Speaker: Péter Dusán Ispánovity (ELTE; Wigner RCP)
Title: Experimental and Theoretical Investigation of Dislocation Avalanches During Plastic Deformation
Date: Tuesday 31 March, 10:00
Place: Building 1, Conference room
Abstract:
Experimental and Theoretical Investigation of Dislocation Avalanches During Plastic Deformation The plastic deformation of crystals generally consists of a series of dislocation avalanches, which are localised and rapid deformation events. During these events, numerous dislocations move quickly and collectively. In the first part of the talk, I present the micromechanical and acoustic emission techniques we use to study these events experimentally, along with the obtained results. I will pay particular attention to our experiments on Zn micro‑pillars, in which we were the first to combine these two experimental methodologies. This allowed us to highlight the universal nature of dislocation avalanches, which show a strong resemblance to earthquakes.
In the second part of the talk, I analyse the spatial extent and distribution of dislocation avalanches using 2D and 3D discrete dislocation dynamics simulations, together with the concepts of local yield thresholds and a weakest-link approach. I conclude that short-range interactions arising from static point-like obstacles (solute atoms, precipitates, etc.) introduce a characteristic length scale that governs the spatial extent of avalanches. I provide the physical explanation of this length scale through linear stability analysis. I demonstrate how avalanches can be linked to the eigenmodes of the system’s dynamical matrix, and how localisation manifests itself in terms of these eigenmodes. Finally, I address the practically important question of how the physics of avalanche behaviour can be incorporated into a continuum theory of dislocations.
