Hunting motion stability of wheelset based on energy method

In order to analyze the formation mechanism and energy transfer mechanism of wheelset hunting motion, the energy expression in the process of hunting motion was established based on the theory of vehicle system dynamics.According to the phase relationship of wheelset movement parameters and energy expression, the work of each part and energy transfer route during the hunting motion were determined.Input energy values under different parameters were calculated through numerical simulation, thus the influences of tread equivalent conicity, mass of wheelset, primary suspension stiffness and gravity stiffness on the stability of wheelset were compared.Research result shows that the synergy of creep force and cone tread is the fundamental cause of hunting motion.The stiffness force contained in creep force inputs energy into the wheelset lateral movement through the regulating action of wheel/rail longitudinal and lateral creep rate, and the damping term in creep force consumes the energy of wheelset system.When the inputenergy is larger than the dissipated energy in a cycle, the hunting motion diverges.When the input energy is less than the dissipated energy in a cycle, the hunting motion converges.When the input energy is equal to the dissipated energy in a cycle, the wheelset performs periodic motion with a constant amplitude.The enlargement of inertia term and conicity is harmful to the stability of wheelset, while the enlargement of primary stiffness is in favor of the stability of wheelset.Tread equivalent conicity has the biggest influence on the stability of hunting motion of wheelset.When conicity increases from 0.15 to 0.20, the input energy increases nearly by 9.5 times.Primary suspension stiffness comes the second.When the stiffness increases from 75 kN·m^-1 to 100 kN·m^-1, the input energy decreases nearly by 60%.The mass of wheelset is the smallest one.When the mass of wheelset increases from 1 000 kg to 2 100 kg, the input energy increases nearly by 1.1 times.Under the condition of conical tread, the effect of gravity stiffness has little influence on the stability, which can be ignored.