SU782184A2 - Method of non-destructive testing of piezoelectric elements - Google Patents

Description

one

The invention relates to piezotechnique and hydroacoustics and can be used in testing piezoelectric elements, as well as products made from them.

According to the main author. St. No. 716135, a method for non-destructive testing of piezoelectric elements is known, in order to measure the quality index M (product of the square of the electromechanical coupling factor by the mechanical quality factor), combining these measurements with tests of the elements for dynamic strength and simplification, excites free oscillations in the element radio pulses with a carrier frequency equal to the frequency of the mechanical resonance of the element, and with respect to the amplitude of the voltage of free oscillations in the interval between the pulse The amplitude of the voltage of the exciting radio pulse is judged on the quality of the piezoelectric element 1.

The disadvantage of this method is the impossibility of measuring the acoustic-mechanical efficiency, designed to work in the fluid of the piezoelectric element.

The purpose of the invention is to provide a measure of the acoustic-mechanical efficiency intended for operation in a fluid of a piezoelectric element.

This goal is achieved by additionally measuring the ratio of the initial amplitude of the voltage of free oscillations Urn to the amplitude of the exciting voltage Osch for a piezoelectric element immersed in a liquid, and determining the acoustic-mechanical efficiency using the formula

10 p -1 M

OQM - 1 P

where M and M are the ratio of the voltage amplitudes UBIJ / Um measured in air and in liquid, respectively.

The method is carried out as follows.

Acoustic-mechanical efficiency expresses equivalent resistance to mechanical loss and radiation as follows.

Oo „

20

Formula (2) can be written in another form, where instead of TP and the mechanical Q of the unloaded element (i.e., measured in air) and the Q of the loaded element 0 are entered

(t W -fC3)

where Wp ijf-fp KpyroBaH resonant "Stot; Me is the equivalent mass of the oscillating element, which in the first approximation does not change when immersed in a liquid.

Then the numerator and denominator of the fraction are multiplied in formula (3) and the square of the coefficient of electromechanical communication (the value of K depends only on the properties of the hardware and the design of the piezoelectric element and does not depend on the properties of the medium in which the element is placed)

. (four)

in most cases, measurements of the values M and M are made at the same amplitude of the exciting voltage UH ,. Here, the definition formula (4) is simplified.

z- -l-F N-Yt -) - yy. )

Where UrajMllTOj is the initial amplitude of the electrical voltage of free oscillations for immersible (i.e., airborne)

and acoustically immersed

piezoelectric element.

Thus, in these cases, to determine 12a, it is sufficient to measure the amplitude ratio according to formula (5), i.e. just two measurements.

Claims (1)

Invention Formula The method of non-destructive control of piezoelectric elements according to ed. St.  No. 716135, characterized in that, in order to ensure the measurement of acoustic-mechanical efficiency, intended for operation in a liquid of a piezoelectric element, the ratio of the initial voltage amplitudes of the free oscillations Uma To the amplitude of the exciting voltage and, for the piezoelectric element immersed in the liquid, the acoustic-mechanical efficiency is determined by the formula W-.4Г1 bon where M and M are the ratio of the voltage amplitudes, measured in air and liquid, respectively. Sources of information taken into account in the examination 1. USSR author's certificate in application no. 2567138/10, cl. H 04 R 29/00, 1977.