•   Scientific objectives of the network 

    Size effects in condensed matter physics have both industrial and fundamental consequences. The reduction of transistor size and their implemented integration on Si wafers has already raised issues of increased metal resistance in small dimensions for instance. Fundamentally, the impact of geometrical confinement on the mechanical properties has been known for decades. Thin films are for instance stronger than their bulk counterpart, and whiskers showed size effects already in the 50' ([1,2]……). But the micropillar test that appeared in 2004 ([3,4]) revealed that this size effect, spectacular at the nanoscale, could extend far in the micron scale. What appeared as a major revolution 10 years ago as expended to an almost routine test on all kinds of systems (ceramic, biocomposites, metals, semi-conductors) but is still highly debated today. Intriguing effects such as avalanche type behavior [5], [6] are for example poorly understood. But a beneficial side effect of this new test was to renew the interest in small-scale objects and to explore an unknown region of physical metallurgy.

    Because of the broad area swept by the members of the network, and because topics, objects and methods give many reading entries to this area, we propose to keep 4 axis, as in the previous network, but to modify them slightly in order to cope with the expressed will of the participants. The goal is of course to have these four axes mixed and interacting with each other as much as possible.

    The proposed 4 axis of the next GDRi MECANO are:

    • Growth and processing of micro and nano-objects
      • Effect of stress, composition, processing route
    • Experimental methods 
      • Stress and strain mapping: TEM, X-Rays, contact,…
      • Mechanical testing: AFM, nanoindentation, micropillar, nanobeams, microtensile…
    • Modeling and simulation:
      • Mesoscale methods: Finite Element, Discrete Dislocation Dynamics,
      • Atomic scale methods : Molecular Dynamics, Ab initio
    • Mechanisms at small scale:
      • Stress relaxation, dislocation, Grain Boundary (GB) engineering, twinning, crack propagation



    [1] S.S. Brenner, Growth and Properties of “Whiskers”: Further research is needed to show why crystal filaments are many times as strong as large crystals, Science. 128 (1958) 569–575.

    [2] S.S. Brenner, Strength Of Gold Whiskers, Journal of Applied Physics. 30 (1958) 266–267.

    [3] M.D. Uchic, D.M. Dimiduk, J.N. Florando, W.D. Nix, Sample dimensions influence strength and crystal plasticity, Science. 305 (2004) 986–989.

    [4] M.D. Uchic, J.N. Florando, W.D. Nix, D. Dimiduk, Exploring specimen size effect in Ni(Al, Ta), in: Boston, 2003: pp. BB1.4.1–1.4.6.

    [5] S. Papanikolaou, D.M. Dimiduk, W. Choi, J.P. Sethna, Quasi-periodic events in crystal plasticity and the self-organized avalanche oscillator, Nature. (2012).

    [6] D.M. Dimiduk, C. Woodward, R. LeSar, M.D. Uchic, Scale-free intermittent flow in crystal plasticity, Science. 312 (2006) 1188–1190.

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