CRACKING PROCESS UNDER ELECTROTHERMECHANICAL FRICTION INTERACTION IN FRICTION PAIRS (PART 1)
DOI:
https://doi.org/10.18372/0370-2197.4(97).16955Keywords:
test stand, friction couple, frictional contact, inter-contact volume, gap effect, cracking processAbstract
The materials of the article refer to the testing technique used to study the processes of tribocracking of friction pairs. These processes are accompanied by the release of gas-vapor mixtures and water, which, at high temperatures exceeding the allowable for polymer lining materials, intensify hydrogen wear of the working elements of the friction pairs. At the same time, it was established that the gas dynamics in the intercontact space of friction pairs has a complex character, which, depending on the friction modes and mechanical-physical-chemical properties of the surface of the materials FK-24A - 35KHNL steel, for which the operational parameters fluctuate in a wide range of their changes . Excess pressure prevents migration in the intercontact space of the environment and creates conditions for the formation of film starvation zones. A stand was developed and created for researching tribocracking processes during frictional interaction in metal-polymer friction pairs, taking into account the influence of various factors on their occurrence in the upper layers of friction linings. At the stand, a sample of FK-24A friction material weighing 125 g was examined for the cracking process of its upper layer using thermogravimetric and differential thermal analysis methods. Thermal destruction of the sample began at a temperature of 300°C with a calculated activation energy of 85.5 kJ/mol. At the same time, the surface layer of the sample disintegrated for about 15 minutes at a temperature of 400°C. The amount of water that ended up in the measuring tube of the vacuum pump was 35.4 ml. Oxidative processes prevailed up to a temperature of 320°C, and then reducing processes began to appear; inert gases acted as moderators of chemical reactions. It was found that the energy load of the discrete contact of the microprotrusions of the metal-polymer friction pairs, taking into account the electric, thermal and chemical fields up to and above the permissible temperature for the upper layers of the polymer coating during oxidation-reduction processes, significantly affects the dynamic coefficient of friction and the intensity of wear of the polymer coating.
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