Shear band formation in amorphous materials under oscillatory shear deformation

TL;DR

This study uses molecular dynamics simulations to explore how oscillatory shear induces shear band formation in amorphous materials, revealing early indicators of yielding and the influence of annealing on deformation behavior.

Contribution

It demonstrates that shear bands can be predicted several cycles before yielding and links the collective dynamics of displacements to the material's annealing history.

Findings

Shear band formation can be detected several cycles before macroscopic yielding.

More slowly annealed glasses show delayed shear band development.

Spatial displacement analysis reveals transition from homogeneous to localized deformation.

Abstract

The effect of periodic shear on strain localization in disordered solids is investigated using molecular dynamics simulations. We consider a binary mixture of one million atoms annealed to a low temperature with different cooling rates and then subjected to oscillatory shear deformation with a strain amplitude slightly above the critical value. It is found that the yielding transition occurs during one cycle but the accumulation of irreversible displacements and initiation of the shear band proceed over larger number of cycles for more slowly annealed glasses. The spatial distribution and correlation function of nonaffine displacements reveal that their collective dynamics changes from homogeneously distributed small clusters to a system-spanning shear band. The analysis of spatially averaged profiles of nonaffine displacements indicates that the location of a shear band in periodically loaded glasses can be identified at least several cycles before yielding. These insights are important for development of novel processing methods and prediction of the fatigue lifetime of metallic glasses.