Borak K. Integrated Approach to Service Durability and Wear Resistance Enhancement of the Morking Tools of Tillage Machines

The thesis is devoted to the development of scientific foundations for increasing the durability of the tillage machine working tools, taking into account the regularities of the influence of soil and climatic conditions, design and technological parameters, operating modes, as well as storage conditions. Basing on the molecular-mechanical theory of friction, an equation has been obtained for determining the coefficient of friction between the surface of the tillage working tools and soil, considering all types of friction available in the tribological contact zone. The influence of the degree of abrasive particle fixation in the soil on the mechanism and the character of wearing of the tillage machine working tools has been theoretically and experimentally established. The coefficients of the abrasive particles shape of soils of Ukraine and its effect on the wear resistance and durability of the tillage working tools have been determined. On the basis of experimental studies, the influence of the tillage machine working tools material, its thermal treatment, roughness, and direction of irregularities on the dynamic and static coefficient of friction between the tillage tools surface and the soil substrate components has been established. It has been proved that the process of friction between the tillage tool and the soil may not be explained by Amontov-Coulomb's law, and it is expedient to describe this process from the standpoint of the molecular-mechanical theory of friction. The regularity of the influence of the plant residues presence in the soil substrate on the change of the intensity of the wearing of tillage machine working tools is established. Experimental studies of change in the surface layer properties, the formation of secondary structures in the tribological contact zone, and the intensity of the wearing of tillage machine working tools enabled defining rational materials for the production of serial V-shaped ploughshares and disk working tools of tillage machines with increased durability. It has been established that the application of a wear-resistant coating can significantly enhance the durability (by 1.07–2.14 times) and wear resistance (by 1.13–3.13 times) of the tillage machine working tools. The basic principles of enhancement of service durability of tillage working tools through the integrated approach of adaptation of their wear resistance have been formulated, which allow to enhance the durability of tillage machine work tools in 1.84–2.51 times depending on the type of tillage working tool and soil and climatic conditions. An economic evaluation of the enhancement of durability of the tillage machine working tools through the integrated approach to adapting their wear resistance with taking into account soil and climatic conditions and operation modes demonstrated cost saving in the range of 6–18 % of a cost of a new machine within the term of exploitation of one set of tillage working tools.