An investigation into the mechanism of high-order polygonal wear of metro train wheels and its mitigation measures

High-order polygonal wear wheels have been detected on metro express train operating on one metro line in China, which cause fatigue failures of steel coil springs in the primary suspension. A series of tests and theory analysis were conducted to figure out the mechanism of wheel high-order polygonal wear. The wheel out-of-roundness (OOR) measurement results show that the wheels exhibit polygonal wear with 12–14 harmonics, which are very different from other metro train wheels reported in the literature. The investigation results indicate that the first bending vibration of the wheelset is the root cause of wheel high-order polygonal wear. Rail corrugation with a wavelength of 200 mm in the 1/3-octave band on sharply curved tracks is the main excitation source of the first bending vibration of the wheelset. The formation process and key influencing factors of wheel high-order polygonal wear are analysed in detail. Three measures are suggested to mitigate the formation of wheel high-order polygonal wear.