1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, P. R. China
2. Department of Engineering Mechanics, College of Mechanical & Vehicle Engineering, Hunan University, Changsha 410082, P. R. China
3. Key Laboratory of Manufacture and Test Techniques for Automobile Parts, Ministry of Education, Chongqing University of Technology, Chongqing 400054, P. R. China