RU2457479C1 - Protector for electromagnetic-acoustic transducers - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: protector for electromagnetic-acoustic transducers is in form of a collection of three or more ceramic plates, wherein end faces of neighbouring plates adjoin each other or are a small distance from each other, and are connected to each other by a sufficiently flexible material having lower specific conductivity than the collection of ceramic plates on the side facing the control object, forms a flat or cylindrical surface having radius of curvature which satisfies the condition R≥d/2, where d is the minimum outer diameter of the control object, and characteristic dimensions of the ceramic plates are selected based on geometric parameters of irregularities of the control object in the range of 2-12 mm, wherein the thickness of the ceramic plates at their thickest point is in the range of 0.1-3 mm.

EFFECT: high service durability of the electromagnetic-acoustic transducer.

5 cl, 3 dwg

Description

The invention relates to the field of non-destructive testing and can be used for ultrasonic testing of sheet, long products and pipes.

Known electromagnetic-acoustic transducer on an "air cushion", including, in particular, a magnetic system that allows you to control the magnetic field in the zone of excitation and reception of elastic waves, an electromagnetic coil, a hub made in the form of a permanent magnet, covered by an electromagnetic coil, a substrate, an inductor and a tread made in the form of one solid ceramic plate located in the area of the inductor. It is assumed that this plate is equally thick and localized in the zone of the inductor as a separate element and its surface from the side of the control object is at the same level with the substrate [1].

An electromagnetic-acoustic transducer is known in which an inductor in the form of a symmetrical flat coil resembling a butterfly is very often used to excite and receive ultrasonic waves along the normal to the surface of the test object. It is assumed that the inductance coil (inductor) is glued onto the tread, for example, on one solid ceramic plate and, therefore, its peripheral parts are approximately equal to the distance from the control object, as is the working part of the inductance coil [2].

Known electromagnetic acoustic transducer containing an electromagnetic coil, magnetic core, substrate and inductor glued to a ceramic plate. However, as in the well-known invention [1, 2], it is assumed that the inductor is glued to one solid flat ceramic plate parallel to the working surface of the substrate, and, therefore, such a ceramic plate and inductor are approximately equal to the distance from the control object [ 3].

Common disadvantages of the known electromagnetic-acoustic converters (EMAT) [1, 2, 3] are:

a) the execution of the tread from one solid ceramic plate parallel to the working plane of the substrate of the electromagnetic-acoustic transducer, and the location of the extreme turns of the inductors on the same level as the working turns located under the hub;

b) unreliable protection of the inductance coils and in general the working surface of the substrate from mechanical damage when EMAT contacts the surface of the test object.

These shortcomings significantly affect the quality of ultrasonic testing of materials and products and contribute to frequent damage and destruction of ceramic plates and inductors glued to them when the substrate contacts metal particles and scale located on the surface of the test object

The tread is an important element of EMAT and serves to protect active elements from mechanical or electrical damage during ultrasonic testing. As a rule, this is a thin plate made of a dielectric material. This plate may have a variable thickness.

Treads implemented in the well-known inventions [1, 2, 3], made of ceramic, have high abrasion resistance, but are brittle, poorly withstand impact from the control object.

EMAT protectors can be made in principle from any dielectric material, including plastic or composite materials. These protectors withstand shock loads, but are easily damaged by the uneven and rough surface of the test object.

The aim of the invention is to increase the operational stability of EMAT due to the use of a tread that has ceramic properties in terms of high abrasion resistance and at the same time withstands shock loads.

This goal is achieved in that the protector for electromagnetic-acoustic converters that protects active elements, including inductors and contains ceramic plates mounted in the housing or substrate of electromagnetic-acoustic converters, is made in the form of a combination of three or more ceramic plates, moreover the ends of adjacent plates are adjacent to each other, or are located at a small distance from each other and are interconnected using a sufficiently flexible material having a bottom specific electrical conductivity, and the set of ceramic plates on the side facing the test object forms a surface of flat or cylindrical shape with a radius of curvature satisfying the condition R≥d / 2, where d is the minimum outer diameter of the test object, and the characteristic dimensions of the ceramic plates are selected with taking into account the geometric parameters of the irregularities of the control object from the range of 2-12 mm, while the thickness of the ceramic plates in their thickest place is 0.1-3 mm.

In order for the sharp elements of the uneven, rough surface of the test object not to destroy, not to scratch the tread, not to “tear out” ceramic plates from it, the latter should be significantly larger than the characteristic dimensions of the irregularities on the surface of the controlled material (sheet and long products). Therefore, the characteristic dimensions of the ceramic plates (for example, the diameter or sides of the rectangle for the plates, respectively, made in the form of a disk or a rectangular shape) are selected from a range of 2-12 mm.

Since the effectiveness of EMAT decreases significantly with increasing distance between the active elements and the control object, the tread thickness is always a compromise between its protective properties and the required control sensitivity. Based on this, the maximum thickness of ceramic plates is 0.1-3 mm.

