JP2774688B2 - Load measuring method in material testing machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a load measuring method for a material testing machine, and more particularly to a load measuring method for a material testing machine for performing a material test under a high temperature and vacuum environment. It is.

[Conventional technology]

Conventionally, as one of the material tests under high temperature and vacuum environment,
There is a so-called stress relaxation test.

This stress relaxation test is a test for measuring a temporal decrease in stress in a state in which all attempts are kept constant, and is generally performed in a sequence as shown in a timing chart of FIG. That is, the test includes a plurality of blocks in units of groups such as constant temperatures T1 and T2, and each block is divided into a plurality of stages in units of load change groups and the like. Specifically, as shown in the drawing, at the start of each block, when the displacement of the load increasing portion in each stage reaches a predetermined load value L1, L2, etc. by performing a displacement control of a constant inclination θ from the standby position, Switching from increasing the displacement to holding is performed, and the displacement is held for a certain time t. Thereafter, the data sampling is completed, the data is recorded on the recording medium, and the process proceeds to the next stage. After the execution of all the stages in each block, the displacement is returned to the standby position once, and then the process proceeds to the next block.

In the above test, a load sensor is used to detect the stress applied to the sample.However, since the load sensor is generally weak to high temperatures, in the case of the above-described test in a high-temperature, A load sensor cannot be installed together with the sample in the vacuum chamber for accommodating the sample to be kept. Therefore, a load sensor is installed outside the chamber. In such a configuration, in order to transmit the load generated in the chamber to the load sensor, the inside of the chamber and the load sensor must be connected by a connection shaft.

[Problems to be solved by the invention]

However, due to such a configuration, when the connecting shaft connecting the inside of the chamber and the load sensor is evacuated to make the inside of the chamber vacuum, the suction is sucked into the chamber, and as a result, a negative load is applied to the load sensor. This condition causes a zero point drift.

Therefore, after the evacuation was completed, the test was started after adjusting the sensor amplifier while checking the meter indication to perform zero adjustment of the load sensor. However, since this adjustment is extremely troublesome in performing the test, the test was performed. In addition to the fact that it takes a long time to actually start the measurement, there is also a problem that it is difficult to perform high-precision load measurement due to manual operation, which causes large variations.

Accordingly, the present invention has been made in view of the above-described conventional problems, and has as an object to provide a load measuring method in a material testing machine capable of performing a high-precision load measurement while eliminating troublesome adjustment work by hand. And

[Means for solving the problem]

In order to solve the above problems, a load measuring method in a material testing machine made according to the present invention includes a vacuum chamber for forming a vacuum and a high-temperature environment, a load detecting means fixed outside the vacuum chamber, and a load detecting means outside the vacuum chamber. A servo-controllable actuator, one end of which is fixed and inserted into the vacuum chamber, and one end connected to the load detecting means, and the other end is a stress transmitting means inserted into the vacuum chamber. A load measuring device for applying a load to the sample by sandwiching the sample between the movable portion and the stress means by moving the movable portion of the actuator, and measuring a load applied to the sample. In the method, the actuator is moved from a state where no sample is sandwiched between the movable portion of the actuator and the stress transmitting means to a state where a sample is sandwiched between the movable portion of the actuator and the stress transmitting means. In this process, the output signal of the load detecting means is monitored, and a sudden change in the output signal of the load detecting means causes the sample to move between the movable part of the actuator and the stress transmitting means. Is detected, the value of the output signal of the load detecting means immediately before the detection is held as a correction value, and the held correction value is added to the output signal of the subsequent load detecting means to obtain a sample. It is characterized by measuring the applied load.

[Action]

In the above configuration, in the vacuum chamber forming a vacuum or high-temperature environment, a load is applied to the sample by sandwiching the sample between the movable portion of the actuator fixed outside the vacuum chamber and the stress transmitting means connected to the load detecting means. And a load applied to the sample is measured, so that a drift component occurs in the output signal of the load detecting means.

However, in the process of moving the movable part of the actuator from a state in which the sample is not sandwiched between the movable part of the actuator and the stress transmitting means to a state in which the sample is sandwiched therebetween, the output signal of the load detecting means is monitored and A sudden change in the output signal of the detecting means detects that the sample is caught between the movable part of the actuator and the stress transmitting means, and holds the value of the output signal of the load detecting means immediately before this detection as a correction value. Since the held correction value is added to a subsequent output signal of the load detecting means, the measured value of the load applied to the sample has a drift component corrected.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the configuration of a material testing machine in which a method according to the present invention is performed. In FIG. 1, reference numeral 1 denotes an electrohydraulic actuator 1 having, for example, a servo valve 1a fixed to a fixed base B. One end of the piston rod 1b is connected to the opening 2a of the vacuum chamber 2 fixed to the fixed base B.
The sample mounting table 1c for mounting and fixing the samples T and P is formed at the end of the sample mounting table 1c.

