Effect of Mechanical aging on the dynamics of soft particle glasses in start-up flow*

Soft Particle Glasses (SPGs) are concentrated suspensions jammed above their close-packed volume fraction. Prior experiments show that the mechanical history of these pastes affects their rheology in start-up flow. In this study, particle dynamics simulations are used to determine the effect of the pre-shearing conditions on the dynamics of suspensions in start-up shear flow. Our results show that the SPGs with significant internal stress retain their memory with a perceptible decrease in the magnitude of their yield stress, while this behavior is less pronounced at stresses close to the dynamic yield point. Also, the microscopic dynamics of these particles are strongly influenced by the directionality of the pre-shear and the magnitude of the shear rate. Detailed analyses of mean squared displacement and intermediate scattering function of suspensions over a wide range of shear rates and volume fractions will be used to determine the microdynamics of SPGs. In summary, our results will provide a linkage between mechanical aging, in the form of the pre-shearing conditions, softness of particles, and flow strength with the macroscopic rheology of SPGs.