JP2674239B2 - Extensometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an extensometer for measuring the displacement between gauge marks of a test piece which is twisted by a load such as a twisted wire.

B. Conventional Technology Conventionally known extensometers have a pair of levers attached to a pair of gauge marks on a test piece, respectively, and a relative displacement of both levers according to the elongation of the test piece is detected by a displacement detector ( It is detected by the detection means) to obtain the displacement between the gauge marks of the test piece.

C. Problems to be Solved by the Invention By the way, when the test piece is, for example, one formed by twisting thread-like members (hereinafter referred to as a twisted wire test piece), twisting occurs in the test piece by applying a tensile load. Therefore, the pair of levers fixed to the gauge point try to rotate in opposite directions. However, since the pair of levers are connected to each other via the displacement detector, they cannot rotate.
For this reason, there is a problem in that an unreasonable force is applied to the lever due to the twist of the test piece and an accurate displacement amount cannot be detected.
Further, especially when the test piece has a large twist, the lever may be disengaged from the test piece.

A technical object of the present invention is to make it possible to accurately measure the displacement between gauge marks even if the test piece is twisted.

D. Means for Solving the Problems The extensometer according to the present invention has a pair of levers attached to a pair of gauges of a test piece, respectively, and a load shaft integrally with the pair of levers according to the twist of the test piece. Detection that detects the relative displacement between the pair of levers and the pair of rotating members, which are rotatably supported as a center and are capable of relative displacement with the pair of levers according to the elongation of the test piece. And means for solving the above technical problems.

E. Action When the test piece is twisted during loading, the pair of levers and the pair of rotating members rotate in unison with the load shaft. Therefore, no excessive force acts on the lever. The pair of levers and the rotating member are displaced relative to each other according to the elongation of the test piece, and the pair of detection means detect the relative displacements. The displacement between the gauge marks of the test piece can be obtained from these detection results.

F. Embodiment An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a front view showing the configuration of the extensometer according to the present invention. A pair of screw rods 2 are erected on the table 1, and a cross head 3 is screwed through the screw rods 2. A load rod (load shaft) 4 attached to the lower surface of the crosshead 3 and a fixed rod 5 attached to the table 1.
A pair of grips 6, 7 are respectively connected to the grips, and both ends of the above-mentioned twisted-wire test piece TP are gripped by the grips 6, 7.

To the pair of upper and lower gauge marks of the test piece TP, one ends of upper and lower levers 11 and 12 constituting the extensometer 10 are attached by clips 21 and 22, respectively. The extensometer 10 is the upper and lower levers 11,12.
, A pair of encoder mounting plates (rotating members) 13 and 14 rotatably supported by the load rod 4, and a pair of encoders 1 fixed to one ends of the encoder mounting plates 13 and 14, respectively.
With 5,16 and.

Guide tube 1 provided on the bottom surface of the encoder mounting plates 13 and 14
Guide shafts 11a and 12a, which are erected on the upper surfaces of the upper and lower levers 11 and 12, are inserted into 3a and 14a, respectively, and therefore the encoder mounting plate 13, the lever 11 and the encoder mounting plate 14 are inserted.
The lever 12 and the lever 12 can rotate together. Wires 17 and 18, one ends of which are respectively attached to the free ends of the levers 11 and 12, are wound around encoders 15 and 16 that are rotatably supported by encoder mounting plates 13 and 14, and weights 23 are attached to the other ends. ,twenty four
Is installed. Weights 25, 26 for balancing are also attached to the other ends of the encoder mounting plates 13, 14. Encoders 15 and 16 have levers 11 and 12 and encoder mounting plates 13 and 1
The number of pulse signals corresponding to the amount of movement of the wires 17 and 18 due to the relative displacement with respect to 4 is output.

FIG. 2 shows a block diagram of the control system, and encoders 15 and 1
The output pulse signal of 6 is waveform shaped by the waveform shaping circuits 31 and 32, multiplied by a predetermined frequency by the multiplying circuits 33 and 34, and then input to the counters 35 and 36. The counters 35 and 36 count the input pulse signals and input the counting result to the CPU 37. A display circuit 38 is also connected to the CPU 37, and a recording circuit 40 is connected via a D / A converter 39.

 Next, the operation of the embodiment will be described.

