COMPARATIVE EVALUATION OF THE CREEP OF PISTON ALUMINUM ALLOYS

The paper deals with the issues of reliability of piston materials in the process of increasing engine power. It is precisely the increase in the liter power of engines while ensuring environmental and economic requirements that is today one of the main areas of work in engine manufacturing. Studies have shown that material creep has significantly affects on the reliability of internal combustion engine parts. The most thermally loaded engine element is a piston. The main critical areas for it can be identified: the edge of the combustion chamber, the area of the piston rings and the piston skirt. The appearance of seizures on the piston skirt is sometimes observed even during the engine initial tests at the engine power increasing. Thus, we can speak about the relevance of the problem of identifying the reasons for reaching the critical state of the piston material. Based on these data, it becomes possible to develop measures to ensure the reliable operation of the piston. Among the most common materials for the manufacture of pistons are aluminum alloys AL25 and AK4. The chemical composition of these alloys varies considerably. The study obtained coefficients for calculating the creep rate for these materials. The identification of the calculation of the creep deformation of aluminum alloys at different stress levels, for different temperatures is carried out. The upper boundary of the region of model adequacy in terms of temperatures and stresses is determined. The creep rate of aluminum alloys is analyzed at different temperatures. In the conclusions, a comparison of the piston materials is made and the advantages of the AK4 alloy in comparison with the AL25 alloy, which are coming out when the engine power is increased, are indicated. The direction of further research is also indicated, which is associated with the analysis of the deformation of the considered materials at the first stage of creep.