A.A. Yevtushenko

Some Methods for Calculating Temperature During the Friction of Thermosensitive Materials

The thermal problem of friction for two semi-infinite bodies, with the dependence of their thermal properties on the temperature taken into account, is considered. It is assumed that a specific power of friction is constant and that a thermal contact between semi-spaces is imperfect. As a consequence of the latter assumption, the linearization of a corresponding boundary-value heat conduction problem using the Kirchhoff transformation is incomplete. Depending on the type of nonlinearity of friction body material—simple or arbitrary—the various methods of linearizing the final task are suggested. The effectiveness of these methods is illustrated by the numerical analysis of the friction materials for couples with a linear or nonlinear temperature dependence on coefficient of thermal conductivity and specific heat.

Effect of thermal sensitivity of materials of tribojoint on friction temperature

An analytical solution of a friction-heat problem for two semi-infinite solids taking into account the temperature dependence of their thermal characteristics has been obtained. It is assumed that the specific power of friction is constant and the thermal contact of the solids is imperfect. Because of the latter assumption, the linearization of the corresponding boundary heat conduction problem carried out using the Kirchhoff transform has turned out to be incomplete. Two methods for the final linearization of this problem have been proposed, i.e., the expansion of the nonlinear function in a power series, followed by the retention of only two first terms in it, and the use of linearizing multipliers. A numerical analysis for the materials with linear dependences of the thermal conductivity and the specific heat on the temperature is carried out.

Effect of dimensions of pad and disk on the temperature and duration of braking

A solution to the axisymmetric nonstationary thermal problem of friction for a disk–pad tribosystem has been obtained using the finite element method taking into account the interrelation between the temperature and velocity of sliding in the course of braking. The calculations are carried out for an FMK-11 ceramics pad and a ChNMKh cast iron disk at the coefficient of friction that depends on the temperature. The effect of the dimensions of the pad and disk on the temperature and duration of braking is studied provided that the volumes of the pad and disk remain unchanged.

Analytical model to investigate distributions of the thermal stresses in the pad and disk for different temporal profiles of friction power

The friction power is a key parameter that largely determines the value and distribution of temperature and corresponding thermal stresses in friction elements of a braking system. In this article, the influence of this parameter on the thermal stresses is under consideration. For this purpose, the exact formula was obtained to determine the normal thermal stresses, arisen due to frictional heating during relative sliding of the pad on the surface of a brake disk, for 10 selected temporal profiles of the specific friction power. Numerical analysis was carried out for a frictional couple consisting of a cast iron disk and a pad made of retinax. It is established that some temporal profiles of the specific friction power can cause the generation of the tensile stresses on the friction surface of a brake disk in a radial direction. The change of compressive stresses into tensile may indicate the initiation of the microcracks on this surface.

Modeling of the temperature regime and stress state in the thermal sensitive pad-disk brake system

An analytical–numerical nonlinear model to investigate temperature fields and thermal stresses in a pad and a disk for a single braking with a constant deceleration has been proposed. For this purpose, the boundary-value heat conduction problem for a tribosystem strip–semi-space has been formulated, which takes into account the temperature dependence of the thermophysical properties of materials. The solution to this problem has been obtained by a partial linearization through the Kirchhoff substitution, and next with a subsequent use of the method of linearizing parameters. Knowing the distribution of temperature fields in the elements of a friction pair, the thermal stresses have been established within the theory of thermal bending of plates. In this case, the temperature dependence of the Young’s modulus, Poisson’s ratio, and linear thermal expansion of the pad and disk materials have been additionally taken into account. The numerical analysis has been performed for a friction pair consisting of a titanium alloy pad and a steel disk.