Paper Number
PO31 

Session
Poster Session

Title
Shear cessation in the pre-yielding and post-yielding of dense soft solids

Presentation Date and Time
October 13, 2021 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom 1-2-3-4

Authors (Click on name to view author profile)

1. H A, Vinutha (Georgetown University, Institute for Soft Matter Synthesis and Metrology)
2. Gavin, Donley (Georgetown university, Institute for Soft Matter Synthesis and Metrology)
3. Vasisht, Vishwas V. (IIT Palakkad)
4. Del Gado, Emanuela (Georgetown University)

Author and Affiliation Lines (in printed abstract book)
Vinutha H A¹, Donley Gavin¹, Vishwas V. Vasisht² and Emanuela Del Gado^3
1Institute for Soft Matter Synthesis and Metrology, Georgetown university, Washington, DC; ²IIT Palakkad, Palakkad, Kerala, India; ³Georgetown University, Washington, DC

Speaker / Presenter 
H A, Vinutha

Keywords
computational methods; glasses; non-Newtonian fluids; rheology methods

Text of Abstract
A range of soft materials, including foams, emulsions, and microgels, exhibit a transition between solid-like and liquid-like deformation behavior as the applied deformation is increased beyond some threshold. This transition from elasticity to flow is known as yielding, and the way in which it progresses is of great practical importance in many engineering applications. Here, we simulate the steady shear startup of a non-Brownian jammed suspension, whose flow curve is described by the Herschel-Bulkley form. The transient behavior of our material shows a stress overshoot followed by a steady shear plateau. Throughout this transience, we perform an iterative series of flow cessation simulations as the strain increases to probe the progression of yielding. This is accessed through the resulting stress relaxation behavior of this suspension at each point in time. We find that the material is able to relax a greater percentage of its shear stress as it goes through yielding, indicating that the material has become more favorable to the acquisition of unrecoverable strain, as the shear cessation tests hold the total strain constant. We find the stress relaxation curve fits a stretched exponential form, and can extract a time scale (τ_σ) accordingly. The maximum value of τ_σ occurs before the system yields or stress overshoot, which may indicate the onset of shear banding. We show the differences in the material microstructure at the onset of shear banding and the steady-state using the particle displacement distributions. We also study the dependence of τ_σ on shear rate, age of the sample, and system size. Further, we compare our simulation results with that of experiments on Carbopol to identify a critical shear rate above which the main dissipation in the system is due to plastic rearrangements and/or solvent viscosity.