1. School of Mechanical Engineering, Xi'an Jiaotong University 1 , Xi'an 710049, People's Republic of China
2. Institute of Design Science and Basic Components, Xi'an Jiaotong University 2 , Xi'an 710049, People's Republic of China
3. Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University 3 , Xi'an 710049, People's Republic of China