JP2979768B2 - Material testing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material testing machine provided with an extensometer for measuring the displacement of the upper and lower reference points of a test piece to measure the elongation of the test piece.

[0002]

2. Description of the Related Art Conventionally, there has been an extensometer for measuring the elongation of a test piece from the relative movement of the pair of levers by locking the tips of a pair of levers arranged in parallel to upper and lower marks on the test piece. Are known. In this type of extensometer, for example, the tip of a lever is locked to upper and lower marks via a mounting bracket, and a differential transformer is interposed between the rear end of one lever and the rear end of the other lever. ing. When the pair of levers is tilted according to the extension of the test piece, the iron core and the coil constituting the operation transformer move relatively, and the differential transformer outputs a signal corresponding to the extension.

[0003]

However, in this type of extensometer, a mounting bracket to a reference point, a pair of levers,
In some cases, the weight of the iron core or coil of the differential transformer acts on the test piece, and a bending load acts on the test piece, so that a test with high accuracy cannot be performed. In addition, since the mounting bracket comes into edge contact with the mark, the test piece may be damaged and may be broken from that portion, and a highly accurate test may not be performed. Further, when the test piece is thinned by the tensile test, the upper and lower levers may be displaced from the respective reference points.

An object of the present invention is to reduce the weight of an extensometer acting on a test piece, not to damage the test piece, and to provide a material test provided with an extensometer which is hardly displaced from a reference point even when the test piece becomes thin. To provide machines.

[0005]

In the material testing machine according to the present invention, a pair of coil springs are wound around upper and lower reference points of a test piece, and a predetermined tension is applied to the coil springs by a connecting member. The end portion is connected to the fixed side, and has an extensometer for detecting a physical quantity correlated with the amount of inclination between the reference point side and the fixed side of the pair of coil springs with a detector.

[0006]

When the test piece is extended, the coil spring wound and locked around each of the upper and lower reference points inclines with the other end on the fixed side as a fulcrum.
This amount of inclination is proportional to the elongation of the test piece. The amount of movement of each of the upper and lower reference points is measured by directly or indirectly detecting the inclination with a detector. The elongation of the test piece can be measured from the difference between the movement amounts of these upper and lower gauge points.

[0007]

An embodiment will be described with reference to FIGS. FIG.
In the figure, reference numeral 1 denotes an upper gripper suspended from a movable crosshead (not shown), 2 denotes a lower gripper installed on a fixed table 3, and a test piece 4 has upper and lower ends of upper and lower grippers 1, 2.
Is gripped. A pair of brackets 5 and 6 are erected from the table 3 on the left and right sides of the test piece 4, and a pair of differential transformers 51 and 6 are provided on each of the brackets 5 and 6.
1 and 52 and 62 are provided above and below. The differential transformers 51 and 52 detect the displacement of the upper gauge 7, and the differential transformers 61 and 62 detect the displacement of the lower gauge 8.

Coil springs 9 and 10 are wound around the upper and lower reference points 7 and 8, respectively, and the right ends of the coil springs 9 and 10 are attached to upper and lower mounting hooks of the right bracket 5 via intermediate joints 11 and 12, respectively. The left ends of the coil springs 9 and 10 are connected to upper and lower mounting hooks 17 and 18 of the left bracket 6 via intermediate joints 13 and 14, respectively. At this time, a predetermined tension is applied to the coil springs 9 and 10, and the coil springs 9 and 10 are securely locked to the upper and lower reference points of the test piece 4.

Core hooks 11f to 14f are provided at intermediate positions of the intermediate joints 11 to 14, respectively. The core hooks 11f to 14f are provided with iron cores 51c, 61c and 52c, 52c of the differential transformers 51, 61 and 52, 62, respectively.
2c is suspended, and the respective iron cores are inserted into the coil portions of the differential transformers 51, 61 and 52, 62. FIG.
In the above, GL indicates the distance between the upper and lower reference points.

In FIG. 2, reference numeral 71 denotes a differential transformer 51.
And 72, an amplifier for adding the outputs of the differential transformers 61 and 62, 73
The subtractor 73 calculates the difference between the output of the amplifier 71 and the output of the amplifier 72. The subtractor 73 outputs a signal indicating the expansion between the reference points.

