SU1262363A1 - Device for checking articles by acoustical emission signals - Google Patents

Abstract

The invention relates to a technique for non-destructive quality control of products and is intended to detect developing defects and determine their coordinates by registering acoustic emission signals (AE) emitted by defects. The aim of the invention is to increase the reliability and reliability of the control results by eliminating false positives of the indicator upon receipt. an incomplete pulse train from an AE source, AE signals taken from the transducers are amplified by amplifiers, detected by detectors. At the outputs of the latter, video pulses are obtained, which are shifted in time one relative to the other. The time intervals depend on the relative orientation of the AE signal source and the acoustic transducers. These video pulses are input to the amplitude selector, where the video pulse that came earlier triggers the selector and passes to its output, and the video pulses received in other channels and entered the selector inputs later are passed to them only if their amplitude is in a certain functional depending on the amplitude of the first video pulse. This is the case if signals from a single LE source are being received. Video pulses corresponding to the same AE source from the selector outputs through the shapers are fed to the strobe pulse shaping unit and a logic unit generating video and pulses with a duration equal to the delay time between a pulse in each channel and a pulse from the same series but arriving the very last. These video pulses of different durations are fed to the inputs of four memory time-amplitude converters, and from their nOvTy4eHHbie voltage outputs via the keys controlled by the strobe pulse-forming unit. - a bridge circuit and a two-coordinate recorder showing (L is the coordinates of the AE source on a certain scale. When two, three or one voltages are received from the drivers at the inputs of the strobe-pulse shaping unit, the control signal will not be closed, At the same time, the internal additional keys of the strobe-IMO5 pulse shaping unit, which protect from subsequent to positives, are closed.When all four-co signal from the formers arrive at the strobe pulse formation unit ode b.yuka of this is video pulse, ny ravso duration time actuation indicator device. The control unit then again comes into the operating state. Elimination of false positives indicator allows to increase the reliability and accuracy of the testing results. 8 yl.

Description

The invention relates to a technique for non-destructive quality control of products and is intended to detect developing defects and determine their coordinates by registering acoustic emission signals (AE) emitted by defects.

The purpose of the invention is to increase the reliability and reliability of the control results by eliminating the false alarms of the indicator while receiving an incomplete pulse train from an AE source.

FIG. 1 shows a block diagram of a device for monitoring products based on AE signals; FIG. 2 - voltage diagrams at various points of the device; in fig. 3 - section of the structural scheme, including the logical block and converters, time-amplitude; in fig. 4 - stress diagrams at various points of the circuit; in fig. 5 is a block diagram of a logic unit; in fig. 6 - diagrams of logical side voltages; in fig. 7 is a block diagram of the time-to-amplitude memory converters; in fig. 8 - stress diagrams at various points of the circuit.

The device for monitoring products for acoustic emission signals contains four channels. The nerve channel contains a series-connected acoustic transducer 1, an amplifier 2 and a detector 3, in the second channel - a series-connected acoustic transducer 4, an amplifier 5 and a detector 6, in the third channel - a series-connected acoustic transducer 7, amplifier 8 and the detector 9 and in the fourth channel-successively connected acoustic transducer 10, amplifier 1 and detector 12. The outputs of the detectors through the amplitude selector 13 and four drivers 14 are connected to the inputs of the logic unit 18 and strobe pulse forming unit 19. The four outputs of logic block 18 are connected via memory storage converters 2023 time-amplitude, keys 24-27 and matching block 28 to a two-coordinate indicator 29, and the output of gate gate-forming unit 19 is connected by control inputs of keys 24-27. The strobe-inn shaping unit 19 consists of four additional keys 30-33, the outputs of which through the waiting multivibrators 34-37 are connected to the element AND 38, to the elements OR 39-42, and also through the differentiating chains 43-46 and connected in series with them 47-50 inverters with the element OR 51, and its output is connected to the discharge elements of the waiting multivibrators 34-37. The output of the AND 38 element is connected to the input of the additional standby multivibrator 52, and its output is connected to the second inputs of the OR elements 39-42, as well as to the control inputs of the keys 24-27.

The outputs of the elements OR 39-42 are connected respectively to the control inputs of the keys 30-33.

Block 18 (Fig. 5) consists of four RS-flip-flops 53-56, the outputs of which are connected to the inputs of the element And 57, as well as through differentiating chains 58-61c with an adder 62, the output of which is through a series-connected peak detector 63, comparator 64, which differentiates the chain 65 and the inverter 66 is connected to one of the inputs of the adder 67, the output of which is connected to the parallel-connected S-inputs of the flip-flops 53-56, and the second input is the output of the And 57.

