SU1418932A1 - Wide-band focusing piezoelectric transducer - Google Patents

Abstract

The invention relates to non-destructive testing and allows to increase the device's decreasing ability. A spherically concave surface of the piezoelectric element has mutually perpendicular grooves in the shape of an isosceles triangle, whose axis of symmetry is an extension of the radius of this surface. On the surfaces of the grooves, a common electrode 5 is applied. Filling the cavity of the swings with a damping material 4 with a dielectric constant less than the permeability of the piezoelectric element ensures the elimination of the parasitic capacitance between the electrodes 5,6. The ratio from which the distance between the grooves is selected is given. 3 silt, i

Description

(L

FIG.

The invention relates to non-destructive tools and methods of control and can be used for focusing ultrasonic vibrations, as well as in ultrasound diagnostics.

The aim of the invention is to increase the resolution of ultrasound monitoring and diagnostics.

FIG. I - image of a spherical concave piezoelectric element, longitudinal section; 2 shows a spherical concave surface, side view; FIG. 3 is a diagram illustrating the principle of operation of a focusing broadband piezo

converter

one

A focusing broadband piezoelectric transducer contains a piezoelectric element 1 of variable thickness, triangular grooves 2 located on the spheically concave surface of the piezoelectric element 1, active parts 3 on a spherically concave surface between the grooves 2, damping material A, filling the cavities of the grooves 2, common electrode 5 on the side surfaces of the grooves 2, the electrode 6 on the spherically concave surface of the piezoelectric element 1; the arrows indicate the direction and structure of the electric field E between the electrodes 5 and 6.

f Focusing broadband piezo transducer works as follows.

35

45

The piezoelectric element 1, which emits only one spherically concave surface, is arranged as follows. On the spherically concave surface of the piezoelectric element I of variable thickness, mutually perpendicular triangular grooves are made (FIGS. 1 and 2). The axis of symmetry of the grooves 2 is an extension of the radius of curvature of the spherically concave surface. On the side surfaces of the grooves 2, there is a common electrode 5. The distance between adjacent grooves 2 is selected from the ratio l t / sin, where t is the width of the groove 2; 1 - the width of the active part 3 of the surface of the piezoelemg 1 between adjacent grooves 2; a / is the angle at the vertex of the triangle. The cavities of the grooves are filled with damping material 4, the dielectric constant of which

fee

much less than the dielectric constant of the material of the piezoelectric element 1. An electrode 6 is deposited on the entire spherically concave surface.

50

Q 5

0 5 Q 5

five

e

-

0

The active part 3 on the center of the spherically concave surface of the piezo-element I ensures the emission and reception of the ultrasonic wave on the acoustic axis. The use of a damping material in the cavity of the grooves 2 with a dielectric constant lower than the dielectric constant of the piezoelectric element I eliminates the parasitic capacitance between electrodes 5 and 6. In addition, filling the cavity of the grooves 2 with a damping material allows the spherically concave surface to be made. cleanliness class.

Connecting a generator (not shown) to the electrodes 5. And 6 - creates in the active parts 3 an electric field E (FIG. 3). This leads to the fact that ultrasonic waves emit only the regions of the active part 3 adjacent to the electrode 6. The side surfaces radiate into the interior of the grooves 2 and MeHbmaeTCH by damping them. If necessary, a damper may be used on its rear surface (not shown) to eliminate reverberation oscillations inside the piezoelectric element.

The choice of the width of the groove, the angle of opening of the groove, the distance between the nanometers, is determined by the need to create a uniform electric field over the spherical surface and by changing the pulse duration at the expense of a layer thickness in which the electro-acoustic conversion takes place, i.e. layer in which the electric field is concentrated.

The lines of force of the electric field (Fig. 3) are circles with the center at the base of an isosceles triangle BAD. The uniformity is fulfilled under the condition that a circle with a center at a point D of a single triangle and a radius EB passes through the same point on a spherical surface as the circle with a center at a point A and a radius AB of the adjacent triangle. From the triangle AED we get AB t / 2 sin dl2 and the distance between the grooves 1 t / / sin 0 // 2.

In order to ensure a shorter pulse duration than in a known device, it is necessary to localize the electric field in the layer,

314

smaller silt || mei; epe of thickness of the fundamental converter (thickness in the center of the pinecKort over ((spine)). The localization thickness of the electric field is determined by the size of the LV: BD (fig.Z) and is t // sin s // 2, the angular increases in resolution () take the form t 2 L sin "/ 2.

Consequently, in the proposed piezo-converter, radiation of only one sphere is provided with a graphically concave surface and a uniform distribution of the displacement amplitude on it. This provides an increase in the radial and axial resolution of the monitoring and diagnostics.

Claims (1)

Invention Formula A focusing transducer; a variable-band width broadband transducer, one of the end surfaces of which is flat and the other spherically concave with an electrode applied to it, characterized in that, in order to increase the resolution Your ability, along the entire spherically concave surface, is made mutually perpendicular grooves in the shape of an isosceles triangle, whose axis of symmetry is an extension of the radius of the spherical concave surface, a common electrode is applied to the lateral surfaces of the grooves The ciH grooves are filled with damping material, the distance 1 between the caiacs and from the center of the spherical surface to the nearest groove meets the condition t sin lr. where t is the width of the groove; al is the angle of opening the isosceles of an isosceles triangle,, 125 and the cf angle and caiawki width are chosen from conditions t g 2 L sin. "/ 2, where L is the smallest thickness of the converter in its middle.  I li - fc "  "one Ml i-l-li-) jl. 11 11 iL4-4J- t-i Jll J-