Dual-stress origin of local stress minima in dense granular suspensions

Dense granular suspensions exhibit a local minimum in the stress–shear rate curve during the transition from quasi-static to viscous flow, a robust yet unexplained feature of dense-flow rheology. Using a dual-stress constitutive framework that couples rate-independent (hypoplastic) and rate-dependent (viscous–inertial) stresses, we capture this behavior and clarify its physical origin. The minimum results from a dynamic shift in stress dominance from contact network support to viscous resistance, revealing a dual-stress mechanism that governs regime transitions in dense granular suspensions.