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Anaël Lemaître: „Elementary mechanisms of plastic deformation in amorphous materials”
Université Paris-Est, France

Significant progress has been achieved in the last years in our understanding of the basic mechanisms of plastic deformation in amorphous materials, thanks in particular to numerical simulations of discrete systems, which have challenged many of the assumptions made in mean-field theories. Indeed, while confirming the view originally proposed by Ali Argon that plasticity is the net result of an accumulation of local shear transformations (or "zone flips"), simulations have revealed the importance of two key features of these elementary processes: flips (i) are the end result of the progressive advection of soft regions ("zones") toward their yield point, and (ii) are analogous to Eshelby transformations, i.e. emit acoustic signals which propagate anisotropic stress changes in the elastic medium. This latter feature is responsible for avalanche behavior which has now been shown to occur over a broad range of strain rates and to be very weakly dependent on temperature up to the glass tr ansition. A predictive expression for the steady flow stress in the low temperature range can thus be formulated by analyzing the interplay between thermal activation and drive, which progressively lowers the energy barriers controlling the occurrence of dissipative events.