Multi-Timescale Approaches to Investigate Plasticity in Amorphous Solids

Harold Park
Boston University

We couple the a recently developed approach for exploring the potential energy surface with applied mechanical deformation to examine the plasticity of amorphous solids across a range of temperatures, and strain rates ranging from atomistic to experimental. We demonstrate the power of this approach by discussing several new findings. First, we find that at room temperature and laboratory strain rates, the activation volume associated with yield is less than 10 atoms, while the yield stress is found to be as sensitive to a 1.5%Tg increase in temperature as it is to a one order of magnitude decrease in strain rate. Second, our results suggest a transition in yield mechanism for temperatures lower than about 0.54Tg that is not captured by extrapolating high strain rate molecular dynamics simulations to laboratory strain rates. Third, we demonstrate a new transition in yield mechanism from a strain driven process at very high strain rates to thermally-activated yield at experimental strain rates. Specifically, we find that the strain-driven yielding process occurs in the direction of the applied shear across both strong and weak regions of the amorphous solid as measured by the local shear modulus, whereas the thermally activated flow occurs predominately along the weak elastic regions, and not necessarily in the direction of the applied shear deformation.

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