Intermittent flow in the uniaxial compression of colloidal crystals
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)Abstract
Cooperative dislocation dynamics, intermittency and power-law distributed plastic events had been repeatedly reported in recent experiments 1-3 of crystal plasticity, emphasizing the importance of stress and strain fluctuations at small scales in contrast with the ideal smooth plastic flow paradigm that prevails at large scales. At intermediate scales, cooperative dislocation dynamics effects and plastic flow can be described with the aid of dislocation dynamics simulations 3, and more coarse-grained statistical approaches4. Here we report recent results that show that similar phenomenology is observed at smaller scales. Numerical simulations of the overdamped dynamics of small colloidal crystals submitted to strain and/or load controlled uniaxial compression tests allow to monitor several important quantities such as the residual stress and the energy dissipated, or to keep track of the nucleation and dynamics of dislocations in the deformed crystal lattice. The size dependence of the strain and stress values at the onset of plasticity is also analyzed. Even for the smallest crystals considered, where only a few dislocations mediate the process, burst-like events are present in both deformation protocols and they appear to be power-law distributed. We finally discuss the analogies and differences observed between the stress and strain burst distributions, their corresponding finite size effects, and the underlying deformation mechanisms.
1) J. Weiss and D. Marsan, Science 299, 89 (2003).\\
2) D.M. Dimiduk et al., Science 312, 1188 (2003).\\
3) M.C. Miguel et al., Nature 410, 667 (2001).\\
4) M. Zaiser and P. Moretti, J. Stat. Mech. P08004 (2005)