Stress Relaxation Driven by Elementary Plastic Events in Nonaging Liquid Foams
Phys. Rev. Lett. 137, 168201 – Published 15 October, 2026
DOI: https://doi.org/10.1103/3np8-ljj1
Abstract
Liquid foams are archetypal athermal amorphous solids whose elasticity arises from the jamming of densely packed bubbles. We investigate the stress relaxation of nonaging liquid foams following flow cessation, using fast x-ray tomorheoscopy. Thanks to in situ, time-resolved measurements, we uncover robust linear affine relationships between shear stress, plastic activity, and coordination number throughout the relaxation toward a residual stress state below the yield value. In contrast to previous studies on amorphous solids, we observe an exponential relaxation governed by the duration of individual plastic events, rather than by cascades of correlated ones associated with much longer, shear-rate-dependent timescales or power-law relaxations. Our results provide new insight into the microscopic mechanisms governing the time evolution of stress in jammed amorphous solids.
