To the question of estimation of thermal transmission through metal friction elements of band-shoe brake of drilling winches

Abstract

The article shows that the main parameter in estimating the energy load of friction pairs of braking devices is the heat transfer coefficient, with the help of which it is further possible to determine the thermal resistance and distribution coefficients of heat fluxes. Recently, works have appeared where sufficiently accurate methods for calculating the temperature in the friction zone are given, depending on the thermophysical properties of materials, energy load and contact characteristics. However, these methods do not always take into account the heat transfer through the metal friction element of braking devices, which always has a noticeable effect on the energy load of their friction pairs. It is known that when calculating the bulk temperatures in the rim of a brake winch pulley above 350 ° C, it is almost always necessary to take heat transfer into account. The latter is not related to the thermal conductivity of the materials of metal friction elements in this way as the coefficient of heat transfer through their body, since the latter is the inverse value is the thermal resistance of the thickness of the metal friction element.

Thermal problems at the modern level are solved with the help of boundary conditions of the second kind, when the heat flow is specified, which is directed at the contact boundary inside the rubbing body. With a known heat release in the contact zone, the task is to correctly determine the distribution of heat flux between the rubbing bodies.

The coefficients of heat flow distribution in the temperature range from 100 to 450 °C were varied for the metal friction element in the range of 0.531 - 0.756, for the non-metal element - 0.469 - 0.244. Due to the presence of external friction pairs of the brake, dynamic and, as a result, thermal unloading of its internal friction pairs occurs. In this regard, there is the likelihood of thermal stabilization of the rim of the brake pulley. In this case, the friction linings should work outside the zone of temperatures acceptable for their materials.

Thus, the heat transfer through the metal friction elements of friction pairs of the drawstring tape-brake brake was evaluated, which made it possible to further determine the coefficients of heat flow distribution between their working parts.