SU1478384A1 - Method of monitoring integrity of sensitive components of piezoelectric converters - Google Patents

Abstract

The invention relates to the field of non-destructive testing and can be used to determine the integrity of sensitive elements of piezoelectric transducers, in particular, accelerometers, in the process of their manufacture and operation. The purpose of the invention is to reduce the time and increase the reliability by eliminating the drive's own resonances. In a piezoelectric transducer, mechanical oscillations are excited; by applying shock acceleration pulses of varying amplitude to it, they control the damping curve and its axis of symmetry. The deviation of the axis of symmetry from the centerline by the value of γ characterizes the integrity of the sensitive element. 2 Il.

Description

one

The invention relates to non-destructive testing and can be used to determine the integrity of sensitive elements of piezoelectric transducers, in particular accelerometers, during their manufacture and operation,

The purpose of the invention is to reduce the time and increase the reliability by eliminating the own resonances of the converter.

The method is as follows

In a piezoelectric transducer, mechanical oscillations are excited, acting on it by impulses of shock acceleration. Increase the amplitude of the exciting pulse and record the decay curve of electrical oscillations. The integrity of the sensitive element is evaluated in relation to the amplitudes of the response signal of the converter and the corresponding amplitudes of the shock acceleration pulses.

Figure 1 shows the decay curve of oscillations of a whole sensitive element; figure 2 - the same, with the destroyed sensitive element.

The process of damping oscillations in the piezoelectric transducer has a symmetrical view with the middle line 1 of the envelopes 2 and 3, which coincides with the end 4 of the shock process for the whole sensitive element. To destroy the sensitive element, the median line 1 is deflected by the value of -j- and does not coincide with the end line of the shock pulse.

 one

oo with

00 Ј

The magnitude of the deviation is calculated by the formula

Calculate (

Ur

U

well a

- one)

where is ut. U and the amplitude of the first pulse of the converter output signal after and before the occurrence of damage; corresponding amplitudes of shock acceleration pulses.

Example. A piezoelectric transducer with a sensitive element made of PZT-19 piezoceramic material was subjected to shock acceleration pulses of increasing amplitude up to the working limit (from x 10 s mo -2

m -c

10 M S TO 6 X

with multiplicity of order

5-10 m with 2). For this, we used a shock stand with the well-known principle of braking a movable striker, made in the form of a tandem, on a fixed measuring rod, on which the transducer under test was fixed. The bench reproduced shock pulses in shape, close to half-sine, with a duration of 20-25 μs.

A storage oscilloscope was used to record the oscillation decay process. After registering this process on the oscilloscope screen, it was photographed, the envelopes and their middle line were drawn using a photocopy (figure 1, figure 2).

Experimental results showed that the process of damping of oscillations in a piezoelectric transducer, in a sensitive element of which there is no mechanical damage, has a symmetrical appearance and

the middle line 1 of the envelopes 2 and 3 coincides with the line 4 of the beginning of the shock process (figure 1).

For transducers, in the sensitive element of which, during testing, mechanical damage (cracks, chipping on the lateral surface) appears, the attenuation of the grit is broken and the average line 1 of the envelopes 2 and 3 does not coincide with the line 4 of the beginning of the impact process ( 2).

The deviation of the midline 1 of envelopes 2 and 3 (Fig. 2) by 5–10% indicates the presence or the appearance of damage to the sensing element, which is visually detectable, and the amplitude of the shock pulse corresponding to this deviation determines the limit of their mechanical strength.

Claims (1)

Invention Formula The method of monitoring the integrity of the sensitive elements of piezoelectric transducers, which consists in that mechanical vibrations are excited in the transducer and the attenuation parameters of the vibrations of the transducer response signal are recorded, which are judged on the strength of the sensitive element, 5 due to the fact that, in order to reduce the time and increase the reliability due to the exclusion of the converter’s own resonances, oscillations are excited 0 by amplitudes of shock acceleration pulses, and the ratios of the amplitudes of the response signal and the corresponding amplitudes are determined as attenuation parameters. 5 TUD shock acceleration pulses. 0 five 0 1 FIG. g