Evaluation of Static and Dynamic Yield Stress for Isotropic and Anisotropic Particle–Based MR Fluids: Modeling and Analysis

Abstract

Structural deformation in the low shear rate region that is an undeformed state is investigated for the isotropic and anisotropic magnetic particle–based magnetorheological (MR) fluid. Flow curves were obtained for both MR fluids between 0.1 s−1 and 500 s−1 in the absence and in the presence of magnetic fields. A model to describe the flow behavior over the full shear rate study is proposed. The proposed model accounts for the friction contribution coming from particle-particle as well as particle-carrier interactions of anisotropic particles particularly in flake-shaped particles. The parameters derived from the fit have physical meaning, and it correlates with the observed dependency in rheology study. To get a better understanding of particle-particle friction contribution, magnetic nanoparticles were added in the MR fluid and flow behavior is studied. The study clearly demonstrates the contribution of particle-particle friction on the MR properties. The contribution of particle-carrier friction, due to the shape of the particle, is verified by comparing the result with spherical-shaped particle–based MR fluid.