SU1670589A1 - Method and apparatus for location of acoustic emission source in coordinates - Google Patents

Abstract

The invention relates to non-destructive testing and can be used in acoustic emission monitoring to determine the location of the source of acoustic emission signals (AE). The aim of the invention is to improve the accuracy of determining the coordinates and expanding the functionality by measuring the time intervals of propagation of AE signals between converters of diagonal pairs of each antenna at fixed points of the signal zero crossing and the possibility of determining both a discrete and continuous source of AE. To receive AE signals, two spatially separated antennas are used, each of which is made up of four transducers located at the vertices of the square. Introduction to the device of a signal detection unit with a trigger in each receiving channel and a quadrant of determining the arrival of the signal AE allows to fix the moments of the AE signal from zero from negative to positive, reject false combinations of the order of arrival of the AE signal to the transducers, determine the true priority , measure the time intervals of propagation of the AE signal between the converters of the diagonal pairs of each antenna on the recorded transition times, determine the angles n of the AE signal at the antennas and using the obtained values and the location of the antenna, calculate the coordinates of the AE source. 2 sp.f-ly, 8 ill.

Description

A3 using two antennas; in fig. 3 - time diagrams of the received AE signal from one of the antennas; in fig. 4 is a block diagram of the device; in fig. 5 is a functional block diagram of determining the quadrant of the arrival of the AE signal; in fig. 6 - functional diagram of the time interval meter; in fig. 7 - functional delay line circuit; in fig. 8 - timing diagrams for the operation of the device.

The device for determining the coordinates of the acoustic emission source (Fig. 4) contains two groups of blocks, each of which consists of four parallel channels including series-connected transducer 1 (2, 3, 4). amplifier 5 (6, 7, 8) and driver 9 (10, 11, 12), meter 13 time slots, serially connected OR 14 and delay lines 15, serially connected computing unit 16 and recorder 17, memory block 18. In each channel, the device contains a block 19 (20, 21, 22) for detecting a signal whose input is connected to the amplifier output, and a trigger 23 (24, 25, 26), whose synchronous input is connected to the output of the driver 9 (10, 11, 12), in each group of blocks, circuit 27 and block 28 for determining the quadrant of signal arrival, the first four inputs of which are connected to the corresponding inputs of the meter 13 time slots and the outputs of the trigger 23t26, the fifth input to the fifth meter input 13 time slots and the output of the delay line 15 , first output - to the second input of the 15 delay line, w swarm output - to the first input of OR gate 14. The inputs of AND gate 27 are connected to respective outputs 19-22 of the signal detecting unit, the output - to the data inputs of flip-flops 23-26. The second input of the OR circuit 14 is connected to the first output of the meter 13 timeslots, the output to the inputs Reset Triggers 23-26. The information inputs of the memory block 18 are connected to the corresponding second and third outputs of the meter 13 time slots and the third output of the block 28 determining the quadrant of the signal arrival of both groups of blocks, the inputs Record to the corresponding fourth outputs of the meter 13 time slots of each group of blocks, and the output to the computing one block 16.

The quadrant for determining the signal quadrant (Fig. 5) is made of four AND 29-32 circuits, an OR 33 circuit connected in series, and a register 34, the output of which is the third output of the block

28 determining the quadrant of the signal arrival, the circuit OR 35 and the serially connected circuit EXCLUDE 1EE OR 36. delay line 37, trigger 38 and driver

39 pulses, the output of which is connected to the first input of the OR circuit 33. The same inputs of the AND 29-32 circuits, the OR circuit 35 and the EXCLUSIVE OR circuit 36 are combined and are the first, second, third and

0 by the fourth inputs of the signal quadrant definition block 28, the outputs of the circuits AND 29-32 are connected to the corresponding information inputs of the register 34 and the second, third, fourth and fifth inputs

5 of the OR 33 circuit. The output of the OR circuit 35 and the forward output of the trigger 38 are the first and second outputs of the signal arrival quadrant 28. Input Reset register 34 is its fifth input.

0 The meter 13 time intervals (Fig. 6) is made of two groups of blocks, including serially connected circuit EXCLUSIVE OR 40 (41), circuit AND 42 (43) and counter 44 (45), the output of which is the second (third) output a meter 13 time slots, an AND 47 series-connected circuit, an AND 47 circuit, and an OR 48 circuit, the output of which is the first output of the meter 13

0 time intervals, the generator 49, the output of which is connected to the second inputs of circuits AND 42 and 43, and the imaging unit 50 pulses, the output of which is connected to the second input of the circuit OR 48. The second input of the circuit AND

5 47 is integrated with the Reset input of counter 44 and is the fifth input of the meter 13 timeslots. The inputs of circuit 46 and are combined with the corresponding inputs of circuits DROPPED OR 40 and 41 and are the first, second, third and fourth inputs of the meter 13 time intervals, the output of the circuit 46 is connected to the output of the pulse former 50 and is the fourth output of the meter 13 time5 intervals.

