectors 3a ', 3b' become 0, and the stages 8a, Move 8b. In such a system, when the test piece β is pulled, the two gauges B and C for detecting the feed amount by the non-contact type feed amount measuring device detectors 3a ′ and 3b ′ respectively move, The stages 8a and 8b, on which the non-contact type feed amount measuring device detectors 3a 'and 3b' are mounted, also move following the reference points B and C, respectively.

Since the stages 8a and 8b are controlled by the stage controller 9, the movement amount can be detected as the control amount of the stage controller 9. Therefore, the movement amount of the stages 8a and 8b is controlled by the stage controller 9
The computer 11 which gives an operation command as a control amount to the two reference points B and C on the test piece β from the difference between the commanded control amounts.
It is possible to compare and calculate the amount of elongation between.

(Third Embodiment) The 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 of this 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 apparatus α ″, the specification procedure of this embodiment is the same as the concrete embodiment described below, but in the second embodiment, the non-contact type feed amount measuring device detecting portion 3a ′ is used. , 3
The amount of movement of the stages 8a and 8b equipped with b ', that is, the distance between the two control points B and C is calculated back from the control amount of the stage control unit 9 is a horizontal support whose cantilever is projected at the base end. It is directly measured by the laser displacement meter 15 installed on the tip of the rod 16.

Since the feed accuracy of the ordinary stages 8a and 8b is not so good, in the elongation measuring and measuring apparatus α ", the horizontal support rod 14 'which relatively moves the distance between the stages 8a and 8b by the laser displacement gauge 15 is used. The accuracy is improved by irradiating the penetrating projecting end 14a with a laser for measurement,
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, the non-contact type feed amount measuring devices 3a, 3b, 3a ', 3b' are used for the measurement, but the non-contact type feed amount measuring devices 3a, 3b, 3 are used.
In the embodiment of the present invention, a'and 3b 'are used for feeding or monitoring / controlling the amount of product / material to be fed, but in the embodiment of the present invention, a test for deformation at the same time as movement is performed. The target points B and C on the piece β are to be measured,
In addition, it is fundamentally different in terms of usage that two or more units are used as a set and the difference in measured values is used. Also, even 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 moving distance between the gauge marks on the test piece is measured by using the non-contact type feed amount measuring device, it is a drawback of the conventional optical extensometer. The measurement accuracy is improved while being completely freed from the troublesome marking and the shape restriction of the test piece. Furthermore, in the first embodiment, the tracking mechanism for the reference points is not required, so the mechanism is greatly simplified.

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 can be attached to a wide variety of test pieces, and the workability can be measured with high accuracy. is there. Further, not only the elongation measurement in the tensile or creep test but also the displacement measurement in the bending test or the like can be expected to have a great effect, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a front view of an elongation measuring device used in 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 of the second embodiment.

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

[Explanation of symbols]

 α, α ′, α ″ ... Elongation measuring device β ... Specimen A, D ... Specimen end B, C ... Mark 1 ... Upper grip 2 ... Lower grip 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 device main body 11 ... Computer 14, 14 ', 16 ... Horizontal support 15 ... Laser displacement meter

Claims (3)

[Claims] 1. In a tensile test in a material strength test,
Provide at least two non-contact type feed amount detectors that can measure the amount of movement of an object in a non-contact manner, up to after pulling the gauge for each non-contact type feed amount detector defined on the surface of the test piece before pulling. A non-contact type elongation measuring method, characterized in that the amount of movement is detected and the amount of elongation of the test piece is obtained from the difference in the amount of movement. 2. In the tensile test in the material strength test,
At least two stages that can move in parallel in the direction of extension of the test piece are installed, and non-contact type feed amount detectors that can measure the amount of movement of the object without contact are mounted on the stage, and the surface of the test piece before pulling. The non-contact type feed amount detection is performed by measuring the amount of movement of each of the non-contact type feed amount detectors during pulling of the control point, and feeding back the movement amount measurement value signal to the control unit of the stage. Non-contact type elongation measuring method characterized by moving the stage so that the measured value of the amount of movement of the gauge point by the vessel becomes zero, and obtaining the amount of elongation of the test piece from the difference in the amount of movement of the stage. 3. The non-contact type elongation measurement according to claim 2, wherein the difference in the amount of movement of the stage is determined by a control amount comparison calculation of a stage control unit or a variation measurement of an appropriate means of the relative stage distance. Method