SU1516966A1 - Device for determining direction of arrival of signals of acoustic emission - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to determine the direction of the arrival of acoustic signals to the place of their reception in sheet products. The purpose of the invention is to increase the reliability of determining the direction of arrival of acoustic emission signals by taking into account the attenuation of the acoustic signal. The device measures the arrival times of acoustic signals into two mutually perpendicular pairs of piezoelectric transducers located around the circumference, which are used to judge the direction of arrival of the acoustic signal. In each of the reception channels, the received signals are compared with two predetermined threshold levels selected with regard to the attenuation of the acoustic signal in the product material, which provides a more accurate determination of the moment of reception of the acoustic wave and increases the reliability of determining the direction of its arrival. 3 il.

Description

The invention relates to non-destructive testing and can be used to determine the direction of the arrival of acoustic signals to the place of their reception in sheet products.

The purpose of the invention is to increase the reliability of determining the direction of arrival of acoustic emission signals by taking into account the attenuation of the acoustic signal.

FIG. 1 is a functional diagram of the device for determining the direction of arrival of acoustic emission signals; FIG. 2, an arrangement of piezo transducers

on the object under study; 3 shows timing diagrams for the operation of the device.

The device contains four identical signal receiving channels, each of which consists of serially connected piezoelectric transducers 1 (2–4) and amplifier 5 (6–8), element I 9 (10–12) and common to all channels of the recorder 13.

In addition, the device contains, in each channel, connected to the output of amplifier 5 (6-8) sequentially connected threshold element 14 (15-17), trigger 18 (19-2 G, and element OR 22 (23-25) and

SL

About CO 05

about:

the output of the amplifier 5 (6-8) connected in series is the second threshold element 26 (27-29) and the second three ger 30 (31-33), the output of which is connected to the element And 9 (10-12) of this channel, and the output of the latter - to the second input of the element OR 22 (23-25), serially connected element EXCLUSIVE IPI 34, the inputs of which are connected 1P 1 respectively to the outputs of elements OR 22 and 3 of the first and second channels, the second element 35 and counter 36, the output of which is under: CLU to the first input of the recorder 13, sequentially connected the second element EXCLUSIVE RSHI 37, the inputs of which oh are connected respectively to the outputs of the elements OR 2A and 25 of the third and fourth channels, the third element is AND 38 and the second counter 39 whose output is connected to the second input of the recorder 13, and the generator whose output is connected to the second inputs of the second 35 and third 38 elements AND, The outputs of the first triggers 18-21 of the first, second, third and fourth channels are connected respectively to the second inputs of the And 10,9,12 and 11 elements of the second, first, fourth and third channels, and the first, 36, and second inputs of the 39 counters and all triggers 18-21 and 30-33 combined (the reset inputs of the triggers are not shown) and are intended to give a signal that transforms the device to its original state.

Piezo transducers 1–4 are installed on a controlled product circumferentially with a diameter D so that pie transducers 1,2 and 3,4 form two mutually perpendicular pairs.

The device works as follows.

The AE signals are received by piezoelectric transducers 1–4. Let the LEs be the first to perceive the piezoelectric transducer 1. At the outputs of the piezoelectric transducers 1 and 2, electrical signals are received

and, DO sinw t i .f

U de and, u2

(.0

f

  sincjt

amplitudes of signals, respectively, at the output of piezoelectric transducers 1 and 2; circular frequency} damping factor.

0

five

0

five

45 menta

The AE signal received by the piezotransducer I is amplified by amplifier 5, the signal from the output of amplifier 5 is fed to the inputs of threshold elements 14 and 26, and the thresholds of each pair of threshold devices are set equal to U nopt o moment of equalization of the signal from the amplifier to the threshold of operation and „„, ( or II

pore 1

pore 2

0

five

0

0

five

one of

the threshold devices at the outputs of the latter appear right-angle pulses that set the triggers 18 and 30 in one state (Fig, 3, a, b, c, d), and the signal from the output of the trigger 18 through the element. OR 22, the EXCLUSIVE OR 34 element and AND 35 element allow the passage of rectangular pulses from the output of the master oscillator 40 to the counting input of the counter 36, which starts operation (FIG. 3, u, l, m), AE signal, propagated by design c damping, reaches the second piezoelectric transducer 2 of this diametral pair, is amplified by the amplifier 6, and is fed to the input of two threshold elements 15 and 27, which, when their response thresholds are equal to 1m amplified by the AE signal, set triggers 19 and 31 into a single state (FIG. 3 , 6, flte).

