Statistics of slip avalanches in sheared amorphous materials based on atomistic simulation

amorphous plasticity;slip avalanches;atomistic simulation;power-law;scaling;subextensive

Zhang, Dansong ; Ostoja-Starzewski ; Martin ; Dahmen ; Karin A.

关键词: amorphous plasticity;    slip avalanches;    atomistic simulation;    power-law;    scaling;    subextensive;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/50407/Dansong_Zhang.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Many experiments have found that amorphous materials deform via slip avalanches in theplastic regime, which are bursts of plastic flows and show scale free features, as evidenced bya power-law probability distribution of the magnitude of serrations in stress-strain curves.Mesoscale models of amorphous plasticity, depending on assumptions of the interactionbetween slipped sites, give different predictions of scaling exponents. Atomistic simulation,which does not rely on such assumptions, offers an important approach to a profoundunderstanding of this phenomenon. In this study, we simulate the quasi-static simple sheardeformation of 2D amorphous samples with an atomistic approach. Tracking the evolution ofstress and potential energy with strain, we find that each avalanche event is marked by asudden drop in shear stress and potential energy. The relationship between stress drop andenergy drop becomes asymptotically linear for increasing avalanche sizes. The probabilitydistributions of stress drops follow a power law, with an exponent of 1.16 ± 0.05. Scaling ofthe distributions for different system sizes reveals that the maximum avalanche size and thenumber of events of a given avalanche size scale subextensively with system size, consistentwith previous studies. Moreover, the spatial extent of avalanches is measured. It is found thatthe occurrence of each avalanche is marked by a sudden localization of deformation. Largeavalanche events are generally more delocalized than small events, as slips are triggered inbroader regions. However, the plastic deformation is still subextensive, not extensive, evenfor the largest avalanches.