JPS6323492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a material testing machine, and more specifically:
This invention relates to a material testing machine with a function to correct the deflection of the testing machine itself.

Generally, a material testing machine applies tensile force or compressive force to a test piece to cause displacement, and measures the load and displacement amount at that time. Therefore, it goes without saying that the test piece itself is distorted by the load applied to it, but the testing machine itself is also slightly bent and deformed.

Conventional testing machines did not compensate for the deflection of the testing machine itself, so they had the disadvantage of causing errors when testing specimens with high rigidity or requiring precision.

Therefore, the present inventors memorized in advance the relationship between the amount of deflection of the testing machine and the load applied to the test piece, calculated the deflection of the testing machine based on the load applied to the test piece, and calculated the amount of deflection using the test machine. We have already proposed a material testing machine that can automatically calculate the true amount of strain in a test piece by subtracting it from the displacement stroke of . This proposal corrected the deflection of the testing machine, making it possible to conduct more accurate tests. However, in a test where a spring with an extremely large spring constant is used as a test piece and is subjected to a high-speed load to displace it to a preset amount of strain, the rate of increase in load is the response rate of the load measurement amplifier. In such cases, the amount of strain on the test piece is calculated by correcting the displacement stroke of the testing machine using the amount of deflection of the testing machine calculated from the measured load value, and that value is determined as the set strain. If the load is stopped immediately when the specified amount is reached, an error will occur in the testing machine's calculation of the amount of deflection due to the delay in detecting the load, causing the problem that the amount of strain on the test piece will be different from the set amount of strain.

The present invention was made in view of the above, and regardless of the spring constant of the test object or the load speed of the test,
The purpose of the present invention is to provide a material testing machine that can stably match the amount of strain in a test object with the set amount of strain.

A feature of the present invention is that the relationship between the amount of deflection of the testing machine and the load applied to the test piece is memorized in advance, the amount of deflection of the testing machine is calculated based on the load applied to the test piece, and this amount of deflection is used in the test. The amount of strain on the test piece is calculated by subtracting it from the displacement stroke of the machine, and the displacement of the testing machine is continued until the value reaches the preset amount of strain. When the set amount of strain is reached, the displacement is stopped for a predetermined period of time, and then The test piece is configured to calculate the amount of deflection of the testing machine again based on the load after a predetermined period of time has elapsed, calculate the amount of strain in the test piece, and then apply displacement again using the testing machine until the value reaches the set amount of strain. It is in.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. Note that this example shows an example of a compression test.

The main body of the test machine rotatably supports two left and right screw rods 2 and 3 on a table 1.
is rotated by a pulse motor 4 by the same amount on the left and right through a timing belt 5, and the crosshead 6 is engaged with the screw rods 2 and 3, so that the crosshead 6 descends according to the rotation angle of the pulse motor. There is. A lower pressure platen 7 is provided at the center of the table 1, and an upper pressure platen 8 is provided at the center of the lower surface of the crosshead 6, and a load cell 9 is installed for converting the load acting on the upper pressure platen 8 into an electric quantity.

The arithmetic control device 10 is composed of a microprocessor, and includes a pulse generation circuit 11, a counter 12 for counting the number of pulses, and an arithmetic device 13, and is connected to a storage device 14 for storing programs, function formulas, numerical tables, etc. has been done.

Also, set the crosshead speed (v) and the set strain amount (x) of the test piece from the keyboard 16,
It is possible to instruct the crosshead to rise or fall. The pulse output of the pulse generation circuit 11 is amplified by a pulse motor drive amplifier 17 to drive the pulse motor 4. The electrical signal from the load cell 9 is amplified by the load measuring amplifier 18, converted into a digital quantity by the A/D converter 19, and inputted to the arithmetic and control unit 10, and the digital quantity is displayed on the load display 20. The calculation result by the calculation device 13 is displayed on the displacement display 21.

The storage device 14 stores the relationship between the amount of deflection of the testing machine and the load, and this relationship is generally as shown in FIG. 2. If the amount of deflection is ΔS and the load is P, then ΔS= It can be expressed as f(P), and can be approximated by ΔS=AP+B (A and B are constants) in the practical range. Therefore, this relationship may be stored in the storage device 14 as a functional formula as described above, or
Or you can memorize it in a numerical table.

Next, the operation of the above embodiment will be explained along with the method of use.

Place the test piece Tp on the lower pressure plate 7 on the table.

After setting the crosshead speed (v) and the set strain amount (x) of the test piece from the keyboard, press the crosshead lowering instruction button to start the program.

The calculation program, as shown in FIG.
Find the value S by subtracting the amount of deflection ΔS from This value S is the strain amount of the test piece calculated by subtracting the deflection amount ΔS of the testing machine corresponding to the detected load value P from the displacement stroke C of the testing machine. This calculated strain amount S is the set strain amount X that has been input in advance.
If it has not reached the threshold, the pulse generating circuit 11 outputs one pulse to drive the crosshead and returns to the first step. If the threshold has been reached, the crosshead is driven for a predetermined period of time, Pause for 0.2 seconds. And the deflection amount ΔS of the testing machine based on the detected load value P after stopping for 0.2 seconds
By correcting the displacement stroke C, the amount of strain S of the test piece is calculated. Then, it is determined whether the calculated strain amount S has reached the set strain amount, and if it has not reached the set strain amount, the pulse generation circuit 11 outputs one pulse to drive the crosshead.
Return to the first step. When S reaches X, the test ends.

In this way, the displacement stroke of the testing machine is corrected by the amount of deflection of the testing machine to calculate the amount of strain on the test piece, and the crosshead of the testing machine is driven until the amount of strain reaches the set amount of strain, and the calculated amount of strain is calculated. When the set amount of strain is reached, the drive is stopped for a predetermined time to recover the delay of the load detection system, and the true amount of strain is newly calculated based on the correct load detection value, and the crosshead is operated again until the value reaches the set amount of strain. is driven. If there is no delay in the load detection system, the amount of strain calculated after stopping for a predetermined period of time becomes equal to the amount of strain calculated before then, and the crosshead is immediately stopped.

As explained above, according to the present invention, it is possible to always accurately strain a test piece to a set strain amount without being affected by the spring constant of the test piece or the test speed, and it is possible to obtain stable test data. can.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the embodiment of the present invention, Fig. 2 is a characteristic diagram showing the correlation between the load P of the testing machine and the amount of deflection, and Fig. 3 is a flowchart showing the program of the embodiment of the invention. be. DESCRIPTION OF SYMBOLS 1...Table, 2, 3...Screw rod, 4...Pulse motor, 6...Crosshead, 9...Load cell, 11...Pulse generation circuit, 12...Counter, 13...Arithmetic unit, 14... Storage device.

Claims (1)

[Claims] 1. A displacement device that applies a known displacement to both ends of the test piece against the stress of the test piece, a load measuring device that measures the load that the displacement device applies to the test piece, and a displacement device that measures the load that the displacement device applies to the test piece. means for storing the correlation of the amount of deflection, and using the correlation, calculates the amount of deflection of the displacement device based on the measured load value, corrects the known amount of displacement with the amount of deflection, and calculates the amount of strain in the test piece. means for calculating, a means for comparing the calculated strain amount with a set strain amount input in advance and driving the displacement device until the calculated strain amount reaches the set strain amount; and a means for driving the displacement device until the calculated strain amount reaches the set strain amount; When the strain amount is reached, the driving of the displacement device is stopped for a predetermined period of time, and the displacement device is again operated until the calculated strain amount calculated based on the load measurement value after the predetermined period of time reaches the set strain amount. A deflection compensation material testing machine equipped with a means to drive the device.