Yielding behavior of glasses under asymmetric cyclic deformation

Abstract

We consider the yielding behaviour of a model glass subjected to asymmetric cyclic shear deformation, wherein the applied strain varies between 0 and a maximum value γmax, and study its dependence on the degree of annealing of the glass and system size. The yielding behaviour of well annealed glasses (unlike poorly annealed glasses) display striking differences from the symmetric case, with the emergence of an intermediate strain regime with substantial plasticity but no yielding. The observed behaviour is satisfactorily captured by a recently proposed model. For larger system sizes, the intermediate strain regime narrows, leading to a remarkable reversal of yield strain with annealing.

Relaxation dynamics in amorphous alloys under asymmetric cyclic shear deformation

“…It was further shown that rescaled distributions of nonaffine displacements during one cycle followed a power-law decay when the strain amplitude is below a critical value. In agreement with the recent results for athermal glasses under asymmetric cyclic shear [56], we found that the yielding transition in more stable glasses occurs at lower strain amplitudes. In the presence of thermal fluctuations, the yielding transition can be delayed for hundreds of shear cycles in a relatively large system when periodically deformed at strain amplitudes near a critical value.…”

“…3. These results are in agreement with a recent MD study on binary glasses under asymmetric cyclic deformation using athermal quasistatic shear protocol [56].…”

“…It can be seen that the yielding transition, which is reflected in an abrupt energy change, occurs after loading is applied at 𝛾 0 = 0.100, while at 𝛾 0 ⩽ 0.096, after about 300 cycles, the potential energy remains nearly constant for 2000 cycles, indicating reversible deformation. For 𝛾 0 = 0.092 and 0.096, the energy increase during the first 300 cycles is associated with plastic deformation, similar to the results reported for athermal glasses under asymmetric shear [56]. Furthermore, loading at 𝛾 0 = 0.098 results in a stepwise increase of the potential energy during 1000 cycles and the yielding transition after 1057 cycles (see the red curve in Fig.…”

“…The glass was initially prepared by cooling across the glass transition temperature with the rate of 10 −2 𝜀∕𝑘 𝐵 𝜏 to 𝑇 𝐿𝐽 = 0.01 𝜀∕𝑘 𝐵 at 𝜌 = 1.2 𝜎 −3 . and, in particular, better annealed glasses under asymmetric shear yield at a smaller strain amplitude and exhibit an enhanced plastic activity at strain amplitudes below a critical value [56]. Despite extensive modeling efforts, however, the influence of the deformation protocol and preparation history on the yielding transition and mechanical annealing remain not fully understood.…”

Mapping out the glassy landscape of a mesoscopic elastoplastic model

“…These observations are consistent with findings in recent work by one of us on periodically sheared 3d atomistic glass formers 82 . There it was found that small samples that were moderately-or well-aged exhibit cyclic response at amplitudes well beyond the value of the strain at the stress peak.…”