Effect of wheel flat on dynamic wheel-rail impact in railway turnouts

Wheel flat is a form of wheel tread defect that reduces the service life and running safety of trains and tracks. Based on the multi-body system dynamics theory, a rigid-flexible vehicle-turnout dynamic coupling modelwas established, and the wheel diameter-varying flat simulation method used to create wheel flat models of different sizes. The most unfavourable phase of flats on the wheels of a vehicle crossing a turnout was studied by scanning and calculating the phase of the flats. The influence of flat size and vehicle speed on a vehicle with flats crossing a turnout was also analyzed. The results show that, compared with a normal wheel crossing a turnout and a wheel flat acting on the interval rail, a wheel flat acting on the wheel load transition of the frog area will excite greater vertical wheel-rail forces and vertical axle box vibration acceleration; in the turnout area, the main frequency band of the vertical vibration acceleration of the axle box is 550–800 Hz, which is rarely affected by the size of flats or the speed of the vehicle. The third-order bending mode of the wheel is excited when the wheel transits from the wing rail to the point rail.