Avalanches in 2D dislocation systems: plastic yielding is not depinning.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Dislocation avalanches, or strain bursts, are crucial in plastic deformation.
• Previous models suggested avalanche statistics align with depinning transitions in disordered systems.

Purpose of the Study:

• Investigate the statistical properties of dislocation avalanches in 2D discrete dislocation dynamics (DDD) models.
• Determine if avalanche dynamics conform to depinning transition predictions.

Main Methods:

• Utilized quasistatic stress-controlled loading in 2D discrete dislocation dynamics simulations.
• Analyzed the power-law distribution of slip and released energy from avalanches.

Main Results:

• Found avalanche statistics fundamentally differ from depinning predictions.
• Observed a power-law exponent τ=1 for slip/energy distribution.
• Identified an exponentially increasing cutoff with applied stress, diverging with system size.

Conclusions:

• 2D dislocation systems exhibit scale-free avalanche dynamics at all applied stresses.
• The observed dynamics cannot be explained by critical behavior associated with depinning transitions.