SU1663530A1 - Device for acoustic inspection of structures - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to determine the state of thin-walled structures from acoustic emission signals. The aim of the invention is to increase the resolution due to the fact that the sensing element of the transducer 1 is made of a segmented soft dielectric film, the sensitivity of the transducer 1 varies inversely with the value of the input signal exceeding the specified discrimination level. The control electrode 4 of the converter 1 is given a signal in antiphase with respect to the input one that has exceeded the level of discrimination, which leads to a change in the polarization value of the sensitive element of the converter 1. 1 sludge.

Description

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(21) 4086705/28 (22) 07.09.86 (46) 07.15.91. Bul №26 (72) A.I.Adonin, V.N.Moskvin, A.N. Serious and V.P. Starikov (53) 620.179.16 (088.8)

(56) Greshnikov V.A. Drobot Yu.B. Acoustic emission. M .: Izd. standards, 1976, pp.68-69.

Sharp R. Nondestructive Test Methods. M .: Mir. 1972, p.43-46. (54) DEVICE FOR ACOUSTIC CONTROL OF STRUCTURES (57) The invention relates to non-destructive testing and can be used to determine the state of thin-walled

designs by acoustic emission signals. The aim of the invention is to increase the resolution due to the fact that the sensing element of the transducer 1 is made of a segmented soft dielectric film, the sensitivity of the transducer 1 varies inversely with the value of the input signal exceeding the specified discrimination level. The control electrode 4 of the converter 1 is given a signal in opposite phase with respect to the input one that has exceeded the level of discrimination, which leads to a change in the polarization value of the sensitive element of the converter 1. 1 Il.

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about

The invention relates to the field of non-destructive testing and can be used to determine the states of thin-walled structures from acoustic emission signals mainly under pulsed loads.

The aim of the invention is to increase the resolution due to the fact that the sensing element of the transducer is made of a segret of a dielectric film, the sensitivity of the transducer varies inversely with the input signal value exceeding the specified discrimination level. The drawing shows a diagram of the device for acoustic control of structures.

The circuit contains a transducer 1 with a sensitive element made of a soft film segret, potential electrodes 2, 3 and a control electrode 4. The transducer is fixed with an adhesive joint 5 on the surface of the tested product 6. The potential electrode 2 is connected through a capacitor to a serially connected pre-amplifier 7 filter 8, the amplifier 9, the discriminator 10 and the measuring unit 11. The device also contains the control unit 12 and the block 13 of the reference signal. The first input of the control unit 12 is connected to the output of the discriminator 10. The output of the control unit 12 is connected to the control electrode 4. The first output of the block 13 of the disputed signal is connected to the second input of the control unit 12. Potential electrode 2 is connected to the second output of the block 13 of the reference signal.

A device for acoustic control of structures works as follows.

Before the control starts, a threshold voltage level equal to the noise interference level is set in the discriminator 10. The acoustic signal arising in the design 6, when it is loaded, is transmitted through the adhesive joint 5 to the sensing element of the transducer 1. The electrical voltage generated on the electrode 2, proportional to the acoustic signal, is amplified by the preliminary amplifier 7, filtered by the filter 8, is finally amplified by the amplifier 9 and

is fed to the input of the discriminator 10. In the discriminator 10, the input signal is compared in amplitude with the threshold voltage level. The excess signal from the discriminator 10 is fed to the first input of the polarization-magnitude control unit 12. The second input of the block 12 is supplied with the reference voltage from the block 13. At the output of the block 12 a difference signal is generated in the opposite phase with respect to the input. The voltage from the output of the control unit 12 is supplied to the control electrode 4 and changes the polarization value of the sensitive element of the converter 1, which was maximum before the monitoring process. For a number of ferroelectrics, a change in the induced polarization E from 0 to 4 kV / cm is accompanied by an increase in the piezoelectric modulus and a decrease in the dielectric constant. Therefore, a change in the value of E leads to a change in the sensitivity

S converter.

Thus, this device allows to increase the resolution by reducing the sensitivity in proportion to the time variation of the amplitude of the input signal and thereby register acoustic signals of different amplitude, following with an interval of 5-10 microseconds.

Claims (1)

Apparatus for acoustic control of structures comprising a transducer connected in series, made in the form of a sensitive element with a potential electrode, a preamplifier, a filter, an amplifier, a discriminator and a measuring unit, characterized in that, in order to increase the resolution, it is provided with a series-connected unit the reference signal and the control unit, the sensitive element of the transducer is made of a soft dielectric film segret and is equipped with a control electrode connected to the output of the control unit, the first input of which is connected to the output of the discriminator, and the potential electrode is connected to the second output of the reference signal block.