JPS63167236A - Static tension testing instrument - Google Patents

Abstract

PURPOSE:To obtain stress and elongation at many points regardless of the material of a test-piece by drawing the test-piece following up a strain quantity so that a stress increasing speed is held constant at a raised part. CONSTITUTION:The stress increasing speed of the raised part and the strain increasing speed of a part which changes from a linear part to a horizontal part are roughly known in advance from the material of the test-piece 2, so they are stored in a memory 7. Then, hydraulic pressure is supplied to a servo valve 14 to drive an actuator 13 and a chuck 11 is drawn up to draw the test- piece 2. In this drawing, the outputs of an elongation quantity detector 4 and a load cell 12 are inputted to an arithmetic circuit 74 through amplifiers 5 and 6 and A/D converters 71 and 72 and the strain increasing speed is made to follow so as to equal the value in a memory 75. Then when the strain increasing speed becomes larger than the previously supplied value, the speed is fixed at the value and the drawing is finished.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a static tensile testing device, and more specifically, to a static tensile testing device that detects the relationship between strain and stress at multiple points in the initial stage of tensile testing of a test piece. related to tensile test equipment.

[Conventional technology]

Conventionally, when a test piece is stretched in a static tensile testing apparatus, the JIS standard stipulates that the test specimen be pulled at a slow speed until the upper yield point or proof stress is reached, and then at a faster speed thereafter. In other words, in a static tensile test, the stress against strain changes significantly in the region I at the beginning of tension, as shown in Figure 3(a), and this region changes the Young's modulus value. This is an important area to be determined, and therefore requires a lot of manual input, so it is pulled at a slow speed.

[Problem that the invention seeks to solve]

By the way, in the method described above, if the speed is suddenly changed from slow to fast, a shock is given to the test piece, which adversely affects the properties of the test piece. You can change it manually or
There were troubles such as connecting a dedicated switching circuit.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention makes it possible to obtain elongation data at multiple points regardless of the material of the test scissors, and also eliminates the troublesome task of switching from slow speed to fast speed as in the past. It does not require any work or circuitry,
The method is to apply a tensile force to the test piece using an actuator on the stress-strain curve of the test piece, and simultaneously monitor the stress increase rate and strain field acceleration in real time at the rising part, and then The strain amount is increased by keeping the stress increase rate constant so that it becomes a pre-given target stress increase rate value, and at the same time increases the pre-given target strain increase rate value when the strain field acceleration occurs. This is done using a static tensile testing device that allows the test to reach breakage at a constant rate of increase in the target amount.

[For production]

The above-mentioned static tensile test device tracks the amount of strain while maintaining a constant stress increase rate in the rising section, so it is possible to obtain data from multiple points on the straight line section where it is most needed. It is.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

1 is a known tensile tester, and a test piece 2 is attached to the chuck 11.
is attached, and a load cell 1 is attached to one chuck 11.
2 is fixed. The other chuck 11 is attached to an actuator 13, and a servo valve 14 that supplies or discharges hydraulic pressure to the actuator 13
is installed.

3 is an amplifier that sends a control signal to the servo valve 14; 4 is an elongation amount detector attached to the test piece 2; 5;
is an amplifier that amplifies the output signal from the elongation amount detector 4;
6 is an amplifier for amplifying the output signal from the load cell 12.

7 is an arithmetic unit, and A/D converters 71 and 72 convert the analog signals from the amplifiers 5 and 6 into digital signals.
, a D/A converter 73 that converts a digital signal from an arithmetic circuit 74 to an analog signal, which will be described later, and an arithmetic circuit 74 and a memory circuit 75 that perform the arithmetic operations shown in the flowchart of FIG.

Reference numeral 8 denotes an adder for adding the signal from the D/A converter 73 of the arithmetic unit 7 and the signal from the amplifier 5, and its output is input to the amplifier 3.

Next, to explain the operation based on the above-mentioned configuration, in the present invention, as shown in FIG. 3(a) and FIG. 3(b), which is an enlarged view of this figure, The rising portion is defined as the area marked ■, the horizontal portion is defined as the area marked ■, and the portion after the fall is defined as the area marked ■.

Since the rate of increase in stress in the rising part in the region (■) is approximately known in advance depending on the material of test piece 2, the strain field acceleration in the part transitioning from the straight line part to the horizontal part in the region is the same, assuming this point as 01. (Test piece 2
This point is roughly known in advance depending on the material, so this point is 02 and this σ. and ε. becomes the target speed. ) In this way, after storing two values in the memory 75 in advance, a tensile test is performed. That is, by supplying hydraulic pressure to the servo valve 14 and driving the actuator 13, the chuck 11 is
and pull up the test piece 2. During this tensioning, as shown in the flowchart of FIG. 2, in the part (■) of FIG. At the same time, the output from the load cell 12 is amplified by the amplifier 6 and converted into a digital signal by the A/D converter 72, which is a parameter given in advance. Compared to this, it becomes the measurement of the part marked ■ in Fig. 3d, and this is always another parameter given in advance, ε. If it becomes larger than the value of , it means that the part ``■'' in Figure 3 d is reached, so ε. Fix it to end the area of tension ■.

In this manner, the present invention enables stress measurements at multiple points on a rising straight portion regardless of the material.

〔Effect of the invention〕

As described above, the present invention applies a tensile force to the test piece using an actuator in the stress-strain curve of the test piece, and simultaneously monitors the stress increase rate and strain increase rate from time to time in the rising portion in real time. The strain amount is increased while keeping the stress increase rate constant from the starting end of the straight line portion to a pre-given target stress increase rate value, and at the same time the strain increase rate is increased to a pre-given target strain increase rate value. In the case of a static test, it is possible to obtain stress and elongation data at multiple points regardless of the material of the test piece because the target strain increase rate is constant until the fracture occurs. can be obtained accurately, and does not require complicated work or circuits for switching from a slow speed to a fast speed as in the conventional method.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, with FIG. 1 being a block diagram, FIG. 2 being a flowchart, and FIG. 3 being a characteristic diagram. 1...Tensile tester, 2...Test piece, 3, 5, 6...
・Amplifier, 4... Extension amount detector, 7... Arithmetic device,
75...Memory.

Claims (1)

[Claims] In the stress-strain curve of the test piece, a tensile force is applied to the test piece by an actuator, and the stress increase rate and strain increase rate are monitored simultaneously in real time in the rising part, and the stress increase rate is calculated from the starting point of the straight part. is kept constant to a pre-given target stress increase rate value and the amount of strain is increased, and at the same time the pre-given target strain increase rate value is set to the target strain increase rate when the strain increase rate occurs. A static tensile test device characterized by being designed to cause breakage at a constant rate.