Stress Overshoots in Simple Yield Stress Fluids

Area of Science:

• Rheology
• Soft Matter Physics
• Materials Science

Background:

• Soft glassy materials like mayonnaise and microgels undergo shear-induced transitions.
• These transitions often manifest as a stress overshoot, a nonmonotonic stress response.
• The stress and strain at the overshoot point scale as power laws with shear rate.

Purpose of the Study:

• To rationalize the observed power-law scalings of stress overshoot in soft glassy materials.
• To develop a continuum model explaining the transient rheological response under shear startup.
• To connect macroscopic observables to microscopic nucleation and growth dynamics.

Main Methods:

• Development of a continuum model for soft glassy materials.
• Analysis of two distinct regimes: low and high applied shear rates.
• Linking model exponents to steady-state rheology and fluidized region dynamics.

Main Results:

• The continuum model successfully rationalizes the weak power-law scalings of stress overshoot.
• Two distinct regimes of behavior were predicted based on shear rate.
• Model exponents are directly related to steady-state rheology and nucleation/growth dynamics.

Conclusions:

• The study provides a consistent framework for predicting the transient response of soft glassy materials.
• The model successfully explains the stress overshoot phenomenon from fundamental principles.
• This work bridges the gap between local flow behavior and global rheological observables.