Methodology and Example of Calculating the Rational Resource of Axial-Piston Hydraulic Machines of Mobile Equipment

The article analyzes approaches for creating models for optimizing the durability of mobile machine units. On the basis of the selected model, in which the target function is the total specific costs of purchasing the machine and the costs of maintaining its working condition, a method of calculating the rational resource of axial-plunger hydraulic machines has been developed for the condition when the resource of the hydraulic machine is limited by the resource of only its plunger pairs. The methodology, built on the basis of the chosen model for optimizing the durability of simple technical systems, takes into account the patterns of wear of plunger pairs under certain operating conditions, and also takes into account the proposed dependencies for calculating their total wear limit. The methodology consists of five consecutive operations, namely: determining the total marginal wear; obtaining experimental patterns of wear of plunger pairs over time in the form of regression equations; calculation of the number and periodicity of technical maintenance of the hydraulic machine for the inter-repair cycle; calculation of the rational resource of the hydraulic machine.The results of the comparative calculation of the rational resource of the adjustable axial-plunger pump 321.224 of the hydraulic system of the single-bucket excavator EO-3323 according to the developed method are also given.The total marginal wear of the pump was determined according to the criterion of reducing its efficiency, namely from the condition of a drop due to the wear of its volume coefficient of useful action by 30 %.To obtain the patterns of wear of the pump's plunger pairs, the results of previous operational tests of the pump were used for two variants of its lubrication: lubrication with ordinary hydraulic oil and lubrication with oil whose anti-wear properties are activated by an external electric field. Specific costs for the purchase of the pump, which are included in the durability optimization model in the form of depreciation deductions, were calculated for the inter-repair cycle. The specific costs of maintaining the working condition of the pump were equal to the costs of its maintenance, during which hydraulic oil and filters are replaced, that is, the pattern of wear of plunger pairs is returned to the starting point.