Abstract.As it is known rail is one of the most significant elements of the whole railway construction. Operation under alternating loads from wheels of the rolling stock and different ambient temperatures lead to appearance and development of rail defects and damages. A great variety of operational factors (freight traffic density, axial loads, traffic speeds, track layout and profile) as well as special features of manufacturing and thermal treatment of rails create certain difficulties while identifying reasons for defects and damages. The article deals with an attempt to estimate influence of track layout and lateral forces on appearance of defects and damages in rails on the base of long-term observations of rail operation in Kharkiv Metro. On the basis of the vehicle/track mathematical model which considers structural features of both rolling stock and permanent way in underground systems, the level of lateral forces in curves was calculated. The coefficients of correlation between the track curvature, the level of forces and the amount of defected rails removed were later obtained, that made it possible to determine the dominant factor which may lead to appearance and development of contact fatigue defects in rails laid in curves.
The article deals with determination of dynamic forces in interaction between a rail vehicle and underground track for working out recommendations in terms of a longer service life of the permanent track without extra charges. The issue is of importance for enterprises under limited resources. The research was conducted with mathematical model methods for the vehicle/track dynamic system (the principles were developed earlier), as the experimental work in the underground tunnels was complicated by intensive train traffic during a day. A special feature of the research was consideration of a rail as a bar rested on discrete elastic-dissipative supports in a design diagram of the vehicle/track dynamic system. Thus, the authors established the effects of unequal elasticity of the track rail support on the value of vertical dynamic forces when a metro coach moves on the track. In particular, the dependencies of dynamic factors and amplitude ratios of vertical forces on speeds of metro coaches along the discrete elastic- dissipative track were obtained. An exceptional value of the research is consideration of both vertical and horizontal lateral forces on the vehicle/track interaction. It allowed the authors to define the value of vertical and horizontal lateral forces which occurred when metro coaches moved along straight and curved sections of the track according to the speed and curve radius.
Areas of rational use of the track construction with reinforced concrete sleepers have been defined, however, it requires improving and the problem of intermediate rail fastenings is particularly serious here. The most common intermediate rail fasteners used in Ukrzaliznytsya are lining terminal-bolted fasteners of KB type and direct fixation boltless fastening type KPP-5. Calculations have been made for the restoration of operability of KPP-5 fasteners using PRP-3.2 repair pads with a thickness of 9 mm and PRP-3.2.1 with a thickness of 10 mm. It has been established that in the sections with the traffic load of more than 15 million ton km/km in year, restoration works should be performed after 13 years of operation. Using 10 mm thick PRP-3.2.1 rail pads will provide the necessary pressing force of the rail base against the sleeper until the expiration of the standard service life – no more than 30 years. When the traffic load is less than or equal to 15 million ton km/km in year, recovery can be performed after 22 years of operation. The use of both types of pads will ensure the reliable functioning of KPP-5 fasteners until the expiration of its service life.
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