A Well Defined Glass State Obtained by Oscillatory Shear

TL;DR

This study explores how oscillatory shear can produce a well-defined, reproducible glass state in colloidal materials, characterized by softening, hysteresis, and independence from residual stresses, with insights supported by a recent theoretical model.

Contribution

It demonstrates a method to obtain a reproducible glass state through oscillatory shear, clarifying the roles of shear history and hysteresis in the process.

Findings

Post-yielding glass shows significant softening.

Hysteresis occurs with increasing/decreasing strain amplitude.

Shear melting onset is described by a model based on loss of long-lived neighbors.

Abstract

We investigate the process of shear melting and re-solidification of a colloidal glass, directly after loading (pre-yielding) and after a series of consecutive strain sweeps (post-yielding). The post-yielding glass shows a significant softening compared to the pre-yielding glass, together with the absence of history effects in successive shear melting protocols, indicating a reproducible process of fluidisation and re-solidification into a glass state unaffected by residual stresses. However, a significant hysteresis characterises strain sweeps with increasing or decreasing strain amplitude. The appearance of history and hysteresis effects coincides with the formation of a glass state, whereas it is not observed in the liquid. We can describe the onset of shear melting over a broad range of volume fractions and frequencies using a recently developed model which describes the yielding process in terms of loss of long-lived nearest neighbours.