Wheel flat can cause or exacerbate wheel polygonization

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.