Analysis of Longitudinal Vibration of Wheel Set during Locomotive Slippage

Roll-slip oscillation in locomotive is an unstable vehicle motion and it turns into strong self-excited torsional vibration of drives and is usually associated with a negative slop of adhesion curve. The periodic variation of adhesion coefficient between wheel and rail arises and it provokes longitudinal vibration of wheel set. A simplified mathematical model of single wheel-set drive system of locomotive whose rotary and longitudinal freedoms are taken into account is established. The phase trajectory of longitudinal vibration of wheel-set is drawn by numerical simulation and frequencies of vibrations are calculated on the condition that the mean creep ratio exceeds critical creep ratio. The formed mechanics of longitudinal vibration makes clear with help of graphical analysis. Results demonstrate that the longitudinal vibration is self-excited vibration during locomotive slippage. The longitudinal vibration frequency is integral multiple of nature frequency of torsion vibration and the amplitude of longitudinal vibration is the biggest when it is two times. Therefore, parameters such as longitudinal locating stiffness of wheel set should be set rationally to avoid strong longitudinal vibration of wheel set during slippage.