1. School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
2. Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province, Chengdu, Sichuan 610031, China;
3. School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
4. School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, China e-mail: