SU855491A1 - Device for acoustic emission signal detection - Google Patents

Description

The invention relates to non-destructive testing and can be used to control the quality of materials and products. from

A device is known for detecting acoustic emission signals, comprising a transducer, an amplifier driver, an intimesimeter, a pulse counter, and a recorder G1]. Θ

The closest in technical ^'υ is the essence of the proposed device for detecting' the acoustic emission signals, comprising series-connected converter, amplifier, filter and shaper block threshold, and the indicator register [2].

The disadvantage of these devices is that with their help it is impossible to detect weak acoustic emission signals, comparable to the intrinsic noise of the equipment.

The purpose of the invention is the detection of signals at the level of intrinsic noise of the equipment.

This goal is achieved due to the fact that the device is equipped with a pulse generator, a delay line connected to it with η taps, η coincidence circuits connected to η 30 delay line taps, η pulse counters connected to the coincidence circuit outputs, a switching circuit connected to the outputs of the counters · impul'ds, clock generators connected to the second input of the switching circuit, the output of which is connected to the unit for setting the registration threshold, and the number η is selected from the relation:

'·. T where T is the period of natural vibrations of the Converter;

- the duration of the pulses at the output of the shaper.

In the drawing, a block diagram of a device.

The device comprises a converter 1, an amplifier 2, a filter 3, a pulse shaper 4, a pulse generator 5, a delay line b, η coincidence circuits 7, η pulse counters 8, a switching circuit 9, a clock 10, a registration threshold setting unit 11, and an indicator 12.

The device operates as follows.

Converter 1 receives acoustic emission signals. The electric signal from the converter passes amplifier 2, filter 3, and driver 4, which generates pulses of duration J ·, at the moment when the input process has a positive derivative at the zero level crossing ^ these pulses arrive at the first input of coincidence circuit 7. Since the reaction of the converter /! Since acoustic emission signals are a periodic function with periodic zero crossing, then a periodic pulse sequence with a pulse duration equal to X and a period equal to the period of the response of converter 1 to the signals is used as a copy of the moments of crossing the zero level acoustic emission. Thus, to the second inputs of the coincidence circuit 7 from the 5 pulse generator 20, a periodic pulse is supplied through the delay line 6, which imitates the moments of crossing the zero level by the response of the converter to acoustic emission signals.

A comparison in the coincidence circuits 7 of the pulses generated by the pulse shaper 4 with the pulse sequences taken from the taps of the delay line 6 relative to each other is performed to eliminate the omission of acoustic emission signals due to the random nature of their appearance. In the delay line 6, the pulse sequence is delayed from the taps by the tap by an amount equal to the pulse duration of the pulse ·; clear sequence. The number of pulse sequences n taken from the taps of the delay line b, and therefore the number of matching circuits 7 and pulse counters 8, is determined by the following equality;

t ^η = νγ

In coincidence circuits 7, pulses are generated when the pulses are combined, pulses are given on the counters by a clock ____________ by the power of the cord-switching circuits ”9 received at their input, and 8 pulses counters. 8 pulses are counted in the time determined by the generator 10. From 1 started by the clock generator 10, alternating connection of the 8 pulse counters to the block 11 for setting the registration threshold and the installation of the 8 pulse counters in the initial position is performed. In block 11, the registration threshold is set. A comparison of the readings of 8 pulse counters with a given threshold is made and signals are generated about the presence or absence of acoustic emission signals in the input process. The signals from block 11 are fed to an indicator device 12, which can be used as a recorder or any other recording device.

