13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Estimation of Wheel/Rail Contact Forces Based on an Inverse Technique Tao Zhu*, Shoune Xiao, Guangwu Yang, Mingmeng Wang State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China * Corresponding author: 232665368@qq.com; hamilyzt@yahoo.cn Abstract For actual operating conditions, wheel/rail contact forces of high-speed train are very difficult to directly measure. Minimizing the role of driving force between wheel and rail is a key point to ensure railway wheel-rail transport systems in good condition and efficient operation in the long-term. A time-domain inversion method for dynamic loads was proposed. Based on the state space equation, dynamic programming methods and the Bellman principle of optimality, the main theoretical derivation of the inversion mathematical model was given. With a high-speed vehicle system as the research object, accelerations of axle box as input conditions, the vertical and horizontal wheel/rail forces were identified. Inverse results were compared with SIMPACK simulation results which had the same kinetic parameters. The results indicate that the vertical and horizontal wheel/rail forces had the same trend with SIMPACK simulation results. Results from the inverse model were also compared with experiment data. The inverse model has high inverse accuracy, and can be used for real-time monitoring of the running train wheel/rail contact forces. Keywords inverse technique, wheel/rail contact force, SIMPACK simulation, experiment data 1. Introduction The estimation of dynamic forces acting on a structure is a problem that has been treated with only partial success. Methods for such estimation include in two categories, direct methods and indirect methods. Direct methods use the placement of force transducers into the load paths at the point of force application. Indirect methods use other sensor types placed at locations on the structure that may not necessarily correspond to the force input locations. Many situations require indirect methods because the forces cannot be measured[1]. For example, the train is subject to a wheel/rail impact load when operating because of rail irregularities and crossing turnouts. Currently, various methods for inverse identification problem associated with indirect force measurements have been proposed, see for example Ref. [2-4] for an overview. Among them, are two main methods: the frequency domain[5,6]and the time domain method [7,8]. The running stability of a vehicle depends on the wheel/rail interaction. Wheel/rail contact forces play an important role to keep the vehicle stable on straight track and make it able to negotiate through curves smoothly. The possibility of gaining information about wheel–rail contact forces in real time and on-board normal rolling stock vehicles has significant value. But due to the complexity of the inverse identification problem in railway vehicle systems, not much research has been performed in this area. Some papers on this subject focused on impact detection at the contact point[9,10]. Commercially available systems for monitoring wheel-rail health are based on strain measurements at a chosen location on the track, and the track strain will be measured when the train passed [11]. A big disadvantage of the application of such a system is the necessity to locate strain measurement points at many locations on the track, not only time consuming but also expensive[12]. There is a great need to formulate a method that can be based on measurements on the vehicle but not on the track. This paper presents a new method to identify the time history of input excitation based on the dynamic programming equation. The forces were identified in the time domain by a recursive
RkJQdWJsaXNoZXIy MjM0NDE=