Fatigue fracture mechanism of amorphous materials from a density-based coarse-grained model

Abstract

Fatigue fracture is a unique failure mode of materials induced by repeated loading and is crucial for the long-term stability of materials used in cars and aeroplanes. Fatigue is the progressive and localised structural damage of a material subjected to cyclic loading. The minimum strain amplitude that causes such damage is much less than the material’s yield strain under simple loading. This observation leads to a widespread belief that the threshold strain amplitude for fatigue fracture is much smaller than that for monotonic fracture under continuous loading. Here, we study the physical mechanism of the low-cycle fatigue fracture of amorphous solids by considering the complex coupling between density, deformation (velocity), and stress. Contrary to the common belief, we find that the critical strain amplitude, i.e., the onset of irreversible deformation, is the same for fatigue and monotonic fractures. Experimental verification of this prediction is desirable.