SU1381385A1 - Apparatus for calibration of acoustic emission signal piezoreceivers - Google Patents

Abstract

The invention relates to the field of non-destructive testing by the method of acoustic emission (AE). The aim of the invention is to enhance the functionality and accuracy of calibration by providing calibration to a wide range of spectral and temporal parameters and reducing the influence of interference signals due to the plate from the piezo material And acoustically associated with her lindra special form. The device contains an ellipsoid piezoplate I with a beveled edge and with a polarized central part and an acoustically connected cylinder 3. The conical recess 10 and the circular grooves I1 scatter the ultrasonic vibrations emitted by the generator 2 by the plate 1, and the layer 5 absorbs them. The control piezosensor B and the signal processing unit 9 state the stability of the device operation. A graduated piezo receiver 6 of AE signals is installed on protector 7 acoustically connected with plate 1. 1 Il. and S (L

Description

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The invention relates to non-destructive testing by the method of acoustic emission (AE) and can be used in the calibration of piezoelectric receivers of AE signals,

The aim of the invention is to enhance the functionality and accuracy of calibration due to the implementation of calibration in a wide range of amplitude, spectral and. temporal parameters of the calibration signals and reducing the effect of radial oscillations and interference effects of the body 12, the cylinder 3, the plate 1 and the piezoelectric sensor 8, which allows the piezo receiver 6 to access the tread working surface 7.

A device for calibrating piezoelectric receivers of AE signals works as follows.

The electrical signal from the output of the generator 2, for example, the G5-56 pulse generator, is fed to plate 1 from the piezormaterial PZT-19, Piezoplast 1 with a contour-like configuration with an oval with a maximum

effects per amplitude-frequency characteristic - 15 45 mm and minimum - 30 mm, thickness 30

35

tristyku (AFC) device.

The drawing schematically shows a device for the calibration of piezoelectric receivers AE signals.

A device for calibrating piezo-20 AE signal receivers contains a plate 1 made of piezomaterial, an electrically connected generator 2, a solid-state cylinder 3 acoustically connected by one of the ends 4 of the 25 Hoh 1 plate, and a layer 5 applied to the lateral surface of the cylinder 3 A material that absorbs acoustic vibrations. Position 6 in the drawing indicates a graduated piezo receiver of AE signals. The device also contains an electrically conductive protector 7 acoustically connected to the free surface of the plate 1 and intended p, n calibrated piezo receiver 6, piezo sensor 8 with a resonant frequency equal to the center frequency of the operating frequency range, mounted on the side surface of the cylinder 3, and a control signal processing unit 9, electrically connected to the piezo sensor 8 o Plate 1 is full ellipsoid with a beveled edge and thick not exceeding a quarter of the acoustic wavelength at the upper frequency of the operating frequency range. The central circular portion of plate 1 is polarized. The diameter of the cylinder 3 exceeds the maximum size of the plate 1, the axially symmetric conical recess 10 is full on the free end surface of the cylinder 3, and circular grooves 11 are made on the opposite-face end surface 4 of the cylinder bounded by its outer diameter and the contour of plate 1 , a gradual increase in their depth in the direction from the center to the outer diameter. In addition, a co40 device

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0.4 mm, and the diameter of its piezo-active zone is 20 mm. The cylinder 3 with a diameter of 75 mm and a height of 110 mm is made of lead. The tread 7 is made of brass with a thickness of less than 0.2 mm. The connection of the plate 1 with the surface 4 of the cylinder 3 and the tread 7 is carried out by brazing with a Rose material with a bonding layer thickness of about 0.02 mm. The materials of the plate 1, cylinder 3, protector 7, and the layers fastening them are selected so that their specific acoustic impedances are close to each other. The piezoelectric sensor 8 is made shielded from PZT-19 with dimensions of 2x2x2 mm with a protector made of PZT-19 plate 0.15 mm thick. Piezoplastina 1 converts an electrical signal into an acoustic one. The acoustic signal propagates from one side through the surface 4 into the solid body of the cylinder 3, dissipating and damping in it at the recess 10 of the grooves 11 and layer 5 and partially falling on it. piezo sensor 8, and on the other - in the protector 7 on its working surface. A low-quality piezosensor 8, for example 2-4, converts the acoustic signal into an electrical signal, which is fed to the signal processing unit 9, the output of which judges the stability of the device operation. On the working surface of the tread 7 through the acoustic layer. the contact medium is set by a graduated piezo receiver, which converts acoustic oscillations into an electrical signal. Measuring this signal with a corresponding block (not shown), for example, with a spectrum analyzer or an oscilloscope, calibrate the piezo receiver 6 with various frequency, time and amplitude characteristics. The specified example of performing the mouth

