Paper Number
MP1
Session
Metzner Presentation
Title
Recovery rheology
Presentation Date and Time
October 13, 2022 (Thursday) 8:00
Track / Room
Metzner Presentation / Sheraton 4
Authors
- Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Simon A. Rogers
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Rogers, Simon A.
Keywords
experimental methods; additive manufacturing; colloids; consumer products; foams; food rheology; gels; glasses; jammed systems; rheometry techniques; soil rheology; surfactants; suspensions
Text of Abstract
Rheological studies of real-world behaviors use idealized protocols to elucidate the underlying constitutive relations and are typically based on measurements of the stress response to strains or strain rates or vice versa. Strains and rates can therefore be thought of as rheological “atoms”, from which any complicated protocol can be built. It is commonly observed, however, that when stresses are removed, some of the deformation is recovered. Strain is therefore a composite parameter and can be decomposed into recoverable and unrecoverable components by iteratively performing constrained recovery steps during any experiment. By acknowledging strain’s composite nature, we not only get more information about how materials respond to forces that can be used to construct more accurate constitutive relations, we must also face the limitations of our current nomenclature and some of the assumptions that underly modern rheology.
Case studies are presented to highlight the benefits of forming rheological investigations around a desire to understand the recoverable and unrecoverable behaviors of soft materials. Nano-scale Kuhn segment orientation is shown to be a linear function of the bulk recoverable strain in the large-amplitude oscillatory shear response of polymer-like micelles using rheo-SANS. Knowledge of the strain components leads to accurate formation of constitutive relations for viscoelastic and yield stress fluids. A rheo-XPCS study of a thixotropic colloidal suspension highlights the central role recoverable strain can have in the formation of generalized memory functions that are applicable to any protocol. Furthermore, recovery rheology is shown to lead to conceptually clearer definitions of common parameters, as well as dimensionless groups such as the Deborah and Weissenberg numbers without the difficulty of addressing nonlinear relaxation times or experimental timescales.