Fatigue failure in glasses under cyclic shear deformation

Abstract

Solids subjected to repeated cycles of stress or deformation can fail after several cycles, a phenomenon termed fatigue failure. Although intensely investigated for a wide range of materials owing to its obvious practical importance, a microscopic understanding of the initiation of fatigue failure continues to be actively pursued, in particular for soft and amorphous materials. We investigate fatigue failure for glasses subjected to cyclic shear deformation through computer simulations. We show that, approaching the so-called fatigue limit, failure times display a power law divergence, at variance with commonly used functional forms, and exhibit strong dependence on the degree of annealing of the glasses. We explore several measures of damage, based on quantification of plastic rearrangements and on dissipated energy. Strikingly, the fraction of particles that undergo plastic rearrangements, and a percolation transition they undergo, are predictive of failure. We also find a robust power law relationship between accumulated damage, quantified by dissipated energy or non-affine displacements, and the failure times, which permits prediction of failure times based on behavior in the initial cycles. These observations reveal salient new microscopic features of fatigue failure and suggest approaches for developing a full microscopic picture of fatigue failure in amorphous solids.