METHODOLOGICAL FOUNDATIONS OF THE MATERIALS SCIENCE ASSESSMENT OF THE QUALITY OF LUBRICANTS FOR LOADED INTEGRATIONS OF MACHINES AND MECHANISMS. MESSAGE 1. THE INFLUENCE OF THE MEDIUM ON THE STRESS-STRAIN STATE AND STRUCTURAL CHANGES IN THE ZONE OF CONTACT DEFORMATION OF METALS DURING FRICTION

The experimental and theoretical foundations of the material science approach to the assessment of lubricants are described. This approach is based on the analysis of the complex of structurally sensitive properties of antifriction material in the tribodeformation zone and aimed at identifying the significant role in the process of interaction of lubricants with the friction surface. The rheological properties of the surface layer formed in the tribo material under conditions of contact deformation and by the action of a lubricating medium determine the conditions for the formation of a wear-resistant structure. The concepts of the physical-chemical bases of the action of the medium in relation to the problems of elasticity and sliding contact are formulated, describing the behavior of surface-modified materials in the simplest stress-strain states. It is shown that when a surface-hardened material, the residual stresses within external layer are in agreement with the loading stresses, while in the inner volume zone they are opposite to them. The distribution of residual stresses in a surface-hardened sample turns out to be the reverse of the case of a plasticized material. The distribution of residual stresses in a surface-hardened sample turns out to be the reverse of the case of a plasticized material. Schematic diagrams of residual stresses arising in the near-surface formation of the material as a result of its elastic-plastic deformation during tribocontact action in a surface-plasticizing and surface-hardening lubricating medium, are presented. It is shown that in the surface-plasticized near-surface formation, residual stresses are compressive in nature, and in the surface-hardened layer they are tensile. There is a sharp change in the direction of residual stresses between layers at their boundary. The stress distribution over the depth of the material is qualitatively similar to the corresponding schematic diagrams obtained for cases of torsion and bending. Based on the calculation of the diagrams of the components of the residual stress tensor arising in the surface layer of the antifriction material during sliding friction, the conditions for the implementation of the plasticizing and strengthening triboeffect, are shown. It is also shown that among industrial aluminum bronzes, BrA5, BrA7 have the highest wear resistance in surfactants.

antifriction alloys, boundary friction, surfactants, microstructure, residual stresses, contact deformation, friction, wear, wear-resistant structure