SU1490632A1 - Device for measuring energy of acoustic emission - Google Patents

Abstract

The invention relates to non-destructive testing of materials and products by the method of acoustic emission and can be used to control engineering and other industries. The purpose of the invention is to increase the reliability due to the spacing in time of the counting pulses in the channels. The received signal is amplified by amplifier 2 and fed to amplitude discriminators 3, 4 and 5 in each channel. The levels of discrimination allow one to form rectangular pulses filled with counting pulses from generators 9, 10 and 11. The frequency of filling is selected depending on the step of the levels of discrimination. The sum of the received pulses corresponds to the energy of the acoustic emission signal and is proportional to the sum of the square and rectangles under the envelope of this signal. 3 il.

Description

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

The purpose of the invention is to increase the reliability of measurements due to the time difference of the counting pulses in the channels.

1 shows a block diagram of the device in the three-channel version; figure 2 - timing charts of the device at various points in the circuit; FIG. 3 is a graph of the energy measurement process.

The device contains (figure 1) serially connected receiving transducer 1 and amplifier 2, amplitude discriminators 3, 4 and 5,

one-shot 6, 7 and 8 with a restart, the generators 9, Yu and 11 pulses, the elements And 12, 13 and 14, serially connected logical element OR 15, the counter 16 and the recorder 17; the inputs of amplitude discriminators 3, 4 and 5 are combined and connected to the output of the amplifier. 2, in each channel the input of the one-shot 6, 7 or 8 is connected to the output amplitude. discriminator 3, 4 or 5, the first input of the logic element And is connected to the direct output of the one-vibrator, the second input of the logic element And is connected to the output of the pulse generator, the third input of the logic element And 13, 14 is connected to the inverse output of the single-oscillator 6, 7 of the adjacent oldest previous channel. The outputs of the logic gates AND are connected to the corresponding t and the inputs of the logical element OR.

four; with

about

about: with tc

The device works as follows.

Acoustic emission signals are received by receiver transducer 1 and converted to electrical signals. The electrical signals are amplified by amplifier 2 and fed to the inputs of amplitude discriminators 3, 4 and 5 (see Fig. 2a). The discrimination levels of amplitude discriminators are chosen in such a way as to ensure the measurement of the energy of acoustic emission signals with a minimum error within the required dynamic range. In Fig. 2a, the discrimination levels of amplitude discriminators 5, 4, 3 are depicted as, and, Ug. Restarting single-oscillators in this device play the role of digital detectors. A burst of impulses arriving at the input of a single vibrator is converted at its output into a single-square pulse, the duration of which COOT- corresponds to the duration of the burst of impulses received at the input. This is due to the fact that the time constant of the single vibrators is chosen at a slightly longer pulse period in the packet. In this case, a constant charging time of the single-vibrator driving capacitance is carried out and the output impulse is continuous. This solution made it possible to do without analog detection and filtering, which inevitably narrows the dynamic range and bandwidth of the device. In addition, the problem of combating bounce on arising output pulses of amplitude discriminators 3, A and 5 is solved. and 8, are depicted in the time diagrams of fig. 2b, c, d.

Logic elements And 12, 13 and 14 pass to the output the pulses of the generator 9, 10 and 11 in their channel during the time interval when the input signal level exceeds the discrimination level of the amplitude discriminator of its channel, but does not exceed the discrimination level of the adjacent older channel. The signals generated at the outputs of logic gates And 14, 13 and 12, are depicted in the time diagrams of fig.2d, e, g. Next, the estimated pulses from all channels pass through the logical

the element OR 15 and is summed up in the counter 16. The registrar 17 records the accumulated amount at fixed intervals. The tuning frequencies of the pulse generators are determined according to the expression

g 2 Ui 2

where u is;

and

 + 1

the discrimination level of the amplitude discriminator of the i-rp channel; the discrimination level of the amplitude discriminator of the adjacent older channel;

C is a constant that determines the scale of the conversion. The process of measuring energy is as follows (Fig. 3).

The device determines the area under the conventional curve corresponding to the square of the envelope of the input signal. On fig.Z marked:

and - signal at the input of amplitude discriminators;

and.

- conditional obybakmtsa input

th signal;

and - the square of the conditional envelope of the input signal;

and, - and, - discrimination levels of amplitude discriminators;

uj is the conditional level of discrimination selected to calculate the frequency of the high-frequency pulse generator;

t, - tg - time points corresponding to the intersection of the input levels of discrimination.

The area under the curve U, proportional to the energy of the input signal, is determined in the proposed device as the sum of the areas of rectangles A, B, C, D, E. The area of each of them is equal to

Si

fi At ;;

g C

the frequency of the pulse generator i-ro channel;

 (t ;, - t ;; is the interval of time during which the generator pulses of the i-ro channel are passed to the input of the summation circuit.

at any time, the counting pulses arrive at the logical element OR through only one channel. This completely eliminates the possibility of overlap, allows you to increase the frequency of filling, increase the number of levels of discrimination. The introduction of a tunable pulse generator in each channel allows setting any values of discrimination levels. A positive effect can be considered as a simplification of the circuit of the device in comparison with the prototype, which led to a decrease in power consumption and a decrease in size.

Claims (1)

Invention Formula A device for measuring the energy of an acoustic emission signal containing series-connected 14906326 receive receiver and power0 five 0 the OR element, the counter and the recorder, n channels connected in parallel between the output of the amplifier and the inputs of the OR element, each of which contains an amplitude discriminator and an element AND, the input and output of which are respectively the input and output of the channel, characterized in that In order to increase reliability, each of the channels is made with a pulse generator connected to the first input of the element I, and with a single-shot with repeated start connected between the output of the amplitude discriminator and the second input of the element And, the third input of orogo connected to the inverted output of one-novibratora predduschego channel. Fi.g  B lib