1. Tianjin Key Laboratory of Modern Engineering MechanicsSchool of Mechanical EngineeringTianjin University Tianjin 300072 P. R. China
2. Applied Mechanics LaboratoryDepartment of Engineering MechanicsTsinghua University Beijing 100084 P. R. China
3. Department of Aerospace Engineering and Engineering MechanicsUniversity of Texas at Austin Austin TX 78712 USA
4. Center for Analysis and TestTianjin University Tianjin 300072 P. R. China