SU1499224A1 - Apparatus for determining posiotion of source of acoustic emission - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to locate defects in materials and rock massifs. The aim of the invention is to increase the reliability of determining the location of the acoustic emission source by obtaining more accurate information about the time of arrival of signals. The acoustic emission signals are received by transducer 1 and then the signal is electrically processed in the device. The comparator 8 captures the moments of the zero-transitions of the signal, which are recorded in the operational storage unit 15. At the moments of writing, the codes from the output of timer 23 are written to the address inputs. The number of zero-transitions is counted in the reversible counter 17, which overflow causes blocking of these pulses, preventing the re-recording of information in the operational storage unit 15 within a single acoustic emission pulse. When reading information from it, a significant subtraction of the number from the reversible counter 17 occurs and, in the zero state, the input of information of this channel to the computing unit 20 is completed, which calculates the difference in arrival times of signals from different channels. 1 il.

Description

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The invention relates to a non-destructive testing technique and can be used to locate defects and cracking sites in materials and rock massifs.

The goal of the invention is to increase the reliability of determining the location of the source of acoustic emission (AE) by more fully using information about the temporal position of the signals.

 The drawing shows a block diagram of a device for determining the location: The location of the AE source.

The device contains p channels for receiving AE signals, including a converter 1 connected in series, a selective amplifier 2,

And 22 is connected to the direct outputs of RS-flip-flops 7, and its output is connected to the control input of the computing unit 20, the first control output of which is connected to the control input of the switch 19, the second to the R-inputs of RS-flip-flops 6 and 7 the third is with the read input of RAM 5 and the subtracting input of the reversible counter 17.

The device works as follows.

The signal from the second control

The output of the computing unit 20 is unlocked by the receiving channels of the device by setting the RS flip-flops 6 and 7 in the nupe state. And a reversing counter 17. Signal

3 envelope detector, threshold element 20 AE, received and converted to

ment 4 and the first driver 5 short pulses, the first and second outputs of which are connected respectively the first 6 and the second 7 RS-flip-flops, connected in series to the comparator 8 and the second driver 9 short pulses, the first and second outputs of which are connected to the inputs of the element OR 10, connected by the third input to the first output of the first shaper 5 short pulses, and the output through the delay element 1 to the element 12, to the other inputs of which the direct and inverse outputs of the first 6 and second 7 are connected, respectively. RS-flip-flops, and to the output - the C-inputs of the D-flip-flop 13, register 14 of the operational storage unit (RAM) 15 and through the inverter 16 the input of the summation of the reversing counter 17, the outputs of which bits are connected to the address input of the RAM 15 and the decoder 18, and the inverse high-order output to the input of the And 12 element, the outputs of the D-trig-45 sive counter-17 and the preparatory liger 13 and the register 14 are connected to the data inputs of the RAM 15, the input of the comparator 8 is connected to the output of the O-terminal 2, and its output - with the D-input of the D-flip-flop 13, as well as common for all channels in series The switch 19, the computing unit 20 and the recorder 21, the element 22, the timer 23 and the pulse generator 24 connected to it, the output of the timer 23 connected to the D inputs of the register 14, the inputs of the switch 19 connected to the outputs of the RAM 15 and the decoder 18, entrances ele50

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Thus, the address of the next cell of RAM 15 is recorded. The signal from the output of the selective amplifier 2 also goes to the comparator 8, during which a series of square impulses is formed, the fronts and decays of which are connected to positive and negative signal rises through the zero level and on which by means of the second imager 9 short pulses form corresponding short pulses. These pulses through the elements OR 10 and the delay 11 in the current-electric signal by the converter 1 of one of the channels, passes through the selective teacher 2, the envelope detector 3 and the threshold

element 4, at the output of which a rectangular impulse is formed, the front and decay of which correspond to the beginning and end of the impulse AE at a given threshold level, which

the first shaper 5 short pulses are formed the corresponding short pulses. The start pulse sets the first RS flip-flop 6 to the one state and then through the OR 10 element and the delay element 11 passes through the open element 12 and writes to the register 14 and from it to the RAM cell 15 with zero address the current code

timer 23 corresponding to the moment when the envelope of the signal exceeds a predetermined threshold level; by decreasing this pulse through inverter 16 the rever0 code increases by one

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Thus, the address of the next RAM cell 15 is recorded. The signal from the output of the selective amplifier 2 also goes to the comparator 8, at the output of which a sequence of square impulses is formed, the fronts and decays of which are tied to the positive and negative signal transitions through the zero level and on which by means of the second shaper 9 short pulses form corresponding short pulses. These pulses through the elements OR 10 and delays 11 during the time when the envelope of the signal of a given threshold level exceeds the threshold pass through the open element 12 and smallpox (recording is made in register 14 and then in RAM cells 15 corresponding to their temporary position of timer codes 23. V older the bit size of the RAM 15 is set to the output level of the D-flip-flop 13, which determines the sign of the null transition (one - plus, zero - minus). At the end of the signal, the drop down and from the first driver 5 short pulses are set to one second RS-flip 7 and zero ur from the inverse output closes the element 12 and prohibits further registering the zero-transition moments in the RAM 15 and blocking the corresponding 1st channel. reception. The unit level from the direct output of this trigger enters the input of the element 22, the other inputs of which are connected to the outputs similar to RS -triggers of other channels 7. It is also possible to block the channel when the reversing counter 17 overflows with a low level at the inverse output of its higher secondary bit connected to one of the inputs of the element 12. This prevents with re-record information in the RAM-15 within one pulse AE.

