Nucleation properties of isolated shear bands

Area of Science:

• Materials Science
• Solid Mechanics
• Condensed Matter Physics

Background:

• Shear banding, or strain localization, is a key plastic instability in solids.
• It significantly impacts material failure across various scales and materials.
• Understanding shear band nucleation is crucial for predicting material behavior.

Purpose of the Study:

• To experimentally investigate the nucleation kinetics and characteristic stresses of single isolated shear bands.
• To explore the relationship between shear banding and homogeneous plastic flow.
• To provide quantitative experimental support for interpreting shear band nucleation as a crystal lattice instability.

Main Methods:

• High-speed in situ imaging techniques.
• Parallel force measurements.
• Experiments conducted on three model alloys.

Main Results:

• A critical shear stress for shear band nucleation was identified.
• Nucleation stress showed minimal dependence on normal stress and was proportional to the shear modulus.
• Phase diagrams were developed, illustrating distinct domains for shear banding and homogeneous plastic flow based on strain, strain rate, and temperature.

Conclusions:

• Shear band nucleation is interpreted as a crystal lattice instability, linked to the breakdown of dislocation barriers.
• The findings offer quantitative experimental validation for this interpretation.
• The study provides insights into the transition between different plastic flow modes in solids.