JP2000314691A - Control method in material testing device and material testing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subject control method capable of holding the vertical stress applied to the shearing surface of a material test piece vertically to an almost constant state and a material testing device. SOLUTION: In a control method in a material testing device, a material test piece 1 is housed in a chamber 2, and the pressure in the chamber is made higher than atmospheric pressure and compression load is applied to the material test piece by a compression actuator 9. The compression load F applied to the material test piece 1 is increased by the compression actuator 9 and the pressure in the chamber 2 is lowered as an increase in this compression load and the vertical stress σn applied to the shearing surface (b) of the material piece 1 vertically is made kept almost constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and a material test apparatus in a material test apparatus for testing a material test piece such as a rock having a shear surface.

[0002]

2. Description of the Related Art Conventionally, in a material testing apparatus for applying a three-dimensional stress to a material test piece, the material test piece is housed in a chamber, the pressure in the chamber is increased, and the material test piece is pressed by a compression actuator. are doing. During this pressing, the pressure in the chamber is controlled to be substantially constant.

[0003]

By the way, in the ground,
With the vertical stress applied to the shear plane of the rock plate being substantially constant, the shear force applied to the shear plane increases and the rock plate breaks. Therefore, in material testing,
It is required to reproduce the state of a material test piece while maintaining it in substantially the same environment as underground.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a control method and a material for a material testing apparatus capable of maintaining a substantially constant vertical stress applied to a shear plane of a material test piece. It is intended to provide a test device.

[0005]

According to the control method of the material testing apparatus of the present invention, the material test piece (1) is housed in the chamber (2), the pressure in the chamber is made higher than the atmospheric pressure, and A compressive load is applied to the material test piece by a compression actuator (9). The compression load (F) applied to the material test piece by the compression actuator is increased, and the pressure in the chamber is reduced with the increase in the compression load.

In some cases, the normal stress (σn) applied perpendicular to the shear surface (b) of the material test piece is maintained substantially constant.

Further, there is a case where the pressure in the chamber is reduced in proportion to the increase of the compression load by the compression actuator.

The material test apparatus of the present invention accommodates a material test piece having a shear surface which is sheared when a shearing force is applied, in a chamber, and makes the pressure in the chamber higher than the atmospheric pressure, and A compression load is applied to the test piece by a compression actuator. The material testing apparatus includes a load sensor (12) for detecting a compression load by the compression actuator, an ambient pressure detection sensor (26) for detecting a pressure in the chamber, and an ambient pressure actuator for increasing / decreasing the pressure in the chamber. (23) and an ambient pressure target value generating section (41) for receiving a signal from the load sensor and generating a target value of the ambient pressure (Pc). A feedback control loop is formed by an ambient pressure actuator and an ambient pressure detection sensor, and the ambient pressure target value generation unit calculates a value obtained by multiplying a compression load detected by the load sensor by a proportional constant by a pressure in the chamber at the start of the experiment. An ambient pressure target value is generated by subtracting from an initial ambient pressure, and the feedback control loop determines that the detected value of the ambient pressure detection sensor is the ambient pressure target value. As a Shirubechi controls the ambient pressure actuator.

The proportionality constant is a square of the sine value of the angle (θ) between the pressing direction of the compression actuator and the shear surface, and the square of the sine value of the material test piece in a plane perpendicular to the pressing direction of the compression actuator. It may be the value divided by the cross-sectional area.

[0010]

Next, an embodiment of a material testing apparatus according to the present invention will be described. FIG. 1 is a block diagram showing the configuration of an embodiment of the material testing apparatus of the present invention. FIG. 2 is a schematic diagram illustrating stress and shear force applied to a material test piece. FIG. 3 is a flowchart of a material test.
4A and 4B are time charts of a material test, in which FIG. 4A is a time chart of an ambient pressure, FIG. 4B is a time chart of a displacement of an actuator for an ambient pressure, and FIG. 4C is a time chart of an output of a compression displacement sensor. 5A and 5B are time charts of the material test, in which FIG. 5A is a time chart of the detected value of the load sensor, and FIG. 5B is a time chart of the stress σn perpendicular to the shear plane.

