Nonlinear rheology for a grease

Abstract

Large amplitude oscillatory experiments were performed using a cone-and-plate geometry with two different greases. Odd harmonics of the resultant stress waveforms are used for obtaining the material parameters. The procedure for calculating the crossover shear rate, the first and second region viscosity, and an apparent yield stress from harmonic amplitude data are each shown. This technique observes a time-dependent structural transition between the unsteady initial state and the secondary state. We found that the crossover time decreases exponentially with the imposed shear rate. Furthermore, the grease with higher filler concentration was found to yield higher yield stress.