Thermodynamic description of the stress overshoot in sheared soft particle glasses

Particle dynamics simulations are used to study the start-up flow of jammed soft particle suspensions in shear flow from a thermodynamic perspective. This thermodynamic framework is established using the concept of the two-body excess entropy extracted from the pair distribution function and elastic energy of the particles. Results show that the evolution of the elastic energy in the system closely mimics the stress-strain behavior at different shear rates. Furthermore, the transient excess entropy of the suspensions at all volume fractions shows general behavior: the excess entropy at high shear rates increases as a function of the strain, shows a mild overshoot, and attains a steady state. On the other hand, it is nearly constant at shear rates close to the dynamic yield stress. Using the transient elastic energy and excess entropy, an effective temperature is defined to establish a relationship between thermodynamics and the static yield stress data. The magnitude of this effective temperature shows a direct relationship with the peak stress and shows universal behavior for suspensions with different volume fractions.