PSI - Issue 81

Dmytro Voloshyn et al. / Procedia Structural Integrity 81 (2026) 264–268

265

lubricant condition, assembly tightness, installation and removal features, quality of incoming inspection of spare parts during maintenance and repair, etc.

Nomenclature а

scale parameter (15,86) parameter form (1,86) operating until failure

b

t

To study the actual reliability of bearing assemblies, the use of the ‘failure tree’ method was proposed. Its tools allow for a detailed analysis of factors that can contribute to the occurrence of damage and failures of individual components, which in further operation will lead to the failure of the assembly with a certain probability. The ‘failure tree’ is the basis for th e development of logical-probabilistic models of cause-and-effect relationships between failures of complex systems with failures of their elements and other events (influences). The analysis of the occurrence of a failure consists of sequences and combinations of disturbances and damage. Thus, it represents a multi-level graphological structure of causal relationships obtained by tracing dangerous situations in reverse order in order to find possible causes of their occurrence. The main advantage of the ‘fa ilure tree’ method over other methods of analysing complex systems is the ability to develop a diagram of the entire picture of the cause-and-effect mechanism of failures in the axlebox assembly. At the same time, all processes and causal relationships occurring in the axlebox are strictly correlated with only two states: operability and failure. When constructing a ‘tree’, it is necessary to start from a specific undesirable event (top event) and analyse the possible causes of its occurrence. The construction of the ‘tree’ ends with the identification of primary events that are not detailed or broken down into components and can be described statistically based on information about similar elements or identified experimentally. An important aspect of this method is the consideration of personnel errors and dependent failures in relation to the wagon unit under consideration. The ‘failure tree’ is graphically represented in the form of a branched open graph (in wh ich there are no circular connections), resembling an ‘upside - down tree’. The use of this method provides an effective tool for assessing the reliability of wagon axleboxes. Based on modelling scenarios of the unit's behaviour in operation, it is possible to recommend new design options, taking into account the specified reliability parameters. 2. Analysis of the reliability of freight wagon axleboxes in operation The main element of the axlebox assembly is the bearing block. The bearing elements absorb static and dynamic loads transmitted to the railway track from the wagon body in empty and loaded conditions under various operating modes. The occurrence of alternating loads when passing railway track joints and entering curved sections of the track creates the conditions for a large number of operational failures and damage to the axlebox assembly. An important factor contributing to failures is the incorrect actions of maintenance personnel during the maintenance and repair of wagons. When assembled, the bearing may have a mismatch between the radial and axial clearances. Such discrepancies in further operation can cause further malfunctions and lead to a probable failure of the axlebox assembly. The main malfunctions of the outer and inner rings of bearings include:

• cracks, fractures, and chipping of the ring material (Fig. 1а) • craters and flaking of the raceways caused by fatigue damage • corrosion spots on the raceways of the rings (Fig. 1b) • burr formation on the chamfers of the outer and inner ring edges The main roller failure modes include: • cracks and chipping of the roller material • dents on the rolling surface

• ring-shaped marks on the rolling surface without metal removal • corrosion pits on the rolling surface in the form of point defects • craters on the rolling surface of cylindrical rollers • damage to the ends of cylindrical rollers in the form of herringbone-type scratches Main separator malfunctions: • cracking or fracture of the retaining bridges in polyamide cages of cylindrical roller bearings, resulting in roller release • cracks in the bearing cage