Study On The Identification Method Of Wheel Rail Force And Track Irregularity

Wheel-rail force is the direct cause of vibration, impact, fatigue and damage of vehicle and track system, and it is also the basis for evaluating the safety of train operation; at the same time, when the train runs on the track, the track irregularity causes the dynamic change of the wheel-rail force, and arouses the vibration of the vehicle system, which can cause the fatigue damage of the vehicle parts. Therefore, identifying wheel-rail force and track irregularity situation accurately has great significance to ensure the safety of train operation. In this paper, the research work and its conclusions are mainly the following three points:(1) Vehicle track dynamic system is established based on the Fortran language. This system includes three models:1) Vehicle model. The lateral and vertical degrees of freedom of the car body, bogie and wheelset are considered, and the longitudinal degree of freedom is neglected, primary (box) and secondary (central) suspension system is simplified as the suspension force, at the same time, the equation of motion of vehicle system is established.2) Track model. Consider track model as three supporting structure including rail, sleeper, ballast and subgrade. Then establish the equation of motion of rail system, and apply the measured excitation to the rail surface.3) Wheel-rail contact model. Trace method is used to deal with the wheel-rail contact relation, in solving the parameters of wheel-rail contact, wheelset lateral and yaw and rail vibration is taken into account. The calculation results of the vehicle track system are compared with the experimental results, the comparison shows that this model is reliable and can provide the theoretical calculation data for the follow-up study.(2) Based on the established vehicle track dynamic model, the axle is treated as a Timoshenko beam with lumped mass and moment of inertia, and the bending vibration of the axle is considered. On this basis, this paper proposes to identify the wheel-rail force through the axle bending moment, that is, by calculating the bending moment of six specific sections of the axle, to solve primary suspension force, wheel-rail lateral force and wheel-rail vertical force. The results show that vertical force of wheel-rail and primary suspension can be identified by axle bending moment perfectly, but with the improvement of train speed, the identification of lateral force of wheel-rail has a larger error, at low speed, the error of lateral force within an acceptable range, this approach can be considered when the train speed lower than 250km/h.(3) This paper proposes integrating axle box acceleration twice to identify the track irregularity, that is, the simulation results of wheelset (axle box) acceleration are integrated by numerical method twice, then get the wheelset (axle box) displacement curve in time domain, then the accuracy of this method is verified by comparison with the track irregularity. The results show that track vertical irregularity can be identified by integrating axle box acceleration perfectly, but this method has limited effects for the identification of track lateral irregularity, the reason is that under the action of nonlinear creep between the wheel-rail, the rail lateral turbulence has a certain degree of attenuation, especially for the attenuation of high frequency turbulence.The results of this paper can provide reference for the wheel-rail force testing and track irregularity inspection.