The operation of the extensometer thus constructed will be described. Upper gripping tool 1 by moving cross head (not shown)
Rises, a tensile load acts on the test piece 4 and the test piece 4
Grows. At this time, assuming that the extension of the upper gauge 7 is δ1 and the extension of the lower gauge is δ2, the intermediate joints 11 and 1 connected to the upper gauge 7 via the coil spring 9 as shown in FIG.
2 tilts by θ1. Further, the intermediate joints 13 and 14 connected to the lower gage 8 via the coil spring 10 have θ2 (<
tilt by θ1). Here, the elongation δ1,
δ2 is proportional to the inclinations θ1 and θ2. In FIG. 2, GL ₀ indicates the distance between the upper and lower gauges before the test, and GL ₁ indicates the distance between the gauges when the test piece is extended.

Due to such inclination of the intermediate joints 11, 13, the iron core 51c (52c) connected to the upper intermediate joints 11, 13 rises according to the inclination θ1, and the coil portion of the differential transformer 51 (52) And relative movement. Further, the iron core 61c (62c) connected to the lower intermediate joints 12, 14 also rises according to the inclination θ1, and relatively moves with the coil portion of the differential transformer 61 (62). Therefore, each of the differential transformers 51, 52, 61, and 62 outputs a signal corresponding to each of the inclinations θ1 and θ2 of the intermediate joints 11 to 14, that is, a signal corresponding to the elongation δ1 and δ2 of the test piece 4.

The amplifier 71 includes upper differential transformers 51 and 52.
And the amplifier 72 is connected to the lower differential transformer 61,
62 outputs are added. Output Sa of both amplifiers 71 and 72
And Sb are input to a subtractor 73, where Sa−Sb (δ1−δ)
2) is calculated and the elongation of the test piece 4 is output.

According to the embodiment configured as described above, since the coil portions of the differential transformers 51, 52, 61, and 62 are set on the brackets 5 and 6, the weight of the coil portions acts on the test piece 4. Absent. The test piece 4 has a coil spring 9,
Although the weights of the core 10, the intermediate joints 11 to 14 and the iron core work, at least the coil springs 9, 10 and the intermediate joints 11 to 14 can be made lighter than conventional levers, so that the influence on the test piece 4 can be reduced. Furthermore, the coil springs 9, 10 and the intermediate joints 11 to 1
Since the load applied to the test piece 4 by the test piece 4 acts uniformly on the left and right sides of the test piece, the occurrence of a bending load accompanying the attachment of the extensometer is prevented. Due to the above factors, according to the present embodiment, the elongation can be measured with higher accuracy than the conventional lever extensometer.
In addition, since the coil spring is wound around the reference point with a predetermined tension, the test piece is not damaged, and the coil does not deviate from the reference point even if the test piece becomes thin during the tensile test.

In the above, the case where the differential transformer is used has been described. However, a magnetic linear encoder or a potentiometer may be used. Also, the elongation is measured by converting the inclination of the intermediate joint into a linear movement amount of the iron core, but an angle sensor that directly detects the inclination of the intermediate joint is used, or the inclination of the intermediate joint is used as a rotation amount by a rotary encoder. In addition to the detection, the inclination amount of the coil spring can be detected in various forms. Therefore, various modes of connection between the coil spring and various sensors can be adopted depending on the type of sensor.

[0016]

As described above in detail, according to the present invention, the load of the extensometer acting on the test piece can be reduced, the test piece can be mounted without damaging the test piece, and even if the test piece becomes thinner. The extensometer does not shift from the upper and lower gauges. for that reason,
High-precision elongation can be measured.

[Brief description of the drawings]

FIG. 1 is a main part front view showing an example of a material testing machine according to the present invention.

FIG. 2 is a block diagram showing a circuit for processing an output signal of a differential transformer.

FIG. 3 is a diagram showing the inclination of a coil spring;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper gripping tool 2 Lower gripping tool 3 Fixed table 4 Test piece 5, 6 Bracket 7, 8 Marking point 9, 10 Coil spring 11-14 Intermediate joint 15-18 Mounting hook 51, 52, 61, 62 Differential transformer 51c, 52c, 61c, 62c Iron core 71, 72 Amplifier 73 Subtractor

Claims (1)

(57) [Claims] A pair of coil springs respectively wound around upper and lower reference points of a test piece; a connecting member for connecting an end of each spring to a fixed side while applying a predetermined tension to the coil spring; A material testing machine comprising: a detector that outputs a signal that correlates to an amount of inclination between the gauge side and the fixed side of a pair of coil springs.