Influence of the aging factor on the reliability of agricultural machinery

Abstract

In the course of time a number of machine significant changes related to machine aging occur. The reasons for these changes are quite diverse. They are inevitable and irreversible in the time process of a gradual transition of the machine to a lower qualitative state. The article contains the data about the change in the indicators of no-failure and repairability of tractors (average restoration time) in the before-repair and between-repairs periods, which should be considered as a result of their aging. Data on the ratio of the lifetime of units and parts indicate the decisive role of the aging factor, but the lifetime can be strongly influenced by the assembly technology and the main thing - the run-in of parts. The degree of the aging of a machine can be estimated by reducing the lifetime of components, MTBF, machine productivity, etc., in the form of an aging factor, Kc. It shows how many times the lifetime of the part replaced in the machine is less than the nominal lifetime of the original part. The MTBF of the ageing machine is less than that of the new machine, or the labor input for the restoration of the old machine is greater than that of the new machine. By determining the aging rate of the parts to be replaced over the time interval under consideration, we constructed an aging function. The aging process of agricultural machinery was evaluated by the time and moment of resistance to unscrewing the uncoated threaded joints with a service life of 0.2 to 4 years. According to the obtained distribution functions, the average time increases with increasing service life, and the moment of resistance to unscrewing approaches the maximum values. With a service life of more than 4 years, the number of non-disassembled bolt connections, which break at the moment of unscrewing, increases, and the maintenance time also increases. The dynamics of the aging factors of threaded connections can be represented in the form of quadratic functions.