A bellows 3 is provided between the peripheral edge of the opening 2a of the vacuum chamber 2 and the outer peripheral surface of the piston rod 1b so as to allow the piston rod 1b to move forward and backward with respect to the vacuum chamber 2 while closing the gap therebetween in an airtight state. Is provided. The vacuum chamber 2 also has an opening at a portion facing the opening 2a.
2b is formed, and one end of the stress transmission shaft 4 is inserted into the vacuum chamber 2 through the opening 2b. The other end of the stress transmission shaft 4 is fixed to a load sensor 5 fixed to a fixed base B, so that stress is transmitted to the load sensor 5 via the stress transmission shaft 4.

A bellows 6 is provided between the peripheral edge of the opening 2b of the vacuum chamber 2 and the outer peripheral surface of the stress transmission shaft 4 to close the gap therebetween in an airtight state. The vacuum chamber 2 is further provided with an exhaust port 2c for connecting a vacuum pump (not shown) that evacuates the vacuum chamber 2 and evacuates the vacuum chamber 2.

The other end of the piston rod 1b of the actuator 1 is connected to a core 7b forming a displacement sensor 7 together with a detection coil 7a fixed to a fixed base B.

The vacuum gauge 8 measures the degree of vacuum in the vacuum chamber 2 evacuated by a vacuum pump (not shown).
The thermometer 9 measures the temperature in the vacuum chamber 2 heated by a heater (not shown).

FIG. 2 is a diagram showing an electric circuit configuration related to the material testing machine of FIG. 1. In FIG. 2, a load detection signal output from the load sensor 5 is amplified by a sensor amplifier 11 and then analog-digital ( The signal is converted into a digital signal by an A / D (converter) converter 12 and input to a microcomputer (CPU) 13. The displacement detection signal output from the displacement sensor 7 is amplified by the sensor amplifier 14, converted into a digital signal by the A / D converter 15, and input to the CPU 13. The detection signal output from the vacuum gauge 8 is amplified by an amplifier 16 and then amplified by an A / D converter 17, and the detection signal output from the thermometer 9 is amplified by an amplifier 18 and then converted to a digital signal by an A / D converter 19. And input to the CPU 13 respectively.

The displacement detection signal amplified by the sensor amplifier 14 is obtained by applying an analog target signal output from a digital-analog (D / A) converter 22 for converting a digital target signal output from the CPU 13 to an analog signal to a + input. Adder 21
Is also applied to the-input. The adder 21 calculates a difference between the displacement detection signal and the analog target signal and outputs a deviation signal. The deviation signal is amplified by the servo amplifier 23 and supplied to the servo valve 1a. Accordingly, the actuator 1 operates so that the deviation signal becomes 0, and applies a displacement to the sample TP according to the target signal.

The CPU 13 includes a ROM 13a, which is a read-only memory for storing a control program necessary for the operation, and A / D converters 12, 1
In addition to temporarily storing digital signals input via 5, 17, 19, etc., it has a RAM 13b which is a readable / writable memory used as a work area when processing the input digital signals. Then, in addition to outputting the digital target signal to the D / A converter 22, the CPU 13
And outputs a control signal to the heater 32, and further exchanges data with a personal computer (PC) 41 via a data bus 42 and inputs the data via the A / D converter 12 to the RAM.
The digital data stored in 13b is transferred to P.C41, and data such as target values such as temperature, degree of vacuum, and displacement are received from P.C41.

Note that a keyboard (KB) 41a, a CRT 41b, a floppy disk (FD) driver 41c, a printer 41d, and the like are connected to the PC 41.

Next, a method of measuring a load applied to a sample by the method of the present invention when performing a material test using the above-described material testing machine will be described with reference to a timing chart of FIG.

First, the sample TP is mounted and fixed on the sample mounting table 1c in the vacuum chamber 2. Before and after this, various data required for the test, the test vacuum pressure value, the test temperature value, the piston rod of the actuator 1,
The displacement target value, load target value, etc. of 1b are input, and these data are stored in the FD driver 41c.

Thereafter, the vacuum pump 31 is operated, and the vacuum chamber 2
When the air in the chamber is exhausted, the pressure in the vacuum chamber 2 decreases as shown in FIG. The pressure in the vacuum chamber 2 is monitored by a vacuum gauge 8, and this evacuation process is performed until the pressure in the vacuum chamber 2 reaches a test vacuum pressure value. At this time, since the stress transmission shaft 4 whose one end is inserted into the vacuum chamber 2 is sucked into the vacuum chamber 2,
The load sensor 5 to which the other end of the load transmission shaft 4 is connected,
Although a load is not applied to the samples T and P, a negative load detection signal as shown in FIG.

