JPH085533A - Fatigue test piece breakage detector - Google Patents

Abstract

PURPOSE:To save power in breakage detection operation by instructing tension and compression load from a program oscillator, and also taking in a load amount and a strain amount from a load detector and a strain gage to detect a predetermined amount of drop in load. CONSTITUTION:A fatigue/creep fatigue tester 10 drives a load adding member 12 through a servo valve to repetitively apply a load to a test piece 14. Tension and compression load to the tester is instructed from a fatigue/creep fatigue test controller 21 to which an instruction of load waveforms is applied from the program oscillator 20. Repetitive load to the test piece 14 is read by a load detector 13, while a strain of the test piece 14 is read by a strain gage 15 to be put into the controller 21. Control waveforms from the oscillator 20 are applied also to a test piece breakage detection circuit 22. When a predetermined ratio of a drop amount which is set from the load amount read from the controller 21 with respect to maximum peak load is detected, the detection circuit 22 outputs a direction for completing the test to the controller 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fatigue test piece breakage detecting device for carrying out material strength tests such as fatigue tests and creep fatigue tests.

[0002]

2. Description of the Related Art In axial strain control fatigue and creep fatigue tests of materials exhibiting repeated hardening behavior, such as stainless steel, generally, from the viewpoint of material strength evaluation, after the tensile load reaches the maximum load, It is defined as "rupture" when it falls by a certain percentage. This will be described with reference to FIGS. FIG. 3 is a conceptual diagram of the fatigue / creep-fatigue test.
The load is repeatedly applied within εt. The control waveform at this time is
For example, as shown in FIG. 4A, the strain repeatedly changes in a triangular wave pattern within Δεt, and the load behavior at this time has a waveform as shown in FIG. 4B. Also, FIG.
As shown in FIGS. 5A and 5B, a control waveform that keeps the maximum strain constant may be used, and the load behavior in this case is a waveform as shown in FIG. 5B.

FIG. 6 shows the relationship between the tensile load value and the number of cycles in each cycle. The definition of "breakage" of a material exhibiting repeated hardening behavior, such as stainless steel, is defined in terms of material strength evaluation. Therefore, the point at which a certain amount, generally 25%, is decreased with respect to the maximum value of the peak load on the tensile side is defined as “break”.

[0004]

In the conventional test piece breakage detection circuit, the person in charge of the test finds the maximum load value on the tensile side each time from the repeated load behavior recording paper (analog data) obtained during the test. The breaking load, which decreases by a certain amount from the value, had to be manually input to the detection circuit. That is, as shown in FIG. 7, the tension side maximum load value (P'max) at that time is read from the repeated load behavior recording paper, and a temporary breaking load is set. This is because when the constant decrease amount is 25%, the temporary breaking load = P'max × 0.
Set as 75. Then, the setting is reset each time (at least once a day) until the actual maximum tensile load value appears.
As described above, the work time involved in setting the breaking load to be corrected each time is long, and there is a problem that the setting must be reset at least once a day for several months if the test time is long.

Further, in the case of a short time (several days) test, as shown in FIG. 8, the maximum load on the tensile side may be exerted during a weekend (holiday), which may lead to breakage. The test is terminated with the repeated breakage number N'by the temporary breakage load L'set on the previous day, while the true breakage load L has the repeated breakage number N, and comparing both, N '> Since this is N, a repeated load is applied in excess of the actual number of ruptures, which causes the trouble of having to calculate the number of repeated ruptures reaching the rupture load from the repeated load behavior recording paper.

The present invention is to solve the above-mentioned problems, and automates the calculation and setting of the load corresponding to the fracture,
An object of the present invention is to provide a fatigue test piece rupture detection device capable of saving labor in rupture detection work and preventing occurrence of human error in setting rupture load.

[0007]

SUMMARY OF THE INVENTION A fatigue test piece breakage detecting apparatus of the present invention is a program oscillator for generating a load waveform, and a fatigue tester in which a test piece is set repeatedly according to a load waveform from the program oscillator. Detects a load value that is a prescribed amount lower than the maximum value of the load amount sent from the control device, as well as indicating a tensile load or a compressive load, and taking in the load amount and strain amount from the load detector and strain gauge. And a detection circuit for detecting the maximum load, the detection circuit instructs the control device to end the test at the time of detecting a load value reduced by a predetermined ratio with respect to the maximum load value. To do.

