1. School of Mechanical Engineering, Southwest Jiaotong University, Sichuan, Chengdu 610031, P. R. China
2. Tribology Research Institute, School of Mechanical Engineering, Southwest Jiaotong University, Sichuan, Chengdu 610031, P. R. China
3. Technology and Equipment of Rail Transit Operation and Maintenance Key Laboratory of Sichuan Province, Sichuan, Chengdu 610031, P. R. China