Although not shown in FIG. 3, the heater 32 is simultaneously operated in the evacuation process to raise the temperature in the vacuum chamber 2 to a test temperature value.

When the pressure and the temperature in the vacuum chamber 2 reached the test vacuum pressure value and the test temperature value, respectively, a target displacement signal was output at time t1, the actuator 1 was operated under displacement control, and the sample TP was placed. The piston rod 1b is moved upward at an arbitrary speed to bring the sample T / P closer to the stress transmission shaft 4. The output of the displacement sensor 7 at this time is shown in FIG.
A displacement signal as shown in FIG. Further, at this time, since the inside of the vacuum chamber 2 has reached the test vacuum pressure value, the output of the load sensor 5 does not change and is maintained at a substantially constant value as shown in the figure. The load detection signal output from the load sensor 5 is sampled and collected at an appropriate cycle and stored in the RAM 13b.

When the sample T / P comes into contact with the stress transmission shaft 4 at the time t2, the output of the load sensor 5 changes suddenly. The sudden change causes the load detection signal S of the output of the load sensor 5 to change.
(= ΔS / Δt) rapidly rises as shown in FIG. 3 (d).
-It can be determined that the load transmission shaft 4 has contacted P. In this way, the load value sampled immediately before the stress transmission shaft 4 comes into contact with the sample T / P is collected as the drift value of the load sensor 5, and this is used as a correction value for correcting a subsequent load detection signal. After the stress transmission shaft 4 comes into contact with the sample T / P, the actual test starts, and the piston rod 1b of the actuator 1 is displaced upward at a predetermined speed,
The detected load signal of the output of the load sensor 5 at this time is collected as test data. When collecting the test data, the correction value is added to each sampling value.

When the detected load signal reaches the predetermined load target value L at the time point t3, the piston rod 1b of the actuator 1 stops moving upward, and the position of the piston rod 1b is held for a predetermined time under displacement control. A load detection signal of the output of the load sensor 5 that changes (decreases) with time is collected, and a stress relaxation curve indicating a decrease in stress with time in a state where the total strain is kept constant is obtained.

The details of the load measurement method outlined above will be described with reference to the flowchart of FIG. 4 showing work performed by the CPU 13 according to a predetermined control program.

The CPU 13 starts operating in response to a start command from the PC 41 after fixing the sample T • P in the vacuum chamber 2, and performs initialization in the first step S1. In this initialization, various setting data set in the PC 41 are received and stored in a predetermined area in the RAM 13b, and an operation of positioning the piston rod 1b of the actuator 1 at a predetermined start position is performed. It performs tasks such as clearing an area in the RAM 13b for storing a correction value described later.

Thereafter, the process proceeds to step S2, in which target values relating to pressure and temperature are set, and based on the target values, the vacuum pump 31 and the heater are set.
Make 32 work. Then, in the following step S3, it is determined whether or not the temperature in the vacuum chamber 2 has reached the target temperature, and the process waits until the determination becomes YES. YES in step S3
If it becomes, the process proceeds to step S4 to determine whether or not the pressure has reached the target pressure. If the determination in step S4 is YES, the process proceeds to step S5, in which a gradually increasing displacement target signal is output, whereby the piston rod 1b of the actuator 1 is output.
Start the ascent operation.

Thereafter, the process proceeds to step S6, where it is determined whether or not the stress transmission shaft 4 has come into contact with the sample T / P based on whether or not the differential value of the detected load signal from the load sensor 5 has increased rapidly. When the determination in step S6 becomes YES, the process proceeds to step S7, where the sampling value of the detected load signal immediately before the determination in step S6 becomes YES is determined as a correction value, and the determined correction value is stored in a predetermined area of the RAM 13b. Store.

Note that the sampling of the detected load signal from the load sensor 5 is performed by an interrupt process executed at each sampling cycle. In the first step S31, the load signal is sampled, and in the subsequent step S32, the correction value is added to the sampled value. Then, the result of this addition is used in the next step S33.
Then, the process returns to the original step at the time of entering the interrupt processing after being stored in a predetermined area of the RAM 13b. Step S32 above
The correction value to be added in is determined in step S7, and before the determination, the correction value added to the sampling value is zero.

