Rejuvenation and shear banding in model amorphous solids

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Materials Science

Background:

• Understanding the mechanical behavior of amorphous materials, particularly glasses, is crucial for their technological applications.
• Shear banding is a common deformation mechanism in glasses, but the underlying atomic-scale processes remain under investigation.
• The relationship between local structure, plastic events, and macroscopic yielding is not fully understood.

Purpose of the Study:

• To investigate the local yield stress and its evolution during shear banding in a two-dimensional glass model.
• To elucidate the role of individual plastic events in initiating and shaping shear bands.
• To connect the yielding behavior of amorphous solids to the properties of supercooled liquids.

Main Methods:

• Simulations of a deeply quenched two-dimensional glass model subjected to athermal quasistatic deformation.
• Measurement of local yield stress at the atomic scale.
• Analysis of structural changes and softness variations following plastic events.

Main Results:

• A single plastic event is sufficient to homogenize the local yield stress distribution, erasing initial structural memory.
• Plastic events trigger the nucleation-like emergence of local softness, leading to shear band formation.
• Early-stage shear bands are softer than the steady-state flow, with yield stress comparable to supercooled liquids near T_MCT.

Conclusions:

• Plasticity in glasses leads to structural rejuvenation and a significant reduction in local yield stress.
• The observed yielding behavior explains the transition between brittle and ductile deformation in amorphous materials.
• Pressure and density changes are negligible contributors to yielding compared to softness changes from structural rejuvenation.