Understanding and modeling the ductility change of a granular raft under small amplitude oscillatory deformation

Predicting the ductility of disordered solids remains challenging due in part to the poorly understood nature of their local particle rearrangements under various loading conditions. In this study, the influence of small amplitude oscillatory deformation on structure is examined with a disordered raft of polydisperse spheres floating on an air-oil interface. Upon periodic deformation below yielding, the packing structure of the raft continues to evolve. As a result, the raft shows more brittle failure in subsequent tensile and compression tests. Through particle tracking and machine learning, a local structural parameter, softness, was calculated to characterize the ability of a select particle to rearrange. We use an analysis of softness to inform a Structuro-Elastoplastic (StEP) model to predict the lower ductility of systems that underwent the oscillatory small amplitude deformation.