JP2003307476A - Material testing machine with explosion preventive function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material testing machine with an explosion preventive function which surely prevents an explosion in a compression test of high- strength concrete and low-strength concrete and which surely prevents the test from being finished without developing a crack. <P>SOLUTION: In the material testing machine having the explosion preventive function, after the test has been started, a load onto a specimen W is stopped at the point when a reduction rate of a test force reaches a set value. An estimated strength S<SB>f</SB>of the specimen W is input, the set value of the reduction rate used in the explosion preventive function is automatically changed according to its input content, a sensitivity of the explosion preventive function is adapted to the strength of the specimen W, the explosion is prevented surely, and the crack is developed surely in the specimen W after the test has been finished. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a material testing machine,
More specifically, the present invention relates to a material testing machine for performing a compression test on concrete and the like, and a material testing machine with a bursting prevention function having a function of preventing explosion of a specimen.

[0002]

2. Description of the Related Art As a general method for measuring the maximum strength of concrete, a method of performing a compression test on a specimen made of concrete having a specified dimension using a material testing machine is adopted.

In the compression test of concrete, the compressive stress applied to the specimen is usually increased at a constant rate, and the load is stopped after the maximum strength appears. In such a test, if the compressive force is continuously applied to the concrete after the maximum strength appears, the concrete eventually breaks, and a phenomenon called "explosion" occurs in which fragments are scattered around (Fig. 4).

Since explosion of concrete is very dangerous, in a material testing machine for conducting this kind of test,
Generally equipped with explosion protection. This explosion prevention function is to automatically stop or restore the origin of the load mechanism of the material testing machine by utilizing the transition of the test force in the concrete compression test as shown in FIG. That is, in the compression test of concrete, the test force starts to decrease due to cracking and growth of the specimen after the appearance of the maximum strength, but the explosion prevention function is to constantly monitor the test force and reduce it. A function that automatically stops the load mechanism or returns to the origin when the reduction rate reaches a preset rate.

[0005]

By the way, in the compression test of concrete, the test force starts to decrease after the appearance of the maximum strength as described above, but the time until the explosion after the decrease depends on the strength of the concrete. That is, in concrete with high strength, as shown in FIG. 5, since the time T until the explosion occurs after the appearance of the maximum strength is short, if the explosion prevention function does not work immediately after the appearance of the maximum strength, the specimen will explode. Resulting in. On the other hand, in the case of concrete having low strength, as shown in FIG. 6, the time T until the explosion occurs after the appearance of the maximum strength is long.

Here, in the compression test of concrete, whether or not the maximum strength could be detected is confirmed by observing the specimen after the test and checking for cracks. Alternatively, when testing low-strength concrete, make settings for high-strength concrete and set a low reduction rate of the test force for stopping the load mechanism or returning to the origin.In other words, operate the explosion-proof function with high sensitivity. If such a setting is made, the load mechanism stops or returns to the origin immediately after the appearance of the maximum strength, and there is a problem that it is not possible to confirm whether or not the true maximum strength can be detected because the specimen does not crack.

The present invention has been made in view of the above circumstances, and in the compression test of high-strength and low-strength concrete, it is possible to surely prevent explosion and at the same time, complete the test without causing cracks. The purpose of the present invention is to provide a material testing machine with explosion proof function that can reliably prevent the

[0008]

In order to achieve the above object, the material testing machine with explosion proof function of the invention according to claim 1 is a load mechanism for applying a compressive load to a specimen and a test which acts on the specimen. The test force detecting means for detecting the force and the output of the test force detecting means are taken in, and it is determined whether or not the rate of decrease of the test force acting on the specimen reaches the set value, and the set value is reached. In the material testing machine equipped with explosion-prevention means to prevent the explosion of the specimen by automatically stopping or returning the origin to the load mechanism, the input means for inputting the expected strength of the specimen and the input contents It is characterized in that it is provided with automatic changing means for automatically changing the set value of the reduction rate of the test force used in the explosion preventing means.

Further, in order to achieve the same object, the second aspect
The material testing machine with explosion proof function according to the invention relates to a load mechanism for applying a compressive load to the test piece, a test force detecting means for detecting a test force acting on the test piece, and a test force detecting means for the test force detecting means. By capturing the output, determine whether the rate of decrease in the test force that acts on the test piece has reached the set value, and when the set value is reached, automatically stop or return to the origin of the load mechanism. According to the magnitude of the output of the test force detection means during the test, in the material testing machine equipped with the explosion prevention means to prevent the explosion of the specimen, It is characterized by having an automatic changing unit that automatically and sequentially changes.

According to the present invention, the operation sensitivity of the explosion proof function is automatically changed according to the strength of the concrete under test.
In low-strength concrete, the intended purpose is achieved by automatically changing the setting so that the sensitivity is low.

That is, in the invention according to claim 1, whether the concrete has high strength or low strength can be almost predicted by the components constituting the concrete, the mixing ratio thereof, and the like. Take advantage of many things,
By inputting the expected strength (expected maximum strength) of the concrete under test, the set value of the reduction rate of the test force, which is the operation sensitivity of the explosion proof function, is automatically changed according to the input contents.

