According to the principle of hierarchy, the interconnection and subordination of the structural elements of the technical system (in this case, the rolling stock) determines the quality criteria both for each part and for their materials. So, for example, when planning the quality of rolling stock elements, such as parts of an automatic coupler, draft gear, etc., it is necessary to take into account the requirements for the material of the surface layer, which determines the reliability of the element. In this case, an indicator of the reliability of the elements is the wear resistance of the material, which, from the point of view of the consumer, is conveniently defined as the wear rate. In this case, it is necessary to take into account that the wear of the surface layer is of a probabilistic nature, and the wear rate has deviations from the calculated value. This fact is associated with the influence of various, constantly changing factors. On the other hand, in the manufacture of technical systems, the occurrence of disturbing factors is associated with a significant number of technological processes of various kinds, the implementation of which affects the service characteristics of each product, and, as a result, consumer properties that characterize its quality. In order to ensure the required level of service characteristics of the surface layer of the friction draft gear elements, the paper proposes to plan the wear rate using stray fields, taking into account the factors that determine its change during the entire technological sequence of working surface formation. At the same time, the principles proposed in the article are only the first stage in the process of assigning quality criteria for materials of the surface layer. No less difficult, the second stage is the establishment of cause-and-effect relationships of the influence of various factors on the dissipation of the wear rate.
