SU807043A1 - Method of measuring layer thickness - Google Patents

Description

one

This invention relates to non-destructive inspection of products and. can be used when measuring the thickness of layers of multilayer objects.

A known method for measuring the thickness of a non-conducting layer located on a conductive base. When controlling the thickness of the layers of a two-layer non-conductive object, an electrically conductive layer is placed between the layers, a source of an alternating magnetic field is placed on the surface of the product and the thickness of the layer 1 is judged by the amount of applied resistance from the influence of eddy currents in the layer.

However, when implementing this method, measurement error arises due to the change in the electrical conductivity of the interlayer over the area, from the temperature change, from the non-uniformity of its conductivity over the surface.

The closest in technical essence to the present invention is a method for measuring the thickness of layers of multilayer products, which consists in the fact that, in the manufacture of a product, interlayer elements are placed between its layers, placed on one of the surfaces of the product

the inductive transducer and the magnitude of the signal of this transducer are judged on the measured thicknesses of the layers, and as interlayer

elements use a system of linear conductors, through which alternating current is alternately passed, as the measured parameter using linear magnetic field induction

 conductor with current 2.

However, the method has the disadvantage that the orientation of the magnetic field at the point of observation with its constant distance from

5, a conductor with a current is determined not only by the field of the conductor portion directly below the observation point, but is the integral sum of the fields from the adjacent portions and the entire contour.

0 The closer these sites are from the observation point, the more significant their contribution to the gender value at this point. The intensity of the field at the point in question above the conductor is not only

Claims (2)

5, its distance from the conductor, i.e. layer thickness, but also a function of the configuration of this conductor, i.e. forms of products. This leads to a significant error in measuring the thickness of the product layers, since the calibration characteristic of a device implementing a known method is different for different parts of the embedded contour with the same thickness of the layer. In addition, in the known method there is an influence of current leads on the measurement result. The purpose of the invention is to improve the measurement accuracy by eliminating the influence of product configuration. This goal is achieved by using non-ferromagnetic cylindrical tubes as interlayer elements, alternately moving a ball of electrically conductive non-ferromagnetic material along each h3 tube and fixing the extremum of the conversion signal. The drawing shows a device for implementing a method for measuring layers of multilayer products. The device contains a compressor 1 connected through a pneumatic switch 2 with non-ferromagnetic cylindrical tubes 3-6, laid between the layers 7-11 of product 12. An inductive converter 13 is placed on the surface of the product. The method is carried out as follows. Put, for example, an eddy-current converter 13, on the surface of the controlled product 12. Set switch 2 to position a, blow the electrically conductive non-ferromagnetic ball 14 through the upper tube with the help of a compressor. At the moment the ball 14 passes under the eddy current transducer 13, the magnitude of its signal Ix will reach an extreme value. The absolute value of this extremum 1 uniquely depends on the thickness of the layer Tdx. The extremal value is fixed by this value; 1 ech and a known calibration characteristic determine the value of the measured thickness Tdx. Switch 1 switch 2 to position b and repeat these operations. The magnitude of the extreme value of the signal of the converter 13 is proportional to the thickness ftx. Similar operations are performed successively to the position (Z - 1) of the switch 2. In this case, the value -1 of the signal of the converter 13 is proportional to the thickness (TOX-T .. - t h- .. . + T (g) x .. The thickness of the first layer is calculated as the difference between the previously defined thicknesses I and (-1 Seals, i.e. T, Otah-Twx ...,) - (.: (1-o) J. The method allows one to eliminate the measurement error of thickness associated with a change in the configuration of a 1 & control object, i.e. in not only plane-parallel multilayer products, but also products with a variable curvature, in the general case of an arbitrary spatial configuration. Formula of the invention A method for measuring the thickness of layers of multilayer products, which consists in placing interlayer elements between its layers in its manufacture, the surface of the product consumptive inductive transducer and the magnitude of the signal of this transducer is judged on the measured layer thicknesses, characterized in that, in order to improve the accuracy of Eren by eliminating the effect of configuration items, as items used interlayer nonferromagnetic cylindrical tubes are alternately moved along the bead of each of the tubes of electrically conductive non-ferromagnetic material and fixed transducer signal extremum. Sources of information taken into account during the examination 1. Reference Book Non-destructive testing of metals and products. Ed. G. S. Samoylovich. M., Mechanical Engineering, 1976, p. 250 2. USSR author's certificate No. 619783, G 01 B 7/06, 1977 (prototype).