JPH026347Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field This invention detects the true load acting on the test piece during material testing in a vacuum chamber or pressure chamber and calculates the load on the test piece. This invention relates to a load correction device for correctly controlling the load.

(b) Prior art Generally, as shown in FIG. 1, a test piece W is housed in a chamber 1 isolated from the outside air,
When performing a test with the internal pressure different from the external pressure, let Sa be the cross-sectional area of rods 2 and 2' that penetrate chamber 1, and let Sb be the cross-sectional area of test piece W, respectively.
If the pressure difference between the internal pressure of the chamber 1 and the external pressure is P, then the upper and lower rods 2 and 2' have the same size and opposite directions, Fp=P×(Sa−Sb)...( 1) A force acts. Since these opposite forces cancel each other out, they are balanced as a whole and are not detected by the load cell 3. However, test piece W
A tensile or compressive load Fp will be applied to both ends of the . As a result, the load value F _L detected by the load cell 3 includes an error Fp with respect to the load F _T actually acting on the test piece W as F _L =F _T +Fp (2). Therefore, for example, when a predetermined set load is applied to the test piece W with the inside of the chamber 1 in a vacuum state, according to the conventional testing machine, the load value detected by the load cell 3 is on the tensile side.
An error Fp occurred, and the detected value was fed back to the loading mechanism as it was, so the test piece W
A load that deviates from the set load by Fp toward the compression side is applied. That is, for example, when the load target value is set to 0 and the detected value of the load cell 3 is fed back, the piston 4 is driven and controlled so that the detected value of the load cell 3 becomes 0, but in this state, the test piece actually This means that a load Fp is acting on W. Therefore, in the past, tests were carried out by shifting the preset load by that amount or ignoring the error, which caused various problems such as the reliability of the test results and the operability of the test equipment.

(C) Purpose The present invention was developed in view of the above, and it is possible to measure and provide feedback on the true load acting on a test piece during material testing in a chamber as described above. The load correction device of the material testing machine is capable of always applying a load exactly equal to the set load to the test piece even if there are pressure fluctuations in the chamber, without shifting the set load in advance. intended to provide.

(D) Structure The feature of the present invention is that a pressure sensor is provided to detect the pressure inside the chamber, and the above-mentioned force Fp is calculated from the output of the pressure sensor, and that value is subtracted from the output of the load detector. The present invention is configured so that the true load acting on the test piece is detected, and the loading mechanism is controlled based on the detected true load value.

(E) Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

Test piece W in chamber 1 isolated from outside air
via a rod 2 that passes through the chamber 1 and is connected to the load cell 3, and a rod 2' that also passes through the chamber 1 and is connected to the actuator 5.
The load is applied by actuator 5. The actuator 5 is driven by a servo valve 6 that adjusts the flow rate of hydraulic oil from a hydraulic source (not shown).
The operation signal for the servo valve 6 is sent to the control unit 7.
Supplied from. The control unit 7 is configured to obtain the above-mentioned operation signal by introducing the load detection value from the load cell 3 via the load amplifier 8 and feeding back the load detection value to a preset target load value. .

The chamber 1 is provided with a pressure sensor 9 that detects the pressure inside the chamber 1, and its output is amplified by a pressure amplifier 10 and then fed back to the output of a load amplifier 8 via a switch 11. . The detected value of the pressure inside the chamber 1 by the pressure sensor 9 and the pressure amplifier 10 is set in advance to satisfy the above-mentioned equation (1).
By measuring the cross-sectional area Sa of 2' and the cross-sectional area Sb of the test piece W in advance, and setting the amplification factor of the pressure amplifier 10 based on the difference (Sa - Sb),
It is calibrated so that when the pressure inside the chamber 1 becomes P, the output of the pressure amplifier 10 becomes Fp.

Therefore, when performing a test with the pressure inside the chamber 1 different from the outside pressure, the detected load value fed back to the control unit 7 by closing the switch 11 will be the difference from the apparent load detected value F _L by the load cell 3. The load value obtained by subtracting the detected load value Fp due to pressure, that is, from equation (2),
This is the true load value F _T acting on the test piece W.

The load compensation device of the present invention as described above can be used for material testing in vacuum, high pressure, and various atmospheres.
You can leave 1 open. Further, even when load control is not performed using a load, the load detection data becomes the true load value by closing the switch 11.

(F) Effect As explained above, according to the present invention, the detected load value that is fed back becomes the true load value acting on the specimen, so that the set load is always applied to the specimen. , the reliability of test results is improved. Further, unlike the conventional method, there is no need to shift the set load in advance, and the tester automatically follows fluctuations in chamber pressure, improving the operability of the testing machine. Furthermore, it is now possible to test even test pieces that buckle due to the compressive load applied when the set load is 0, due to the detected load caused by the pressure difference with the outside air pressure when testing in a conventional vacuum state. Summer.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the effect related to the detected load during a test in a chamber, and FIG. 2 is a configuration diagram of an embodiment of the present invention. 1... Chamber, 2, 2'... Chamber penetrating rod, 3... Load cell, 5... Actuator, 6... Servo valve, 7... Control unit, 9... Pressure sensor, 10... Pressure amplifier, 1
1...Switch.

Claims (1)

[Scope of utility model registration request] A chamber that accommodates a test piece, a loading mechanism that applies a load to the test piece via a penetrating member that penetrates outward from the chamber, a load detector that detects the load acting on the test piece, and a load detector that detects the load acting on the test piece. A correction device for a test machine equipped with a feedback control system that obtains an operation signal for the load mechanism based on a detected load value, which includes a pressure sensor that detects the pressure inside the chamber, and an output of the pressure sensor that is set in advance. a calculation means for converting the cross-sectional area of the penetrating member and the test piece into a load acting on the test piece due to the difference between the pressure inside the chamber and the outside air pressure; A load correction device for a material testing machine, characterized by having a loop for feeding back.