FIG. 3 shows the case when, due to attenuation, the AE signal did not exceed the trigger threshold P, .. At that, the signal from the output of the trigger 31 through AND 10 and OR 23 sets the EXCLUSIVE OR 34 element to the zero state (Fig. 3, 3 , k, l) and through the element AND .35 prohibits the passage of pulses from the output of the master oscillator 40, and the counting stops (Fig, 3, m). In this case, a zero potential is set at the output of Elea 9 (Le, 3, g). In this case, if the AE received the AE signal from the piezoelectric transducer 2, then everything happens in reverse order, and the AE signal on the second piezoelectric transducer 2 occurs at the level of the first — by P „opi — upon the arrival of the AE signal on the second diametric pair (piezoelectric transducer 3 and 4 in FIG. 1 and 2), the device operates in the same way as

In the proposed device, the time difference:, - the arrival of the AE signal corresponds to

5, 5

vetveitino on the first t.H second tj.4 diametrically located pairs of piezo transducers (figure 2) are respectively equal

R t,., G З1пс;

 3-4

Coso

where c / is the angle between the line connecting the diametral pairs of piezo transducers and the direction of arrival of the acoustic emission signal. Angle 0 between the line where

piezo transducers installed 1

and 2, and the direction of arrival of the signal

AE is defined as

about (arctg b-j

t-3-4

After the measurement results are recorded in the recorder 13, the counters 36 and 39 are reset, the triggers 18-21 and 30-33 are reset, and the device returns to the initial state. Information from the output of counters 36 and 39 about the differences in arrival times of the AE signal for pairs of piezo transducers is fed to the recorder 13. The direction of arrival of the AE signal is determined by the formula

, N,

with arctg -i

N

N and N

- binary codes from the outputs of counters 36 and 39, representing; time intervals

t 1. i and t 3-

The proposed device for determining the direction of arrival of the AE signal as compared with the known one has a higher accuracy of determining the direction of arrival of the AE signal. Despite the attenuation of the AE signal that has reached the second piezoelectric transducer of the diametral pair, it is fixed by the device. This eliminates errors in determining the direction of arrival of the AE signal and increases the accuracy of determining the direction to the AE source.

666

Claims (1)

Invention Formula A device for determining the direction of arrival of acoustic transmission signals, containing four identical channels for receiving signals, each of which consists of a series-connected piezoelectric transducer and amplifier, element I, and common for all channels of the recorder, piezoelectric transducers are installed on a circle at equal distances x and form two mutually perpendicular pairs, characterized in that, with the purpose of increasing the reliability of determining the direction of arrival of acoustic transmission signals, it is supplied in each channel connected to the output of the amplifier in series connected by a threshold element, a trigger and an OR element and connected to the output of the amplifier in series by a second threshold element and a second trigger, the output of which is connected to the AND element of this channel, and the output of the latter to the second input of the OR element, connected in series by the EXCLUSIVE OR element, whose inputs are connected respectively to the outputs of the OR elements of the first and second channels, the second AND element and the counter whose output is connected to the first input of the recorder, serially connected by the second element EXCLUSIVE OR, whose inputs are connected respectively to the outputs of the elements OR of the third and fourth channels, the third element AND and the second counter com, the output of which is connected to the second input of the recorder, and a generator, the output of which is connected to the second inputs of the second and third elements And, the outputs of the first triggers of the first, second, third and fourth channels are connected respectively to the second inputs of the elements And the second, first, fourth and third channels as well the reset inputs of the first and second counters and all of the flip-flops are combined and intended to give a signal that brings the device to its initial state. -. xS