Visualizing the strain evolution during the indentation of colloidal glasses

TL;DR

This study visualizes how strain evolves during indentation of colloidal glasses, revealing a transition from correlated to uncorrelated plastic deformation and the weak influence of structure on this process.

Contribution

It introduces a method to track individual particle motion during indentation, providing new insights into the critical behavior of strain and plasticity in colloidal glasses.

Findings

Strain distribution shifts from power-law to Gaussian during deformation.

Plastic events become uncorrelated at later stages.

Weak correlation between glass structure and strain distribution.

Abstract

We use an analogue of nanoindentation on a colloidal glass to elucidate the incipient plastic deformation of glasses. By tracking the motion of the individual particles in three dimensions, we visualize the strain field and glass structure during the emerging deformation. At the onset of flow, we observe a power-law distribution of strain indicating strongly correlated deformation, and reflecting a critical state of the glass. At later stages, the strain acquires a Gaussian distribution, indicating that plastic events become uncorrelated. Investigation of the glass structure using both static and dynamic measures shows a weak correlation between the structure and the emerging strain distribution. These results indicate that the onset of plasticity is governed by strong power-law correlations of strain, weakly biased by the heterogeneous glass structure.