Fatigue failure of amorphous alloys under cyclic shear deformation

TL;DR

This study uses molecular dynamics simulations to explore how amorphous alloys accumulate plastic deformation and develop shear bands under cyclic shear, revealing critical strain amplitudes and fatigue lifetimes.

Contribution

It introduces a detailed analysis of fatigue failure mechanisms in amorphous alloys under cyclic shear, including a power-law description of yielding and a method to estimate fatigue lifetime.

Findings

Yielding transition follows a power-law near critical strain amplitude.

Potential energy at cycle end is nearly independent of strain amplitude.

Shear band formation involves irreversible atomic rearrangements.

Abstract

The accumulation of plastic deformation and flow localization in amorphous alloys under periodic shear are investigated using molecular dynamics simulations. We study a well-annealed binary mixture of one million atoms subjected to oscillatory shear deformation with strain amplitudes slightly above a critical value. We find that upon approaching a critical strain amplitude from above, the number of shear cycles until the yielding transition is well described by a power-law function. Remarkably, the potential energy at the end of each cycle as a function of the normalized number of cycles is nearly independent of the strain amplitude, which allows for estimation of the fatigue lifetime at a given strain amplitude. The analysis on nonaffine displacements of atoms elucidates the process of strain localization, including irreversible rearrangements of small clusters until the formation of a system-spanning shear band.