The improvement of operational properties of the parts of means of transport by applying regular reliefs

Abstract

Problem. Specially created regular surface reliefs strongly influence the reliability and operational properties of machine parts. One of the effective methods of obtaining reliefs is cold plastic deformation (CPD). This method of modification does not lead to the occurrence of significant stresses in the material of the part and can be form-forming. The latter is important in repair production. However, to date, there is no systematic study of the formation of reliefs by CPD methods, especially with the use of linear indenters. Goal. To improve the operational properties of the parts of means of transport by applying regular micro- and macro-reliefs of technological and operational purposes by deepening linear indenters. Methodology. Press hydroficated equipment was used to create a normal indenter penetration force. The brands of typical structural materials are defined: steel, gray cast iron, bronze, brass, aluminum and titanium alloys. A linear indenter made of high-speed steel with angles at the top of 60° - 90° and a radius at the base of 0.005 - 0.5 mm was created. Methods of microstructural analysis and microhardness, standard and original instruments and devices were used. The range of groove depths was 0.02-0.5 mm. A lubricating-cooling liquid based on rapeseed oil was used. Results. It was hypothesized that when the indenter is immersed in the material of the part, the factors that have the greatest influence on the depth and other parameters of the relief groove are the normal strength, hardness, and relative elongation of the material under study. These theoretical principles formed the basis of the mathematical model of the indentation process. Originality. It was created a classification of regular reliefs by purpose: for preliminary division of the allowance during cutting; for preparing the surfaces of parts for applying coatings, including anti-friction films; to create labyrinths on the surface of parts for lubricants; for preliminary separation of fragmentary ammunition cases; to create strengthened new load-bearing surfaces, in particular, discrete when restoring worn parts; to obtain complex profiles on the surfaces of the holes of the parts. The calculation of the impact of the indentation force and the geometric parameters of the linear indenter on the shape and dimensions of the relief groove has been developed. Theoretical propositions about the influence of the embedment force, hardness and plasticity of the material of the part on the parameters of the relief groove were experimentally confirmed. These factors affect the optimization parameter both directly and through intermediate factors: the radius of rounding and the angle at the top of the indenter and the composition of the lubricating and cooling liquid and the speed of immersion. The interrelationship of phenomena during the formation of reliefs and the dependence of the depth of the groove on the process factors are constructed. Practical value. The method of restoring worn parts by indenting a linear indenter was developed, the principle of obtaining discrete surfaces of machine parts by alternating relief grooves with flat areas within a discreteness of 5-50% and methods of obtaining shaped surfaces in the holes of hollow parts by copying were developed.