Abstract: Influence of wheel diameter difference on the stress and movement of wheelset is discussed based on the analysis on wheel diameter difference types. A train dynamic model which consists of an eight axle heavy haul locomotive+a detailed C80 gondola car +a simplified C80 gondola car has built up, the effect of different type of wheel diameter difference on the wheel/rail interaction under coasting and breaking condition is simulated. The results show that the movement of wheelset will changed for the reason of wheel diameter difference, thus affect the wheel/rail interaction and aggravate the wear between wheel and rail; Because the yaw angle of wheelset caused lateral creep, so the influence of wheel diameter difference in anti-phase on the wheel/rail lateral force and wear is larger than wheel diameter difference in same-phase. Breaking condition decrease lateral creepage force compare with coasting condition, so the influence of wheel diameter difference on wheel rail lateral force under electric braking condition should be less than coasting condition, and decrease lateral wheelset force as well. Due to the braking force can reduce the adjustment ability of wheelset on its rolling diameter between left and right wheel, the steady wheel diameter difference under electric braking condition should be larger than the steady wheel diameter difference under coasting condition, the wear between wheel and rail would overweigh the coasting condition too, wheel diameter difference also leads to eccentrically-wearing under breaking condition, further increase wheel diameter difference.

Key words: dynamics, electric breaking, locomotive, wheel diameter difference, wheel/rail interaction