Mechanical rejuvenation and over-aging in the soft glassy rheology model

TL;DR

This study uses stochastic simulations of the soft glassy rheology model to explore how deformation affects aging and rejuvenation in glasses, revealing conditions under which rejuvenation or over-aging occurs.

Contribution

It introduces a detailed analysis of mechanical rejuvenation and over-aging in the SGR model, comparing results with molecular dynamics simulations for polymer glasses.

Findings

Deformation mainly causes rejuvenation in glasses.

Over-aging occurs only at low temperature, small strains, and high initial energy.

Large stresses can lead to rejuvenation even in the creep regime.

Abstract

Mechanical rejuvenation and over-aging of glasses is investigated through stochastic simulations of the soft glassy rheology (SGR) model. Strain- and stress-controlled deformation cycles for a wide range of loading conditions are analyzed and compared to molecular dynamics simulations of a model polymer glass. Results indicate that deformation causes predominantly rejuvenation, whereas over-aging occurs only at very low temperature, small strains, and for high initial energy states. Although the creep compliance in the SGR model exhibits full aging independent of applied load, large stresses in the nonlinear creep regime cause configurational changes leading to rejuvenation of the relaxation time spectrum probed after a stress cycle. During recovery, however, the rejuvenated state rapidly returns to the original aging trajectory due to collective relaxations of the internal strain.