Dr. Quan Wang, Tribology Research Institute Southwest Jiaotong University Chengdu 610031, P. R. China, CHINA
Dr. Zhiwei Wang, Tribology Research Institute Southwest Jiaotong University Chengdu 610031, P. R. China, CHINA
Prof. Jiliang Mo, Tribology Research Institute Southwest Jiaotong University Chengdu 610031, P. R. China, CHINA
Research and /or Engineering Questions/Objective: The disc friction brake which consumes the kinetic energy of the high-speed train through disc-pad friction is one of the important approaches to brake or decelerate the train as well as the safety and performance assurance. However, the friction between the brake pad and the disc may lead to the vibration of the brake components in the braking process. And when the friction-induced vibration of the disc brake system is transmitted through the suspension system to the bogie, it not only reduces the stability of the train operation and the ride comfort for the passengers, but also causes damage to the brake device and reduces the service life of such system. what’s worse, the vibration may provoke noise problems. Therefore, the mechanism of friction-induced vibration of the disc brake system and the method to eliminate the unstable vibration require in-depth research.
Methodology: The experimental research, finite element method and numerical simulation are widely used in the analysis of the disc brake system and a great deal of meaningful research achievements have been obtained. In this article, to reflect the vibration response of the disc brake system more realistic in the braking process, a three-degree-of-freedom dynamic model of the disc brake system for the China Railways High-Speed train CRH5 is established by considering the effect of the wheel/rail adhesive characteristics and the number of brake units (the powered wheelsets installs two brake units and the non-powered wheelsets installs three on CRH5). Then, the model is applied to analysis the nonlinear dynamic response under different brake conditions to investigate the stability of the disc brake system using the numerical integration method. And diagrams of bifurcation, phase plane, Poincaré map and time domain response are used to discuss the vibration characteristics of the disc brake system in details.
Innovation: The nonlinear friction between the brake disc and pad, and the nonlinear interactions between the wheel and rail are considered in this three-degree-of-freedom model. And it can be applied to investigate the effect of wheel/rail adhesive characteristics, parameters and the number of brake units on the disc brake system.
Results: Results show that with the increasing of the brake force, the brake pad occurs periodic motion and chaotic motion alternately, and the region of chaotic vibrations is growing while the region of periodic vibrations is decreasing. In addition, the stick-slip vibration of the brake pad and the torsional vibration between the brake disc and the wheelset are more complicated and violent with a larger brake force. It also shows that the chaos phenomenon of the disc brake system only occurs when the vehicle speed is less than the critical speed, and after that the system maintains stable periodic vibrations. Moreover, the results obtained with different number of brake units reveal that the chaotic region of the disc brake system with three brake units is narrower than the system with two brake units. It indicates that the high-speed train adopted three brake units to undertake the decelerating or braking task is more stable.
Conclusion: The research result can provide useful references for the design of the brake conditions and the vibration control of the disc brake system. The dynamic model proposed can also be applied to discuss the effect of parameters on the stability of the system further.