Дослідження статичного та динамічного коефіцієнта тертя між поверхнею робочих органів грунтообробних машин та рослинними рештками

Abstract

The purpose of this study was to determine the effect of moisture content in plant remains, steel grade, heat treatment of the steel, roughness and the direction of the rough surface waves upon the variation of the coefficients of static and dynamic friction between the steel and plant remains after the crops have been harvested. For the purpose of the study the conventional Inclined Plane Method was applied to determine the coefficient of static friction. The coefficient of dynamic friction was determined in consideration of the time required for the plant remains to move across the inclined plane, and the time of movement without regard to the friction force (vertical incidence time, α = 90°). As follows from the study, the coefficient of sliding (kinetic) friction between plant remains and steel is significantly different for either element of the plant remains, so that the coefficient of sliding (kinetic) friction of leaves is on average 18… 29 % greater than the coefficient of sliding (kinetic) friction of stems. Steel treatment, whereby the surface energy is abated, reduces the sliding (kinetic) friction by 5… 16 %. Gain in moisture by plant remains leads to a significant increase of the coefficient of sliding (kinetic) friction. Changes of the steel surface roughness lead to a variation in the coefficient of sliding (kinetic) friction, so that it is much greater for the polished surface by contrast with those ones with rough finish. Variations in the direction of the irregularities on the polished surface do not lead to increase of the coefficient of static and dynamic sliding friction. Therefore, in case of rough surface finish and should irregularities have the longitudinal pattern, the coefficient of static friction remains unaffected, while the dynamic one is decreased by 7...10 %. The friction conditioned by the interaction of plant remains and steel may not be described by the Amonton’s & Coulomb’s Law, since in this case the coefficient of friction between the plant remains and steel is significantly affected by the molecular component. The process of friction must be described based upon the molecular-mechanical theory of friction. The molecular-mechanical theory of friction shall be taken as a basis for description of the friction process itself.