SU1413519A1 - Apparatus for measuring the energy of acoustic emission signals - Google Patents

Abstract

The invention relates to the non-destructive control of materials and products by the method of acoustic emission and can be used in various industrial areas. The purpose of the invention is to improve the accuracy of energy measurement due to the approximation of the area above the conventional curve corresponding to the square of the signal under study, the sum of the areas of the trapezium. Acoustic emission signals are received from the monitored product and processed in n conversion channels by amplitude discrimination and conversion to the number of counts. The output signals of the pulse transducer time 13–16 approximating the area under the curve of the acoustic emission signal with the area of the trapezium sum are multiplied using frequency dividers 17–20 by a factor proportional to the square of the acoustic emission signal values, and then summed and fed to the recorder 6. 2 Il. i WITH

Description

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The invention relates to the non-destructive testing of materials and products by the method of acoustic emission and can be used to control engineering, building industry and other industrial areas.

The aim of the invention is to improve the accuracy of energy measurement due to the approximation of the area under the conditional curve corresponding to the square of the signal under study, the sum of the areas of the trapezium.

1 shows a block diagram of the device in a four-channel version; Fig. 2 is a graph of the energy measurement process. :

The device contains a serially connected receiving transducer 1, an amplifier 2, a detector 3, a serially connected logical element OR 4 counter 5 and a recorder 6, connected in series a generator of 7 counting pulses and a distributor of 8 counting pulses, n channels, each of which contains series-connected amplitudes - the discriminator 9 (10-12), time - the pulse converter 13 (14-16) and the divider 17 (18-20) frequency, the output of which is connected to the corresponding input of the OR element.

The time pulse converter of the n-th channel is made as an element 21 AND connected between the output of the amplitude discriminator connected with the second input of the first element AND of the (n-l) -ro channel and the input of the frequency divider 17. Time pulse converters 14-16 are made in series-connected element 22 (23, 24) AND, element 25 (26, 27) OR - "element 28 (29, 30) AND, the output of which is the output of the corresponding time pulse converter The output of the amplitude discriminator 10 (11, 12) of each channel is connected to the first input of element 22 (23, 24) and the second input of element 28 (29, 30) of the same channel and to the second input of element 23 (24) And the previous channel.

The first output of the distributor 8 counting pulses is connected to the second input of the element 21 And, and the remaining outputs are connected respectively to the third input of the element 22 (23, 24) And

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 and the second input element 25 (26, 27) IL.

The device works as follows. Acoustic emission signals are received by receiver transducer 1 and converted by it into electrical signals. The latter are amplified by amplifier 2 and then converted by detector 3 into electrical signals of the same polarity. From the output of the detector 3, the signal enters in parallel to the inputs of amplitude discriminators 9-12. The discrimination levels of amplitude discriminators 9-12 are chosen different and such as to ensure the measurement of the energy of acoustic emission signals within the required dynamic range. At the outputs of amplitude discriminators 9-12, pulses are formed with a duration equal to the time during which the output signal of detector 3 exceeds the discrimination level of the corresponding amplitude discriminator 9-12. The generator 7 of counting pulses produces quantizing pulses of the same constant follow-up period. The distributor 8 counting pulses, having in this case 2p - 1 7 outputs, provides at its outputs a continuous sequence of quantizing pulses of the same period. These sequences of pulses are shifted in phase in such a way as to exclude their mutual overlapping at some time. The pulses from each output of the distributor 8 counted pulses are received either at the second input of element 21-24 and one of the channels, or at the second input of element 25-27 OR of one of the channels. If the signal from the output of the detector 3 exceeds the discrimination level of only the amplitude discriminator 12 of the first (lower) channel, then the output pulse of the amplitude discriminator 12 receives an opening pulse to the first input of element 24 I. Since the third input of element 24 And there is a prohibiting signal from the output of amplitude discriminator 11, then the pulses from one of the outputs of the distributor 8 of counting pulses, arriving at the second input of element 24 I, do not pass to the output of the latter. At the same time, pulses from another output of the distributor 8 counting pulses, arriving at the second

31

the input element 27 or, passes to the input of the second element 30 I. These pulses during the time the pulse at the output of the amplitude discriminator 12 passes through the second element 30 And to the input of the frequency divider 20. If the signal from the output of the detector 3 exceeds the level of discrimination and the amplitude discriminator 11 of the second: g-channel, then it starts working as before the first one worked. However, the first channel at the same time changes the mode of operation, since at the third input of the element 24, a signal appears from the output of the amplitude discriminator 11. At the same time, the pulses from the output of the distributor 8 counting pulses to the second input of the element 24 And pass to the output last and then to the first input of element 27 OR Thus, at the output of element 27 OR, we have the sum of pulses, after two different outputs of the distributor, 8 counting pulses, i.e. sequence of double frequency pulses. These pulses then through the element 30 and arrive at the input of the frequency divider 20.

