Statistics of Bubble Rearrangements in a Slowly Sheared Two-dimensional Foam

TL;DR

This paper experimentally investigates bubble rearrangements (T1 events) in a 2D foam under shear, linking their distribution to stress and velocity profiles during elastic and plastic deformation phases.

Contribution

It provides new experimental insights into the connection between T1 event distributions and mechanical responses in sheared 2D foam, advancing understanding of plastic flow mechanisms.

Findings

T1 event distribution correlates with stress relaxation.

Velocity profiles change during elastic and plastic phases.

Plastic flow involves irreversible bubble rearrangements.

Abstract

Many physical systems exhibit plastic flow when subjected to slow steady shear. A unified picture of plastic flow is still lacking; however, there is an emerging theoretical understanding of such flows based on irreversible motions of the constituent ``particles'' of the material. Depending on the specific system, various irreversible events have been studied, such as T1 events in foam and shear transformation zones (STZ's) in amorphous solids. This paper presents an experimental study of the T1 events in a model, two-dimensional foam: bubble rafts. In particular, I report on the connection between the distribution of T1 events and the behavior of the average stress and average velocity profiles during both the initial elastic response of the bubble raft and the subsequent plastic flow at sufficiently high strains.