Modeling of Materials Deformation - First Principle Study of Ductility of Solids -

Date & Time
6 March 2008 (Thur), 1:30 pm - 3:00 pm
6F seminar room, Sengen site
Prof. Shigenobu Ogata(尾方成信教授)
Department of Mechanical Science and Bioengineering, Osaka University(大阪大学大学院基礎工学研究科機能創成専攻)
Modeling of Materials Deformation - First Principle Study of Ductility of Solids -
We newly propose ductility parameter D, which is defined as the ratio of energies needed for bond breaking under uniform shear and tensile deformations. So far the ratio of bulk modulus and shear modulus [1] and ideal tensile and shear strength [2] and so on are carried out to estimate ductility of solids. However they cannot clearly demonstrate the actual big ductility gap between ceramics and metals. We estimated our proposed D of 23 materials including different ceramics, alloys and metals by performing shear and tensile testing simulations to these materials using ab-initio density functional theory method [3]. We find that (1) ductility of crystalline solids is mainly controlled by the ideal shear strain [4], (2) the D can clearly demonstrate the big ductility gap between ceramics and metals, and (3) the D has clear linear correlation with widely used experimental toughness value in wide range of different materials from ceramics to metals. Hence we conclude D is a good predictor of ductility and also fracture toughness.
[1] A. Kelly, W. R. Tyson and A. H. Cottrell, Philos. Mag., Vol. 15 (1967), p. 567.
[2] S. S. Hecker, D. L. Rohr and D. F. Stein, Met. Trans., Vol. A 9 (1978), p. 481.
[3] G. Kresse and J. Furthmuller, Phys. Rev. B, Vol. 54 (1996), p. 11169.
[4] S. Ogata, J. Li, N. Hirosaki, Y. Shibutani and S. Yip, Phys. Rev. B, Vol. 70 (2004), 104104.
Dr. Taichi Abe(阿部太一)