1Mazda Motor Corporation, 3-1, Shinchi, Fucho-cho, Aki-Gun, Hiroshima 735-0028, Japan
2Steel Research Laboratory, JFE Steel Corporation, 1, Kawasaki-cho, Chuo-ku, Chiba 260-0806, Japan
3Department of Mechanical Science and Engineering, Hiroshima University, 1-4-1, Kagamiyama, Higashi-Hiroshima city, Hiroshima 739-8527, Japan