Dilution dependent magnetorheological effect of flake-shaped particle suspensions—destructive friction effects

The increase in viscosity as well as yield stress induced by an applied magnetic field were measured in dependence on the particle volume fraction of a magnetorheological fluid with flake-shaped particles. Five suspensions were synthesized, with particle volume concentrations varying from 7.45 vol.% to 17.74 vol.%. A drastic change in the behaviour of the relative viscosities was observed, which was related to a critical volume fraction. The yield stress showed similar characteristics and its origins were studied in more detail using a special analysis method which allows one to distinguish between the magnetic and friction components of yield stress. The hypothesis of 'destructive friction' is presented, which describes damped structure formation due to the dissipation of energy through multibody interactions. (paper)