Claims (2)

(54) DEVICE FOR DETECTION OF ACOUSTIC EMISSION SIGNALS 1. The resolution refers to non-destructive testing and can be used to control the quality of materials and products. A device for detecting acoustic emission signals is known, which comprises a transducer, a shaper amplifier, an intismimeter, a pulse counter, and a Tlj recorder. Nearby to the technical essence of the present invention is a device for detecting T acoustic emission signals comprising in series connected pre-converter, amplifier, filter and driver, installation unit thresholds of registration and indicator 2. The disadvantage of these devices is that with their help it is impossible to detect weak acoustic emission signals comparable to the intrinsic noise of the gparatura. The purpose of the invention is to detect signals at the level of the intrinsic noise of the gparatura. This goal is achieved due to the fact that the device is equipped with a pulse generator, connected to it a delay line with n taps, n coincidence circuits connected to n taps of the rod line, n pulse counters connected to the outputs of the coincidence circuit, a switching circuit connected to the outputs of the counters - impulses, a clock generator connected to the second input of the switching circuit, the output of which is connected to the registration threshold setting block, and the number n selected from the relation:. T- where T is the period of natural oscillations of the converter; C is the pulse duration at the output of the ate forms. The drawing shows the block diagram of the device. The device contains a converter 1, an amplifier 2, a filter 3, a pulse shaper 4, a pulse generator, a delay line 6, n coincidence circuits 7, 8 pulse counters 8, a switching circuit 9, a clock generator 10, a registration threshold setting unit 11 and an indicator 12. The device works as follows. Transducer 1 receives acoustic emission signals. The electrical signal from the converter pierces the amplifier 2, the filter 3, and the driver 4, which generates pulses of duration C J-, at the moment when the input process has a zero level crossing, the positive pulse has passed through the water and these pulses arrive at the first input of circuit 7 of coincidence. Since the reaction transducer ffSL signals of the acoustic emission is a periodic function with a periodic zero-crossing, then as a copy of the moments of zero crossings reaction transducer 1 on acoustic emission signs1ly isprlzuets periodic eska pulse sequence of a pulse width ravnoyT, and a period equal periodureaktsii transducer 1 on acoustic emission signals. Thus, the second inputs of circuit 7 coincident with generator 5 of pulses are fed through a line b for cores to a sequence imitating the zero-crossing times by the response of the transducer to acoustic emission signals. Comparison in the circuits 7 of the pulses produced by the shaping of the 4 pulses with a number of pulse sequences / shots relative to each other from the taps of the delay line 6 is made to eliminate the passage of acoustic emission signals due to a random nature and occurrence. In line 6, the pulse per sequence delayed from the tap to the tap by an amount equal to the pulse duration of the pulse sequence. The number of pulse sequences p removed from the taps of the delay line b, and therefore also the number of coincidence circuits 7 and pulse counters 8 is determined by the following equation: In coincidence circuits 7, pulses are generated when the impulses arriving at their inputs are matched and output to counters 8 impulses. In impulse counters B, impulses are counted for a time that is determined by the clock generator 10. With the help of the "muting circuit 9, triggered by the clock generator 10, the counters 8 impulses are connected to block 11, establishing the detection threshold and setting pulse counter 8 to the initial position. In block 11, the establishment of the threshold for registration is made by comparing the readings of the counters of 8 pulses with a predetermined threshold and signals are generated about the presence or absence of acoustic emission signals in the input process. The signals from block 11 are sent to the indicator device 12, which can be used as a recorder or any other recording device. Apparatus for detecting acoustic emission signals, comprising a serially connected transducer, amplifier, filter and shaper, a recording threshold setting unit and an indicator, characterized in that, in order to detect signals at the level of corresponding noise of the apparatus, it is equipped with a pulse generator connected to it delay line with n taps, n coincidence circuits, connected to n taps of the delay line, n pulse counters, connected to the outputs of the coincidence circuits, comm A switching circuit connected to the outputs of the pulse counters by a clock generator connected to the second input of the switching circuit, whose output is connected to the registration threshold setting block, and the number n is chosen from the relation where T is the period of natural oscillations of the converter, pulse duration at the output of the imager. Sources of information taken into account in the examination 1. US Patent 3545262, cl. G 01 W 28/04, .1970. i 2. Brazhnikov V.A., Drobot Yu.B. Acoustic emission. M., Publishing house of standards, 1976, P.219221 (prototype).