SU1587324A1 - Method of checking thickness of electroconducting coating - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to measure the thickness of conductive ferromagnetic materials on ferromagnetic bases. The increase in reliability in controlling the thickness of ferromagnetic coatings on ferromagnetic bases is achieved by choosing the optimal frequency of excitation of eddy currents. The surface-mounted eddy current transducer is installed in a controlled area of an object consisting of a ferromagnetic electrically conductive base and a ferromagnetic electrically conductive coating. Using eddy current transducers excite eddy currents, the frequency F of which is chosen from the condition δ = (0.4-0.6) H cf, where H cf is the average thickness of the coating in the control range, δ is the depth of penetration of the field of eddy currents in the coating material . The maximum relative sensitivity of the applied voltage phase to the coating thickness is achieved. 1 tab.

Description

The invention relates to non-destructive testing and can be used to measure the thickness of conductive ferromagnetic materials on a ferromagnetic substrate.

The purpose of the invention is to increase the reliability in controlling the thickness of ferromagnetic coatings on a ferromagnetic base by selecting the optimal frequency of eddy current excitation.

The method of controlling the thickness of the electrically conductive coating is carried out as follows.

An in-line eddy current transducer (not shown) is installed in a controlled area of the object (not shown) consisting of a ferromagnetic electrically conductive base and a ferromagnetic solenoid conductive coating, the thickness of which is monitored and varies in the range from LM to max.

Using an eddy current transducer, eddy currents are excited, the frequency f of which is chosen from the condition (5 (0.4 - - 0.6) hcp, where hep 0.5 (hMMH + h „ax) is the average thickness of the coating in the control range, d is the depth penetration of eddy current currents in the coating material.

The penetration depth of the eddy currents of the surface-mounted eddy current transducer into the material can be estimated by the formula:

SP

sc

SA) Yu b.

d

T

l f - / go

where f is the frequency of the current feeding the excitation winding of the converter, c / o-magnetic constant,

 4 l 10 GN / m;

 - relative magnetic permeability of the material;

(7 - specific electrical conductivity, Ohm / m.

The voltage UBH introduced by the coating into the eddy current transducer is extracted, for which the voltage introduced into the eddy current transducer induced by an uncoated object into the eddy current transducer is subtracted from the eddy current transducer induced in the measuring winding.

The phase difference is determined and, based on the obtained phase difference, the thickness of the coating is determined, the phase of the reference voltage is recommended to be set equal to the UBH phase on the sample with thickness Lmin of the coating.

The optimality of the chosen ratio is confirmed by experimentally obtained data on the change in the ratio

body sensitivity D00 - in

 Ah

dependence on relative depth

penetrations d / h, where Ah is the change in the thickness of the coating, A (D) is the change in the phase difference between the reference and applied voltages, and. The change in the sensitivity of the control of Au9 coating thickness depending on the relative depth of penetration of electromagnetic

The waves in the coating material b are listed in the table.

Claims (1)

Invention Formula The method of controlling the thickness of the electrically conductive coating, which consists in installing an invoice eddy current transducer in a controlled area of the test object, excites eddy currents, isolates the voltage applied by the coating, determines the phase difference between the reference voltage and the applied voltage and phases are determined by the thickness of the coating, characterized in that, in order to increase the reliability in controlling the thickness of ferromagnetic coatings on a ferromagnetic base, the frequency f of the excited eddy currents is chosen ayut of conditions d (0.4-0.6) hep, where d is the depth of penetration of the eddy current field in the coating material, hep is the average coating thickness in the control range.