Application of Fractal Formalism for Express Analysis of Mechanical Properties of Parts

Problem The choice of processing methods plays a decisive role in the formation of the set of properties of the original part, especially the methods of surface processing. Problem. Detonation coatings, as a type of gas-thermal coatings, due to the highest characteristics, are increasingly used in various industries. Due to the highest characteristics (bonding strength with the substrate up to 250-280 MPa), detonation spraying can be better for strengthening and restoring the most responsible and loaded parts and assemblies. Goal. Detonation spraying increases the mechanical properties of various parts of a responsible purpose, whose surface wears out during operation. It is proposed to apply the theory of fractals to estimate the mechanical properties of hydraulic hammer parts. Methodology Evaluation of the mechanical properties of parts after detonation spraying using non-destructive control methods based on structure analysis is complicated due to the complex configuration of the shape of its components. A heterogeneous and geometrically complex structure is characteristic of many surfaces after various types of spraying/dosing device (block), fuel oil or air is blown in specified portions – finely dispersed powder into the gas mixture immediately before its ignition, then the gas mixture is ignited. Results. As a result of ignition and movement along the channel of the combustible mixture, it explodes with the release of a significant amount of heat and the formation of a detonation wave, which accelerates and transfers through the barrel to the surface of the part the particles that are sprayed, with a speed determined by the geometry of the barrel and the composition of the gas. Originality. The fractal dimension D of the structure of the hammer and the peaks of the hydrohammer after detonation spraying at a magnification of 100 was calculated according to the Hausdorff formula where is the number of cells with linear size, that cover the object under. A method of comparative evaluation of the effectiveness of strengthening technologies for increasing the durability of hydraulic hammer parts has been created and tested, which is based on testing parts after various strengthening options and provides action during the loading process of pressures and gas-dynamic characteristics that simulate the relevant parameters of operational loads. Practical value. Tests of parts strengthened by the researched methods showed that, compared to the initial version, a significant increase in wear resistance is achieved: Mathematical models are obtained, which makes it possible to carry out an operational forecast of the mechanical properties of hydraulic hammer parts strengthened by detonation spraying based on the analysis of their fractal structure within an error of up to 6%.