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The article presents the results of a study of the effect of the functional relationship between the parameters of the microgeometry of the brake disc surface and the level of the stress-strain state of the contact area on the thermal resistance coefficient. The results of an experimental study of the process of changing the step and altitude parameters of the microgeometry of the surface of the brake disc under the influence of normal and tangential forces realized during friction are obtained. It was found that under the influence of normal and tangential forces, the height parameters of the microgeometry tend to increase, and the step parameters tend to decrease. It is shown that when calculating the contact thermal resistance, it is necessary to take into account the functional relationship between the geometric parameters of the microroughness of the brake disc surface and the level of the stress-strain state of the contact area. The calculations performed without taking into account this connection lead to overestimated values of the contact thermal resistance and, accordingly, to errors in determining the values of heat fluxes passing through the contact area of the mating surfaces. The values of the constants, which depend on the design features of the friction unit of the disc brake and are used to determine the nature of the change in the geometric features of microroughnesses, have been specified. The correction of the input parameters of the microgeometry of the surface of the brake disc is performed, taking into account the dynamics of changes in their geometry under the influence of force loading. It is shown that it is advisable to take into account the dynamics of changes in the surface microgeometry in the analytical determination of the contact thermal resistance of a disc brake. The results obtained are recommended to be used in calculating the friction characteristics and assessing the heat fluxes passing through the area of mutual contact of the brake disc and brake pads of the disc brake.

The article discusses the thermal state of the disc brake elements during braking, taking into account the distribution of heat fluxes between the friction elements. The results of the study of the influence of the thermal resistance of the medium filling the microcontact gaps, caused by reversible deformations of the surface microgeometry, on the thermal state of the disc brake elements are presented. Method - the description of the thermal state of the disc brake elements during braking is made on the basis of the Fourier - Kirchhoff differential equation of thermal conductivity, taking into account the influence of the thermal resistance of the medium filling the microgaps between the surfaces of the brake pad and the brake disc. Results of the work: The calculation of the thermal state of a railway disc brake was carried out taking into account the reversible deformations of the microgeometry of the surfaces of the working elements of the disc brake. The exact dimensions and shape of the disc brake elements are specified in the CAD system (SolidWorks). The graphs of changes in the thermal energy generated and dissipated by the disc brake at different initial speed and duration of braking are given. The obtained dependences illustrate the process of heat energy dissipation into the environment. The inertia of the friction system of the disc brake in relation to the dissipation of the generated thermal energy during braking is shown. It has been shown that the distribution of heat fluxes between the working elements of a disc brake depends on the level of reversible deformations of the microgeometry of the brake disc surface, which directly determine the thermal resistance of the medium filling the microcontact gaps. Taking this circumstance into account makes it possible to increase the reliability of calculations of the generated and dissipated energy by the working elements of the disc brake during braking. The results of the study are recommended for use in calculating the thermal state of the working elements of the disc brake during braking.

The article is devoted to the experimental study of the force interaction of the working elements of a disc brake in order to establish the dependence of the coefficient of static friction, taken as a criterion for the potential frictional properties of the friction unit, on the pressing force of the brake linings to the brake disc and the coefficient of mutual overlap. The experiments were performed on a full-scale stand, the basis of which is an electric drive with a power of 75.0 kW and a full-scale disc brake of the LT-10 tram. The stand allows to measure the static friction force under conditions of real forces, pressures, geometry of the contact area, as well as the coefficient of mutual overlap. TR119 and UT22-B were taken as friction materials for brake linings, in the first of which, according to the characteristics declared by the manufacturer, the coefficient of friction decreases with increasing temperature, in the second it increases. During the experiments, these materials worked in a pair of friction with the material steel 35, from which the brake disc is made. The experimental results were processed using the methods of mathematical statistics and presented in graphical form. It is shown that in the range of loads realized during braking, the stress-strain state of the contact area of the working elements of the disc brake according to the criterion of microstrains corresponds to an unsaturated elastic contact. This type of contact is typical for the studied overlap coefficients (0,33; 0,66; 0,98). It was found that with an increase in the pressing force of the brake linings to the brake disc, the static friction coefficient tends to decrease, and with an increase in the overlap coefficient, an increase in the static friction coefficient is observed for all specified values of the pressing force. At the same time, the UT22-V material is characterized by lower values of the coefficient of static friction compared to the TR119 material. Field of application of the results: development and design of advanced designs of disc brakes.