RU2604094C1 - Uhf method of irregularities detecting in dielectric coatings on metal substrate - Google Patents

Abstract

FIELD: metal processing.

SUBSTANCE: invention relates to electrophysical and geometrical parameters irregularities determining method of dielectric and non-magnetic coatings on metal surface and can be used for quality control of hard coatings on metal during development and operation of nonreflecting and absorbing coatings, as well as in chemical, paint and coatings and other industries. Said technical result is achieved by fact that in known UHF method of irregularities in dielectric coatings on metal substrate detecting, consisting in creation of slow surface E-wave electromagnetic field above dielectric coating on electrically conductive substrate, followed by recording changes in parameters, characterizing high-frequency field, in calculation of attenuation factor of α slow surface E-wave field intensity in normal plane relative to its propagation direction in spaced points and determining irregularities boundaries, preliminary measuring actual part of dielectric permeability ε′ and thickness b of reference sample coating, by which determining slow surface E-wave field intensity attenuation factor threshold value α₀, wherein comparing in each measurement point of scanned coating surface current value of surface slow wave α field intensity attenuation factor with attenuation factor threshold value α₀, and if α<α₀, then making decision on presence of coating d delamination in given point.

EFFECT: technical result is higher probability of irregularities detecting due to determining of slow surface E-wave field intensity attenuation factor threshold value of with regard to analyzed coating individual characteristics.

1 cl, 1 dwg

Description

The present invention relates to methods for determining the heterogeneity of the electrophysical and geometric parameters of dielectric and magnetodielectric coatings on a metal surface and can be used to control the quality of hard coatings on a metal during the development and operation of non-reflective and absorbing coatings, as well as in chemical, paint and varnish and other industries.

The closest in technical essence to the proposed invention (prototype) is a microwave method and localization of inhomogeneities magnitodiehlektricheskih dielectric coatings on metal and to assess their relative magnitudes [Patent RU №2256165, IPC ⁷ G01N 22/02, G01R 27/26, appl. 09/01/03. Publ. 07/10/05. Bull No. 19], which consists in creating an electromagnetic field of a slow surface E-wave above a dielectric coating on an electrically conductive substrate and then recording changes in the parameters characterizing the high-frequency field, calculating the attenuation coefficient α of the field strength of the slow surface E-wave in a normal plane relative to its propagation direction in spaced points and the subsequent determination of the boundaries of heterogeneity.

The disadvantages of this method is the low probability of detecting inhomogeneities, due to the fact that the choice of the threshold value of the attenuation coefficient of the field strength of the slow surface E-wave, which is used to detect inhomogeneities, is performed by the operator performing the measurements.

The technical result of the invention is to increase the probability of detecting inhomogeneities by determining the threshold value of the attenuation coefficient of the field strength of the slow surface E-wave as applied to the individual characteristics of the coating under study.

The specified technical result is achieved by the fact that in the known microwave method for detecting inhomogeneities in dielectric coatings on a metal substrate, which consists in creating an electromagnetic field of a slow surface E-wave above a dielectric coating on an electrically conductive substrate and then recording changes in the parameters characterizing the high-frequency field, calculating the attenuation coefficient α field strength of a slow surface E-wave in a normal plane relative to its direction neniya at spaced apart locations and determining inhomogeneities boundaries previously measured real part of the dielectric constant ε ', and a thickness b of the reference coating sample, which define the threshold value of the attenuation coefficient field a slow surface E-wave α ₀ is compared scanned surface coating in each measurement point current value of the field intensity attenuation coefficient of the surface of the slow wave with the threshold value α attenuation coefficient α _0, and if α <α _0, then the received mayutsya decision on the presence coating exfoliation d at a given point and its value is calculated,

- волновое число свободного пространства; $$k_1=\sqrt{\frac{2\pi }{{\lambda }_{г}}}\sqrt{\epsilon \text{'}}$$

- волновое число в слое исследуемого покрытия; λ_г - длина волны СВЧ-генератора, ε′ - действительная часть диэлектрической проницаемости исследуемого покрытия, b - толщина слоя исследуемого покрытия.where α is the current value of the attenuation coefficient of the field strength of the surface slow E-wave,

- wave number of free space; $$k_{\mathrm{one}}=\sqrt{\frac{2\pi }{{\lambda }_g}}\sqrt{\epsilon \text{'}\text{'}}$$

- the wave number in the layer of the investigated coating; λ _g is the wavelength of the microwave generator, ε ′ is the real part of the dielectric constant of the studied coating, b is the thickness of the studied coating layer.

The invention consists in the following. In the prototype value of the threshold attenuation coefficient α _threshold field strength slow surface E-waves selected by the operator who performs the measurement, excluding electro coating parameters (dielectric constant ε 'and thickness b), which ultimately reduces the probability of correct detection of irregularities therein. The proposed method, in contrast to the prototype, allows to increase the probability of the correct detection of inhomogeneities due to the fact that the threshold value of the attenuation coefficient of the field strength of the slow surface E-wave α _{0 is} calculated in relation to the individual characteristics of the studied coating according to the measured values of the dielectric constant ε ′ and thickness b reference coating sample.

The figure shows one of the possible embodiments of the proposed microwave method for detecting inhomogeneities in dielectric coatings on a metal substrate, where the numbers indicate 1 - measuring receiver, 2 - comparison circuit, 3 - unit for calculating the peeling value of the coating, 4 - unit for determining the threshold value of the attenuation coefficient of tension field of the surface wave slow - α _0, 5 - an input unit of the test parameters covering, 6 - unit of measurement of the real part of permittivity ε 'and this thickness b onnogo coating.

