Umut Salman (CNRS - CNRS – Université Sorbonne Paris Nord) - Inelastic rotations and plastic turbulence

Following the observations of intermittent plastic events and scale-free dislocation patterns in some crystals, the focus in crystal plasticity has shifted from phenomenological to micro-scale informed descriptions. The existence of temporal and spatial correlations suggested cooperative dynamics at sub-continuum scales with scaling laws interpreted as a signature of the highly coherent interaction of microscopic defects. The associated complex velocity fields  were compared to the ones  in turbulent flows. Since  turbulence in fluids  relies  on  vortices, it is natural to ask whether  large rotations are also crucial in crystal plasticity. We use a   mesoscopic  Landau-type model to show that such large rotations can be represented as micro-twinned laminates that are only disguised as  large rigid  rotations. The corresponding  deformations  are inelastic and originate from slip-induced dissipative processes at the microscale. We show that the process of the formation of such patchy textures is inherently unstable and involves quasi-turbulent motions with power law distributed spatial correlations.