SU1638807A1 - Method for piezo element polarization - Google Patents

Abstract

This invention relates to ultrasonic testing and may be used to create ultrasonic piezoceramic transducers. The purpose of the invention — improving the quality of piezoceramic elements — consists in the current supplying electrical voltage to the electrodes of the piezoelectric element from the power source, changing the voltage from 0 to U0, where U is “1” and is the electrical strength of the piezoceramic material; 1 is the shortest distance between the electrodes. The voltage change is performed at a rate not exceeding the speed of the steady state equilibrium process in the piezo material. After setting U U0, the voltage is again gradually reduced to 0 also at a rate not exceeding the speed of the steady state equilibrium process in the piezomaterial. The voltage change is repeated n times, where n 5. 4 Il. c &

Description

The invention relates to an ultrasonic non-destructive testing technique and can be used to create ultrasonic piezoceramic transducers.

The purpose of the invention is to improve the quality of piezoelectric elements.

FIG. 1 shows schematically a device for implementing the proposed method J in FIG. 2 - dependence of the electromechanical coupling coefficient on the polarization voltage for different rates of change of the polarizing voltage (the dependence of a refers to the rate of change

of the applied voltage, not exceeding the speed of the steady-state equilibrium process in the piezo material); in FIG. 3 - modules of electrical resistance of the polarized piezoelement: a) the piezoelectric element is not polarized (U 0), b) the polarization voltage is taken to be Ut (11 11,), c) the polarization voltage is taken to be Uj (U U2), in this case, in FIG. 4 - the observed echo pulses received by the polarized piezoelement at different polarization voltages: a) U - 0, b) U and, c) U ig.

WITH&

with

00 00

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J1638807

The device (Fig. I) contains a voltage source 1 connected to electrode 2 via a restrictive

prx E pr strength of piezoceramic

Jo Eka

material Ј 1 is the smallest distance between the electrodes. The voltage change is performed at a speed not exceeding the speed of the steady-state equilibrium process in the piezoelectric material as an electromechanical system, after the voltage U U0 is established, the voltage gradually decreases again to 0, while the voltage reduction is performed at a speed not exceeding the speed steady-state equilibrium process in the piezomaterial. The described voltage changes are made at least five times.

To implement the method, it is necessary to determine the numerical value of the rate of the steady-state equilibrium process in the pieematerial. This can be done in various ways. For example, in Fig. 3d-b, the observed forms of the electric resistance module of the piezoelectric element in the frequency range of the resonance f ′ and the antiresistance Zorp and electrode 3 are shown. Between the electrodes 2 and 3 there is a polarized piezoelectric element A, parallel to which a measuring voltmeter 5 is installed. 2 and a source of voltage I included limiting resistance 6.

The source 1 of the polarizing voltage must be able to smoothly change the voltage of the polarization U. Voltmeter 5 must have a large input resistance (for example, electrostatic).

The method is carried out as follows.

An electrical voltage is applied to the electrodes 2 and 3 of the piezoelectric element from the power source 1 through the limiting resistance 6, the voltage of the power source varies from 0 to and, where U EnDl; E py electric 10

15

20

25

observable immunity. To determine the allowable rate of change II, it is necessary at some point in time, for example, at t t4, stop the change in y and observe the values of fp, fq or U "U1. If the amplitude of the pulse U or the frequency f p, f Q remain almost unchanged, then the rate of change of D is considered acceptable to ensure the progress of the equilibrium process. The values of fp, fg or U are practically unchanged when, after 3 minutes, the values of f p, fg, U differ from the initial values by no more than 0.25%.

Having determined the numerical value of the polarization rate for a given piezoceramic material, the polarization process begins, which is as follows: smoothly (with a certain speed) the polarization voltage increases from 0 to

1, where E is the electrical strength of a piezoceramic material; 1 is the smallest distance between the electrodes; when the value U0 is reached, they begin to decrease gradually 30

io E “P

Shut voltage to 0; Cycle 0- is repeated at least 5 times.

The use of the method improves the quality of the piezoceramic elements used to fabricate piezoceramic transducers.

Claims (1)

Invention Formula 40 A method of polarization of piezoelements, including a change in the magnitude of the electric voltage on the electrodes of the piezoelectric element from zero to pre-breakdown and back to zero, is different from 45 to preliminarily determine the rate of change in electrical voltage From the condition of a change in resonance and anti-resonance Ја, and in FIG. 4q-B- observable50 resonant frequencies with no more than echo pulses at a time of 0.25% with a delay of 3 min. T - t (when polarizing U0 after the last change, at tt, for U, j of the skip voltage, and the quantity at t tj, U ig. With increasing U u-cycles of electric variation, a resonant gap of $ 5 runs, more than five are chosen for the voltage. fa R and also amplitude difference i five 0 five observable immunity. To determine the allowable rate of change II, it is necessary at some point in time, for example, at t t4, stop the change in y and observe the values of fp, fq or U "U1. If the amplitude of the pulse U or the frequency f p, f Q remain almost unchanged, then the rate of change of D is considered acceptable to ensure the progress of the equilibrium process. The values of fp, fg or U are practically unchanged when, after 3 minutes, the values of f p, fg, U differ from the initial values by no more than 0.25%. Having determined the numerical value of the polarization rate for a given piezoceramic material, the polarization process begins, which is as follows: smoothly (with a certain speed) the polarization voltage increases from 0 to 1, where Е „р is the electrical strength of the piezoceramic material} 1 is the smallest distance between the electrodes, when the value U0 is reached, they begin to decrease smoothly io E “P Shut voltage to 0; Cycle 0- is repeated at least 5 times. The use of the method improves the quality of the piezoceramic elements used to make piezoceramic transducers. Invention Formula 0 A method of polarization of piezoelectric elements, including a change in the magnitude of the electrical voltage on the electrodes of the piezoelectric element from zero to “pre-breakdown and back to zero, is different from 5 OA and so that, in order to improve the quality of the piezoelectric elements, from the condition that the resonant and anti0 resonant frequencies vary by no more than 0.25% when exposed for 3 min after the last change in the electric voltage, and the number of cycles of change in the electric 12 „1 . five 1 FIG. I u t-ty u o a  a (Y Vv