Assignment of circuit elements.

The measuring receiver 1 is inherent in the analogue (prototype) and includes a system of receiving vibrators, a mechanism for their movement and a unit for calculating the current value of the attenuation coefficient α of the field strength of the surface slow E-wave.

Comparison scheme 2 is inherent in the analogue (prototype) and compares the current value of the attenuation coefficient α of the field strength of the surface slow wave with a threshold value of α ₀ .

The unit for calculating the amount of peeling of the coating 3 is designed to determine from the real part of the dielectric constant ε ′ and the thickness b of the investigated coating the amount of peeling of the coating d at a given measurement point according to formula (1). Block 3 can be implemented based on the ATmega2560 microcontroller [ATmega2560. Datasheet [Electronic resource] URL: http://www.atmel.com/Images/Atmel-2549-8-bit-AVR-Microcontroller-ATmega640-1280-1281-2560-2561_datasheet.pdf. (Date of treatment: 10.1 01.2015)]. Expression (1) is calculated using a subroutine that is loaded into the microcontroller of block 3.

The unit for determining the threshold value of the attenuation coefficient of the field strength of the surface slow E-wave 4 is intended to determine the threshold value of the attenuation coefficient α ₀ from the measured values of the real part of the dielectric constant ε ′ and the layer thickness b of the reference sample. The threshold attenuation coefficient α ₀ can be determined, for example, by solving a transcendental equation for determining the attenuation coefficients of E-type surface waves [formula (2.21), p. 79 [Fedyunin P.нин., Kazmin A.I. Methods of radio wave control of the parameters of protective coatings of aircraft. M .: Fizmatlit. 2013]. The solution to this equation can be implemented using a program that is loaded into block 4, while it can be implemented on the basis of the microcontroller ATmega2560 [ATmega2560. Datasheet [Electronic resource] URL: http://www.atmel.com/Images/Atmel-2549-8-bit-AVR-Microcontroller-ATmega640-1280-1281-2560-2561_datasheet.pdf. (Date of treatment: 11/10/2015)].

The input unit for the parameters of the test coating 5 is intended to record the values of the real part of the dielectric constant ε ′ and the thickness b of the test coating in block 3. This block can be implemented, for example, on the basis of a matrix keyboard. It is connected to the microcontroller of the unit for calculating the coating peeling value 3 [Connection of the matrix keyboard to the AVR microcontroller [Electronic resource] URL: http://radioparty.ru/prog-avr/program-c/455-lesson-matrix-keyboard (Date of access: 11/10/2015)].

The purpose of the unit 6 for measuring the real part of the dielectric constant ε ′ and the thickness b of the reference coating 6 follows from the name of the block itself. In this case, block 6 can be implemented, for example, on the basis of the radio wave method of surface electromagnetic waves and using the measuring and computing system of radio wave control, which implements it [Fedyunin P.A. Kazmin A.I. Methods of radio wave control of the parameters of protective coatings of aircraft. M: Fizmatlit. 2013. S. 143-151].

The scheme works as follows. Before starting measurements of the test coating, the actual part of the dielectric constant ε ′ and the thickness of the layer b of the reference coating sample are measured using block 6.

Using the measuring receiver 1, the current value of the attenuation coefficient α of the field strength of the surface slow E-wave of the test coating is determined.

The current value of the attenuation coefficient α of the field strength of the surface slow E-wave of the test coating is fed to the first input of the comparison circuit 2, the second input of which receives the threshold value of the attenuation coefficient α ₀ .

If α <α ₀ , then decide on the presence of peeling of the coating d at a given measurement point and calculate its value in the unit for calculating peeling of the coating 3. The values of the real part of the dielectric constant of the test coating ε ′ and its thickness b are recorded in block 3 using the input unit parameters of the investigated coating 5.

If α≥α ₀ , then the exfoliation d is taken equal to zero d = 0.

The value of the peeling value d of the coating for each measurement point is stored and an array of peeling of the coating d is formed. The distribution d over the surface of the coating shows the detected inhomogeneities and their boundaries.

Thus, the proposed method allows to increase the probability of detecting inhomogeneities of the coating due to the fact that the threshold value of the attenuation coefficient of the field strength of the slow surface E-wave is determined in relation to the individual characteristics of the studied coating.

Claims (1)

The microwave method for detecting inhomogeneities in dielectric coatings on a metal substrate, which consists in creating the electromagnetic field of a slow surface E-wave above a dielectric coating on an electrically conductive substrate and then recording changes in the parameters characterizing the high-frequency field, calculating the attenuation coefficient α of the field strength of the slow surface E-wave in normal plane relative to its direction of propagation at spaced points and determining the boundaries of heterogeneities, tlichayuschiysya in that the pre-measured real part of the dielectric constant ε ', and a thickness b of the reference coating sample, which determine the threshold value of attenuation coefficient field intensity of slower surface E-wave α ₀ is compared at each measurement point scanned surface coating current attenuation field intensity ratio surface slow wave α with a threshold value of the attenuation coefficient α ₀ , and if α <α ₀ , then decide on the presence of delamination of the coating d in given point and calculate its value,

,
where α is the current value of the attenuation coefficient of the field strength of the surface slow E-wave,

- wave number of free space;

- the wave number in the layer of the investigated coating;

is the wavelength of the microwave generator, ε ′ is the real part of the dielectric constant of the studied coating, b is the thickness of the studied coating layer.

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