Paper Number
SC22 

Session
Suspensions, Colloids and Granular Media

Title
A reinterpretation of the rheological behavior of hard-sphere colloidal glass under shear start-up

Presentation Date and Time
February 14, 2017 (Tuesday) 2:20

Track / Room
Track 1 / Audubon B

Authors (Click on name to view author profile)

1. Park, Jun Dong (University of Illinois at Urbana-Champaign, Department of Chemical & Biomolecular Engineering)
2. Rogers, Simon A. (University of Illinois, Urbana Champaign, Chemical & Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Jun Dong Park and Simon A. Rogers
Chemical & Biomolecular Engineering, University of Illinois, Urbana Champaign, Urbana, IL

Speaker / Presenter 
Park, Jun Dong

Text of Abstract
The rheology and dynamics of a hard-sphere colloidal glass under shear start-up are investigated with Brownian dynamic simulations. Under shear start-up, colloidal glasses show yielding behavior which is manifested by a stress overshoot. In this work, the stress overshoot behaviors are reinterpreted in terms of Laun’s elastic strain and an equilibrium position shift. This is a departure from the dominant rheological approach that assumes a fixed equilibrium position. Upon initiation of shearing, the elastic strain, which is the difference between the applied strain and the equilibrium position, is determined by a series of hybrid step rate (rate-controlled) and recovery (stress-controlled) tests. The elastic strain change facilitates a reasonable and quantitative explanation of the stress overshoot behavior of our colloidal glass, demonstrating a close relationship to the stress response. Additional analysis of the particle dynamics and microstructural changes is correlated to the change in elastic strain. The successful explanation of the stress overshoot of the colloidal glass suggests that Laun’s elastic strain concept has significant utility in understanding other nonlinear protocols, notably large amplitude oscillatory shear (LAOS).