Crack growth versus blunting in nanocrystalline metals with extremely small grain size.pdf

ARTICLE IN PRESSContents lists available at ScienceDirect Journal of the Mechanics and Physics of Solids Journal of the Mechanics and Physics of Solids 57 (2009) 305–3240022-50 doi:10.1  Cor E-mjournal homepage: /locate/jmpsCrack growth versus blunting in nanocrystalline metals with extremely small grain sizeFan Yang a, Wei Yang a,b, a Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China b Zhejiang University, Hangzhou 310058, Chinaa r t i c l e i n f o Article history: Received 16 July 2008 Received in revised form 6 October 2008 Accepted 21 October 2008 Keywords: Polycrystalline material Fracture Grain boundaries Diffusion Energy methods96/$ - see front matter 2008 Elsevier Ltd. A 016/j.jmps.2008.10.011 responding author at: Department of Enginee ail address: yangw@ (W. Yang).a b s t r a c t Fracture of nanocrystalline metals with extremely small grain size is simulated in this paper by structural evolution. Two-dimensional scheme is formulated to study the competition between crack growth and blunting in nanocrystalline samples with edge cracks. The scheme couples the creep deformation induced by grain boundary (GB) mechanisms and the intergranular crack growth. The effects of material properties, initial configurations and applied loads are explored. Either the enhancement in diffusion mobility, or the deterrence in the grain boundary damage, would blunt the crack and decelerate its growth, and vice versa. The simulations agree with the analytical predictions as modified from that of Yang and Yang [2008. Brittle versus ductile transition of nanocrystalline metal. Int. J. Solids Struct. 45, 3897–3907]. Upon the suppression of dislocation activities, it is validated that the brittle versus ductile transition of nanocrystals is controlled by the development of grain boundary- dominated creep versus grain boundary decohesion. Further simulations found that either decreasing the grain sizes or increasing the dispersion of grain sizes wou