After the execution of step S7, the process proceeds to step S8, where it is determined whether or not the load applied to the sample T / P has reached a predetermined value based on the detected load signal from the load sensor 5. Sample T
When the load applied to P reaches a predetermined value, the process proceeds to step S9, where the lifting operation of the piston rod 1b is stopped, and the piston rod 1b is held at that position. Then step S1
The process proceeds to 0, where it is determined whether or not a predetermined time has elapsed from the stop of the piston rod 1b. YES in step S10
If the condition is satisfied, the process proceeds to step S11, where it is determined whether or not the test was the final stage of the block.
In the case of, the process proceeds to step S12 to restart the lifting operation of the piston rod 1b, and then returns to step S8. In step S8, a load judgment different from the previous load value is used.
The ascending operation of 1b is continuously performed.

The final stage test is completed and the judgment in step S11 is Y
If it becomes ES, the process proceeds to step S13, where it is determined whether the test is the last block. The determination in step S13 is N
In the case of O, the process proceeds to step S14 to start the lowering operation of the piston rod 1b, and then proceeds to step S15. Step S
In 15, it is determined whether or not the piston rod 1b has returned to its start position by monitoring the detected displacement signal from the displacement sensor 7. If the determination in step S16 is YES, the process proceeds to step S16, where the piston rod 1b
Stop the descending operation of. Then, the process proceeds to step S17 to clear the correction value determined in step S7, and then returns to step S2 to move to the test of the next block.

When the determination in step S13 is YES, that is, when the test of the last block is completed, the process proceeds to step S18, where predetermined processing is performed on the data collected in step S33, and a series of operations is completed. Although the flowchart for illustration does not show the steps for collecting the detected displacement signal from the displacement sensor 7 by sampling, actually, the sampling value of the displacement is also collected and stored.

According to the load measuring method described above, in the vacuum chamber 2 forming a vacuum or high-temperature environment, the movable portion composed of the piston rod 1b of the actuator 1 fixed outside the vacuum chamber 2 and the load detecting means composed of the load sensor 5 are used. The sample T and the sample T are sandwiched between the connected stress transmission shaft 4 and the sample T.
A drift component occurs in the output signal of the load sensor 5 because a load is applied to P and the load applied to the sample T / P is measured, but between the piston rod 1b and the stress transmission shaft 4 In the process of moving the piston rod 1b from the state in which the sample T / P is not sandwiched to the state in which the sample is sandwiched, the output signal of the load sensor 5 is monitored. Detecting contact of the stress transmission shaft 4 with P, holding the value of the output signal of the load sensor 5 immediately before the detection as a correction value, and adding the held correction value to the output signal of the subsequent load sensor 5 Therefore, the measured value of the load applied to the sample T / P has a drift component corrected.

〔effect〕

According to the present invention as described above, the value of the load signal immediately before the sample is sandwiched is detected and held as a correction value,
Since the held correction value is added to the subsequent load signal, the zero-point drift generated in the load signal by evacuating the vacuum chamber is removed without performing any manual adjustment operation, and high precision Load measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a material testing machine to which a load measuring method according to the present invention is applied, FIG. 2 is a diagram showing an electric circuit configuration of a material testing machine to which a load measuring method according to the present invention is applied, 3 is a timing chart for explaining the load measuring method according to the present invention, FIG. 4 is a flowchart showing work performed by the CPU in FIG. 2 in accordance with a predetermined control program, and FIG. 5 is a schematic diagram of a load relaxation test. It is a timing chart for performing. DESCRIPTION OF SYMBOLS 1 ... Actuator, 1b ... Piston rod (movable part), 2 ... Vacuum chamber, 4 ... Stress transmission shaft (Stress transmission means), 5 ... Load sensor (Load detection means), TP
……sample.

Claims (1)

(57) [Claims] A vacuum chamber for forming a vacuum and high-temperature environment, load detecting means fixed outside the vacuum chamber, and one end of a movable part fixed outside the vacuum chamber and inserted into the vacuum chamber. A servo-controllable actuator, one end of which is connected to the load detecting means, and the other end thereof includes a stress transmitting means inserted into the vacuum chamber, and the movable part of the actuator is moved by moving the movable part. A load measuring method in a material testing machine in which a load is applied to the sample with the sample interposed between the stress transmitting means and the load applied to the sample is measured, wherein the movable part of the actuator and the stress transmitting means The movable part of the actuator is moved from a state where no sample is sandwiched between the sample to a state where the sample is sandwiched between the sample, and in this process, the output signal of the load detecting means is moved. Monitoring that a sample has been caught between the movable part of the actuator and the stress transmitting means by a sudden change in the output signal of the load detecting means. Holding the value of the output signal as a correction value and adding the held correction value to a subsequent output signal of the load detection means to measure a load applied to the sample, wherein a load applied to the sample is measured. .