Prediction of service life of auto-tractor engine parts

Abstract

Wear and fatigue are phenomena that limit to some extent the reliability of mechanical systems in almost any modern machine. Traditionally, reliability indicators of power parts of machines are evaluated differentially, according to individual criteria. This is often justified, since in the design of machines there are a lot of parts that “work” only on fatigue under repeated-variable loads. There are also parts that “work” exclusively in conditions of friction, sliding or rolling. However, in reality there are also mechanical systems in which a combination of both phenomena takes place. For example, these are such systems as: “crankshaft-connecting rods of piston engines”; “gearing, camshaft-cam follower”; “axis bearings of centrifugal machines”; “details of the chassis of the car and tractor”; “wheels of rolling stock-rails of the railway track” and a large number of other critical structural elements of various machine components. Consequently, the entire range of scientific research in the design, manufacture and repair of machines should be aimed at ensuring fundamental transformations in technology and creating the prerequisites for the scientific justification of both methods for calculating the accuracy of mechanisms and all technological problems, from the design of the technological process as a whole to a thorough mathematical modeling of its individual components. The currently used methods for calculating the strength by safety factors in a deterministic formulation do not sufficiently take into account the scattering of the characteristics of fatigue resistance, the random nature of the loading of parts and do not provide an estimate at the design stage of the distribution function of the resource of machine elements. At the same time, it is possible to correctly determine the indicators of machine reliability and durability on the basis of these functions.