SU1490455A1 - Method for measuring thickness of layers of multilayer articles - Google Patents

Abstract

This invention relates to the field of non-destructive testing. The purpose of the invention is to improve the accuracy in measuring the thickness of electrically conductive products. Increased accuracy is achieved by eliminating the effect on the measurement result of eddy currents induced in the product layers. To do this, a constant current is passed through the circuits formed by the conductors placed between the layers, the transmission time of which exceeds the decay time of transients in the electrically conductive layers. 2 Il.

Description

one

(21) 4348695 / 25-28

(22) 12/25/87

(46) 06/30/89. Bksh. No. 24

(71) Lviv Forestry Institute

(72) B.A. Agranovsky, V.G. Brandorf, Yu.N. Kizilov and J.A. Yampols% cue

(33) 620.179.142.5 (088.8) (56) USSR Copyright Certificate No. 619783, cl. G 01 B 7/06, 1977. USSR Copyright Certificate No. 879279, cl. O 01 B 7/06, 1980.

(54) METHOD OF MEASURING THE THICKNESS OF LAYERS OF MULTILAYERED PRODUCTS (57) The invention relates to non-destructive testing. The purpose of the invention is to improve the accuracy in measuring the thickness of electrically conductive products. Higher accuracy is achieved by eliminating the effect on the measurement result of eddy currents induced in the product layers. To do this, a constant current is passed through the circuits formed by the conductors placed between the layers, the transmission time of which exceeds the decay time of transients in the electrically conductive layers. 2 Il.

with

The invention relates to non-destructive testing and can be used to measure the thickness of electrically conductive layers of multilayer products.

The purpose of the invention is to improve the accuracy in measuring the tolling of electrically conductive layers of products by eliminating the influence of eddy currents. Figures 1 and 2 show a three-layer product with various combinations of contours.

The method is carried out as follows.

Linear conductors 4 - 7 are located between the heads 1 - 3 of the product and on its outer surfaces. A surface-mounted transducer 8 of a constant magnetic field, such as ferro-Edge, is placed on the surface of the product from the side of the conductor 7. In order to create direct currents, sources of 9 ... 12 EMF of direct current are included in each of the two circuits. In this case, the magnitude of the EMF can be regulated

To compensate for the fields created by the two circuits, in the converter 8, the sources of emf are switched on so that the currents in the circuits have the directions shown in fig. and 2.

Measurement of the thickness of the layers of the three-layer inspection product is carried out as follows. The shape of a pair of circuits (Fig. D) changes the value of the EMF of one of the sources from zero to the moment when the signal of the converter becomes zero after the attenuation of transients associated with eddy currents in the layers,

ABOUT

li

by changing emf. In this position, the current ratio is measured.

Then form another combination of contours (figure 2) similarly receive the value

P hz

and determine the thickness of the layers 1-3 by the formulas

T t, - t ,; T,

T 3 tj- t4.

Hh;

t 4t 4t.

t, -; t 3 -; a-j; . a 514

Ejl-Pj - Р () Рэ (1 + Р) О

РЗ- 1

 - RO)

+ a)

In the case of the p-layer product, the conductors from the outermost one from the converter are numbered sequentially, then four are chosen: the first is the third and the -th, and the thicknesses of the layers T t –t and T t f – tj are determined by this method. Then the third and fifth conductors are chosen - the fifth and the fifth, they find Tz t, - t, and T, t, etc.

The use of alternating magnetic fields generated by alternating currents passing through the embedded conductors causes the appearance of eddy currents in the electrically conductive layers whose magnetic fields, superimposed on the magnetic fields of the embedded conductors, distort the measurement results.

The use of the method makes it possible to carry out layer-by-layer thickness gauging of large-sized products with electrically conductive psi with more accurate

five

0

five

30 5

before

ability to provide improved quality control.

Claims (1)

Invention Formula The method of measuring the thickness of layers of multilayer products consists in the fact that, in the manufacture of the product, linear conductors are placed between its layers and on both surfaces so that they are in the same plane and position the magnetic field transducer on one of the surfaces of the product the groups of four linear conductors form a pair of non-common branches of electric circuits so that the magnetic fields created by each circuit in the surface transducer are directed oppositely, in one of the circuits the pair changes The current amplitude is up to the moment when the converter signal is zero, and in this position the ratio P of the currents of the first pair of circuits is measured and fixed, another pair of circuits from the same group of four linear conductors is formed and the ratio of the currents of the second pair is measured and fixed similarly circuits determine the thickness of the layers between the linear conductors, which were used to form the first two pairs of circuits, and then all the linear conductors are used in groups of four conductors and determine the thickness of all product layers characterized in that, in order to improve accuracy when measuring the thickness of the electroconductor layers, a direct current is passed through each of the circuits of the pair, the transmission time of which the transient decay time in the electrically conductive layers passes. . L 12 FIG. it