In FIG. 1, a material test piece 1 is housed in an airtight chamber 2. Further, the fixed support portion 3 and the movable support portion 4 are arranged to face each other with the material test piece 1 interposed therebetween. A cylindrical sealing material 5 covers the distal end of the fixed support 3, the distal end of the movable support 4, and the material test piece 1. And the fixed support part 3 includes
A water passage 6 through which water flows toward the material test piece 1 is formed, while a drain passage 7 is formed in the movable support portion 4. The movable support 4 is driven and moved by a hydraulic compression actuator 9. The amount of movement of the movable support part 4, that is, the amount of displacement of the drive part of the compression actuator 9, is detected by the compression displacement sensor 11. The load sensor 12 detects a load F applied to the material test piece 1 by the compression actuator 9. Further, the inside of the chamber 2 is provided with an intensifier 1 comprising a high-pressure gas cylinder, a compressor, and the like.
7 is connected via a pipe 16. Also, piping 1
A cylinder device 21 is connected to 6, and a piston 22 of the cylinder device 21 is driven by a hydraulic actuator 23 for ambient pressure. The amount of movement of the piston 22, that is, the amount of displacement of the drive unit of the actuator for ambient pressure 23 is detected by the displacement sensor for ambient pressure 24. Furthermore, piping 16
Is provided with an ambient pressure detection sensor 26 for detecting an ambient pressure Pc which is a pressure in the chamber 2.

A compression target value generator 31 serving as a compression target value generator outputs a compression control target input signal Ei to an adder 32. The detection signal Da of the compression displacement sensor 11 is amplified by the sensor amplifier 30 and output to the adding unit 32. The adder 32 calculates a difference signal Er by subtracting the compression displacement detection signal Da from the compression control target input signal Ei, and outputs the difference signal Er via the amplifier 33 to the servo valve of the compression actuator 9. 34.

An ambient pressure target value generator 41 as an ambient pressure target value generator outputs an ambient pressure control target input signal Es to an ambient pressure adder 42. The output signal Ds from the ambient pressure displacement sensor 24 is amplified by the sensor amplifier 43 and output to the ambient pressure adding unit 42 via the displacement control switch 45a. Further, the ambient pressure detection sensor 26
Is amplified by the sensor amplifier 44 and output to the ambient pressure addition unit 42 via the pressure control switch 45b. When one of the switches 45a and 45b is ON, the other is OFF. The detection signal E of the load sensor 12 is supplied to the ambient pressure target value generator 41.
f is input via the sensor amplifier 46, and the detection signal Dp of the ambient pressure detection sensor 26 is input. The output of the ambient pressure addition unit 42 is supplied to an amplifier 47.
Is input to the servo valve 48 of the actuator 23 for ambient pressure.

In the material testing apparatus having such a configuration, when the compression actuator 9 is operated, a compressive load F is applied to the material test piece 1. The chamber 2 is filled with an inert gas such as argon gas by the pressure intensifier 17,
The pressure in the chamber 2 is increased to a higher pressure than the atmospheric pressure, and an ambient pressure Pc can be applied to the material test piece 1 from the surroundings. This ambient pressure Pc is equal to the ambient pressure actuator 2
3 can be adjusted. Thus, as shown in FIG. 2, the load F and the ambient pressure Pc are applied to the material test piece 1. If the cross-sectional area of the material test piece 1 in a plane perpendicular to the load direction of the load F is A, the stress σf becomes F / A.

Further, the material test piece 1 has a shear surface b such as a tomographic surface which is relatively low in shearing strength and shears when a large load F is applied. It is inclined at an angle θ to the direction. In addition,
In FIG. 2, the symbol σn is a stress applied perpendicular to the shear plane b, and the symbol τ is a shear force applied to the shear plane b. And
The mechanical balance is as shown in the following equation (1). 1) Pc = σn− (sinθ × sinθ) × σf In the ground, the stress σn is substantially constant and the stress σf increases (that is, the shearing force τ increases), so that the shear plane b as the fault plane b The phenomenon of slippage has occurred.

Therefore, in the material testing apparatus, in order to reproduce this phenomenon, the ambient pressure Pc is reduced and the stress σn is maintained substantially constant with an increase in the load F (ie, A × σf) (that is, the stress σn is kept substantially constant). , Maintaining the initial stress σn0). When the load F is 0, the stress σ
n is equal to the ambient pressure Pc. Then, (sinθ ×
sin θ) / A is determined before the material test and is constant during the material test, so that it is calculated in advance. This value is treated as a constant in the control during the material test.