After the end of the entire received locational series of pulses AE, on the trigger of the coincidence element, a single level is set informing the computing unit 20 about the completion of the measuring cycle. According to this signal, the computing unit 20 organizes the input of measurement information on the RAM 15 of all channels into the buffer memory of the block using the control signals of the switch 19 (channel selection) and reading of the RAM 15. By decreasing the reading signal, the content of the reversible counter 17 is reduced by 1 ton. e, preparing the address of the next readable cell. In this case, one of the bits of the information bus enters into the computing unit 20 an output level from the decoder 18 of the zero state, according to which the computing unit 20 determines the end of the input of information from the corresponding channel. It also allows you to locate the channel in which

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 the beginning of the AE impulse was not recorded, and determine the number of the zero-crossing signal registered during the pulse. Upon completion of the input cycle, the computing unit 20 issues a setup signal to the RS flip-flops 6 and 7, preparing the device channels

10 to receive the next location series of AE pulses, and proceeds to the analysis and processing of the received information.

Based on the information about the moments of signal zero crossing, the computational block 20 calculates for each channel pair the sign correlation functions (ICFs) and from the maxima of the sign CMFs, the time

20 position of the signals and their arrival time difference (RWP). It is distinguished by simplicity of software implementation and high speed, since it does not require the execution of operations much more than 25. The minimum step of changing the delay is determined by the frequency of the generator 24 pulses. As the initial values of the RVP, you can use delays calculated by the moments

30 exceeding the envelope of the signals of a given threshold level, and then, by searching for the maxima of the sign CCFs, correct the errors of the initial RTD estimates. The estimates obtained for the maxima of the sign CCFs and RTDs are close to the optimum estimates of the signal time positions.

Based on the found RWP values, based on the known algorithms, the computing unit 20 calculates the coordinates of the AE source, which are output to the recorder 21. The following

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note that on the basis of the registered primary information, such important time parameters of AE signals as the duration at a given threshold level, the number of zero crossings and the average filling frequency that can be used, for example, to identify signals, adapt the threshold and Others By changing the threshold of the comparator 8, it is possible to record the instants of coupling the signal to the threshold level, which differs from zero. This changes the peak shape of the maximum of the MCF and the resolution of the estimation of RAH.

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Thus, the use of more accurate integral estimates of the temporal position of the signals on the basis of the sign CCF allows, in comparison with the known devices using point estimates, to increase the reliability of determining the location of the source A3. In this case, the sign MCFs are calculated by easily adjustable moments of signal transitions through zero (or a level different from zero using fairly simple algorithms that do not require complicated arithmetic operations.

Claims (1)

Invention Formula A device for determining the location of an acoustic emission source, comprising a series-connected n-channel switch, a computing unit and a recorder and n reception channels, each of which contains a series-connected acoustic transducer and measuring amplifier, a threshold element, a ShN element, a D-trigger and an And element, characterized in that, in order to increase the reliability, it is equipped with an I-channel element AND, the output of which is connected to the starting input of the computing unit, and sequentially with Connected by a pulse generator and a timer, and a calid of n receiving channels is equipped with an envelope detector connected between the output of the selective amplifier and the input of the threshold element, a delay element connected between the output of the OR element and the first input of the AND element, the first driver of short pulses, the input of which is connected to the output of the threshold element, the first and second RS-triggers, -S-inputs which under eight Connected respectively to the negative polarity output and the positive polarity output of the first short pulse shaper, connected in series by a comparator, the input of which is connected to the output of the selective amplifier, and the second short pulse shaper, whose negative and positive polar outputs are connected to the first and second inputs of the element OR, sequentially connected by an inverter, reversible The high-inverse output of which is connected to the second input of the element I, and the decoder and serially connected register and the operational storage unit, the output of the comparator is connected to the D-input of the D-flip-flop, the output of which is connected to the address input of the operational storage unit inverse output the first RS-flip-flop and the direct output of the second RS-flip-flop are connected to the third and fourth inputs of the I element, the output of which is connected to the C-inputs of the D-flip-flop and the register and to the recording input of the operational storage unit, forward The first output of the first RS flip-flop is connected to the corresponding input of the n-channel element I, the decoder code and the operative storage unit are connected to the corresponding inputs of the n-channel switch, the timer output is connected to the information inputs of the registers, the output clock of the computing unit is connected to the read control input of the operative the storage unit and to the subtracting input of the reversible counter, and the output signal of the end of the computation of the computing unit is connected to the setup inputs of the RS flip-flops and the switch but.