SU1481672A1 - Device for monitoring article by signals of acoustic emission - Google Patents

Abstract

The invention relates to ultrasonic non-destructive testing methods and can be used in the control of products using acoustic emission. The aim of the invention is to increase the reliability of control through the use of amplitude and temporal selection of acoustic emission pulses. The received signal is subjected to amplitude selection by comparison circuit 4 and temporal selection by peak detector 8 and second comparison circuit 10 by selecting a constant discharge time of peak detector 8 for a longer average acoustic emission signal duration. 1 hp f-ly, 3 ill.

Description

Phie.1

The invention relates to methods of ultrasonic non-intrusive testing and can be used in the control of products using acoustic emission.

The aim of the invention is to increase the reliability of control through the use of amplitude and temporal selection of acoustic emission pulses.

FIG. a block diagram of the device is presented; figure 2 - reset circuit option; Fig. 3 shows temporary voltage diagrams for the operation of the device.

The device comprises a converter connected in series 1, an amplifier 2, an envelope detector 3 and a first comparison circuit 4, a reference voltage source 5 connected to a second input of the first comparison circuit 4, an F 6 circuit, the first input of which is connected to the output of the first comparison circuit 4, and a processing and registration unit 7 connected in series with a peak detector 8, a voltage divider 9 and a second comparison circuit 10, the output of which is connected to a second input of circuit F 6, and a reset circuit 11 connected between the output of the first comparison circuit 4 and the second input the house of the peak detector 8, the input of which is combined with the second input of the second comparison circuit 10 and connected to the output of the envelope detector 3, the reset circuit 11 is made of a collector resistor 12 connected to the collector circuit of the transistor 13, the emitter of which is grounded, a capacitor 14 connected in parallel the emitter-collector circuit of the transistor 13, the base resistor 15 connected to the base circuit of the transistor 13 and the input of the reset circuit 11, the third comparison circuit 16, the first input of which is connected to the collector of the transistor 13, the second source reference 17 is connected to the second input of the third comparison circuit 16, the output of which serves as the output of the reset circuit 11.

The device works as follows.

The acoustic emission signals, after being converted to electrical signals, are amplified in amplifier 2 and detected by an envelope detector 3, the shape of which is shown in FIG. At the exit

с- constant recession time

In comparison circuit 4, a pulse is generated with a duration equal to the total duration of the event (Lig. 36) at level E, which is set in advance depending on the level of the interfering signal of the envelope detector 3, the signal from which is also fed to the input of the peak detector 8, the discharge time constant tp which is selected and conditions

. P "with. where is c1

events.

The signal at the output of the peak detector 8 Normalizes the floating reference level F, for comparison circuit 10. At t-tt (Fig. 3a), the peak detector 8 is in the sampling mode and repeats the shape of the envelope; at point IT, it goes into storage mode, and the output signal decreases with a constant discharge time of detector C (segment II-III of FIG. In this case, the comparison circuit 10 at the point (HT.TI) of intersection of the signal of the envelope detector and the voltage part of the peak detector, determined by the division factor of divider 9, is transferred to the new stable state of logical O, and at the point III, i.e. at the time when the second superimposed event of level E is exceeded, the state of logical 1 is re-established at the output of the second comparison circuit 10 (Fig. 3c).

Thus, at the output of circuit 6, two pulses are formed, characterizing two separate events (Fig. 3e).

The reset circuit works as follows.

At time points inside the pulse of the total duration of the event, the output of the first comparison circuit 4 is at logic level 1, while the transistor 13 is open, the capacitor 14 is discharged, and the output of the circuits. comparison, a logical level of O is formed, which for the peak detector corresponds to the Storage mode. At the end of the positive pulse at the input of the transistor 13, it closes, and the capacitor 14 is charged through a resistor 15 of a voltage higher than the voltage of the source 17 of the supports. new voltage. At the moment of their equality, the comparison circuit 16 passes to a new stable state and to its

51

The output after the time & f (Fig. 3e) appears at a logic level of 1, which for the peak detector corresponds to the Reset mode with a decreasing speed of the input signal.

The use of the invention allows to increase the reliability of control of the product due to the reduction of the probability of missing events at a high intensity of their occurrence.

Claims (2)

1. A device for monitoring products based on acoustic emission signals, comprising a series-connected transducer, amplifier, envelope detector and first comparison circuit, a reference voltage source connected to the second input of the first comparison circuit, circuit K, the first input of which is connected to the output of the first comparison circuits, and a processing and recording unit connected to its output, characterized in that, in order to increase the reliability of the control, it is equipped with series-connected peak detector, voltage divider Eni, the second comparison circuit, the output of which is soy 10 15 816726 It is connected to the second input of the AND circuit, a reset circuit connected between the output of the first comparison circuit and the input of the peak detector, and the second inputs of the peak detector and the second comparison circuit are connected to the output of the envelope detector. 2. The device in accordance with claim 1, 1, Ik is that the reset circuit is made of a collector resistor, a transistor, a capacitor, a base resistor, a third comparison circuit, and a second reference voltage source, the first terminal of the collector resistor is designed to connect to power supply, the second is connected to the collector of the transistor, the emitter of which is grounded, and the base is connected to the first terminal of the base resistor, the first input of the third comparison circuit is connected to the first terminal of the capacitor and connected to the collector of the transistor, second The output of the capacitor is grounded, the second output of the third comparison circuit is connected to the output of the second reference voltage source, the second output of the base resistor is the input of the reset circuit, and the output of the third comparison circuit is the output of the reset circuit. 20 thirty Out 15 Out Fie.2 kudem Enut ".Per / tt scr2 1g ts t7 Phme.Z