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AbstractFarm tractors due to the nature of their work are exposed to a substantial risk of failures. The issues of their reliability are unusually significant in the aspect of the time limit of realisation of agricultural works in agrotechnical seasons. Nowadays, tractors provided for agriculture have increasingly complex functional units. The aim of the paper was to analyse reliability of presently produced farm tractors. Three tractor makes were evaluated and the analysis of failures was carried out with regard to functional units. Based on the obtained results, the average time of correct functioning and refreshment times and availability of particular tractor makes were determined. It was stated that the obtained empirical data of the correct functioning time and refreshment time may be well described with exponential functions. Significant differences in the values that determine the average time of correct functioning and duration time of refreshment obtained by tractors of the investigated makes were found. From among particular functional units, electric and hydraulic systems were the most often damaged, regardless the tractor make.

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This paper is concerned with the possibility of applying modern non-contact methods for assessing the wear as a result of tribological interaction between working bodies and the soil. An original method for wear testing using the test space discretization based on the 3D scanning technology was employed. A localized volumetric wear coefficient was proposed, allowing for wear analysis and improving the accuracy of the Holm-Archard model. The coefficient of local volumetric wear shows the influence of the nominal shape and the slip trajectory of the abrasive particle along the elementary surface on the intensity of wear. At local volumetric wear coefficient > 0.3, this factor determines the intensity of surface wear. Volumetric wear characteristics are the basis for prediction of wear consequences for different materials and techniques of reinforcement of working surfaces, subject to intensive wear in abrasive soil mass. The reliability of the study is confirmed by the comparison with the mass method for wear assessment and the results of the application of the proposed method for different conditions of abrasive wear of operating parts.