On the other hand, according to the second aspect of the invention, the set value of the decrease rate of the test force, which is the operation sensitivity of the explosion proof function, is automatically set according to the magnitude of the test force acting on the specimen during the test. Change sequentially. In other words, if the operation sensitivity of the explosion protection function is increased as the test force increases, if the maximum strength of the specimen is low, the explosion protection function operates with low sensitivity and the maximum strength is high. In some cases, the explosion protection function operates under high sensitivity.

According to each of the inventions according to claims 1 and 2 described above, the operator does not change the operation sensitivity of the explosion-preventing function, and the explosive-preventing function has low sensitivity when testing low-strength concrete. It works, and when testing high-strength concrete, the explosion-proof function operates with high sensitivity, and the test ends without cracking the test piece while reliably preventing the test piece from exploding. It is possible to reliably prevent the occurrence of.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of the present invention, in which a schematic diagram showing a mechanical configuration and a block diagram showing an electrical configuration are shown together.

The tester main body 1 is provided with two screw rods 12a and 12b along a vertical direction on a main body frame 11, and a crosshead 13 whose position can be vertically adjusted along the screw rods 12a and 12b. The table 15 is arranged below the cross head 13 and is vertically moved by a load cylinder 14 provided in the main body frame 11.

The concrete specimen W to be tested is arranged between the pressure plate 16 mounted on the lower surface of the crosshead 13 and the pressure plate 17 mounted on the upper surface of the table 15. In this state, the load cylinder 14 is mounted. By driving and raising the table 15, a compressive load acts on the sample W.

The compressive load acting on the specimen W, that is, the test force, is detected by the pressure cell 18 attached to the load cylinder 14, and the detection output is mainly transmitted to the CPU via the A / D converter 21. It is taken into the control device 2 every moment.

The load cylinder 14 is operated by hydraulic oil supplied from a hydraulic pressure source (not shown) via a servo valve 19, and this servo valve 19 is controlled by the control device 2 to D.
The valve opening degree is controlled by the operation signal supplied via the -A converter 22. In the control device 2, the pressure cell 18
The momentary test force detected by generates an operation signal to be supplied to the servo valve 19 so as to match a preset target value. Specifically, after performing a calculation such as PID on the deviation between the preset target value and the detected value of the test force by the pressure cell 18 every moment,
It is fed back to the servo valve 19 as an operation signal via the DA converter 22. The detection value of the test force every moment during the test is displayed on the display 23 and is output to the plotter 24.

An operation panel 25 for setting various test conditions and the like is connected to the control device 2,
The operation panel 25 includes a switch 25a for inputting the expected strength of the sample W prior to the test.

The operation program written in the control device 2 takes in the detected value of the test force every moment during the test as described above, and is in parallel with the routine for feedback controlling the valve opening of the servo valve 19. do it,
It includes a routine for explosion prevention, in which the test force is monitored every moment and the load cylinder 14 is automatically stopped and the home position is restored when the decrease rate of the test force reaches a set value.

FIG. 2 is a flowchart showing the contents of the explosion prevention routine. The operation of the embodiment of the present invention will be described below with reference to FIG.

First, prior to the test, test conditions and the like are set from the operation panel 25, and at the same time, the switch 25a is operated to input the expected strength S _f of the sample W. By inputting this expected strength S _f , the decrease rate P of the test force, which is the sensitivity of the explosion prevention function, is automatically set. In this example, the reduction rate is set in three stages, and the higher the predicted strength S _f , the higher the sensitivity of the explosion protection function, that is, the load cylinder 14
The reduction rate at which to stop is set to a low value.

More specifically, the expected strength S _f is 70 N /
If it is mm ² or more, the explosion proof function has maximum sensitivity (the reduction rate P of the test force for operating the explosion proof function is the minimum value P _min ).
And the expected strength S _f is 20 N / mm ² or more and 70 N
If it is less than / mm ² in the intermediate sensitivity (reduction ratio P of test force to operate the explosion certain device features an intermediate value P _mid), minimum sensitivity (also explosion preventing long expected intensity S _f is less than 20 N / mm ² The reduction rate of the test force P that operates the function is the maximum value P
_max ) is set.

After that, by giving a test start command, the loading cylinder 14 is activated and the table 15 is raised, and a compressive load according to the target value is applied to the test piece W, during which the test that acts on the test piece W is performed. Every time the force is taken in, the change over time of the test force including the latest test force and several test forces immediately before that is calculated, and when the test force is decreasing, the decrease rate P _t is calculated. When the reduction ratio P set in advance is reached, the load cylinder 14 is automatically stopped and returned to the origin.

