JPH0321847A - fatigue testing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] A. INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to a fatigue testing machine in which the combination of frequency and amplitude of repeated loads in a fatigue test is limited by the capacity of a hydraulic power source.

B. Conventional technology In this type of fatigue testing machine, a load pattern waveform is set by the load average value, amplitude, and frequency of repeated loads, and the load applied to the test piece is fed back to form a load pattern waveform. The test is conducted under load. Normally, this type of fatigue testing machine uses a hydraulic cylinder that is operated by pressure oil supplied from a hydraulic source.
The test conditions are limited by the above combination of amplitude and frequency based on the capacity of the hydraulic source (for example, discharge capacity). FIG. 3 is an amplitude characteristic diagram of the hydraulic power source, and the test can be performed within the range surrounded by the solid line SL, the horizontal axis, and the vertical axis.

C. Problems to be Solved by the Invention However, if the rigidity of the test piece TP decreases due to fatigue and the amplitude of the load actuator becomes larger than the initial value, there is a risk that the amplitude will deviate from the range shown in FIG. Therefore, conventionally, deviation from this range is detected and an alarm is issued.

However, fatigue tests generally take a long time, and operators do not constantly monitor the testing machine.

Therefore, if the test conditions are not changed manually when the alarm is issued, the testing machine will automatically stop, and the test piece TP that was subjected to the fatigue test over a long period of time will be wasted. A technical object of the present invention is to automatically continue the fatigue test even when the amplitude exceeds the range defined by the amplitude characteristic diagram of the hydraulic power source.

D. To explain with reference to FIG. 1 showing an embodiment of means for solving the problem, the fatigue testing machine according to the present invention includes a waveform generation circuit 10 that outputs a load pattern waveform of a predetermined frequency for repeatedly loading a test piece;
A hydraulic actuator 21 that is excited and loads the test piece based on this load pattern waveform, a hydraulic power source 22 for this actuator 21, a load detection means 13 that detects the load acting on the test piece, and a oscillation control means 16.19 for oscillating the actuator 21 so that the test specimen is loaded with the fed-back load pattern waveform;
During this feedback control, when the momentum of the actuator 21 increases as the rigidity of the test piece decreases, the hydraulic source 22
A determining means 12 determines whether or not the capacity exceeds the capacity of the waveform. The above technical problem is solved by including the frequency changing means 12 that reduces the frequency of the waveform output by the device 111 so as to avoid overcapacity.

E. For example, the limit curve S of the amplitude characteristic diagram of the hydraulic power source shown in FIG.
A fatigue test is performed using a load pattern waveform with a frequency and amplitude inside L. When the rigidity of the test piece decreases as a result of the fatigue test, the amount of momentum (amplitude) of the actuator 21 increases in order to deliver a load commensurate with the load pattern. the result,
The intersection point between the frequency and the amplitude is about to deviate from the limit curve SL, but when this is determined by the determining means 2, the frequency of the waveform output from the waveform generating circuit 10 is returned to a value within the range of the limit curve SL. It will be set. This automatically continues the fatigue test.

In the above sections D and E explaining the structure of the present invention, figures of embodiments are used to make the present invention easier to understand, but the present invention is not limited to the embodiments. F. Embodiment FIG. 1 is a block diagram showing the overall structure of a fatigue testing machine according to the present invention. Reference numeral 10 denotes a waveform generating circuit, which outputs a load pattern such as a sine waveform or a ramp waveform determined by the average load value, amplitude, and frequency manually inputted from the operating section l1. FIG. 4 shows an example of a sinusoidal waveform load pattern.

l2 is. This is a well-known microcomputer consisting of a CPU, ROM, RAM, etc., and the ROM stores the amplitude characteristic diagram of the hydraulic power source shown in FIG. That is, the limit curve SL and the recommended curve DL inside the limit curve SL are stored. 13 is a load cell that detects the load acting on the test piece, and 14 is a load actuator 2 that loads the test piece.
This is a displacement meter that detects one stroke. 15 is a load amplifier that amplifies the output signal of the load cell 13, and 16 is a deviation device that takes the deviation between the load pattern waveform signal output from the waveform generation circuit 10 and the actual load waveform signal output from the load amplifier 15. .

