Effects of torque adjustment rates and increments on wheel-rail adhesion instability behavior under various speed and axle load conditions

Abstract

During the locomotive traction process, if the tangential force exceeds the maximum adhesion force of the wheel-rail interface, wheel-rail adhesion instability occurs, leading to accelerated damage to the contact surface due to severe wear. Therefore, it is important to study the dynamic behavior of wheel-rail adhesion instability to improve the safety and stability of the train operations. A novel wheel-rail rolling contact experiment machine based on torque control was designed and established to investigate the wheel-rail adhesion instability behavior. The results show that: As the torque of the loading motor increased, the slip ratio initially increased steadily, then rapidly rose and fluctuated. With the decrease in torque adjustment rate, the fluctuation of the slip ratio decreased. Meanwhile, the torque increments had an impact on adhesion instability behavior. When the torque increment was less than 0.6 Nm, with the increase in torque increment, the slip ratio initially increased and then decreased, while the wheel-rail adhesion coefficient increased. However, when the torque increment exceeded 0.6 Nm, as the torque increment increased, the maximum slip ratio remained constant, while the adhesion coefficient decreased, leading to the slippage of the wheel-rail roller. In addition, with the axle loads and rotational speeds increased, the maximum slip ratio and adhesion coefficient decreased. Also, the function relationship between the slip ratio and the torque increment after the critical point (adhesion force saturation point) was proposed, which can provide guidance for vehicles to adjust the adhesion coefficient.