Achieving the goal is also facilitated by the fact that ceramic plates are glued to a larger base plate with low electrical conductivity, and the space between the ceramic plates is filled with a binder. The shape of this base plate is roughly consistent with the shape of the test object. In this case, the shape of the surface formed by ceramic plates will automatically be matched with the object of control as well.

The goal is also achieved in the case when ceramic plates are integrated into a plate or an element of an EMAT body made of plastic and forming a single monolithic block with it.

The goal is also achieved by the fact that ceramic plates in the peripheral regions have thinning, so that the thickness of the ceramic plates in the peripheral regions is less than its value in their central regions. This contributes to a stronger fixation of ceramic plates in the material surrounding them. When the tread bends, hits it from the side of the control object, the risk of “falling out” of ceramic plates will be minimal.

Achieving the goal is also facilitated by the fact that the ceramic plates are made in the form of a single or biconvex lens. This form provides not only excellent fixation of the plates in the surrounding material, but also the absence of aggressive tread on the controlled material. With partial tread wear, rounded ceramic elements will not scratch the surface of the test object. From a technological point of view, the symmetrical shape of biconvex lenses allows them to be embedded in the surrounding material, without worrying about the preliminary orientation of the plates in the manufacture of the tread.

As the surrounding material, plastic, rubber or any plastic compound can be used. Ceramic plates can also be glued into a pre-drilled dielectric plate.

Figure 1 shows an example of a tread with a thickness of 0.5 mm with embedded ceramic "lenses" with a diameter of 5 mm. Such a tread will be matched in shape with a flat or almost flat control object, for example, with a pipe whose diameter significantly exceeds the characteristic size of the active element protected by the tread.

Figure 2 shows an example when ceramic plates are glued to a base substrate.

Figure 3 illustrates an example when a tread in the form of a set of ceramic plates interconnected by a plastic base is integrated in an element of the EMAT housing.

It can be seen from the above examples that ceramic plates can have various shapes and are interconnected in various ways.

The destruction of one of the plates, for example, as a result of a concentrated shock load, does not automatically lead to the destruction of the remaining plates and the tread as a whole, as is the case if the tread is made of a monolithic ceramic plate. In addition, the relatively small size of the plates that make up the tread, as well as the presence of an elastic bond between them provide a significantly greater tread resistance to impacts from the control object. Moreover, the resistance of the composite tread to abrasion is at the level provided by the monolithic tread plate.

Description of drawings

Description of the tread (s) for electromagnetic acoustic transducers (EMAT)

The tread 1, according to figure 1, contains cylindrical ceramic plates 2, the characteristic dimensions of which are selected taking into account the geometric parameters of the irregularities of the test object (OK) from a range of 2-12 mm, while the thickness of the ceramic plates 2 in their thickest place is 0, 1-3 mm. Ceramic plates 2 are integrated, "poured" into the plastic 3 and form a monolithic block 4. This block can have a more complex shape and also serve as an EMAT body 5 or an element of its body, for example, substrate 6.

The tread 7, according to figure 2, for example, rectangular ceramic plates 8, which are glued to the base 9, defining the shape of the tread 7 and mechanically connecting the ceramic plates 8 into a single monolithic block 10. This block 10, as in the previous case, may have more complex shape and also serve as an EMAT body 5 or an element of its body, for example, a substrate 6. The space between the plates is filled with a binder material 11, for example, plastic 3 or epoxy compound 12.

The tread 13, according to figure 3, is made as an element of the EMAT housing 5 and is matched in shape with a cylindrical control object (OK), and in the peripheral zones there are places of thinning of ceramic plates 14.

Information sources

1. RF patent No. 2300762.

2. RF patent No. 2268517.

3. RF patent No. 2270443.

Claims (5)

1. The tread for electromagnetic-acoustic converters that protects active elements, including inductors and contains ceramic plates mounted in the housing or substrate of electromagnetic-acoustic converters, characterized in that it is made in the form of a combination of three or more ceramic plates, the ends of adjacent plates are adjacent to each other or are located at a small distance from each other and are interconnected using a sufficiently flexible material having a low specific electrical conductivity, moreover, the set of ceramic plates on the side facing the test object forms a flat or cylindrical surface with a radius of curvature satisfying the condition R≥d / 2, where d is the minimum outer diameter of the test object and the characteristic dimensions of the ceramic plates are selected taking into account the geometric parameters of the irregularities of the test object from a range of 2-12 mm, while the thickness of the ceramic plates in their thickest place is 0.1-3 mm. 2. The tread according to claim 1, characterized in that the ceramic plates are glued to a larger base plate made of a material with low electrical conductivity, and the space between the plates is filled with a binder material, the shape of this base plate being approximately consistent with the shape of the test object . 3. The tread according to claim 1, characterized in that the ceramic plates are integrated into the housing or an element of the EMAT housing made of a material with low electrical conductivity, such as plastic, and forming a monolithic block with it. 4. The tread according to claim 1, characterized in that the ceramic plates in the peripheral regions have thinning. 5. The tread according to claim 1, characterized in that the ceramic plates are made in the form of a single or biconvex lens.

Images