As described above, in this material testing apparatus,
The stress σn perpendicular to the shear plane b is maintained substantially constant,
The flow of the material test will be described based on the flowchart of FIG. First, in step 1, the intensifier 1
At 7, the inside of the chamber 2 is pressurized to a pressure higher than the atmospheric pressure. Further, the displacement control switch 45a is ON, and the ambient pressure target value generator 41, the ambient pressure adding section 42, the servo valve 4
8, an ambient pressure actuator 23 and an ambient pressure displacement sensor 24 constitute a displacement feedback control loop, and the ambient pressure adding section 42 outputs an output signal Ds of the ambient pressure displacement sensor 24 from the ambient pressure control target input signal Es.
Is output to the servo valve 48. The ambient pressure target value generator 41 outputs the ambient pressure control target input signal E.
A target position signal is output as s, and the piston 22 is set to the center position. In step 2, when the pressure in the chamber 2 reaches the target pressure by the pressure intensifier 17, the ambient pressure detection sensor 26 detects the ambient pressure Pc, which is the initial stress σn0, as an initial value, and outputs a detection signal to an ambient pressure target value generator. Input to 41. The storage unit is provided in the ambient pressure target value generator 41 and stores the initial value of the ambient pressure Pc. Further, the switch 45a for displacement control is turned off, and the switch 45b for pressure control is turned on to set the ambient pressure target value generator 41,
A pressure feedback control loop is formed by the ambient pressure addition unit 42, the servo valve 48, the ambient pressure actuator 23, the ambient pressure detection sensor 26, and the like. The ambient pressure addition unit 42 detects the ambient pressure from the ambient pressure control target input signal Es. The detection signal Dp of the sensor 26 is subtracted and the servo valve 4
8 is output. Then, the ambient pressure target value generator 41
Outputs the initial value of the ambient pressure Pc which is the target pressure signal as the ambient pressure control target input signal Es, and maintains the ambient pressure Pc at the initial value, that is, the initial stress σn0.

Next, in step 3, the compression actuator 9 is manually operated, and the movable support 4 is moved toward the material test piece 1. Then, in step 4, when the movable support unit 4 presses the material test piece 1 and the load sensor 12 detects the load, the compression actuator 9 is stopped. Next, in step 5, the compression displacement sensor 11 is reset and its current position is set to zero. This completes the preparation for the material test. And
In step 6, the material test is started, the compression target value generator 31 outputs a target displacement signal that increases at a constant speed, and the compression actuator 9 operates as shown in FIG. The part 4 is moved at a constant speed toward the material test piece 1, and a compressive load F is applied to the material test piece 1. This load F gradually increases as shown in FIG. In performing the water permeability test, water is injected from the water passage 6 toward the material test piece 1, and water that has passed through the material test piece 1 is drained from the drain passage 7.

In step 7, the load F applied to the material test piece 1 is detected by the load sensor 12 and output to the ambient pressure target value generator 41. In step 8, the ambient pressure target value generator 41 obtains the ambient pressure Pc, which is the target value, from the above equation (1). That is,
The value obtained by multiplying the constant (sinθ × sinθ) / A by the load F is used as the initial stress σ which is the initial value of the stored ambient pressure Pc.
By subtracting from n0, the target value of the ambient pressure Pc is determined, and the procedure goes to step 9. In step 9, the ambient pressure target value generator 4
1 outputs the target value of the ambient pressure Pc to the ambient pressure addition unit 42, and operates the ambient pressure actuator 23 as shown in FIG. 4B to reduce the pressure in the chamber 2 to the ambient pressure Pc. The target value is set. Then, returning to step 6, steps 6 to 9 are performed, for example, by 0.2
It repeats every second. Then, the pressure in the chamber 2 is gradually decreasing in proportion to the increase of the load F as shown in FIG. Further, as shown in FIG. 5B, the stress σn perpendicular to the shear plane b is maintained substantially constant. In this manner, the material test is performed, and the material test piece 1 is sheared along the shear plane b to break, and the load sensor 1
It is also possible to carry out until the output of No. 2 becomes substantially zero, or to stop the material test piece 1 halfway without breaking it.

