Correlation method of processing the image of the surface microrelief to determine its roughness

Background. The analysis of the results of the use of various machines and mechanisms in the national economy has shown that the roughness of the microrelief of their working surfaces largely determines the reliability and durability of their operation. In this regard, the study and development of modern new methods for measuring the roughness of a microrelief is an urgent task at present. Aim. The purpose of the work is to study and develop an optoelectronic method, algorithms and software for digital processing of images of microreliefs of the surfaces under study to measure their roughness directly during the technological process of their manufacture. Methods. The method is based on computer processing of images of the studied microreliefs, as a result of which the roughness parameters of these microreliefs are determined. For this purpose, two-dimensional correlation functions are calculated for halftone images of microreliefs of reference samples, with certain GOST methods and roughness parameters. For these functions, the average amplitudes Ucp of the variable components of the correlation coefficients are calculated and the analytical dependence of the GOST roughness parameter Ra on Ucp is constructed. To depict the studied microrelief with unknown roughness parameters, the variable component of the two-dimensional correlation function is also determined, and the arithmetic mean deviation of the profile from the middle line Ra is found based on the obtained dependence Ra = f(Ucp). Results. A new optoelectronic method for measuring the roughness parameters of microreliefs of machined surfaces is proposed, which is based on digital processing of their halftone images. As a result of such processing, a two-dimensional correlation function is calculated, the parameters of which serve to identify the studied microrelief and, thereby, to measure its roughness. The results of using this method to measure the surface roughness parameters of the compressor blade of a gas turbine engine are presented. Conclusion. The prospects of using the optoelectronic method and digital processing of images of microreliefs of mechanically processed surfaces in order to quickly measure their roughness parameters are shown. An algorithm for calculating a two-dimensional correlation function has been developed, which characterizes the microrelief under study and by the characteristics of which it is possible to identify it, that is, to measure its roughness. At the same time, the negative influence of side uninformative factors on the results of measuring the parameters of the microrelief, in particular, fluctuations in the power of the light flux and the angle of its incidence on the surface under study, is also eliminated. The results of the application of the developed optoelectronic method for measuring the roughness parameters of the surface areas of the compressor blade of a gas turbine engine, which are identical to the results of measuring their roughness by GOST profile methods, are presented.