====== Depinning models for fracture and plasticity ======

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  * Data: 04/09/09 às 16:00 
  * Local: Sl A5-01
  * Apresentador: D. Vandembroucq, Laboratoire PMMH, ESPCI - France

Resumo: The propagation of a fracture front in a heterogeneous material can be
modelled as the advance of an elastic line in a random environment.
The competition between elasticity - which tends to smooothen the
line-  and disorder - which tends to roughen it - induces a rich
phenomenology : scale invariant roughness, avalanche behavior, etc. We
will show that beyond scaling invariance, this description of crack
propagation as a dynamic phase transition gives us important
information on the effective mechanical properties at macroscopic
scale. We will also discuss the modelling of plasticity in amorphous
materials. In the absence of crystalline lattice, plastic deformation
does not result of dislocation motion but of series of very localized
reorganizations. Such reorganizations of the structure induce in turn
elastic stresses. We will propose a very simple depinning-like model
to describe this phenomenon, again characterized by a strong
competition between elasticity and disorder.


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