Each block 20-23 of storage time-to-amplitude converter (Fig. 7)

consists of a current generator b o, which through a normally closed key 69 is connected to a charging element (capacitor) 70, in parallel with which a second normally closed key 71 is connected, whose control input is via a series-connected inverter 72, a differentiating chain 73, a multivibrator 74 and the second differentiating chain 75 is connected to the control input of the key 69.

The device works as follows.

Claims (1)

AE signals are received spaced and reinforced by acoustic transducers 1, 4, 7 and 10 on the surface of the product being monitored. Signals taken from transducers are amplified by amplifiers 2, 5, 8 and 11, and then detected by detectors 3, 6, 9 and 12, at the outputs of which we obtain video pulses that are shifted in time relative to each other by time intervals depending on the relative orientation of the source of the AE signal and acoustic transducers, 4, 7, and 10. These video pulses go to four inputs of the amplitude selector 13, where coming off their selektirovanie by amplitude-time dependency characteristic of the signals from. any one source of AE. From the outputs of the amplitude selector 13, the pulses pass through the for makers 14–17 and arrive at logic block 18, which produces rectangular video pulses with a duration equal to the delay time between the pulse in each channel and the pulse peaked from the same AE source last. These video pulses of different durations are fed to the inputs of four memory converters 20-23 time-amplitude, which produce and store at the output voltage, proportional to the duration of the incoming pulses to the inputs of the pulses. These voltages are applied to the inputs of normally-closed keys 24-27, which are opened by a video pulse U, are received by a video pulse. I tag prepares the control inputs of keys 24-27 from the output of the pulse shaping unit 19 only if Complete series of Ui.-U4 signals from a registered AE source. If any of the signals Ui-Ua or Ui are missing, then the Ur video impulse is not generated and the keys 24-27 are not opened, which prevents the generation of incorrect information about the coordinates of the AE source. After opening the keys 24-27, the voltage from the converters 20-23 (one of them is zero) is sent to the matching unit 28 composed of resistors, and from its output to the two-coordinate indicator 29, showing the coordinates of the AE source. The voltages Ui-U4 from the outputs of the formers 14-17 are fed to the inputs of normally open additional keys 30-33 installed at the input of the strobe-pulse forming unit 19. Passing through the keys, these voltages trigger pending multivibrators 34-37 operating in standby mode. The time constants of the RC circuits of the multivibrators are chosen such that they produce Ue-Ug video pulses with durations equal to the transit time of AE signals from the most distant portions or equal to the response times of the remaining units of the device. In addition, in the waiting multivibrators. 34-37, it is possible to transfer them to a stable state before the end of the pulse produced by them. To do this, parallel to their storage elements (capacitors during the driving circuits) are connected normally closed discharge elements, such as field effect transistors, opened by the pulse signal Ui2. The video pulse Ue, developed earlier than the pulses in other channels, goes to the differentiating chain 43, and the signal Uio, which corresponds to the falling edge of the pulse Ue, passes through the inverter 47, goes to one of the inputs of the OR element 51, and from its output to the bits elements of the waiting multivibrators 34-37 and puts them in a steady state. When two, three or one single voltage Ui - U4 is applied to the inputs of the strobe-pulse shaping unit 19, one, two or three voltages Ue-Ug and signal UIQ are also generated at the output of the And 38 element and do not appear. The pulses Ug-Ug also come through the elements OR 39-42 to the control inputs of the keys 30-33 and close those that received the input pulses Ui, U2, Us or U4. This prevents pending multivibrators 34-37 from subsequent triggers when there are several video pulses in one channel at the inputs of keys 30-32 or 33. After one of the multivibrators 34-37 returns to the initial state, the pulse obtained by differentiating the falling edge of the Ue-Ua signals or Ug, puts the remaining multivibrators in a steady state, and the pulse shaping unit 19 returns to the steady state again. Upon receipt of the strobe-pulse unit 19 of all four signals Ui - U4 from the same AE source, the overlapping parts of the pulses Ue-Ug cause the appearance at the output of the element 38 and the signal U 11, which triggers an additional standby multivibrator 52 operating in the standby mode and generating video impulse Us equal in duration t - response time. indicator device 29. This video pulse through the elements OR 39-42 closes the additional keys 32 and 33 for the time t, and also opens the keys 24-27, the voltage from the transducer output time amplitude 20-23 goes to the matching unit 28, and then to the two-coordinate indicator 29. After the termination of the pulse Ur, the keys 24-27 are closed, and the additional keys 30-33 are opened, and the gate-pulse shaping unit 19 comes back into operation. After the arrival of the new pulse sequence Ui-U4, the strobe-pulse shaping