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Small-radius wheels are gradually introduced on special rail vehicles, such as double-decker coaches and piggyback wagons. It allows for a low-floor design and further increases the loading capacity of vehicles. From the perspective of vehicle dynamics, small-radius wheels have lower unsprung mass than the nominal wheels with a radius of 460 mm, and it could mitigate the wheel-rail dynamic interaction. Also, the contact patch size is reduced due to the increased curvature of the rolling contact circle, and they are more sensitive to changes in the track geometry than nominal wheels, especially in turnouts with discontinuous rail profiles. To investigate the dynamic response of small-radius wheels in a turnout, the Manchester Benchmark passenger coach with variable radius wheels and a left-hand turnout with a radius of 245 m are introduced in this work. The influence of wheel radii on the running performance, including the wheel-rail interaction and wheel damage behaviour, is investigated by numerical simulations. In addition, a sensitivity study is executed to evaluate the influence of unsprung mass and wheel flange friction on the performance of a vehicle whose wheel radius is 275 mm, and the potential remedy to mitigate high wheel wear is proposed. [ABSTRACT FROM AUTHOR]

• The angular domain synchronous averaging (ADSA) method for wheel flat detection is proposed. • Simulation and experiment study on the effectiveness of the ADSA method. • This method can remove the interfering signals due to special track geometries or track defects. • This method can identify the position and the number of wheel flats. Wheel flats (WFs) can generate periodic impact forces and aggravate the wheel-rail interaction. Therefore, the early detection of WFs is significant for railway operators to lower the maintenance cost. In this work, the angular domain synchronous averaging (ADSA) method is employed to detect WFs on railway vehicles since it can handle the non-stationary vibration process of rotating machines by processing the vibration data in the angular domain. Furthermore, the short-time irregular impulses, such as those caused by crossings and rail joints, can be attenuated by using synchronous averaging technology. The periodic impact caused by WFs can be easily observed in the polar coordinate using the ADSA method, which is verified by one multibody system (MBS) simulation and one field experiment. Besides, the sensitivity of this method to various flat dimensions and multiple flats is also studied in the MBS simulation. [ABSTRACT FROM AUTHOR]

Wheel flat is a common local defect occurring to railway wheels. The relevant standards have specified the operational limits for wheel flats in terms of the length. However, in the actual operation, wheel flats, the sizes of which are smaller than the specified criteria, often appear on wheels, and such flats are difficult to be completely erased by normal wheel-rail wear, resulting in a long-term cyclic wheel-rail impact with a followed damping oscillation. Besides, the mechanism of wheel polygonization has not been explained perfectly. Considering these two aspects, this paper aims to investigate whether wheel flats can cause or aggravate wheel polygonization as well as the influence of vehicle speeds and flat lengths on polygonal wear. Firstly, a parametric and automatic wear calculation model, which combines FaStrip and USFD wear function, is proposed. The simulation results prove that wheel flats can cause or exacerbate wheel polygonization, and vehicle speeds and flat lengths have a large influence on the polygonal wear. Furthermore, the conclusion that wheel flat can cause or exacerbate wheel polygonization is verified by a field test. It further states that those excitations or defects, which can cause long-term periodic wheel-rail impacts, may cause or aggravate wheel polygonization. [ABSTRACT FROM AUTHOR]