Line 15 of the delay is made of series-connected trigger 51, the S input of which is its second input, the AND circuit 52 and the counter 53 whose output

0 is the output of delay line 15, and generator 54, the output of which is connected to the second input of circuit AND 52. The reset inputs of trigger 51 and counter 53 are combined and are the first input of delay line 15.

5: Positions 55 to 64 denote yields.

signals from device blocks.

The method for determining the coordinates of the AE source is as follows.

AE signals generated by the source and propagated through controlled

the structures are adopted by two spatially separated antennas (Fig. 2), each of which is made of four transducers 1-4 located at the vertices of the square.

Consider the implementation of the method for the case when the source AE generates a continuous signal of frequency M / T, arriving at the antenna in the direction AB (Fig. 1). As the fixed points of the AE signal, the zero-crossing points are chosen, since this eliminates the measurement error of the time intervals caused by the spread of the conversion factors of the converters and the gain of the amplifiers. Timing diagrams for signal reception by transducers 1–4 for a given case are shown in FIG. 3. In this case, the points in time corresponding to the transition of the AE signal through zero from the negative region of its values to positive are indicated by the points A, C. C. D, A, B. C. D, A, B, C D and correspond to the true situation, Namely: the first receives the signal from the transducer 1, the second - the transducer 4, the third - the transducer 3, the fourth - the transducer 2.

However, there is the likelihood of a false combination corresponding to points C, D, A, c. C D A B (Fig. 3), which give a false direction A7B; the arrival of the AE signal (Fig, 1) at the antenna. Other false combinations, such as the direction of the LEDs (Fig. 1), can be rejected based on the order of reception of the AE signal by the antenna converters. To eliminate the possibility of a false combination, a restriction is introduced

G12 Tmax, (

where ri2 is the time interval between the moments when the AE signal is received by the converter, which received the signal first, and the converter, which received the signal last;

Tmax 1 / Cmin - maximum time; - propagation of the AE signal between converters of a diagonal antenna pair;

I is the distance between the transducers diagonally,

Cmin is the minimum speed of the ultrasonic wave in the test structure.

At the same time, the period of the received AE signal should correspond to the inequality of the form

C + T34,

where Gs4 is the time interval between the moments of receiving the AE signal by the converter, the second signal received, and the converter, the last signal received by the converter.

This condition limits the upper frequency of the processed AE signal at a given distance I between the transducers of diagonal pairs and the minimum ultrasound velocity in the test structure Depending on the direction of arrival of the AE signal, the time interval

/ 2

g may range from 0 to x-Tmax. what

corresponds to the angle of arrival of the AE signal a -45 °. Therefore, to satisfy condition (2), it is necessary to observe the inequality of the form

T T max (1 +). (3)

Since t - 1 - 1

I max

C min Cumin

Kingdom 3 is species I. 1 + 4F1-, then neral "in

(four)

For this tested design, the values of the minimum wavelength of the amine are determined from expression (4) of the required distance I between the converters of the diagonal pairs of the antenna. The constraints introduced (1) and (4) make it possible to clearly determine the order of reception of a given signal by antenna fecundators and to determine the arrival quadrant of the AE signal.

Using the measured values of the time intervals P2 and Gz4, the acute angles between the direction of arrival of the AE signal and the axis connecting the 3-4 and 3 4 converters (Fig. 2) are calculated from the relations:

«Arctgg | ;

/ arctg IM

(five)

Using the obtained angles, the relative position of the antennas and the distance between their centers, the coordinates of the AE source are calculated, which are located at the intersection point of the directions determined by the two receiving antennas.

The device works as follows.

The AE signals generated by the source propagate through the structure under test, reach the transducers 1-4 of both antennas, and are converted into electrical signals. The latter are fed to the inputs of amplifiers 5-8 of each channel, amplified, and then shapers 9-12 convert them into square pulses 55-58 (Fig. 8), the fronts of which correspond to the moments of the electrical signal crossing through zero, and the leading edge

the signals at the output of the formers 9–12 correspond to the moment of transition of the AE signal from the negative to the positive region, and the trailing edge - the moment of transition of the AE signal from the positive to the negative region.

