In many countries, including Russia, the three-piece bogies are essential for freight transportation. Their dynamic behavior includes many nonlinear effects and is strongly dependent on the realized parameters that are subject to change due to wear. Since the beginning of the 20th century, when the three-piece bogie was invented, there has been significant progress in its design. Actually, now the term three-piece bogie is applied to a variety of construction schemes that look similar, but have principal differences. This article investigates various construction schemes of the three-piece bogies from the point of view of stability, ride, and curving quality, using numerical simulation results as well as the results of natural experiments for the available bogies. Analysis of the dynamic behavior of traditional three-piece bogieThe traditional three-piece bogie (for example, model 18-100 in Russia, figure 1) is equipped with central suspension that consists of a set of springs and wedge friction dampers working in vertical and lateral directions and keeping the frame square. The side frames with their flat surfaces rest on the axle boxes (or bearing adapters). The size of the opening in the side frame provides clearances in longitudinal and lateral direction within which the axle box moves resisted by dry friction forces.In traditional three-piece bogies, the flanges of wheels are worn much faster than the tread. For instance, for gondola cars that are always operated in laden condition, the tread wear rate reaches 3.6 mm per 100 km, but the corresponding flange wear rate is up to 11.1 mm per 100 km, which actually means that the wheel has to be reprofiled (after 9 mm flange wear). This problem is especially sharp for wagons operated in Siberian regions, where 80% of track are curves less than 600 m radius.The main reason for flange wear is the unstable behavior of bogies in curves (rutting mode), reference [1], when the bogie is flanging with a two-point contact situation (figure 2) instead of passing the curves using the wheel conicity. Flanging is the result of bogie 'warping', which makes the angle of attack increase when compared to radial position.

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Purpose: To analyze and compare the requirements of State Standards of Russia, countries of Europe and North America to assessment of dynamic qualities of freight cars, their impact on railway track. Methods: Review and analysis of requirements of various countries to conditions to pursue testing of freight cars on dynamic qualities and their impact on a track, requirements to indicator permissible values made it possible to form the most representative calculated cases for simulation of railway crew motion along various construction tracks (straight, curve sections) and to pursue the study of freight car dynamics with the help of computer simulation modelling in program complex "Universal Mechanism". Results: The comparison of various country’s requirements to the assessment of freight car dynamic behavior is made. Using computer simulation methods, oscillograms of various indicators (forces, accelerations, coefficients) for universal gondola car, installed on bogies of 18-100 model, at its motion along various construction tracks were obtained. The advantages and flaws of used approaches to assess dynamic qualities, indicators of crew impact on various country’s track are shown. Practical significance: The work obtained results can be used to improve the system of railway crew dynamic behavior assessment and its impact on a track with the purpose to improve the safety of freight car motion in Russia.