Origin of the Bauschinger Effect in Amorphous Solids.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Mechanics

Background:

• The Bauschinger effect describes reduced yield stress in the reverse loading direction after initial plastic deformation.
• Understanding the microscopic origins of this effect is crucial for predicting material behavior under cyclic loading.

Purpose of the Study:

• To investigate the structural origins of the Bauschinger effect in a two-dimensional model glass.
• To elucidate the role of local plastic thresholds and material polarization in driving this phenomenon.

Main Methods:

• Numerical simulations of a two-dimensional model glass under athermal quasistatic deformation.
• Computation of local residual strength (Δτ^{c}) for various loading orientations.
• Development of an elementary model for early plastic response.

Main Results:

• Plastic deformation induces material polarization, an asymmetry in local plastic thresholds.
• In steady flow, local packings favor forward instabilities, but mechanical noise leads to significant reverse yielding.
• Unloading causes reverse softening and shifts forward-yielding barriers, inverting polarization and manifesting the Bauschinger effect.

Conclusions:

• The study reveals a generic mechanism for the Bauschinger effect rooted in stress-induced polarization and reverse softening.
• This framework explains the widespread occurrence of the Bauschinger effect in various materials.