SUBSTANTIATION OF THE MATHEMATICAL MODEL OF SURFACE HARDENING BY RUNNING-IN OF CYLINDRICAL SURFACES

Abstract

The high efficiency of surface plastic deformation hardening technologies combined with their productivity and economic feasibility make them attractive for a wide range of industrial sectors. At present, modern plastic theory has not yet offered a complete solution to the problem of interaction between an elastic tool and a body subjected to elastic-plastic deformation in the case when both surfaces have arbitrary curvature. The aim of this study is to develop a mathematical model that would allow us to reasonably determine the optimal modes of surface plastic deformation of cylindrical parts at given surface finish indicators. The study showed that the roughness, feed rate, and diameters of indenter balls are interrelated. The feed rate significantly affects the condition of the machined surface. As the feed rate increases, the interval between the vertices of the micron irregularities increases, and the number of repeated presses on the same area decreases, resulting in an increase in roughness and a decrease in the depth and level of the scratch pattern.Increasing the feed rate by 15 times increases the surface roughness by two classes. In turn, the depth of the deposited layer decreased by 2.5 times, and the degree of adhesion decreased by 11 %. Thus, the analysis of the results showed the feasibility of the optimal feed rate for steel 45, which is 0.05 mm/ball. When running-in steel surfaces, an increase in load improves the peening characteristics. With increasing pressure, the surface roughness remains at Ra 0.2 µm, while the depth of the peening for steel 45 increases from 0.9 to 1.8 mm, and the degree of peening increases by 11 % on average. When ball diameters are increased, with all other conditions remaining constant, a slight decrease in surface roughness is observed, as well as a decrease in the depth and degree of peening by 48 % and 11 %, respectively. Thus, with an increase in the diameter of the balls, the surface finish class increases, but the depth and intensity of the riveted layer decreases by a small amount.