The sequence of pulses from the formers 9–12 of each pump is continuously fed to the corresponding synchronous inputs of the triggers 23–26. At the same time, electrical signals from the outputs of amplifiers 5-8 of each channel are fed to the corresponding inputs of signal detection units 19-22. When the output signal of the amplifier exceeds the specified detection threshold, the output of the signal detection unit produces a signal arriving at the inputs of the circuit 27. At the output of the AE signal, the detection thresholds in all channels of this group output the circuit 27 and produce a signal that arrives at the information inputs of the flip-flops 23 -26, allows the device to work. The described operating situation for the AE signal coming from the second quadrant (the direction of the LED in Fig. 1) corresponds to the time ti (Fig. 8) when the output signal of the device’s operation comes from the output of circuit 27 And, the first signal is sensed by the first converter the second is the third transducer, the third is the fourth transducer, the last is the second transducer. At time t2 (Fig. 8), the trigger 25 of the third channel is set to one and the signal 61 from its output goes to the quadrant of determining the arrival of the AE signal. The output signal of the latter goes further to the delay line 15, which delays the signal by the time Tmax, which is necessary for specifying the arrival quadrant of the AE signal. In this case, it is assumed that the first to accept the AE signal is not the first converter, but the third one, and this version is further checked. Following the installation of the third channel trigger 25 at time t3, the fourth channel trigger 26 is set to one (Fig. 8, signal 62). From the output of the latter, the signal 62 is fed to the fourth input of the block 28 for determining the arrival quadrant of the signal AE. Since, following the third transducer, the AE signal cannot be received by the fourth transducer, but can be received by either the first or second transducers (Fig. 1), the signal arrival quadrant 28 determines the reset pulse 63, which through OR 14 arrives at resetting triggers 23-26 and stops the delay line 15. Thus, the assumption that the third transducer received the AE signal first is rejected. At time t4, the trigger 24 of the second channel is set to one.

The signal 60 from its output is fed to a block 28 for determining the arrival quadrant of the signal AE, which triggers the delay line 15. Lastly, after a period of time Tmchx, a signal 64 is generated, which is supplied

to the fifth inputs of the quadrant of determining the arrival of the AE signal and the meter, 13 time slots, reset them. Triggers 23-26 are reset and thereby reject the assumption that the second AE signal was received by the second transducer first. At time t5, the trigger 23 by the signal 55 from the output of the driver 9 of the first channel is set to one, the delay line 15 is started, and then at the times te, t and ta the triggers 25, 26 and 24 of the third, fourth and second channels are respectively set to one the Since the time between triggering the first 23

the channel that received the AE signal first, and triggering the trigger 24 of the second channel that received the AE signal last, is less than Tmax, and delay line 15 does not generate a reset signal. The unit 28 for determining the arrival quadrant of the AE signal in accordance with the sequence of the arrival of the signal AE on the antenna channels determines the quadrant of its arrival, and the 13 time slot meter measures the intervals

time t. Гз4 (Fig. 8), where, tsl are the time intervals of propagation of the AE signal between the transducers of the diagonal pairs of the first antenna in the lth dimension. Next from the output of blocks 28 and 13 code numbers

the quadrant of arrival of the AE signal and the codes of the corresponding time intervals are transmitted to the memory unit 18. After that (at time tg), the device returns to its initial state (triggers are reset

23-26 on all channels and the operation of the delay line 15 is prohibited). Next, the device waits for the arrival of the next oscillation period of the AE signal. The memory block 18 records the results of the n measurements.

Wire p measurements of the time intervals of propagation of AE signals between converters of diagonal pairs of antenna, you can specify the angle of arrival of the AE signal from the relation A

(2I h

about

szch

A1 b 1-2.

u

(6)

where a, ft are the acute angles between the direction of arrival of the signal A3 and the axis connecting the transducers 3-4 and 3-4 (Fig. 2);

tb tb are the time intervals of propagation of the AE signal between the diagonal pair transducers of the second antenna in the 1st dimension.

AE signals from the second antenna are processed similarly. The results of all measurements from the output of the memory block 18 are transferred to the computing unit 16, in which the calculation of the angles of arrival of the AE signal to the first and second antennas, as well as the calculation of the coordinates of the AE source, which are transmitted to the recorder 17.

The coordinates of the AE source are determined from the known mutual arrangement of the antennas and the calculated angles a and / 5. In this case, the latter is located at the intersection point of the directions determined by the two receiving antennas.

In the case of using the device to control discrete AE signals, the time of existence of the latter should correspond to several periods of the AE signal.

Block 28 determining the quadrant of the arrival of the signal AE works as follows (Fig. 5).

The quadrant number of the AE signal arrival is determined by the numbers of the two transducers that received the AE signal first. The signals from the flip-flops 23-26 of the respective measurement channels arrive at the inputs of the circuits AND 29-32, at the output of which the code of the number of the arrival quadrant of the AE signal is formed. The signal from the output of the circuit OR 33 records this code in register 34. On the circuit EXCLUSIVE OR 36, delay line 37, trigger 38, a blocking circuit is assembled to eliminate the false combination of the order of arrival of the AE signal on the measuring channels. On the second received signal coming from the measurement channels, the trigger 38 (via the SPARE scheme - AU-S OR 36, the delay line 37) is set to one. Through the OR 14 circuit, a signal is given to reset the flip-flops 23-26 and reset the delay line 15. If the order of arrival of the AE signal at the converters is true, then the output of one of the AND 29-32 circuits is a signal that through the OR 33 circuit is fed to the reset input of the trigger 38. The OR circuit 35 starts the delay line 15 (FIG. 5) which is produced on the first signal received from the output of the flip-flops 23-26.

