(255d) Connecting Microscopic Dynamics and Macroscopic Properties of Soft Particle Glasses

Soft particle glasses (SPG), which are suspensions composed of the deformable particles, show a solid-like behavior at rest and flow under applied stress, which exceeds the yield stress of the material. It is shown empirically that the flow curve of SPG (i.e., the relationship between shear stress and shear rate) under steady shear flow follows a Herschel-Bulkley equation (e.g., Seth et al. Nat. Mater. 10, 838 (2011)) with an exponent close to 0.5 at high shear rates. Here we utilize the three-dimensional particle-dynamics simulation to characterize the relationship between the local motion of the particles and shear stress in steady shear flow. Analysis of particles motion at short times show that the sustained elastic force, which is exerted on the particles due to frequent contacts in the particle’s cage, determines the macroscopic rheology of SPGs. The anomalous shear-dependent behavior of the diffusion coefficient also can be rationalized using the elastic force autocorrelation function obtained at different shear rates. Furthermore, a simple power balance between the shear flow energy and the dissipated energy shows that the shear stress can be related to the magnitude and the relaxation time of the elastic force autocorrelation function. Finally using experiments, this relaxation time is determined from a stress relaxation test that allows one to establish a linkage between the elastic force autocorrelation function and macroscopic rheological measurements.