Modeling shear band formation in amorphous solids using a structuro-elasto-plasticity (StEP) model

Modeling shear band formation of brittle amorphous solids under load is an ongoing challenge. In this study, a newly developed structuro-elasto-plasticity (StEP) model is used to capture the essential physics for brittle response. The local disordered structure is described by a machine learning-informed property, softness, which represents the propensity of a local region to rearrange. Softness interacts with the elastic strain and plastic rearrangements. Details of these interactions are measured from two particulate systems that exhibit shear band formation during deformation: quasi-static tensile experiments of particle rafts and computational simulations of tensile deformation of polymer nanopillars. Direct microscopic measurements capture the interplay between structure, dynamics and elasticity, such as a local increase of softness after rearrangements indicating structural weakening. Such effects are then incorporated into a lattice StEP model, which qualitatively captures the shear band formation process as well as brittle-to-ductile transitions when system variables (e.g. temperature) are changed.