Michael Falk1 Adam Hinkle1 Sylvain Patinet3 Michael Shields1 Christopher Rycroft2
1, Johns Hopkins University, Baltimore, Maryland, United States
3, ESPCI, Paris, , France
2, Harvard University, Cambridge, Massachusetts, United States
Glasses, and the more general category of materials known as amorphous solids, lack crystal structure and find wide application from consumer goods to photovoltaics. Yet, issues quantifying disorder have stymied the construction of physically grounded mechanical constitutive laws for these materials suitable for failure prediction. Atomistic simulation methods can provide some insight regarding the mechanisms of plastic deformation, strain localization, cavitation and fracture. I will briefly discuss some applications of atomistic simulation methods to investigate each of these phenomena and the physical insights that have been gained. Recent investigations have aimed at quantifying the defects that control plastic flow. These have confirmed some of the assumptions built into the shear transformation zone theory of amorphous plasticity. I will further discuss methods for quantitatively predicting strain localization, a limiting failure process in high-strength metallic glasses and other amorphous materials by parameterizing the effective-temperature shear transformation zone theory from molecular dynamics simulations. We have directly cross-compared molecular dynamics simulations and continuum representations of these same materials in order to test and validate our constitutive theories. The role of coarse graining in the linkage of continuum and atomistic methods is crucial, and convergence only arises above a critical length scale on the order of tens of angstroms. The investigation makes clear the need to separate out the relevant fluctuations in material structure from the shorter wavelength fluctuations that serve to obscure them. It is, in the end, the interactions between these larger-scale relevant fluctuations via the material’s mechanical response that controls the failure process during strain localization.