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0.4 mm, and the diameter of its piezo-active zone is 20 mm. The cylinder 3 with a diameter of 75 mm and a height of 110 mm is made of lead. The tread 7 is made of brass with a thickness of less than 0.2 mm. The plate 1 is connected to the surface 4 of the cylinder 3 and the tread 7 by brazing with a Rose material with a bonding layer thickness of about 0.02 mm. The materials of the plate 1, cylinder 3, protector 7 and the layers fastening them are chosen so that their specific acoustic resistances are close to each other. The piezoelectric sensor 8 is made shielded from PZT-19 with dimensions of 2x2x2 mm with a protector made of PZT-19 plate 0.15 mm thick. Piezoplastina 1 converts an electrical signal into an acoustic one. The acoustic signal propagates from one side through the surface 4 into the solid body of the cylinder 3, dissipating and damping in it at the recess 10, the grooves 11 and the layer 5, and partially falling on it. piezo sensor 8, and on the other - in the protector 7 on its working surface. A low-quality piezoelectric transducer 8, for example 2-4, converts the acoustic signal into an electrical signal, which is fed to the signal processing unit 9, the output signal of which judges the stability of the device. On the working surface of the tread 7 through the acoustic layer. the contact medium installs a graduated piezo receiver, which converts acoustic oscillations into an electrical signal. Measuring this signal with a corresponding block (not shown), for example, with a spectrum analyzer or oscilloscope, calibrate the piezo receiver 6 with various frequency, time, and amplitude characteristics. The specified example of the implementation of the device

The device allows to obtain a frequency range from 0.1 to 2.0 MHz with an unevenness of no more than 3 dB, an amplitude range (with connection of serial generators) - in the range from 10 to m, a range of signal durations - in the range from 0.5 up to 5 µs with the following frequency from hertz fractions up to 100 kHz (set from serial generators) with non-uniformity of frequency response less than 1 dB.

By making the plate less than a quarter of a wavelength thick and matching the specific acoustic 11: their resistances of the plate, cylinder and tread materials, the input acoustic impedance of the device from the working area of the tread is constant over a wide frequency range and frequency response of the electroacoustic conversion of the plate m is uniform in this wide frequency range. The increased area of the plate compared to the area of the working platform makes it possible to shift the frequencies of parasitic radial oscillations below the operating frequency range and more effectively suppress them, since the area of the outlet of these oscillations in the measure body increases along the propagation path (the amplitude of radial oscillations decreases proportional to the radius of the plate). Reducing the thickness of the radiating

piezoplates on its edges, for example, a bevel at an angle of 40-45, also reduces the effect of radial oscillations on the frequency response of the device. The implementation of a plate with a variable size in the plane eliminates the strong frequency expression of the radial oscillations. Polarizing the plate only along its central part, which is equal to the working platform, allows reducing the energy of oscillations emitted into the cylinder, which reduces the error due to interference effects. The arrangement of the piezorescence plate in close proximity to the working platform increases the signal-to-noise ratio.

The use of a piezo sensor allows you to notice and eliminate possible erroneous changes in time. Order 1180/39

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reni. A conical depression, for example, half the height of the cylinder, dissipates the ultrasonic vibrations that enter the cylinder in the direction of the absorbing layer. Circular grooves with a minimum depth of the first groove, not exceeding half the wavelength of the upper part of the working range, allow diffuse scattering of surface and subsurface oscillations into the cylinder body.

Claims (1)

Invention Formula A device for calibrating piezo receivers of acoustic emission signals comprising a plate made of piezoelectric material, an electrically connected generator, a solid cylinder acoustically connected to one of the ends of the plate, and a layer of material that absorbs acoustic vibrations applied to the lateral surface of the cylinder. in order to extend the functionality and accuracy of the calibration, it is equipped with an electrically conductive protector acoustically connected with the free surface of the plate and designed to to accommodate a calibrated piezo receiver, a piezo sensor with a resonant frequency equal to the center frequency of the operating frequency range, installed on the lateral surface of the cylinder, a control signal processing unit electrically connected with the piezo sensor, the plate is made ellipsoid with a bevelled edge and thickness not greater than a quarter of the acoustic wavelength at the upper frequency of the working frequency range, the central circular part of the plate is polarized, the diameter of the cylinder exceeds the maximum size The plate, on the free end surface of the cylinder, is an axially symmetric conical recess, and on the opposite end surface of the cylinder, limited by its outer diameter and the plate contour, circular grooves are made with a gradual increase in their depth in the direction from the center to the outer diameter. Circulation 847 Subscription