SU1376041A1 - Ultrasonic mosaic converter - Google Patents

Abstract

This invention relates to non-destructive testing. The aim of the invention is to increase the sensitivity by reducing parasitic vibrations. In the process of control, the parasitic longitudinal oscillations arising in the piezoplate 2, whose working surface is divided by grooves into n elements of the mosaic structure with insulated electrodes 1 ji and extending in the direction of the lateral surface of the extreme elements 3, and 3 mosaic structures, are extinguished using additional dampers 7, and 7 ", covering the lateral surface of the extreme elements 3, and Zr of the mosaic structure and their electrodes, and resistors 8, and 8., shunting the electrodes of elements 3, and 3, respectively, and c hundred g or between the insulated electrical g of 4, width of the outer rows of elements 3 ,, 4, and 3 and material for performing the additional dampers 7 and 7 are selected from certain conditions, 2 yl. (L

Description

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The invention relates to non-destructive testing and can be used for ultrasonic testing of sheets of welded joints, vessels and pipes of large diameter.

The purpose of the invention is to increase the sensitivity 39 by reducing parasitic vibrations.

FIG. 1 shows an ultrasonic mosaic transducer, front view in section; in fig. 2 - the same, top view.

The ultrasonic mosaic transducer includes a housing 1, a piezoelectric element (piezo-plastic) 2 placed in it, the working surface of which is divided by grooves (not shown) into n elements 3, 3 ,. . ., 3, a mosaic structure with insulated electrodes A ,, 4, .., 4 "located on them, placed on the non-working surface of the piezoplate 2, solid electrode 5, main damper 6, located contact to the solid electrode 5, additional dampers 7 and 7, covering the lateral surface of the extreme elements 3 and 3, respectively | and their electrodes 4 and 4 ,,, and resistors 8, and 8, shunting, respectively, the electrodes of elements 3 and 3. the mosaic structure, and the distance between the insulated electrodes 4, 4, ..., 4 are chosen equal to no more than half The wavelengths of the ultrasonic vibrations, the width of the extreme elements 3, and 3 "of the mosaic structure are chosen 3-5 times greater than the width of the middle elements 3,.,.,

3f ,. 1, and additional dampers 7 and 7 | made of a material with acoustic impedance equal to the acoustic impedance of the piezoelectric element,

and the attenuation coefficient is not less than three times the attenuation coefficient of the main piezoelectric element. The depth of the grooves is not less than the width of the middle elements 3, ..., 3, of the mosaic structure.

The ultrasonic mosaic transducer works as follows.

The working surface of the transducer is installed on the surface of the test product (not shown) moistened with contact liquid, applying to the electrodes 4, 4,. ..,

4, the signals from the ultrasonic oscillator (not shown), phase-shifted relative to each other, excite elements 3, 3, ..., 3,1 of the mosaic structure of the piezoplate 2. In this case, an ultrasonic field is formed in the controlled product, the directionality and the form of which depends from the law, according to which excite elements of the mosaic structure. For example, one can achieve focusing of the emitted ultrasonic vibrations. The signals received by the transducer from the monitored zone are used to determine the presence of a defect and its parameters.

With such excitation of the converter, in addition to vibrations of the piezoplates in thickness, parasitic longitudinal oscillations occur, extending in a direction parallel to the working surface, which are damped by additional dampers 7 and resistors 8 and 8 ", which prevent oscillations reflected from the lateral surface of the piezoelectric element, creating noise background.

The conditions for choosing the width of the extreme elements of the mosaic structure and the attenuation coefficients of the additional dampers were obtained experimentally.

Thus, the proposed ultrasonic mosaic converter possesses more high sensitivity due to the very small number of parasitic oscillations.

Claims (1)

Invention Formula Ultrasonic mosaic transducer, comprising a housing, a piezoplate placed therein, at least the working surface of which is divided by grooves into n elements. a mosaic structure with insulated electrodes located on them, and the main damper located in contact with the electrode of the non-working surface of the piezoelectric element, the distance between the insulated elements; Trods are chosen to be no more than half the length of the ultrasonic oscillation wave, characterized in that, in order to increase the sensitivity due to the reduction of parasitic oscillations, each extreme element of the mosaic structure is equipped with an additional fflofer, covering its side surface and electrodes and made of a material acoustic resistance equal to the acoustic resistance of the piezoplate, and the attenuation coefficient of at least three times the attenuation coefficient of the main damper, and shunt Electrodes with a resistor whose resistance value is selected ( the wound is equal to the capacitance of the corresponding element of the mosaic structure, and the width of the extreme elements of the mosaic structure is chosen 3-5 times greater than the width of the middle elements of the mosaic structure. n In. one / I 1 / I Phi22