SU1310712A1 - Method of determining coefficient of mechanical damping of piezoelectric transducers - Google Patents

Abstract

This invention relates to the field of testing piezoelectric transducers. The purpose of the invention is to improve the accuracy of measuring the mechanical damping coefficient (CD) of piezoelectric transducers (PP). To determine the CD, the ratio of the transfer coefficients of the studied PP in the radiation mode at the antiresonant and resonant frequencies of the PP is measured. According to the value of the obtained ratio, using the values of the coefficient of electromechanical communication and the normalized acoustic resistance of the working medium, known for this software, judge the magnitude of the CD. The method makes it possible to exclude the operation of compensation of the capacitance PP and with it the associated systematic error. 1 sludge. (Lu

Description

one )

The invention relates to the field of testing piezoelectric transducers and can be used in hydroacoustics and defectoscopy.

The purpose of the invention is to improve the accuracy of determination by eliminating the error due to electrical compensation of the piezoplastic.

The drawing shows a functional diagram of the device that implements the proposed method.

The device consists of a generator of radio pulses 1, the piezo transducer 2 under study, a broadband reference piezo receiver 3, switch A, meter 5 of the ratio of the amplitudes of radio pulses and the recorder 6. The position 7 designates the working medium.

The essence of the method lies in the fact that to determine the damping coefficient K, it is sufficient to measure the transmit (fx) coefficients of the piezo transducer under investigation at the antiresonant and resonant frequencies, determine their ratio and calculate the sought coefficient K, using the formula

 tKt.

to,

ffVt p. (Xo). (x;) r

F. (ho)

where K. is the coefficient of electromechanical communication piezomat

yala;

40

- acoustic wave impedances, respectively, of a piezo plate and a working medium;

the normalized transfer coefficient of the piezo transducer at the antiresonant frequency X in the radiation mode;

the normalized transmittance of the piezo transducer at the resonant frequency X in the emission mode.

Here, the values of K, and the piezo material used and the medium used are determined by known dami.

five

71

ABOUT

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0

35

40

45

22

The method is carried out 1 as follows.

From the generator of radio pulses, electric pulses with amplitude Ugj and a filling frequency equal to the antiresonant frequency X of the piezoelectric plates of the piezoelectric converter under investigation 2 are applied to the electrical input of the converter 2 under study. The electric signal of the converter 2 is converted into acoustic pulses that propagate in the working medium 7 (for example, water ) and are received by a wideband piezoelectric receiver 3, the electrical output of which produces an electrical pulse signal with an amplitude of I2 ( X). Then the generator 1 is rearranged to the resonant frequency of the piezoplates of the converter under study and is fed to the input of the converter 2 electric pulses with the same amplitude Ug and a filling frequency equal to the resonant frequency X of the piezoelectric plates. The resulting acoustic pulses are received by a wideband receiver 3, the electrical output of which produces a pulse signal with an amplitude U2 (X (j).

Due to the close location of the resonant and antiresonant frequencies, the transfer coefficients of the working medium and the piezoelectric receiver when the generator 1 is tuned to the resonant frequency of the piezoelectric plate of the transducer 2 under study remain practically unchanged. Therefore, the voltage ratio of the electrical signal at the output of the exemplary piezo receiver 3 is proportional to the ratio of the transfer coefficients of the piezo transducer 2:

UjiXol fliXa

nlXj „(ho)

(2)

and (x;) F

With the amplitude ratio meter 5, the ratio of the voltages (and UJ (XQ)) and the output signal of the meter 5 of the amplitude ratio is proportional to the ratio of the normalized transmission coefficients and).

The desired value of the K coefficient, the damping, is determined by calculating using registrar 6 according to formula (1).

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Claims (1)

Invention Formula The method for determining the mechanical damping coefficient of piezoelectric transducers, which consists in exciting and recording thickness oscillations of the transducer's piezoelectric plate at an antiresonant frequency, measures the ratio of the transfer coefficients of the piezoelectric transducer, which take into account the magnitude of the mechanical damping factor, and the ones measured, and those that determine those mechanical factors. , in order to improve the accuracy of determination, they additionally excite and register thickness oscillations of the piezoplates at the resonant frequency, measure the ratio of the transfer coefficients of the piezoelectric transducer at the antiresonant and resonant frequencies, and the coefficient Compiled by S. Volkov Editor A. Revin Tehred I.Popovich Proofreader A..0bouchar Order 1884/40 Circulation 777 Subscription VNIIPI USSR State Committee for inventions and discoveries P3035, Moscow, Zh-35, Raushsk nab ,, d.4 / 5 Production and printing company, Uzhgorod, Projecto st., 4 124 nominal K (mechanical damping is determined by the formula  ,    - f-Wu / tocF  - P.W TO 7 /about 5/5 0 where Kj is the electromechanical coupling coefficient of the piezo material; K, Z, / / Zg, Zg, acoustic wave impedances, respectively, of a piezoplate and working medium; (j (Xd) is the normalized transfer coefficient of the piezoelectric transducer at the antiresonant frequency ) - the normalized transfer coefficient of the piezoelectric transducer at the resonant frequency Xr. -