SU531058A1 - Device for controlling the destruction of the sample - Google Patents

Description

one

The invention relates to testing equipment, in particular, devices for monitoring the destruction of a sample during software fatigue testing with self-oscillations.

A device is known for controlling the destruction of a sample in self-oscillating loading systems, which contains an electromechanical vibrator, into the excitation winding of which an alternating voltage is applied, having a frequency of excited loads and allowing to judge the change in the resonant frequency and the beginning of the destruction of the sample, a relay whose switch circuit closes the vibrator rod, tuned to a frequency lower than the driving frequency

A disadvantage of this device is that it tunes to a frequency lower than that which corresponds to oscillations with a maximum amplitude provided by the program, with a certain error.

It is also known a device for monitoring the destruction of a specimen during software fatigue tests with self-oscillations,

containing a control unit, an input driver and a generator of counting pulses, the outputs of which are connected to the control unit, and an output unit, whose input is connected to the control unit 2, the known device registers the period of pulses passed through the exciter of the testing machine and generates a signal to turn it off when increase the period to a value corresponding to the fatigue damage of the specimen.

This device is closest to the proposed invention in its technical essence and the achieved effect.

A disadvantage of this device is that it does not take into account changes in the electromechanical coupling coefficient of the transducer of the testing machine, depending on the magnitude of the excitation current during the test, which reduces the accuracy of the control of the destruction of the sample.

Claims (1)

The purpose of the invention is to improve the accuracy of determining the moment of generation of fatigue crack in a sample. This is achieved by the fact that the proposed device is equipped with a successively connected memory counter, rewrite unit and adder, the inputs of which are connected to the control unit, and the output of the adder - with the output unit. The drawing shows a block diagram of the proposed device. The device contains a control unit 1, its input is connected to a software unit (not shown), an input signal conditioner 2 and a generator of 3 counting pulses, the outputs of which are connected to the control unit 1 & laziness, connected in series by the memory counter 4, rewriting unit 5, adder 6 and output unit 7, the outputs of which are connected to control unit 1. The device works as follows. After switching on the test facility, after some time sufficient to exit the self-oscillating system to a stable mode of oscillation, the signal from the program block turns on the proposed device. In this case, the signal from the driver, the passage through the driver 2 of the input signal, enters the control unit 1, where one period of oscillation of the moving part of the test set is selected, filling it with counting pulses from the generator 3 counting pulses and writing the number code to the memory counter 4. The number of memory counters is determined by the number of loads of the program. Upon completion of the recording in block 1 of control, a command is generated to analyze the state of output block 7, and since at this stage in adder 6 there is no information about the oscillation frequency of the moving part of the setup, there is no signal indicating a change in frequency from output block 7. By the next command from control unit 1, block 5 rewrites the information contained in memory counter 4 in adder 6. Then control block 1 selects the next oscillation period, filling it with counting pulses, which are read in adder 6, at the same time, in the adder, the code of the number rewritten from the memory counter 4 is added to the number code corresponding to the oscillation period of the moving part of the installation at the moment of filling the extracted period with the counting pulses. After that, the command for analyzing the state of the output block 7 is formed again, taking into account the state of the adder 6, and the output block gives a conclusion about the equality or inequality of the compared oscillation frequencies. The same sequence is also observed when working on other load stages with the only difference that the adder 6 rewrites the information contained in the corresponding memory counter. The device allows for each loading amplitude to follow in the course of the test the change in frequency, indicating the initiation of a fatigue crack in the test specimen. Apparatus of the Invention A device for monitoring sample destruction in software fatigue tests with self-oscillations, comprising a control unit, an input driver and a counting pulse generator, whose outputs are connected to a control unit, and an output unit, whose input is connected to a control unit, characterized in that , in order to improve the accuracy of determining the moment of inception of a fatigue crack in a sample, it is equipped with a series-connected memory counter, rewrite unit and adder, the inputs of which These are connected to the control unit, and the output of the adder is connected to the output unit. Sources of information taken into account in the examination: 1, Litvak V, I. Automation of fatigue tests of full-scale structures, 1972, p. 157. 2, Litvak V, I. Automation of fatigue tests of full-scale structures, 1972, p. 343-344. From software SJIOKU From SosSydu iriean wobble