Coupling effect of track irregularity and wheel-rail contact conicity on carbody swaying of a metro vehicle: an experimental investigation

A carbody swaying with low frequency of about 2 Hz occurs during vehicles with linear induction motors (LIM) running in shallow curve and straight sections on a China metro line, which significantly deteriorates the ride comfort of passengers. A series of field tests were carried out to identify the main cause and possible solutions. During the tests, the vibration characteristics, dynamic performance, wheel-rail contact condition and track condition were analysed. The test results show that the abnormal carbody swaying is a manifestation of a frequency coupled resonance between the track excitation frequency, bogie hunting frequency and carbody modal frequency at the operating speed. The periodic excitation of the track is the periodic track alignment irregularity with a wavelength of 11-13 m, which is caused by rail surface wear during long-term operation. The carbody swaying can be suppressed by reprofiling the wheel tread to LMA and optimising the suspension parameters.