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.

Formations of force network and softening of amorphous elastic materials from a coarsen-grained particle model

“…For instance, shear-induced decreases in the effective moduli of aggregates have been reported 33 . Additionally, fractures often occur following enhancements in density fluctuations induced by shear stress 22 , 23 . Investigating the behavior of systems characterized by inhomogeneous G under shear deformation would be of interest.…”

“…This modeling technique has traditionally been employed to explain phenomenological behaviors in various systems, including polymers, liquid crystals 20 , and phase separations 21 . Recently, coarse-grained models have successfully demonstrated the fracture of amorphous materials 22 , 23 . In these models, it is assumed that density is heterogeneous, and the shear modulus strongly depends on density.…”

Fatigue failure of amorphous alloys under cyclic shear deformation

“…The prediction of stability and lifetime of amorphous alloys under repeated stress or strain deformation is important for various structural applications [1,2]. Although multicomponent alloys like metallic glasses possess a number of advantageous properties, such as high strength and large elastic strain limit, their resistance to fatigue damage is relatively poor [3][4][5][6].…”