[0008]

In the present invention, the maximum load during the test is recognized, and the arithmetic function for setting the breaking load reduced by a certain amount is incorporated therein. Therefore, the work required until the breaking load is set, There is no work required to calculate the number of repeated breaks, and labor can be saved.
It is possible to eliminate human error such as erroneous setting of breaking load.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of a detection device of the present invention, and FIG. 2 is a waveform diagram of strain and load. The fatigue / creep-fatigue testing machine 10 has a servo valve 11, through which a load applying member 12 is driven to repeatedly apply a load to a test piece 14. The tensile / compression load instruction to the testing machine is given from the fatigue / creep-fatigue test control device 21 to which the load waveform instruction is given from the program oscillator 20. The program oscillator 20 can set an arbitrary control waveform, and the control device 21 issues a load instruction to the tester 10 in accordance with the control waveform supplied from the program oscillator 20. Various tests can be performed. The repeated load on the test piece is read by the load detector 13, the strain of the test piece 14 is read by the strain gauge 15, and the read load amount and axial strain amount are taken into the control device 21.

The control waveform output from the program oscillator 20 is also given to the test piece breakage detection circuit 22, and the test piece breakage detection circuit 22 sets a predetermined ratio to the maximum peak load from the read load amount given from the control device 21. When the decrease amount of is detected, an instruction to end the test is given to the control device. The test piece breakage detection circuit 2
The setting reduction amount for the maximum peak load in 2 is 0 to 1
A value of 00% can be set freely.

In such a fatigue test piece rupture detection device, for example, when the control waveform and load behavior as shown in FIGS. 2 (a) and 2 (b) are exhibited, the maximum load value on the tensile side is detected by the load detector 13. Recognize and, for example, the set reduction amount is 2 of the maximum load value.
In the case of 5%, as shown in FIG. 2 (b), a load value that is 25% lower than the maximum load value is recognized as a breaking load at point a, the test machine automatically stops, and the test ends. It will be. In the above description, the case where a tensile load is used has been described, but it goes without saying that the present invention can be applied to a compressive load in exactly the same manner.

[0012]

As described above, according to the present invention, the work required to set the breaking load, the work required to calculate the number of repeated breaks, etc. are unnecessary, and the load calculation and setting can be automated. Labor can be saved, and human errors such as mistakes in setting the breaking load can be eliminated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a detection device of the present invention.

FIG. 2 is a waveform diagram of strain and load.

FIG. 3 is a conceptual diagram of a fatigue / creep fatigue test.

FIG. 4 is a diagram showing an example of a control waveform.

FIG. 5 is a diagram showing an example of control waveforms.

FIG. 6 is a diagram showing the relationship between the tensile load value and the number of repetitions in each cycle.

FIG. 7 is a diagram showing a conventional breaking load setting method.

FIG. 8 is a diagram illustrating the number of surplus repetitions.

[Explanation of symbols]

10 ... Fatigue / creep fatigue tester, 11 ... Servo valve, 1
2 ... load applying member, 13 ... load detector, 14 ... test piece,
15 ... Strain gauge, 20 ... Program oscillator, 21 ... Fatigue / creep-fatigue test control device, 22 ... Test piece breakage detection circuit.

Claims (3)

[Claims] 1. A program oscillator for generating a load waveform, and a fatigue tester in which a test piece is set, repeatedly instructing a tensile load or a compressive load according to a load waveform from the program oscillator, and a load detector and strain. A control device that takes in a load amount and a strain amount from the meter, and a detection circuit for detecting a load value that is reduced by a predetermined amount with respect to the maximum value of the load amount sent from the control device, and the detection circuit is a maximum load After the recognition, the fatigue test piece breakage detecting device is characterized in instructing the control device to end the test when a load value reduced by a predetermined ratio with respect to the maximum load value is detected. 2. The fatigue test piece rupture detection device according to claim 1, wherein the detection circuit is capable of setting the predetermined ratio within a range of 0 to 100% of a maximum load. 3. The fatigue test piece fracture detection device according to claim 1, wherein the program oscillator is capable of generating an arbitrary load waveform.