Influence of Friction on Magnetorheological Effect

The magnetorheological effect (MR effect) used to be believed to be dominated by magnetic dipole interactions among carbonyl iron particles. In this chapter, friction as an important factor is introduced in the MR effect. The shear history effect of MR fluids was ascribed to not yet relaxed pre-formed chain/column structure. At certain conditions, the stick-slip effect in MR fluids could be found, which is similar to the general observation in general sliding friction. The influence on rheology of MR fluids from the lubrication performances of the carrier fluid was fully demonstrated. A better lubrication of base oil usually led to a decreased shear strength of the MR fluid under the same field strength. The ‘cross point’ of the damping factor (tan δ) of the MRF was found, which suggested two kinds of friction influencing MR effects. The shear thickening of the MR fluid and its tribological mechanism was also introduced. All these results clearly indicated that friction played important roles in the magnetorheology by affecting the force transmission at the particle–particle interface and particle–electrode interface.