1. Materials & Fracture Laboratory, Department of Mechanical Design, Chonbuk National University, Duckjin 1-664-14, Chonju, JB561-756, South Korea
2. Automobile Hi-Technology Research Institute, Faculty of Mechanical and Aerospace System Engineering, Chonbuk National University, Duckjin 1-664-14, Chonju, JB561-756, South Korea