According to the above-mentioned embodiment, by simply inputting the expected strength S _f of the test piece W, the explosion-proof function operates at the maximum sensitivity in the test of high-strength concrete, and the test force reaches the maximum value. The load cylinder 14 immediately stops and returns to the origin after the decrease, and the explosion-proof function operates at the minimum sensitivity when testing low-strength concrete, and the test force reaches the maximum value and decreases. After turning, the load cylinder 14 further rises to some extent, stops, and returns to the origin. Therefore, it is possible to reliably prevent the occurrence of explosion in the test of high-strength concrete, and at the same time, to end the test in the state of reliably cracking in the test of low-strength concrete.

Here, in the above embodiment, an example in which the operation sensitivity of the explosion prevention function is automatically set based on the input content of the expected strength S _f of the sample W has been shown. It is also possible to automatically set the operation sensitivity of the explosion protection function without performing the above. FIG. 3 is a flowchart showing an example of the routine.

In this example, the operation sensitivity of the explosion proof function is set to three levels as in the previous example, and the operation sensitivity is automatically and sequentially increased according to the detection result F of the test force during the test. It will become.

That is, when the test start command is given, the load cylinder 14 is activated and the table 15 is raised in the same manner as described above, and the compressive load according to the target value is applied to the sample W. Then, during that time, every time the test force F acting on the specimen W is taken in momentarily, when the magnitude of the test force F is less than 20 N / mm ² , the sensitivity of the explosion proof function is the minimum sensitivity (load cylinder 14 Of the test force for stopping the test force P = P _max ) and the test force is set to 2
0N / mm ² or more 70N / mm ² lower than entering the sensitivity between the automatically changed to an intermediate sensitivity (P = P _mid), more sensitive if the test force reaches a higher 70N / mm is the maximum sensitivity (P
= P _min ).

Then, while automatically changing the operation sensitivity of the explosion proof function in accordance with the magnitude of the test force during the test, the latest test is taken every time the test force is taken in, as in the previous example. The time-dependent change of the test force including the force and several test forces immediately before that is monitored, and when the test force is decreasing, the decrease rate P _t is set in advance and reaches the decrease rate P. Then, the load cylinder 14 is automatically stopped,
Return to the origin.

In the example of FIG. 3 as well, in the test of high-strength concrete, the operation sensitivity of the explosion-preventing function is automatically increased to surely prevent explosion, and at the same time, the strength of the low-strength concrete is In the test, the operation sensitivity of the explosion proof function is automatically lowered, and the specimen W can be reliably cracked at the end of the test.

[0031]

As described above, according to the present invention, by inputting the expected strength of the concrete under test (Claim 1) or with the increase of the test force during the test (Claim 2), Since the operation sensitivity of the explosion protection function is automatically set to the optimum value, the operator can set the operation sensitivity of the explosion protection function without fail to reliably prevent the occurrence of explosion when testing concrete of various strengths including high strength. At the same time, it is possible to surely prevent the occurrence of the problem that the test is terminated without causing cracks in the test of low-strength concrete.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, in which a schematic diagram showing a mechanical configuration and a block diagram showing an electrical configuration are shown together.

FIG. 2 is a flow chart showing the contents of a routine for explosion prevention written in the control device 2 in the embodiment of the present invention.

FIG. 3 is a flowchart showing the contents of a routine for explosion prevention according to another embodiment of the present invention.

FIG. 4 is a graph for explaining transition of test force and explosion in a compression test of concrete.

FIG. 5 is a graph showing an example of explosion occurrence in a compression test of high-strength concrete.

FIG. 6 is a graph showing an example of occurrence of explosion in a compression test of low-strength concrete.

[Explanation of symbols]

1 Testing machine body 11 body frame 12a, 12b screw rod 13 crosshead 14 Load cylinder 15 tables 16,17 pressure plate 18 Pressure cell 19 Servo valve 2 controller 21 A-D converter 22 D-A converter 25 Operation panel 25a Predictive strength input switch W specimen

Claims (2)

[Claims] 1. A loading mechanism for applying a compressive load to a specimen,
A test force detecting means for detecting a test force acting on the specimen,
By taking in the output of the test force detection means, it is determined whether or not the rate of decrease of the test force acting on the specimen reaches the set value, and when the set value is reached, the load mechanism is automatically operated. In a material testing machine equipped with explosion-prevention means for preventing explosion of a specimen by stopping or returning to the origin, input means for inputting the expected strength of the specimen and the test used by the explosion prevention means based on the input contents A material testing machine with an explosion proof function, characterized in that it is provided with automatic changing means for automatically changing the set value of the force reduction rate. 2. A loading mechanism for applying a compressive load to the specimen,
A test force detecting means for detecting a test force acting on the specimen,
By taking in the output of the test force detection means, it is determined whether or not the rate of decrease of the test force acting on the specimen reaches the set value, and when the set value is reached, the load mechanism is automatically operated. In a material testing machine equipped with explosion-prevention means that prevents explosion of the test piece by stopping or returning to the origin, the test force used by the explosion-prevention means should be adjusted according to the output of the test force detection means during the test. A material testing machine with an explosion proof function, characterized in that it is equipped with automatic changing means for automatically changing the set value of the reduction rate in sequence.