CRACKING PROCESS UNDER ELECTROTHERMECHANICAL FRICTION INTERACTION IN FRICTION PAIRS (PART 2)
Keywords:test stand, friction pair, friction contact, inter-contact volume, gap effect, cracking process
It has been established that the driving force of endothermic and exothermic chemical reactions occurring in the upper layer of the polymer coating, as well as redox processes on the contact spots of microprotrusions of metal-polymer friction pairs, are chemical potentials that arise during electrothermomechanical frictional interaction of the working surface of the metal element of friction with the upper layer of the electrolyte and the lower layer of the electrolyte with the surface of the lining cuvette. The results of the research made it possible to establish and predict the following: the electrons formed in the electrolyte are strongly oriented and their effective dipole moment is large, which leads to the inversion of the set of currents according to the "polymer-metal" scheme; triboadsorbed gas adsorbs on the working surface of the metal, after which its chemical transformations take place; at the rate of tribosorption and triboreaction of the same order, the chemical reaction shifts towards the working surface of the metal friction element; a change in the degree of dispersion and compactness of the phases that occurs in the upper layer of the polymer coating containing amorphous and glassy substances significantly affects their chemical activity; at the same time, it is necessary to take into account the change in Gibbs energy; the change in the Gibbs energy of the surface layer of the polymer coating is related to its temperature and heat capacity, which affect the direction of the shift in the equilibrium of the chemical reaction. As a result of the study of the thermokinetic interaction of the contact spots of the microprotrusions of the working surfaces during friction in different environments and the influence of various factors on the cracking process in the upper layers of the overlays, the following was established: the effects of ion adsorption differ significantly with purely electrostatic or so-called specific (due to covalent interaction with the metal) adsorption - sorption. Its limiting case is adsorption with complete charge transfer and transition of the ion to the composition of the atom; an increase in the surface temperature contributes to an increase in the output volume of the products of endothermic reactions from the upper layer of the polymer coating, as well as the equilibrium constant, which is accompanied by the release of heat. At the same time, in accordance with the Van't-Hoff mobile equilibrium principle, elastic-plastic deformation of the microprotrusions of the working surface of the metal friction element occurs. A decrease in the surface temperature of the friction pairs contributes to the intensification of the exothermic reaction with the dissociation of the ions of the surface layer of the polymer overlay; an increase in the specific loads in the friction pair leads to a decrease in the output of gaseous products, including unsaturated carbons that combine with hydrogen, from their contact gap; at the same time, specific loads in friction pairs directly depend on their mutual overlap coefficient; to achieve the maximum rate of the conversion reaction, an excess of starting substances is required; at the same time, if the consumption of one of them is limited for operational reasons, then the increase in the initial concentration of other reagents increases the number of moles of products formed, and thereby the degree of reaction.
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