Magnetorheological Fluids Modeling: Without the No-Slip Boundary Condition

摘要

In this work, we have developed a new micro-mechanic-hydrodynamic model to predict the yield stress of magnetorheological fluids, which is also applicable without the no-slip boundary condition. We first determine the storage modulus of a MR fluid with a three-dimensional chain structure model taking into account the field concentration between the particles inside the aggregates and the effect of saturation magnetization of the particles. Then we determine the apparent viscosity of a MR fluid using the balance between the magnetic torque and hydrodynamic torque. The magnetic interaction between the particles and the wall, as well as the static coefficient of friction, are considered. Experiments are conducted to measure the magnetic properties of two MR fluids with core-shell particles. The predictions of the model are compared to preliminary experimental data obtained in a controlled stress plate-plate rheometer and other theoretical predictions. It is found that the model gives almost the correct yield stress for the MRFs in the magnetic fields lower than the saturation field, but underestimates the experimental results obtained in the magnetic fields higher than the saturation field.