17 is a forward gain setter that multiplies the output signal of the deviation device 16 by a gain, and 18 is a servo amplifier that amplifies the output signal and supplies a time motion signal to the servo valves 1-9 of the actuator 21. 20 is a stroke amplifier that amplifies the output signal of the displacement meter 14, and 22 is a hydraulic pressure source for the actuator.

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG.

In step Sl, it is determined whether the test currently being performed is within the range of automatic gain control (hereinafter referred to as AGC) of the servo amplifier 18, and if it is within the range, the test is continued as is. When it deviates from the AGC range, the process proceeds to step S2, and it is determined whether the test piece is broken by detecting the maximum actual load or the minimum actual load. If affirmative, the test ends in step S9. If step S2 is negative, the process proceeds to step S3, where it is determined whether the test is over. This can be determined, for example, by monitoring the amount of strain in the test piece and determining whether it exceeds a predetermined value.

If affirmative, the test ends in step S9, and if negative, the signal from the stroke amplifier 20 is taken in in step S4, and the current amplitude of the actuator is determined. Next, in step S5, the current frequency is read, and in step S6
Proceed to.

In step S6, it is determined whether the intersection of the read amplitude and frequency is within the limit curve SI in FIG. If the answer is affirmative, the process directly returns to step S1, and if the answer is negative, the process proceeds to step S7.

In step S7, the frequency is determined from the recommended curve DL in FIG. 3 using the read amplitude, and step S8
Then, change the oscillation frequency of the waveform generating circuit {1 to the obtained frequency and return to step S↓.

According to such a procedure, the stiffness of the test piece decreases due to the fatigue test, and in order to apply the same load, the actuator 2
When the amplitude of 1 increases, the intersection of the amplitude and the frequency becomes the third
When the amplitude characteristic of the hydraulic power source shown in the figure deviates from the range of the limit curve SL, a predetermined recommended curve DL is used to automatically set a frequency that matches the capacity of the hydraulic power source with respect to the current amplitude. The test continues. Therefore, even when there is no operator present, such as at night, the testing machine automatically changes the test conditions and continues the fatigue test, eliminating the possibility of wasting a test piece that has been partially subjected to a fatigue test, improving test efficiency. do.

Note that the frequency may be changed not based on the recommended curve DL, but instead a value that is within a certain percentage of the limit curve ST may be selected.

G. Effects of the Invention Since the present invention is constructed as described above, when the capacity of the hydraulic power source becomes insufficient due to the rigidity of the test piece, the frequency of repeated loading is automatically reduced to avoid overcapacity, thereby reducing fatigue. Testing continues and testing efficiency improves.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall structure of the fatigue testing machine according to the present invention, Fig. 2 is a flowchart showing the procedure for changing the frequency, Fig. 3 is an amplitude characteristic diagram of the hydraulic power source, and Fig. 4 is a load pattern. It is a figure showing an example.

Claims (1)

[Claims] A waveform generation circuit that outputs a load pattern waveform of a predetermined frequency for repeatedly loading a test piece, a hydraulic actuator that is excited based on this load pattern waveform and loads the test piece, a hydraulic power source for this actuator, and the test piece. load detection means for detecting the load acting on the specimen; drive control means for feeding back the detected load and driving the actuator so that the test specimen is loaded with the load pattern waveform; determining means for determining whether or not the capacity of the hydraulic source exceeds when the momentum of the actuator increases as the rigidity of the actuator decreases; and when the determining means detects that the capacity exceeds the capacity, the waveform generating circuit outputs an output. and a frequency changing means for reducing the frequency of the waveform so as to avoid the capacity overflow.