In conducting the test, both ends of the stranded wire test piece TP are held by the grippers 6 and 7, and then one ends of the levers 11 and 12 are attached to the pair of upper and lower gauge points of the test piece TP by the clips 21 and 22, respectively.
After that, when the pair of screw rods 2 are rotated to raise the crosshead 3, a tensile load acts on the test piece TP and the test piece TP extends. Here, since the test piece TP is in the form of a stranded wire, twisting occurs as it extends, so that the pair of upper and lower levers 11 and 12 attached to the gauge point rotate in mutually opposite directions. Guide shafts 11a and 12a of levers 11 and 12 are encoder mounting plates 13 and 14
Since it is inserted in the guide cylinders 13a, 14a of the encoder mounting plates 13, 14, the encoder mounting plates 13, 14 have levers 11, 12 centered on the load rod 4.
And rotate together. Therefore, the encoders 15 and 16 also rotate integrally with the levers 11 and 12.

On the other hand, the positions of the pair of gauges are displaced according to the elongation of the test piece TP, and the guide shafts 11a and 12a slide in the guide cylinders 13a and 14a, respectively, so that the encoder mounting plate 13, the lever 11 and the encoder mounting plate 14 and the lever 12 are displaced relative to each other according to the elongation of the test piece TP. Wires 17,1 accordingly
8 moves by an amount corresponding to the displacement, and the encoders 15 and 16 respectively output the pulse signals of the number corresponding to the moving amount.

This pulse signal is generated by the waveform shaping circuits 31, 3 as described above.
The waveform is shaped in 2 respectively, multiplied by a predetermined frequency in the multiplying circuits 33, 34 and input to the counters 35, 36.
36 counts the number of input pulse signals respectively and inputs the count results N1, N2 to the CPU 37. The CPU 37 sequentially calculates the deviation ΔN between N1 and N2 by ΔN = N1−N2. N1 and N2 are
Since it depends on the relative displacement between the levers 11 and 12 and the encoder mounting plates 13 and 14, respectively, this deviation ΔN depends on the displacement between the reference points of the test piece TP.

The CPU 37 sequentially obtains the gauge length displacement from this deviation ΔN,
The calculation result is digitally displayed on a display meter (not shown) via the display circuit 38. The obtained gauge displacement ΔN
Is converted into an analog signal by the D / A converter 39, and then output to the recording circuit 40. The recording circuit 40 records the displacement between the gauge marks in an analog manner by, for example, a recorder (not shown).

Based on the above, the lever 11,1
Since 2 rotates integrally with encoder mounting plates 13 and 14, the relative displacement between lever 11 and encoder mounting plate 13 (displacement of the upper gauge point) without applying excessive force to levers 11 and 12. The relative displacement amount between the lever 12 and the encoder mounting plate 14 (the displacement amount of the lower gauge point) can be accurately detected, respectively, and thus the gauge displacement of the test piece TP can be accurately obtained.

In the above description, the relative displacements of the levers 11 and 12 and the rotating members (encoder mounting plates) 13 and 14 are detected by the encoders 15 and 16, respectively.
Instead of 16, for example, the guide shafts 11a and 12a and the guide tube 1 described above.
A linear scale may be configured by 3a and 14a, and the relative displacement amount may be detected by this. In this case, the means for transmitting the twist of the lever to the rotating member also serves as the detecting means.

Further, as shown in FIG. 3, a differential transformer 50 may be used as the detecting means. In this case, the coils 51 may be installed above the rotating members 13 and 14, the iron cores 52 may be provided upright above the levers 11 and 12, and the iron cores 52 may be inserted into the coils 51. In this case, the holes 13b, 1 of the rotating members 13, 14 through which the iron core 52 penetrates so that the iron core does not contact the coil 52.
The diameters of 4b and the iron core 51 need to be substantially the same.

G. Effect of the Invention Since the present invention is configured as described above, when the twisted wire test piece is tested, even if the test piece is twisted, the lever and the rotating member rotate integrally, which causes an excessive force to the lever. It is possible to accurately detect the amount of displacement of the upper gauge mark and the amount of displacement of the lower gauge mark without adding a pressure, and it is possible to accurately obtain the gauge mark displacement of the test piece. Even if the test piece is heavily twisted, the lever will not come off the test piece.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention, FIG. 1 is a front view of a material testing machine showing the structure of an extensometer according to the present invention, and FIG. 2 is a display and recording of the detected elongation. FIG. 3 is a partial sectional view of an extensometer showing a modified example. 4: Load rod, 10: Extensometer 11, 12: Lever 13, 14: Encoder mounting plate 15, 16: Encoder, TP: Test piece

Claims (1)

(57) [Claims] 1. A pair of levers respectively attached to a pair of gauge points of a test piece, and a pair of levers which are integrally supported by the pair of levers in response to a twist of the test piece so as to be rotatable about a load shaft. A pair of rotating members that can be respectively displaced relative to the pair of levers according to the elongation of the test piece, and a detection unit that detects the relative displacement of the pair of rotating members and the pair of levers, respectively. An extensometer.