Plastic strain is a mixture of avalanches and quasi-reversible deformations: Study of various sizes

TL;DR

This study uses discrete dislocation simulations to analyze size-dependent plastic deformation, revealing nearly reversible regions, power-law behavior, and size effects consistent with experiments, but not reaching a thermodynamical limit at large strains.

Contribution

It demonstrates the coexistence of avalanches and quasi-reversible deformations in size-dependent plastic flow through detailed simulation analysis.

Findings

Nearly linear and reversible regions between avalanches.

Power-law stress-strain behavior over two decades.

Size effects consistent with experimental observations.

Abstract

Size-dependence of plastic flow is studied by discrete dislocation dynamical simulation of systems with various numbers of interacting linear edge dislocations while the stress is slowly increased. Regions between avalanches in the individual stress curves as functions of the plastic strain were found nearly linear and reversible, where the plastic deformation obeys an effective equation of motion with a nearly linear force. For small plastic deformation, the means of the stress-strain curves are power law over two decades. Here and for somewhat larger plastic deformations, the mean stress-strain curves converge for larger sizes, while their variances shrink, both indicating the existence of a thermodynamical limit. The converging averages decrease with increasing size, in accordance with size-effects from experiments. For large plastic deformations, where steady flow sets in, thermodynamical limit was not realized in this model system.