All other channels work in a similar way, i.e. The inputs of the dividers 18–20 of the frequency of each i-ro channel receive pulses with a frequency f equal to twice the frequency of the pulses at one of the outputs of the distributor 8 counting pulses (if the after-channel works) or f - / 2 (if the subsequent channel does not work) ,

To the input of the divider 17 frequency receives pulses with a frequency of fj / 2.

Dividers 17–20 frequencies divide the number of pulses arriving at their inputs during the measurement in accordance with the division factors established in them.

The output pulses of dividers 17–20 frequencies are combined by element 4 OR, summed by counter 5 and recorded by the recorder 6. The division factors of dividers 17–20 are chosen so that the total number of pulses in counter 5 is proportional to the energy of the signal being analyzed.

The energy measurement process is as follows (Fig. 2).

In the device, the area under the conditional curve corresponding to the square of the signal under study is determined.

194

FIG. marked U - signal from the output of the detector 3; Ui conditional curve corresponding to the square of the signal from the output of the detector 3; U, -U4 discrimination levels of amplitude discriminators 12, 11, 10 and 9, respectively.

and it is set to slightly above the level of the noise. The area under the curve and, proportional to the energy of the signal under investigation, is defined in the proposed device as the sum of the areas of trapezoids A, B and C, and the trapezoid C for the oldest of the activated channels degenerates into a triangle. The area of each trapezium is equal to the sum of the areas of the rectangle and two triangles. If the base of each i-and trapezium is expressed in terms of the number of impulses M-; then the area of the trapezium is defined as

S, M ,,, -n 1 (M. - Mi ,,). (U ,,

- Uf),

and the area under the curve U will be equal to

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In each i-M channel, in the absence of a subsequent adjacent channel, the frequency f | by two, i.e. The number of pulses is 1/2 (Mj - M,.,), and if the next adjacent channel is triggered, the division into two stops and a number of pulses equal to M is produced.

Thus, in the proposed device, by introducing the distributor 8 counting pulses, guaranteed quantizing pulses are delivered in time. In addition, a more accurate measurement of the energy of the AE signal is provided by approximating the area under the conditional curve corresponding to the square of the signal under study by the sum of the trapezoid areas.

Formula inventions

A device for measuring the energy of acoustic emission signals, containing a series-connected receiving transducer, an amplifier and a detector, a series-connected element OR, a counter and a register-. torus, n channels, each of which contains series-connected

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the amplitude discriminator whose input is connected to the detector output, a time pulse converter and a frequency divider whose output is connected to the corresponding input for the element OR, and a counting pulse generator, characterized in that it is equipped with a counter distributor - pulses with the number of outputs 2п-1, whose input is connected with the output of the generator of counting pulses, the time pulse converter of each channel, except for the n-th one, is made in the form of successively connected first element And, element OR and the second element AND zyhots which is the output time of the pulse converter, the output of the amplitude discriminator of each

Editor E. Kopcha

Compiled by B. Lomakin.

Tehred A. Kravchuk Proofreader V. But ha

Order 3776/46

Circulation 847

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

the channel is connected to the first input of the first element AND, the second code of the second element of the same channel and the second input of the first element AND of the previous channel, the time pulse converter of the nth channel is made as an element connected between the output amplitude discriminator of the nth the channel associated with the second input of the first element And (nl) -ro channel, and the input of the frequency divider n-th channel, the first output of the distributor counting pulses connected to the second input element And the time pulse converter n-th channel, and the rest rows are respectively connected to third inputs of first AND gates and the second inputs of OR elements other channels.

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Claims (1)

Claim A device for measuring the energy of acoustic emission signals, containing a series-connected receiving transducer, amplifier and detector, series-connected OR element, counter and register—. torus, n channels, each of which contains a series-connected amplitude discriminator, the input of which is connected to the detector output, a time-pulse converter and a frequency divider, the output of which is connected to the corresponding input of the OR element., and a counting pulse generator, characterized in that, for the purpose of to improve accuracy, it is equipped with a counting pulse distributor jq pulses with the number of outputs 2p-1, the input of which is connected to the output of the counting pulse generator, the time-pulse converter of each channel, except for the ηth, In the form of series-connected the first element AND, the OR element and the second element AND, the output of which is the output of the time-pulse converter, the output of the amplitude discriminator of each channel 20 is connected to the first input of the first element And, the second input of the second element And of the same channel and the second input of the first of the And element of the previous channel, the time-pulse converter of the η-th channel is made in the form of the And element connected between the output of the amplitude discriminator of the η-th channel associated with the second input of the first element nth And (n-1) -th channel, and the input of the frequency divider of the nth channel, the first output of the counting pulse distributor is connected to the second input of the And element of the pulse-time converter of the η-th channel, and the remaining outputs are connected respectively to the third inputs of the first elements And and the second inputs of the elements OR the remaining channels.