unit 19 is triggered, and then after an interval T returns to its original state. The four inputs of the logical block 18 in general form receive a sequence of pulses Ui - Lj4 shifted in time and distributed randomly over the channels. At the outputs of block 18, three video pulses Ui3-Uis are formed, the duration of which is equal to the time interval between the pulses Ui - Ua and the pulse U4 received last. In addition, a short pulse can form and 16, with a duration approximately equal to the duration of the signal U4. The Uis-Ulg signals are fed to memory times - amplitude converters 23, 22, 21, 20, producing voltages Ui / - Uig with an amplitude of a flat top, proportional to the size of the intervals TI-g. The amplitude of the signal U20 will be near zero due to the small duration of the signal UIG. The storage time T4 is chosen to be approximately equal to the duration of the video pulse Us (Fig. 4), after which the voltages Ui -U2ii are reset to zero. The pulses Ui - U4 (Fig. 5) arrive at the R-inputs of the flip-flops 53-56 and transfer them to a single state. Uia-Uir signals are generated at the trigger outputs. When the last time signal Ui6 appears, the output of the circuit 57 of Mate yields a signal U2i, which through the adder enters the S inputs of the flip-flops 53-56 and transfers them to the zero state. The duration of the signal Uie is equal to the sum of the switching times of the blocks 34, 44 and 33 and for actual monitoring cases is significantly less than the duration of the signals Ui3-Ui6- Therefore, the presence of the signal Ui6 does not lead to any noticeable errors in determining the coordinates of the AE sources. The generation of voltage U2i occurs only in the case when all four flip-flops 53-56 are transferred to a single state. Therefore, when only part of the signals Ui-U4 arrive, the voltage U2i is not generated and the flip-flop of the flip-flops to the zero state does not occur, which can lead to malfunction of the entire device. Therefore, in block 18, an additional (at a certain interval) flip-flop of triggers to the zero state is provided. For this, the voltage Uia-Uie is differentiated and the signals U22-U25, corresponding to their leading fronts, are fed through adder 62 to the input of the peak detector 63 with discharge time T equal to the maximum probable interval. If during this time the signal U2I is not produced, then The value of Ua at the detector input decreases to zero. The comparator 64 then goes to the zero state, and the output of the inverter 66 produces a pulse Uso corresponding to the falling edge of the signal 67, and flips the triggers 53-56 to the zero state. The voltages Uia-Uie from the outputs of the triggers are fed to the inputs of the storage converters 20-23 time - aplity. The Uia video pulse opens the key 69, and the element 70 is charged to a voltage Un proportional to the duration TI After differentiating the pulse lJi3, the part of the voltage Uai corresponding to the trailing edge of the pulse Uis triggers the signal 74 that produces (video pulse U32 with duration T4, After differentiating and inverting the signal U34, which corresponds to the trailing edge of the U32 pulse, opens the key 71 and the element 70 is discharged through it to zero. Thus, in the proposed device as a result of the introduction of four keys and a forming unit the strobe pulse eliminated the false alarms of the indicator in the absence of a signal in any of the channels, and the indication of the coordinates of the AE source is made only if there is a complete sequence of informative signals taken from all the channels. containing four channels from series-connected acoustic transducer, amplifier and detector, amplitude selector, whose inputs are connected to the outputs of the detectors, log a unit and four formers connected between the outputs of the amplitude selector and the inputs of the logic unit, four memory time-amplitude converters, the inputs of which are connected to the outputs of the logic unit, a matching unit and a two-coordinate indicator connected to the outputs of the matching unit, characterized in that increase the reliability of control, it is equipped with four keys, installed respectively between the outputs of the four transducers time - amplitude and the inputs of the matching unit, and the unit f strobing pulses, the output of which is connected to the control inputs of four keys, and four inputs connected to the outputs of the drivers, the strobe pulse formation unit is made in the form of five OR elements, four channels, each of which consists of a series-connected additional key, waiting for a multivibrator, differentiating circuit and inverter, the output of each inverter is connected to the inputs of the first element OR, and its output - to the reset inputs of the waiting multivibrators, the outputs of which are connected by the first inputs of OR elements, series-connected AND elements and an additional standby multivibrator, the output of which is the output of the strobe-pulse shaping unit and connected to the second inputs of the remaining OR elements, the output of each of them is connected to the control input of the additional key of the corresponding channel, and the signal input It is one of the four inputs of the strobe-pulse shaping unit. - srig.Z i / 26 fig l ut ig L / 1 sh UI3 and № Ш5 ip Ui ia from Ш5 ig: igg ig their FIG. 6 t 65 6 66 FIG. five L / r FIG. 7