As described above, in this embodiment, the load F can be increased while the stress σn perpendicular to the shear plane b is maintained substantially constant, so that the actual underground state is substantially reproduced. be able to. The temperature in the chamber 2 can be controlled to be high. Further, it is not always necessary to perform the water permeability test.

[0021]

According to the present invention, since the compression load applied to the material test piece by the compression actuator is increased and the pressure in the chamber is reduced with the increase in the compression load, the material test is performed. Changes in the normal stress applied perpendicular to the shear plane of the piece are reduced. Therefore, in the material test, the state of the material test piece can be reproduced while maintaining the same environment as underground as much as possible. In particular,
When the vertical stress is maintained substantially constant, the environment can be further substantially the same as underground.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a material testing apparatus according to the present invention.

FIG. 2 is a schematic diagram illustrating stress and shear force applied to a material test piece.

FIG. 3 is a flowchart of a material test.

4A and 4B are time charts of a material test, in which (a) is a time chart of an ambient pressure, (b) is a time chart of a displacement of an actuator for an ambient pressure, and (c) is a time chart of an output of a displacement sensor for compression. It is.

5A and 5B are time charts of a material test, in which FIG. 5A is a time chart of a detection value of a load sensor, and FIG. 5B is a time chart of a stress σn perpendicular to a shear plane.

[Explanation of symbols]

θ Angle between the pressing direction of the compression actuator and the shear plane σn Stress perpendicular to the shear plane b b Shear plane F Compressive load Pc Ambient pressure 1 Material test piece 2 Chamber 9 Compression actuator 12 Load sensor 23 Ambient pressure actuator 26 Around Pressure detection sensor 41 Ambient pressure target value generator (Ambient pressure target value generator)

Claims (5)

[Claims] 1. A control method in a material test apparatus, wherein a material test piece is housed in a chamber, a pressure in the chamber is set higher than the atmospheric pressure, and a compressive load is applied to the material test piece by a compression actuator. A method for controlling a material test apparatus, comprising: increasing a compression load applied to the material test piece by the compression actuator, and reducing a pressure in a chamber with the increase in the compression load. . 2. A material test piece having a shear surface that is sheared when a shear force is applied is housed in a chamber, the pressure in the chamber is made higher than atmospheric pressure, and a compression actuator is attached to the material test piece. In the control method in the material test apparatus applying a compressive load, the compressive actuator increases the compressive load applied to the material test piece, and with the increase of the compressive load, reduces the pressure in the chamber. A method for controlling a material test apparatus, wherein a vertical stress applied perpendicular to the shear surface is maintained substantially constant. 3. The control method according to claim 1, wherein the pressure in the chamber is reduced in proportion to an increase in the compression load by the compression actuator. 4. A material test piece having a shear surface that is sheared when a shearing force is applied is housed in a chamber, the pressure in the chamber is made higher than atmospheric pressure, and a compression actuator is attached to the material test piece. In a material testing device that applies a compressive load by: a load sensor that detects a compressive load by a compressing actuator, an ambient pressure detecting sensor that detects a pressure in a chamber, an actuator for an ambient pressure that increases / decreases a pressure in a chamber, A signal from the load sensor is input, and an ambient pressure target value generation unit that generates a target value of the ambient pressure is provided. Feedback control is performed by the ambient pressure target value generation unit, the ambient pressure actuator, and the ambient pressure detection sensor. A loop is formed, and the ambient pressure target value generation unit multiplies the compression load detected by the load sensor by a proportional constant. The value is subtracted from the initial ambient pressure, which is the pressure in the chamber at the start of the experiment, to generate an ambient pressure target value.In the feedback control loop, the detection value of the ambient pressure detection sensor becomes the ambient pressure target value. A material testing device characterized by controlling an actuator for ambient pressure as described above. 5. The method according to claim 5, wherein the proportionality constant is a square value of a sine value of an angle formed between the pressing direction of the compression actuator and the shear surface, and is a cross-sectional area of the material test piece in a plane perpendicular to the pressing direction of the compression actuator. The material testing apparatus according to claim 4, wherein the value is a value obtained by dividing the value.