A Model for Aging under Deformation Field, Residual Stresses and Strains in Soft Glassy Materials

TL;DR

This paper introduces a comprehensive model for aging and rejuvenation in soft glassy materials, capturing complex rheological behaviors and residual stresses under deformation by linking free energy, relaxation time, and modulus variations.

Contribution

The model uniquely incorporates aging and rejuvenation dynamics with physically meaningful parameters, explaining diverse rheological phenomena in soft glassy materials.

Findings

Predicts power law dependence of relaxation time on waiting time.

Explains thixotropic behavior and shear banding.

Accounts for residual stresses and strains in soft glassy materials.

Abstract

A model is proposed that considers aging and rejuvenation in a soft glassy material as respectively a decrease and an increase in free energy. The aging term is weighted by inverse of characteristic relaxation time suggesting greater mobility of the constituents induce faster aging in a material. A dependence of relaxation time on free energy is proposed, which under quiescent conditions, leads to power law dependence of relaxation time on waiting time as observed experimentally. The model considers two cases namely, a constant modulus when aging is entropy controlled and a time dependent modulus. In the former and the latter cases the model has respectively two and three experimentally measurable parameters that are physically meaningful. Overall the model predicts how material undergoes aging and approaches rejuvenated state under application of deformation field. Particularly model proposes distinction between various kinds of rheological effects for different combinations of parameters. Interestingly, when relaxation time evolves stronger than linear, the model predicts various features observed in soft glassy materials such as thixotropic and constant yield stress, thixotropic shear banding, and presence of residual stress and strain.