Universal features of amorphous plasticity
This work is a continuation of this other one. Here, we leverage the possibilities offered by the Finite Element Method to simulate systems under diverse and more realistic conditions. Specifically, we study different non-trivial loading conditions such as simple shear, bending, or indentation. These loading conditions are of higher relevance in real-world situations than those typically simulated by stochastic models.
From the data produced by the model, my collaborators and I estimated the probability distributions for different material properties and computed spatial maps of plastic activity. The results showed that loading conditions substantially impact spatial activity, leading to strikingly different patterns. Despite these differences, the results also evidenced that many other statistical properties are independent of loading conditions and model variations. Therefore, we identified universal characteristics intrinsic to plastic deformation that always hold across different physical scenarios.
These videos show a sample deforming in bending (left) and under an indentor (right). The red color represents deformation:
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Article Abstract
Plastic yielding of amorphous solids occurs by power-law distributed deformation avalanches whose universality is still debated. Experiments and molecular dynamics simulations are hampered by limited statistical samples, and although existing stochastic models give precise exponents, they require strong assumptions about fixed deformation directions, at odds with the statistical isotropy of amorphous materials. Here, we introduce a fully tensorial, stochastic mesoscale model for amorphous plasticity that links the statistical physics of plastic yielding to engineering mechanics. It captures the complex shear patterning observed for a wide variety of deformation modes, as well as the avalanche dynamics of plastic flow. Avalanches are described by universal size exponents and scaling functions, avalanche shapes, and local stability distributions, independent of system dimensionality, boundary and loading conditions, and stress state. Our predictions consistently differ from those of mean-field depinning models, providing evidence that plastic yielding is a distinct type of critical phenomenon.
Z. Budrikis, D. F. Castellanos, S. Sandfeld, M. Zaiser & S. Zapperi