FIG. 6 shows a functional diagram of a time interval meter. The signals from the output of the flip-flops 23-26 of the respective measurement channels are fed to the schemes EXCLUSIVE OR 40 and 41, from the output of which the signals have a duration equal to the time intervals G12. 34 propagation of the AE signal between the converters of diagonal pairs,

The pulses from the generator 49 are allowed to pass through the AND 42 and 43 circuits to the counting inputs of counters 44 and 45. From the output of the latter, the code equivalent of the time slots is transmitted to memory block 18. When

non-equality of sight

G12 Tmax

Smin

(i.e., when from the output of the line 15 the delayed signal arrived, and from the output of the trigger 23 (24-26)

no channel has been received), circuits And 46 and 47 reset the flip-flops 23-26 and the delay line 15

Line 15 of the delay (Fig. 7) consists of a trigger 51. set in unit

the state of the trigger signal from the first output of the block 28 determining the quadrant of the arrival of the signal AE. This allows the passage of pulses from the generator 54 through the circuit AND 52 to the counting input of the counter 53,

which counts the time interval Tmeks. When a false combination of the sequence of arrival of the AE signal is detected on the converters 1-4, the counter 53 and the trigger 51 are reset by a signal from the output of the circuit.

OR 14.

Thus, the use of the invention allows to increase the accuracy of determining the coordinates of both a discrete and continuously acting source of AE.

Claims (2)

1. A method for determining the coordinates of an acoustic emission source, which consists in receiving acoustic emission signals from two antennas the four transducers located at the vertices of the square measure the differences in the arrival times of the acoustic emission signal at the transducers and determine the coordinates of the acoustic source emission, in order to improve the accuracy of determining the coordinates and expand functionality, fix the moment of arrival of the acoustic emission signal on all converters of each antenna, record the moments of the acoustic emission signal from zero from the negative region of its values to positive for all converters of each antenna, measure the time interval L2 between the moments of the transition of the acoustic emission signal through zero from the negative region of its values to the positive for first and last signal generators compare it with a predetermined delay T max and, when condition P2 T max is determined, the sequence of arrival of the acoustic emission signal at the transducers of each antenna is measured, the time interval Gz4 of acoustic emission propagation between the transducers of the diagonal pairs of each antenna is measured the second and the third, which determine the signal, determine the angles of arrival of the acoustic emission signal at the antennas and, using the values obtained and the position of the antennas, calculate the coordinates of the source nick acoustic emission, and the distance I between the diagonal transducers each antenna and the delay T max is determined from the relations: I - Lmin t I I and max t ()5 MINUTES where AMIN and Cmin are the minimum possible length and velocity of the ultrasonic wave in the test structure. 2. An apparatus for determining the coordinates of an acoustic emission source, comprising two groups of blocks, each of which consists of four parallel channels including a serially connected transducer, an amplifier and a driver, a time interval meter and serially connected OR circuits and delay lines, and serially connected computing units and the recorder, and the block converters form two antennas, which, in order to increase the accuracy of determining the coordinates and expand the function capacity, it is equipped with a memory unit, in each channel - a signal detection unit, the input of which is connected to the amplifier output, and a trigger, the synchronous input of which is connected to the output of the imager, in each group of blocks - by the circuit I and the block for determining the quadrant of the signal arrival, the first four inputs of which are connected to the corresponding inputs of the time interval meter and the outputs of the trigger of each channel of this group of blocks, the fifth input - to the fifth input of the meter time intervals and the output of the delay line, the first output to the second input of the delay line, the second output to the first input of the OR circuit, the inputs of the AND circuit are connected to the corresponding outputs of the signal detection units each channel of this group of blocks, output - to the information inputs of triggers of each channel of this group of blocks, the second input of the OR circuit is connected to the first output of the time interval meter, the output to the inputs Reset of the trigger, the information inputs of the memory block are connected to the corresponding second and third outputs of the meter time intervals and the third output of the block for determining the arrival quadrant of the signal of both groups of blocks, the inputs Record - to the corresponding fourth outputs of the time interval meter of each group of blocks, and the output - to the computing unit. AND FIG. 2 Fig.Z IB From the delay line 15 Oe J R hell J / 45 5 Sm lines Wraps 15 Refl-kaB 12B. Lt element PAI M To the item. Mlt Hi IS IS To the delay line K 55 R Quelett Mn N FIG. 6 7