Transient inhomogeneous flow patterns in supercooled liquids under shear

Area of Science:

• Soft Matter Physics
• Rheology
• Materials Science

Background:

• Supercooled liquids and soft glassy systems display inherent spatial inhomogeneities in their dynamics.
• Understanding the flow behavior of these complex fluids under shear is crucial for material processing and fundamental science.

Purpose of the Study:

• To investigate the occurrence of transient inhomogeneous flow patterns (shear banding) in supercooled liquids during the start-up of steady shear flow.
• To correlate the onset of shear banding with stress overshoots in supercooled liquids.

Main Methods:

• Detailed molecular dynamics simulations were employed.
• Simulations were conducted at sufficiently low temperatures and high shear rates.

Main Results:

• Supercooled liquids exhibit transient shear banding at low temperatures and high shear rates, mirroring behavior in other soft glassy systems.
• The onset of transient shear banding aligns well with the observation of a stress overshoot.
• Slower bands accumulate higher shear stresses due to poorer adaptation to deformation.
• Shear rates in fast and slow bands adjust to maintain similar local dissipation rates.

Conclusions:

• Transient shear banding is a characteristic flow instability in supercooled liquids under startup shear.
• The interplay between shear rate, stress, and dissipation governs the dynamics of shear bands in these systems.