  The influence of variable-amplitude loading on the potential energy and
mechanical properties of amorphous materials is investigated using molecular
dynamics simulations. We study a binary mixture that is either rapidly or
slowly cooled across the glass transition temperature and then subjected to a
sequence of shear cycles with strain amplitudes above and below the yielding
strain. It was found that well annealed glasses can be rejuvenated by
small-amplitude loading if the strain amplitude is occasionally increased above
the critical value. By contrast, poorly annealed glasses are relocated to
progressively lower energy states when subyield cycles are alternated with
large-amplitude cycles that facilitate exploration of the potential energy
landscape. The analysis of nonaffine displacements revealed that in both cases,
the typical size of plastic rearrangements varies depending on the strain
amplitude and number of cycles, but remains smaller than the system size, thus
preserving structural integrity of amorphous samples.
