Showcasing RRI

Many dense particulate suspensions show a stress-induced transformation from a liquid-like state to a solid-like shear jammed (SJ) state. However, the underlying particle-scale dynamics leading to such a striking, reversible transition of the bulk remains unknown. Here, we study the transient stress relaxation behaviour of SJ states formed by a well-characterized dense suspension under a step strain perturbation. We observe a strongly non-exponential relaxation that develops a sharp discontinuous stress drop at a short time for high enough peak-stress values. High-resolution boundary imaging and normal stress measurements confirm that such stress discontinuity originates from the localized plastic events, whereas, the system spanning dilation controls the slower relaxation process. We also find an intriguing correlation between the nature of transient relaxation and the steady state shear jamming phase diagram obtained from the Wyart-Cates Model.